POLYMERIC ALLOYS FROM POLYESTER RESINS AND PROCESS FOR THEIR PREPARATION

Abstract: Process for the preparation of polymeric alloys from polyester resins and polymers containing groups capable of giving addition reaction with functional compounds containing at least two reactive groups comprising the melt state mixture stage of polyester resin, reactive polymer and functional compound of mixture pelletizing and following polyaddition reaction in the solid state at temperatures between 150 DEG and 220 DEG C to obtain an increase of the polymer intrinsic viscosity of 0.1 dl/g in comparison with the starting polyester resin.

Description: Polymeric alloys from polyester resins and process for their preparation The present invention relates to an improved process for the preparation of polymeric alloys from polyester resins and polymers containing reactive end groups. The polymeric alloys from polyester resins and from resins such as polycarbonate, polyamides were so far obtained by blending in the molten state optionally operating in the presence of functional compounds able to react with the re¬ sin end groups. The properties of these alloys are not satisfactory due to side reactions such as transesterification, transamidation and degradation, which occur in the molten state. Due to the degradation reactions, it was not possible moreover to pre¬ pare resins with molecular weight high enough to enable good mechanical properties of the polymeric alloys. A method has now been found which allows to prepare polyme¬ ric alloys with unexpectly high mechanical properties by reacting resins mixtures at the solid state in the presence of a polyfunctional compound containing at least two groups capable of reacting with addition reactions with the resins end groups. The polyester resin, the resin containing reactive groups and the functional compound are blended in the molten state; the mixture is then pelletieed and the chips are then su¬ bjected to the solid state polyaddition reaction. The polyaddition reaction in the solid state is generally preceded by a crystallization step carried out after the melt state mixture stage and after the following pelleti- zing. The crystallization step is carried out to prevent ag¬ glomeration phenomena of chips and/or of sticking on the reactor wall during the reaction in the solid state. The crystallization step is carried out at temperatures hi¬ gher than the TG of the polyester and comprised in general between 130° and lβo'C. The process of alloys preparation is preferably carried out in continuous way using continuous crystallizers and polyad¬ dition reactors where the chips are fed counter currently to a stream of a heated gas, e.g. air, nitrogen and other inert gas, such as carbon dioxide. The polyaddition reaction in the solid state is carried out at temperatures higher than 150*C and lower than the melting point of the polyester re¬ sins. The temperatures are in general comprised between 180° and 210*C. The residence time depends on the increase of the required intrinsic viscosity and of the mechanical proper¬ ties. The viscosity increase is at least 0.1 dl/g in compa¬ rison with the starting polyester resin. The treatment is carried out in an inert gas stream in a fluid bed or fluidi- zed reactor. The polyfunctional compound is preferably selected from the group consisting of pyromellitic acid dianhydride, 3,3' 4,4' biphenyltetracarboxylic acid, bis (3,4-dicarboxyphenyl) et¬ her, bis (3,4 dicarboxyphenyl) thiother, 3,4 dicar oxylic acid, bisphenol A, 2,2 - bis (3,4 dicarboxyphenyl) hexafluoropro- pane, 2,3,6,7 naphtalenetetracarboxylic acid, bis (3,4 di¬ carboxyphenyl) sulfone, 1,2,5,6 - naphtalenetetracarboxylic acid, 3,2' 3,3" - biphenyltetraσarboxylic acid, bis (3,4 dicarboxyphenyl) sulfoxide, 3,4,9,10 - perylene tetracarbo- xylic acid and mixtures thereof. The aromatic dianydrideβ most preferred are the pyromellitic dianydride and 3,3' 4,4' benzophenonetetracarboxylic acid dianydride and mixtures thereof. Besides the dianydrides of the above mentioned tetracarboxy- lic aromatic acids can be also used the dianydrides of ali¬ phatic, cycloaliphatic and tetrahydrofurantetracarboxylic acids. Representative compounds are 1,2,3,4 cyclobutanetetracarbo- xylic acid and tetrahydrofuran 2,3,4,5 - tetracarboxylic acid. The blending of the polyester resin with the resins contai¬ ning reactive end groups and with polyfunctional compound is preferably carried out in corotating or counter rotating, intermeshing or not intermeshing twin screw extruders with or without degassing equipment, at a temperature between 200° and 350"C depending on the melting point of the mixture of the polymers. A counter rotating and not intermeshing screws extruder is preferred. The use of such a type of extruder allows to perform a good distribution of the polyfunctional compound in the melt and to avoid problems of local high concentrations of the addi¬ tive due to its high reactivity. This type of extruder allows very short residence times. The extruder is preferably connected with a high vacuum oil seal pump to maintain a vacuum higher than 2 tor to carry out the dosing of the reactive mixture and to obtain a resin with a low content of acethaldehyde. The preferred concentration of additive with respect to the polyester resin is 0.05-1% by weight. The residence time in the extruder can be comprised between 10 and 120 sec. preferably 15-30 sec. To avoid random local concentrations of additive in the melt it is advisable to dilute the additive with crystallized PET powder (1 part of additive to 3 parts of PET powder) . This procedure ensures a homogeneous distribution of additi¬ ve leading to a better reproducibility of the end product intrinsic viscosity and Inhibiting gel formation. The additive may also be diluted using crystallized PET chips (1 part additive to 10 parts of PET chips) . The blending could be performed in a fanned blender using 0,1% by weight of adhesive agent. The polyester resins usable in the invention process are the product of polycondenεation of glycole with 2-10 carbon atoms, such as ethylene glycol, 1,4-butileneglycol, 1,4 cy- clohexylenglycol, with terephthalic acid or derivatives the¬ reof such as dimethylterephthalate, as well as the polycon¬ densation products containing besides units deriving from terephthalic acid, also units deriving from other bicarboxy- lic acids such as naphthalendicarboxylic acids / isophtalic acid, orthophtalic acid and 5-tert-butyl-l,3-benzene- dicarboxylic acid in a quantity of about 0.5-25% mole of all acid units. Among the polyester resins the elastomeric polyester resins are also included and in general are included block polye¬ ster copolymers containing blocks deriving from the polycon- densation of a glycol with an aromatic bicarboxylic acid. The starting polyester resin has an intrinsic viscosity lo¬ wer than 0.8 dl/g and generally between 0.6 and 0.75 dl/g. The preferred resins are polyethylenterephthaiate and copo- lyethylenterephthalates containing up to 20% of unit deri¬ ving from isophtalic acid. The reactive resins different from the polyester resins have end groups preferably selec¬ ted among OH, KH 2 , SH. The polyamides are the preferred resins. These resins are characterized by the repeating unit - NH CO -; the ponderal molecular weights are generally included between 10,000 and 50,000. Examples of these resins are Nylon 4, Nylon 6,6, Nylon 6, Nylon 8, Nylon 11, Nylon 12. Other examples of usable resins are polycarbonate, polyphe- nylenoxide and polysulphide resins. The reactive resins are used in a quantity of about 1-50% preferably 5-20% by weight: on the weight of the mixture. The alloys obtained using polyamides are characterized by a very high elastic module fithout sacrificing the tensile strength and elongation at break.Films obtained from alloys prepared starting from polyamides, present values of the elastic modulus varing between 4.2 and 5 GPa following the stretch ratio in the range between 3-5, while the reference polyester shows values in the range between 3.3 and 2.2 GPa and the alloys obtained without using the polyfunctional compound (piromellitic dianydride) have values of the modu¬ lus in the range between 2.4-2.9 GPa. The following examples are given to illustrate but not to limit the invention. EXAMPLE 1 10 Kg/h of a mixture at 95% by weight of crystalline PET (IV=0.601 dl/g) and at 5% by weight of 6,6 Nylon (the mixtu¬ re is dried vacuum at 140*C for lOh) were fed together at 0.05% by weight of pyromellitic dianhydridβ (PMDA) to a counter rotating and not intsmashing twin screw extruder. The mixture was extruded and also pelletized. The chip in¬ trinsic viscosity was 0.694 dl/g; the COOH groups content =52.2 eq/ton. The extrusion conditions were as follows: Ratio lengt /diameter (L/D) = 36 Screw speed = 150 rpm Cylinder temperature = 260*C Chips feed speed <* 10 Kg/h PMDA feed speed = 0.05 Kg/h mould type = circular with 3 mm dia. The so obtained chips were subjected to upgrading at 186 β C for 6 hours in nitrogen stream. The intrinsic viscosity after the treatment was of 0,927 dl/g and the COOH groups as 49 eq/ton. The obtained polymer was then extruded continuously (before drying) in a monoscrew extruder for film. The film was col¬ lected on chilled rollers and then on rollers heated at B5°C and then on collecting cylinder. The stretch ratio used was of 3:1 in a test, of 4:1 in a second test and of 5:1 in a third one. The films mechanical properties are shown in table 1. Comparative example l A mixture at 95% by weight of crystalline PET (IV«0,601 dl/g) and at 5% of 6,6 Nylon (dried vacuum at 140 β C for lOh) was extruded and pelletized in the conditions as in example 1. The chips were then subjected to upgrading under the same conditions as in example 1. The obtained polymer intrinsic viscosity was of 0,786 dl/g and the groups concentration COOH of 21.4 eq/ton. The chips were also extruded in the extruder for films of example l in the same conditions there indicated. The obtai¬ ned film was collected with stretch ratio of 3:1, 4:1 and 5:1 in the different tests. The film properties are shown in table l Comparative example 2 PET with IV-0.83 dl/g was filmed under the conditions of example 1 using the same stretch ratios. The film properties are shown in table 1. Table 1 The tensile strength was determined according to ASTMD-882 using a INSTRON tensile tester (Mod. 4505) on samples at 25"C and with 50% of relative humidity. The elastic modulus was determined from the slope at the stress-strain curve. The intrinsic viscosity was determined in a solution of 0,5 g of polymer in 100 ml, of a solution at 60/40 by weight of phenol and tetraclorethane, operating at 25*C according to ASTM D-4603-86.

Claims: CLAIMS Polymeric alloys from polyester resins and reactive po¬ lymers containing end groups capable of addition reac¬ tions with compounds containing at least two reactive groups obtained by reaction in the solid state of mix¬ tures of the above resins, polymers and functional compounds. Process for the production of polymeric alloys starting from polyester resins and reactive polymers containing end groups capable of addition reactions with functio¬ nal compounds containing at least two reactive groups according to claim 1, comprising following operations: a) blending in the molten state the polyester resin, the reactive polymer and the functional compound b) pelletizing the molten mixture c) polyaddition treatment in the solid state at tem¬ peratures between 150"-220"C for a time sufficient to obtain an increase of at least 0.1 dl/g of the intrinsic viscosity of the polymeric alloy refer¬ red to the intrinsic viscosity value of the star¬ ting polyester resin. Process according to claim 2, where the reactive poly¬ mer contains end groups selected among OH, NH 2 and SH. Process according to claim 2 where the reactive polymer is a polyamide. 5. Process according to claim 4, where the polyamide is chosen among Nylon 4, Nylon 6, Nylon 6,6, Nylon 8, Ny¬ lon 11 and Nylon 12. 6. Process according to claims from 1 to 5, where the quantity of reactive polymer is comprised between 1 and 50% by weight on the mixture. 7. Process according to claim 4 where in the polyamide quantity is comprised between 5 and 20% by weight. 8. Polymeric alloys obtained according to a process of claims 2-7. 9. Manufactured articles obtainable from polymeric alloys of claim 8.

Inventors: AL GHATTA HUSSAIN ALI KASHIF, AL GHATTA, HUSSAIN, ALI, KASHIF
Applicants: AL GHATTA HUSSAIN ALI KASHIF, M & G RICERCHE SPA, M. & G. RICERCHE S.P.A.
Application year: 1993
Main classification: C08L67
IPC codes: C08L67, C08L69, C08L71, C08L77, C08L81