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
  • C08G63/78—Preparation processes
  • C08G63/80—Solid-state polycondensation

Definitions

• the present invention relates to a polyester type polymer, a manufacturing process and its use for the manufacture of articles.
• It relates more particularly to a polyester of high molecular weight and viscosity in the molten state allowing use of this polymer in the processes for manufacturing articles by extrusion and pultrusion, for example or more generally the shaping processes require a polymer having a high melt viscosity to avoid or limit deformation of the shaped article before solidification of the material.
• Polyesters that is to say the polymers obtained by reaction between two monomers leading to ester functions are among the most used polymers.
• polyethylene terephthalate is the most common and is the raw material for the manufacture of numerous articles such as films, threads, articles obtained by injection molding and / or blow molding.
• polyesters are more and more used because they combine interesting physical, physicochemical properties, high processability and are also entirely recyclable either by remelting or by depolymerization into starting monomers.
• these methods consist of a first step of esterification or transesterification by reaction of a diol with a diacid or a diester, followed by a second step of polymerization or polycondensation with elimination of alcohol.
• the accessible degree of polymerization of the polymer is limited by the parasitic and concurrent degradation or depolymerization reactions occurring when the temperature is above 260 ° C.
• the manufacture of polymer with a high degree of polymerization therefore with a high melt viscosity, is impossible because the stirring of the reactor becomes impossible as well as the casting of the polymer.
• it is proposed to carry out a post-condensation in the solid phase consisting in maintaining the polymer in the solid state at a temperature between 200 ° C. and 240 ° C. and entraining the alcohol. formed by a advantageously non-oxidizing gaseous fluid or carrying out the polycondensation under reduced pressure.
• the degree of polymerization can be raised up to a certain limit corresponding to viscosity indices of the order of 1.4 dl / g, (absolute molecular weight by mass of the order of 80,000). .
• the polymers thus obtained have a viscosity in the molten state which is still too low to allow their use in shaping processes such as extrusion or pultrusion of articles with thick walls which do not allow the material to harden. immediately after leaving the die and therefore requiring the use of a self-supporting material which does not flow or very weakly in the molten state.
• One of the aims of the present invention is to remedy these drawbacks by providing a polyester free from chain extender and having a sufficiently high degree of polymerization to obtain a level of viscosity in the molten state compatible with the shaping processes. articles, especially articles with thick walls.
• the invention provides a polymer comprising repeating units of general formula I
• R 1 is an aromatic group which can comprise several nuclei in condensed form, and which can be substituted.
• R 2 is a linear or branched aliphatic hydrocarbon group comprising from 2 to 6 carbon atoms.
• the polymer has an absolute average molecular weight by mass Mw greater than 130,000, preferably greater than 135,000.
• the polymer has an absolute average molecular weight in number Mn greater than 45,000, preferably greater than 50,000.
• the absolute average molecular weights by mass and number Mw and Mn for the polyesters in accordance with the invention are determined according to the method described below.
• This method uses GPC (gel permeation chromatography) or SEC (size exclusion chromatography) techniques. It corresponds to that described by Klaus Weisskopf (Journal of Polymer Science: part A, vol 26, 1919-1935; 1988).
• the method used differs in the composition of the vector mixture.
• the mixture used consists of 95% by volume of CH 2 CI 2 and 5% by volume of HFIP (hexafluoroisopropanol) to which 0.005 mole of BF 4 NBu 4 is added to eliminate any artifacts observed with certain polyesters.
• HFIP hexafluoroisopropanol
• polyesters are dissolved in a mixture 75% by volume CH 2 CI 2 and 25% by volume of HFIP containing 0.005 mole of BF 4 NBu 4 .
• the GPC is calibrated with polystyrene (PST) as the standard compound.
• PST polystyrene
• the average molecular weights Mn, Mw, Mz and the polymolecularity index Ip are determined in PST equivalent.
• the elution concentration is established by UV at 270 nm for injections of 40 ⁇ i at 2 mg - 3 mg / ml.
• the experimental conditions of the analysis method are as follows:
• RI ERMA refractometer sensitivity 16 -UV: UV2000 TSP dual wavelength (270nm and 290nm)
• the group R 1 is chosen from the group comprising the divalent phenyl, naphthyl and sulfophenyl groups.
• the phenyl group is the preferred group and corresponds to the terephthalic and / or isophthalic acid monomers or their esters.
• the group R 2 it is advantageously chosen from the group comprising the divalent ethyl, propyl and butyl groups.
• the ethyl group corresponding to the ethylene glycol monomer is the preferred group.
• 130,000 has a melt viscosity greater than 8040 Pa.s.
• a polymer of high degree of polymerization is capable of being obtained by a manufacturing process defined by the following steps: i) - Preparation of a prepolymer from the monomers corresponding to the production of a repeating unit according to general formula I, said prepolymer advantageously having a degree of polymerization at least equal to 10, preferably included between 10 and 80. ii) - Formation of particles of said prepolymer, having a surface area / mass ratio of polymer greater than 20 cm 2 / g, advantageously greater than or equal to 50 cm 2 / g, preferably greater than or equal to 80 cm 2 / g.
• the solid phase polycondensation is advantageously carried out by setting the particles in motion relative to one another by means of agitation, and heating the particles. at a temperature, advantageously the highest possible but lower than the temperature causing the polymer to melt on the surface of the particles.
• the bed of particles is swept or traversed by a fluid, preferably a non-oxidizing gaseous fluid such as nitrogen. To promote this elimination, it is also possible to carry out this polycondensation in the solid phase under reduced pressure.
• the flow of gaseous fluid can cause the particles to move.
• the solid phase condensation can be carried out in a fluidized bed.
• the risks of sticking are minimal allowing the use of a fixed bed of particles in this phase of polycondensation in the solid state.
• the condensation temperature in solid phase is advantageously less than or equal to 270 ° C, preferably between 220 ° C and 270 ° C.
• step i) of preparation of the prepolymer can be carried out by all known methods and in particular in the first steps of the usual method of manufacturing conventional polyesters.
• These methods generally include:
• the first route of production is the so-called "methyl terephthalate” (DMT) route. It is a transesterification reaction.
• the molten DMT is added to the excess ethylene glycol (EG), the EG / DMT molar ratio being approximately 1.9 to 2.2, and the reaction is carried out at atmospheric pressure and at temperatures of approximately 130 ° C. 250 ° C. It requires the presence of a catalyst, for example, manganese acetate.
• the methanol released by the reaction is removed by distillation.
• the excess ethylene glycol is removed after the transesterification reaction.
• the catalyst which is also a catalyst for the degradation of the polyester is blocked with phosphorous compounds after the reaction.
• the product resulting from the transesterification is a mixture of bis-hydroxyethyl terephthalate (BHET) and oligomers.
• BHET bis-hydroxyethyl terephthalate
• the second route is the so-called "direct esterification" route. It is an esterification reaction of terephthalic acid with ethylene glycol. It is carried out at temperatures from 130 ° C to 280 ° C. Ethylene glycol is present with an EG / Terephthalic Acid molar ratio of approximately 1 to 1.4. The result of this reaction is a mixture of oligomers having terminal acid and hydroxyethyl functions.
• the use of these methods is the subject of numerous studies described in the literature. The conditions indicated above do not constitute a limitation on the scope of the present invention.
• the subsequent prepolymerization step is a polycondensation polymerization step. It is generally catalyzed using metallic compounds, for example by compounds of antimony, titanium or germanium. It can be catalyzed by any polycondensation catalyst described in the prior art.
• This liquid phase prepolymerization step can preferably be carried out according to two embodiments.
• the first embodiment consists in carrying out the prepolymerization in the molten phase.
• the second embodiment consists in carrying out the prepolymerization in the molten phase dispersed in a liquid medium.
• the prepolymer obtained is advantageously of average degree of polymerization between 10 and 80, preferably between 20 and 80.
• average degree of polymerization is meant the absolute average degree of polymerization defined by the following formula (IV):
• M 0 is the molar mass of the repeating unit of the polymer
• Mj is the molar mass of the chain of size referenced i
• nj is the number of chains of size referenced i.
• the molar masses are the absolute molar masses.
• the average degree of polymerization is related to the absolute molar mass in number M n absolute, according to the above formula. The latter is evaluated by
• viscosity index (IV) is understood to mean, without indication to the contrary, the viscosity in ml / g measured at 25 ° C. using a Ubbelohde type viscometer for a 0.005 g / ml solution. of polymer dissolved at 115 ° C. in a mixture composed of 50% by weight of phenol and 50% by weight of 1-2 dichlorobenzene.
• the prepolymer thus obtained is ,. according to the invention, put in the form of particles of controlled dimensions to allow diffusion of the alcohol formed by the condensation reaction, without physical limitation.
• the particles formed have, according to the invention, a surface / mass ratio at least equal to 20 cm 2 / g, preferably greater than or equal to 50 cm 2 / g, advantageously greater than or equal to 80 cm 2 / g.
• the shape of the particles is not critical and depends on the technique used for the preparation thereof. Thus, for the techniques leading to an almost spherical shape of particles, the average size of these particles should be less than 1 mm, preferably less than 0.8 mm, advantageously between 50 ⁇ m and 0.5 mm.
• particle size it should be understood that all the particles suitable for the process of the invention must pass at least through a sieve whose orifices have a diameter of 1 mm, preferably less than 0.8 mm, advantageously less than 0.5 mm.
• the prepolymer can also be formed into particles by grinding or flaking techniques, for example. With these techniques, the particles obtained can have a high form factor (ratio between the smallest dimension and the largest dimension of a particle). To allow diffusion of the diol and of the water formed without physical limitation, it is advantageous for the smallest dimension of these particles to be less than 700 ⁇ m, preferably less than or equal to 200 ⁇ m. The form factor of the particles is advantageously greater than 10.
• This liquid must not be a solvent for the alcohol formed or a plasticizer or swelling agent for the polymer.
• the prepolymer can be dispersed in the molten state in the liquid medium, solidification being obtained by cooling.
• the liquid suspension of the particles of esterification or transesterification product is maintained at temperature to cause polycondensation and to obtain a degree of polymerization of the prepolymer particles equivalent to that of the prepolymer obtained by the polycondensation route in the molten state.
• the particles are then solidified by cooling.
• the particles thus obtained are at least partially crystallized.
• this crystallization can be obtained by cooling and maintaining the particles at a temperature greater than or equal to 100 ° C., advantageously between 130 ° C. and 210 ° C. It intervenes mainly in the surface layer of the particle, thus making it possible to avoid the problems of sticking during the stage of condensation in solid phase.
• the last step of the process is the realization of polycondensation in solid phase of the polymer in the form of particles.
• This solid phase polycondensation in the process of the invention, exhibits rapid kinetics and can be continued at high degrees of polymerization because of the particle size which removes the physical limits to the diffusion of the diol and of the volatile compounds formed. during the polycondensation reaction in the material, and to the characteristics of the starting prepolymer, in particular its degree of polymerization.
• Solid phase polycondensation is carried out in a device similar to that used to carry out solid phase post-condensation in conventional polyester manufacturing processes.
• it is advantageously carried out by setting the particles in motion with a non-oxidizing gaseous fluid, thereby forming a fluidized bed.
• non-oxidizing gases are preferred.
• nitrogen, rare gases, inert gases, CO 2 are the preferred fluids, nitrogen being the preferred gas.
• the particles are heated by any suitable means, in particular by supplying the hot gaseous fluid, to a temperature allowing advancement of the polycondensation, advantageously with kinetics acceptable for industrial exploitation.
• This temperature must be lower than the temperature at which a melting or an onset of melting of the polymer particles would occur, in particular on the surface thereof. This condition is necessary to avoid sticking of the particles together.
• this temperature increases with the advancement of the polycondensation reaction. This increase in temperature can be continuous or be carried out in successive stages.
• the temperature at the start of solid phase polycondensation is advantageously greater than 220 ° C. and rises to values close to or equal to 270 ° C. at the end of polycondensation.
• the duration of this polycondensation step is variable and depends on the degree of polymerization desired. It can vary from a few tens of minutes to a few tens of hours. Other process variants are possible for carrying out this polycondensation step in the solid phase.
• the particles can be set in motion by mechanical means such as ultrasonic agitation, mechanical agitation.
• the gaseous fluid can also sweep the surface of the particle bed. It is also possible to carry out this polycondensation in the solid phase by using a liquid as a fluid. This embodiment is used in particular when the preparation of the prepolymer is carried out by the polycondensation process in dispersion in a liquid.
• the polymer particles obtained at the outlet of the solid phase polycondensation step can be used as a raw material for the production of articles in processes for shaping these articles.
• the polymer in the molten state has a high viscosity allowing its use in the shaping processes by extrusion, pultrusion of articles in particular with walls thick, that is to say articles of shapes and dimensions preventing any immediate cooling at the outlet of the die.
• the material used does not immediately flow out of the die to avoid any deformation before solidification thereof.
• the polymer with a high degree of polymerization can be used alone or in combination with additives usually used to improve or modify certain properties of the polymers such as thermal stability, resistance to UN radiation. or to light, fireproofing properties, resistance to oxidation. It is also possible to use the polymer with pigments and / or dyes as well as fillers or reinforcing fillers.
• filling fillers of mineral powders such as clays, talc, silica, alumina and as reinforcing fillers for glass fibers, carbon fibers, ceramic fibers or thermosetting plastic fibers.
• a poly (ethylene terephthalate) prepolymer with an initial viscosity index (IV) of 42 ml / g corresponding to an average degree of polymerization of 43 is prepared according to a conventional process of direct esterification and polycondensation in the melt phase, starting from 'purified terephthalic acid and ethylene glycol, in the presence of 250 ppm of catalyst based on antimony oxide (expressed by mass of Sb).
• This prepolymer contains 52 ⁇ eq of acid terminations per gram of prepolymer.
• the prepolymer is solidified en masse and then ground in the presence of dry ice.
• the grinding product is sieved to select the particles passing through a 400 ⁇ m mesh sieve.
• the sieved powder is dried for 3 hours at 130 ° C under vacuum.
• the polymer thus obtained has a degree of crystallization of approximately 50%.
• This powder is fed into a 250 ml flask placed on a rotary evaporator rotated at a speed of 30 revolutions per minute. Heating of the powder is obtained by an oil bath in which the flask is immersed.
• a flow of nitrogen with a standardized flow rate of 25 to 30 l / h is fed into the tank.
• the powder is brought to a temperature of 250 ° C., samples are taken at different treatment times to determine the progress of the polymerization.
• the viscosity index IV expressed in dl / g has been determined by solubilization at room temperature (between 15 and 25 ° C) of the polymer in a solvent comprising 75% by volume of CH 2 CI 2 and 25% by volume of HFIP. The solvent is then evaporated to obtain a film which will be dissolved at a temperature of 110 ° C in a mixture of phenol / dichlorobenzene solvents (50/50). The viscosity index is measured from a solution comprising 0.5% by weight of polymer, according to the method indicated above. The viscosity in the molten state was calculated using the correlation formula ( III) indicated above.
• Ip represents the polymolecularity index of the polymer. The results obtained are shown in Table 1 below.
• Example 1 is repeated but carrying out the polycondensation in solid phase at a temperature of 240 ° C instead of 250 ° C and for 25 hours.
• the polymer obtained has the following properties:
• Example 2 is repeated, but using as a prepolymer, a polyester with a degree of polymerization equal to 73 and 64 ⁇ eq of acid terminations per gram of prepolymer.
• the polymer obtained after polycondensation in solid phase has the following properties:
• Example 1 is repeated but using a prepolymer with a degree of polymerization equal to 43 in the form of particles obtained by grinding and not passing not through a mesh screen equal to 1 mm, but passing through a mesh screen equal to 2 mm.

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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)
• Extrusion Moulding Of Plastics Or The Like (AREA)

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• 2001
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