FR2557499A1 - METHOD FOR MANUFACTURING COMPOSITE ARTICLE BY COEXTRUSION AND COMPOSITE ARTICLE OBTAINED - Google Patents

Abstract

METHOD FOR MANUFACTURING AN ARTICLE BY BIMATE EXTRUSION AND ARTICLE OBTAINED. THE PROCESS, ACCORDING TO THE INVENTION, CONSISTS OF MAKING A FLAT, OR TUBULAR, OR SHAPED ARTICLE INCLUDING A CORE 13 OF POLYETHYLENE TEREPHTHALATE WITH 0 TO 50 MINERAL LOADS AND PRESENTING A SEMI-CRYSTALLINE STRUCTURE, AND A LAYER OF POLYETHYLENE TEREPHTHALATE. COATING 14, 15 IN AT LEAST ONE OTHER THERMOPLASTIC MATERIAL, BY COEXTRUSION OF A COMPOSITE MATERIAL 12; IMMEDIATELY AFTER EXTRUSION, THE LATTER IS TREATED BY MEANS 20, 21, 22 WITH A TEMPERATURE LOWER THAN THE CRYSTALLIZATION TEMPERATURE OF POLYETHYLENE TEREPHTHALATE CONTAINING THE SAID PROPORTION OF LOADS, IN PARTICULAR AT A TEMPERATURE OF THE ORDER OF 40 TO 80, AND THE SAID SECOND THERMOPLASTIC MATERIAL IS USED AS A THERMAL BUFFER SLOWING THE TEMPERATURE BALANCE BETWEEN POLYETHYLENE TEREPHTHALATE AND THE SAID MEANS 20, 21, 22, SO AS TO ENSURE THE TERECETROPHTHALATE FLENEPHTHALATE FOR POLYETHYLENE TEREPHTHALATE AND THE SAID MEANS 20, 21, 22, TO ENSURE THE TERECETROISHTHORALATE FLENEPHTHORALATE OF POLYETHYLENE TEREPHTHALATE. IT PRESENTS THE DESIRED SEMI-CRYSTALLINE STRUCTURE. APPLICATION TO THE MANUFACTURING OF ARTICLES INTENDED FOR INDUSTRIAL OR TECHNICAL APPLICATIONS.

Description

The present invention relates to a method of manufacturing an article

by extrusion, and an article

obtained by this method.

  It is particularly interested in the manufacture of articles comprising a core of polyethylene terephthalate (or PETP) coated with a coating layer

  in another thermoplastic material.

  When injected at its temperature, it is known that

  normal transformation rature, greater than its plastoelasticity temperature and for example of the order of 210 to 220 C, in a mold heated to a temperature of the order of 130 C, that is to say under these conditions him avoiding a thermal shock, the PETP acquires at a temperature of less than 140 ° C, while cooling slowly, a very opaque semi-crystalline structure

  homogeneous, distinguished by eminent mechanical properties.

  as well as very good characteristics

  in terms of chemical resistance and crack

  under constraint, particularly when it contains

up to 50% of mineral charges.

  This structure is characterized by a very low coefficient of thermal expansion (1.8.10-5) and an almost total absence of internal tension which largely prevent the articles obtained from deformation after use, but in case of elevation. of the temperature. In addition, the remarkable stiffness of the parts obtained (flexural modulus of the order of 16,000 MN / M2) and the high bending temperature (of the order of

  240 C) make it possible to reduce the usual thickness of articles

  and result in weight gains.

  In addition, PETP is cheaper than

  other crystalline thermoplastics.

  However, despite its qualities when treated under these temperature conditions, PETP has a poor development. Indeed, if it admits high proportions of charges, contributing largely to its excellent properties, these high proportions of charges alter the surface of the articles obtained, which have a satiny and heterogeneous appearance making them unsuitable as such.

  for certain uses requiring a smooth surface state.

  More generally, the need to heat the mold and then to slowly cool the injection temperature to less than 140 [deg.] C. if it is desired to obtain a semi-crystalline structure leads, on the one hand, to energy expenditure. and on the other hand at low rates, incompatible with exploitation on the industrial scale; in addition, the stiffening temperature of the PETP is much lower than 140 ° C, and the rates are further weakened because, after obtaining the crystallization temperature, it is still necessary to

  wait to unmold the mold, heated to a temperature

  higher than this temperature, allowing the

  demolding, has reached this one again.

  The object of the present invention is to overcome these disadvantages of PETP and, thus, to allow its use at the industrial level for the production of articles having a smooth surface state, while having the mechanical, physical and chemical characteristics resulting from a semi-crystalline structure of PETP. For this purpose, the invention proposes to apply to the manufacture of articles having a PETP core of semi-crystalline structure, having the mechanical, physical and chemical characteristics related to this structure, and a coating layer in at least another thermoplastic material which in turn makes it possible to obtain a smooth surface state, the process known under the name of

"multi-material extrusion".

  It is known that this method consists, when it is desired to obtain an article comprising a core of a first thermoplastic material and a coating layer of this core in at least a second thermoplastic material, to manufacture a composite material by simultaneously extruding said first and second plastics brought to a temperature above their respective plastoelasticity temperature, in amounts sufficient to respectively form the core coating layer, and to immediately apply to said composite material obtained a treatment involving cooling, by means having a temperature below the hardening temperature of the

second plastic material.

  This well-known method is characterized by high production rates, unrivaled

  with those of the molding processes.

  It is also characterized by the application to the composite material obtained by extrusion, immediately after this extrusion, of the above-mentioned treatment, which may consist of a simple cooling, or of forming by suitable means whose temperature

  is generally of the order of 60 C + 20 C.

  However, if the PETP injected at its normal temperature of transformation in a mold heated beyond C allows to obtain a semicrystalline structure particularly interesting in terms of mechanical, physical and chemical properties, the advent of PETP

  brought to its normal processing temperature, that is

  that is to say at a temperature above its plasto-elasticity temperature, in contact with such cold means leads to obtaining perfectly transparent parts having an amoxphe structure, but can not be suitable for the manufacture of industrial and technical parts. because of too weak physical characteristics, close to those of chloride

of polyvinyl.

  To avoid obtaining such an amorphous structure, it could be proposed to practice the known process of extrusion multi-material taking care to slow down

  cooling of the composite material after extrusion

  if we. However, such a method would require a considerable slowing of the extrusion rates and expensive means to prevent too rapid cooling of the composite material, assuming moreover that one can find, to form the coating layer, a thermoplastic material clean to give

satisfaction in these conditions.

  Now, quite unexpectedly, the present invention proposes to apply the extrusion process

  multi-material as it is known, that is to say in application

  cant immediately after extrusion, to the composite material obtained, a treatment involving cooling thereof, by so-called "cold" means, that is to say that one uses at a temperature of the order of C + 20 C, to manufacture articles comprising

  including a PETP core, while obtaining from this material

  the semi-crystalline structure interesting for

  industrial and technical parts.

  For this purpose, the present invention proposes to manufacture an article comprising a PETP core comprising 0 to 50% mineral filler and a coating layer of this core in at least one other thermoplastic material, by a process consisting in manufacturing a material composite by simultaneously extruding the PETP thus loaded and said other thermoplastic material, both of which are carried at a temperature above their respective plasto-elasticity temperature, in amounts sufficient to form respectively the coating layer and the soul, and to immediately apply to the composite material obtained a treatment involving a cooling thereof, by means having a temperature also lower than the crystallization temperature of the polyethylene terephthalate containing said proportion of filler, and more precisely at a temperature of the order of 40 to 80 C; in accordance with the present invention, this treatment is applied using said other thermoplastic material as a

  of thermal buffer slowing the balancing of the tempera-

  temperatures between the still fluid PrTP and said means, so as to ensure the PETP sufficiently slow cooling

  to have a semi-crystalline structure.

  Thus, although the composite material undergoes immediately after extrusion processing by so-called "cold" means if their temperature is compared with the crystallization temperature of the PETP, that is to say at a temperature of the order of 40 to 80 C which is traditional extrusion process while the crystallization temperature of the PETP is of little inferior

  below 140 ° C, sufficient cooling is achieved.

  PETP to acquire the particularly advantageous semicrystalline structure

  mentioned above, and not the usual amorphous structure

  linked to a contact with so-called "cold" means, an amorphous structure that one seeks to avoid

according to the invention.

  The semi-crystalline structure is obtained with the advantages

  traditionally related to extrusion, namely

  high production rates, which are not comparable to those allowed by the C-molding usually used to obtain such

  structure and with a considerable expenditure of energy

  considerably less than that implied by a

such hot molding.

  The articles obtained furthermore have a smooth surface state, related to the presence of the coating layer, and thus suitable for a wide range of uses, and for example for

car body.

  In addition, insofar as the layer of enro-

  In direct contact with the so-called "cold" means is able to harden more quickly than the PETP core, it is possible to perform a shaping of the

  multilayer material obtained while only being rigid

  a skin of the coating layer, that is to say even when the PETP has not reached its stiffening temperature much lower than 140 C, which allows

  in particular to obtain shaped articles in a

particularly fast.

  Other features and advantages of the process

  according to the invention will emerge from the description below.

  below, relating to several non-limiting modes of implementation, as well as the attached drawings which make

  integral part of this description.

  FIG. 1 illustrates, in a schematic sectional view of an installation of implementation, a

  method according to the invention of extruding a material

  composite material and then subject it to

  diatement, a treatment involving its cooling

  and of which three variants are illustrated.

  FIG. 2 illustrates, in a similar view, a method according to the invention consisting in extruding a sheath-shaped composite material, which is then subjected immediately to a treatment involving

  a cooling and of which two variants are illustrated.

  Reference is made first to FIG. 1, where a so-called "tri-material" extrusion head of known type, having three extrusion channels 2, 3, and 4, which have inputs, is schematized in FIG. separated 5, 6, 7 for the reception of a respective material to be extruded as schematically arrows 8, 9, 10, and gradually thin in the form of a slot from this input so as to be superimposed flat to define a single slot-shaped outlet 11, and to produce at this outlet a flat composite material 12 having a core 13 formed of the material extruded through the channel 2, which is interposed between channels 3 and 4, and a coating of this core 13 defined on one side thereof by a layer 14 formed by the material extruded through the channel 3 and on the other side of this core by a layer

  formed by the material extruded through the channel 4.

  Immediately at exit 11 of the extrusion head

  1, this composite material 12 is calibrated by

  passage in a flat die 16, which will be noted that it -

  could also be integrated directly to the extrusion head 1; the die 16 has an inlet 17 placed in the immediate vicinity of the outlet 11 of the extrusion head 1, in the direct extension of this outlet, to receive the composite material 12; it also has an output 18 for the material

calibrated composite.

  This output 18 constitutes the output of the extruder itself, which further comprises means, not shown, for introducing at the inlet 5,

  6, 7 of each of the channels 2, 3, 4 a thermally

  plastic heated to a temperature higher than its

  temperature of thermoplasticity and at a specific pressure

  undermined. All these elements of the extruder 19, as well as the operating parameters of the latter such as temperature and pressure of the materials introduced into the different channels 2, 3, 4 are traditional,

and known to those skilled in the art.

  According to the present invention, the channel 2, intended to form the core 13 of the composite material 12, is fed at its PETP inlet loaded with 0 to 50% of inorganic fillers such as mica, biotites or similar mineral fillers, and / or glass fibers, and brought to a temperature above its plastoelasticity temperature, and for example of the order of 210 to 220 ° C., these figures being given by way of example

non-limiting.

  The channels 3 and 4 are in turn supplied with other thermoplastic materials chosen according to the characteristics that it is desired to give to the coating layers 14 and 15, also brought to a

  temperature above their plasto-

  elasticity; for example, the channel 3 and the channel 4 can thus be fed with polycarbonate resin,

  ABS, polystyrene, methacrylate, or terephthalate

  polybutylene, other thermoplastics pretending to coextrusion with PETP can naturally be chosen without departing from the scope of the present invention; the temperature at which these materials are introduced into the channels 3 and 4 is for example of the order of 240 C; the whole of the extrusion head 1 and the flat die 16 is advantageously heated to a temperature specific to

  maintain all thermoplastics introduced

  in channels 2, 3, 4 at a higher temperature than

  than their plasto-elasticity temperature up to

the exit 18 of the extruder 19.

  According to the present invention, the composite material 12 is immediately subjected to the exit 18

  from the extruder 19, to a treatment involving a cooling

  said means 20, 21, 22 having a temperature below not only the curing temperature of the thermoplastics locating the coating layers 14 and 15, to cause

  the hardening of the latter, but also

  than the crystallization temperature of the optionally loaded polyethylene terephthalate, as it has been

  introduced in channel 2, although it is desired to

  give this PETP the desired semi-crystalline structure.

  For this purpose, means 20, 21, 22, brought to a temperature of the order of 40 to 80 ° C., are successfully used, depending on the gloss that it is desired to give to the coating layers 14 and 15, using the thermoplastic materials constituting the latter as a thermal buffer slowing down the temperature equilibration between the PETP constituting the core 13, still fluid, and these means 20, 21, 22, so as to ensure the PErP still fluid cooling sufficiently slow to

  it has the required semi-crystalline structure.

  As an example of a means thus placed immediately

  at the outlet 18 of the extruder 19 and brought to a temperature of the order of 40 to 80 ° C to harden the coating layers 14 and 15 without causing a cooling of the PETP resulting in an amorphous structure thereof ci, thanks to the thermal buffer. What constitutes the coating layers 14 and 15 is illustrated in a non-limiting way: either a cooler 20 of known type, for example water-circulating, that the composite material 12 passes through without any change in shape, when it is desired to produce an article 23 in the form of a strip or, after cutting, a plate; it will be appreciated that in this case, not only flat articles as described, but also various profiles can be made in accordance with the present invention; or a shell 21 formed of two rollers 24 and 25 between which the composite material 12 engages immediately at the outlet 18 of the extruder

  19, which imposes on this material a reduction in thickness.

  to also produce a flat web material 26 which can be cut next; - Stamping means 22 comprising a punch 27 and a die 28, to transform the

  composite material 12 flat in a shaped material.

  Depending on the case, the cooling device, the rollers 24 and 25, the punch 27 and the matrix 28 are brought to a temperature of the order of 40 to 80 C and the PETP constituting the core 13 passes through them without sudden cooling, thanks to the thermal buffer

  ensured by the coating layers 14 and 15.

  Naturally, these three examples of means 20, 21, 22 should not be considered as limiting, and other means treating the composite material 12 under the same conditions including temperature

  immediately at the exit 18 of the extruder 19 for

  could be used without

of the scope of the present invention.

  Such means, as well as the means 20, 21, 22 are known to those skilled in the art and do not require

not a more complete description.

  Reference will now be made to FIG. 2, where a sheath extrusion head has been schematized at 29.

  type also known to those skilled in the art.

  In a manner known per se, the extrusion head 29 has three channels 30, 31, 32 each of which has an inlet 33, 34, 35 in order to receive appropriate means, not shown, a respective thermoplastic material heated to a temperature superior to his

  plasto-elasticity temperature and subjected to a

  determined, as schematized in each case an arrow 36, 37, 38 .; these three channels meet in a single channel 39 arranged between a central core 40 and a peripheral body 41 of the same axis 42, this channel 39 having an annular section transversely to this axis 42 and defining for all three channels 30 , 31, 32 a common output 43 which constitutes the output of the extruder; the annular channel 39 has, between its zone o join the channels 31, 32 and the outlet 43, a narrowing 44 calibration. These arrangements are known in themselves to those skilled in the art and make it possible to extrude at 43 a composite material 45 in the form of a sheath, having a wall 46 comprising a core 47 formed of the thermoplastic material introduced into the channel 34. inlet 31 thereof, and two coating layers with a coating layer 48 facing the inside of the sheath and formed by the thermoplastic material introduced into the channel 30 at the inlet 33 of the this, and a coating layer 49 facing the outside of the sheath and formed by the thermoplastic material

  introduced into the channel 32 at the inlet 35 thereof.

  According to the present invention, the thermoplastic material introduced at 34 in the channel 31, and constituting the core 47 of the material 45, is a PETP introduced into the extrusion head 29 and maintained in the latter at a temperature above its temperature. plastoelasticity, and for example at a temperature of the order of 210 to 220 C; this PETP contains from 0 to 50% of selected mineral charges in the same manner as in the example described with reference to FIG.

  and / or glass fibers, depending on the characteristics

  what is expected of the material 45; the thermo

  plastic constituting each of the coating layers 48 and 49, identical or different, can be chosen

  in the same range as the thermoplastic material

  the coating layer 14 or the coating layer of the example of FIG. 1, with a temperature, for example of the order of 240.degree. C., in the extrusion head 29 suitably heated to maintain all the materials thermoplastics introduced through the channels 30, 31, 32 at a higher temperature

  at their temperature of elasticity.

  These parameters are also known to man

of career.

  In accordance with the present invention, immediately

  At the outlet 43 of the extruder, the material 45

  is subjected to a treatment that involves its cooling

  by means having a lower temperature than

  at least the curing temperature of at least the coating layer 49 facing outwards from the

  sheath in order to cause the hardening of this

  However, the temperature of these means is also lower than the crystallization temperature of the polyethylene terephthalate optionally loaded as it is at its introduction in the channel-31, and the thermoplastic material constituting the coating layer 49 is used. of thermal buffer slowing the temperature equilibration between the polyethylene terephthalate forming the core 47 and

  these means, so as to ensure that the terephthalate

  still fluid ethylene cooling sufficiently slow to

  it has a semi-crystalline structure.

  By way of example of such means, there is illustrated: either a cooling device 50 of known type, for example with water circulation, that the material

  cross immediately at exit 43 of the extrusion

  deuse, when it is desired to obtain an article 51 in the form of multilayer wall tube; - Or blowing means 52 also arranged immediately at the outlet 43 and having two mold halves 53, 54 initially separated from one another and placed on either side of the material 45 as is schematized in A , and that is then closed on a section 55 of this material before injecting air 56 in this section 55 to press against the respective indentations 57, 58 of the two mold halves 53, 54 as it is schematized in B; again separating the two mold halves 53 and 54 releases a parison which can either be used as it is when the article to be manufactured is to be in the form of a container having a PETP core multilayer wall, or to be divided in two. halves 59, 50 as schematized in C, each of these halves then constituting an article comparable to that obtained by stamping at 22 in the case of the implementation mode

illustrated in Figure 1.

2557499.

  These means 50 and 52 are only a non-limiting example of means that can be used, immediately at the outlet 43 of the extruder, to treat a material 45 while cooling without causing an amorphous structure of the PETP; these means 50 and 52, as well as those which could be substituted for them, are advantageously maintained at a temperature of the order of 40 to 80.degree. C., depending on the gloss that it is desired to impart to the coating layer 49 turned to the outside; however, the use of this coating layer 49 as a heat buffer ensures that the core 47 is cooled sufficiently slowly that the PETP constituting it

  has the desired semi-crystalline structure.

  It is easy to understand that the implementation of the method according to the present invention, in the variants which have been described as in other variants that would not be outside the scope of the present invention,

  makes it possible to produce articles of varied shapes,

  a PETP core of semicrystalline structure with the resulting advantages in a known manner and a coating of another thermoplastic material selected according to desired surface characteristics of the article, which allows many applications,

  for example for the production of coach parts-

  automotive, protective housings, etc ...

  Naturally, although the process according to the invention has been described with reference to a tri-material extrusion, it is easy to see that the number of coextruded materials is not critical, since the material leaving the extruder is , outraged

2557499.

  a PETP core, at least one coating layer of another thermoplastic material capable of constituting a

  thermal buffer as defined.

Claims (10)

  A method of manufacturing, by extrusion, an article comprising a core (13, 47) of a first thermoplastic material and a layer (14, 15, 48, 49) for coating said core with at least a second material thermoplastic, consisting of manufacturing a composite material (12, 45) by simultaneously extruding said first and second plastics   temperature above their plasto-   respective elasticity, in amounts sufficient to form respectively the coating layer and the core, and to immediately apply to the composite material   obtained (12, 45) a treatment involving a cooling   by means (20, 21, 22, 50, 52) presented   both a temperature below the temperature of   hardening of the second plastic material,   in that the first plastic material is a polyethylene terephthalate having from 0 to 50% of inorganic fillers, and in that said treatment is applied to the composite material (12, 45) by means (20, 21, 22, 50, 52) having a temperature also lower than the crystallization temperature of the polyethylene terephthalate containing said proportion   charge, using said second thermo-material   plastic as a thermal buffer slowing   temperature balancing between the polyethylene terephthalate   ethylene still fluid and said means (20, 21, 22, 50, 52), so as to ensure the polyethylene terephthalate-cooling sufficiently slow to present a semi-crystalline structure.   2. Method according to claim 1, characterized in that the temperature of said means (20, 21, 22) is of the order of 40 C to 80 C.   3. A method according to any of the claims   cations 1 and 2, characterized in that one extrudes a flat composite material (12).   4. Method according to claim 3, characterized in that said treatment consists of shaping the flat composite material (12) immediately after having extruded and before rigidification of the PETP, by means (22) having said temperature lower than the crystallization temperature of the polyethylene terephthalate containing said proportion of fillers, using said second thermoplastic material as a heat buffer.   5. Method according to claim 4, characterized in that the flat composite material is shaped (12) parestamping (22).   6. Method according to claim 3, characterized in that said treatment consists in subjecting the flat composite material (12) immediately after having extruded it and before stiffening the PETP, to a calendering by means (21) having said temperature lower than the crystallization temperature of the polyethylene terephthalate containing said proportion   charge, using said second thermo-material   plastic as a heat buffer.   7. Process according to any one of the   cations 1 and 2, characterized in that one extrudes a tubular composite material (45).   8. The method according to claim 7, characterized in that said treatment consists in shaping the tubular composite material (45) immediately after having extruded it and before stiffening the PETP, by means (52) having said temperature less than the crystallization temperature of the polyethylene terephthalate containing said proportion of filler, using said second thermoplastic material as a heat buffer.   9. The method of claim 8, characterized in that said treatment is a blow in a mold. 10. Article obtained by the implementation of the   process according to one of claims 1 to 9,   and having a polyethylene terephthalate core (13, 47) having from 0 to 50% of the mineral fillers and a coating layer (14, 15, 48, 49) of another thermoplastic material, said core having a semi-crystalline structure.