FR2498609A1 - TERPOLYMERS OF ETHYLENE, PROCESS FOR THEIR MANUFACTURE AND THEIR APPLICATION TO THE MANUFACTURE OF FILMS - Google Patents

Abstract

ETHYLENE TERPOLYMER CONTAINING REASONS DERIVED FROM MALEIC ANHYDRIDE. IT INCLUDES: -From 88 TO 98.7 IN MOLES OF PATTERNS DERIVED FROM ETHYLENE, -From 1 TO 10 IN MOLES OF PATTERNS DERIVED FROM AN ESTER CHOSEN FROM ALKYL ACRYLATES AND METHACRYLATES, THESE ALKYL GROUP HAVING 1 WITH 6 CARBON ATOMS, -DE 0.3 TO 3 IN MOLES OF PATTERNS DERIVED FROM MALEIC ANHYDRIDE. APPLICATION TO THE MANUFACTURING OF FILMS WITH A THICKNESS BETWEEN 10 AND 500MM (MICRONS).

Description

The present invention relates to novel polymers of ethyl

  and more particularly terpolymers comprising

derived from maleic anhydride.

  Terpolymers of olefin, vinyl acetate and maleic anhydride have already been described in East German Patent No. 89,485. Similarly, US Pat. No. 2,599,123 discloses terpolymers of ethylene, methyl acrylate and ethyl monomaleate which can be crosslinked and can be converted into films. Finally, Belgian Patent No. 818,609 describes

  vulcanizable terpolymers of ethylene, methyl acrylate and mono-

methyl or propyl maleate.

  The present invention relates to a new class of polymers comprising on the one hand ethylene as the main monomer, and on the other hand at least two comonomers including a (meth) acrylic ester and maleic anhydride. The polymers according to the invention are therefore

  terpolymers since they comprise at least three mononers. Facultati-

  they can take a fourth monomer copolymerizable with

  the first three and they are then called tetra-polymers.

  The polymers according to the invention comprise: from 88 to 98.7 mol% of units derived from ethylene, from 1 to 10 mol% of units derived from an ester chosen from alkyl acrylates and methacrylates , said alkyl group having 1

at 6 carbon atoms.

  from 0.3 to 3 mol% of units derived from maleic anhydride.

  In addition, the terpolymers according to the invention are characterized by a melt index (measured under the conditions of the standard

  ASIM D 1238-73) between 1 and 500 dg / min. Their polydispersity index

  Mw / Mn is generally greater than 6. Their Vicat temperature is between 30 C (high comonomer levels) and 85 C (low levels). When the polymers according to the invention comprise a fourth comonomer, it may be chosen from α-olefins having from 3 to 8 carbon atoms, alkyl monomaleates and dialkyl maleates, the alkyl groups of which have from 1 to 6 carbon atoms, vinyl acetate, carbon monoxide, and may be present at up to 5 mol%, the proportion of ethylene in the tetrapolymer

  being then reduced by the same amount as the range indicated above.

  The process for producing the terpolymers according to the invention consists in copolymerizing, in the presence of at least one free radical initiator, a mixture composed of 94 to 99% by weight of ethylene, 0.7 to 5% by weight of (meth) acrylic ester and from 0.2 to 0.9% by weight of maleic anhydride in a reactor maintained at a pressure of 1000 to 3000 bar and at a temperature of 170 to 280 C, to relax and then to separate the monomer mixture and the terpolymer formed in the reactor, and finally to recycle to the reactor the mixture of ethylene and monomers previously separated. In the process according to the invention, it is possible to provide a separate supply of fresh ethylene on the one hand and comonomers and recycled ethylene on the other. The introduction of the comonomers into the reactor is preferably by pressure pumping a solution of maleic anhydride in the (meth) acrylic ester, mixing this solution with the flow of ethylene and homogenizing said mixture before its entry in

  the reactor. By way of nonlimiting example, the mixture and the hoanogenicity

  can be performed simultaneously in a device Venturi type. In practice, it is observed that the recycled stream comprises 99 to 99.8% of ethylene and 0.2 to 1% of (meth) acrylic ester. Of course, it can be envisaged to separate the ethylene and the (meth) acrylic ester at this stage, but such an operation does not bring any advantages that allow

  to offset the corresponding increase in manufacturing cost.

  As initiators of free radicals for use in the

  In the context of the present invention, for example, peroxydicarboxylic acid

  2-ethylhexyl bonate, ditertiobutyl peroxide, tert-butyl perbenzoate, tert-butyl 2-ethyl perhexanoate. In a perfectly known manner it will also be possible to use, in the process according to the invention, one or more chain transfer agents, such as, for example, hydrogen, to regulate and control the characteristics of the polymer and in particular

its fluidity index.

  The process according to the invention is carried out continuously either in a stirred autoclave reactor comprising one or more zones or in a tubular reactor, for example described in German Patent No. 58,387. Downstream of the reactor are located an expansion valve and a separator operating under a pressure of 200 to 500

  bars. The method according to the invention can implement cooling

  polymer mixture and monomers between the expansion valve and the separator, for example according to French Patent No. 2,313,399 injecting ethylene at a lower pressure than the separator, said ethylene can be captured downstream of an exchanger of the recycling circuit. The terpolymers according to the invention can be used in many applications, either alone or mixed with other

  materials or polymers. As the ethylene / (meth) acrylate copolymers

  As they improve their properties, their applications depend on the melt index obtained by the use of the chain transfer agent. They also depend on the content of units derived from maleic anhydride. Thus, an important application of terpolymers having a melt index of between 1 and 10 dg / min and comprising from 0.3 to 1 mol% of units derived from maleic anhydride consists in the production of films. These films can have a thickness of between 10 and 500 IAm (microns) when they are obtained through a flat die and from 25 to 200 Km (microns) when they are obtained.

by extrusion blow molding.

  The following examples are given for illustrative purposes and not

  limiting of the present invention.

EXAMPLES 1 to 4

  A cylindrical autoclave reactor comprising three

  areas of a volume of 1 liter each and equipped with a paddle stirrer.

  The zones are separated by valve screens. Fresh ethylene

  m by a first compressor feeds the first zone. The second zone is fed with a homogeneous mixture of ethylene and maleic anhydride

  (AM) and ethyl acrylate (AE). Finally a solution of 2-ethyl perhexanoate

  terbutyl in a hydrocarbon cut is injected into the third

  sth zone. This is therefore the only reaction zone since it

  brings together the three comonomers and an initiator of free radicals.

  The proportions by weight of maleic anhydride and of ethyl acrylate with respect to ethylene in the following table are given in Table I below.

  the reaction zone and secondly the temperature in said zone.

  The reactor is maintained at a pressure of 1600 bars. At the bottom of the third zone of the reactor is placed an expansion valve for lowering the pressure to 300 bars. The mixture of the molten polymer on the one hand and gaseous monomers on the other hand, after having passed through the expansion valve, passes into a separating hopper. While the polymer is collected at the bottom of the hopper, the monomers are transported, after

  passing through a degreasing hopper, to a second compressor.

  On the other hand, a solution of maleic anhydride in ethyl acrylate is pumped under pressure and fed to the inlet of a venturi type homogenizer where it is mixed with the stream of recycled monomers from the second compressor. At the outlet of this venturi device, the mixture of the three monomers is fed to a spiral homogenizer then

  transferred to the second reactor zone.

  At the outlet of the separating hopper, the terpolymer produced is analyzed by infrared spectrophotometry and the proportions in moles

  of ethyl acrylate units and maleic anhydride units are

  and listed in Table I below. On the other hand the index of S fluidity of the polymer is determined according to the standard ASIM D 1238-73 and

expressed in dg / min.

  Then the following characteristics of the polymer - density, expressed in g / cm 3 and determined according to the standard are measured.

ASIM D 2839,

  - number average molecular weight Mn, determined by gel permeation chromatography, - polydispersity index, determined according to the same method and equal to the Mw / Mn ratio, Mw being the weight average molecular weight, - Vicat temperature, expressed in degrees. Celsius and determined according to

standard NF T 51-012 (1).

  The results of these measurements are collated in Table II below.

EXAMPLE 5

  The device of the preceding examples is used for copoly

  to merit ethylene, maleic anhydride and ethyl acrylate under the following conditions: Reactor pressure: 1200 bar Reaction zone temperature: 180 C The composition by weight of the monomer mixture in the reaction zone, the composition in moles of the terpolymer obtained and its melt index are given in Table I below. The polymer is

  then analyzed and characterized by its density, molecular weight and

  Mn and its polydispersity index, measured as described above

  and whose values are shown in Table II below.

EXAMPLE 6

  The device of the preceding examples for copolymer

  Reuse ethylene, maleic anhydride and butyl methacrylate (MAB) under the following conditions: Reactor pressure: 1800 bar Reaction zone temperature: 180 ° C

  The weight proportions of the comonomers in the reaction zone

  These are: 4.8% MAB, 0.38% Amine The obtained polymer has a melt index of 30 dg / min (measured

according to ASTM D 1238-73).

EXAMPLE 7

  The device of the preceding examples is used for copoly

  to merit ethylene, maleic anhydride and butyl acrylate (AB) under the following conditions: Reactor pressure: 2300 bar Temperature of the reaction zone: 260 ° C

  The weight proportions of the comonomers in the reaction zone

are:

1.3% AB, 0.23% AM

  The polymer obtained has a melt index of 2 dg / min (measured according to ASTM D 1238-73), a Vicat temperature of 65 ° C. and a density of 0.935 g / cm 3. Its analysis by infrared spectrophotometry makes it possible to demonstrate the presence of: - 2.0 mol% of units derived from butyl acrylate,

  - 0.8 mol% of units derived from maleic anhydride.

EXAMPLE 8

  The terpolymer obtained in Example 2 is converted by extrusion into

  blowing at a temperature of 140 C in a film of thickness 100 Pm

  (microns), the draw ratio being equal to 2.5 m / min.

  On the film obtained, the following properties are measured: - RE elastic resistance expressed in kg / cm 2 and determined according to standard NF T 51-034, - breaking strength RR (expressed in kg / cm 2) and elongation at break AR ( expressed as a percentage) determined according to the ASM standard

D 882-67.

  The following values are perfectly balanced in the longitudinal and transverse directions: RE = 51 kg / cm2 RR = 112 kg / cm2

AR = 540%.

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Claims (10)

  1. Terpolymer of ethylene comprising units derived from maleic anhydride, characterized in that it comprises: from 88 to 98.7 mol% of units derived from ethylene, from 1 to 10% by weight; moles of units derived from an ester selected from alkyl acrylates and methacrylates, said alkyl group having from 1 to 6 carbon atoms.   from 0.3 to 3 mol% of units derived from maleic anhydride.   2. Terpolymer according to claim 1, characterized in that   its melt index is between 1 and 500 dg / min.   3. Terpolymer according to one of claims 1 and 2, characterized   in that its polydispersity index is greater than 6.   4. Terpolymer according to one of claims 1 to 3, characterized   rised in that its Vicat temperature is between 30 C and 850C.   5. Terpolymer according to one of claims 1 to 4, characterized   in that it comprises up to 5 mol% of units derived from a fourth comonomer selected from "-olefins having from 3 to 8 carbon atoms, alkyl monomaleates and dialkyl maleates, the groups of which alkyl have 1 to 6 carbon atoms, vinyl acetate and carbon monoxide.   6. Terpolymer according to one of claims 1 to 5, characterized   in that it comprises from 0.3 to 1 mol% of units derived from maleic anhydride and in that its melt index is between 1 and 10 dg / min.   7. A method of manufacturing a terpolymer according to the claim   1, characterized in that it consists in copolymerizing, in the presence of at least one free radical initiator, a mixture composed of 94 to 99% by weight of ethylene, 0.7 to 5% by weight of (meth) acrylic ester and from 0.2 to 0.9% by weight of maleic anhydride in a reactor maintained under a pressure of 1000 to 3000 bar and at a temperature of 170 to 280 C, to relax and then to separate the mixture of monomer and terpolymer formed in the reactor, and finally to recycle the mixture to the reactor   ethylene and monomers previously separated.   8. Process according to claim 7, characterized in that the mixture recycled to the reactor comprises from 99 to 99.8% of ethylene and   0.2 to 1% (meth) acrylic ester.   9. Method according to one of claims 7 and 8, characterized   in that the free radical initiator is selected from among peroxydi   2-ethylhexyl carbonate, ditertiobutyl peroxide, perbenzoate   tert-butyl and tert-butyl ethyl-2-perhexanoate.   10. Application of a terpolymer according to claim 6 to   the manufacture of films of thickness between 10 and 500 m (microns).