Process for the manufacture of radical ethylene terpolymers and radical ethylene copolymers.

The present invention relates to a novel terpolymers of the manufacturing process of ethylene and ethylene copolymers.

More specifically, the invention relates to a new manufacturing process of radical ethylene terpolymers comprising units derived from a (meth) acrylate and units derived from maleic anhydride and of ethylene radical copolymers comprising units derived from a (meth) acrylate and radical ethylene copolymers comprising moieties derived from maleic anhydride.

In French patent application No. 2498609, the Applicant has described an ethylene terpolymers manufacturing method comprising derivatives of ester units (meth) acrylic acid and units derived from maleic anhydride, by copolymerization high pressure in the presence of at least one free radical initiator, a mixture of ethylene, of (meth) acrylic acid and maleic anhydride. In the process described in Patent No. 2,498,609 the introduction of the monomers (meth) acrylic acid and maleic anhydride in the polymerization reactor is effected by pressure pumping a solution of maleic anhydride in the ester (meth ) acrylic acid, mixing this solution with the ethylene flow and homogenization of this mixture before are feed into the polymerization reactor, said homogenisation being performed in a Venturi type homogenizer and then in a spiral homogenizer.

The Applicant has discovered, in a surprising way, that in such terpolymers of ethylene manufacturing method comprising derivatives of ester units (meth) acrylic acid and units derived from maleic anhydride, ester monomers ( meth) acrylic and maleic anhydride can be introduced into the polymerization reactor being fed directly into the said reactor, that is to say independently of the ethylene stream.

The present invention thus provides a radical terpolymers manufacturing method of the ethylene copolymer comprising units derived from at least one (meth) acrylate (the alkyl group having 1 to 6 carbon atoms) and units derived from maleic anhydride by copolymerization in the presence of at least one free radical initiator, a mixture of ethylene, (meth) acrylate and maleic anhydride in a device comprising a primary compressor whose delivery pressure is between 200 and 300 bars connected to a secondary compressor which is connected directly to a polymerization reactor, in which fresh ethylene is fed at the intake of said primary compressor and the said copolymerization is carried out in said polymerization reactor at a pressure between 1000 and 2500 bars and at a temperature between 140 and 280 ° C characterized in that at least one of the monomers (meth) acrylate and maleic anhydride is fed directly into said polymerization reactor, that is to say independently of the ethylene stream in the presence of a solvent satisfying the following requirements:<ul><li>be a good solvent for the monomer,</li><li>have a constant vis-à-vis the ethylene negligible transfer, and</li><li>have a boiling point between 100 and 250 ° C.</li></ul>

Unexpectedly, despite the lack of standardization of monomers prior to their introduction into the reactor, copolymerization is performed very well according to the present invention.

Several embodiments can be envisaged to prepare the terpolymers according to the present invention, providing great flexibility in the claimed process.

In a first embodiment of the invention, the monomers (meth) acrylate and maleic anhydride are introduced both directly, that is to say independently of the ethylene stream, in the reactor as a solution of maleic anhydride in the (meth) acrylate.

According to a variant of this first embodiment, an extra (meth) acrylate is fed at the intake of the secondary compressor. According to another variant of this first embodiment, an extra maleic anhydride is fed at the intake of the secondary compressor.

In a second embodiment of the invention, maleic anhydride is fed directly, that is to say independently of the ethylene flow to the reactor and the (meth) acrylate is fed at the intake of the compressor secondary.

In a third embodiment of the invention, the (meth) acrylate is fed directly, that is to say independently of the ethylene flow to the reactor and maleic anhydride is fed at the intake of the compressor secondary.

By varying the location of the comonomers in the reactor, it can affect the distribution of the monomer units and the molecular distribution of the resulting terpolymer.

When introduced alone maleic anhydride according to the present invention, whether the intake of the secondary compressor or directly into the polymerisation reactor, it is necessary to feed as a solution in a solvent of the maleic anhydride, whose characteristics are indicated below.

The introduction of (meth) acrylate and maleic anhydride in the reactor according to the present invention is carried out as a solution of maleic anhydride in the (meth) acrylate to concentrations less maleic anhydride to about 300 g / l, or in the form of a solution of maleic anhydride and (meth) acrylate in a solvent for maleic anhydride.

Said solvent maleic anhydride must meet the following requirements:<ul><li>be a good solvent for maleic anhydride,</li><li>have a constant vis-a-vis the transfer negligible ethylene,</li><li>have a boiling point between 100 and 250 ° C.</li></ul>

Solvents of maleic anhydride can be used according to the invention are for example propylene carbonate and dimethylformamide.

Some (meth) acrylates are also fed according to the present invention in solution in a solvent satisfying the following requirements:<ul><li>good solubility of the (meth) acrylate,</li><li>constant vis-à-vis the ethylene negligible transfer,</li><li>boiling point between 100 and 250 ° C.</li></ul>

The terpolymers can be produced by the process of the present invention include:<ul><li>50 to 99.2% by weight of units derived from ethylene,</li><li>0.5 to 40% by weight of units derived from a (meth) acrylate,</li><li>0.3 to 10% by weight of units derived from maleic anhydride.</li></ul>

Their melt index is between 0.1 and 500 dg / min. The usable polymerization reactor according to the invention can be a tubular reactor or an autoclave reactor and may include one or more zones.

The reactor bottom can be provided with an expansion valve for lowering the pressure to about 250 bar. Mixing the molten terpolymer obtained and unreacted monomers through said expansion valve and is sent to a separator operating under medium pressure. The terpolymer is collected at the bottom of said separator while the unreacted monomers are recycled after cooling and decantation-separation of low molecular weight polymers (less than or equal to 5000) contained therein, to the intake of the secondary compressor. The bottom of the medium pressure separator may be provided with an expansion valve connected to a low pressure hopper to the bottom of which is recovered the terpolymer, low pressure hopper returns being recycled to the intake of the primary compressor.

As mentioned above, the secondary compressor is directly connected to the polymerization reactor; its discharge pressure is equal to that of the reactor, near the head losses.

The free radical initiators used according to the invention are the initiators conventionally used in such high pressure polymerization processes, such as for example the 2-ethylhexyl peroxydicarbonate, di-tertiary butyl peroxide, butyl perbenzoate, ethyl 2 perhexanoate t-butyl peroxide isopropanoyl.

One can simultaneously use multiple initiators in the same zone of the reactor. As is well known to those skilled in the art, the choice of the initiator depends on the polymerization temperature.

Known manner, can be introduced into the reaction mixture a transfer agent to control the molecular weight of the obtained product. Such transfer agents are for example alkanes such as propane and butane, olefins, in particular α-olefins, aldehydes, ketones, etc.

Terpolymers manufactured according to the present invention find many applications, particularly in compositions for sealants, coating metals, hot melt adhesives, described in French Patents 2,505,731, 2,505,859 and 2,504,933 of applicant.

The present invention also provides a process for making free-radical ethylene copolymers comprising moieties derived from a second monomer chosen from (meth) acrylates and maleic anhydride by copolymerization in the presence of at least one radical initiator free of a mixture of ethylene and said second monomer in a device comprising a primary compressor whose delivery pressure is between 200 and 300 bars connected to a secondary compressor which is connected directly to a polymérisaton reactor, wherein the fresh ethylene is fed at the intake of said primary compressor and the said copolymerization is carried out in said polymerization reactor at a pressure between 1000 and 2500 bars and at a temperature between 140 and 280 ° C, characterized in that said second monomer is fed directly into said polymerization reactor, that is to say independently of the ethylene stream in the presence of a solvent satisfying the following requirements:<ul><li>be a good solvent for the monomer,</li><li>have a constant vis-à-vis the ethylene negligible transfer, and</li><li>have a boiling point between 100 and 250 ° C.</li></ul>

The second monomer may, if necessary, be introduced according to the present invention in solution in a solvent whose characteristics are those indicated above, that is to say:<ul><li>good solvency said second monomer</li><li>constant vis-à-vis the ethylene negligible transfer</li><li>boiling point between 100 and 250 ° C.</li></ul>

The free radical initiators suitable for the manufacture of the copolymers according to the invention are the same as those mentioned above.

The method of the present invention allows the manufacture of radical copolymers comprising 60 to 99.5% by weight of units derived from ethylene and 0.5 to 40% by weight of units derived from a (meth) acrylate as well as copolymers radical comprises 90 to 99.7% by weight of units derived from ethylene and 0.3 to 10% by weight of units derived from maleic anhydride.

The following examples illustrate the invention without limitation.

example 1

In a device comprising a primary compressor whose delivery pressure is 250 bars, a secondary compressor connected to a high pressure polymerization reactor, the reactor is fed with 62 l / h of a solution containing 400 g / l of maleic anhydride in a mixture of 80% ethyl acrylate 20% propylene carbonate. The flow of ethylene fed is 7 t / h. The reactor operates at a pressure of 1800 bar and a temperature of 195 ° C.

Was collected 0.7 t / h of terpolymer resin containing 3.5% by weight of units derived from maleic anhydride and 4.5% by weight of units derived from ethyl acrylate and having a melt index 6 dg / min.

example 2

It uses the same device as in Example 1.

the reactor is fed with 62 l / h of the same solution of maleic anhydride as in Example 1. The flow rate of ethylene fed is 7 t / h. The reactor operates at a pressure of 1900 bar and at a temperature of 195 ° C. Is fed in addition 200 l / h of ethyl acrylate to the intake of the secondary compressor.

Was collected 0.7 t / h of terpolymer resin containing 3.5% by weight of units derived from maleic anhydride and 30% by weight of units derived from ethyl acrylate and having a melt index of 18 dg / min.

example 3

It uses the same device as in Example 1.

The reactor is fed with 80 l / h of ethyl acrylate. The flow of ethylene fed is 10 t / h. The reactor operates at a pressure of 1600 bar and at a temperature of 250 ° C.

Was collected 1.4 t / h of copolymer resin comprising 5% by weight of units derived from ethyl acrylate and having a melt index of 0.2 dg / min.

example 4

It uses the same device as in Example 1.

The reactor is fed with 1 l / h of a solution containing 400 g / l of maleic anhydride in propylene carbonate. The flow rate of ethylene fed to the reactor is 100 kg / h.

The reactor operates at a pressure of 1700 bar and at a temperature of 205 ° C.

Was collected 10 kg / h of a copolymer resin comprising 4% by weight of units derived from maleic anhydride and having a melt index of 8 dg / min.