The present invention relates to a manufacturing method of polyethylene or copolymer of ethylene by polymerization under high pressure (autoclave or tubular) in the presence of a pair of polymerization peroxidic initiators particularly in a wide temperature range .

State of the art

The low density polyethylenes and ethylene copolymers are generally manufactured in an autoclave or tubular reactor under high pressure, by introduction of ethylene continuously, one or more optional comonomers and one or more initiators organic peroxides generally diluted in an organic solvent. The pressure inside the reactor is generally between 500 and 5000 bars. The temperature during the initiation of the reaction is generally between 80 and 250 ° C (degree Celsius). The maximum reaction temperature is generally between 120 and 350 ° C.

The polymer conversion rate usually obtained with this type of process is of the order of 15 to 25%. Similarly, the productivity of such a process, expressed in grams of polyethylene produced per gram of peroxide initiator used, is generally between 1000 and 3000 g / g, more generally less than 2500 g / g.

The search for increased productivity and therefore cost is a constant concern of polyethylene producers. There is a need for a polyethylene manufacturing process which has high productivity, while maintaining a conversion rate interesting polymer.

Document US 2650913 discloses an ethylene polymerisation process in the presence of an initiator 2,2-bis (tertiary butyl peroxy) butane initiator but this leads to low productivity (see Example 1 of this document and test 3 below).

Also known document FR 2946653 discloses that 2,2-di- (t-amyl peroxy) propane but it is absolutely not used as the initiator.

The documents US 2008/0226891 is also known, EP 0273090 and EP 0259537 which disclose the use of 2,2-di- (t-amyl peroxy) butane, but the latter is used for the manufacture of very distinct polymers polymers of ethylene or copolymers of ethylene.

Finally, it is known EP 2673307, filed in the name of the Applicant, wherein it has been shown that certain organic peroxides diperketals type allowed to increase the productivity of the process to values above 3000 g / g in a temperature range initiation particular, between 150 and 200 ° C. This document illustrates by example the specific interest of 2,2-di (t-amyl peroxy) butane (50% diluted in isododecane known as supplied under the name Luperox ® 520M50) as an initiator of high productivity LDPE ( "Low Density PolyEthylene").

The aforementioned peroxide initiator satisfactory because it improves productivity and research productivity gain is a major goal of producing polyethylene resins.

Nevertheless, it is desirable to provide an even more significant improvement in productivity.

Summary of the Invention

Contrary to what could be expected by the skilled person, the applicant has surprisingly found that the use of a couple of organic peroxides diperketals formula

the R groups consisting essentially of alkyl groups C1 -C6, these two peroxides having a half-life temperature in one minute between 150 ° C and 185 ° C, allowed to reduce the specific fuel consumption (mass of polymer produced per gram peroxides injected) peroxide used in the initiation temperature range 140 ° C-200 ° C.

This results in the possibility to obtain higher productivities or equal to 3000 g / g for a initiation temperature range between 140 ° C and 200 ° C conventionally used for this type of process and increase high productivity reaction temperature (temperature

polymerization) between 200 ° C and 290 ° C for better thermal boot sequence, that is to say, better productivity with peroxides to achieve very high temperatures (T my x = maximum temperature attained by the exotherm of polymerization), typically 295-305 ° C, such as with di-tert-butyl peroxide.

Thus, the present invention relates to a manufacturing method of polyethylene or copolymer of ethylene, comprising a step of polymerization or radical copolymerization of ethylene in the presence:

- a first peroxide polymerization initiator selected from peroxides diperketals compounds of formula:

where Ri, R2, R3, R6, R7 and Rs consist of alkyl groups C1 -C10 substituted or unsubstituted linear, branched or cyclic,

- a second initiator, different from said first initiator, also consisting of a diperketal peroxide of formula (I).

In particular, the present invention relates to a manufacturing method of polyethylene or copolymer of ethylene by feeding ethylene continuously and eventual (s) comonomer (s) in a tubular reactor or autoclave, comprising a step of radical polymerization or copolymerization of ethylene at an initiation temperature ranging from 140 ° C to 200 ° C, at a pressure ranging from 1200 to 3000 bar in the presence of a first peroxide polymerization initiator selected from compounds diperketals peroxides of formula

where Ri, R2, R3, R6, R7 and Rs consist of alkyl groups in

C1 -C6,

characterized in that a second initiator, also consisting of a diperketal peroxide of formula (I) is present at the above step, the first and second peroxides, forming a mixture of peroxides, having a half-life temperature at a minute between 150 ° C and 185 ° C as measured in n-dodecane at a concentration of 0.1 moles per liter (mol.l "1 ) using a calorimeter curve of differential scanning (DSC ).

Determining the half-life temperature can be carried out simply from the DSC data used to characterize the thermal stability of the peroxide in question. Said temperature half-life to one minute is measured in n-dodecane at a concentration of 0.1 moles per liter (mol.l "1 ) using a calorimeter curve of differential scanning (DSC).

The thermokinetics decomposition curve recorded by this technique provides the kinetic parameters for thermal decomposition of unstable substances following an Arrhenius decay equation.

In the case of a treatment according to a kinetic order of n, the three parameters ko (pre-exponential factor), E a (activation energy) and n (order of the decomposition reaction) are linked and optimized so to minimize the differences between the model and the experimental curve.

The half-life temperature T is the temperature at which, after the time t, the amount of thermally unstable material remaining is equal to half of the initial amount.

It should be noted that, hereinafter, the term "half-life temperature in one minute" always refers in the context of a measurement carried out in n-dodecane at a concentration of 0.1 mole per liter (mol.l "1 ).

The term "C1 -C10 alkyl", preferably "C1-C6" means that it is a group derived from alkane, substituted or unsubstituted linear, branched or cyclic, comprising at least one (1) carbon atom and up to ten (10), preferably up to six (6) carbon atoms. This is typically for non-branched structures, for example methyl, ethyl, n-propyl, n-butyl, n-pentyl or n-hexyl.

According to one embodiment, the invention is also particularly enhanced when the half-life temperature in one minute is between 160 ° C and 170 ° C as measured in n-dodecane at a concentration of 0.1 mol per liter (mol.l "1 ).

Preferably, the half-life temperature in one minute of said first initiator is between 140 ° C and 180 ° C, preferably between 150 ° C and 170 ° C, and more preferably between 155 ° C and 165 ° C.

Preferably, the half-life temperature in one minute of said second initiator is between 150 ° C and 185 ° C, preferably between 155 ° C and 175 ° C, and more preferably between 160 ° C and 170 ° C.

Thus, the Applicant has tested the 1, 1 -di (tert-amyl peroxy) cyclohexane

(Luperox ® 531 M60), 1, 1 -di (tert-butylperoxy) -3,3,5-trimethylcyclohexane (Luperox ® 231 M50) and 1, 1 -di (tert-butylperoxy) -cyclohexane (Luperox ® 331 M50) which have half-life of Temperatures one minute respectively 150 ° C, 153 ° C and 155 ° C. The results of association of one of these peroxides with such 2,2- (di-tert-amyl peroxy) butane (Luperox ® 520M50) are good - a "booster" effect of productivity is clearly seen - but less good when both associated diperketals both have a half-life temperature in one minute between 160 ° C and 170 ° C.

It should be noted here that the three abovementioned diperketals peroxides have a central carbon ring so that, for these components, the groups R 4 and R 5 of formula (I) are linked so as to form said ring.

Similarly, it has been observed by the applicant that for the ethyl 3,3-di (tert-butylperoxy) butyrate (Luperox ® 233M50) and ethyl 3,3-di (tert-amylperoxy) butyrate (Luperox ® 533M65), respectively having a half-life temperature in one minute of 175 ° C and 173 ° C, the association with e.g., 2,2- (di-tert-amylperoxy) butane (Luperox ® 520M50) give good results - a "booster" effect of productivity is clearly observed-but not as good as when the two associated diperketals both have a half-life of one minute temperature between 160 ° C and 170 ° C.

Finally, it is noted that the applicant has tried the combination of n-butyl-4,4-di (tert-butylperoxy) -valerate (Luperox ® 230), having a half-life temperature in one minute of 163 ° C, with 2,2- (di-tert-amylperoxy) butane (Luperox ® 520M50). The observed results are satisfactory, in other words a "booster" effect productivity is observed, but the n-butyl-4,4-di (tert-butylperoxy) -valerate releases an amount of carbon dioxide (CO2) and likely important in an industrial application to be counter-productive or problematic by introducing an inert gas from the lower partial pressure of ethylene monomer. Thus, in general, organic peroxides having one ester function, like the Luperox ® 230, are a priori not retained in the context of the present invention not due to the absence of "booster" effect but because of their harmful release of CO2.

The Applicant has also discovered a very significant improvement of the invention when the two organic peroxides used differ structurally from one another from a single carbon, at the central groups R 4 or R 5. This is presented in the following with the 2,2 pair (di-tert-amylperoxy) butane (Luperox ® 520M50) and 2,2- (di-tert-amylperoxy) propane (in all examples below, diluted to 50% by weight in isododecane), but this effectiveness has been verified in the laboratory with other pairs of organic peroxides diperketals.

This particularly interesting structural relationship between the two diperketals is established when the group R 4 or R 5 of the first initiator is different from the corresponding group, or R 4 or R 5 of the second initiator, a single carbon.

This small difference in molecular structure it is noted that not absolutely foreshadowed conversion efficiency (ability of the peroxide to initiate a number of polymer chains by reacting initiation monomer) much higher.

Other features or embodiments of the invention are presented below:

- preferably the groups R 4 and R 5 are alkyl groups, C1 -C10 substituted or unsaturated, linear, branched or cyclic preferably C 1 -C 6 substituted or unsubstituted linear, branched or cyclic.

- preferably at least 1, preferably at least 2, preferably at least 3, preferably at least 4, preferably at least 5, preferably

at least 6, the groups R2 to R7 are alkyl groups C 1 -C 6 substituted or unsubstituted linear, branched or cyclic.

- preferably at least 1, preferably at least 2, preferably at least 3, preferably at least 4, preferably at least 5, preferably at least 6, the groups R2 to R7 are linear.

- preferably at least 1, preferably at least 2, preferably at least 3, preferably at least 4, preferably at least 5, preferably at least 6 of R 2 to R 7 are unsubstituted.

- preferably at least 1, preferably at least 2, preferably at least 3, preferably at least 4, preferably at least 5, preferably at least 6 of R 2 to R 7 are linear and unsubstituted.

- advantageously, the groups R2, R3, R6 and R 7 of the above two initiators each consist of a methyl group,

- preferably the group R 4 is a methyl group.

- preferably the groups R2, R3, R4, R6 and R 7 each consist of a methyl group.

- according to a preferred aspect of the invention, the groups R and R of the above two initiators each consist of an alkyl group C2-C5, preferably C2-C4.

- according to another advantageous aspect of the invention, the R5 group of the aforesaid two initiators is alkyl C1 -C2.

- according to a preferred solution offered by the invention, the first polymerization initiator is 2,2-di (tert-amylperoxy) butane.

- in the same way, according to a preferred solution offered by the invention, the second polymerization initiator is 2,2-di (tert-amylperoxy) propane.

- preferably, said first polymerization initiator is 2,2-di (tert-amylperoxy) butane and said second polymerization initiator is 2,2-di (tert-amylperoxy) propane.

- advantageously, the mixture / the proportion of the two peroxides diperketals / initiators has a part of the second initiator of between 2% and 50 mol% (all two perkétals peroxides representing 100% of the mixture), preferably between 10% and 40 mol%, still preferably between 15 and 35 mol%.

- preferably the total amount of said first and second initiators is between 1 and 10,000 ppm, preferably between 10 and 1000 ppm, still preferably between 50 and 150 ppm by weight based on the weight of polyethylene or final ethylene copolymer.

Said first and second initiators may be added to the reaction mixture together or separately.

Preferably, said first and second initiators are added together, and preferably they form a mixture of peroxides.

The polymerization or copolymerization can be carried out in further presence of at least one additional peroxide initiator. Preferably, said at least one additional peroxide initiator is not a compound of formula (I).

In particular, said at least one additional peroxide initiator is not a diperketal as defined in the independent claim of the present patent application.

This additional peroxide initiator may be selected from the group consisting of: tertiobutylperoxyneodécanoate the tertiobutylperoxypivalate the tertioamylperoxypivalate, di (3,5,5 trimethylhexanoyl) peroxide, dilauroyl peroxide, didecanoyl peroxide, tertioamyl peroxy-2-ethylhexanoate, the tert-butyl peroxy-2-ethylhexanoate, tertiary butyl peroxy-3,5,5-trimethylhexanoate, peroxy-3,5,5-trimethylhexanoate tertioamyl, tertbutyl peroxybenzoate, tertbutyl peroxyacetate the the ditertiobutylperoxyde and ditertioamyl peroxide.

The polymerization or copolymerization may be carried out in the presence of at least one additive, preferably selected from the group consisting of: antioxidants; UV protection agents; the implementation of agents, having the function of improving the final appearance during its implementation, such as fatty amides, stearic acid and its salts, ethylene bis-stearamide or fluoropolymers; antifogging agents; anti-blocking agents such as silica or talc; fillers such as calcium carbonate and nanofillers such as clays; coupling agents such as silanes; crosslinking agents such as peroxides; antistatic agents; nucleating agents; pigments; dyes; plasticizers; the plasticizers and flame retardant additives such as aluminum or magnesium hydroxides.

These additives are generally used in contents of between 10 ppm and 100,000 ppm by weight relative to the weight of polyethylene or

of end-ethylene copolymer. In particular, plasticizers, flow and flame retardant additives can reach much higher amounts to 10 000 ppm.

In addition to improved productivity results, the method of the invention also presents a number of advantages including a non-exhaustive list is given below:

- implementation facilitated by simple addition of peroxides torque can be introduced in a single formulation formulation / dilution initiators;

- organic peroxides used in the context of the invention are peroxides of the same category (diperketals), thus having the same advantage of reduced production of CO2 (inert gas detrimental to the conversion of ethylene, for replacement purpose) and a higher conversion than peresters;

- lower specific fuel consumption of the first diperketal peroxide used (principal) not compromised by the addition of the second diperketal peroxide (possibly designated by the term "booster"), on the contrary, the addition of the second diperketal peroxide reduces amounts used of the two peroxides, of the order of 5 to 10% (relative to the use of only the first diperketal peroxide);

- compatibility with existing high-pressure polymerization technology, ie no adaptation hardware or autoclave process or tubular current is required for the implementation of the method according to the invention.

Detailed Description of the Invention

The polymerization or copolymerization is performed at a pressure ranging from 500-3500 bar, preferably from 500 to 3000 bar, preferably 1200 to 3000 bar, even more preferably of 1200 to 2600 bar.

The high pressure polymerization is generally carried out in an autoclave or tubular reactor. The reaction temperature is generally between 100 ° C and 330 ° C, preferably between 120 ° C and 300 ° C and more preferably between 140 ° C and 200 ° C.

When a tubular reactor is used, the introduction of the mixture of ethylene and or optional comonomers is preferably carried out in the tubular reactor head. Preferably, the initiator or initiator mixture is injected with a high pressure pump into the reactor head, after

the point of introduction of the ethylene or of the mixture and optional comonomers.

The mixture of ethylene and or optional comonomers can be injected in at least one other point in the reactor, this injection may be itself followed by a further injection of initiator or mixture of initiators then speaks of multipoint injection technology. When the multi-injection technique is used, the mixture is preferably injected such that the weight ratio of the mixture injected into the reactor entry to all of the injected mixture is between 10 and 90%.

Other methods of polymerization or high pressure copolymerization tubular usable are for example those described in US2006 / 0149004 A1 or US2007 / 0032614 A1.

One can also use an autoclave reactor for carrying out the high pressure radical polymerization.

An autoclave reactor generally consists of a cylindrical reactor in which is placed a stirrer. The reactor can be separated into several zones interconnected in series. Advantageously, the residence time in the reactor is between 30 and 120 seconds. Preferably the ratio length / diameter of the reactor is between 3 and 25. The only ethylene and the optional comonomer are injected into the first zone of the reactor at a temperature between 50 and 120 ° C. An initiator is also injected into the first reaction zone when the reaction zone reaches a temperature between 150 and 200 ° C. During the reaction the temperature may be between 150 and 320 ° C, since the reaction is exothermic. If the reactor is a multi-zone reactor, the flow of ethylene and optional comonomers unreacted and the formed polymer then pass into the following reaction zones. In each reaction zone, ethylene, optional comonomers and initiators can be injected at an initiation temperature of between 140 and 200 ° C. The temperature zones after the initiation is between 140 and 320 ° C. The reactor pressure ranges from 500 to 3500 bar, preferably from 500 to 3000 bar, preferably 1200 to 3000 bar, and more preferably of 1200 to 2600 bars.

The invention is illustrated by examples and not limiting experiments that follow.

In the following, note that in experiments and tests following two cases are distinguished drastically. First, the case of a mono-peroxide boot system and associated binary mixture of peroxides according to the invention and secondly, the case of a ternary mixture of peroxides, because of their temperature separate initiation leading to performance and in particular to different specific consumption.

The initiation systems incorporating ternary highly reactive peroxides such as tert-butyl peroxypivalate (known under the commercial form Luperox ® January 1 M75) and tert-butyl peroxy-2-ethylhexanoate (known commercially as Luperox ® 26) are thermally decomposed at a lower temperature that the only type of diperketals initiation systems of the invention.

It is known to the skilled in the art that the use of such reactive peroxides comes at the cost of higher peroxide consumption, even if their use also allows to achieve grades of resins / polymers different. Therefore, the performance of individual diperketals initiator systems tested at an initial temperature near 180 ° C on the one hand - Examples 1 to 4 - and peresters + perkétals tested at a temperature close to 145 ° C on the other hand - Examples 5 8 - can not be compared with each other crosswise but only under the same experimental conditions.

Thus, to be in accordance with the invention, results in the context of a binary system (peroxides), with initial temperature ~ 180 ° C and P = 1800 bars, must be:

- maximum temperature attained: it must (to be consistent with the invention) be greater than 250 ° C;

- time of reaching the maximum temperature to be consistent with the invention, less than or equal to 21 s;

- Conversion: to conform to the invention, greater than 10%;

- Specific consumption of peroxide (s) pure (s) overall to be in accordance with the invention, less than 0.18 g of peroxide (s) consumed / kg produced resin.

As part of a ternary system (peroxides) positioned at an initial temperature of 145 ° C, 1800 bar, the results should be the following:

- maximum temperature attained: it must (to be consistent with the invention) be greater than 235 ° C;

- time of reaching the maximum temperature to be consistent with the invention, less than 19 s;

- Conversion: to conform to the invention, more than 1 1%; - Specific consumption of peroxide (s) pure (s) overall to be in accordance with the invention, less than 0.32 g / kg.

For brevity and simplicity, it should be noted that only a part of the experiments and tests conducted by the applicant are shown below. However, it is understood that the applicant conducted all the experiments and tests enabling it to define the invention as claimed in its generality and in its details and keeps its data available, if needed.

Example 1:

Example 1 provides a comparison of the ethylene polymerization kinetics with either 2,2- (di-tert-amylperoxy) propane or 2,2- (di-tert-amylperoxy) butane (Luperox ® 520M50).

In a stirred reactor high autoclave type pressure 435 ml (milliliter), ethylene is fed until a pressure of 1800 bar. The reactor wall temperature is set at 180 ° C using heating rods placed in the reactor walls. The stirring was 1000 r / min (revolutions per minute).

The temperature of the reaction medium in the reactor is measured by two thermocouples.

The various flows (peroxide + + propanaldehyde heptane) are mixed upstream of the reactor at low temperature (25 ° C) so as not to initiate the reaction prior to entry into the precharged reactor with ethylene.

2,2- (di-tert-amylperoxy) propane (4.3 mg corresponding to a concentration of 2.26 molar ppm relative to the content of total reactor comprising an ethylene load 216,62g) or the 2,2- (di-tert-amylperoxy) butane (Luperox ® 520M50) (4.6 mg or 2.26 ppm molar) was diluted in heptane and propanaldehyde (0.654 grams of heptane solvent diluent injection and 0.502 gram of propanaldehyde, transfer agent) and injected into the reactor using a high pressure pump. The polymerization is initiated from the injection of the peroxide at an initial temperature of 180 ° C (initiation temperature).

The experiment time is 20 minutes for the uncooled reactor.

On leaving the reactor the mixture of ethylene / polyethylene is expanded directly to three bars and the polymer is separated from the ethylene unreacted by passage through a recovery pot.

The amount of polymer recovered after polymerization is determined by weighing thereby express conversion (grams of resin produced per grams of monomer (s) engaged (s)) and specific consumption of peroxide (s).

In this example, the following results were recorded.

For 2,2- (di-tert-amylperoxy) propane (diluted to 50% by weight in isododecane), one obtains:

maximum temperature: 284 ° C

time to reach the maximum temperature: 26 s (seconds)

Conversion : 15,84%

The specific consumption or "CS" is expressed in pure peroxide in g / kg (gram per kilogram) of LDPE ( "Low Density PolyEthylene") obtained = 0.126 g / kg PE.

Quantity polyethylene LDPE low density produced: 34.5 g

For 2,2- (di-tert-amyl peroxy) butane diluted to 50% by weight in isododecane (Luperox ® 520M50), one obtains:

maximum temperature: 256 ° C

time to reach the maximum temperature: 15 s

Conversion : 1 1 ,95%

CS = 0,176g/kg

LDPE produced Quantity: 26.05 g

According to this Example 1, an equimolar dosage of each diperketals Luperox ® 520M50 and 2,2- (di-tert-amylperoxy) propane and therefore equitable (active oxygen) leads to find a higher conversion and a lower specific fuel consumption when the 2,2- (di-tert-amylperoxy) propane is used in place of Luperox ® 520M50.

However the kinetics of reaction with 2,2- (di-tert-amylperoxy) propane is much slower as indicated by the time T is reached m is X which is increased over 40%, which in industrial application tube or autoclave would be extremely penalizing.

Example 2:

This example is according to the invention.

In this example, it is to test a mixture of 2,2- (di-tert-amylperoxy) butane (Luperox ® 520M50) and 2,2- (di-tert-amylperoxy) propane.

The procedure described in Example 1 is reproduced with 2,2- (di-tert-amylperoxy) butane (Luperox ® 520M50) except that replaces a proportion of about 30 mol% of the peroxide of 2 , 2- (di-tert-amylperoxy) propane.

More specifically, 1, 59 ppm (parts per million) molar Luperox ® 520M50, 0.7 ppm molar diperketal 2,2- (di-tert-amylperoxy) propane (molar ppm expressed as pure peroxide for both perkétals ) were mixed, 3.2 mg of Luperox ® 520M50 and 1, 3 mg of 2,2- (di-tertamylperoxy) -propane.

The results observed are:

maximum temperature: 260 ° C

time to reach the maximum temperature: 19 s

Conversion : 13,13%

CS = 0,159g/kg

LDPE produced Quantity: 28.45 g

The substitution of about 30 mole% Luperox ® 520M50 (calculated as pure) by 2,2 diperketal (di-tert-amylperoxy) -propane (calculated as pure) allows to increase the conversion by Luperox ® 520M50 of about 2% while achieving the T my x remains fast, which allows for improved production of approximately 9% (28.45 g instead of 26.05 g).

The association Luperox ® 520 / 2,2- (di-tert-amylperoxy) -propane allows both higher conversion and a lower specific consumption of about 10% to that of Luperox ® 520M50 alone, without significantly delaying the Highest peak exotherm as observed with diperketal 2,2- (di-tert-amylperoxy) propane alone.

Example 3:

This example is according to the invention.

In this example, it is to test a binary mixture with 2,2 perkétal (di-tert-amylperoxy) butane (Luperox ® 520M50) and a di-perkétal 2,2-di (tert-butylperoxy) -butane (Luperox ® 220M50).

This example highlights in particular the fact that all structural perkétals (I) and HTL ( "Half Life Temperature" or temperature half-life T) to one (1) minute near Luperox ® 520M50 are no 'as good as "boosters" of Luperox ® 520M50 that diperketal 2,2- (di-tert-amyl peroxy) propane in particular, although the effect "boost" is actually present.

The procedure described in Example 1 is reproduced with 2,2- (di-tert-amylperoxy) butane (Luperox ® 520M50) except that replaces a proportion of the peroxide 2,2-di (tert butylperoxy) butane (Luperox ® 220M50).

More specifically, 1, 52 molar ppm of Luperox ® 520M50 and 0.66 molar ppm of Luperox ® 220M50 are mixed to form a homogeneous whole.

The observed results are presented below:

maximum temperature: 261 ° C

Time reaching the maximum temperature: 21 s

Conversion : 12,1 %

CS = 0,163 g/kg

Quantity LDPE produced 26.3 g

Example 4:

This peroxide mixture of example is not according to the invention. In this example, it is testing a binary mixture with the perester tert-butylperoxy-3,5,5-trimethylhexanoate or Luperox ® 270 (in combination with Luperox ® 520M50) bad "Booster" despite HLT to 1 minute equivalent to that of 2,2 diperketal (di-tert-amylperoxy) propane 165 ° C.

The procedure described in Example 1 is reproduced with 2,2- (di-tert-amylperoxy) butane (Luperox ® 520M50) except that replaces a higher molar proportion as in Example 3 (approximately 47 mol%) of the peroxide Luperox ® 520M50, by tert-butylperoxy-3,5,5-trimethylhexanoate (Luperox ® 270), because of the peroxidic monofonctionalité of Luperox ® 270.

More specifically, 1, 49 molar ppm of Luperox ® 520M50 and 1, 34 molar ppm of Luperox ® 270 are mixed to form a homogeneous whole.

This summary shows in particular that, despite the high proportion of peroxide tert-butylperoxy-3,5,5-trimethylhexanoate (Luperox ® 270), the

maximum temperature, the conversion and the specific consumption with deteriorated compared to the mixture at 30% of 2,2- (di-tert-amylperoxy) propane in 2,2- (di-tert-amylperoxy) butane (Luperox ® 520M50) of example 2.

The observed results are noted below:

maximum temperature: 255 ° C

time to reach the maximum temperature: 19 s

Conversion : 1 1 ,92%

CS = 0,209 g/kg

LDPE produced amount: 26 g

Example 5:

The peroxide blend of example is not according to the invention.

In this example, it comes to the production of LDPE as described in Example 1 reproduced a cocktail / ternary mixture of peresters Luperox ® 1 1 M75 / Luperox ® 26 / Luperox ® 270 (t-butyl peroxypivalate / tert-butyl peroxy-2-ethylhexanoate / tert-butyl peroxy-3,5,5-trimethylhexanoate) in the respective molar ratio referred * 20/56/24 ( * expressed as tert-butyl peroxypivalate pure), two global concentrations peroxides, one to achieve T my x around 240 ° C, the other to reach Tmax of around 250 ° C, with a firing temperature of 145 ° C.

The tests were conducted on the same batch reactor as in Example 1, charged with ethylene to 1800 bar but regulated to the initiation temperature of 145 ° C instead of 180 ° C due to the presence of reactive peresters Luperox ® January 1 M75 (tert-butyl peroxypivalate was diluted to 75% in isododecane) and Luperox ® 26.

Results (event with Tmax of around 240 ° C, molar ratio 19/57/23 as defined at the beginning of the example) observed are as follows:

Total weight 78.36 ppm (pure peroxide)

maximum temperature: 239 ° C

Time reaching the maximum temperature: 13,5s

Conversion : 1 1 %

overall CS pure peroxides = 0.678 g / kg

Quantity LDPE produced 24.5 g

The results (case T with my x around 250 ° C molar ratio 20/56/24 as defined at the beginning of the example) observed are as follows:

Total weight 126.18 ppm (pure peroxides committed)

maximum temperature: 249 ° C

Time reaching the maximum temperature: 14,7s

Conversion : 12,29%

overall CS pure peroxides = 0.967 g / kg

Quantity LDPE produced 27.7 g

These polymerizations show breaches t my x fast less than 15 seconds conventional conversions for this equipment and this molar composition 20/56/24 ternary peroxide, but very high specific consumption.

Example 6:

This peroxide mixture of example is not according to the invention.

In this example, it comes to the production of LDPE as described in Example 1 but with a cocktail / ternary mixture of peresters and diperketal, either Luperox ® 1 1 M75 / Luperox ® 26 / Luperox ® 520M50 (tert-butyl peroxypivalate / tert-butyl peroxy-2-ethylhexanoate / 2,2- (di-tert-amyl) butane) in the target molar ratio of around 23 (neat) / 65/12 (pure diperketal), two overall concentrations of peroxides, for achieving a Tmax of around 240 ° C, the other to reach Tmax of around 250 ° C, with a firing temperature of 145 ° C.

Results (event with Tmax of around 240 ° C molar ratio 22/66/12 as defined at the beginning of the example) observed are as follows:

Total weight 45.88 ppm (pure peroxide committed)

maximum temperature: 240 ° C

time to reach the maximum temperature: 16s

Conversion : 14,10%

overall CS pure peroxides = 0.325 g / kg

LDPE produced amount: 31, 7 g

Results (event with Tmax of around 250 ° C molar ratio 23/65/12 as defined at the beginning of the example) observed are as follows:

Total weight 77.91 ppm (pure peroxides committed)

maximum temperature: 254 ° C

Time reaching the maximum temperature: 13,5s

Conversion : 14,91 %

overall CS pure peroxides = 0.523 g / kg

Quantity LDPE produced 33.5 g

These polymerizations made with peroxide ternary mixture having seen its high temperature peroxide Luperox ® 270 replaced by the diperketal Luperox ® 520 still show damage t my short x of about 15 seconds, but improved conversions for specific consumption virtually divided by 2.

Example 7:

This peroxide mixture of example is not according to the invention. In this example, it comes to the production of LDPE as described in Example 1 but with a cocktail / ternary mixture of peresters and diperketal, either Luperox ® 1 1 M75 / Luperox ® 26 / diperketal 2 2- (di-tert-amylperoxy) propane in a molar ratio 23 (neat) / 65/12 (expressed as pure diperketal) to two global concentrations of peroxides, for achieving a T my x around 240 ° C, the other to achieve T my x around 250 ° C, with a firing temperature of 145 ° C

Results (event with Tmax of around 240 ° C molar ratio 23/65/12 as defined at the beginning of the example) observed are as follows:

Total weight ppm 31 51 (pure peroxide committed)

maximum temperature: 238 ° C

time to reach the maximum temperature: 22,7s

Conversion : 13,44%

overall CS pure peroxides = 0.234 g / kg

Quantity LDPE produced: 30.2 g

Results (event with Tmax of around 250 ° C molar ratio 23/65/12 as defined at the beginning of the example) observed are as follows:

Total weight ppm 41 23 (pure peroxides committed)

maximum temperature: 246 ° C

time to reach the maximum temperature: 20,5s

Conversion : 14,50%

overall CS pure peroxides = 0.284 g / kg

Quantity LDPE produced: 32.5 g

These polymerizations carried out with a peroxidic mixture wherein the high temperature peroxide Luperox ® 270 is replaced by the 2,2 diperketal (di-tert-amylperoxy) -propane still show T I x at the same level but with a delay of at least five seconds compared to the synthesis of example 5 or with Luperox ® 520 of example 6, despite a good response as seen by the conversion rates comparable to those obtained with Luperox ® 520 (of example 6) and specific consumption even improved compared to those of example 6.

The diperketals of the invention allow higher conversions, especially compared to the perester Luperox ® 270, but all diperketals do not react as quickly. Thus, the Luperox ® 520 is much faster than diperketal 2,2- (di-tert-amylperoxy) -propane despite a molecular structure and a decomposition temperature very close HLT 1 minute.

Example 8:

The peroxide blend of example is not according to the invention.

In this example, it comes to the production of LDPE as described in Example 1 but with a cocktail / ternary mixture of peresters and diperketal, either Luperox ® 1 1 M75 / Luperox ® 26 / Luperox ® 220M50 in the molar ratio 23 (neat) / 64/13 (pure diperketal) to two global concentrations of peroxides, for achieving a T my x around 240 ° C, the other to reach Tmax around 250 ° C, with a firing temperature of 145 ° C)

Results (event with Tmax of around 240 ° C molar ratio 23/64/13 as defined at the beginning of the example) observed are as follows:

Total weight ppm 41 77 (pure peroxide committed)

maximum temperature: 244 ° C

time to reach the maximum temperature: 19,2s

Conversion : 13,81 %

overall CS pure peroxides = 0,353g / kg

LDPE produced amount: 31, 1 g

Results (event with Tmax of around 250 ° C molar ratio 23/64/13 as defined at the beginning of the example) observed are as follows:

Total weight 58.14 ppm (pure peroxides committed)

Maximum temperature reached 259 ° C

time to reach the maximum temperature: 18,5s

Conversion : 15,71 %

overall CS pure peroxides = 0.434 g / kg

Quantity LDPE produced: 35.4 g

These polymerizations made with peroxide ternary mixture in which the high temperature peroxide Luperox ® 270 is replaced by the diperketal Luperox ® 220M50 again show the superiority conversion and specific consumption of the use of a diperketal but as for example 7, the time to reach of T my x remains longer than when the Luperox ® 520M50 is selected as diperketal the ternary mixture (example 6), whereas the molecular structure and HLT 1 minute from Luperox ® 220M50 are there still close to those of Luperox ® 520M50.

From the examples 5, 6, 7 it appears that the 2,2 diperketalperketal (di-tert-amyl peroxy) propane does not replace the Luperox ® 270 usual because of excessive movement of the T my x that from 15 seconds to over 20 seconds despite an overall reduced specific consumption of about 65%. Only Luperox ® 520M50 allows to substitute the perester Luperox ® 270 with a profit on both conversion and a still considerable reduction of about 50% of the specific consumption of the ternary peroxides cocktail without degrading kinetics. But applicant and shown by Example 7 that the use of 2,2 diperketalperketal (di-tert-amylperoxy) propane as the sole diperketal for high reaction temperature range 140-290 ° C is not possible and the invention should preferably comprise a majority of Luperox ® 520M50 to enable maximum productivity (high conversion in a short reaction time).

Example 9:

peroxide blend of example according to the invention used in a cocktail initiators.

Polymerization of LDPE was carried out as described in Example 1, but on the basis of a cocktail initiator Luperox ® 1 1 M75 / Luperox ® 26 / Luperox ® 520M50 (tert-butyl peroxypivalate / tert-butyl peroxy-2-ethylhexanoate / diperketal 2,2- (di-tert-amyl peroxy) butane) to compare it to a polymerization carried out on the same basis of initiators but wherein a portion of Luperox ® 520M50 was replaced with 2,2- (di-tert-amylperoxy) -propane

Example 9a:

For reference in this example, the production of LDPE was carried out following the procedure described in Example 1, with a cocktail / ternary mixture of peresters and diperketal, precisely Luperox ® 1 1 M75 / Luperox ® 26 / Luperox ® 520M50 (tert-butyl peroxypivalate / tert-butyl peroxy-2-ethylhexanoate / diperketal 2,2- (di-tert-amyl peroxy) butane) in the molar ratio 23.1 (neat) / 65.1 / 1 1, 8 (expressed pure diperketal) at a total concentration of peroxides to achieve T my x around 250 ° C, with a firing temperature of 145 ° C.

Polymerization Reference Example 9:

The results observed are:

Total weight 48.4 ppm (pure peroxides committed)

maximum temperature: 250 ° C

Time reaching the maximum temperature: 14s

Conversion : 15,32%

overall CS pure peroxides = 0.316 g / kg

Quantity LDPE produced: 34.5 g

This polymerization was then compared to that achieved with peroxides cocktail described in the following example:

Example 9b:

Polymerization according to the invention Example 9: polymerization with peroxides cocktail as for the reference example 9, but for which a molar thirds of perketal 2,2- (di-tert-amyl peroxy) butane was replaced by a molar thirds deperketal 2,2- (di-tert-amylperoxy) -propane:

The procedure described in Example 1 is repeated with the following composition of the cocktail injected:

Luperox® 1 1 M75 / Luperox® 26 / Luperox® 520M50 (tert-butyl peroxypivalate / tert-butyl peroxy-2-ethylhexanoate / 2,2-(di-tert-amylperoxy)butane)/ 2,2-(di-tert-amylperoxy)propane) dans le rapport molaire 23 (pur) / 65,4 / 8 /3,6

respectively, the last two peroxides perkétals di being expressed in pure then qu'engagés form of dilution at 50% in iso-dodecane.

The results observed are:

Total weight ppm 51 55 (pure peroxides committed)

maximum temperature: 251 ° C

Time reaching the maximum temperature: 13,5s

Conversion : 16,83%

overall CS pure peroxides = 0.306 g / kg

Quantity LDPE produced 37.9 g

Example 9b shows that the use of 2,2- (di-tert-amylperoxy) propane to replace a molar thirds of 2,2- (di-tert-amyl peroxy) butane in an initiated polymerization a ternary mixture consisting of peresters and a peroxidic initiator diperketal high productivity such as 2,2- (di-tert-amyl peroxy) -butane) can increase the conversion of more than, 1, 5%, and with a conserved kinetics, while example 7 shows that the total substitution of 2,2- (di-tert-amyl peroxy) -butane by 2,2- (di-tert-amylperoxy) propane leads to a lengthening of the reaction unacceptable polymerization production. Example 9b thus illustrates the advantage of introducing a non perketal majority proportion of 2,2- (di-tert-amylperoxy) -propane with 2,2 diperketal (di-tert-amyl peroxy) butane in a cocktail of perester initiators and diperketal components.

Example 9c:

Polymerization according to the invention Example 9: polymerization cocktail peroxides as for the reference example 9, but for which 12 mol% to about perketal 2,2- (di-tert-amyl peroxy) butane was replaced by 12 mol% to about diperketal 2,2- (di-tert-amylperoxy) -propane:

The procedure described in Example 1 is repeated with the following cocktail: Luperox ® 1 1 / Luperox ® 26 / diperketal 2,2- (di-tert-amyl peroxy) butane / diperketal 2,2- (di-tert-amylperoxy ) propane in a molar ratio 22.8 (neat) / 64.7 / 1 1/1, 5 respectively, the last two peroxides perkétals di being expressed in pure then qu'engagés form of dilution at 50% in the iso-dodecane.

The results observed are

Total weight 60.23 ppm (pure peroxides committed)

maximum temperature: 249 ° C

Time reaching the maximum temperature: 14s

Conversion : 15,81 %

overall CS pure peroxides = 0.31 1 g / kg

Quantity LDPE produced: 35.6 g

Example 9c again shows the advantage of introducing a non diperketal majority proportion of 2,2- (di-tert-amylperoxy) -propane with 2,2 diperketal (di-tert-amyl peroxy) butane in a cocktail perester initiators and diperketal components.

Although the gain in conversion and production of resin is lower than that shown by Example 9b, Example 9c with 12% instead of about 30 mol% of 2,2- (di-tert-amylperoxy) - propane used together with 2,2- (di-tert-amyl peroxy) -butane still allows an order of the conversion gain of a half percent conversion.

CLAIMS

1. A method of manufacture of polyethylene or copolymer of ethylene, comprising a step of polymerization or radical copolymerization of ethylene in the presence:

- a first peroxide polymerization initiator selected from peroxides diperketals compounds of formula:

where Ri, R2, R3, R6, R7 and Rs consist of alkyl groups C1 -C10 substituted or unsubstituted linear, branched or cyclic,

- a second initiator, different from said first initiator, also consisting of a diperketal peroxide of formula (I).

2. Method according to claim 1, characterized in that the

Temperature half-life to one minute of said first initiator is between 140 ° C and 180 ° C, preferably between 150 ° C and 170 ° C, and more preferably between 155 ° C and 165 ° C.

3. The method of claim 1 or 2, characterized in that the

Temperature half-life to one minute of said second initiator is between 150 ° C and 185 ° C, preferably between 155 ° C and 175 ° C, and more preferably between 160 ° C and 170 ° C.

4. A method according to any one of the preceding claims, characterized in that the step of polymerization or radical copolymerization is conducted at a pressure between 500 and 3500 bar, preferably between 1200 and 3000 bar, still preferably 1200 to 2600 bar.

5. A method according to any one of the preceding claims, characterized in that the step of polymerization or radical copolymerization is conducted at a temperature between 100 ° C and 330 ° C, preferably between 120 ° C and 300 ° C and even more preferably between 140 ° C and 200 ° C.

6. A method according to any one of the preceding claims, characterized in that the group R 4 or R of the first initiator is different from the corresponding group, or R 4 or R of the second initiator, a single carbon.

7. A method according to any one of the preceding claims, characterized in that the groups R 4 and Rs are alkyl groups C 1 -C 6.

8. A method according to any one of the preceding claims, characterized in that the groups R2, R3, R6 and R 7 of the above two initiators consist each methyl, preferably also the group R 4 .

9. A method according to any one of the preceding claims, characterized in that the groups R and R of said two initiators each consist of an alkyl group C2-C5, preferably C2-C4.

10. A method according to any preceding claim characterized in that the R5 group of the aforesaid two initiators is alkyl C1 -C2.

January 1. A method according to any one of the preceding claims, characterized in that the first initiator is 2,2-di (t-amyl peroxy) butane.

12. A method according to any one of the preceding claims, characterized in that the second initiator is 2,2-di (t-amylperoxy) propane.

13. A method according to any one of the preceding claims, characterized in that the mixture of the two peroxides diperketals has a part of the second initiator of between 2% and 50% molar, preferably between 10% and 40 mol%, even more preferably between 15 and 35 mol%.

14. A method according to any preceding claim characterized in that the polymerization or copolymerization is carried out in the further presence of one or more initiator (s) peroxide (s) Additional (s).

15. A method according to any preceding claim characterized in that the polymerization or copolymerization is performed in the presence of at least one additive selected from the group consisting of: antioxidants; UV protection agents; implementing agents; antifogging agents; anti-blocking agents; the charges ; coupling agents; crosslinking agents; antistatic agents; nucleating agents; pigments; dyes; plasticizers; the plasticizers and flame retardant additives.