DE1520655C - Process for the polymerization of ethylene - Google Patents

Description

Since then it has been found that ethylene under high pressure forms solid, high molecular weight polymers polymerized as described in U.S. Pat. No. 2,153,553 is continued from Methods have been sought to help with the high pressure processes, particularly those that are tubular Use reaction vessels. control conditions applied to polymers or Copolymers with optimal physical and chemical properties with increased conversions to create. In particular, in the case of high pressure polymerization with tubular reaction vessels, possibilities have been sought to increase conversion, facilitate operation, and reduce the cost of the peroxide initiator.

As has been said, it is known to polymerize ethylene by subjecting it to high pressures, usually above 500 kg / cm ² , ie 1054 up to 3164 kg / cm ² or higher, such as 7030 kg / cm ² . In polymerization reactions under these high pressures is typically oxygen or a peroxide, ie, a free radical initiator used at temperatures in the range of about 107 to about 316 ⁰ C. ' The polymerization reaction of ethylene in high pressure processes of this type is highly exothermic, and methods must be used to avoid an unacceptable rise in the reaction temperature, which can cause the reactions to get out of control and cause explosions. In processes in which a long tubular reaction vessel is used for the polymerization, the temperature can be controlled by dissipating the heat released by heat transfer to a medium which circulates in a jacket surrounding the reaction vessel. Diluents can also be used to aid in heat transfer and to absorb some of the heat of reaction, so long as they are weak chain transfer agents, e.g. B. water or benzene.

It is known that especially in processes in which long tubular reaction vessels are used there are irregular, uncontrolled temperature fluctuations in the polymerization reactions of ethylene affect the physical properties of the polymer directly in the reaction zone. Therefore, various schemes have been proposed in the art to avoid a reaction to cause large fluctuations in the temperature curve (profile) of the reaction zone. The temperature profile can be determined by simply taking the readings from all of the thermocouples that are along the reaction zone are used, records. So when ethylene and peroxide initiator occurs in a tube • are introduced and polymerization begins, usually at a temperature above 107 ° C, a temperature maximum due to the exothermic reaction and the initially high concentration of the initiator in the reaction zone which affects the conversion and properties of the polymer. The properties of the polymer are influenced when such a maximum is uncontrolled irregular Maxima or minima follow along the temperature profile of the reaction zone.

In a conventional continuous process for the polymerization of ethylene in a long tubular reaction zone at high pressures, the initiator and the monomer are introduced at or near the inlet opening of the reaction vessels and then subjected to suitable polymerization conditions. In such processes, for example, when using oxygen as the initiator, conversions are usually below about 10%. The solid polyethylene commonly produced has a density of 0.910 to 0.92 g / cm ³ . The properties of the polymer, e.g. B. the molecular weight,

ίο can through the introduction of a common chain transfer agent be modified. When the properties of polyethylene are more fundamentally changed are to be, a comonomer is usually introduced into the ethylene feed. When if this is done, a polyethylene is obtained which contains branches introduced along the polymer chain and has a reduced density. .

In conventional ethylene polymerization reactions in which a long tubular reaction vessel is used, it being immaterial, as mentioned, whether it is a homo- or copolymerization, the usual pressures preferred for such processes are in the order of magnitude of above about 1054 to about 4218 kg / cm ² and temperatures of about

107 to about 302 ^° C. The particular size of the pipe used can vary considerably in length and diameter. However, it is common to use tubular reaction vessels with a length to diameter ratio greater than about 100: 1 and in some cases as much as 20,000: 1 that can withstand the high pressures applied.

The object of the invention is now to develop a method according to which homo- and copolymers of ethylene with optimal physical properties can be obtained, which allows the manufacture of a greater variety of products and of a uniform one Rate of change of temperature in the tubular used for ethylene polymerization High pressure polymerization systems leads. Under a steady rate of change The temperature is not just meant to mean that the temperature is at a controlled rate increases between the initial temperature and the maximum reaction temperature, but also, that the temperature profile has controlled maxima and minima.

A process has now been found for the polymerization of ethylene, alone or together with other ethylenically unsaturated monomers, in tubular reaction zones at pressures above 1054kg'cm ² and temperatures from 107 to 316'C in the presence of mixtures of several free radical-forming catalysts the aforementioned aims are reached when the polymerization in the presence of a Peroxydmischung is executed, a peroxide of the type 1, the half-life is at temperatures from 43.3 to 79.4 ^f C in 10 hours, a peroxide of type II, whose half-life is 10 hours at a temperature of 79.4 to 12PC, and a type III peroxide whose half-life is at one temperature

from 121 to 160 ° C for 10 hours contains.

The half-life of a peroxide is defined as

the time it takes to concentrate the

■ Peroxide at a certain temperature on the

3 4

Half of the original concentration to be reduced to the reaction as a result of the exothermic reaction. a maximum and then gradually falls as a result of the peroxide mixture, which creates heat dissipation at a single point, whereby the reaction can essentially be introduced into the reaction vessel, is terminated. It has been found that by a substantially guided free radical formation 5 appropriate control of the initiator mixture, the Gebei rising temperatures and leads to a desired reaction zone temperature profile determined uniform rate of change can be the tem-, so that products with optimal physiperatur. It goes without saying that the prior art kaiischen characteristics are obtained, .also teaches that the pressure in a reaction vessel. In the known processes, it was essential to periodically be vented into a trap or high-pressure container if a high-temperature initiator such as the one is used can, for example, a type III initiator. to separate a nenten .. If such a process wanted to achieve high conversion, this is applied at lower, but the speed of injecting changes. However, a large amount of ethylene through the reaction vessel as well as an amount of peroxide was required to achieve the required high speed at which the initiator mixture had to be injected at the rate of free radical formation. To get the injection at a low temperature. Therefore, if the Tem multicomponent peroxide mixture rose to such a temperature, the rate of the Radi system would be so high that the temperature rose above the concentration of the initiators at the injection decomposition point of the ethylene. This cause the pivot point. According to the invention, this overcomes this problem. From British patent 870 043 it is true that a smaller amount of a high temperature high pressure polymerization of ethylene in tubular .peroxyds, ie a type III initiator, is applied using deformed reaction vessels and a controlled amount of a mixture of several, free radical-forming peroxide initiators of type II, known as half-life catalysts. In this method, is 25 times of 10 hours at 79.4 to 12TC has einjedoch only one Peroxydkatalysätor used out, this peroxide type It delivers a half-life of 10 hours at about required amount of free radicals at the lower 121 ° C (ie a temperature set according to the invention. Therefore, when the temperature rises, peroxide becomes of type II). The other type used in this process is type II peroxide, and the known initiator used is type III acid. Peroxide provides the required (but material which, according to the literature, results in a smaller amount of free radicals). The use of approximately 160 ^c C begins to decompose, ie, a peroxide type I allows the application must be at least this temperature be reached, an even lower initial temperature. This so that the oxygen becomes effective as an initiator. lower initial temperature is only practical by this means that in the known process it is not limited by considerations that make the kinetic chain length possible, including the ethylene at temperatures below, for example, at low temperatures. Introduce the 150 ⁰ C into the polymerization zone. By using several peroxide initiators, the better control of the temperature profit makes it possible to start the reaction at a lower temperature in the method of the invention, and to achieve a controlled temperature density than in the known method. 40 temperature rise (although not necessary equi-Another important advantage of using the moderate) in the reaction zone. Thus, three peroxides catalyst mixes are generally larger amounts of peroxide initial is that one can increase the conversion, such as the Type I required for the initial temperatures, by increasing the maximum temperature and increasing the (since they are less effective than Types II and III) feed temperature lowers. . 45 while minor amounts of Type II and III for The process of the invention requiring the higher polymerization temperatures has been found to have increased conversions of ethylene. will.

in solid polymer, for example over 10%, obtained in the process of the invention in which a th. Conversions from 12 to multicomponent peroxide initiator used, 13% and higher, are easily obtained compared to 5 °, determined at a given temperature range, conversions of 5 to 8% in processes using the amount of usable initiator present in which a single peroxide initiator, How, for example, how many polymer chains at that temperature, oxygen is used. to be started. Since the degree of polymerization in the drawings which will later be described in detail for each given section shows the amount of heat released, 55 shows the amount and so the temperature rise of the reac F i g. 1 a reaction vessel temperature profile, determined against ionization participants, determines the amount, the time, usable initiator, which is present in its usable FIG if a multi-component peroxide mixture is 60 bar range. It is according to the method used in the invention, and. Invention so possible, the course of parts of the - ■. F i g. 3 reaction vessel temperature profiles, which can be set from the reaction zone temperature profile, without four attempts using alternating Ethy- that other conditions are drastically changed, oil supply temperatures and initiator concentrations are plotted below with reference to ions. . 65 F i g. 3 Changes in the course and in the position In the polymerization of ethylene in a pipe of Temperaturrhaxima by manipulation of shaped reaction vessel according to the process of Äthyleneintrittstetapßhituren und Initiatorlösung- \ invention, the reaction temperature rises from the beginning nissen described. '^;:

<· ■ ■ '. ■■ .-.

The range of initiators used should be preferably overlap one another. That means that at any given temperature range a particular type of initiator is predominantly useful; however is at the beginning of the range the previous initiator can still be used, and the next one begins at the end of the area Initiator to become useful (i.e., to decompose). Such overlaps are preferred, as they lead to advantages. The covering of free radicals generated from various peroxides prevents wide and sharp fluctuations in the concentration of free radicals in the reaction zone: this avoids sharp changes in the rate of change in temperature, which leads to the fact that a uniform temperature profile is maintained. This gives a better control of the reaction and leads to better control of the polymer properties.

By using the multi-component peroxide initiator mixture according to the method of the invention, a desired amount of free radicals is obtained cleared, beginning with the decomposition of the first Type I initiator at start-up temperatures and higher, followed by free radical formation from the initiator, of Type II on one Point before Type I is applied. then type III etc. so that a continuous supply is more active free radicals to the reaction is created.

In the following "the drawings are more detailed explained. .

.. * F i g. 1 represents an aclion zone temperature profile dar; this is obtained by taking readings from thermocouples taken along the length of the reaction zone are used, plots against the elapsed time, and which are determined during an experiment were, in which a four-component Pcroxydinitiator at one point or was injected close to the inlet opening of the pipe. It became ethylene when entering the reaction vessel introduced at a temperature of about 152 C and a pressure of 2330 kgcnr. The initiator mixture consisted of lauroyl hydroxide (type 1). tert-Butylpcroxusobutvrat (also type 1). tc.rt.-But \ lperacetat (Type II) and bi-tert.-butyl peroxide (type Uli in a molar ratio of 2.6 b / w. 1.56: 1.0 ".0.915. From the drawing it can be seen that the curve is evenly dependent on the preheating temperature of 152 C to a peak temperature of about 288 C and then gradually to an exit temperature drops from about 21.VC. By using a multi-component peroxide initiator system, as described here, a fairly steady rise in temperature is possible, as in the drawing is shown.

F i g. Figure 2 shows the relative rate of free radical formation along the temperature profile a tubular reaction vessel. The various curves were made from values obtained from the profile of Fig. 1, and decomposition rates of the various initiators at the temperatures in question drawn. These free radical formation rates are calculated and their accuracy is subject to certain simplifying assumptions made in the calculations.

Curve A shows, for example, an estimate of the total amount of free radicals that are formed as a function of time and increasing temperatures. The following explanation is given. In a reaction of the specified type, the generation of free radicals occurs as follows:

where / = initiator concentration and R = concentration of free radicals (K _d is, as indicated, the decomposition coefficient of the initiator). The instantaneous formation of free radicals can be represented by the following differential equation:

d /

d7

1 (iRj

2 at

UR,

where t means the time and ' the speed

represents the formation of free radicals. Hence means

j- the current rate of decomposition

of the initiator at a given temperature for a known concentration. And this is, for example, from a graphic representation of the Decomposition rate constants of the initiator taken from the information on the decomposition coefficient (Kj) of initiators versus temperature contain.

The initiator concentration at any given temperature is more difficult to determine because they depend both on the initial amount that enters the reaction vessel and on the amount that goes into the reaction vessel is decomposed before the temperature in question is reached, depends. One Method to estimate the amount of undecomposed initiator at each temperature in the reaction vessel, consists in applying the following equation:

(at constant temperature) over very short time intervals (e.g. about 0.2 seconds) so that average values of K ₁ (which changes with temperature) can be used. By using this method and starting at the front end of the reaction vessel, the amount of decomposed initiator can be estimated at each time interval.

If the reaction vessel temperature profile of FIG. 1 in small and equal time intervals (0.2 seconds) and the analysis proceeds from the beginning to the end of the reaction zone, the following expression represents the concentration tration at any point in the reaction vessel for any particular initiator:

fco where. / = Initiator con / eiHration at any point. / "= Initiator concentration at the reaction vessel inlet. ι - small and equal time intervals in the analysis. K - sum of all average K ₁ values. which were used in the analysis until

^(< > to your but only the time interval in question. ■ '.

This equation is an estimate of the instantaneous initiator con / entratioh and can have a

Errors of about 10 "/ ,, included. If one explains the use of varying molar the above equation in the expression ratios (two attempts) and ethylene introduction

temperatures (two attempts) to see the difference

d / f 'j _' dRf between varying molar initiator ratios

AT ^{= Λ} ~ 2 df 5 at two different inlet temperatures

to demonstrate. The initiators used were

uses, the following expression is obtained: Mixtures of types I, lauroyl peroxide and tert.-Bu-

d /. _ ,: _Kj tylperoxyisobutyrat, Type II, tert-Butylperacetat, und

~ dj ~. ~ ^ dIt) C ■ ^J Type III, di-tert-butyl peroxide. These curves show

ίο also the effect when the feed temperature

where K d is the average of the ethylene feed in question and the initiator introduction time interval and where f K _{d is} the sum of the average is varied while the same initiator _{mixture is used as the average reaction coefficient of each time interval to.} .

to the time interval in question. . In Fig. 3 represent the curves H and / temperature

It is noted that the above estimates for ethylene supply and initiator introduction apply to only a single initiator at a time of about 138 ° C, while curves F and G are and that the system door any introduction temperatures used of about 154 ° C represent. Initiator has to be analyzed and the decomposition tests, of which the reaction vessel temperature rates for each initiator were recorded in a given time interval given a profile of F, G, H and J, have to be added together, were carried out at 2320 kg / cm ² . In the case of the sen. To determine the total rate of formation curves G and /, experiments were shown to give the free radicals in the time interval. same initiator mixture used, while with the

f ' With the above explanations in mind, an experiment illustrated by curves F and H is shown further on F i g. Reference is made to 2, where curves A, different initiator mixture (ie shown with higher concentration BC D and E are shown "taken from a recording of low temperature initiators) used on semi-logarithmic paper. By comparing G and / can man

τλ · λ ι- ', uj. . <ll a I you,; . see that the maximum temperature is shifted,

The ord.nate means _A or -, _ä /, which _{if the AlhylsnmMtun} ^ _{tempemvit at the E} in

half the speed of the formation of free radical line parts of the initiator is reduced, without kale with the line which is shown as the abscissa. 30 that the initiator ratio is changed,
is equivalent. Curve δ represents the initiator. However, by comparing G and H lauroyl peroxide is represented. Curve C iert.-Butylperoxybuty- shows that when the initiator mixture is adjusted rat. Curve D terl.-butyl peracctate and curve E di- is used in order to extract the lower preheating temperature - butyl peroxide. Curve A represents, as noted above the same (ie. The initiator type / is increased at H ), the sum of the individual instantaneous 35 represents the maximum temperature approximately at the same 'initiator decomposition rates and therefore; Position can be held. Thus, referring to the above equation, it can be seen that since the percentage rate of conversion of the instantaneous formation is known to increase, firstly by increasing the maximum radicals along a tubular reaction temperature and secondly by lowering the feed vessel with the temperature shown in Fig. 1, by controlling each of these two turprofiles. It is obvious that within one or both of these factors, by appropriate use of the time interval shown for the measurement, the addition of the initiator type / conversions can be increased and free radicals for the reaction of ethylene can be increased. It has been shown that this is the case with the Ver according to curve .4 of FIG. 2 is continuous and search is the case for which temperature profiles in ^ that such a supply a desired reaction. 3 are shown.

vessel temperature profile provides .. as in F i g. 1 represents- It can be seen that the additional freedom is posed. degree, that’s the ability to set the initiator ratios So F i g. 2. As shown, varying the results can lead to both the Umanalysis of a typical temperature profile (Fig. 1) conversion and the polymer properties in order to determine the fluctuation in the rate 50 through the process and the initiator mixture after the Determine free radical generation. Which the invention can be influenced. For example peaks of the individual decomposition rates, it is known that density in general can be increased as a representation of some variation by looking at the peak and total rates. Feed temperature is reduced. Therefore, based on this analysis, a new 55 can be found, however, that by using a suitable initiator mixture to smooth out neter concentrations of initiators of type I curve A , so that they are a desired one in combination with type II and III Densification of function follows. F i g. Figure 2 also clearly shows that any initiator used can achieve higher conversions in certain temperature ranges than is particularly effective with a single peroxide initiator. Analyzes of this type constitute 6 ° would be the case.

The basis for using various types of initiators of type I are the following mixtures in order to achieve the following: 2,4-dichlorobenzoyl peroxide, caproyl peroxide, white targets with regard to operating or polymer lauroyl peroxide. tert-butyl peroxyisobutyrate to support properties. zoyl peroxide, p-chlorobenzoyl peroxide, isopropyl peroxide. 3 shows four reaction vessel temperature pro- ^{6 5 oxydicarbonate.} Acetyl peroxide, decanoyl peroxide and files F, G. H and /. the critical reaction tcrt.-butyl peroxypivalate. Illustrate usable initiators of the zone section of the pipe and in type II are z. B. tert-butyl peracetate, tert-butyl are registered in the usual manner. The profiles perbenzoat. Dicumyl peroxide, diethyl dioxide, tert.-Bu-

tyl hydroperoxide, methyl ethyl ketone peroxide, di-tert-butyl diperphthalate, Hydroxyheptyl peroxide and cyclohexanone peroxide. Usable initiators of type III are the following: p-menthane hydroperoxide, Pinane hydroperoxide, cumene hydroperoxide, di-tert-butyl peroxide and 2,5-dimethylhexane-2,5-dihydroperoxide.

In carrying out the process according to the invention, the molar ratios of the initiators which are most expedient in order to obtain a polymer with the desired properties vary to a certain extent with the pressure. It has been found, for example, that for pressures of 1054 to 2812 kg / cm ² the molar ratios of the initiators of types I, II and III can vary considerably, namely from more than 0 to 8 for type I and from more than 0 to 3 for Type III, with Type II being used arbitrarily as a reference point for the molar ratios of Types I and III.

The choice of initiators and types can of course vary. So can two or more initiators are used, belonging to Type I or of Type II, etc. If for example a type II initiator whose 10 hour half-life is close to the end of the temperature range width of Type II is selected, i.e. close to 121 ° C, it will be seen that the molar ratio of the type III initiator used can be much smaller than if a type II initiator is used, its 10 hour half-life of the temperature range of type I of up to 79.4 ° C is closer.

The total concentration of initiators of types I, II and III can vary according to the operating pressures and temperatures. Thus, for polymerizations carried out at minimum pressures of about 1054 kg / cm ² , up to about 500 parts per million on a molar basis of ethylene can be used, while for pressures of about 2812 kg / cm ² the concentration is conveniently down to about 5 parts per million on a molar basis of ethylene. While the ranges of total initiator concentration given herein are preferred, they can of course be varied and the resulting polymers still have highly desirable properties. The process of the invention can be carried out at pressures of 1054 to 4218 kg / cm ² or higher.

As stated above, one or more initiators of a single type, e.g. B. des Type I or II, used in combination with the other types, so that actually one Multi-component initiator system, which consists of a total of 3, 4 or 5 initiators, can be used can. ■

It has been found that as solvents for the initiators' hydrocarbons, e.g. * B. paraffinic Hydrocarbons, such as pentane, hexane, heptane or cyclohexane, or aromatic hydrocarbons, such as benzene and toluene are suitable. Preferred solvents for the initiators are mixtures of one or more paraffinic hydrocarbons with an aromatic one Hydrocarbon. By combining a paraffinic and an aromatic one Solvent, the solubility of the solid peroxides is improved without them solidifying when they can be used at elevated pressures. It has been found that mixtures of 35 to 50% hexane and 50 to 65 percent benzene is particularly desirable. Preferably the method according to. the Invention carried out with a solution of the initiators in hydrocarbons, as such a solution that which contains three components, by a suitable pump at a single point in the reaction vessel can be introduced.

The concentration of the initiators in the solvent is not critical and various concentrations can be used. Exemplary Initiator mixtures in solvents, such as, for example, a 50:50 mixture of benzene and U Hexane, are in percent by weight of the solvent 18: 3: 2 for the system lauroyl peroxide to tert-butyl peracetate to di-tert-butyl peroxide, a ratio of 12: 3: 2 of the same components and a Ratio of 8: 5: 3: 2 for a four-component peroxide system consisting of lauroyl peroxide, tert.-butyl peroxyisobutyrate, tert-butyl peracetate and di-tert-butyl peroxide.

Polymers with optimal properties were obtained by the process according to the invention, when certain chain transfer agents have been used. Chain transfer agents to be used here can be: hydrogen or saturated hydrocarbons, e.g. propane, butane, isobutane, pentane, Hexane, heptane, alicyclic hydrocarbons, such as cyclohexane, methylcyclohexane, Cyclopentane, aromatic hydrocarbons, chlorinated hydrocarbons and aldehydes. Included in this are also saturated aliphatic alcohols with Γ to 6 carbon atoms and higher, "especially primary and secondary alcohols having 3 to 5 carbon atoms. Primary alcohols are for example methanol, ethanol, propanol, n-butanol, pentanol, hexanol, while as secondary and other alcohols isopropanol, isobutanol, sec-butanol, 3-methanol, 1-pentanol are suitable. It can Chain transfer agent mixed with ethylene in proportions of about 0.2 to about 6 mol percent, based on total ethylene.

In addition to the above chain transfer agents, aliphatic ketones can also be used in approximately the same molar ratio can be used. It becomes ketones with 3 to 10 carbon atoms preferred, preferably those with 3 to 5 carbon atoms, such as acetone, Diethyl ketone, diamyl ketone, diisobutyl ketone, methyl ethyl ketone, Methyl isopropyl ketone, ethyl butyl ketone and ethyl propyl ketone. Aldehydes can also be used with approximately the same number of carbon atoms are used, such as formaldehyde, Acetaldehyde and n-valeraldehyde. Aldehydes can be used in a molar ratio of 0.05 to ethylene or lower to 3 mole percent based on total ethylene can be used. .

As ethylenically unsaturated monomers that can be copolymerized with the ethylene, Olefins, preferably those having 3 to 10 carbon atoms, are particularly useful. examples for such olefins are propylene, isobutylene, butene-1, hexene-1, 3-methylbutene-1, 4-methylbutene-1, octene-1 and Nonen-1. It is usually desirable to be 0.01 to 4 mole percent, and preferably 0.2 to 3 mole percent of total ethylene in such un-

to use saturated olefins. At this point it must be mentioned that it was found that Olefins act as chain transfer agents.

It is also possible to use other copolymerizable, ethylenically unsaturated monomers with the terminal group CH ₂ = C <. Examples of such compounds are acrylic and methacrylic acid, substituted acrylic compounds and esters of acrylic and methacrylic acid, such as the methyl, ethyl and stearyl esters; Vinyl chloride, vinylidene chloride; Vinyl carboxylic acid esters such as vinyl acetate, vinyl propionate; and substituted vinyl monomers such as vinyl compounds containing a nitrogen group. Styrene, α-chlorostyrene, vinyl naphthalene, are also suitable. Vinyl ethers, such as, for example, vinyl methyl ether, vinyl butyl ether, and vinyl ketones, such as, for example, vinyl ethyl ketone.

Any combination of the above compounds, e.g. , hexane and propylene, can also be used to produce polymers or copolymers of certain desired physical properties.

The test methods used to determine the polymer properties are standard methods in the plastics industry. The impact strength in & 25u is determined in accordance with ASTM D-I709-59T. Yield strength in kg / cm ² , tensile strength in kg cm ² and percentage elongation are determined according to ASTM 638-60T. The percent opacity is determined according to ASTM D-10O3-59T, while the percent gloss is determined at at an angle of 60

ίο incident light with a Gardner gloss meter is measured. The tear strength is determined according to the Elmendorf method and is called tear strength in g / 25 α door the machine direction and door the Transverse direction indicated. The density is determined with a standard density column under standard conditions.

Example Γ

This example is a compilation of various attempts that have high conversions like also show the use of lower preheating temperatures. ·

Attempt no.

Synthesis conditions
Reaction pressure, kg / cm ²

Initiator composition
(molar base)

Lauroyl peroxide

tert-butylperoxyiso-

butyrate

tert-butyl peracetate ...
Di-tert-butyl peroxide ..

Injection temperature , ~ C
(nearly)

Peak temperature, '' C
(nearly)

Conversion,% .....

Polymer key figures
Density, g / cm ^J at 23 ^C C
Melt Index, g / 10 minutes (range)

2320

• 2nd °

1.60

1.0

0.67

138.9

290.6 12.6

0.9275 1.7 to 6.3

2320

3.0

■ ·. 2.0 1.0 0.50

137.8 '

292.8. 12.6

0.9275 1.2 to 2.6 2320

3.0

2.0
1.0
0.50

154.4

291.7
12.0

0.9275
1.0 to 2.3

2320

3.0.

2.0
1.0
0.50.

143.9

291.1
12.9

0.9275
1.3 to 2.3

2320

5.0

2.98

1.0

0.33

132.2

291.7 13.1

■ 0.9293 1.3 to 2.4

2320

4.1

2.2

1.0 0.5

132.2

291.7 13.5

0.9297. 2.1 to 2.8

In the above experiments, hexane was used as a chain transfer agent in a molar concentration from about 0.8 to 3.4 used.

The experiments given above show the purpose, namely higher conversions than in known processes, in which conversions usually below 10%. d .. h · from 5 to 8%. These experiments also show that by reducing the injection temperature of ethylene of from about 154 ° C (Run no. 3, conversion 12.0%) are obtained at 132.2 to 137.8 ⁰ C transformations well above 12% (experiment Nr. 6, conversion 13.5%) .. Furthermore, as shown, the higher conversions were obtained by increasing the molar concentration of the type I peroxydinitiator (only based on actual moles of initiator, in that the solvent was not taken into account), while a relatively lower Type III concentration was used as previously discussed elsewhere in the specification.

The versatility and ease of control of the various process conditions of a high pressure polymerization process Door ethylene if the multi-component initiators are used according to the invention, are further illustrated by Experiments Nos. 1, 2 and 3 in Example 2 set out that the production of a polymer with shows increased density. :

example

Synthesis conditions
Reaction pressure. kg cm ²

Initiator composition (molar basis)

Laurylpcroxide

tert-butyiperoxy isobulyrate

tcrt.-butyl peracctate ..............

Di-tert-butyl peroxide

liinspritztcmpcratur, C (approximately) .. peak temperature. C (approximately) ...

Conversion, ",,." ......-

Polymer numbers

Density, preferably ³ at 23 C .......;

Schniclzindcx. g K) minutes (range)

fis as 1 hexane s transmission means used in the example as a chain. ₂

One can see from the above series of experiments. that high conversions as well as higher densities obtained by changing the molar initiator concentration and the injection temperature can be. During the various experiments outlined above, controlled temperature

I. Attempt no. 2320 2320 2320 3.0 3.0 3.0 ■ ^y 2.0 2.0 2.0 1.0 1.0 1.0 0.25 0.50 - 0.25 • 142 142 142 266 266 266 -11.5 11.5 11.4- . 0.9301 0.9303 0.9302 1.1 to 2.0 3.5 to 4.6 1.0 to 2.9

Maintain ralurprofile as discussed above with reference to the drawings. .,.

While hexane has been indicated above as a chain transfer agent. other such agents can be used, as previously mentioned.

The following example 3 shows the use of butene-1 as C'omonomeres in various Mole percent at the indicated pressures.

example

System conditions

Reaction pressure. kg enr ..........

Mind-1-salary. Molpio / ent

Initiator composition (molar base oil)

tert-Bulylperox \ isobut \ rat

lert.-Bunlperacetai

Di-tert-butylpero \ yd ...........

Polymer key figures

Density, g cm 'at 23 C

Melt index, u 10 minutes

at 190 C

Yield strength, kg cnr

Elongation at break

Processed Film (Blown Pipe)

l'opacity. ""

Shine. ""

Impact strength, g 25 -ι

Lilmendorf Reil. <prt> be. g 25 μ in

Machine direction;.

in Ouei direction ... _;

VeiMi.ch No.

2320 i 2320 ; 2320 0.29 : 0.35 0.47
i 1.92 i 1.92 1.92 l. (X) I. (K) ¹ 1.00 1.05 1.05 : ■ 1.05

0.9240

0.9251

The above example shows the use of \ on initiators of types I. H and III and various Properties of the l'ohnieren or the one obtained from it-0.9245

6.9 142 140

8.1 . 8.x 56

360

245 '

I requested "ilnie. While the examples have demonstrated the use of three and four initiators iirfindung on, use \ is on five or more

1.9 ■; 3.2 141 ■ j 142 600 ■ .1 350 7.6 K.3 . 9.2:. P.8 59 '', ' 58 315 350 200 ^: 245

Initiator components applicable to achieve the desired goal that one continuous Has free radical generation and a controlled reaction vessel temperature profile.

Claims (4)

Patent claims: 1. Process for the polymerization of ethylene, alone or together with other ethylenically unsaturated monomers, in tubular reaction zones at pressures above 1054 kg / cm ² and temperatures of 107 to 316 ° C in the presence of mixtures of several free radical catalysts, d ad u rc h indicates that the polymerization is carried out in the presence of a peroxide mixture. a type I peroxide whose half-life is 10 hours at temperatures from 43.3 to 79.4 C, a type II peroxide whose half-life is 10 hours at a temperature of 79.4 to 121 C, and a HI-type peroxide. whose half-life at a temperature of 121 to 160 C is 10 hours. 2. The method according to claim 1, characterized ge indicates that other ethylenically unsaturated monomers' olefins, which are at least 'Contain 3 carbon atoms, are used. 3. The method according to claim 1, characterized in that the polymerization in the presence a chain transfer agent. 4. The method according to claim 1 to 3, characterized in that a peroxide mixture is used will that as. Type I peroxide 2,4-dichlorobenzoyl peroxide, caproyl peroxide, lauroyl peroxide, tert-butyl peroxyisobutyrate, benzoyl peroxide, p-chlorobehzoyl peroxide, acetyl peroxide, decanoyl peroxide. Isopropyl peroxydicarbonate or tert-butyl peroxypivalate, as type II peroxide tert-butyl peracetate, tert-butyl perbenzoate, dicumyl peroxide, Diethyl dioxide. tert-butylhydroxide, Methyl ethyl ketone peroxide, di-tert-butyl diperphthalate, hydroxyheptyl peroxide or cyclohexanone peroxide and as type III peroxide p-menthane hydroperoxide, pinane hydroperoxide, cumene hydroperoxide, Contains di-tert-butyl peroxide or 2.5-dimethylhydroxane-2.5-dihydroproxide. 1 sheet of drawings 009 640 140