Process for preparing a-olefin feed stream and polymerization process using same

Abstract

The present invention relates to a process for preparing an alpha-olefin feed stream, the process comprising: providing a low pressure initial stream comprising a hydrocarbon solvent at a low pressure level in the range from below atmospheric pressure to 15 barg; pressurizing the low pressure initial stream to a medium pressure level in the range of greater than 15 barg to 45 barg to form a medium pressure initial stream; pressurizing the medium pressure initial stream to a high pressure level in the range of greater than 45 barg to 300 barg to form a high pressure initial stream; wherein a monomer stream comprising an alpha-olefin monomer is introduced at a medium pressure level into the medium pressure initial stream and / or at a high pressure level into the high pressure initial stream, and one or more comonomer streams comprising at least one alpha-olefin comonomer are introduced at a low pressure level into the low pressure initial stream, and / or introducing the medium pressure initial stream at a medium pressure level and / or introducing the high pressure initial stream at a high pressure level to form an alpha-olefin feed stream. Alternatively, the medium pressure level may be omitted, a monomer stream comprising an alpha-olefin monomer is introduced into the high pressure initial stream at a high pressure level; and introducing one or more comonomer streams comprising at least one alpha-olefin comonomer to the low pressure initial stream at a low pressure level and / or to the high pressure initial stream at a high pressure level; to form an alpha-olefin feed stream. The process achieves solution polymerization with reduced process complexity and improved process economy.

Description

Technical Field

[0001] The present invention relates to a process for preparing a feed stream, in particular an alpha-olefin feed stream for solution polymerization, and a polymerization process using the same. Background Art

[0002] In solution polymerization processes, it is essential that all reactants are completely absorbed (i.e., dissolved) in the solvent upstream of the reactor. Therefore, before the reactant(s) and solvent(s) are introduced into the polymerization reactor, they are typically brought together, mixed, and dissolved. This process is generally understood as preparing the feed stream to the solution polymerization reactor.

[0003] The feed stream to a solution polymerization reactor can be prepared by mixing fresh solvent with fresh reactants. However, a portion of the mixture leaving the reactor is typically recovered and reintroduced into the feed stream preparation process. This arrangement offers the advantage of recovering not only material but also energy, as these recycled streams, in addition to the unreacted reactants and solvent they contain, can be provided with a defined temperature and pressure.

[0004] Furthermore, the recycle stream typically consists of a condensed product (liquid) and an uncondensed product (vapor). Volatile impurities and hydrogen are typically present in the vapor phase, but may also be present in the liquid phase. Removal of volatile components from the liquid phase or mixed liquid / vapor phase is typically accomplished by simply venting the volatile components, i.e., allowing the volatiles to evaporate during a sudden reduction in pressure. However, in the case of solution polymerization, volatile reactants, such as ethylene or propylene, are also present in the recycle stream. Therefore, simply venting the aforementioned volatile components will inevitably result in significant losses of reactants that could otherwise be used in the solution polymerization process.

[0005] Therefore, for solution polymerization, it is generally necessary to optimize the feed stream preparation equipment and its process based on the control of volatile components and improved recovery of volatile reactants.

[0006] Furthermore, the feed stream transferred to the reactor for solution polymerization must contain sufficient monomer, comonomer, and solvent to produce the desired polymer with a sufficiently high comonomer content. Furthermore, the feed stream also contains hydrogen, which can cause chain length control problems when it is recycled. Therefore, for economic reasons, hydrogen must be adequately purged while maintaining sufficient monomer, comonomer, and solvent in the process. Consequently, the feed stream composition must be carefully replenished or adjusted, and reactor feed operating conditions must be carefully controlled. Since the recycle stream withdrawn and recovered from the solution polymerization reactor is obtained as a low-pressure liquid stream with a moderate temperature, it must be repressurized to dissolve sufficient concentrations of monomer and comonomer. Comonomer reactants can be added at various pressure levels, depending on the properties and absorption capacity of the monomer reactants. For economic reasons, it is desirable to feed the comonomer at the lowest possible pressure. However, not all comonomers can be added to a low-pressure feed stream. For example, 1-butene cannot typically be added at high concentrations at low pressure because it will not dissolve completely or at all in the stream. If a comonomer (such as 1-butene) evaporates from a monomer (such as ethylene), it can also cause cavitation problems in one or more pumps. Another issue is that higher-pressure comonomers like 1-octene are preferably dosed on the low-pressure side, which helps keep the monomer (such as ethylene) in the process rather than venting it with the exhaust gas. Therefore, the various comonomers must be dosed at different pressure levels, which makes the process more complex in terms of economics and costs.

[0007] In solution polymerization processes, the recycle stream to be recycled into the system is typically derived from the post-reactor vacuum flash stream. This recycle stream is then transferred to the reactor feed stream by adding fresh solvent, monomer, and / or comonomer to compensate for reactant or solvent losses. In addition to restoring the feed stream composition, the reactor feed operating conditions must also be adjusted. The recycle stream is typically a low-pressure liquid stream at a moderate temperature, while the reactor feed stream is a cold stream, typically at a pressure of 50 to 120 barg.

[0008] Document WO 2010 / 027491 A1 discloses a method for feeding ethylene into a polymerization system in liquid or supercritical phase operation, comprising: providing a low-pressure ethylene stream, one or more low-pressure C3 to C 20The monomer stream, the optional low-pressure inert solvent / diluent stream and one or more reactors are metered and mixed together to form a low-pressure mixed liquid feed stream carrying ethylene, the low-pressure mixed liquid feed stream carrying ethylene is pressurized to the polymerization system pressure with one or more high-pressure pumps to form a high-pressure mixed reactor feed stream carrying ethylene, and the high-pressure mixed reactor feed stream carrying ethylene is fed to one or more reactors. Before being pressurized to the reactor pressure, the monomer recovery stream may also be optionally mixed with the ethylene feed stream and the C3 to C 20 Higher olefins are mixed.

[0009] The recycle feed stream must be re-pressurized before it can be used as a reactor feed. In an initial step, the depressurized recycle feed stream (typically at a low pressure level in the range of less than 15 barg) is pressurized to a medium pressure level in the range of about 15 barg to 45 barg, and gaseous monomer reactants (typically ethylene or propylene) are also fed into the recycle stream at this medium pressure level. Due to the absorption energy from the dissolution of the monomer reactants, this stream is cooled, and the reactor feed stream is then pressurized from the medium pressure level to a high pressure level in the range of greater than 45 barg, typically at least about 90 barg.

[0010] Therefore, the object of the present invention is to provide a process for preparing an alpha-olefin feed stream for solution polymerization, which process has reduced process complexity and improved process economy. In addition, the versatility for using a variety of different process reactants should be high. Summary of the Invention

[0011] It has therefore surprisingly been found that the above objects can be achieved by a process for preparing an alpha-olefin feed stream, which comprises:

[0012] providing a low pressure initial stream comprising a hydrocarbon solvent at a low pressure level in the range of subatmospheric pressure to 15 barg;

[0013] pressurizing the low-pressure initial flow to a medium-pressure level in a range of greater than 15 barg to 45 barg to form a medium-pressure initial flow;

[0014] pressurizing the medium-pressure initial flow to a high-pressure level in a range of greater than 45 barg to 300 barg to form a high-pressure initial flow;

[0015] The method further comprises:

[0016] introducing a monomer stream comprising an α-olefin monomer into the medium-pressure initial stream at a medium-pressure level and / or into the high-pressure initial stream at a high-pressure level;

[0017] and

[0018] introducing one or more comonomer streams comprising at least one α-olefin comonomer into the low-pressure initial stream at a low pressure level, and / or into the medium-pressure initial stream at a medium pressure level, and / or into the high-pressure initial stream at a high pressure level;

[0019] to form an alpha-olefin feed stream,

[0020] Wherein, the α-olefin monomer is selected from ethylene and propylene,

[0021] wherein when one or more comonomer streams are introduced into the low pressure initial stream at a low pressure level, the at least one α-olefin comonomer is selected from 1-heptene, 1-octene, 1-nonene and 1-decene or mixtures thereof; and

[0022] Wherein, when one or more comonomer streams are introduced into the medium-pressure initial stream at a medium pressure level, and / or introduced into the high-pressure initial stream at a high pressure level, the at least one α-olefin comonomer is selected from propylene, 1-butene, 1-pentene and 1-hexene or a mixture thereof.

[0023] The above objects can also be achieved by a process for preparing an alpha-olefin feed stream, the process comprising:

[0024] providing a low pressure initial stream comprising a hydrocarbon solvent at a low pressure level in the range of subatmospheric pressure to 15 barg;

[0025] pressurizing the low-pressure initial stream to a high-pressure level in a range of greater than 45 barg to 300 barg to form a high-pressure initial stream;

[0026] The method further comprises:

[0027] introducing a monomer stream comprising an alpha-olefin monomer into the high pressure initial stream at a high pressure level;

[0028] and

[0029] introducing one or more comonomer streams comprising at least one α-olefin comonomer into the low-pressure initial stream at a low pressure level and / or into the high-pressure initial stream at a high pressure level;

[0030] to form an alpha-olefin feed stream,

[0031] Wherein, the α-olefin monomer is selected from ethylene and propylene,

[0032] wherein when one or more comonomer streams are introduced into the low pressure initial stream at a low pressure level, the at least one α-olefin comonomer is selected from 1-heptene, 1-octene, 1-nonene and 1-decene or mixtures thereof; and

[0033] Wherein, when one or more comonomer streams are introduced into the medium-pressure initial stream at a medium pressure level, and / or introduced into the high-pressure initial stream at a high pressure level, the at least one α-olefin comonomer is selected from propylene, 1-butene, 1-pentene and 1-hexene or a mixture thereof.

[0034] These objects are further achieved by a process for the polymerization of alpha-olefin polymers in liquid or under supercritical conditions, comprising:

[0035] preparing an alpha-olefin feed stream as described above;

[0036] conveying the α-olefin feed stream to one or more polymerization reactors arranged in parallel, in series, or a combination thereof; and

[0037] The α-olefin feed stream is contacted with a catalyst in the one or more polymerization reactors to form a reaction mixture comprising an α-olefin polymer.

[0038] In this disclosure, the term "low pressure level" means a pressure level in the range from below atmospheric pressure to 15 barg.

[0039] The term "medium pressure level" denotes a pressure level in the range of greater than 15 barg to 45 barg.

[0040] The term "high pressure level" means a pressure level in the range of greater than 45 barg to 300 barg.

[0041] As used herein, the term "volatile components" refers to components preferably found in the liquid and vapor recovery streams provided by the recovery section of a solution polymerization process. Such streams contain components that can evaporate from such liquid streams when the pressure of the streams is released or the temperature is increased. Such volatile components can include inert gases such as nitrogen, unreacted light monomers such as ethylene and propylene, lower hydrocarbons such as methane, ethane, propane, or butane, volatile impurities typically generated by side reactions during the polymerization process, and hydrogen.

[0042] As used herein, the term "fresh liquid" refers to the liquid used in the feed stream that contains no volatile components at ambient conditions (ie, 1 atm pressure and 20°C).

[0043] As used herein, the term "recovery liquid" refers to the liquid used in the feed stream that has an amount of volatile components at ambient conditions (ie, 1 atm pressure and 20°C).

[0044] As used herein, the term "recovery vapor" refers to a gaseous composition comprising an amount of volatile components.

[0045] As used herein, the term "reactant" refers to monomers such as ethylene or propylene, but also includes optionally one or more comonomers. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 A schematic diagram of a reactor layout according to the prior art is shown. It should be understood that this schematic diagram does not reflect the actual size of the feed device. The same applies to the remaining figures.

[0047] Figure 2 A schematic diagram of a reactor layout according to a preferred embodiment of the present invention is shown.

[0048] Figure 3 A schematic diagram of a reactor layout according to another preferred embodiment of the present invention is shown. DETAILED DESCRIPTION

[0049] As a first option, the present invention provides a process for preparing an alpha-olefin feed stream, the process comprising:

[0050] providing a low pressure initial stream comprising a hydrocarbon solvent at a low pressure level in the range of subatmospheric pressure to 15 barg;

[0051] pressurizing the low-pressure initial flow to a medium-pressure level in a range of greater than 15 barg to 45 barg to form a medium-pressure initial flow;

[0052] pressurizing the medium-pressure initial flow to a high-pressure level in a range of greater than 45 barg to 300 barg to form a high-pressure initial flow;

[0053] The method further comprises:

[0054] introducing a monomer stream comprising an α-olefin monomer into the medium-pressure initial stream at a medium-pressure level and / or into the high-pressure initial stream at a high-pressure level, preferably into the high-pressure initial stream at a high-pressure level;

[0055] and

[0056] introducing one or more comonomer streams comprising at least one α-olefin comonomer into the low-pressure initial stream at a low pressure level, and / or into the medium-pressure initial stream at a medium pressure level, and / or into the high-pressure initial stream at a high pressure level;

[0057] to form an alpha-olefin feed stream,

[0058] Wherein, the α-olefin monomer is selected from ethylene and propylene,

[0059] wherein when one or more comonomer streams are introduced into the low pressure initial stream at a low pressure level, the at least one α-olefin comonomer is selected from 1-heptene, 1-octene, 1-nonene and 1-decene or mixtures thereof; and

[0060] Wherein, when one or more comonomer streams are introduced into the medium-pressure initial stream at a medium pressure level, and / or introduced into the high-pressure initial stream at a high pressure level, the at least one α-olefin comonomer is selected from propylene, 1-butene, 1-pentene and 1-hexene or a mixture thereof.

[0061] As a second option, the process of the present invention for preparing an alpha-olefin feed stream comprises the following steps:

[0062] providing a low pressure initial stream comprising a hydrocarbon solvent at a low pressure level in the range of subatmospheric pressure to 15 barg;

[0063] pressurizing the low-pressure initial stream to a high-pressure level in a range of greater than 45 barg to 300 barg to form a high-pressure initial stream;

[0064] The method further comprises:

[0065] introducing a monomer stream comprising an alpha-olefin monomer into the high pressure initial stream at a high pressure level;

[0066] and

[0067] introducing one or more comonomer streams comprising at least one α-olefin comonomer into the low-pressure initial stream at a low pressure level and / or into the high-pressure initial stream at a high pressure level;

[0068] to form an alpha-olefin feed stream,

[0069] Wherein, the α-olefin monomer is selected from ethylene and propylene,

[0070] wherein when one or more comonomer streams are introduced into the low pressure initial stream at a low pressure level, the at least one α-olefin comonomer is selected from 1-heptene, 1-octene, 1-nonene and 1-decene or mixtures thereof; and

[0071] Wherein, when one or more comonomer streams are introduced into the medium-pressure initial stream at a medium pressure level, and / or introduced into the high-pressure initial stream at a high pressure level, the at least one α-olefin comonomer is selected from propylene, 1-butene, 1-pentene and 1-hexene or a mixture thereof.

[0072] The present invention generally provides a process for preparing an alpha-olefin feed stream for solution polymerization comprising at least one solvent, at least one alpha-olefin monomer reactant, one or more comonomer reactants, and optionally hydrogen, an inert gas, and / or impurities.

[0073] Typically, the method of the present invention is associated with a solution polymerization process. The method of the present invention provides an alpha-olefin feed stream for use in a solution polymerization process. Preferably, the method of the present invention is used to recover streams (liquid stream and vapor stream) extracted from the solution polymerization process. Even more preferably, the two solution polymerization processes (i.e., the solution polymerization process to which the feed stream is fed and the solution polymerization process from which the recovery stream is withdrawn) are one and the same solution polymerization process.

[0074] Preferably, the present invention is applicable to supercritical polymerization processes, solution polymerization processes, and advanced solution polymerization processes, more preferably continuous supercritical polymerization processes, solution polymerization processes, and advanced solution polymerization processes. Most preferably, the production process comprises a continuous solution polymerization process.

[0075] The process of the present invention facilitates processing of vacuum recovery streams, reducing processing / pressurization steps, while also increasing the valuable monomer content of the alpha olefin feed stream ultimately used to polymerize alpha olefin polymers.

[0076] According to the present invention, the α-olefin monomer introduced with the monomer stream is selected from ethylene and propylene.

[0077] According to the present invention, the at least one alpha-olefin comonomer introduced into the low pressure initial stream together with one or more comonomer streams at a low pressure level is selected from 1-heptene, 1-octene, 1-nonene and 1-decene or mixtures thereof.

[0078] The at least one α-olefin comonomer introduced into the medium pressure initial stream at the medium pressure level and / or into the high pressure initial stream at the high pressure level together with the one or more comonomer streams is selected from propylene, 1-butene, 1-pentene and 1-hexene or mixtures thereof.

[0079] The process of the present invention may involve introducing a single or more than one comonomer stream into the process. Thus, a first α-olefin comonomer and an optional second α-olefin comonomer that are different from each other may be introduced with the comonomer stream. Examples of introducing the first α-olefin comonomer and the second α-olefin comonomer as comonomer streams at different pressure levels are described in detail in the Examples section.

[0080] The process according to the invention may preferably further comprise: introducing a chain transfer agent stream comprising at least one chain transfer agent, preferably hydrogen, into said medium pressure stream, and / or introducing said high pressure initial stream at a high pressure level.

[0081] The method according to the present invention may preferably further comprise: introducing a hydrocarbon solvent stream comprising additional hydrocarbon solvent into said low-pressure initial stream at a low pressure level.

[0082] The low pressure level is preferably a pressure in the range of 2 barg to 10 barg, the medium pressure level is preferably a pressure in the range of 20 barg to 40 barg, and the high pressure level is preferably a pressure in the range of 50 barg to 250 barg.

[0083] The medium pressure initial stream is preferably cooled after pressurization and / or after the monomer stream and one or more comonomer streams are introduced. Alternatively or additionally, the high pressure initial stream can be cooled after pressurization and / or after the monomer stream and one or more comonomer streams are introduced.

[0084] According to the present invention, the temperature of the low-pressure initial stream may preferably be in the range of 10° C. to 50° C., more preferably 20° C. to 40° C. The temperature of the medium-pressure initial stream may preferably be in the range of 20° C. to 50° C., more preferably 25° C. to 45° C. The temperature of the high-pressure initial stream may preferably be in the range of -40° C. to 50° C., more preferably -30° C. to 40° C.

[0085] According to the present invention, the concentration of α-olefin monomers in the medium pressure initial stream may preferably be in the range of 0 to 22 wt.-%, more preferably in the range of 0 to 21 wt.-%, even more preferably in the range of 0.01 to 20 wt.-%.

[0086] The concentration of the at least one α-olefin comonomer in the medium-pressure initial stream may preferably be in the range of 0 wt.-% to 35 wt.-%, more preferably in the range of 0.01 wt.-% to 20 wt.-%, even more preferably in the range of 0.01 wt.-% to 15 wt.-%, or alternatively preferably in the range of 0.01 wt.-% to 50 wt.-%, more preferably in the range of 0.01 wt.-% to 40 wt.-%, even more preferably in the range of 0.01 wt.-% to 35 wt.-%. According to a preferred embodiment of the above invention, the concentration of 1-butene as the at least one α-olefin comonomer in the medium-pressure initial stream may preferably be in the range of 0 wt.-% to 15 wt.-%, or the concentration of 1-octene as the at least one α-olefin comonomer in the medium-pressure initial stream may preferably be in the range of 0.01 wt.-% to 35 wt.-%.

[0087] The concentration of the α-olefin monomer in the high pressure initial stream may preferably be in the range of 10 wt.-% to 20 wt.-%, more preferably in the range of 12 wt.-% to 20 wt.-%.

[0088] The concentration of the at least one α-olefin comonomer in the high-pressure initial stream may preferably be in the range of 0 wt.-% to 35 wt.-%, more preferably in the range of 0.01 wt.-% to 20 wt.-%, even more preferably in the range of 0.01 wt.-% to 15 wt.-%, or alternatively in the range of 0 wt.-% to 50 wt.-%, more preferably in the range of 0 wt.-% to 40 wt.-%, even more preferably in the range of 0 wt.-% to 35 wt.-%. According to a preferred embodiment of the above invention, the concentration of 1-butene as the at least one α-olefin comonomer in the high-pressure initial stream may preferably be in the range of 0 wt.-% to 15 wt.-%, or the concentration of 1-octene as the at least one α-olefin comonomer in the high-pressure initial stream may preferably be in the range of 0 wt.-% to 35 wt.-%.

[0089] The streams defined above may be liquid or in a supercritical phase.

[0090] According to the present invention, the low pressure initial stream may preferably be a recovery stream.

[0091] A solvent is also present during solution polymerization. The solvent is in a liquid or supercritical state under the polymerization conditions. The solvent is usually and preferably a hydrocarbon solvent. The liquid hydrocarbon solvent used is preferably C 5-12 Hydrocarbons, which may be unsubstituted or replaced by C 1-4 Alkyl substitution, such as pentane, methylpentane, hexane, heptane, octane, cyclohexane, methylcyclohexane and hydrogenated naphtha or a combination thereof. More preferably, unsubstituted C 6-10 Hydrocarbon solvents, most preferably unsubstituted C 5-7 hydrocarbon solvents or combinations thereof.

[0092] Other components may also be added to the reactor. It is known to add hydrogen to the reactor to control the molecular weight of the polymer formed during polymerization. The use of various antifouling compounds is also known in the art. In addition, various types of activity enhancers or activity inhibitors can be used to control the activity of the catalyst.

[0093] Typically, the stream withdrawn from the polymerization reactor comprising solvent, polymer and unreacted monomers and optionally comonomers has a polymer content of 10 to 35 wt.-%, preferably 12.5 to 30 wt.-%, more preferably 15 to 25 wt.-%.

[0094] In addition, the stream taken out from the reactor is usually further processed, and the solvent, monomer and comonomer are recovered, that is, sent to a separation section downstream, and its amount is greater than 50% of the total stream taken out from the polymer stream, preferably greater than 60%, and most preferably greater than 70%. In this separation section, the polymer feed stream is usually separated into a concentrated phase rich in polymer and a vapor phase poor in polymer. The polymer-poor vapor phase, which is sent to a first separation device by the reactor outlet and contains solvent, unreacted monomer and comonomer, inert gas, hydrogen and volatile impurities, is subsequently separated by cooling into a recovery liquid stream and a recovery vapor stream. As described herein (in the examples), this recovery liquid stream and optional recovery vapor stream are sent to a recovery feed container according to the present invention.

[0095] The solution polymerization process can be carried out in a solution polymerization apparatus as described, for example, in WO 2011 / 087728 A1 or EP 4 000 723 A1.

[0096] In a preferred embodiment of the present invention, when one or more comonomer streams are introduced into the low-pressure initial stream at a low pressure level, at least one α-olefin comonomer is selected from 1-heptene, 1-octene, 1-nonene and 1-decene or a mixture thereof; and wherein, when one or more comonomer streams are introduced into the medium-pressure initial stream at a medium pressure level, and / or introduced into the high-pressure initial stream at a high pressure level, at least one α-olefin comonomer is selected from propylene, 1-butene, 1-pentene and 1-hexene or a mixture thereof.

[0097] This has the advantage that the introduction of the at least one α-olefin comonomer into the low-pressure initial stream at a low pressure level allows for maximum absorption of the α-olefin monomer, preferably ethylene or propylene, provided in the low-pressure initial stream.

[0098] In this embodiment, the at least one α-olefin comonomer introduced into the medium pressure initial stream at a medium pressure level and / or into the high pressure initial stream at a high pressure level can be substantially absorbed in the corresponding medium pressure or high pressure initial stream.

[0099] In one embodiment of the present invention, hydrogen is introduced into the medium-pressure initial stream at a medium-pressure level. One advantage of this embodiment is that by introducing the hydrogen at a medium-pressure level, the need for separate compression of the hydrogen to a higher pressure is avoided. The hydrogen is then entrained with the reactor feed at a medium pressure and compressed together with the reactor feed to the reactor pressure.

[0100] The low pressure level is more preferably a pressure in the range of 2 barg to 10 barg, and even more preferably 2 barg to 7 barg, still more preferably 2.5 barg or 3 barg to 6 barg.

[0101] The medium pressure level is more preferably a pressure in the range of 20 barg to 40 barg, and even more preferably 25 barg to 35 barg.

[0102] The high pressure level is more preferably a pressure in the range of 50 barg to 250 barg, even more preferably 60 barg to 200 barg, and still more preferably 70 barg to 200 barg.

[0103] It should be understood that each of the above ranges can be combined with each other, and each of the low pressure, medium pressure, and high pressure ranges can be combined with each other.

[0104] The concentration of the α-olefin monomer in the medium-pressure initial stream is preferably from 15 to 23 wt.%. The concentration of the at least one α-olefin comonomer in the medium-pressure initial stream is preferably from 0.01 to 35 wt.%. The concentration of the α-olefin monomer in the high-pressure initial stream is preferably from 15 to 20 wt.%, more preferably from 16 to 19 wt.%. The concentration of the at least one α-olefin comonomer in the high-pressure initial stream is preferably from 0.01 to 50 wt.%, more preferably from 5 to 45 wt.%, even more preferably from 10 to 40 wt.%, all based on the total weight of the respective stream.

[0105] It should be understood that each of the above concentration ranges can be combined with each other.

[0106] One effect of the present invention is that when the comonomer is introduced under elevated pressure, more comonomer (e.g., propylene, 1-butene, 1-pentene, and 1-hexene, or mixtures thereof) is absorbed. Due to the higher concentration of the at least one comonomer in the reactor feed stream, a higher comonomer content can be achieved in the resulting copolymer, which translates into a lower density and, consequently, an α-olefin elastomer with high product performance suitability. Similarly, when the monomer is introduced under elevated pressure, more monomer (e.g., ethylene or propylene) is absorbed, and therefore less gaseous monomer needs to be purged, which is beneficial in terms of process economics.

[0107] The introduction of higher carbon number comonomers (such as 1-heptene, 1-octene, 1-nonene and 1-decene or mixtures thereof) at elevated pressures is detrimental to process economics due to higher monomer losses or the need for higher pressures to optimize monomer absorption in the feed stream. Therefore, these higher carbon number comonomers are typically introduced at low pressure levels.

[0108] In the feed process of the present invention, the hydrocarbon solvent stream comprising additional hydrocarbon solvent may be introduced into the low-pressure initial stream, preferably at a low-pressure level.

[0109] In case a chain transfer agent is used, it may be preferably introduced into the high-pressure initial stream at a high-pressure level together with a chain transfer agent stream comprising at least one chain transfer agent, preferably hydrogen.

[0110] In the feed process of the present invention, it is preferred that the medium-pressure initial stream and / or the high-pressure initial stream be cooled after pressurization and / or after introduction of the monomer stream and one or more comonomer streams. This can be accomplished by providing one or more heat exchangers downstream of the feed vessel containing the medium-pressure or high-pressure initial stream and / or downstream of the pressurizing pump used to pressurize the initial stream to the medium-pressure or high-pressure level, respectively.

[0111] The temperature of the low-pressure initial stream is preferably in the range of 10° C. to 50° C., more preferably 20° C. to 40° C. The temperature of the medium-pressure initial stream is preferably in the range of 20° C. to 50° C., more preferably 25° C. to 45° C. The temperature of the high-pressure initial stream is in the range of -40° C. to 50° C., preferably -30° C. to 40° C.

[0112] At least one or more, or all, of the streams discussed above may be liquid or in a supercritical phase.

[0113] The low pressure initial stream may be a recycle stream recovered from the product stream of a solution polymerization process as described above.

[0114] The final α-olefin feed stream formed in the feeding process of the present invention can be used for the polymerization of α-olefin polymers in liquid or under supercritical conditions. Therefore, the present invention also relates to a method for the polymerization of α-olefin polymers in liquid or under supercritical conditions, comprising:

[0115] preparing an alpha-olefin feed stream as described above;

[0116] conveying the alpha-olefin feed stream to one or more polymerization reactors arranged in parallel, series, or a combination thereof; and

[0117] The α-olefin feed stream is contacted with a catalyst in the one or more polymerization reactors to form a reaction mixture comprising an α-olefin polymer.

[0118] The α-olefin polymer produced in the present invention may be any polymer. Preferably, the polymer produced in the present invention is an α-olefin homopolymer or copolymer. More preferably, the monomers of such a polymer are selected from α-olefins having 2 to 4 carbon atoms, preferably selected from ethylene, propylene, and 1-butene, more preferably selected from ethylene and propylene, and most preferably selected from ethylene. Particularly preferably, the polymer is an ethylene copolymer or homopolymer.

[0119] If the polymer is a copolymer, the comonomer is preferably different from the α-olefin monomer and is selected from linear and cyclic α-olefins having 2 to 12 carbon atoms and mixtures thereof. More preferably, the comonomer is an α-olefin different from the olefin monomer and is selected from linear α-olefins having 2 to 12 carbon atoms (preferably 4 to 10 carbon atoms) and mixtures thereof, and most preferably is selected from 1-butene and 1-octene.

[0120] The polymer may also be an elastomeric alpha-olefin copolymer, such as an ethylene or propylene copolymer.

[0121] In a most preferred embodiment, the polymer is produced in a solution polymerization process as described below.

[0122] Polymerization is carried out conventionally in the presence of an olefin polymerization catalyst. An olefin polymerization catalyst can be any catalyst known in the art that can make monomer and optional comonomer be polymerized. Therefore, the polymerization catalyst can be a Ziegler-Natta catalyst as disclosed in EP-A-280352, EP-A-280353 and EP-A-286148, or it can be a metallocene catalyst as disclosed in WO-A-1993025590, US-A-5001205, WO-A-1987003604 and US-A-5001244, or it can be a combination of these catalysts. Other suitable catalysts (for example late transition metal catalysts) also can be used.

[0123] Examples of suitable processes for polymerizing α-olefin polymers can be found, for example, in WO 2017 / 108951 A1 and WO 2017 / 108969 A1.

[0124] The above-mentioned reaction mixture comprising an α-olefin polymer may optionally be further polymerized in one or more other polymerization reactors, which involve the feeding of one or more comonomers, to obtain a product stream comprising an α-olefin polymer composition as the desired product. Preferably, the α-olefin polymer composition is an elastomeric α-olefin polymer composition, preferably an elastomeric ethylene or propylene copolymer. Examples of the desired product are, for example, ethylene and one or more C3 to C 10 Elastomer or plasticizer copolymerized with comonomer, or propylene and one or more C4 to C 10 The elastomer or plastomer is copolymerized with a comonomer, wherein 1-butene and / or 1-octene are preferred comonomers.

[0125] Example

[0126] Comparative Example 1: Production of Butene Plastomer

[0127] Establish a basis Figure 1The reactor layout shown. 1-Butene comonomer is added as a low-pressure first comonomer to the outlet of the recovery feed vessel (1) to prepare a 5 wt.-% concentration of 1-butene as a low-pressure comonomer in a solvent at a temperature of about 40°C and a pressure of about 6 barg, thereby obtaining a low-pressure initial stream (a).

[0128] The pressure is increased to a level of 35 barg by a recycle feed pump (2) downstream of the recycle feed vessel (1).

[0129] At this medium-pressure level, ethylene is fed as monomer (c) so as to reach a concentration of 20 wt.-% after cooling the medium-pressure initial stream thus obtained.

[0130] After the medium-pressure initial stream is passed through the first heat exchanger (3) and the reactor feed container (4) downstream of the first heat exchanger (3), the pressure is increased to 92 barg by the reactor feed pump (5). The high-pressure initial stream thus obtained is fed to the second heat exchanger (6).

[0131] At this high pressure level, high pressure hydrogen (d) is fed downstream of the second heat exchanger (6) to reach the final composition of the reactor feed stream, which is fed to the reactor (7).

[0132] Inventive Example 1: Production of Butene Plastomers with Comonomer Dosing at Medium Pressure

[0133] according to Figure 2 The reactor layout was established. Solvent hexane was fed (a) to the recovery feed vessel (1) at a temperature of about 40°C and a pressure of about 5 barg to obtain a low-pressure initial flow. The pressure was increased to 35 barg by a recovery feed pump (2) downstream of the recovery feed vessel (1).

[0134] At this medium pressure level, ethylene was fed as monomer (c) in order to reach a final reactor feed concentration of 20 wt.-% after cooling the medium pressure initial stream thus obtained. 1-Butene comonomer was also added (b') to the medium pressure reactor feed vessel (1) in order to produce a final reactor feed concentration of 1-butene of 4 wt.-%.

[0135] After the medium-pressure initial stream is conveyed through the first heat exchanger (3) and the reactor feed vessel (4) downstream of the first heat exchanger (3), the pressure is increased to 94 barg by the reactor feed pump (5) to obtain the high-pressure initial stream.

[0136] At this high pressure level, high pressure hydrogen (d) is fed downstream of the second heat exchanger (6) to reach the final composition of the reactor feed stream, which is fed to the reactor (7).

[0137] Inventive Example 2: Production of Butene Plastomers with Comonomer Dosing at High Pressure

[0138] according to Figure 2 The reactor layout was established. Solvent hexane was fed (a) to the recovery feed vessel (1) at a temperature of about 40°C and a pressure of about 5 barg to obtain a low-pressure initial flow. The pressure was increased to 35 barg by a recovery feed pump (2) downstream of the recovery feed vessel (1).

[0139] At this medium pressure level, ethylene is fed as monomer (c) so as to reach a final reactor feed concentration of 20 wt.-% after cooling the medium pressure initial stream thus obtained, which is fed to the medium pressure reactor feed vessel (1).

[0140] After the medium-pressure initial stream is conveyed through the first heat exchanger (3) and the reactor feed vessel (4) downstream of the first heat exchanger (3), the pressure is increased to 94 barg by the reactor feed pump (5) to obtain the high-pressure initial stream. At this high pressure, the comonomer 1-butene stream (b") is added to prepare a final reactor feed concentration of 4 wt.-% 1-butene upstream of the second heat exchanger (6).

[0141] At this high pressure level, high pressure hydrogen (d) is fed downstream of the second heat exchanger (6) to reach the final composition of the reactor feed stream, which is fed to the reactor (7).

[0142] Inventive Example 3: Production of Butene Plastomers with Comonomer Dosing and Monomer Dosing at High Pressure

[0143] according to Figure 2 The reactor layout was established. Solvent hexane was fed (a) to the recovery feed vessel (1) at a temperature of about 40°C and a pressure of about 5 barg to obtain a low-pressure initial flow. The pressure was increased to 35 barg by a recovery feed pump (2) downstream of the recovery feed vessel (1).

[0144] This stream is fed to the reactor feed vessel (4), where the pressure is increased to 94 barg by means of a reactor feed pump (5) to obtain a high-pressure initial stream. At this high pressure, a comonomer 1-butene stream (b") is added to prepare a final reactor feed concentration of 4 wt.-% of 1-butene, and ethylene is fed as monomer (c') upstream of the second heat exchanger (6) to reach a final reactor feed concentration of 20 wt.-%.

[0145] At this high pressure level, high pressure hydrogen (d) is fed downstream of the second heat exchanger (6) to reach the final composition of the reactor feed stream, which is fed to the reactor (7).

[0146] Inventive Example 4: Production of Butene Plastomer with Comonomer Dosing and Monomer Dosing at High Pressure in a Single Pump Configuration

[0147] according to Figure 3 The reactor layout was established. Solvent hexane was fed (a) to the recovery feed vessel (1) at a temperature of about 40°C and a pressure of about 5 barg to obtain a low-pressure initial flow. The pressure was increased to 94 barg by the reactor feed pump (5) downstream of the recovery feed vessel (1).

[0148] At this high pressure, the comonomer 1-butene stream (b") is added to prepare a final reactor feed concentration of 4 wt.-% of 1-butene, and ethylene is fed as monomer (c') upstream of the second heat exchanger (6) to reach a final reactor feed concentration of 20 wt.-%.

[0149] At this high pressure level, high pressure hydrogen (d) is fed downstream of the second heat exchanger (6) to reach the final composition of the reactor feed stream that will be fed to the reactor (7).

[0150] Tag number

[0151] 1: Recycle the feed container a: Low pressure initial flow, feed: solvent + first comonomer 2: Recycling feed pump b: Second comonomer added to the low pressure initial flow 3: First heat exchanger b': Second comonomer added to the medium pressure initial flow 4: Reactor feed container b": Second comonomer added to the high pressure initial flow 5: Reactor feed pump c: Monomer added to the medium pressure initial flow 6: Second heat exchanger c': monomer added to the high pressure initial flow 7: Polymerization reactor d: Hydrogen added to the high pressure initial flow

Claims

1. A process for preparing an alpha-olefin feed stream, the process comprising: providing a low pressure initial stream comprising a hydrocarbon solvent at a low pressure level in the range of subatmospheric pressure to 15 barg; pressurizing the low-pressure initial flow to a medium-pressure level in a range of greater than 15 barg to 45 barg to form a medium-pressure initial flow; pressurizing the medium-pressure initial flow to a high-pressure level in a range of greater than 45 barg to 300 barg to form a high-pressure initial flow; The method further comprises: introducing a monomer stream comprising an α-olefin monomer into the medium-pressure initial stream at a medium-pressure level, and / or introducing the high-pressure initial stream at a high-pressure level; and introducing one or more comonomer streams comprising at least one α-olefin comonomer into the low-pressure initial stream at a low pressure level, and / or into the medium-pressure initial stream at a medium pressure level, and / or into the high-pressure initial stream at a high pressure level; to form an alpha-olefin feed stream, Wherein, the α-olefin monomer is selected from ethylene and propylene, wherein when one or more comonomer streams are introduced into the low pressure initial stream at a low pressure level, the at least one α-olefin comonomer is selected from 1-heptene, 1-octene, 1-nonene and 1-decene or mixtures thereof; and Wherein, when one or more comonomer streams are introduced into the medium-pressure initial stream at a medium pressure level, and / or introduced into the high-pressure initial stream at a high pressure level, the at least one α-olefin comonomer is selected from propylene, 1-butene, 1-pentene and 1-hexene or a mixture thereof.

2. A process for preparing an alpha-olefin feed stream, the process comprising: providing a low pressure initial stream comprising a hydrocarbon solvent at a low pressure level in the range of subatmospheric pressure to 15 barg; pressurizing the low-pressure initial stream to a high-pressure level in a range of greater than 45 barg to 300 barg to form a high-pressure initial stream; The method further comprises: introducing a monomer stream comprising an alpha-olefin monomer into the high pressure initial stream at a high pressure level; and introducing one or more comonomer streams comprising at least one α-olefin comonomer into the low-pressure initial stream at a low pressure level and / or into the high-pressure initial stream at a high pressure level; to form an alpha-olefin feed stream, Wherein, the α-olefin monomer is selected from ethylene and propylene, wherein when one or more comonomer streams are introduced into the low pressure initial stream at a low pressure level, the at least one α-olefin comonomer is selected from 1-heptene, 1-octene, 1-nonene and 1-decene or mixtures thereof; and Wherein, when one or more comonomer streams are introduced into the high pressure initial stream at a high pressure level, the at least one α-olefin comonomer is selected from propylene, 1-butene, 1-pentene and 1-hexene or a mixture thereof.

3. The method according to claim 1 or 2, wherein: The at least one α-olefin comonomer introduced into the low-pressure initial stream at a low pressure level is different from the at least one α-olefin comonomer introduced into the medium-pressure initial stream at a medium pressure level and / or introduced into the high-pressure initial stream at a high pressure level.

4. The method according to any one of the preceding claims, further comprising: A chain transfer agent stream comprising at least one chain transfer agent, preferably hydrogen, is introduced into the medium pressure stream and / or into the high pressure initial stream at a high pressure level.

5. The method according to any one of the preceding claims, further comprising: A hydrocarbon solvent stream comprising additional hydrocarbon solvent is introduced into the low pressure initial stream at a low pressure level.

6. A method according to any one of the preceding claims, wherein The low pressure level is a pressure in the range of 2 barg to 10 barg, and / or The medium pressure level is a pressure in the range of 20 barg to 40 barg, and / or The high pressure level is a pressure in the range of 50 barg to 250 barg.

7. A method according to any one of the preceding claims, wherein The medium-pressure initial stream is cooled after pressurization and / or after introduction of the monomer stream and the one or more comonomer streams, and / or the high-pressure initial stream is cooled after pressurization and / or after introduction of the monomer stream and the one or more comonomer streams.

8. A method according to any one of the preceding claims, wherein The temperature of the low-pressure initial flow is in the range of 10°C to 50°C, more preferably 20°C to 40°C; the temperature of the medium-pressure initial flow is in the range of 20°C to 50°C, more preferably 25°C to 45°C; and / or the temperature of the high-pressure initial flow is in the range of -40°C to 50°C, more preferably -30°C to 40°C.

9. A method according to any one of the preceding claims, wherein The concentration of the alpha-olefin monomer in the medium pressure initial stream is in the range of 0 wt.-% to 22 wt.-%, and / or The concentration of the at least one alpha-olefin comonomer in the medium pressure initial stream is in the range of 0 wt.-% to 35 wt.-%, or alternatively in the range of 0.01 wt.-% to 50 wt.-%, and / or The concentration of the alpha-olefin monomer in the high pressure initial stream is in the range of 10 wt.-% to 20 wt.-%, and / or The concentration of the at least one α-olefin comonomer in the high pressure initial stream is in the range of 0 wt.-% to 35 wt.-%, or alternatively in the range of 0 wt.-% to 50 wt.-%.

10. A method according to any one of the preceding claims, wherein The stream is either liquid or in a supercritical phase.

11. A method according to any one of the preceding claims, wherein The low-pressure initial flow is the recovery flow.

12. A process for the polymerization of alpha-olefin polymers in liquid or under supercritical conditions, the process comprising: preparing an alpha-olefin feed stream according to any one of the preceding claims; conveying the α-olefin feed stream to one or more polymerization reactors arranged in parallel, in series, or a combination thereof; and The α-olefin feed stream is contacted with a catalyst in the one or more polymerization reactors to form a reaction mixture comprising an α-olefin polymer.

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