Formation of bimodal molecular weight poly(hydroxyalkanoate)

Abstract

A poly(hydroxyalkanoate) composition having a bimodal molecular weight distribution. The composition includes a first portion and a second portion of poly(hydroxyalkanoate). The first portion has a first weight average molecular weight and the second portion has a second weight average molecular weight that is at least 50 percent less than the first weight average molecular weight. The poly(hydroxyalkanoate) is composed of at least 10 mole percent of 3-hydroxypropionate monomer repeat units. A method for preparing the composition is also disclosed.

Description

Technical Field

[0001] The present disclosure relates to biodegradable polymer compositions. More specifically, the present disclosure relates to poly(hydroxyalkanoate) compositions having a bimodal molecular weight distribution and methods for preparing such compositions.

Background Art

[0002] Poly(hydroxyalkanoate) can be prepared by a ring-opening polymerization process. In such a polymerization, the physical properties of the polymer are often defined by the molecular weight. In order to obtain desirable physical properties, it is often desirable to produce a polymer with the largest possible molecular weight.

[0003] On the other hand, if increasing the molecular weight would improve all physical properties, that is not the case. For example, melt viscosity is strongly defined by the molecular weight, and if the melt viscosity is too high, thermal processing of the polymer in typical conversion devices can be difficult.

[0004] Therefore, it would be desirable to produce a poly(hydroxyalkanoate) composition that has a high molecular weight and exhibits many of the advantageous physical properties associated with an increase in molecular weight, while at the same time exhibiting a decrease in melt viscosity typically associated with a decrease in molecular weight.

Summary of the Invention

[0005] In response to the above and other needs, the present disclosure provides a poly(hydroxyalkanoate) composition having a bimodal molecular weight distribution. In other words, the molecular weight distribution of the poly(hydroxyalkanoate) in the composition exhibits two different molecular weight peaks.

[0006] Generally, the composition comprises a first portion of poly(hydroxyalkanoate) and a second portion of poly(hydroxyalkanoate). The first and second portions each have their own distinct weight-average molecular weights. Thus, the first portion of poly(hydroxyalkanoate) has a first weight-average molecular weight, and the second portion of poly(hydroxyalkanoate) has a second weight-average molecular weight. According to this disclosure, the second weight-average molecular weight is at least 50 percent smaller than the first weight-average molecular weight.

[0007] More specifically, the first weight-average molecular weight is typically at least 100,000 daltons, as determined by ASTM D5296. Preferably, the first weight-average molecular weight is at least 200,000 daltons, as determined by ASTM D5296. Even more preferably, the first weight-average molecular weight is at least 300,000 daltons, as determined by ASTM D5296.

[0008] In contrast, the second weight-average molecular weight, as determined by ASTM D5296, is preferably less than about 25,000 daltons.

[0009] Due to this molecular weight difference, the composition typically has a polydispersity of at least 1.9, as determined by ASTM D5296. More preferably, the composition typically has a polydispersity of about 1.9 to about 3.5, as determined by ASTM D5296.

[0010] Typically, the composition contains about 90 to about 50 weight percent of the first part poly(hydroxyalkanoate) and about 50 to about 50 weight percent of the second part poly(hydroxyalkanoate). It contains 10% by weight. More preferably, the composition contains about 85 to about 60% by weight of the first part poly(hydroxyalkanoate) and about 40 to about 15% by weight of the second part poly(hydroxyalkanoate).

[0011] In some embodiments, the weight ratio of the first portion of poly(hydroxyalkanoate) to the second portion of poly(hydroxyalkanoate) is approximately 1:1 to approximately 9:1.

[0012] The poly(hydroxyalkanoate) of this composition contains at least 10 mole percent of monomer repeating units of 3-hydroxypropionate. In certain embodiments, the poly(hydroxyalkanoate) may contain at least 25, at least 50, or at least 75 mole percent of monomer repeating units of 3-hydroxypropionate.

[0013] Broadly speaking, the poly(hydroxyalkanoate) in a composition may be a homopolymer, copolymer, or terpolymer. Therefore, in certain embodiments, the poly(hydroxyalkanoate) includes a homopolymer, i.e., poly(3-hydroxypropionate).

[0014] In other embodiments, poly(hydroxyalkanoate) is, The first repeating unit is (3-hydroxypropionate), Equation I [ka] The second iteration unit and Optionally, Equation II [ka] The third iteration unit and A copolymer or terpolymer containing the following: In the formula, R1 and R2 are each independently selected from the group consisting of linear or branched alkyl groups having 1 to 22 carbon atoms.

[0015] In some embodiments, the poly(hydroxyalkanoate) is more preferably a copolymer, and R1 is methyl. In such embodiments, the poly(hydroxyalkanoate) copolymer is preferably composed of about 10 to about 90 moles of the first repeating units. Including cents, it contains approximately 90 to 10 mole percent of the second repeating unit.

[0016] In other embodiments, the poly(hydroxyalkanoate) is more preferably a terpolymer, where R1 is methyl and R2 is propyl. In such embodiments, the poly(hydroxyalkanoate) terpolymer preferably contains about 15 to about 75 mole percent of a first repeating unit, about 75 to about 15 mole percent of a second repeating unit, and about 1 to about 5 mole percent of a third repeating unit.

[0017] Advantageously, this bimodal poly(hydroxyalkanoate) composition has been shown to exhibit good physical properties associated with increased molecular weight, while simultaneously reducing melt viscosity.

[0018] The disclosure also provides various articles comprising the aforementioned poly(hydroxyalkanoate) compositions. In one embodiment, the disclosure provides a film comprising a poly(hydroxyalkanoate) composition having a bimodal molecular weight distribution. In another embodiment, the disclosure provides a fiber comprising a poly(hydroxyalkanoate) composition having a bimodal molecular weight distribution.

[0019] In another embodiment, the present disclosure provides a method for preparing a composition having a first portion of poly(hydroxyalkanoate) and a second portion of poly(hydroxyalkanoate). According to one embodiment, the method includes the step of polymerizing a first amount of at least one substituted lactone to produce a first portion of poly(hydroxyalkanoate) having a first weight-average molecular weight. The method also includes the step of polymerizing a second amount of at least one substituted lactone to produce a second portion of poly(hydroxyalkanoate) having a second weight-average molecular weight, the second weight-average molecular weight being at least 50 percent smaller than the first weight-average molecular weight.

[0020] The method further includes the step of mixing a first portion and a second portion to produce a final poly(hydroxyalkanoate).

[0021] According to the present disclosure, at least one substituted lactone includes beta-propiolactone, and the poly(hydroxyalkanoate) includes monomer repeating units of 3-hydroxypropionate.

[0022] According to certain embodiments of the method, the poly(hydroxyalkanoate) is a homopolymer, i.e., poly(3-hydroxypropionate).

[0023] In other embodiments of the method, the poly(hydroxyalkanoate) is a first repeating unit that is (3-hydroxypropionate), and Formula I

Chemical formula

Chemical formula

[0024] In some embodiments of the method, the step of mixing the first portion and the second portion is carried out by polymerizing the second amount in the presence of the first portion to form the second portion.

[0025] In some embodiments of the method, the step of mixing the first portion and the second portion is carried out by polymerizing the second amount in the presence of the first portion to form the second portion.

Mode for Carrying Out the Invention

[0026] This disclosure provides a poly(hydroxyalkanoate) composition having a bimodal molecular weight distribution. This poly(hydroxyalkanoate) composition is industrially compostable and / or home compostable, as determined by ASTM D6400.

[0027] According to one embodiment, the composition comprises a first portion of poly(hydroxyalkanoate) and a second portion of poly(hydroxyalkanoate). The first portion of poly(hydroxyalkanoate) has a first weight-average molecular weight, and the second portion of poly(hydroxyalkanoate) has a second weight-average molecular weight that is at least 50 percent smaller than the first weight-average molecular weight. Furthermore, according to this disclosure, the poly(hydroxyalkanoate) comprises at least 10 mole percent of monomer repeating units of 3-hydroxypropionate.

[0028] Generally, the poly(hydroxyalkanoate) in a composition may be a homopolymer, copolymer, or terpolymer. Therefore, in certain embodiments, the poly(hydroxyalkanoate) is a homopolymer, i.e., poly(3-hydroxypropionate).

[0029] In other embodiments, poly(hydroxyalkanoate) is, The first repeating unit is (3-hydroxypropionate), Equation I [ka] The second iteration unit and Optionally, Equation II [ka] The third iteration unit and A copolymer or terpolymer composed of, In the formula, R1 and R2 are each independently selected from the group consisting of linear or branched alkyl groups having 1 to 22 carbon atoms.

[0030] In some embodiments, the poly(hydroxyalkanoate) is more preferably a copolymer, and R1 is methyl. In such embodiments, the poly(hydroxyalkanoate) copolymer generally consists of about 10 to about 90 mole percent of first repeating units and about 90 to about 10 mole percent of second repeating units.

[0031] In other embodiments, the poly(hydroxyalkanoate) is more preferably a terpolymer, where R1 is methyl and R2 is propyl. In such embodiments, the poly(hydroxyalkanoate) terpolymer generally consists of about 15 to about 75 mole percent of first repeating units, about 75 to about 15 mole percent of second repeating units, and about 1 to about 5 mole percent of third repeating units.

[0032] According to a particular embodiment, the composition contains about 90 to about 50 weight percent of the first part of poly(hydroxyalkanoate) and about 50 to about 10 weight percent of the second part of poly(hydroxyalkanoate).

[0033] In some embodiments, the weight ratio of the first portion of poly(hydroxyalkanoate) to the second portion of poly(hydroxyalkanoate) is approximately 1:1 to approximately 9:1.

[0034] In some cases, the first weight-average molecular weight is at least 100,000 daltons, as determined by ASTM D5296, and the second weight-average molecular weight is less than approximately 25,000 daltons, as determined by ASTM D5296.

[0035] In a particular embodiment, the composition, as determined by ASTM D5296, is small It has a polydispersity index of at least 1.9.

[0036] The bimodal poly(hydroxyalkanoate) compositions according to this disclosure have good physical properties associated with an increase in molecular weight, while also having a reduced melt viscosity.

[0037] This disclosure also provides various articles containing the aforementioned poly(hydroxyalkanoate) composition.

[0038] For example, in one embodiment, the disclosure provides a film comprising a poly(hydroxyalkanoate) composition having a bimodal molecular weight distribution. The film structure may be formed by blow film extrusion, cast film extrusion, or cast film extrusion followed by biaxial stretching. Such films may be used in end uses such as bags, pouches, food packaging, agricultural mulch films, and protective packaging.

[0039] In another embodiment, the disclosure provides fibers comprising a poly(hydroxyalkanoate) composition having a bimodal molecular weight distribution. Such fibers may be formed by extrusion as staple fibers, monofilaments, or nonwovens. The fibers may be used in end applications such as fabrics, wipes, diapers, sanitary products, yarns, or geotextiles.

[0040] In another aspect, the disclosure also provides a method for preparing a poly(hydroxyalkanoate) composition having a bimodal molecular weight distribution. As described above, the poly(hydroxyalkanoate) composition comprises a first part of poly(hydroxyalkanoate) and a second part of poly(hydroxyalkanoate), each part having its own distinct weight-average molecular weight, wherein the second weight-average molecular weight (i.e., that of the second part) is substantially smaller than the first weight-average molecular weight (i.e., that of the first part).

[0041] Generally, according to the method, both the first and second poly(hydroxyalkanoate) portions are formed by ring-opening polymerization of substituted lactones.

[0042] Therefore, the method comprises a first step of polymerizing a first amount of at least one substituted lactone to produce a first portion poly(hydroxyalkanoate) having a first weight-average molecular weight.

[0043] The method also includes the step of polymerizing a second amount of at least one substituted lactone to produce a second portion poly(hydroxyalkanoate) having a second weight-average molecular weight.

[0044] The method also includes the step of mixing the first part and the second part to produce the final poly(hydroxyalkanoate).

[0045] Various different forms of poly(hydroxyalkanoates) having a bimodal molecular weight distribution can be prepared according to the methods of this disclosure. The properties of the poly(hydroxyalkanoates) are determined by at least one substituted lactone used as a starting material.

[0046] Generally, at least one substituted lactone comprises at least a beta-propiolactone, and the resulting poly(hydroxyalkanoate) comprises monomeric repeating units of 3-hydroxypropionate formed from ring-opening of the beta-propiolactone.

[0047] In some cases, beta-propiolactone is the only substituted lactone starting material. The resulting poly(hydroxyalkanoate) is a homopolymer, i.e., poly(3-hydroxypropionate).

[0048] In other embodiments of the method, poly(hydroxyalkanoate) is used. The first repeating unit is (3-hydroxypropionate), Equation I [ka] The second iteration unit and Optionally, Equation II [ka] The third iteration unit and A copolymer or terpolymer composed of, In the formula, R1 and R2 are each independently selected from the group consisting of linear or branched alkyl groups having 1 to 22 carbon atoms.

[0049] In some embodiments, the poly(hydroxyalkanoate) is preferably a copolymer, and R1 is methyl. In such embodiments, the substituted lactone starting materials are beta-propiolactone and beta-butyrolactone. For such poly(hydroxyalkanoate) copolymers, the copolymer preferably contains about 10 to about 90 mole percent of a first repeating unit and about 90 to about 10 mole percent of a second repeating unit.

[0050] In other embodiments, the poly(hydroxyalkanoate) is further a terpolymer, where R1 is methyl and R2 is propyl. In such embodiments, the substituted lactone starting materials are beta-propiolactone, beta-butyrolactone, and beta-valerolactone. For such poly(hydroxyalkanoate) terpolymers, the terpolymer preferably contains about 15 to about 75 mole percent of a first repeating unit, about 75 to about 15 mole percent of a second repeating unit, and about 1 to about 5 mole percent of a third repeating unit.

[0051] Polymerization of a first amount to produce the first part of poly(hydroxyalkanoate), and polymerization of a second amount to produce the second part of poly(hydroxyalkanoate) Both can be performed either in a batch-based or sequential manner.

[0052] For example, a batch of the first portion can be polymerized in a first batch reactor, and a batch of the second portion can be polymerized in a second batch reactor. Subsequently, the poly(hydroxyalkanoate) of the first and second portions can be dissolved and mixed in, for example, an extruder or other melting and mixing device.

[0053] On the other hand, more preferably, both the first and second poly(hydroxyalkanoate) components can be produced on a continuous basis. A preferred reactor for this continuous polymerization process is a loop reactor in which the reactants pass through and recirculate a loop of piping. At one point, monomers, a catalyst, and a fresh solvent are supplied to this loop, and at different points in the loop, the reacted polymer is continuously extracted.

[0054] In a particularly preferred embodiment, the method of the present disclosure may be carried out using two loop reactors operated in series. A first amount of lactone is added to the first loop reactor along with a catalyst and a solvent, where it is polymerized to produce a first portion of poly(hydroxyalkanoate) having a first (larger) weight-average molecular weight. At the time of polymerization, the first portion of poly(hydroxyalkanoate) is then transferred to a second loop reactor. A second amount of lactone is added to the second loop reactor along with a catalyst and a solvent, where it is polymerized to produce a second portion of poly(hydroxyalkanoate) having a second (smaller) weight-average molecular weight.

[0055] Therefore, according to this embodiment, the second amount polymerizes in the presence of the first part to form the second part. According to this embodiment, it will be seen that the step of mixing the first part and the second part is carried out by polymerizing the second amount in the presence of the first part to form the second part.

[0056] For both polymerization steps, suitable solvents for carrying out the reaction include tetrahydrofuran and methyl (t-butyl ether). A catalyst or initiator is also preferably used. Suitable catalysts or initiators include quaternary ammonium salts. The amount of catalyst or initiator may differ between the first and second amount polymerizations. For the first amount polymerization to produce the first part poly(hydroxyalkanoate), the amount of catalyst or initiator is preferably about 1 part of catalyst or initiator per about 5000 parts of the first amount. For the second amount polymerization to produce the second part poly(hydroxyalkanoate), the amount of catalyst or initiator is preferably about 1 part of catalyst or initiator per about 500 parts of the second amount.

[0057] This disclosure is further illustrated by the embodiments described below.

[0058] Embodiment 1 A composition comprising a first portion of poly(hydroxyalkanoate) and a second portion of the same poly(hydroxyalkanoate), The poly(hydroxyalkanoate) in the first portion has a first weight-average molecular weight, and the poly(hydroxyalkanoate) in the second portion has a second weight-average molecular weight that is at least 50 percent smaller than the first weight-average molecular weight. The composition wherein the poly(hydroxyalkanoate) comprises at least 10 mole percent of monomer repeating units of 3-hydroxypropionate.

[0059] Embodiment 2 The aforementioned poly(hydroxyalkanoate) is poly(3-hydroxypropionate) The composition described in Embodiment 1, including

[0060] Embodiment 3 The aforementioned poly(hydroxyalkanoate) The first repeating unit is (3-hydroxypropionate), Equation I [ka] The second iteration unit and Optionally, Equation II [ka] The third iteration unit and A copolymer or terpolymer containing, The composition according to Embodiment 1, wherein R1 and R2 are each independently selected from the group consisting of linear or branched alkyl groups having 1 to 22 carbon atoms.

[0061] Embodiment 4 The composition according to Embodiment 3, wherein the poly(hydroxyalkanoate) comprises a copolymer and R1 is methyl.

[0062] Embodiment 5 The composition according to Embodiment 4, wherein the poly(hydroxyalkanoate) copolymer contains about 10 to about 90 mole percent of the first repeating unit and about 90 to about 10 mole percent of the second repeating unit.

[0063] Embodiment 6 The composition according to Embodiment 3, wherein the poly(hydroxyalkanoate) comprises a terpolymer, R1 is methyl, and R2 is propyl.

[0064] Embodiment 7 The composition according to Embodiment 6, wherein the poly(hydroxyalkanoate) terpolymer contains about 15 to about 75 mole percent of the first repeating unit, about 75 to about 15 mole percent of the second repeating unit, and about 1 to about 5 mole percent of the third repeating unit.

[0065] Embodiment 8 The composition according to any of the prior embodiments, wherein the composition comprises about 90 to about 50 weight percent of the first portion of the poly(hydroxyalkanoate) and about 50 to about 10 weight percent of the second portion of the poly(hydroxyalkanoate).

[0066] Embodiment 9 The composition according to any of the prior embodiments, wherein the first weight-average molecular weight is at least 100,000 daltons as determined by ASTM D5296, and the second weight-average molecular weight is less than about 25,000 daltons as determined by ASTM D5296.

[0067] Embodiment 10 The composition according to any of the prior embodiments, wherein the composition has a polydispersity of at least 1.9 as determined by ASTM D5296.

[0068] Embodiment 11 The composition according to any of the prior embodiments, wherein the weight ratio of the poly(hydroxyalkanoate) in the first portion to the poly(hydroxyalkanoate) in the second portion is about 1:1 to about 9:1.

[0069] Embodiment 12 A film comprising the composition described in any of the prior embodiments.

[0070] Embodiment 13 A fiber comprising the composition described in any of the prior embodiments.

[0071] Embodiment 14 A method for preparing a composition having a first portion of poly(hydroxyalkanoate) and a second portion of the poly(hydroxyalkanoate), wherein the method is A step of polymerizing a first amount of at least one substituted lactone to produce a first portion poly(hydroxyalkanoate) having a first weight-average molecular weight, A step of polymerizing a second amount of the at least one substituted lactone to produce a second portion of the poly(hydroxyalkanoate) having a second weight-average molecular weight, A step of mixing the first part and the second part to produce the final poly(hydroxyalkanoate), Includes, The at least one substituted lactone comprises a beta-propiolactone, and the poly(hydroxyalkanoate) comprises a monomer repeating unit of 3-hydroxypropionate. The method wherein the second weight-average molecular weight is at least 50 percent smaller than the first weight-average molecular weight.

[0072] Embodiment 15 The method according to Embodiment 14, wherein the poly(hydroxyalkanoate) includes poly(3-hydroxypropionate).

[0073] Embodiment 16 The aforementioned poly(hydroxyalkanoate) The first repeating unit is (3-hydroxypropionate), Equation I [ka] The second iteration unit and Optionally, Equation II [ka] The third iteration unit and A copolymer or terpolymer containing, The method according to Embodiment 14, wherein R1 and R2 are each independently selected from the group consisting of linear or branched alkyl groups having 1 to 22 carbon atoms.

[0074] Embodiment 17 The method according to any one of embodiments 14 to 16, wherein the first amount is polymerized in a first loop reactor.

[0075] Embodiment 18 The method according to any one of embodiments 14 to 17, wherein the second amount is polymerized in a second loop reactor.

[0076] Embodiment 19 The method according to any one of embodiments 14 to 18, wherein the step of mixing the first portion and the second portion is carried out by polymerizing the second amount in the presence of the first portion to form the second portion.

[0077] The foregoing description of preferred embodiments of the present invention is provided for illustrative and explanatory purposes only. They are not intended to be comprehensive or to limit the invention to the detailed forms disclosed. Obvious modifications or variations are possible based on the teachings above. The embodiments have been selected and described in an effort to provide best examples of the principles of the present invention and its practical applications, thereby enabling those skilled in the art to utilize the invention in various embodiments, and various modifications are made to suit specific intended uses. All such modifications and variations fall within the scope of the invention as determined by the appended claims, if they are interpreted in accordance with the scope to which they are fairly, legally, and justly granted.

Claims

1. A composition comprising a first portion of poly(hydroxyalkanoate) and a second portion of the same poly(hydroxyalkanoate), The aforementioned poly(hydroxyalkanoate) The first repeating unit is (3-hydroxypropionate), Equation I 【Chemistry 1】 The second iteration unit and Optionally, Equation II 【Chemistry 2】 The third iteration unit and A copolymer or terpolymer containing, In the formula, R 1 and R 2 Each of these is independently selected from the group consisting of linear or branched alkyl groups having 1 to 22 carbon atoms. The poly(hydroxyalkanoate) in the first portion has a first weight-average molecular weight, and the poly(hydroxyalkanoate) in the second portion has a second weight-average molecular weight that is at least 50 percent smaller than the first weight-average molecular weight. The composition wherein the poly(hydroxyalkanoate) contains at least 10 mole percent of monomer repeating units of 3-hydroxypropionate.

2. The poly(hydroxyalkanoate) comprises a copolymer, R 1 The composition according to claim 1, wherein is methyl.

3. The composition according to claim 2, wherein the poly(hydroxyalkanoate) copolymer contains 10 to 90 mole percent of the first repeating unit and 90 to 10 mole percent of the second repeating unit.

4. The aforementioned poly(hydroxyalkanoate) contains a terpolymer, R 1 is methyl, R 2 The composition according to claim 1, wherein is propyl.

5. The composition according to claim 4, wherein the poly(hydroxyalkanoate) terpolymer contains 15 to 75 mole percent of the first repeating unit, 75 to 15 mole percent of the second repeating unit, and 1 to 5 mole percent of the third repeating unit.

6. The composition according to claim 1, wherein the composition comprises 90 to 50 percent by weight of the first portion of the poly(hydroxyalkanoate) and 50 to 10 percent by weight of the second portion of the poly(hydroxyalkanoate).

7. The composition according to claim 1, wherein the first weight-average molecular weight is at least 100,000 daltons as determined by ASTM D5296, and the second weight-average molecular weight is less than 25,000 daltons as determined by ASTM D5296.

8. The composition according to claim 1, wherein the composition has a polydispersity of at least 1.9 as determined by ASTM D5296.

9. The composition according to claim 1, wherein the weight ratio of the poly(hydroxyalkanoate) in the first portion to the poly(hydroxyalkanoate) in the second portion is 1:1 to 9:

1.

10. A film comprising the composition described in claim 1.

11. A fiber comprising the composition described in claim 1.

12. A method for preparing a composition having a first portion of poly(hydroxyalkanoate) and a second portion of the poly(hydroxyalkanoate), wherein the method is A step of polymerizing a first amount of at least one substituted lactone to produce a first portion poly(hydroxyalkanoate) having a first weight-average molecular weight, A step of polymerizing a second amount of the at least one substituted lactone to produce a second portion of the poly(hydroxyalkanoate) having a second weight-average molecular weight, A step of mixing the first part and the second part to produce the final poly(hydroxyalkanoate), Includes, The at least one substituted lactone comprises a beta-propiolactone, and the poly(hydroxyalkanoate) comprises a monomer repeating unit of 3-hydroxypropionate. The method wherein the second weight-average molecular weight is at least 50 percent smaller than the first weight-average molecular weight.

13. The method according to claim 12, wherein the poly(hydroxyalkanoate) comprises poly(3-hydroxypropionate).

14. The aforementioned poly(hydroxyalkanoate) The first repeating unit is (3-hydroxypropionate), Equation I 【Transformation 3】 The second iteration unit and Optionally, Equation II 【Chemistry 4】 The third iteration unit and A copolymer or terpolymer containing, In the formula, R 1 and R 2 The method according to claim 12, wherein each of them is independently selected from the group consisting of linear or branched alkyl groups having 1 to 22 carbon atoms.

15. The method according to claim 12, wherein the first amount is polymerized in a first loop reactor.

16. The method according to claim 12, wherein the second amount is polymerized in a second loop reactor.

17. The method according to claim 12, wherein the step of mixing the first portion and the second portion is carried out by polymerizing the second amount in the presence of the first portion to form the second portion.

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