Use of radical scavengers to reduce fouling during high-pressure polymerization.

Abstract

An embodiment of a method for producing a high-pressure ethylene-based polymer comprises polymerizing an ethylene monomer feed and optionally an additional comonomer feed in the presence of a radical scavenger via free radical polymerization at a pressure of at least 1000 atmospheres (atm) to produce the high-pressure ethylene-based polymer, wherein the radical scavenger is represented by Structure 1: 40 ) hydrocarbyl, (C1-C 40 ) heterohydrocarbyl, or aromatic-containing moiety; and R4-R8 are each independently H, OH, (C1-C 40 ) hydrocarbyl, (C1-C 40 ) heterohydrocarbyl, or aromatic-containing moiety, provided that at least one of R4-R8 must be OH). [Case 1] JPEG2025533766000013.jpg28170

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims the benefit of U.S. Provisional Application No. 63 / 411,354, filed September 29, 2022, the entire disclosure of which is incorporated herein by reference.

[0002] FIELD OF THE INVENTION FIELD OF THE INVENTION The embodiments described herein relate generally to high pressure polymerization processes, and specifically to the use of radical scavengers used to reduce fouling during high pressure polymerization. [Background technology]

[0003] One of the major causes of reduced production rates in high-pressure polymerization processes is fouling, such as hypercompressor or preheater fouling. Therefore, there is a need for additives that eliminate reactor fouling but do not adversely affect the high-pressure polymerization process or products. Summary of the Invention

[0004] Embodiments of the present disclosure meet this need through the use of radical scavengers that can reduce the amount of fouling without adversely affecting the polymerization process or product properties.

[0005] According to at least one embodiment of the present disclosure, there is provided a method for producing a high-pressure ethylene-based polymer, the method comprising polymerizing an ethylene monomer feed and optionally an additional comonomer feed via free radical polymerization at a pressure of at least 1000 atmospheres (atm) in the presence of a radical scavenger to produce the high-pressure ethylene-based polymer, the radical scavenger having a structure represented by Structure 1:

[0006] [ka] (wherein n may be 0 to 100; R1, R2, and R3 each independently represent H, (C1 to C 40 ) hydrocarbyl, (C1-C 40 ) heterohydrocarbyl, or aromatic-containing moiety; and R4-R8 are each independently H, OH, (C1-C 40 ) hydrocarbyl, (C1-C 40 ) a heterohydrocarbyl, or aromatic-containing moiety, provided that at least one of R4-R8 is OH).

[0007] These and other embodiments are described in more detail in the detailed description below. DETAILED DESCRIPTION OF THE INVENTION

[0008] Certain embodiments of the present application will now be described. These embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art.

[0009] The term "polymer" refers to a polymeric compound prepared by polymerizing monomers, whether of the same or different types. Thus, the general term polymer generally encompasses the term "homopolymer," which refers to a polymer prepared from only one type of monomer, as well as the term "copolymer," which refers to a polymer prepared from two or more different monomers. As used herein, the term "interpolymer" refers to a polymer prepared by polymerization of at least two different types of monomers. Thus, the general term interpolymer includes copolymers or polymers prepared from more than two different types of monomers, such as terpolymers.

[0010] "Polyethylene" or "ethylene-based polymer" refers to a polymer containing more than 50 mole percent units derived from ethylene monomers. This includes ethylene-based homopolymers or copolymers (meaning the units are derived from two or more comonomers). Common forms of ethylene-based polymers known in the art include low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (ULDPE), very low-density polyethylene (VLDPE), single-site catalyzed linear low-density polyethylene (m-LLDPE), including both linear and substantially linear low-density resins, medium-density polyethylene (MDPE), and high-density polyethylene (HDPE). Ethylene-based polymers also encompass "ethylene acid copolymers," which are the polymerization reaction products of ethylene and one or more unsaturated carboxylic acid-containing monomers.

[0011] Embodiments are directed to a method of producing a high-pressure ethylene-based polymer, the method comprising polymerizing an ethylene monomer feed and optionally an additional comonomer feed in the presence of a radical scavenger via free radical polymerization at a pressure of at least 1000 atmospheres (atm) to produce the high-pressure ethylene-based polymer.

[0012] In embodiments, the high-pressure ethylene-based polymer is an ethylene homopolymer, such as low-density polyethylene (LDPE). In other embodiments, the high-pressure ethylene-based polymer is an ethylene copolymer comprising the polymerization reaction product of ethylene and a polar comonomer. In further embodiments, the high-pressure ethylene-based polymer is an ethylene acid copolymer comprising the polymerization reaction product of ethylene and a carboxylic acid-containing comonomer. The carboxylic acid-containing comonomer may comprise an unsaturated monocarboxylic acid, such as acrylic acid, methacrylic acid, or a combination thereof. In embodiments, the unsaturated carboxylic acid-containing comonomer may be present in an amount of 5% to 35%, 12 to 30%, 15 to 25%, or 21 to 25% by weight, based on the total weight of the monomers present in the ethylene acid copolymer. Conversely, the ethylene content of the ethylene acid copolymer is greater than 50% or greater than 60% by weight. For example, the ethylene content of the ethylene acid copolymer is 50% to 95%, 70% to 88%, 75% to 85%, or 75% to 79% by weight.

[0013] In embodiments, the radical scavenger has the structure 1:

[0014] [ka] (wherein n may be 0 to 100; R1, R2, and R3 each independently represent H, (C1 to C 40 ) hydrocarbyl, (C1-C 40 ) heterohydrocarbyl, or aromatic-containing moiety; and R4-R8 are each independently H, OH, (C1-C 40 ) hydrocarbyl, (C1-C 40 ) a heterohydrocarbyl, or aromatic-containing moiety, provided that at least one of R4-R8 is OH).

[0015] In further embodiments, n is 0 to 10, or preferably 0 to 5. In further embodiments, R1 is a C1-C6 alkene, preferably a C1-C3 alkene, or most preferably ethylene; and at least one of R2 and R3 is an aromatic-containing moiety. In other embodiments, at least one of R4-R8 must be OH, and at least one of R4-R8 must be a C1-C6 hydrocarbyl.

[0016] In other embodiments, the radical scavenger has the following structure:

[0017] [ka] (wherein m can be 0 to 100; R1 can be H, (C1 to C 40 ) hydrocarbyl, (C1-C 40 ) heterohydrocarbyl, or aromatic-containing moiety; R4-R8 are each independently H, OH, (C1-C 40 ) hydrocarbyl, (C1-C 40 ) heterohydrocarbyl, or aromatic-containing moiety, provided that at least one of R4 through R8 must be OH; R9 and R 10 are each independently H, (C1 to C 40 ) hydrocarbyl, or (C1-C 40 ) heterohydrocarbyl; and R 11 ~R 14 are each independently H, OH, (C1 to C 40 ) hydrocarbyl, (C1-C 40 ) heterohydrocarbyl, or aromatic-containing moiety).

[0018] In other embodiments, m is 0 to 10, or preferably 0 to 5. In other embodiments, at least one of R4 to R8 must be OH, and at least one of R4 to R8 must be C1 to C6 hydrocarbyl. In further embodiments, R9 and R 10 at least one of is H or C1-C6 hydrocarbyl, and R11 ~R 14 At least one of them is a C1 to C6 hydrocarbyl.

[0019] In other embodiments, the radical scavenger has the following structure:

[0020] [ka] In the formula, R1 is independently H, (C1 to C 40 ) hydrocarbyl, (C1-C 40 ) heterohydrocarbyl, or aromatic-containing moiety; R5-R8 are each independently H, OH, (C1-C 40 ) hydrocarbyl, (C1-C 40 ) heterohydrocarbyl, or aromatic-containing moiety; R9 is H, (C1-C 40 ) hydrocarbyl, or (C1-C 40 ) heterohydrocarbyl; and R 11 ~R 14 are each independently H, OH, (C1 to C 40 ) hydrocarbyl, (C1-C 40 ) heterohydrocarbyl, or aromatic-containing moiety).

[0021] In some embodiments, at least one of R5 to R8 and / or R 11 ~R 14 At least one of R5-R8 is either tert-butyl or tert-pentyl. In further embodiments, at least one of R5-R8 is tert-butyl, at least one of R5-R8 is methyl, or both conditions are met. In additional embodiments, R 11 ~R 14 at least one of R is tert-butyl; 11 ~R 14 is methyl, or both conditions are met. In further embodiments, at least one of R5-R8 is tert-pentyl. In additional embodiments, R 11 ~R 14At least one of is tert-pentyl.

[0022] In certain embodiments, the radical scavenger has the following structure:

[0023] [ka] This includes one or both of the following.

[0024] Various amounts are contemplated as suitable for the radical scavenger. In some embodiments, the radical scavenger is added at a concentration of 0.1 molar ppm to 5 ppm based on the amount of ethylene feed and, optionally, additional comonomer feed. In other embodiments, the radical scavenger is added at a concentration of 0.1 molar ppm to 1 ppm, or 0.25 to 0.75 ppm based on the amount of ethylene feed and, optionally, additional comonomer feed.

[0025] Additional additives are contemplated for the process of the present invention. For example, polymerization can occur in the presence of a chain transfer agent. In embodiments, the chain transfer agent comprises an aliphatic hydrocarbon, an olefinic hydrocarbon, a ketone, an aldehyde, or a saturated aliphatic aldehyde alcohol. In one embodiment, the chain transfer agent comprises propionaldehyde.

[0026] Free radical polymerization processes are generally known in the art. Generally, the process is conducted at high temperature and pressure, either as a batch process or in a continuous mode. Suitable reactors, such as tubular reactors or autoclave reactors, are well known to those skilled in the art. Additionally, compressor units upstream of the reactor and separator units downstream of the reactor are also well known to those skilled in the art. The polymerization pressure can be at least 1000 atm (101.3 MPa or 1013.25 bar), 1000 to 5000 atm, 1200 to 4000 atm, or 1500 to 3500 atm. The polymerization temperature typically ranges from about 70°C to about 380°C. All individual values ​​and subranges within the range of about 70°C to about 380°C are included herein and disclosed herein; for example, the polymerization temperature ranges from 100°C to 300°C, or from 150°C to 250°C.

[0027] In one or more embodiments, the high pressure ethylene-based polymer further comprises from 1 to 100 ppm of a radical scavenger, from 10 to 100 ppm of a radical scavenger, or from 10 to 50 ppm, based on the weight of the high pressure ethylene-based polymer.

[0028] Test Method Melt Index Melt index was measured according to ASTM D 1238-13, Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer, using the conditions 190°C / 2.16 kilograms (kg). Results were reported in grams dissolved per 10 minutes (g / 10 min) or the equivalent in decigrams per 1.0 minute (dg / 1 min).

[0029] Total dissolution method All samples used in this study were in pellet form. Approximately 1.0 g ± 0.02 g of resin was weighed into a clean 100 mL glass vial and the weight was recorded. A PTFE-coated stir bar was added to the vial. In the hood, 25 mL of o-xylene was added to the vial using an electronic pipette. The vial was sealed with a crimp cap. The vial was placed on the Gerstel robot, which completed the sample preparation. The sample was dissolved by placing the vial on a heating / stirring plate at 130 °C for 30 minutes. The solution was cooled on a 15-position stirrer for 15 minutes while mixing. After 15 minutes of cooling, 50 mL of isopropanol was added to the vial. The solution was stirred again for 2 hours. The stirrer was stopped, and the solid particles were allowed to settle. 1 mL of the solution was removed and transferred to a 2 mL capped glass autosampler vial. The autosampler vial was placed in the LC autosampler for analysis. Samples and standard solutions are analyzed using a reversed-phase liquid chromatography method with a UV / Vis absorbance detector. The concentrations of the extractables were determined using an external standard calibration procedure. [Example]

[0030] The following examples illustrate features of the present disclosure but are not intended to limit the scope of the disclosure.

[0031] Example 1 - Reactor Fouling Test Comparative Examples C1 and C2 Ethylene was added at 7 lb / hr along with 1000 mol ppm propionaldehyde in a 300 mL continuous reactor, and both were pressurized to 30,000 psi through the use of compressors and valves. The reactors were heated to 100°C (C1) or 140°C (C2) to mimic the temperatures in the compressor and preheater sections of an LDPE plant. Ethylene and propionaldehyde were allowed to flow through the reactor at this temperature for 18 hours. During the course of the 18 hours, all polymer formed was collected and weighed. At the end of the 18 hours, the reactor was opened and inspected for fouling levels.

[0032] Comparative Example C3 (BHT) For Comparative Example C3, the same procedure as Comparative Example C2 was used, except that butylated hydroxytoluene (BHT) was added to the propionaldehyde to give a final BHT concentration in the reactor of 0.5 mole ppm. BHT is a hindered phenolic antioxidant commonly used in LDPE processes, but does not contain (meth)acrylate substitution.

[0033] Examples I1 and I2 of the present invention For Inventive Examples I1 and I2, the same procedure as in the Comparative Example was used, except that Sumilizer GS (Structure 4) from Sumitomo Chemical was added to the propionaldehyde to give a final concentration in the reactor of 0.5 molar ppm. The reactor temperature was 100° C. for I1 and 140° C. for I2.

[0034] Additionally, reactor fouling was measured for Comparative Examples C1-C3 and Inventive Examples I1-I2, as shown in Table 1 below. As shown, each reactor was evaluated and ranked 1-5, with 1 being the most fouled and 5 being completely clean. As shown below, Inventive Samples I1 and I2 resulted in reactors that were either completely clean (I1=rank 5) or clean (I2=rank 5), with little or no polymer recovered thereon, both of which indicate reduced fouling. In contrast, Comparative Samples C1-C3 resulted in reactors with fouling ranks of 1-3, respectively, with at least three times the amount of polymer recovered on the reactor, all of which indicate increased fouling.

[0035] [Table 1]

[0036] Example 2 - Radical Scavenger Final Concentration The following example in Table 2 shows how radical scavengers are present in the final polymer concentration. In a 300 mL continuous reactor, ethylene was added at 25 lb / hr along with approximately 400 mol ppm propionaldehyde, and both were pressurized to 28,000 psi using a compressor and valve. The reactor was heated to 270°C and operated adiabatically. tert-Butyl peroxyacetate was added to produce 12% ethylene conversion in the reactor. Sumilizer GS was the radical scavenger added to the reactor as a solution in propionaldehyde at the levels shown in Table 2. In Table 2, the radical scavenger reactor feed concentration and the radical scavenger fed / polymer produced were determined based on mass balances from pilot plant data. The radical scavenger in the final polymer form was determined by the total dissolution method.

[0037] [Table 2]

[0038] It will be apparent that modifications and variations are possible without departing from the scope of the present disclosure, as defined in the appended claims. More specifically, while certain aspects of the present disclosure have been identified herein as preferred or particularly advantageous, it is not intended that the present disclosure be necessarily limited to these aspects.

Claims

1. 1. A method for producing a high-pressure ethylene-based polymer, comprising: and polymerizing an ethylene monomer feed and optionally an additional comonomer feed in the presence of a radical scavenger via free radical polymerization at a pressure of at least 1000 atmospheres (atm) to produce said high-pressure ethylene-based polymer, wherein said radical scavenger has the structure 1: 【Chemical 1】 where n=0 to 100; R １ , R ２ and R ３ are each independently H, (C １ ~C ４０ ) hydrocarbyl, (C １ ~C ４０ ) heterohydrocarbyl, or aromatic-containing moiety; and R ４ ~R ８ are each independently H, OH, (C １ ~C ４０ ) hydrocarbyl, (C １ ~C ４０ ) heterohydrocarbyl, or aromatic-containing moiety, provided that R ４ ~R ８ at least one of which must be OH.

2. The radical scavenger is represented by the formula: 【Chemistry 2】 where m can be 0 to 100; R １ is H, (C １ ~C ４０ ) hydrocarbyl, (C １ ~C ４０ ) heterohydrocarbyl, or aromatic-containing moiety; R ４ ~R ８ are each independently H, OH, (C １ ~C ４０ ) hydrocarbyl, (C １ ~C ４０ ) heterohydrocarbyl, or aromatic-containing moiety, provided that R ４ ~R ８ At least one of R must be OH; ９ and R １０ are each independently H, (C １ ~C ４０ ) hydrocarbyl, or (C １ ~C ４０ ) heterohydrocarbyl; and R １１ ~R １４ are each independently H, OH, (C １ ~C ４０ ) hydrocarbyl, (C １ ~C ４０ ) a heterohydrocarbyl, or aromatic-containing moiety.

3. The radical scavenger is represented by the formula: 【Chemistry 3】 (In the formula, R １ are independently H, (C １ ~C ４０ ) hydrocarbyl, (C １ ~C ４０ ) heterohydrocarbyl, or aromatic-containing moiety; R ５ ~R ８ are each independently H, OH, (C １ ~C ４０ ) hydrocarbyl, (C １ ~C ４０ ) heterohydrocarbyl, or aromatic-containing moiety; R ９ is H, (C １ ~C ４０ ) hydrocarbyl, or (C １ ~C ４０ ) heterohydrocarbyl; and R １１ ~R １４ are each independently H, OH, (C １ ~C ４０ ) hydrocarbyl, (C １ ~C ４０ 10. The method of any preceding claim, comprising a cycloalkyl group, a cycloalkyl group, a cyclohexyl ...

4. R ５ ~R ８ and / or R １１ ~R １４ 5. The method of any preceding claim, wherein at least one of is either tert-butyl or tert-pentyl.

5. The radical scavenger has the following structure: 【Chemistry 4】 10. A method according to any preceding claim, comprising one or both of:

6. 10. The method of any of the preceding claims, wherein the polymerization occurs in the presence of a chain transfer agent.

7. The method of claim 6, wherein the chain transfer agents include aliphatic and olefinic hydrocarbons, ketones, aldehydes, and saturated aliphatic aldehyde alcohols.

8. 8. The method of claim 6 or 7, wherein the chain transfer agent comprises propionaldehyde.

9. 10. The process of any preceding claim, wherein said radical scavenger is added at a concentration of from 0.1 molar ppm to 5 ppm, based on the amount of ethylene feed and optionally additional comonomer feed.

11. 10. The method of any preceding claim, wherein the additional comonomer comprises a polar monomer.

12. The method of any of claims 1 to 10, wherein the high-pressure ethylene-based polymer comprises low-density polyethylene (LDPE).

13. 10. A high-pressure ethylene-based polymer produced by the method of any preceding claim.

14. 14. The high-pressure ethylene-based polymer of claim 13, wherein the high-pressure ethylene-based polymer further comprises 1 to 100 ppm, based on the weight of the high-pressure ethylene-based polymer, of the radical scavenger of claims 1 to 12.

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