WO2026035931A1

WO2026035931A1 - Process for pelletizing polymers

Info

Publication number: WO2026035931A1
Application number: PCT/US2025/041078
Authority: WO
Inventors: Anthony Charles Neubauer; Simon J. White
Original assignee: Univation Technologies LLC
Current assignee: Univation Technologies LLC
Priority date: 2024-08-09
Filing date: 2025-08-07
Publication date: 2026-02-12
Anticipated expiration: 2027-02-09

Abstract

A process for pelletizing polymer products may comprise: extruding a polymer to form pellets in an extruder in communication with a polymer feeder, a gear pump, or both; passing the pellets from the extruder to a tank and then to a pellet feeder; pausing the pellet feeder; obtaining an initial weight (W_i) of the tank; and at a time after W_i is obtained, obtaining a final weight (W_f) of the tank; restarting the pellet feeder; calculating: a theoretical mass flow rate (M_ft) a theoretical mass transferred (M_tt) and/or a theoretical mass flow rate (M_ht) of the pellets; and calculating a correction factor C_fa or C_fb or C_fc;anddetermining the amount of the first polymer, the one or more additives, or both passed to the extruder in response to a predicted mass flow rate, a predicted mass transferred, and/or a predicted mass transferred computed by a controller.

Description

86153-WO-PCT/DOW 86153 WO

1

PROCESS FOR PELLETIZING POLYMERS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63/681,355 filed August 9, 2024, the contents of which are incorporated in their entirety herein.

BACKGROUND

[0002] Pelletizing processes combine polymer with one or more additives in an extruder. Precise control of the mass ratios of polymer and additives is necessary to produce polymer pellets having the desired composition and properties. In order to achieve such control, it is necessary to have a real time understanding of the amounts of polymer and/or additives passing through the extruder.

[0003] Previous measurement techniques have included polymer weighing belt feeders, loss in weight feeders, laser flow measurement, and many other similar devices. However, each of these systems has substantial drawbacks ranging from inaccuracy and low precision to high purchase cost and substantial maintenance demands.

BRIEF SUMMARY

[0004] Accordingly, reliable and inexpensive measurement techniques for determining the mass of polymer entering a pelletizing process are desired. Embodiments of the present disclosure meet this need by providing estimates of polymer flow using typically installed equipment and an additional step of determining obtaining data and determining correction factors. In embodiments, a theoretical flow rate of polymer is calculated based on gear pump speed, polymer feeder speed, or both. Generally, sufficient data is readily available to calculate the theoretical flow rate of polymer. Then the rate/amount of polymer converted to pellets is weighed in a pellet tank. Then, the theoretical polymer flow rate is routinely compared with total polymer converted to pellets by a controller to generate the correction factors.

[0005] In one embodiment, a process for pelletizing polymer products comprises: extruding a first polymer with one or more additives to form pellets in an extruder in communication with a polymer feeder, a gear pump, or both; passing the pellets from the extruder to a tank; 86153-WO-PCT/DOW 86153 WO

2 passing the pellets from the tank to a pellet feeder; pausing the pellet feeder while the extruder is still forming pellets: obtaining an initial weight (W_;) of the tank; when the pellet feeder is restarted, both the time period T after Wi is obtained and the final weight (Wf) of the tank are obtained; calculating: a theoretical mass flow rate (Ma) of the pellets according to Equation la and/or lb; a theoretical mass transferred (Mtt) of the pellets according to Equation 1c and/or Id; a theoretical mass flow rate (Mht) of the pellets according to Equation le and/or If; or more than one of these, wherein: Equation la: Ma = gear pump speed x gear pump volumetric efficiency x melt density x gear pump volume per revolution; Equation lb: Ma = polymer feeder speed x polymer feeder volumetric efficiency x bulk density x polymer feeder volume per revolution; Equation 1c: M_t = gear pump speed x gear pump volumetric efficiency x melt density x gear pump volume per revolution x T; and Equation Id: M_t = polymer feeder speed x polymer feeder volumetric efficiency x bulk density x polymer feeder volume per revolution x T; and Equation le: Mht = number of gear pump revolutions during time period T x gear pump volumetric efficiency x melt density x gear pump volume per revolution; and Equation If: Mht = number of polymer feeder revolutions during time period T x polymer feeder volumetric efficiency x bulk density x polymer feeder volume per revolution; and calculating a correction factor Cat or Cia or C& according to Equation 2a or

2b or 2c: Equation 2a: Cat = _w ; Equation 2b: Cia = - - — ; Equation 2c: Cf_c =

-E . Wf - Wi

- - — ; determining the amount of the first polymer, the one or more additives, or both Wf - Wj. passed to the extruder in response to a predicted mass flow rate (Mf_P) and/or a predicted mass transferred (M_tp) and/or a predicted mass transferred (Mh_P) computed by a controller, wherein h f_p h ft x fa and h t_p hlu x ia and t hp hl hi x fc-

[0006] These and other embodiments are described in detail in the Detailed Description. It is to be understood that both the foregoing general description and the following detailed description present embodiments of the presently disclosed technology, and are intended to provide an overview or framework for understanding the nature and character of the technology as it is claimed. For example and without limitation, embodiments of the methods described herein may be applicable to extrusion of pellets in addition to granular polymers, and to extrusion of thermoplastics and elastomers, including polyolefins, and to other 86153-WO-PCT/DOW 86153 WO

3 polymers, such as but not limited to polystyrene, polyvinyl chloride, polyurethane, polyester, polyethylene terephthalate, acrylonitrile butadiene styrene, and the like.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings in which:

[0008] FIG. 1 illustrates a system for pelletizing polymer products.

[0009] FIG. 2 illustrates another system for pelletizing polymer products.

[0010] Reference will now be made in detail to various embodiments, some embodiments of which are illustrated in the accompanying drawings.

DETAIEED DESCRIPTION

[0011] The present disclosure is directed to providing reliable and inexpensive estimates of polymer flow using typically installed equipment and correction factors.

[0012] The term “polymer” refers to a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The generic term polymer thus embraces the term “homopolymer,” usually employed to refer to polymers prepared from only one type of monomer as well as “copolymer” which refers to polymers prepared from two or more different monomer types.

[0013] “Polyethylene” or “ethylene-based polymer” refers to polymers comprising greater than 50% by weight derived from ethylene monomer. This includes polyethylene homopolymers or copolymers (meaning units derived from two or more monomer types). Common forms of polyethylene known in the art include Tow-density polyethylene (EDPE); Einear Low-density polyethylene (LLDPE); Ultra Low-density polyethylene (ULDPE); Very Low-density polyethylene (VLDPE); single-site catalyzed Linear Low-density polyethylene, including both linear and substantially linear low-density polymers (m-LLDPE); Medium Density Polyethylene (MDPE); and High-Density Polyethylene (HDPE).

[0014] The term “LDPE” may also be referred to as “high-pressure ethylene polymer” or “highly branched polyethylene” and is defined to mean that the polymer is partly or entirely homopolymerized or copolymerized in autoclave or tubular reactors at pressures above 14,500 psi (100 MPa) with the use of free-radical initiators, such as peroxides (see, for 86153-WO-PCT/DOW 86153 WO

4 example, U.S. Patent No. 4,599,392, which is hereby incorporated by reference in its entirety). LDPE polymers typically have a density in the range of 0.916 g/cm³ to 0.930 g/cm³. [0015] The term “LLDPE,” includes polymer made using Ziegler-Natta catalyst systems as well as polymer made using single-site catalysts, including, but not limited to, bismetallocene catalysts (sometimes referred to as “m-LLDPE”), phosphinimine, and constrained geometry catalysts, and polymers made using post-metallocene, molecular catalysts, including, but not limited to, bis(biphenylphenoxy) catalysts (also referred to as polyvalent aryloxy ether catalysts). LLDPE includes linear, substantially linear, or heterogeneous ethylene-based copolymers. LLDPEs contain less long chain branching than LDPEs and include the substantially linear ethylene polymers, which are further defined in U.S. Patent No. 5,272,236, U.S. Patent No. 5,278,272, U.S. Patent No. 5,582,923 and U.S. Patent No. 5,733,155 each of which are incorporated herein by reference in their entirety; the homogeneously branched linear ethylene polymer compositions such as those in U.S. Patent No. 3,645,992 which is incorporated herein by reference in its entirety; the heterogeneously branched ethylene polymers such as those prepared according to the process disclosed in U.S. Patent No. 4,076,698 which is incorporated herein by reference in its entirety; and blends thereof such as those disclosed in U.S. Patent No. 3,914,342 and U.S. Patent No. 5,854,045 which are incorporated herein by reference in their entirety. The LLDPE polymers can be made via gas-phase, solution-phase, or slurry polymerization or any combination thereof, using any type of reactor or reactor configuration known in the art.

[0016] The term “HDPE” generally refers to polyethylene having densities greater than about 0.940 g/cm³ and up to about 0.970 g/cm³, which are generally prepared with Ziegler- Natta catalysts, chrome catalysts or single-site catalysts including, but not limited to, substituted mono- or bis-cyclopentadienyl catalysts (typically referred to as metallocene), constrained geometry catalysts, phosphinimine catalysts and polyvalent aryloxyether catalysts (typically referred to as bisphenyl phenoxy).

[0017] Referring now to FIG. 1, a system 100 may be used to pelletize polymer products. The system 100 may comprise a polymer tank 102 in fluid communication a polymer feeder 104. The polymer feeder 104 may be in direct fluid communication with an extruder 108. The extruder 108 may be in fluid communication with a gear pump 106. Furthermore, an additive tank 112 may be in fluid communication with an additive feeder 110. The additive feeder 110 may be in fluid communication with the extruder 108. A tank 114 may be downstream of, 86153-WO-PCT/DOW 86153 WO

5 and in fluid communication with the gear pump 106. A pellet feeder 116 may be downstream of, and in fluid communication with the gear pump 106.

[0018] The extruder 108 may be any conventional extruder type, such as a single screw extruder, or a multi-screw extruder, such as a twin screw extruder, or a continuous mixer. Continuous mixers are commercially available from Farrel Corporation, Ansonia, Connecticut under their FCM and UMSD designations, and from Kobe Steel, Ltd., Takasago, Japan under their KCM and LCM designations, and from The Japan Steel Works, Ltd., Hiroshima, Japan under their CMP, CMPX, and CIMP designations. Twin screw extruders are commercially available from Coperion GmbH, Stuttgart, Germany under their ZSK designation.

[0019] One or more of the polymer feeder 104, the additive feeder 110, and the pellet feeder 116 may be volumetric feeders. Generally, a volumetric feeder refers to any feeder which measures and dispenses a particular volume of feed. In embodiments, the volumetric feeder may be a rotary feeder.

[0020] A gear pump refers to a pump that moves a fluid by repeatedly enclosing a fixed volume using interlocking cogs or gears, transferring it mechanically using a cyclic pumping action.

[0021] Referring now to FIG. 2, a system 200 may be substantially the same as the system 100 except that system 200 may not include the gear pump 106. In such embodiments, the polymer feeder 104 may be in direct communication with the extruder 108. A tank 114 may be downstream of, and in fluid communication with the extruder 108. A pellet feeder 116 may be downstream of, and in fluid communication with the extruder 108.

[0022] A process for pelletizing polymer products may comprise extruding a first polymer with one or more additives to form pellets in an extruder 108. The pellets may comprise a blend of polymer and one or more additives.

[0023] A polymer feeder 104, may transfer polymer from the polymer tank 102 to the extruder 108. In embodiments, the extruder 108 may be upstream of the gear pump 106, where a gear pump 106 is used. The polymer in the polymer tank 102 may comprise a granular polymer, or a powdered polymer, or a pelletized polymer. The granular polymer may comprise discrete particles having an average particle size of from 356 micron (0.014 inch) to 1219 micron (0.048 inch). The polymer may comprise an ethylene based polymer. 86153-WO-PCT/DOW 86153 WO

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[0024] In some embodiments, the one or more additives are passed to the extruder 108 by one or more additive feeders 110. The one or more additives may comprise primary antioxidants, secondary antioxidants, anti-block agents, polymer processing aids, ultraviolet stabilizers, ultraviolet absorbers, lubricants, thermal stabilizers, slip agents, anti-stat agents, processing lubricants, neutralizers, master batches, pre-blends, and the like.

[0025] The process may further comprise passing the pellets from the extruder 108, to a gear pump 106 if installed, to a tank 114, and then from the tank 114 to a pellet feeder 116. Generally, the pellet feeder 116 may be operable to empty pellets from the tank 114.

[0026] The process may further comprise measuring the weight of pellets produced during a time period T. Measuring the weight of pellets produced in a given time may comprise pausing the pellet feeder 116 while the extruder 108 is still forming pellets; obtaining an initial weight (W_;) of the tank; when the pellet feeder is restarted, both the time period T after Wi is obtained and the final weight (Wf) of the tank 114 are obtained. The weight of pellets produced is thus Wf-Wi and the rate of pellets produced is f .

T

[0027] In embodiments, the extruder 108 may be continuously forming pellets for from 10 minutes to 20 minutes, such as about 15 minutes before the pellet feeder 116 is stopped and Wi is obtained.

[0028] Time period T, for which the pellet feeder 116 is stopped, may be from at least one (1) minute to around ten (10) minutes after Wi is obtained before Wf is obtained.

[0029] The process may comprise calculating the amount and/or rate of pellets produced. A theoretical mass flow rate (Ma) of the pellets may be calculated according to Equation la and/or lb. A theoretical mass transferred (Ma) of the pellets may be calculated according to Equation 1c and/or Id. A theoretical mass flow rate (Mht) of the pellets may be calculated according to Equation le and/or If. In embodiments, or more than one of Ma

Equation la: Ma = gear pump speed x gear pump volumetric efficiency x melt density x gear pump volume per revolution;

Equation lb: Ma = polymer feeder speed x polymer feeder volumetric efficiency x bulk density x polymer feeder volume per revolution; 86153-WO-PCT/DOW 86153 WO

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Equation 1c: M_t = gear pump speed x gear pump volumetric efficiency x melt density x gear pump volume per revolution x T;

Equation Id: Mtt = polymer feeder speed x polymer feeder volumetric efficiency x bulk density x polymer feeder volume per revolution x T; and

Equation le: Mht = number of gear pump revolutions during time period T x gear pump volumetric efficiency x melt density x gear pump volume per revolution; and

Equation If: Mht = number of polymer feeder revolutions during time period T x polymer feeder volumetric efficiency x bulk density x polymer feeder volume per revolution; [0030] In Equations la- If, gear pump speed refers to the speed of the gear pump in revolutions per minute (rpm). Gear pump volume per revolution refers to the theoretical volume moved by the gear pump, per revolution of the gear pump. Gear pump volumetric efficiency refers to the average ratio of actual volume moved by the gear pump over theoretical volume moved by the gear pump, per revolution of the gear pump. In embodiments, the gear pump volumetric efficiency may be from 60% to 100%, such as from 60% to 70%, from 70% to 80%, from 80% to 90%, from 90% to 100%, or any combination of two or more of these ranges.

[0031] Polymer feeder speed refers to the speed of the polymer feeder in revolutions per minute (rpm). Polymer feeder volume per revolution refers to the theoretical volume moved by the polymer feeder, per revolution of the polymer feeder. Polymer feeder volumetric efficiency refers to the average ratio of actual volume moved by the polymer feeder over theoretical volume moved by the polymer feeder, per revolution of the polymer feeder. In embodiments, the polymer feeder volumetric efficiency may be from 60% to 100%, such as from 60% to 70%, from 70% to 80%, from 80% to 90%, from 90% to 100%, or any combination of two or more of these ranges.

[0032] Density of solid materials is calculated using the following formula: D = M / V, where: D represents density (weight per unit volume); where V represents container volume; where M represents weight of the full container. Density of solids does not include pore space (air space). Bulk density is the density of a volume of particles (e.g., pellets, granular polymers) as they exist naturally; i.e., it includes pore space (air space), solid particles, etc. Density of molten polymer, i.e., melt density, refers to the average density of the polymer. In 86153-WO-PCT/DOW 86153 WO

8 embodiments, the melt density may be from 500 g/cm³ to 1,500 g/cm³, such as from 500 g/cm³ to 750 g/cm³, from 750 g/cm³ to 1,000 g/cm³, from 1,000 g/cm³ to 1,250 g/cm³, from 1,250 g/cm³ to 1,500 g/cm³, or any combination of two or more of these ranges. Melt density can be determined using the method described in Capt, L., and Kamal, M.R., paper entitled “The Pressure- Volume-Temperature Behavior Polyethylene Melts”, International Polymer Processing, Vol. 15, No. 1, pp. 83-94, 2000.

[0033] Generally, a gear pump 106 and/or an extruder 108 may be flood fed or starved fed. Generally, being flood fed means that excess material is supplied to the inlet of the device and the rate limiting step is the device itself. Conversely, being starved fed means that less material is supplied to the inlet of the device than the device can handle and thus, the rate limiting step is material delivery. Generally, it may be preferable to base the calculations on the speed of a flood fed device as the speed of the flood fed device will better reflect the amount of material transferred.

[0034] The process further comprises calculating a correction factor Cfa or Cfb or Cf_c according to Equation 2a or 2b or 2c.

Mf_t

Equation 2a: Cfa =

>

Equation

[0035] In embodiments, Cfa and Cfb and Cf_c may be limited to the range of from 0.8 to 1.2, such as from 0.8 to 0.9, from 0.9 to 1.0, from 1.0 to 1.1, from 1.1 to 1.2, or any combination of two or more of these ranges. In such embodiments where the correction factor is limited, if the calculated correction factor is greater than 1.2, a value of 1.2 is used. Similarly, where the correction factor is limited, if the calculated correction factor is less than 0.8, a value of 0.8 is used.

[0036] In some embodiments, the correction factor may be averaged over a series of pauses of the pellet feeder 116. For example, Cfa and Cfb and Cf_c may each be taken as the average of Cfa and Cfb and Cf_c values respectively over at least two pauses of the pellet feeder 116, such 86153-WO-PCT/DOW 86153 WO

9 as at least 3 pauses, at least 4 pauses, or at least 5 pauses of the pellet feeder 116. The pellet feeder 116 may be paused for at least one minute to around 10 minutes for each measurement. The extruder 108 may be operating with the pellet feeder 116 operational for at least 15 minutes between each pause of the pellet feeder 116. In embodiments, the pellet feeder 116 may be stopped and a weight may be determined at least once every 15 minutes to at least once very several hours (e.g., at least every 2 hours, at least every 3 hours, at least every 4 hours, at least every 5 hours, at least every 8 hours, or at least every 10 hours).

[0037] The process further comprises determining the amount of the first polymer, the one or more additives, or both passed to the extruder in response to a predicted mass flow rate (Mf_P) and/or a predicted mass transferred (M_tp) and/or a predicted mass transferred (Mhp) computed by a controller, wherein Mf_P = Ma x Cfa and M_tp = M_tt x Ca and Mh_P = Mht x Cf_c.

[0038] In some embodiments, the controller may then compute the required amount of the first polymer, the one or more additives, or both. The polymer feeder 104 may be responsive to instructions computed by the controller. Additionally, the one or more additive feeders 110 may be responsive to instructions computed by the controller.

[0039] It should be apparent to those skilled in the art that various modifications can be made to the described embodiments without departing from the spirit and scope of the claimed subject matter. Thus, it is intended that the specification cover modifications and variations of the described embodiments provided such modification and variations come within the scope of the appended claims and their equivalences.

[0040] Reference throughout this specification to “one embodiment,” “embodiments,” “certain embodiments,” “some embodiments,” “various embodiments,” “one or more embodiments,” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as “in embodiments,” “in one or more embodiments,” “in certain embodiments,” “in various embodiments,” “in one embodiment,” “in some embodiments,” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, materials, or characteristics described in connection with one embodiment may be combined in any suitable manner in one or more other embodiments. 86153-WO-PCT/DOW 86153 WO

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[0041] While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.

Claims

86153-WO-PCT/DOW 86153 WO 11 CLAIMS

1. A process for pelletizing polymer products comprising: extruding a first polymer with one or more additives to form pellets in an extruder in communication with a polymer feeder, a gear pump, or both; passing the pellets from the extruder to a tank; passing the pellets from the tank to a pellet feeder; pausing the pellet feeder while the extruder is still forming pellets: obtaining an initial weight (W_;) of the tank; and restarting the pellet feeder and obtaining both a time period T after Wi is obtained, and a final weight (Wf) of the tank; calculating: a theoretical mass flow rate (Ma) of the pellets according to Equation la and/or lb; a theoretical mass transferred (M_t) of the pellets according to Equation 1c and/or Id; a theoretical mass flow rate (Mht) of the pellets according to Equation le and/or If; or more than one of these, wherein:

Equation la: Ma= gear pump speed x gear pump volumetric efficiency x melt density x gear pump volume per revolution;

Equation lb: Ma= polymer feeder speed x polymer feeder volumetric efficiency x bulk density x polymer feeder volume per revolution;

Equation 1c: M_tt = gear pump speed x gear pump volumetric efficiency x melt density x gear pump volume per revolution x T; and

Equation Id: M_tt = polymer feeder speed x polymer feeder volumetric efficiency x bulk density x polymer feeder volume per revolution x T; and

Equation le: Mht = number of gear pump revolutions during time period T x gear pump volumetric efficiency x melt density x gear pump volume per revolution; and 86153-WO-PCT/DOW 86153 WO

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Equation If: Mht = number of polymer feeder revolutions during time period T x polymer feeder volumetric efficiency x bulk density x polymer feeder volume per revolution; and calculating a correction factor Cfa or Cfb or Cf_c according to Equation 2a or 2b or 2c:

Equation 2a: Cfa

Equation 2b: Cfb

E > ■quat .i •on 2c .* C'fc determining the amount of the first polymer, the one or more additives, or both passed to the extruder in response to a predicted mass flow rate (Mf_P) and/or a predicted mass transferred (M_tp) and/or a predicted mass transferred (Mh_P) computed by a controller, wherein Mf_P = Ma x Cfa and M_tp = M_t x Cfb and Mh_P = Mht x Cf_c.

2. The process of claim 1, wherein Cfa and Cfb and Cf_c are limited to the range of from 0.8 to 1.2.

3. The process of claim 1 or 2, wherein Cfa and Cfb and Cf_c are taken as the average of Cfa and Cfb and Cf_c values respectively over at least two pauses of the pellet feeder

4. The process of any one of claims 1 to 3, wherein the pellet feeder is stopped at least once every 15 minutes.

5. The process of any one of claims 1 to 4, wherein the pellet feeder is a volumetric feeder or a rotary feeder.

6. The process of any one of claims 1 to 5, wherein the one or more additives comprise primary antioxidants, secondary antioxidants, anti-block agents, polymer processing aids, ultraviolet stabilizers, ultraviolet absorbers, lubricants, thermal stabilizers, slip agents, antistat agents, processing lubricants, neutralizers, master batches, or pre-blends.

7. The process of any one of claims 1 to 6, wherein the melt density is from 500 g/cm³ to 1,500 g/cm³. 86153-WO-PCT/DOW 86153 WO

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8. The process of any one of claims 1 to 7, wherein the gear pump volumetric efficiency is from 60% to 100%.

9. The process of any one of claims 1 to 8, wherein the first polymer is a granular polymer.

10. The process of any one of claims 1 to 9, wherein the one or more additives are passed to the extruder by one or more additive feeders and the one or more additive feeders are responsive to instructions computed by the controller.

11. The process of any one of claims 1 to 10, wherein the first polymer is passed to the extruder by the polymer feeder and wherein the polymer feeder is responsive to instructions computed by the controller.

12. The process of any one of claims 1 to 11, wherein Ma is calculated according to Equation la, M_tt is calculated according to Equation 1c, or Mht is calculated according to Equation le.

13. The process of any one of claims 1 to 12, wherein Ma is calculated according to Equation lb, M_t is calculated according to Equation Id, or Mht is calculated according to Equation If.