Novel polymer modification method using carboxylic acids, radicals, and nitrogen, supported by metallocenes

Abstract

A polymer modification method comprises: (a) contacting a polymer with at least one carboxylic acid selected from C2-C40 aliphatic, aromatic, or cyclic acids; (b) introducing free radicals via thermal, photochemical, or chemical decomposition; (c) adding at least one nitrogen compound; and (d) optionally incorporating a metallocene catalyst. The method enhances polymer properties (tensile strength, elongation, impact resistance) by 25-250%, reduces energy consumption 20-45% compared to virgin production, and enables processing of mixed polymer wastes. Applications include automotive components (20-40% recycled content), food-grade packaging (up to 35% recycled HOPE), construction materials, and waste valorization. The predictive radical chemistry enables controlled property enhancement through mathematical correlation between radical concentration, reaction kinetics, and polymer modification degree.

Description

NOVEL POLYMER MODIFICATION METHOD USING CARBOXYLIC ACIDS, RADICALS, AND NITROGEN, SUPPORTED BY METALLOCENESPriority Application: LVP2024000080 (Latvia, December 17, 2024)FIELD OF THE INVENTION

[0001] This invention relates to novel methods for modifying polymers through the synergistic use of carboxylic acids, free radicals, nitrogen compounds, and optionally metallocene catalysts. More specifically, the invention provides processes for enhancing the properties of both virgin and recycled polymers while reducing energy consumption and enabling the processing of mixed polymer waste streams.BACKGROUND OF THE INVENTION

[0002] The polymer industry faces mounting challenges in recycling post-consumer and industrial polymer waste. Conventional mechanical recycling degrades polymer properties through chain scission, oxidation, and contamination, limiting the use of recycled content in high-performance applications.

[0003] Current polymer modification approaches suffer from several limitations:

[0004] Chemical modification methods (e.g., grafting, crosslinking) often require harsh conditions (high temperatures, aggressive chemicals, extended reaction times) that further degrade polymer chains and increase costs.

[0005] Mechanical blending with virgin polymers dilutes recycled content and provides limited property enhancement.

[0006] Compatibilization techniques for mixed polymer wastes typically rely on expensive compatibilizers and fail to address fundamental property degradation.

[0007] Radical chemistry approaches lack predictive control over modification degree and property outcomes.Analysis of Prior Art

[0008] U.S. Pat. No. 5,539,067 (Toyota) discloses acid-modified polypropylene for automotive applications but does not teach radical chemistry control, nitrogen compound synergy, or metallocene catalysis.

[0009] U.S. Pat. No. 6,846,851 (ExxonMobil) describes metallocene-catalyzed polyolefin production but focuses on polymerization rather than post-production modification of degraded or recycled polymers.

[0010] EP 0 716 121 (Borealis) teaches radical grafting of maleic anhydride onto polyolefins for compatibilization but does not disclose the synergistic combination with nitrogen compounds or predictive radical chemistry control.

[0011] U.S. Pat. No. 7,135,528 (Dow) describes polymer modification using peroxides but lacks the predictive mathematical framework for controlled radical reactions and does not teach metallocene synergy.

[0012] None of the prior art teaches or suggests:

[0013] The synergistic combination of carboxylic acids, controlled radical chemistry, nitrogen compounds, and metallocene catalysts.

[0014] Predictive control of polymer modification through mathematical correlation between radical concentration, reaction kinetics, and property enhancement.

[0015] Methods enabling simultaneous processing and upgrading of mixed polymer waste streams without pre-sorting.

[0016] Energy reduction of 20-45% compared to virgin polymer production while achieving property enhancement.SUMMARY OF THE INVENTION

[0017] The present invention overcomes the limitations of prior art by providing novel polymer modification methods that synergistically combine carboxylic acids, controlled radical chemistry, nitrogen compounds, and optionally metallocene catalysts. The invention enables:

[0018] Predictive control of polymer modification through mathematical correlation between radical concentration, reaction kinetics, and property enhancement.

[0019] Property enhancement of 25-250% in tensile strength, elongation, and impact resistance for both virgin and recycled polymers.

[0020] Energy reduction of 20-45% compared to virgin polymer production.

[0021] Processing of mixed polymer waste streams (automotive shredded residue, packaging waste) without pre-sorting.

[0022] Production of high-performance materials from degraded or contaminated polymer feedstocks.DETAILED DESCRIPTION OF THE INVENTIONMethod 1 : Carboxylic Acid Modification

[0023] The polymer is contacted with at least one carboxylic acid selected from C2-C40 aliphatic acids (e.g., acetic, stearic, oleic), aromatic acids (e.g., benzoic, phthalic), and cyclic acids.

[0024] Acid concentration: 0.01 -10 wt% based on polymer weight.

[0025] Processing temperature: 140-280 degrees C depending on polymer melt temperature.

[0026] Residence time: 30 seconds to 15 minutes in extruder or batch mixer.

[0027] The carboxylic acid modifies polymer chain ends and side groups, improving interfacial adhesion and compatibility in blends and composites.Method 2: Predictive Radical Chemistry

[0028] Free radicals are introduced via:

[0029] Thermal decomposition of organic peroxides (e.g., dicumyl peroxide, benzoyl peroxide) at 0.01 -2.0 wt%.

[0030] Photochemical initiation using UV radiation (200-400 nm).

[0031] Chemical decomposition of azo compounds (e.g., AIBN).

[0032] The radical concentration [I] is controlled according to the mathematical relationship: [I] equals [P radical]squared times kt divided by (f times kd)

[0033] Where [P radical] is the propagating radical concentration (mol / L), kt is the termination rate constant (L / mol times s), f is the initiator efficiency (0.3-0.8), and kd is the initiator decomposition rate constant (s to the power of minus 1 ).

[0034] This predictive approach enables controlled modification degree and property outcomes, distinguishing the invention from prior art empirical trial-and-error methods.Method 3: Synergistic Hybrid Compositions

[0035] The invention combines:

[0036] Carboxylic acid modification (Method 1 )

[0037] Radical chemistry (Method 2)

[0038] At least one nitrogen compound: melamine, urea, caprolactam, cyanuric acid, guanidine at 0.1 -5 wt%

[0039] Optional metallocene catalyst: Cp2TiCI2, Cp2ZrCI2, or Cp2HfCI2 at 0.001 -0.5 wt%

[0040] The nitrogen compounds act as chain extenders and branching agents, while metallocene catalysts enhance reaction selectivity and reduce side reactions.

[0041] Synergistic effects yield property enhancements exceeding the sum of individual modifications:

[0042] Tensile strength increase: 40-250% (vs. 15-80% for individual methods)

[0043] Impact resistance: 50-180% (vs. 20-60% for individual methods)

[0044] Elongation at break: 25-120% (vs. 10-40% for individual methods)Processing Equipment and Conditions

[0045] Twin-screw extruder: L / D ratio 36-48, screw speed 200-500 rpm

[0046] Batch mixer: Sigma blade or Banbury mixer, 30-120 minutes

[0047] Reactive extrusion: Multi-zone temperature profile for sequential addition

[0048] Atmosphere: Inert (nitrogen or argon) to prevent oxidative degradationEXAMPLESExample 1 : Automotive Component from ASR

[0049] Automotive shredded residue (ASR) containing 60% PP, 25% PE, 10% ABS, 5% contaminants was processed as follows:

[0050] Ingredients: ASR (85 wt%), stearic acid (1.5 wt%), dicumyl peroxide (0.5 wt%), melamine (2 wt%), Cp2TiCI2 (0.01 wt%), virgin PP (10.99 wt%)

[0051] Processing: Twin-screw extruder, 180-220 degrees C, 300 rpm, residence time 4 minutes, nitrogen atmosphere

[0052] Results: Tensile strength 32 MPa (vs. 18 MPa unmodified ASR), Elongation 85% (vs. 35%), Impact strength 65 kJ / m squared (vs. 28 kJ / m squared), Energy consumption 45% lower than virgin PP production

[0053] Application: Automotive under-hood components with 30% recycled content meeting OEM specificationsExample 2: Food-Grade Packaging from Mixed HDPE

[0054] Post-consumer HDPE bottles (various colors, contaminated with labels) were processed:

[0055] Ingredients: Recycled HDPE (65 wt%), oleic acid (2 wt%), benzoyl peroxide (0.3 wt%), urea (1.5 wt%), virgin HDPE (31 .2 wt%)

[0056] Processing: Reactive extrusion, 160-200 degrees C, 400 rpm, 3 minutes

[0057] Results: MFI 0.8 g / 10min (suitable for blow molding), Density 0.958 g / cm cubed, FDA compliance achieved for indirect food contact, Odor and color significantly improved

[0058] Application: Detergent bottles with 35% recycled content meeting FDA food-contact standardsExample 3: High-Performance Construction Material

[0059] Industrial PP waste (degraded from multiple reprocessing cycles) was upgraded:

[0060] Ingredients: Degraded PP (75 wt%), maleic anhydride (3 wt%), dicumyl peroxide (0.8 wt%), caprolactam (2.5 wt%), Cp2ZrCI2 (0.02 wt%), virgin PP (18.68 wt%)

[0061] Processing: Batch mixer, 190 degrees C, 45 minutes, inert atmosphere

[0062] Results: Flexural modulus 2200 MPa (250% increase vs. degraded PP), Notched Izod impact 12 kJ / m squared (180% increase), Heat deflection temperature 105 degrees C (vs. 85 degrees C)

[0063] Application: Exterior building panels with 40% recycled content exceeding virgin PP performanceExample 4: Waste Valorization Economic Analysis

[0064] Cost comparison per metric ton of automotive component grade material:

[0065] Virgin PP production: EUR 1 ,200 / ton raw material + EUR 800 / ton processing = EUR 2,000 / ton

[0066] Invention (Example 1 ): ASR EUR 50 / ton + Chemicals EUR 120 / ton + Processing EUR 350 / ton + Virgin PP blending EUR 130 / ton = EUR 650 / ton

[0067] Net savings: 67.5% cost reduction

[0068] Carbon footprint reduction: 3.2 kg CO2e / kg (virgin PP) vs. 0.9 kg CO2e / kg (invention) = 72% reduction

[0069] Landfill diversion: 15,000 tons ASR / year per production lineExample 5: Radical Concentration Predictive Control

[0070] To achieve 150% tensile strength improvement in recycled PP:

[0071] Target [P radical] = 5 times 10 to the minus 6 mol / L

[0072] kt = 2 times 10 to the 8 L / mol times s (PP at 200 degrees C)

[0073] f = 0.6 (dicumyl peroxide efficiency)

[0074] kd = 5 times 10 to the minus 4 s to the minus 1 (dicumyl peroxide at 200 degrees C)

[0075] Required [I] = (5 times 10 to the minus 6) squared times (2 times 10 to the 8) divided by (0.6 times 5 times 10 to the minus 4) = 1 .67 times 10 to the minus 2 mol / L

[0076] This corresponds to 0.42 wt% dicumyl peroxide (MW = 270 g / mol)

[0077] Result: Actual tensile strength improvement 148% plus or minus 7%, demonstrating predictive accuracyExample 6: Metallocene Catalyst Selection

[0078] Three metallocene catalysts were compared for modification of recycled LDPE:

[0079] Cp2TiCI2 (0.01 wt%): Tensile strength +65%, Elongation +42%, Side reaction byproducts 3.2 wt%

[0080] Cp2ZrCI2 (0.01 wt%): Tensile strength +72%, Elongation +58%, Side reaction byproducts 1 .8 wt%

[0081] Cp2HfCI2 (0.01 wt%): Tensile strength +78%, Elongation +61%, Side reaction byproducts 1 .1 wt%

[0082] Conclusion: Hafnocene provides optimal selectivity and property enhancement but costs 4 times more than zirconocene; zirconocene offers best performance / cost balanceExample 7: Nitrogen Compound Synergy

[0083] Effect of nitrogen compound addition to acid / radical modified recycled PP:

[0084] Acid + Radical only: Tensile strength +48%, MFI 12 g / 10min

[0085] + Melamine (2 wt%): Tensile strength +125%, MFI 3.5 g / 10min (chain extension)

[0086] + Urea (1 .5 wt%): Tensile strength +95%, MFI 5.2 g / 10min (moderate chain extension)

[0087] + Caprolactam (2.5 wt%): Tensile strength +110%, MFI 4.1 g / 10min, improved thermal stability

[0088] Conclusion: Nitrogen compounds provide synergistic chain extension and branching, with melamine showing strongest effectsExample 8: Carboxylic Acid Coverage Comparison

[0089] Different carboxylic acids were tested for modification of recycled HDPE:

[0090] Acetic acid (C2, 2 wt%): Tensile strength +28%, Poor thermal stability

[0091] Stearic acid (C18, 1 .5 wt%): Tensile strength +52%, Excellent processing, Good thermal stability

[0092] Oleic acid (C18:1 , 2 wt%): Tensile strength +58%, Excellent compatibilization for blends

[0093] Benzoic acid (aromatic, 1 .8 wt%): Tensile strength +45%, Enhanced UV stability

[0094] Conclusion: Long-chain aliphatic acids (C16-C20) provide optimal balance of property enhancement, processing, and thermal stability

Claims

Example 9: Radical Source Selection Validation[0095] Different radical sources were evaluated for modification of recycled PP at 200 degrees C:[0096] Dicumyl peroxide (0.5 wt%): Half-life 2 min at 200 degrees C, Property enhancement +145%, Minimal odor, Excellent stability[0097] Benzoyl peroxide (0.5 wt%): Half-life 0.5 min at 200 degrees C, Property enhancement +98%, Strong odor, Premature decomposition risk[0098] AIBN (0.5 wt%): Half-life 5 min at 200 degrees C, Property enhancement +112%, Nitrogen generation (foaming potential)[0099] UV radiation (254 nm, 15 W / m squared): Surface modification only, Bulk properties unchanged, Limited penetration[0100] Conclusion: Dicumyl peroxide provides optimal balance of reaction rate, property enhancement, stability, and processability for bulk polymer modificationExample 10: Industrial-Scale Mixed Waste Processing[0101] A 5,000 kg / day industrial line processed mixed packaging waste (HDPE 40%, PP 35%, LDPE 20%, contaminants 5%):[0102] Feed preparation: Shredding, metal separation, no polymer sorting required[0103] Modification: Stearic acid 1.8 wt%, dicumyl peroxide 0.6 wt%, melamine 2.2 wt%, Cp2ZrCI2 0.015 wt%[0104] Processing: Twin-screw extruder (L / D 48), 180-210 degrees C, 350 rpm, 4.5 min residence time[0105] Output: 4,750 kg / day pellets (95% yield)[0106] Properties: Tensile strength 28 MPa, MFI 2.8 g / 10min, suitable for injection molding of non-critical parts[0107] Economics: Chemical costs EUR 145 / ton, Processing EUR 280 / ton, Total production cost EUR 475 / ton vs. EUR 1 ,450 / ton virgin polymer blend[0108] Environmental: Energy consumption 4.2 MJ / kg (55% lower than virgin), CO2e 1.1 kg / kg (65% reduction)[0109] Conclusion: The invention enables profitable, environmentally beneficial processing of mixed polymer waste without pre-sorting, producing materials suitable for demanding applications at 67% cost savingsCLAIMS1. A method for modifying a polymer, comprising: (a) contacting said polymer with at least one carboxylic acid selected from the group consisting of C2-C40 aliphatic carboxylic acids, aromatic carboxylic acids, and cyclic carboxylic acids, wherein said carboxylic acid is present at 0.01 to 10 weight percent based on the weight of said polymer; (b) introducing free radicals into said polymer by thermal decomposition, photochemical initiation, or chemical decomposition of a radical source; (c) adding at least one nitrogen compound selected from the group consisting of melamine, urea, caprolactam, cyanuric acid, and guanidine, wherein said nitrogen compound is present at 0.1 to 5 weight percent based on the weight of said polymer; (d) optionally incorporating a metallocene catalyst selected from the group consisting of Cp2TiCI2, Cp2ZrCI2, and Cp2HfCI2, wherein said metallocene catalyst is present at 0.001 to 0.5 weight percent based on the weight of said polymer; and (e) processing said polymer under conditions effective to enhance at least one property selected from tensile strength, elongation at break, and impact resistance by at least 25 percent compared to unmodified polymer, wherein said polymer comprises at least one polyolefin selected from polyethylene, polypropylene, polybutene, and copolymers thereof.2 A method for predictive modification of a polymer using radical chemistry, comprising: (a) determining a target propagating radical concentration [P radical] required to achieve a desired degree of polymer modification; (b) calculating a required initiator concentration [I] according to the mathematical relationship: [I] equals [P radical] squared times kt divided by (f times kd), wherein kt is a termination rate constant, f is an initiator efficiency factor, and kd is an initiator decomposition rate constant; (c) incorporating said initiator at said calculated concentration [I] into said polymer; (d) processing said polymer under conditions effective to decompose said initiator and generate said target propagating radical concentration [P radical]; and (e) achieving said desired degree of polymer modification with a prediction accuracy of plus or minus 15 percent.3 A synergistic polymer composition comprising: (a) a polymer selected from the group consisting of polyolefins, polyesters, polyamides, and blends thereof, wherein at least 20 weight percent of said polymer is derived from recycled sources; (b) a carboxylic acid residue present at 0.05 to 8 weight percent based on the total composition weight; (c) a radical-induced modification resulting in at least 10 percent increase in molecular weight; (d) a nitrogen compound residue present at 0.2 to 4 weight percent based on the total composition weight; and (e) optionally a metallocene catalyst residue present at 0.002 to 0.3 weight percent based on the total composition weight, wherein said composition exhibits at least one property selected from tensile strength, impact resistance, and elongation at break that is enhanced by at least 40 percent compared to the unmodified recycled polymer.4 The method of claim 1 , wherein said processing comprises extrusion at a temperature of 140 degrees C to 280 degrees C with a residence time of 30 seconds to 15 minutes.5 The method of claim 1 , wherein said polymer is a mixed polymer waste stream comprising at least two different polymers without pre-sorting, and wherein said method produces a composition suitable for automotive components, packaging materials, or construction materials.6 The method of claim 2, wherein said initiator is selected from the group consisting of dicumyl peroxide, benzoyl peroxide, and azobisisobutyronitrile, and wherein said processing temperature is selected to provide said initiator with a half-life of 0.5 to 10 minutes.7 The method of claim 1 , wherein said carboxylic acid is selected from stearic acid, oleic acid, and maleic anhydride, said nitrogen compound is melamine, and said metallocene catalyst is Cp2ZrCI2.8 The composition of claim 3, wherein said polymer comprises automotive shredded residue (ASR) containing polyolefins, and wherein said composition exhibits tensile strength of at least 30 MPa and impact resistance of at least 60 kJ / m squared.9 The method of claim 1 , wherein said method reduces energy consumption by 20 to 45 percent compared to production of virgin polymer with equivalent properties.

10. The composition of claim 3, wherein said recycled polymer comprises at least 30 weight percent of the total polymer content and wherein said composition meets food-contact compliance standards or automotive OEM specifications.