Thermoplastic cellulosic fiber granules useful as infill materials for artificial turf

Abstract

An artificial turf system has polymeric turf fibers resembling grass, and infill particles interspersed among said turf fibers. At least some of the infill comprises synthetic composite particles containing a thermoplastic polymer and cellulosic fibers, in which thermoplastic polymer is a matrix that binds together the other components of each synthetic particle into a composite particle.

Claims

1. An artificial turf system, wherein said system comprises: polymeric, upright turf fibers resembling grass; and infill interspersed among said turf fibers; wherein at least some of said infill comprises synthetic composite particles wherein: said synthetic composite particles comprise a thermoplastic polymer, cellulosic fibers, calcium carbonate, maleated polyethylene, an ultraviolet absorber, and zinc borate; said thermoplastic polymer is between about 10% and about 90% of said synthetic composite particles by mass; said thermoplastic polymer comprises high-density polyethylene, low-density polyethylene or both; said cellulosic fibers are between about 10% and about 80% of said synthetic composite particles by mass; said cellulosic fibers comprise pine wood shavings, pine wood sawdust, or both; said calcium carbonate is between 5% and 30% of said synthetic composite particles by mass; said maleated polyethylene is between 0.5% and 2% of said synthetic composite particles by mass; said ultraviolet absorber is between 0.5% and 2% of said synthetic composite particles by mass; said zinc borate is between 0.5% and 2% of said synthetic composite particles by mass; said thermoplastic polymer is a matrix that binds together the other components of said synthetic particles into a composite material; and the density of said synthetic composite particles is greater than 1.0 g/cm.sup.3.

2. The system of claim 1, wherein said thermoplastic polymer additionally comprises one or more polymers selected from the group consisting of acrylonitrile butadiene styrene, polymethylmethacrylate, acrylonitrile, polytetrafluoroethylene, polyvinylidene fluoride, nylon 6, nylon 66, polycarbonate, polybutylene terephthalate, polyethylene terephthalate, polyetheretherketone, polyetherimide, polyimide, polyphenylene oxide, polyphenylene sulfide, polypropylene, polystyrene, polysulfone, polyethersulfone, polyvinyl chloride, a starch-based polymer, polylactic acid, poly-3-hydroxybutyrate, polyamide 11, and bio-derived polyethylene.

3. The system of claim 1, wherein said synthetic composite particles additionally comprise one or more fibers, particles, or flakes selected from the group consisting of softwoods other than pine, maple, oak, other hardwoods, bamboo, rattan, rice straw, wheat straw, rice husk, bagasse, cotton stalk, jute, hemp, flax, kenaf, milkweed, grass, banana tree, coconuts, walnut shells, pecan shells, other tree nut shells, and peanut shells.

4. The system of claim 1, wherein said synthetic composite particles additionally comprise between 0.1% and 10% by mass of a biocide other than zinc borate.

5. The system of claim 4, wherein said biocide comprises one or more compounds or elements selected from the group consisting of calcium borate; boric acid; copper; zinc; and silver.

6. The system of claim 1, wherein said synthetic composite particles additionally comprise between 1% and 50% by mass of a fire retardant other than zinc borate.

7. The system of claim 6, wherein said fire retardant comprises one or more compounds selected from the group consisting of aluminum trihydroxide, magnesium dihydroxide, ammonium polyphosphate, antimony trioxide; silicon dioxide, silsesquioxanes, silicon nanoparticles, montmorillonite clays, other silicon-containing clays, triphenyl phosphate, halogenated organophosphorus compounds, other organophosphorus compounds, ammonium polyphosphate, bromo-organic compounds, chloro-organic compounds, fluoro-organic compounds, melamines, carbon nanotubes, alumino-silicates, boroxiloxanes, organoclays, zinc chloride, expandable flake graphite intercalations, ammonium borate, ammonium sulphate, ammonium chloride, boric acid, and sodium borate.

8. The system of claim 1, wherein said synthetic composite particles additionally comprise between 0.1% and 20% by mass of a bonding agent.

9. The system of claim 8, wherein said bonding agent comprises one or more compounds selected from the group consisting of stearic acid, organo-titanates, maleated ethylenes, maleic anhydride, styrene/ethylene/butylene/styrene block copolymer, ethylene/propylene/diene terpolymer, ethylene/octene copolymer, ethylene/methyl acrylate copolymer, ethylene/butyl acrylate/glycidyl methacrylate copolymer, poly(ethylene-co-methacrylic acid), and maleated ethylene/propylene elastomer.

10. The system of claim 1, wherein said synthetic composite particles additionally comprise one or more compounds or compositions selected from the group consisting of mica, talc, barite, and ceramics.

11. The system of claim 1, wherein said calcium carbonate comprises oyster shell.

12. The system of claim 1, wherein said synthetic composite particles additionally comprise between 5% and 20% by mass of magnesium hydroxide.

13. The system of claim 1, wherein said synthetic composite particles are between 6 mesh and 35 mesh (i.e., between 0.5 mm and 3.4 mm).

14. The system of claim 1, wherein said infill additionally comprises particles selected from the group consisting of walnut shell fragments, coconut shell fragments, cypress wood flakes, cedar wood flakes, other wood flakes, ground composites of wood and plastic, ground composites of other natural cellulosic fibers and plastic, ground particleboard of wood and plastic, ground particleboard of other natural cellulosic fibers and plastic.

Description

MODES FOR CARRYING OUT THE INVENTION

(1) To facilitate a better understanding of the present invention, the following examples of specific embodiments are given. These examples should not be read to limit the scope of the invention. Unless otherwise stated, all percentages given in the specification and claims are percentages by weight (or mass).

Example 1. Thermoplastic Cellulosic-Fiber Granule Composite One (TCFG1)

(2) Thermoplastic cellulosic-fiber granule composite one (TCFG1) was created with recycled film-grade low-density polyethylene (38%), 20-mesh wood pine fiber from American Wood Fiber Company, Madison, Wis. (40%), precipitated calcium carbonate with a mean particle diameter of about 20 microns (20%), and 2% maleated polyethylene as a bonding agent. The components were compounded with a counter-rotating, CTSE-V/MARKII twin-screw extruder (C.W. Brabender Instruments Inc., South Hackensack, N.J., USA) at a screw rotation speed of 50 rpm at a temperature profile of 140, 160, 170, and 170 C. The extrudates were quenched in a cold water bath and were then granulated into particulate form.

Example 2. Thermoplastic Cellulosic-Fiber Granule Composite Two (TCFG2)

(3) Thermoplastic cellulosic-fiber granule composite two (TCFG2) was created with mixed recycled high density polyethylene (25%), 8-mesh wood pine fiber from American Wood Fiber Company, Madison, Wis. (50%), calcium carbonate (23%), and 2% maleated polyethylene as a bonding agent. The materials were compounded at selected proportions through a Micro-27 extruder from American Leistritz Extruder Corporation (Somerville, N.J., USA) with a temperature profile of 130-150-160-170-180-180-180-180-180-180-180 C. and a screw rotation speed of 100 rpm. The extrudates were cooled in air and then granulated into particulate form.

Example 3. Thermoplastic Cellulosic-Fiber Granule Composite Three (TCFG3)

(4) Thermoplastic cellulosic-fiber granule composite three (TCFG3) was created with virgin high density polyethylene (39%), 10-mesh wood pine fiber from American Wood Fiber Company, Madison, Wis. (50%), zinc stearate-based lubricant (6%), maleated polyethylene as a bonding agent (4%), and zinc borate (1%). The lubricant was used to enhance the flow of the polymer-fiber mixture to better shape the composite. Zinc borate was used as a biocide to inhibit mold, decay, and termite attacks. The materials were compounded at selected proportions with a Micro-27 extruder from American Leistritz Extruder Corporation (Somerville, N.J., USA) with a temperature profile of 130-150-160-170-180-180-180-180-180-180-180 C. and a screw rotation speed of 100 rpm. The extrudates were cooled in air and then granulated into pellet form.

Example 4. Thermoplastic Cellulosic-Fiber Granule Composite Four (TCFG4)

(5) Thermoplastic cellulosic-fiber granule composite four (TCFG4) was created with mixed recycled high density polyethylene (25%), wood shavings from a wood planer (50%), and calcium carbonate (25%). The materials were compounded at selected proportions with a commercial scale, twin-screw extrusion machine at 180 C. and a screw rotation speed of 100 rpm. The extrudates were cooled in air and then granulated into particulate form.

Example 5. Thermoplastic Cellulosic-Fiber Granule Composite Five (TCFG5)

(6) Thermoplastic cellulosic-fiber granule composite five (TCFG5) was created with virgin high density polyethylene (30%), wood fiber (55%), maleated polyethylene (MAPE) (2%), zinc stearate lubricant (5%), talc (5%), a UV absorber (Tinuvin 783) (2%), and colorant (1%). The materials were compounded at selected proportions through a commercial scale twin-screw extrusion machine at 180 C. and a screw rotation speed of 100 rpm. The composite was extruded into air, and then granulated into particles.

(7) TCFG5 is a preferred formulation. Its cost could perhaps be reduced somewhat by lowering the amount of MAPE or UV absorber, or by increasing the amount of talc in the formulation, or by adding zinc borate. These modifications will be tested to find an optimal formulation that retains the beneficial properties of TCFG5 while lowering the overall cost.

Example 6. Thermoplastic Cellulosic-Fiber Granule Composite Six (TCFG6)

(8) Thermoplastic cellulosic-fiber granule composite six (TCFG6) was created with virgin high density polyethylene (31.6%), wood fiber (50.5%), maleated polyethylene (3.2%), zinc stearate lubricant (4.7%), and magnesium hydroxide (flame retardant) (10%). The materials were compounded in the selected proportions with a commercial-scale, twin-screw extrusion machine at 180 C. and a screw rotation speed of 100 rpm. The composite was extruded into air, and then granulated into particles.

Example 7. Thermoplastic Cellulosic-Fiber Granule Composite Seven (TCFG7)

(9) sample was taken from a new, commercially-prepared, high-quality, 25-year-warranty, wood-plastic composite (CWPC) blend. The commercially-prepared composite was estimated (based both on analysis in our laboratory and on communications with the manufacturer) to contain about 30% plastics (10% virgin HDPE and 20% recycled LDPE), 54% wood fiber, 10% talc, and about 6% other processing additives such as maleated polyethylene (MAPE), zinc stearate lubricant, UV absorber, and colorant. The CWPC board was processed into smaller pieces and then granulated to pass a US 8-mesh screen (2.4 mm). The particles were screened using a US 35 mesh screen (0.5 mm) to remove fines. The particles passing the 8-mesh screen and retained by the 35-mesh screen were used as infill materials.

(10) Many high-quality commercial wood-plastic composites have generally similar compositions, although the details vary from one to another. Many recycled commercial wood-plastic composite boards may therefore be used in preparing the infills of this invention, with reprocessing and additional additives incorporated as needed to provide the desired material properties and uniformity. For example, some commercial composite boards do not include a coupling agent; they may or may not incorporate a biocide such as zinc borate. Commercial composite boards are typically formed under high extrusion pressure, leading to densities greater than 1 g/cm.sup.3. When purpose-made infill materials are made at lower extrusion pressures, unless countervailing steps are taken the density can end up below 1 g/cm.sup.3; and in such a case the formulation (e.g., higher density mineral additives) or extrusion conditions (e.g., higher pressure) can be modified to achieve the desired density above 1 g/cm.sup.3.

Examples 8-15. Characterization of Composite Properties

(11) The properties of the composites of Examples 1-7 were tested.

(12) Two 40-gram samples of each of the composites TCFG1, TCFG2, TCFG4, TCFG5, and CWPC were compression-molded at 170 C. to produce two plates of each of the composites, each measuring approximately 100 mm152 mm5 mm. Test samples for measuring mechanical properties of the composites were machined from these plates.

(13) Granules of TCFG3 were extruded through a Micro-27 extruder (American Leistritz Extruder Corporation, Somerville, N.J., USA) with a temperature profile of 130-150-160-170-180-180-180-180-180-180-180 C. and a screw rotation speed of 60 rpm to make an extruded composite with cross-sectional dimensions of 50 mm12.5 mm, from which test samples were machined for measuring mechanical properties.

(14) Flexural properties of the composite samples were measured according to ASTM D790-03 using an INSTRON 5582 Testing Machine (Instron Co., Grove City, Pa., USA). A TINIUS 92T impact tester (Testing Machine Company, Horsham, Pa.) was used for the Izod impact test. All samples were notched at the center point of one long side according to ASTM D256. Material rebound after 20% compression was measured using an INSTRON 5582 machine and a digital caliper, by determining sample thickness both before and after three compression loads had been applied to each of the test samples.

(15) Fire performance was measured with a Stanton Redcroft cone calorimeter (Fire Testing Technology Limited, London, UK) according to the ISO 5660-1 standard. The test sample was placed on a piece of aluminum foil inside a corundum crucible. The crucible was mounted horizontally on a loader, and then exposed to 50 kW/m.sup.2 heat radiation, corresponding to a temperature of about 780 C. on the upper surface of the test sample.

(16) Fungal decay susceptibility was tested for selected composite formulations in accordance with the American Wood Protection Association (AWPA) Standard Method of Testing Wood Preservatives by Laboratory Soil-Block Cultures (E10-12). The brown rot fungus used in these tests was Gloeophylum trabeum. Future tests will also be conducted with the brown rot fungus Postia placenta, and with the white rot fungi Trametes versicolor and Irpex lacteus. The G. trabeum brown rot decay test ran for 12 weeks. Future tests for white rot decay will run for 24 weeks. Samples were sterilized by gamma irradiation prior to testing. Sample weight loss was measured.

(17) Resistance to Formosan subterranean termites was measured for selected composite formulations in accordance with the AWPA E1-13 Standard Method for Laboratory Evaluation to Determine Resistance to Subterranean Termites, single choice method. Test samples measuring 25 mm25 mm5 mm, or 25 mm25 mm12.5 mm were used for the composites; and test samples measuring 25 mm25 mm6 mm were used for southern pine controls. Weight loss and damage ratings were assessed after a 28-day exposure test.

(18) Accelerated artificial UV weathering tests were conducted in a Ci300+ xenon arc-type Weatherometer (Atlas Electric Devices, Wauconda) according to the ASTM D2565-99 (2008) standard. The samples were rotated at 1 rpm around a spray nozzle and a UV source, as specified in the ASTM standard. The weathering times were 500, 1000, and 2000 h. Sample color change and strength loss were measured.

(19) Surface hardness tests were conducted on artificial turf filled with the composite infill materials, based on ASTM F3550-A. A commercial artificial grass turf was used with 64 mm-long grass, at an infill depth of 38 mm with the novel composite particles. Based on these test results, surface hardness Gmax values were obtained.

(20) Table 1 lists selected properties for various composites. The data showed that the composites were strong and durable, providing sufficient strength, impact resistance, compressibility, fire resistance, and biological resistance. The surface hardness data (Gmax value) showed that the infill systems led to acceptable surface hardness for balancing the safety and performanceall based on comparison to typical industrial standards (not shown).

(21) TABLE-US-00001 TABLE 1 Young's Bending Impact Rebound Base Density Modulus Strength Strength Rate.sup.1 Gmax Sample Polymer (g/cm.sup.3) (GPa) (MPa) (kJ/m.sup.2) (%) Value.sup.2 TCFG1 Recycled-LOPE 1.20 1.99 21.01 3.53 19.9 95 TCFG2 Recycled-Mixed- 1.25 1.45 14.15 2.73 23.3 113 HDPE TCFG3.sup.3 Virgin HDPE 1.19 3.32 32.25 3.45 25.6 135 TCFG4 Recycled-Mixed- 1.13 1.39 29.80 3.05 21.8 121 HDPE TCFG5.sup.4 Virgin HDPE 1.15 4.6 30.7 3.06 30.0 146 TCFG6.sup.5 Virgin HDPE 1.18 4.30 30.55 2.90 28.9 164 CWPC Recycled HDPE 1.15 2.50 27.8 2.20 20.0 138 .sup.1Rebound rate after 20% Compression. .sup.2Surface hardness test based on ASTM F3550-A, on a commercial artificial grass turf with 64 mm-long grass and 38 mm infill depth. .sup.3Additional data not otherwise presented in Table 1 for the TCFG3 sample: Improved composite resistance to both termite and decay fungi was seen. Weight loss from decay with brown rot G. trabeum for TCFG3 was 0.74%. Weight loss from decay with brown rot G. trabeum for control was 32.3%. Mean weight loss from Formosan subterranean termites was 29.7% for the untreated wood controls. Mean weight loss from Formosan subterranean termites was 0.55% for TCFG3 samples. .sup.4Additional data not otherwise presented in Table 1 for the TCFG5 sample: Improved composite color change index was seen, showing better UV resistance for TCFG5 samples, with fewer surface cracks. Incorporating a UV absorber (2.0% by weight) led to a reduced color change index (E): 22.5 (control without UV agent) versus 18.0 (composition with UV agent) after 2000 hour UV exposure. These results showed enhanced color stabilization. There were substantially fewer surface cracks in the samples with the UV agent. .sup.5Additional data not otherwise presented in Table 1 for the TCFG6 sample: Improved flame retardance was seen. TCFG6 samples had a reduced peak of heat release rate (pHRR: control sample = 371.48 kW/m.sup.2 vs. treated sample = 284.88 kW/m.sup.2), lower total heat release (THR: control sample = 166.85 kW/m.sup.2 vs. treated sample = 153.13 kW/m2), similar total smoke production (TSP: control sample = 11.03 m.sup.2/m.sup.2 vs. treated sample = 11.60 m.sup.2/m.sup.2), and lower mass loss (ML: control sample = 55.64% vs treated sample = 50.07%) as compared to controls.

(22) Three selected composite formulations were granulated to pass through a US 8-mesh circular screen. Diameters of the granulated materials were measured with a digital caliper. Mean particle diameter and standard deviation for each sample set were determined from measured particle diameters. Ranges of particle size distribution were determined for each group. The data are shown in Table 2. Most particles were approximately spherical, with an aspect ratio less than two.

(23) TABLE-US-00002 TABLE 2 Average particle size and particle size distributions for three formulations Average Standard Particle size distribution .sup.a Mean deviation 10% 30% 50% 70% 90% Formulation (mm) (mm) (mm) (mm) (mm) (mm) (mm) TCFG4 2.05 0.37 <1.63 <1.82 <1.95 <2.28 <2.60 TCFG5 2.37 0.66 <1.59 <1.95 <2.35 <2.66 <3.20 TCFG6 1.98 0.46 <1.40 <1.75 <1.95 <2.20 <2.43 .sup.a Particle sizes were measured and counted by laser. Percentages are by particle numbers. For example, with a hypothetical sample size of 1000 particles of TCFG4, 10% of the total number (or 100 particles) consisted of the smallest particles, those having a length (longest dimension) less than 1.63 mm, 30% (or 300 particles) had a length less than 1.82 mm, 50% (or 500 particles) had a length less than 1.95 mm in diameter; etc. . . . and 10% (or 100 particles) had a length greater than 2.60 mm.

Example 16. Slender Composite Particles

(24) A lab granulator was used to make slender particles from TCFG5, using a metal screen with rectangular openings. The dimensions of the resulting particles were measured with a digital caliper. The particles had lengths varying from about 5 to 20 mm, widths varying from about 1 to 5 mm, and thicknesses from about 0.1 to 1.5 mm. The aspect ratio (ratio of the length of the longest side to the length of the shortest side) varied from about 5 to 70.

(25) The complete disclosures of all references cited in this specification are hereby incorporated by reference, as are the complete disclosures of the present inventor's patent application publications US 2014/0374110, US 2012/0108472, and US 2011/0263758, and also the complete disclosure of priority application 62/175,474. In the event of an otherwise irreconcilable conflict, however, the present specification shall control.