Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/02—Elements
  • C08K3/04—Carbon
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K7/00—Use of ingredients characterised by shape
  • C08K7/02—Fibres or whiskers
  • C08K7/04—Fibres or whiskers inorganic
  • C08K7/06—Elements
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L71/00—Compositions of polyethers obtained by reactions forming an ether link in the main chain; Compositions of derivatives of such polymers
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L79/00—Compositions of macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen with or without oxygen or carbon only, not provided for in groups C08L61/00 - C08L77/00
  • C08L79/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
  • C08L79/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors

Definitions

• the present invention relates to a thermoplastic composition and an article made therefrom having low friction/sliding properties. More particularly, the present invention relates to a thermoplastic composition containing at least graphite, mica and carbon fiber for low coefficient of friction materials and an article made therefrom.
• U.S. Patent No. 5,969,083 to Long et al. discloses a select class of liquid crystalline polyesters and molding compositions comprising the polyesters and glass fiber.
• the liquid crystalline polyesters consist essentially of (1) diacid residues consisting essentially of (i) cyclohexanedicarboxylic acid residues and (ii) other diacid residues, 2,6- naphthalene-dicarboxylic acid residues, or a mixture thereof; (2) diol residues consisting essentially of hydroquinone residues, 4,4'-biphenol residues or a mixture thereof; and, optionally (3) p-hydroxybenzoic acid residues.
• the moles of diol residues are equal to the moles of diacid residues and the total of the (1), (2) and (3) mole percentages is equal to 100.
• the liquid crystalline polyesters have melting points determined by differential scanning calorimetry equal to or less than 360°C.
• U.S. Patent No. 5, 844,036 to Hughes discloses an injection moldable, highly filled polymer composites, which exhibit high dimensional stability at temperatures above the glass transition temperature of the matrix polymer.
• the heat distortion temperature of the composites approaches that of the crystal melting temperature of the matrix polymer.
• the composite includes a polyaryletherketone matrix and at least two types of fillers each providing unique properties.
• the first filler is a reinforcing fiber filler, which provides high strength and stiffness.
• the second filler is a non-thermoplastic immobilizing filler to immobilize the amorphous portion of the partially crystalline polyaryletherketone polymer and provide resistance to high temperature distortion. Notwithstanding its improved mechanical and heat resistant properties, the composite remains injection moldable and thus capable of low cost manufacturing.
• U.S. Patent No. 5,830,940 to Nakamura et al. discloses a shaped article of a liquid crystalline polymer containing (A) 100 parts by weight of a liquid crystalline polyester and/or liquid crystal polyesteramide capable of forming an anisotropic melt and (B) 0.01 to 2 parts of an olefinic polymer and having a retention rate of a weld strength of 15% to 100%, which has excellent heat stability, mechanical properties, dimensional stability and mold releasability and is suitable for various application uses such as electrical and electronic related devices, accurate machine related devices, office related devices, automobile related parts.
• U.S. Patent No. 5,789,523 to George et al. discloses polyimide compositions that can be substantially improved by incorporating into the composition an inorganic, low hardness, thermally stable, sheet silicate, such as muscovite mica, talc and kaolinite, which results in improved wear resistance and reduced coefficient of friction.
• U.S. Patent No. 5,700,863 to Bloom discloses polyimide polymeric blends which are environmentally friendly during compounding and give improved coefficient of friction in shaped articles prepared therefrom are provided by blending polyimides which are at least 90% imidized and substantially solvent free and have a mean particle size of about 30 ⁇ m or less with at least one melt processible thermoplastic liquid crystalline polymer or polyamide and a lubricant.
• U.S. Patent No. 4,115,283 to Needham discloses an antifriction composition useful for bearings comprising poly(arylene sulfide), a solid lubricating component, a reinforcing material, and a filler in which the commonly employed antimony trioxide filler is replaced in whole or in part by a replacement filler of calcium carbonate, titanium dioxide, barium sulfate, hydrated aluminum silicates, red iron oxide, carbon black or diatomaceous earth, compatible with the other components.
• Thermoplastics are used in a variety of applications including molding resins. Thermoplastics are used in a variety of applications because they have desirable (combination of) properties that other polymers have been unable to match. There are many applications in which low coefficient of friction (COF) is desired such as in bushings and bearings where the low coefficient of friction results in lower heat generation and improved lifetime for the application.
• COF low coefficient of friction
• thermoplastic material It is desirable to improve the coefficient of friction of thermoplastic material to less than or equal to 0.2.
• a composition comprising a thermoplastic material containing fillers wherein said fillers comprise: (A) 1-20% by weight of graphite; (B) 4-30% by weight of a carbon fiber; and (C) 1-20% by weight of mica, said composition having a coefficient of friction of less than or equal to 0.20 .
• an article made from a composition comprising a thermoplastic material containing fillers wherein said fillers comprise: (A) 1-20% by weight of graphite; (B) 4-30% by weight of a carbon fiber; and (C) 1-20% by weight of mica, said composition having a coefficient of friction of less than or equal to 0.20.
• PV pressure x velocity
• Pareto Chart is a bar graph that shows information in order of magnitude. The Pareto Chart is used to identify those factors that have the greatest cumulative effect on the system. 3. For purposes of this application the following legend is provided showing the capital letter(s) that coincides with the description of the materials used in the Examples or Pareto Chart herein:
• polyimides are suitable for use according to the invention, including those described in U.S. Patent No. 3,179,614, the teachings of which are incorporated herein by reference.
• the polyimides described therein are prepared from at least one diamine and at least one anhydride.
• Preferred diamines which can be used, include m-phenylene diamine (MPD), p-phenylene diamine (PPD), oxydianiline (ODA), methylene dianiline (MDA), and toluene diamine (TDA).
• Preferred anhydrides which can be used to include benzophenone tetracarboxylic dianhydride (BTDA), biphenyl dianhydride (BPDA), trimellitic anhydride (TMA), pyromellitic dianhydride (PMDA), maleic anhydride (MA), and nadic anhydride (NA).
• BTDA benzophenone tetracarboxylic dianhydride
• BPDA biphenyl dianhydride
• TMA trimellitic anhydride
• PMDA pyromellitic dianhydride
• MA maleic anhydride
• NA nadic anhydride
• Preferred polyimides include those prepared from the following combinations of anhydride and diamine: BTDA-MPD, MA-MDA, BTDA- TDA-MPD, BTDA-MDA-NA, TMA-MPD & TMA-ODA, BPDA-ODA, BPDA- MPD, BPDA-PPD, BTDA-4,4'-diaminobenzophenone, and BTDA-bis(p- Phenoxy)-p,p'biphenyl.
• An especially satisfactory polyimide useful in the present invention is that prepared from pyromellitic dianhydride and 4,4'- oxydianiline (PMDA-ODA).
• High performance shaped articles are formed from thermoplastics of this invention by a suitable thermoplastic molding operation including but not limited to injection or compression molding. Forming conditions must be selected to prevent polymer degradation and the formation of a well-consolidated structure.
• the thermoplastics for use in the present invention include polypropylene, polyethylene, chlorinated polyethylene, polyethylene terephthalate (PET), polyamides, polysulfones, polyetherimides, polyether sulfones, polyphenylene sulfone, polyphenylene sulfide, polyether ketones, polyether ether ketones (PEEK), polyacetal, polycarbonate, ethylene- tetrafluoroethylene copolymers, aromatic polyesters, grafted polyphenylene ether resin, liquid crystal polymers and mixtures thereof.
• Articles made from the composition of the present invention are another embodiment of the present invention.
• Typical articles include, but are not limited to, bearings, gears, bushings and brush washers.
• the present invention is further illustrated by the following Examples in which parts and percentages are by weight unless otherwise indicated.
• wear specimens were prepared by machining test blocks of the composition described. A 6.35mm (0.25") wide contact surface of a wear/friction test block was machined to such a curvature that it conformed to the outer circumference of a 35mm (1.38”) diameter x 9.74mm (0.34") wide metal mating ring. The blocks were oven dried and maintained over desiccant until tested.
• Wear Factor weight loss (grams)/(material density (g/cc) x test duration (hr) x load (kg) x velocity (mis)).
• the wear factor is determined by the above calculation. Wear Factor allows pressure and velocity to be taken into account when comparing resins. A low number is desired for Wear Factor and a low number or narrow range is desired for the Coefficient of Friction. Coefficient of Friction is preferably ⁇ 0.20. When a sample is considered to have failed the wear test, melting of the sample occurs such that no usable weight loss can be calculated and the COF is suspect because the wear specimen is no longer of a known dimension.
• the Tm i.e. melting temperature
• onset of melting temperature were determined using a 25°C/minute heating rate with either a DuPont Model 1090 Dual Sample Differential Scanning Calorimeter or a TA Instruments Model 2010 Differential Scanning Calorimeter by ASTM D3418.
• the melting point is taken as the peak of the melting endotherm on the second heat when measured by Differential Scanning Calorimetry.
• Cypek® DS-E manufactured by Cytec Industries, Inc. was tested in order to provide a comparison of a non-LCP matrix material to an LCP matrix material, in the present invention.
• Cypek® DS-E is a polyether ketone ketone (PEKK) and has an onset of melting temperature of 280°C and a Tm of 307°C.
• PEKK polyether ketone ketone
• the pellets were molded into standard 6.4mm thick ASTM (D638) tensile test bars using a 170g capacity, 145-ton clamping pressure injection molding machine.
• the profile was as follows: Rear 335°C, Center 340°C, Front 340 °C and Nozzle 345 °C. Boost 1.5 sec, Injection 5 sec, Hold 15 sec, Injection Pressure 5.5 MPa, Ram Speed fast, Screw Speed 115 rpm and Back Pressure 0.3MPa.
• Example 1 A statistically designed experiment was utilized to determine the relationship between the fillers used in Example 1 and the coefficient of friction (COF).
• the same method for sample preparations as used in Example 1 was used in Example 2 with the exception of various filler amounts being changed .
• a 32 run, four (4) variable screening design with four (4) midpoints and two levels of replication was used.
• Each filler component was set from 0 to 12 weight percent where total filler content did not exceed 48 weight %.
• the various compositions were measured for friction at a PV of 1.75 MPa-m/s. Values were obtained for the coefficient of friction even if the sample did not survive the entire 24 hours of the test.
• Table 2 documents the formulation and the coefficient of friction (COF) of the two wear tests performed on each sample.
• the Pareto Chart in Chart 1 plots the fillers (horizontal axis) and the effect on the coefficient of friction (vertical axis) from the statistically determined data shown in Table 2.
• the horizontal line, in the chart, indicates the calculated confidence control limit (CCL) of 0.04.
• CCL confidence control limit
• the effects above the CCL of 0.04 are considered special cause variation and are considered to be significant.
• the presence of the carbon fiber (CF) as a filler is critical to obtaining low coefficient of friction (e.g. less than or equal to 0.02).
• Mica (M) and graphite (G) are also considered to be significant as their values from the Pareto Chart are greater than the CCL.
• the combination of PP (particulate polyimide) and the G (graphite) are also determined to be of significance as filler for determining coefficient of friction.
• This equation is used in the present invention to determine statistically the filler levels to achieve desired coefficient of friction.
• Example 38 The same method for sample preparation as used in Example 1 was utilized in Example 3. Seventy-five (75) weight percent of a liquid crystalline polyester (DuPont Zenite® 7000) was blended with 10 weight percent of 4767 synthetic graphite, 10 weight percent of Amoco® VMX26 milled carbon fiber, and 5 weight percent of mica (Alsibronz® 10) (Sample 38). Wear testing was done at 1.75 MPa-m/s for this Sample No. 38 and resulted in a wear factor of 30.4 x 10 "6 cc-s/m-kg-hr and a coefficient of friction of 0.115. The value predicted by the equation in Example 2 is 0.098. (Note: The above described model in Example 2 and Table 2 are based on the resin of Example 3. The model would need to be modified for changes to the resin and/or the range of the fillers.)
• Example 39 The same method for sample preparation as used in Example 1 was utilized. Sixty-five (65) weight percent of a poletherketone ketone (Cypek® DS-E) was blended with 10 weight percent of 4767 synthetic graphite, 10 weight percent of Amoco® VMX26 milled carbon fiber, 10 weight percent of a particulate polyimide resin (Vespel® SP-1) and 5 weight percent of mica (Alsibronz® 10) (Sample 39). Processing conditions were comparable to that used in Example 1 and was such that the molded part kept its amorphous character. Wear testing was done at 1.4 MPa-m/s for this Sample No. 39 and resulted in a wear factor of 19.2 x 10 "6 cc-s/m-kg-hr and a coefficient of friction of 0.124.
• a poletherketone ketone Cypek® DS-E
• the pellets were molded into standard 6.4mm thick ASTM (D638) tensile test bars using a 170g capacity, 145-ton clamping pressure injection molding machine.
• the profile was as follows: Rear 370°C, Center 400 °C, Front 405°C and Nozzle 405°C.
• the mold was set to 130 °C.
• the injection conditions were Boost 1 sec, Injection 15 sec, Hold 15 sec, Injection Pressure 3.4 MPa, Ram Speed fast, Screw Speed 120 rpm and Back Pressure minimum.
• Example 2 The same method for sample preparation as used in Example 1 was utilized in this example. Sixty-five (65) weight percent of a liquid crystalline polyester (DuPont Zenite® 7000) was blended with10 weight percent of 4767 synthetic graphite, 10 weight percent of fiber indicated in the "Fiber Manufacturer” and “Fiber Type” columns of Table 4, 5 weight percent of mica (Alsibronz® 10) and 10 weight percent of a particulate polyimide resin (Vespel® SP-1).
• a liquid crystalline polyester DuPont Zenite® 7000
• Example 2 The same method for sample preparation as used in Example 1 was utilized.
• a liquid crystalline polyester (Zenite® 7000) was blended with various weight percents of a particulate polyimide resin (Vespel® SP-1), graphite (4767 synthetic), Mica (Alsibronz ⁇ 10) and Carbon Fiber (Panex 33MF manufactured by Zoltek) as documented in Table 5. Processing conditions were comparable to that used in Example 1. Wear testing was done at 1.75 MPa-m/s and is reported in Table 5.
• Example 53 The same method for sample preparation as used in Example 1 was utilized in Example 8. Sixty-five (65) weight percent of a liquid crystalline polyester (Zenite® 7000) was blended with 10 weight percent of a particulate polyimide resin (Vespel® SP-1), 10 weight percent of M990 natural graphite manufactured by Asbury Graphite Mills, Inc., 10 weight percent of Panex 33MF milled carbon fiber (manufactured by Zoltek), and 5 weight percent of mica (Alsibronz® 10) (Sample 53). Wear testing was done at 1.75 MPa-m/s and Sample No. 53 resulted in a wear factor of 45.9 x 10 "6 cc-s/m-kg-hr and a coefficient of friction of 0.18.
• Zenite® 7000 liquid crystalline polyester
• Vespel® SP-1 particulate polyimide resin
• M990 natural graphite manufactured by Asbury Graphite Mills, Inc. 10 weight percent of Panex 33MF milled

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• Organic Chemistry (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Sliding-Contact Bearings (AREA)
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• Liquid Carbonaceous Fuels (AREA)

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• 2003
  • 2003-09-10 US US10/659,203 patent/US20040158005A1/en not_active Abandoned
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  • 2003-12-16 EP EP03814120A patent/EP1572792B1/en not_active Expired - Lifetime
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