Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C71/00—After-treatment of articles without altering their shape; Apparatus therefor
  • B29C71/04—After-treatment of articles without altering their shape; Apparatus therefor by wave energy or particle radiation, e.g. for curing or vulcanising preformed articles
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G67/00—Macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing oxygen or oxygen and carbon, not provided for in groups C08G2/00 - C08G65/00
  • C08G67/02—Copolymers of carbon monoxide and aliphatic unsaturated compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
  • B29C2035/0844—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using X-ray
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0805—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation
  • B29C2035/085—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using electromagnetic radiation using gamma-ray
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0866—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using particle radiation
  • B29C2035/0872—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using particle radiation using ion-radiation, e.g. alpha-rays
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C35/00—Heating, cooling or curing, e.g. crosslinking or vulcanising; Apparatus therefor
  • B29C35/02—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould
  • B29C35/08—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation
  • B29C35/0866—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using particle radiation
  • B29C2035/0877—Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mould by wave energy or particle radiation using particle radiation using electron radiation, e.g. beta-rays
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2096/00—Use of specified macromolecular materials not provided for in a single one of main groups B29K2001/00 - B29K2095/00, as moulding material

Definitions

• This invention relates to polyketone polymers. More particularly, this invention relates to crosslinked polyketone polymers, their production and their application.
• Linear alternating polymers of carbon monoxide and olefins herein referred to as polyketones or polyketone polymers are well known in the art .
• This class of polymers is disclosed in numerous patent documents, such as in US-A-4880865 and US-A-4818811.
• Polyketone polymers display a well balanced set of mechanical properties which make them particularly useful as engineering thermoplastics. The excellent properties of polyketones could be further exploited by improving the materials so that they exhibit improved tribological properties.
• Parts and items made from such improved materials would be able to resist wear and to bear greater frictional loads when m rolling or sliding contact, m particular over extended durations. Such properties are generally attained through the addition of additives. However, it would be beneficial if they could be attained without the addition of additives to avoid other changes in the polyketone properties due to additive loading of the polymer matrix. It would also be beneficial if other attributes such as thermal performance, dimensional stability and tensile strength could be improved without further loading the polymer with additives.
• polyketones which are crosslinked m the melt are not particularly desirable e.g. in applications as an engineering thermoplastic. Aside from chemical mod - fication, substantially crosslinked polyketones which do not exhibit such a loss in mechanical properties have not yet been produced.
• US-A-3812025 proposes crosslinking by high-energy radiation of polyolefins having a small mole fraction of ketone groups m the backbone or in side chains, viz. generally less than about 10 mole%, in particular less than about 5 mole%, calculated on monomer.
• ketone groups are incorporated by copolymerizing the olefin with carbon monoxide or with a vinyl ketone, optionally by graft or block copolymerization. Only polymers with a low content of ketone groups have been employed because, according to US-A-3812025, these polymers have all the desired properties of unmodified polyolefins.
• polyketone polymer would undergo degradation by chain scission.
• properties of polyketone polymers can be enhanced through curing by high energy radiation and that the materials produced by this process are unique m their properties, such as in enhanced thermal and mechanical properties, for example toughness, and m triPological characteristics, for example wear.
• the products are excellently suitable for use m a range of highly demanding applications, for example applications where articles of the radiated polyketones are placed m rolling or sliding contact with each other or with otner articles .
• the invention relates to a process for crosslinking a polyketone polymer comprising crosslinking the polyketone polymer by exposure to high energy radiation.
• the invention further relates to the crosslinked polyketone polymer per se as obtainable by the process of the invention.
• the invention also relates to articles of manufacture which comprise the crosslinked polyketone of this invention and/or which can be obtained by a process which includes the process for crosslinking a polyketone in accordance with this invention.
• the processes of this invention comprise irradiating polyketone polymer at one or more points during the processing of the polymer or of articles made therefrom.
• the invention also includes compositions comprising a crosslinked polyketone according to the invention.
• polyketones or polyketone polymers are linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon. These terms refer to copolymers, ter ⁇ polymers, quaterpolymers etc. of these monomers
• Polymer additives well known m the art can be used in con ⁇ junction with the polyketones For instance, fillers, extenders, lubricants, pigments, plasticizers, and other polymeric materials can be added to the polyketone compositions to improve or otherwise alter the properties of the compositions.
• DCOF During relative motion of two surfaces m contact the DCOF is the ratio of the resulting frictional force to the applied normal force while holding the relative surface velocity constant over time
• the LPV is the multiplicative product of the normal pressure and surface velocity at the step just prior to catastrophic material failure due to thermal softening.
• Crosslinking is the attachment of two or more polymer molecules at least one point on the backbone of each polymer molecule so joined Crosslinking results m an increase m molecular weight Extensive crosslinking results m the formation of a gel which comprises a network of polymer chains rendering the gel insoluble in solvents used for dissolving the uncrosslinked polymer.
• a crosslinked polyketone is typically a polyketone polymer which exhibits an increase m the weight average molecular weight of at least 10% relative to the poly ⁇ ketone staring material. Indeed, polyketone polymer which is already crosslinked to one degree or another can be further crosslinked according to the metnod of this invention.
• “Curing” is the treatment of the polyketone polymer m accordance with this invention.
• the polyketone polymer is crosslinked without an overall loss m useful mechanical properties.
• cured poly ⁇ etone polymers are distinguished from other crosslinked polyketone polymers (e.g. those crosslinked m the melt) m their exhibition of substantially no increase (relative to the uncured material from which it was made) m the intensity of emission at 490 nm when excited with 400 nm light. Typically there is less than 10% increase m the intensity m emission at 490 nm.
• “Specific surface area” means the surface area per unit mass (m 2 /g) .
• the polyketones for use in this invention are linear alternating copolymers of carbon monoxide and at least one ethylenically unsaturated compound.
• the polyketone polymers are of a linear alternating structure which means that they contain one molecule of carbon monoxide for each molecule of the ethylenically unsaturated compound.
• Ethylenically unsaturated compounds comprise suitably up to 20 carbon atoms and include compounds which consist exclusively of carbon and hydrogen and compounds which m addition comprise hetero atoms, such as unsaturated esters, ethers and amides. Unsaturated hydrocarbons are preferred.
• ethylenically monomers examples include aliphatic ⁇ -olefins, such as ethene, propene and butene-1, cyclic olefins such as cyclopentene, aromatic compounds, such as styrene and ⁇ -methylstyrene and vinyl esters, such as vinyl acetate and vinyl propionate .
• the preferred polyketone polymers are linear alternating copolymers of carbon monoxide and ethene or linear alternating copolymers of carbon monoxide, ethene and another ethylenically unsaturated compound of at least 3 carbon atoms, particularly an u- olefin such as propene or butene-1.
• the preferred polyketone polymers of carbon monoxide, ethene and another ethylenically unsaturated compound there will be within the polymer typically at least 2 units incorporating a moiety of ethene for each unit incorporating a moiety of the other ethylenically unsaturated compound(s) . Preferably, there will be from 10 units to 100 units incorporating a moiety of ethene for each unit incorporating a moiety of the other ethylenically unsaturated compound(s) .
• the polymer chain of preferred polyketone polymers is therefore represented by the repeating formula
• G is the moiety of the ethylenically unsaturated compound of at least 3 carbon atoms polymerized through the ethylenic unsaturation and the ratio of y:x is typically no more than 0.5.
• linear alternating polymers of carbon monoxide and ethene are employed m the compositions of the invention, there will be no second ethylenically unsaturated compound present and the polymers are represented by the above formula wherein y is zero.
• y is other than zero the -CO-CH2—H2-)- units and the —CO-G units are found randomly throughout the polymer chain, and preferred ratios of y:x are from 0.01 to 0.1.
• the precise nature of the end groups does not appear to influence the properties of the polymer to any considerable extent so that the polymers are fairly represented by the formula for the polymer chains as depicted above.
• the polyketone polymers of number average molecular weight from 1000 to 200,000, particularly those of number average molecular weight from 20,000 to 90,000 a ⁇ determined by gel permeation chromatography are of particular interest .
• a preferred range of the weight average molecular weight is from 2000 to 1,000,000, m particular from 40,000 to 500,000.
• the physical properties of the polymer will depend m part upon the molecular weight, whether the polymer is based on a single or on a plurality of ethylenically unsaturated compounds and on the nature and the proportion of the ethylenically unsaturated compounds.
• Typical melting points for the polymers are from 175 °C to 300 °C, more typically from 210 °C to 270 °C, as determined by differential scanning calorimetry.
• the polymers have typically a limiting viscosity number (LVN) , measured in m-cresol at 60 °C in a standard capillary viscosity measuring device, from 0.5 dl/g to 10 dl/g, more typically from 0.8 dl/g to 4 dl/g.
• LPN limiting viscosity number
• US-A-4808699 teaches the production of polyketone polymers by contacting ethene and carbon monoxide in the presence of a catalyst comprising a
• Group VII metal compound an anion of a nonhydrohalogenic acid with a pKa less than 6 and a bidentate phosphorus, arsenic or antimony ligand.
• US-A-4868282 teaches the production of polyketone polymers by contacting carbon monoxide and ethene m the presence of one or more hydrocarbons having an ethylenically unsaturated group with a similar catalyst.
• the degree or depth of cure is dependent, in part, on the source and intensity of the radiation source.
• a photon-type source of radiation such as ⁇ -radiation
• the cure can be affected throughout the polymer matrix. This is largely due to the penetrating nature of the radiation. Surface curing will occur with non-penetrating radiation such as an ion beam.
• the type of ion used and the intensity of the bombardment will dictate the depth and degree of cure. Lighter ions will, of course, create a greater depth of cure than will heavier ions .
• electron beam (e-beam) crosslinking is particularly attractive as an industrial application.
• Polymer wires and cables, pellets, heatshrink products, roto-moulded parts, blow-moulded containers, injected moulded parts, and sheets are all easily subjected to high energy bombardment in such off-line processes with a minimum impact on other parts of the manufacturing process.
• the process can be nearly instantaneous with exposure times measured m seconds.
• the degree of crosslinking is directly related to the level of e-beam exposure and can be readily controlled.
• High energy radiation useful to bring about the cure of this invention is any irradiation which occurs with energy greater than 10 eV, especially greater than 100 eV, and can be successfully undertaken with irradiation which occurs with energy up to IO 9 eV. Particularly useful is an energy level of 10 4 -10 8 eV
• Well known sources of such radiation include e-beam, X-ray, gamma ray, and ion beams
• Preferred sources are e-beam, gamma radiation, and, when surface curing is desired, ion beam
• the most preferred source is a gamma radiation source such as industrial Co ⁇ ° emitters
• gamma radiation such as from a Co 60 emitter
• preferred doses range between 5 Mrad and 25 Mrad although doses between 1 and 50 Mrad are believed to have a beneficial effect It is most preferred that the dose be 5-5 6 Mrad. Any rate necessary to apply the doses needed for cure may be applied but cure is believed to be most efficiently affected with the highest rate of irradiation possible for the given emitter.
• the dose and rate of irradiation can be significantly lowered with the additional use of radiation accelerators known in the art such as triallyl cyanurates, ethylene glycol dimetha- crylate, polyethylene glycol dimethacrylate, and allyl methacrylate.
• Polyketone may be cured with or without the presence of other additives such as antioxidants and melt stabilizers. No special preparation of the poly ⁇ ketones is necessary. It has surprisingly been found that tribological properties such as LPV and Wear Factors have been improved through the practice of this invention.
• the cured polyketone polymer displays an LPV which exceeds the measurement capacity of commercially available analyzers. That is, the LPV is greater than 7000 kPa.m/s (200,000 psi. ft/mm) . Cured polyketone gears, bearings, and other parts which are m rolling or sliding contact can thus bear greater loads than parts which are not so cured.
• High temperature properties of the materials made according to this invention are also improved over those of the prior art
• the heat deflection temperature (HDT) of a polyketone sample cured by exposure to 20 Mrad of gamma radiation was increased to 100 °C
• a similar uncured polyketone polymer sample displayed an HDT of 92 °C
• cured polyketones made according to this invention should exhibit a lower transmission of reagents through the polymer matrix and should resist swelling or sorption of water, alcohol, chlorinated hydrocarbons and the like relative to uncured polyketones
• the cured polyketones of this invention can be used to produce snap fit parts, parts for use m load bearing applications, and heat shrinkable moulded parts It should also be useful m the preparation of parts useful in down-hole mining applications such as chemical, wear, and heat resistant piping Sleeves, wire and cable jacketing, coatings, connectors, liners, tubes and the like can also be made to good effect from this material.
• melt crosslinked polyketones can be readily distinguished from the melt crosslinked materials by characterization according to Doth visible fluorescence observations and fluorescence spectroscopy (excitation/emission spectra) Melt crosslinked polyketones display visible fluorescence under illumination by a mercury vapour lamp while polyketones crosslinked by exposure to high energy radiation do not Further, excitation and emission spectra for melt crosslinked polyketone is vastly different from polyketone polymer crosslinked by high energy radiation as is set forth m the examples Such characteristic differences can only result from differences in chemical structure Melt crosslinked polyketone polymers have a chemical structure compnsmg a fluorophore species while irradiation cured polyketone polymers do not, similar to the polyketone polymer starting material from which it was produced
• Polyketones having specific surface areas of less than 2.1 X IO"" 3 m 2 /g will undergo predominantly crosslinking while those having specific surface areas of at least 0.10 m 2 /g will undergo significant chain scission m the presence of air. It is believed that polyketones having specific surface areas of as little as 1 X IO -3 m 2 /g will crosslink m the presence of air.
• cryoground polymer is ordinarily less suitable for irradiation crosslinking m the presence of air due to the high proportion of polymer volume which would be exposed to oxygen.
• strands, most finished articles of manufacture such as gears and bearings, stock shapes for further machining, sheet, and the like are ordinarily well suited for irradiation curing.
• the temperature at which this process is carried out does not appear to be important. However, it is preferred that it be conducted at temperatures below the melting point of the polyketone polymer, such as at a temperature chosen m the range of 0-170 °C, m particular 10-150 ° C . Curing through the crosslinking of finished parts is one such preferred process Nevertheless, curing can still be conducted above the melting point to produce various useful embodiments of the cured material .
• Type I tensile bars were tested at a strain rate of
• Tribological Properties were measured using a Computer Controlled Multi-Specimen Test Machine In this testing, a thrustwasher injection moulded from the material to be tested was spun against a steel stationary washer m one direction Data logging for the following parameters was conducted continuously: speed, load, temperature, wear, and run time. LPVs, DCOF, and Wear Factors were computed from this data logging. LPV was measured at 0.51 m/s (100 fpm) velocity with stepped 4 4 N (10 lb) load increments from 9 1 N (20 lb) to specimen failure.
• Specimen failure is the sudden loss of structural integrity at melt softening Wear tests were run at 2.41 MPa (350 psi) load and 0 28 m/s (56 fpm) velocity for 4 hours to seat test specimens which were not irradiated Specimens which were then irradiated (after seating) were run at 0.28 MPa (40 psi) and 0.25 m/s (50 fpm) for 20 hours on a new stationary washer (a 1018 carbon steel with a 16-18 rms finish) The test specimen and stationary washer were measured for thickness and weight before and after each run. The specific gravity of the test specimen was then incorporated into the computation of the resulting wear factor.
• Heat Deflection Temperatures were determined using ASTM D648 with a 1.82 MPa (264 psi) load. Melting point (Tm) and enthalpy of fusion ( ⁇ H) were determined under nitrogen using a differential scanning calorimeter (model 7700) with a ramp rate of 20 °C per minute Unless otherwise stated, irradiation of the materials used m the examples was accomplished by subjecting the polyketone polymei with a Co 6 0 ⁇ -radiation source at a rate of 0.28 Mrad/hour.
• Example 1 Neat linear alternating polyketone (terpolymer of carbon monoxide, ethylene, and a minor amount of propylene) having a melting point of about 220 °C and a limiting viscosity number of 1 8 dl/g was prepared This material was blended with 0.2% IRGANOX 1330 (IRGANOX is a trademark) hindered phenol antioxidant, 0.3% NUCREL 535 (NUCREL is a trademark) ethylene methacrylic acid copolymer and 0.2% calcium hydroxyapatite (all percentages are as a weight percent of total weight of the mixture) Tensile bar specimens were prepared from this material. Specimen A was not subsequently irradiated Specimens B and C were ⁇ -irradiated m air with 5.6 Mrad and 20 Mrad, respectively. Various mechanical properties and characteristics were measured as set forth m Table 1 below Table 1
• Neat linear polyketone (terpolymer of carbon monoxide, ethylene, and a minor amount of propylene) having a melting point of about 220 °C and a limiting viscosity number of about 1.8 dl/g was prepared (Mw of 83,000 with a MWD of 4.3) .
• This material was blended with 0.5% IRGANOX 1330 hindered phenol antioxidant m a twin screw extruder and forced through a die to yield a 1.52 mm (60 mil) (diameter) strand
• Example 3 The polyketone polymer of Example 2 was cryoground into a powder. About 10 grams of the polymer powder was placed m a glass tube which was evacuated to reach a pressure of 0.4 Pa (3 mtor) . The samples thus presented a specific surface area of 0.10 m 2 /g (as measured by the BET method) . The sample was then exposed to 5.6 Mrad of ⁇ -radiation.
• Example 4 The polyketone polymer as set forth in Example 1 was processed through a tubular blown film line using a 31.8 mm (1.25 inch) extruder and prepared as a film having a thickness of 0.051 mm (2 mil) .
• Four 10.2x10.2 cm (4X4 inch) specimens were prepared from the blown film. The first specimen was not irradiated. It was analyzed to determined to have a Mw of 79,400. Three samples were then placed in an Energy Science Incorporated CB 150 Electrocurtain apparatus.
• the sample chamber was purged with nitrogen such that oxygen content was less than 100 ppm. Specimens were then exposed to electron beam irradiation having a voltage of 165 kV. The cathode power was 360 W.
• the specimen exposed to a total of 5 Mrad was found to have a Mw of 87,500, the specimen exposed to 10 Mrad was found to have a Mw of 141,000, and the specimen exposed to 20 Mrad was found to have a Mw of 144,000 (with 20% gels) .
• Example 5 Three different 3.18 mm (1/8 inch) type I tensile bars were prepared from the polyketone polymer of Example 1.
• tensile bar A was not irradiated or treated to a further melt heat history.
• Tensile bar B was subjected to 5.6 Mrad of ⁇ -radiation.
• tensile bar C was placed in a 3.18 mm (1/8 inch) mould and heated for 20 minutes at 265 °C in a compression moulder with a clamp pressure of 70 MPa (10,000 psi) to induce crosslinking in the melt.
• Tensile bar C was then removed from the compression moulder and cooled to room temperature.
• the tensile bars were then submitted to visible fluorescence observations by exposing them to the light emitted from an unfiltered hand-held mercury vapour lamp No visible fluorescence was observed m the case of Tensile bars A and B.
• a bright yellow fluorescence was observed in Tensile bar C, the melt crosslinked sample.
• Specimen A- LPV 1120 kPa.m/s (32,000 psi. ft/mm)
• Specimen B LPV>7000 kPa.m/s (> 200,000 psi. ft/mm) (exceeds capacity of instrumentation)
• Specimen C LPV>7000 kPa.m/s (>200,000 psi. ft/mm) (exceeds capacity of instrumentation) .

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• 1996
  • 1996-12-10 EP EP96944024A patent/EP0868293A1/de not_active Withdrawn
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  • 1996-12-10 JP JP9521753A patent/JP2000501761A/ja active Pending
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