Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J3/00—Processes of treating or compounding macromolecular substances
  • C08J3/02—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques
  • C08J3/03—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media
  • C08J3/05—Making solutions, dispersions, lattices or gels by other methods than by solution, emulsion or suspension polymerisation techniques in aqueous media from solid polymers
• • 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
  • C08K3/18—Oxygen-containing compounds, e.g. metal carbonyls
  • C08K3/20—Oxides; Hydroxides
• • 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
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/05—Alcohols; Metal alcoholates
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L23/00—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers
  • C08L23/02—Compositions of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Compositions of derivatives of such polymers not modified by chemical after-treatment
  • C08L23/04—Homopolymers or copolymers of ethene
  • C08L23/06—Polyethylene
• • D—TEXTILES; PAPER
  • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
  • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
  • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
  • D01F6/02—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • D01F6/04—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyolefins
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2323/00—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers
  • C08J2323/02—Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers not modified by chemical after treatment
  • C08J2323/04—Homopolymers or copolymers of ethene
  • C08J2323/06—Polyethene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2207/00—Properties characterising the ingredient of the composition
  • C08L2207/06—Properties of polyethylene
  • C08L2207/068—Ultra high molecular weight polyethylene
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2314/00—Polymer mixtures characterised by way of preparation
  • C08L2314/02—Ziegler natta catalyst
• • 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
  • C08L71/02—Polyalkylene oxides

Definitions

• the invention relates to a process for producing articles from ethylene polymer with an intrinsic viscosity (IV) of at least 4 dl/g and with a low density of entanglement, starting from a composition comprising the ethylene polymer and an auxiliary, which composition is pressed through an opening below the melting point of the ethylene polymer.
• IV intrinsic viscosity
• auxiliaries are used having a dissolving or swelling effect for the ethylene polymer at a temperature at which the mixture of ethylene polymer and auxiliary is processed.
• the disadvantage of these auxiliaries is that they are so expensive and/or so harmful to the environment that it is necessary for these substances to be recovered in a certain process step. This recovery involves a high amount of costs.
• the object of the invention is to provide a process described in the opening lines that does not have said disadvantages, or to a less degree.
• auxiliary is a non-solvent for the ethylene polymer capable of being formed into a paste with the ethylene polymer.
• non-solvents too, once they are mixed with the ethylene polymer, are capable of realizing a cohesion between the polymer particles during the pressing operation carried out below the melting point of the pure ethylene polymer.
• This cohesion has been found to be so strong that articles are formed that are suited as such to serve as intermediate products for the production of articles with a high tensile strength and a high modulus.
• Suitable non-solvents according to the invention are those auxiliaries in which the ethylene polymer does not appreciably swell or dissolve at the processing temperature.
• the non-solvent according to the invention must have a melting point below the melting point of the ethylene polymer.
• the auxiliary is a non-solvent according to the invention.
• suitable non-solvents are water and alcohols, for instance methanol, n-propanol, isopropanol, ethanol and n-butanol. Highly suitable as non-solvent is water. This has the advantage that it is cheap and environmentally benign. Butanol has the advantage that it is cheap and that it is easier to remove from the moulded article than water.
• a surface tension reductant is added to tfc-. non-solvent.
• the surface tension reductants known in the art can be used, such as anionic, kationic and non-ionic detergents.
• a suitable surface tension reductant is, for instance, the detergent TritonR N 101 of Rohm & Haas.
• the said surface tension reductant is added to the non-solvent in, for instance, a concentration of 1% (wt).
• the amount of surface tension reductant must be such that the ethylene polymer particles are so wetted by the non-solvent that a homogeneous paste can be formed.
• the surface tension reductant can be removed from the ethylene polymer, for instance by washing. After removal, the concentration of surface tension reductant in the ethylene polymer is preferably less than 0.05% (wt), more particularly less than 0.01% (wt). calculated on the ethylene polymer.
• the concentration of the non-solvent in the composition is preferably not above 50% (vol.) calculated on the composition. Higher concentrations, though possible, usually result in a paste that can be less readily pressed. Specifically, the concentration amounts to 10-40%.
• Ethylene polymer with a low density of entanglement is known from, for instance, US-A-4769433. In it the drawing is described of never previously dissolved or melted ultra-high molecular weight polyethylene ( 'virgin PE' ) prepared by polymerization at relatively low temperatures. Such ethylene polymers with a low density of entanglement can be drawn well below the melting point of the ethylene polymer. In this specification, therefore, an ethylene polymer with a low density of entanglement is defined as an ethylene polymer with a maximum draw ratio of at least 20. The maximum draw ratio is determined as follows.
• a layer of ethylene polymer powder having a thickness of 2 mm is compressed in a round mould with a diameter of 5 cm for 5 minutes at room temperature under a weight of 50,000 kg.
• the resulting round film is subsequently compressed in a flat mould for 10 minutes at 130°C under a weight of 100,000 kg.
• a dumb-bell test specimen is punched having a length of 10 mm between the shoulders and a width of 2 mm.
• this test specimen is drawn in a Zwick 1445 tensile tester at a speed of 10 mra/min until the specimen breaks.
• the maximum draw ratio is determined as the quotient of the length of the part of the specimen between the shoulders at the moment when the test specimen breaks and the length thereof before the drawing (10 mm) .
• the maximum draw ratio of the ethylene polymer is at least 20, preferably at least 40 and specifically at least 80.
• the 'virgin' ethylene polymer as prepared according to US-A-4769433 can further be characterized by the difference between the initial melting enthalpy of a sample and the melting enthalpy that is obtained when the sample has melted completely and has subsequently solidified again.
• the difference (fall) in melting enthalpies is preferably at least 10% of the initial melting enthalpy, specifically at least 20%.
• the crystallinity of the ethylene polymer just mentioned is high, at least 75%.
• Melting temperatures Tm and melting enthalpies ⁇ H can be determined with differential scanning calorimetry (DSC) at a scanning speed of 5°C/min and a commencing temperature of 40°C.
• the melting enthalpy ⁇ H is determined from the area below the melting curve. Crystallinities (%) are calculated by dividing the melting enthalpy ⁇ H of the sample by the melting enthalpy of 100% crystalline polymer. The ⁇ H for 100% crystalline polymer is assumed for polyethylene to amount to 293 kJ/kg.
• the ethylene polymer according to the invention consists of a homo or copolymer of ethylene with a DSC crystallinity of at least 30%. Preferably the DSC crystallinity is at least 50%.
• the intrinsic viscosity (IV) of an ethylene polymer according to the invention measured in decalin at 135°C is at least 4 dl/g, specifically at least 6 dl/g, more specifically it amounts to 8-40 dl/g.
• UHMWPE linear ultra-high molecular weight polyethylene
• UHMWPE linear polyethylene having fewer than 10 side chains per 1000 carbon atoms and preferably having fewer than 3 side chains per 1000 carbon atoms, or such a polyethylene as contains also minor amounts, preferably less than 5 moles %, of one or more other alkenes copolymerized with it, such as propylene, butylene, pentene, hexene, 4-methyl-pentene, octene, etc., which polyethylene or copolymer of ethylene has an intrinsic viscosity of at least 5 dl/g.
• the polyethylene may further contain minor amounts, preferably 25% (wt) at most, of one or more other polymers, specifically an alkene-1-polymer, such as polypropylene, polybutadiene or a copolymer of propylene with a minor amount of ethylene.
• an alkene-1-polymer such as polypropylene, polybutadiene or a copolymer of propylene with a minor amount of ethylene.
• Such an UHMWPE can be made, for instance, by applying a Ziegler or a Phillips process using suitable catalysts and under polymerization conditions known in the art.
• the ethylene polymer may also contain non-polymeric materials, such as waxes and fillers.
• the amount of these materials may be up to 60% (vol.) calculated on the ethylene polymer.
• the pressing of the paste through an opening may be done by the methods known in the art, for instance by calandering or by means of an extruder, such as a ram extruder or a screw extruder.
• an extruder such as a ram extruder or a screw extruder.
• Such orientation is promoted particularly by using an extrusion channel whose cross section decreases into the direction into which the material is pressed.
• the fact is that the cohesion of the moulded article or of the extrudate increases as the orientation of the ethylene polymer chains increases.
• the ratio between the areas of the cross sections at the beginning (A0) and at the end (Al) of the pressure channel is referred to as the reduction ratio (RR), which, with channels with a round cross section, equals the square of the ratio of the diameters (D0/D1)2 at respectively the beginning (DO) and the end (Dl) of the pressure channel.
• RR reduction ratio
• a RR of 100 or higher preference is given to the use of a RR lower than 60, even more preference to the use of a RR lower than 50, for obtaining a homogeneous continuous extrudate.
• a further measure for obtaining an increased cohesion of the ethylene polymer in the moulded article or in the extrudate is that the the paste is pressed through an opening at a processing temperature of between 80 and 120°C, preferably between 90 and 120 ⁇ C.
• a processing temperature of between 80 and 120°C, preferably between 90 and 120 ⁇ C is that the moulded article or the extrudate is better qualified for an after-treatment consisting in the drawing of the moulded article or the extrudate to obtain a higher tensile strength and E-modulus in the direction of drawing. This treatment is highly advantageous if from the moulded article or from the extrudate filaments, tapes or films are produced that must have a high tensile strength and modulus.
• UHMWPE with an IV of 29 dl/g measured in decalin at 135°C was obtained by polymerizing ethylene at a temperature of -7°C in the presence of a Ziegler catalyst as in US-A-4769433.
• the resulting UHMWPE has a maximum draw ratio of 100. It has a melting point of 141°C measured according to a standard DSC method (highest peak in the DSC diagram) and a melting enthalpy of 237 J/g. The melting enthalpy of the sample of the same ethylene polymer, melted only once and then solidified, measured according to the same standard DSC method is 30% lower.
• the X-ray crystallinity is 81%.
• the ethylene polymer was mixed in the form of a powder with demineralized water to which 1% (wt) Triton* N 101 (nonylphenol-polyethylene oxide) of Rohm & Haas had been added as surface tension reductant.
• the mixing temperature was 25°C.
• the concentration of the water in the paste obtained by the mixing was 39% (vol.).
• the paste was placed in an Instron rheograph the plunger of which is provided with a pressure recorder.
• the capillary of the rheograph has a reduction ratio of 16.
• the half vertex angle of the capillary is 9°20'.
• the round entrance aperture of the capillary has a diameter of 9.6 mm.
• the plunger was moved at a speed of 0.2 cm/min. and the paste was pressed through the capillary and left the device in the form of a moulded article or extrudate.
• the stabilization and pressing temperature was 115°C and the pressure observed during the pressing operation was 55 MPa. After conditioning for 15 minutes at 110°C, the extrudate was drawn at 120°C with a length of 21 mm between the clamps of an Instron drawing device and a drawing speed of 10 mm min.
• the ethylene polymer used was UHMWPE of the HIFAX R 1900 type of the firm of Hercules.
• This ethylene polymer has an IV of 29 dl/g measured in decalin at 135°C and a maximum draw ratio of 16. It has a melting point measured according to a standard DSC (highest peak in the DSC diagram) of 142°C and a melting enthalpy of 240 J/g. The melting enthalpy of the sample of the same ethylene polymer, melted once and subsequently solidified, measured according to the same standard DSC method is 30% lower. The X-ray crystallinity is 82%.
• the ethylene polymer was mixed in the form of a powder with demineralized water to which 1% (wt) Triton* N 101 had been added.
• the concentration of the non-solvent in the paste obtained by the mixing was 39% (vol. ) .
• the paste was extruded as in experiment I.
• the stabilization and pressing temperature was 115°C and the pressure observed during the pressing operation was about 55 MPa.
• the extrudate was conditioned and drawn as in experiment I.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Health & Medical Sciences (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• General Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Textile Engineering (AREA)
• Dispersion Chemistry (AREA)
• Processes Of Treating Macromolecular Substances (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)

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Cited By (4)

Citations (3)

• 1990
  • 1990-08-23 NL NL9001857A patent/NL9001857A/nl not_active Application Discontinuation
• 1991
  • 1991-08-14 WO PCT/NL1991/000150 patent/WO1992003494A1/en not_active Ceased
  • 1991-08-21 TW TW80106645A patent/TW197979B/zh active

Patent Citations (3)

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