WO2002064695A1 - Sealing composition - Google Patents

Sealing composition Download PDF

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Publication number
WO2002064695A1
WO2002064695A1 PCT/GB2002/000591 GB0200591W WO02064695A1 WO 2002064695 A1 WO2002064695 A1 WO 2002064695A1 GB 0200591 W GB0200591 W GB 0200591W WO 02064695 A1 WO02064695 A1 WO 02064695A1
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WO
WIPO (PCT)
Prior art keywords
composition
inductive
copolymer
capacitative
thermoplastic
Prior art date
Application number
PCT/GB2002/000591
Other languages
French (fr)
Inventor
Gerry Mavin
Stephen Glover
John Victor Skilton
Original Assignee
Portola Packaging Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Portola Packaging Limited filed Critical Portola Packaging Limited
Publication of WO2002064695A1 publication Critical patent/WO2002064695A1/en

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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/10—Materials in mouldable or extrudable form for sealing or packing joints or covers
    • 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
    • C08K3/08—Metals
    • 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
    • C08K3/22—Oxides; Hydroxides of metals
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
    • C08L21/00—Compositions of unspecified rubbers
    • 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
    • C08L23/08—Copolymers of ethene
    • 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
    • C08L23/08—Copolymers of ethene
    • C08L23/0846—Copolymers of ethene with unsaturated hydrocarbons containing other atoms than carbon or hydrogen atoms
    • C08L23/0853—Vinylacetate
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
    • C09K2200/02—Inorganic compounds
    • C09K2200/0204—Elements
    • C09K2200/0213—Metals
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
    • C09K2200/02—Inorganic compounds
    • C09K2200/0239—Oxides, hydroxides, carbonates
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
    • C09K2200/06—Macromolecular organic compounds, e.g. prepolymers
    • C09K2200/0615—Macromolecular organic compounds, e.g. prepolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • C09K2200/0617—Polyalkenes
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
    • C09K2200/06—Macromolecular organic compounds, e.g. prepolymers
    • C09K2200/0615—Macromolecular organic compounds, e.g. prepolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • C09K2200/0617—Polyalkenes
    • C09K2200/062—Polyethylene
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K2200/00—Chemical nature of materials in mouldable or extrudable form for sealing or packing joints or covers
    • C09K2200/06—Macromolecular organic compounds, e.g. prepolymers
    • C09K2200/0615—Macromolecular organic compounds, e.g. prepolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
    • C09K2200/0622—Polyvinylalcohols, polyvinylacetates

Definitions

  • the present invention relates to sealing compositions.
  • it relates to sealing compositions suitable for the production of sealing elements which may be softened or melted by inductive and/or capacitative heating so that they are capable of forming a weld or seal between at least two objects.
  • Sealing elements which may be produced using the composition of the present invention are particularly useful as sealing elements for container closures such as metal crowns and plastic caps .
  • Synthetic polymer compositions which are suitable for the production of sealing elements are well known in the art. Such compositions are generally formed by extrusion and then cut into pellets. The pellets are then deposited into closures where they are stamped by means of a die to form an appropriately shaped sealing element. Whilst synthetic polymer compositions which are known in the art can provide sealing elements which provide an adequate seal, it would be advantageous to provide polymer compositions suitable for the production of sealing elements which exhibit improved sealing performance.
  • the present invention provides a composition for the production of a sealing element which may be softened or melted by inductive and/or capacitative heating, and which comprises one or more thermoplastic polyolefin polymers, one or more thermoplastic olefin-vinylester copolymers and particles of one or more inductive and/or capacitative materials.
  • the composition may also comprise one or more thermoplastic elastomers.
  • Thermoplastic elastomers may be introduced in order to vary the hardness of the resultant composition.
  • polymer is not limited to polymers formed from a single monomer but also includes polymers formed from two or more different monomers. It is therefore intended to include within its scope polymers which could be further defined as “copolymers” in accordance with the definition below.
  • polymer compounds identified herein consist essentially of the one or more monomer units identified therewith, it is not intended to exclude the possibility that minor amounts of other monomer units may also be included in the polymer chain, provided that they do not fundamentally alter the physical and chemical properties of the polymer.
  • copolymer refers to polymers formed from two or more monomers.
  • olefin-vinylester copolymer refers to a copolymer formed from one or more olefins (as defined below) and one or more vinylesters (as defined below) .
  • copolymer includes within its scope random, alternating, statistical, graft and block copolymers.
  • olefin means an unsaturated aliphatic hydrocarbon having one or more double bonds. Preferred olefins possess only one double bond. Preferred olefins possess from 2 to 8 carbon atoms. Examples of particularly preferred olefins include; ethylene, propylene, butylene, hexylene and octylene.
  • polyolefin polymer means a polymer (as defined above) formed from one or more olefins (as defined above) .
  • compositions of the present invention are suitable for the production of a sealing element which may be softened or melted by inductive and/or capacitative heating.
  • Inductive heating is a phenomenon which is well known in the art.
  • a current (I) is induced to flow through the conductor.
  • R resistance
  • the electrical energy lost is often converted to heat energy which causes the conductor to heat up.
  • Capacitative heating results from the exposure of a conductor to a variable electric field.
  • the variable electric field causes a current (I) to flow within the conductor which again results in resistive losses which cause the conductor to heat up.
  • induction welding consists of contacting an inductive material with a welding material which is itself in contact with the items to be welded.
  • the inductive material is exposed to a variable magnetic field (for example by exposure to electromagnetic radiation) so that it heats up by induction.
  • the welding material with which it is in contact also heats up.
  • the welding material melts or softens so that it flows into fuller contact with the items to be welded.
  • the welding material re-solidifies to provide a solid weld between the items .
  • the inductive material and welding material will often be different materials, in some cases they may be one and the same material.
  • inductive material means a material whose temperature may be increased by exposure to a variable magnetic field.
  • Capacitative welding works in a similar fashion except that the inductive material is replaced by a capacitative material and the variable magnetic field is replaced by a variable electric field. Again, the variable electric field may be provided by electromagnetic radiation. Although the capacitative material and welding material will often be different materials, in some cases they may be one and the same material. Thus, as used herein, the term "capacitative material" means a material whose temperature may be increased by exposure to a variable electric field.
  • the composition is a homogenous composition of said components .
  • the composition In order to provide a composition which can be conveniently used for inductive or capacitative welding, it is preferable for the composition to have a melting point in the range of from 75 to 120°C.
  • the present invention provides a composition wherein the one or more thermoplastic polyolefin polymers are present in an amount of from 40 to 70% by weight based on the total weight of the composition.
  • the one or more thermoplastic polyolefin polymers are present in an amount of from 50 to 60% by weight based on the total weight of the composition.
  • the present invention provides a' composition wherein the one or more thermoplastic olefin-vinylester copolymers are present in an amount of from 30 to 60% by weight based on the total weight of the composition.
  • the vinylester content of the one or more thermoplastic olefin-vinylester copolymer is low (i.e. from 5 to 18% by weight) it is preferable that said copolymers are present in an amount of from 45 to 60% by weight based on the total weight of the composition.
  • the vinylester content of the one or more thermoplastic olefin-vinylester copolymer is high (i.e. from 18 to 35% by weight) it is preferable that said copolymers are present in an amount of from 30 to 45% by weight based on the total weight of the composition.
  • the present invention provides a composition wherein the one or more inductive and/or capacitative materials are present in an amount of from 15 to 70% by weight based on the total weight of the composition.
  • the one or more inductive and/or capacitative materials are present in an amount of from 20 to 60% by weight based on the total weight of the composition. More preferably, the one or more inductive materials are present in an amount of from 35 to 50% by weight based on the total weight of the composition.
  • the present invention provides a composition wherein one or more thermoplastic elastomers may also be present in an amount of from 10 to 50% by weight based on the total weight of the composition.
  • one or more thermoplastic elastomers are present in an amount of from 15 to 35% by weight based on the total weight of the composition. Elastomers may be added if a softer sealing composition is required.
  • the present invention provides a composition wherein the one or more thermoplastic polyolefin polymers is/are selected from polyethylene, polypropylene, ethylene-propylene copolymer, polybutylene, polyhexylene and polyoctylene .
  • thermoplastic polyolefin polymer is polyethylene.
  • polyethylene may be selected from one or more of high density polyethylene, low density polyethylene or linear low density polyethylene.
  • Particularly preferred polyolefins are those manufactured by single site technology using metallocene catalysts.
  • the present invention provides a composition wherein the one or more thermoplastic olefin-vinylester copolymers is/are selected from olefin-vinylacetate copolymers.
  • the present invention provides a composition wherein the one or more thermoplastic olefin-vinylester copolymers is/are selected from ethylene-vinylester copolymers.
  • the present invention provides a composition wherein the thermoplastic olefin- vinylester copolymer is ethylene-vinylacetate copolymer.
  • the present invention provides a composition wherein the thermoplastic olefin- vinylester copolymer is ethylene-vinylacetate copolymer having a vinyl acetate content of from 5 to 35% by weight, preferably 7 to 30% by weight, more preferably 18 to 30% by weight.
  • a vinyl acetate content of from 18 to 30% by weight is particularly preferred because such copolymers have lower melting points and better adhesion. These properties are important for producing compositions suitable for capacitative or inductive welding.
  • a lower melting point for the olefin-vinylester copolymer results in a lower melting point for the resulting composition making it easier to weld. Improved adhesion or stickiness of the copolymer also provides a composition with better welding properties.
  • the one or more thermoplastic elastomers When used in the composition, preferably have a hardness of from 50 to 90 on the Shore A scale and/or from 25 to 40 on the Shore D scale.
  • the present invention provides a composition wherein the one or more thermoplastic elastomers (if present) is/are selected from polyisoprene, polyisobutylene, polybutadiene, isoprene-isobutylene copolymer (such as crosslinked and normal butyl rubber) , isoprene-butadiene copolymer, styrene-butadiene copolymer, styrene- butadiene-styrene copolymer, styrene-isoprene copolymer, styrene-isoprene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer and ethylene-propylene copolymer and ethylene-propylene- diene terpolymer.
  • polyisoprene polyisobutylene, polybutadiene, isoprene-isobutylene cop
  • the present invention provides a composition wherein the one or more thermoplastic elastomers are selected from styrene-butadiene-styrene copolymer, isoprene-isobutylene copolymer (such as butyl rubber) , styrene-ethylene-butylene-styrene copolymer and ethylene-propylene-diene terpolymer.
  • the one or more thermoplastic elastomers are selected from styrene-butadiene-styrene copolymer, isoprene-isobutylene copolymer (such as butyl rubber) , styrene-ethylene-butylene-styrene copolymer and ethylene-propylene-diene terpolymer.
  • the present invention provides a composition wherein the thermoplastic elastomer is styrene-butadiene-styrene copolymer or ethylene- propylene-diene terpolymer.
  • the present invention provides a composition wherein the one or more inductive and/or capacitative materials is/are selected from inductive and/or capacitative metals and inductive and/or capacitative metallic oxides .
  • the present invention provides a composition wherein the one or more inductive and/or capacitative materials is/are selected from aluminium, aluminum alloys, copper, copper alloys, magnetic iron oxides and magnetic chromium oxides (e.g. Cr 2 0 3 ) .
  • aluminium or copper are used, they should preferably be of the leafing type, i.e. they form layers. These types of aluminium and copper exhibit better heating properties.
  • the present invention provides a composition wherein the inductive and/or capacitative material is aluminium.
  • the inductive and/or capacitative material is aluminium.
  • aluminium particles When aluminium particles are included in the composition they may be added in the form of a paste so as to minimise the safety hazards associated with the handling of finely divided aluminium particles. Alternatively, they may be added in a granulate form wherein they are pre-mixed with a suitable polymer. Aluminium undergoes capacitative rather than inductive heating.
  • the present invention provides a composition wherein the particle size of the one or more inductive and/or capacitative materials is less than lOO m.
  • the particle size is in the range of from 2 to lOO ⁇ m. More preferably 2 to 50 m and most preferably 2 to 30 m. The smaller size is preferred because it results in less wear in the extruders during production.
  • the present invention provides a composition as described above which additionally comprises one or more mineral oils.
  • the mineral oil is a food grade or medicinal grade mineral oil.
  • the mineral oil is preferably paraffin oil. Mineral oils are used to soften the composition and may be employed instead of or in addition to thermoplastic elastomers.
  • composition of the present invention may additionally comprise pigments to improve the visual appearance of the composition, antioxidants and/or stabilisers to maintain its chemical integrity, fillers to add bulk and/or modify its physical characteristics, and plasticisers and/or lubricants such as silicone oils and fluorinated polymers to improve the processability of the composition.
  • suitable fillers/pigments which may be added to the composition include mica, talc, calcium carbonate, clay (such as kaolin) and titanium dioxide.
  • the composition of the present invention may be formed by conventional techniques known in the art for the manufacture of polymer compositions.
  • a preferred process comprises mixing the one or more thermoplastic polyolefin polymers with the one or more thermoplastic olefin-vinylester copolymers and the particles of one or more inductive materials and, optionally, one or more thermoplastic elastomers; blending the mixture to provide a homogenous composition; and extruding the composition through a suitable shaped die. Both single and double screw extruders may be used. Mixing and blending can be carried out in a standard mixer such as a Banbury mixer. The plastic extrudate may conveniently be cut into individual lumps or pellets by a blade positioned directly after the orifice.
  • the composition of the present invention is suitable for forming sealing elements which may be softened or melted by inductive and/or capacitative heating so that they are capable of forming a weld or seal between at least two objects.
  • the present invention provides a process for forming a weld or seal between two or more objects which comprises contacting said objects with a composition as described above, exposing said composition to a variable electric and/or magnetic field so that it is softened or melted by inductive and/or capacitative heating and cooling said composition so that it rehardens to provide a weld or seal between said objects.
  • the variable electric and/or magnetic field may be provided by means of electromagnetic radiation of a suitable frequency. Microwave radiation is particularly preferred.

Abstract

There is described a composition for the production of a sealing element which may be softened or melted by inductive and/or capacitative heating. The composition comprises one or more thermoplastic polyolefin polymers, one or more thermoplastic olefin-vinylester copolymers and particles of one or more inductive and/or capacitative materials.

Description

Sealing Composition
The present invention relates to sealing compositions. In particular, it relates to sealing compositions suitable for the production of sealing elements which may be softened or melted by inductive and/or capacitative heating so that they are capable of forming a weld or seal between at least two objects. Sealing elements which may be produced using the composition of the present invention are particularly useful as sealing elements for container closures such as metal crowns and plastic caps .
Synthetic polymer compositions which are suitable for the production of sealing elements are well known in the art. Such compositions are generally formed by extrusion and then cut into pellets. The pellets are then deposited into closures where they are stamped by means of a die to form an appropriately shaped sealing element. Whilst synthetic polymer compositions which are known in the art can provide sealing elements which provide an adequate seal, it would be advantageous to provide polymer compositions suitable for the production of sealing elements which exhibit improved sealing performance.
In order to address this problem, the present invention provides a composition for the production of a sealing element which may be softened or melted by inductive and/or capacitative heating, and which comprises one or more thermoplastic polyolefin polymers, one or more thermoplastic olefin-vinylester copolymers and particles of one or more inductive and/or capacitative materials.
If desired, the composition may also comprise one or more thermoplastic elastomers. Thermoplastic elastomers may be introduced in order to vary the hardness of the resultant composition.
As used herein, the term "polymer" is not limited to polymers formed from a single monomer but also includes polymers formed from two or more different monomers. It is therefore intended to include within its scope polymers which could be further defined as "copolymers" in accordance with the definition below. Furthermore, whilst the polymer compounds identified herein consist essentially of the one or more monomer units identified therewith, it is not intended to exclude the possibility that minor amounts of other monomer units may also be included in the polymer chain, provided that they do not fundamentally alter the physical and chemical properties of the polymer.
As used herein, the term "copolymer" refers to polymers formed from two or more monomers. Thus, for example, "olefin-vinylester copolymer" refers to a copolymer formed from one or more olefins (as defined below) and one or more vinylesters (as defined below) . The term "copolymer" includes within its scope random, alternating, statistical, graft and block copolymers.
As used herein the term "olefin" means an unsaturated aliphatic hydrocarbon having one or more double bonds. Preferred olefins possess only one double bond. Preferred olefins possess from 2 to 8 carbon atoms. Examples of particularly preferred olefins include; ethylene, propylene, butylene, hexylene and octylene.
As used herein the term "vinyl ester" means a compound of the general formula CH2=CH-C—CO-R, where R is a Cx- C8 alkyl group, preferably methyl or propyl .
As used herein the term "polyolefin polymer" means a polymer (as defined above) formed from one or more olefins (as defined above) .
The compositions of the present invention are suitable for the production of a sealing element which may be softened or melted by inductive and/or capacitative heating.
Inductive heating is a phenomenon which is well known in the art. When a conductor is exposed to a variable magnetic field, a current (I) is induced to flow through the conductor. If the conductor has a resistance (R) the flow of current results in resistive losses which are equal to I2R. The electrical energy lost is often converted to heat energy which causes the conductor to heat up.
Capacitative heating results from the exposure of a conductor to a variable electric field. The variable electric field causes a current (I) to flow within the conductor which again results in resistive losses which cause the conductor to heat up.
The phenomena of inductive and capacitative heating provide the basis for the techniques of induction welding and capacitative welding.
Briefly, induction welding consists of contacting an inductive material with a welding material which is itself in contact with the items to be welded. The inductive material is exposed to a variable magnetic field (for example by exposure to electromagnetic radiation) so that it heats up by induction. As the inductive material heats up, the welding material with which it is in contact also heats up. When it reaches a high enough temperature, the welding material melts or softens so that it flows into fuller contact with the items to be welded. On subsequent cooling, the welding material re-solidifies to provide a solid weld between the items . Although the inductive material and welding material will often be different materials, in some cases they may be one and the same material.
Thus, as used herein, the term "inductive material" means a material whose temperature may be increased by exposure to a variable magnetic field.
Capacitative welding works in a similar fashion except that the inductive material is replaced by a capacitative material and the variable magnetic field is replaced by a variable electric field. Again, the variable electric field may be provided by electromagnetic radiation. Although the capacitative material and welding material will often be different materials, in some cases they may be one and the same material. Thus, as used herein, the term "capacitative material" means a material whose temperature may be increased by exposure to a variable electric field.
In a preferred embodiment of the present invention, the composition is a homogenous composition of said components .
In order to provide a composition which can be conveniently used for inductive or capacitative welding, it is preferable for the composition to have a melting point in the range of from 75 to 120°C.
In another aspect, the present invention provides a composition wherein the one or more thermoplastic polyolefin polymers are present in an amount of from 40 to 70% by weight based on the total weight of the composition. Preferably, the one or more thermoplastic polyolefin polymers are present in an amount of from 50 to 60% by weight based on the total weight of the composition.
In another aspect, the present invention provides a' composition wherein the one or more thermoplastic olefin-vinylester copolymers are present in an amount of from 30 to 60% by weight based on the total weight of the composition. When the vinylester content of the one or more thermoplastic olefin-vinylester copolymer is low (i.e. from 5 to 18% by weight) it is preferable that said copolymers are present in an amount of from 45 to 60% by weight based on the total weight of the composition. When the vinylester content of the one or more thermoplastic olefin-vinylester copolymer is high (i.e. from 18 to 35% by weight) it is preferable that said copolymers are present in an amount of from 30 to 45% by weight based on the total weight of the composition.
In another aspect, the present invention provides a composition wherein the one or more inductive and/or capacitative materials are present in an amount of from 15 to 70% by weight based on the total weight of the composition. Preferably, the one or more inductive and/or capacitative materials are present in an amount of from 20 to 60% by weight based on the total weight of the composition. More preferably, the one or more inductive materials are present in an amount of from 35 to 50% by weight based on the total weight of the composition.
In another aspect, the present invention provides a composition wherein one or more thermoplastic elastomers may also be present in an amount of from 10 to 50% by weight based on the total weight of the composition. Preferably, when present, the one or more thermoplastic elastomers are present in an amount of from 15 to 35% by weight based on the total weight of the composition. Elastomers may be added if a softer sealing composition is required.
In another aspect, the present invention provides a composition wherein the one or more thermoplastic polyolefin polymers is/are selected from polyethylene, polypropylene, ethylene-propylene copolymer, polybutylene, polyhexylene and polyoctylene .
In another aspect, the thermoplastic polyolefin polymer is polyethylene. In this aspect the polyethylene may be selected from one or more of high density polyethylene, low density polyethylene or linear low density polyethylene.
Particularly preferred polyolefins are those manufactured by single site technology using metallocene catalysts.
In another aspect, the present invention provides a composition wherein the one or more thermoplastic olefin-vinylester copolymers is/are selected from olefin-vinylacetate copolymers.
In another aspect, the present invention provides a composition wherein the one or more thermoplastic olefin-vinylester copolymers is/are selected from ethylene-vinylester copolymers.
In another aspect, the present invention provides a composition wherein the thermoplastic olefin- vinylester copolymer is ethylene-vinylacetate copolymer.
In another aspect, the present invention provides a composition wherein the thermoplastic olefin- vinylester copolymer is ethylene-vinylacetate copolymer having a vinyl acetate content of from 5 to 35% by weight, preferably 7 to 30% by weight, more preferably 18 to 30% by weight. A vinyl acetate content of from 18 to 30% by weight is particularly preferred because such copolymers have lower melting points and better adhesion. These properties are important for producing compositions suitable for capacitative or inductive welding. A lower melting point for the olefin-vinylester copolymer results in a lower melting point for the resulting composition making it easier to weld. Improved adhesion or stickiness of the copolymer also provides a composition with better welding properties.
When used in the composition, the one or more thermoplastic elastomers preferably have a hardness of from 50 to 90 on the Shore A scale and/or from 25 to 40 on the Shore D scale.
In another aspect, the present invention provides a composition wherein the one or more thermoplastic elastomers (if present) is/are selected from polyisoprene, polyisobutylene, polybutadiene, isoprene-isobutylene copolymer (such as crosslinked and normal butyl rubber) , isoprene-butadiene copolymer, styrene-butadiene copolymer, styrene- butadiene-styrene copolymer, styrene-isoprene copolymer, styrene-isoprene-styrene copolymer, styrene-ethylene-butylene-styrene copolymer and ethylene-propylene copolymer and ethylene-propylene- diene terpolymer.
In another aspect, the present invention provides a composition wherein the one or more thermoplastic elastomers are selected from styrene-butadiene-styrene copolymer, isoprene-isobutylene copolymer (such as butyl rubber) , styrene-ethylene-butylene-styrene copolymer and ethylene-propylene-diene terpolymer.
In another aspect, the present invention provides a composition wherein the thermoplastic elastomer is styrene-butadiene-styrene copolymer or ethylene- propylene-diene terpolymer.
In another aspect, the present invention provides a composition wherein the one or more inductive and/or capacitative materials is/are selected from inductive and/or capacitative metals and inductive and/or capacitative metallic oxides .
In another aspect, the present invention provides a composition wherein the one or more inductive and/or capacitative materials is/are selected from aluminium, aluminum alloys, copper, copper alloys, magnetic iron oxides and magnetic chromium oxides (e.g. Cr203) .
Where aluminium or copper are used, they should preferably be of the leafing type, i.e. they form layers. These types of aluminium and copper exhibit better heating properties.
In another aspect, the present invention provides a composition wherein the inductive and/or capacitative material is aluminium. When aluminium particles are included in the composition they may be added in the form of a paste so as to minimise the safety hazards associated with the handling of finely divided aluminium particles. Alternatively, they may be added in a granulate form wherein they are pre-mixed with a suitable polymer. Aluminium undergoes capacitative rather than inductive heating.
In another aspect, the present invention provides a composition wherein the particle size of the one or more inductive and/or capacitative materials is less than lOO m. Preferably the particle size is in the range of from 2 to lOOμm. More preferably 2 to 50 m and most preferably 2 to 30 m. The smaller size is preferred because it results in less wear in the extruders during production.
In another aspect, the present invention provides a composition as described above which additionally comprises one or more mineral oils. Preferably the mineral oil is a food grade or medicinal grade mineral oil. When included in the composition, the mineral oil is preferably paraffin oil. Mineral oils are used to soften the composition and may be employed instead of or in addition to thermoplastic elastomers.
It will be apparent to a person skilled in the art that a number of further additives may be included in the composition of the present invention in order to improve its physical and/or chemical properties. Thus, the composition of the present invention may additionally comprise pigments to improve the visual appearance of the composition, antioxidants and/or stabilisers to maintain its chemical integrity, fillers to add bulk and/or modify its physical characteristics, and plasticisers and/or lubricants such as silicone oils and fluorinated polymers to improve the processability of the composition. Examples of suitable fillers/pigments which may be added to the composition include mica, talc, calcium carbonate, clay (such as kaolin) and titanium dioxide.
The composition of the present invention may be formed by conventional techniques known in the art for the manufacture of polymer compositions. A preferred process comprises mixing the one or more thermoplastic polyolefin polymers with the one or more thermoplastic olefin-vinylester copolymers and the particles of one or more inductive materials and, optionally, one or more thermoplastic elastomers; blending the mixture to provide a homogenous composition; and extruding the composition through a suitable shaped die. Both single and double screw extruders may be used. Mixing and blending can be carried out in a standard mixer such as a Banbury mixer. The plastic extrudate may conveniently be cut into individual lumps or pellets by a blade positioned directly after the orifice.
As previously mentioned, the composition of the present invention is suitable for forming sealing elements which may be softened or melted by inductive and/or capacitative heating so that they are capable of forming a weld or seal between at least two objects. Thus, in another aspect, the present invention provides a process for forming a weld or seal between two or more objects which comprises contacting said objects with a composition as described above, exposing said composition to a variable electric and/or magnetic field so that it is softened or melted by inductive and/or capacitative heating and cooling said composition so that it rehardens to provide a weld or seal between said objects. The variable electric and/or magnetic field may be provided by means of electromagnetic radiation of a suitable frequency. Microwave radiation is particularly preferred.

Claims

Claims
A composition for the production of a sealing element which may be softened or melted by inductive and/or capacitative heating and which comprises one or more thermoplastic polyolefin polymers, one or more thermoplastic olefin- vinylester copolymers and particles of one or more inductive and/or capacitative materials.
A composition as claimed in claim 1 wherein the one or more thermoplastic polyolefin polymers are present in an amount of from 40 to 70% by weight based on the total weight of the composition.
3. A composition as claimed in any preceding claim wherein the one or more thermoplastic olefin- vinylester copolymers are present in an amount of from 30 to 60% by weight based on the total weight of the composition.
4. A composition as claimed in any preceding claim wherein the one or more inductive and/or capacitative materials are present in an amount of from 15 to 70% by weight based on the total weight of the composition.
5. A composition as claimed in any preceding claim wherein one or more thermoplastic elastomers are also present in an amount of from 10 to 50% by weight based on the total weight of the composition.
6. A composition as claimed in any preceding claim wherein the one or more thermoplastic polyolefin polymers is/are selected from polyethylene, polypropylene, ethylene-propylene copolymer, polybutylene, polyhexylene and polyoctylene .
7. A composition as claimed in any preceding claim wherein the one or more thermoplastic olefin- vinylester copolymers is/are selected from olefin-vinylacetate copolymers.
8. A composition as claimed in any preceding claim wherein the one or more thermoplastic olefin- vinylester copolymers is/are selected from ethylene-vinylester copolymers.
9. A composition as claimed in any preceding claim wherein the thermoplastic olefin-vinylester copolymer is ethylene-vinylacetate copolymer.
10. A composition as claimed in any preceding claim wherein the one or more inductive and/or capacitative materials is/are selected from metals and metallic oxides.
11. A composition as claimed in claim 5 wherein the one or more thermoplastic elastomers is/are selected from polyisoprene, polyisobutylene, polybutadiene, isoprene-isobutylene copolymer (such as crosslinked and normal butyl rubber) , isoprene-butadiene copolymer, styrene-butadiene copolymer, styrene-butadiene-styrene copolymer, styrene-isoprene copolymer, styrene-isoprene- styrene copolymer, styrene-ethylene-butylene- styrene copolymer, ethylene-propylene copolymer and ethylene-propylene-diene terpolymer.
12. A composition as claimed in any preceding claim wherein the one or more inductive and/or capacitative materials is/are selected from aluminium, aluminium alloys, copper, copper alloys, magnetic iron oxides and magnetic chromium oxides .
13. A composition as claimed in any preceding claim wherein the inductive and/or capacitative material is aluminium.
14. A composition as claimed in any preceding claim wherein the particle size of the one or more inductive and/or capacitative materials is less than lOO m.
15. A composition as claimed in any preceding claim which additionally comprises one or more mineral oils .
16. A composition as claimed in claim 15 wherein the mineral oil is paraffin oil.
17. A composition as claimed in any preceding claim which additionally comprises one or more additives selected from pigments, antioxidants, fillers, stabilisers, plasticisers and lubricants .
18. A process for forming a composition as claimed in any one of claims 1 to 17 which comprises mixing one or more thermoplastic polyolefin polymers with one or more thermoplastic olefin-vinylester copolymers and particles of one or more inductive materials and, optionally one or more thermoplastic elastomers, blending the mixture to provide a homogenous mixture and extruding the mixture through a suitable die.
19. A process for forming a weld or seal between two or more objects which comprises contacting said objects with a composition as claimed in any one of claims 1 to 17, exposing said composition to a variable electric and/or magnetic field so that it is softened or melted by inductive and/or capacitative heating and cooling said composition so that it rehardens to provide a weld or seal between said objects
20. An object which comprises two or more parts joined by a sealing element formed from a composition as claimed in any one of claims 1 to 17.
PCT/GB2002/000591 2001-02-15 2002-02-11 Sealing composition WO2002064695A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB0103771.2 2001-02-15
GB0103771A GB2376689A (en) 2001-02-15 2001-02-15 Sealing composition

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WO2002064695A1 true WO2002064695A1 (en) 2002-08-22

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DE3414108A1 (en) * 1983-04-15 1984-10-25 Bixby International Corp., Newburyport, Mass. Shoe reinforcement
US4693775A (en) * 1986-03-06 1987-09-15 United Technologies Automotive, Inc. Hot melt, synthetic, magnetic sealant
JPS64164A (en) * 1987-06-22 1989-01-05 Mitsubishi Cable Ind Ltd Electroconductive composition
JPH061964A (en) * 1992-06-17 1994-01-11 Mitsui Toatsu Chem Inc Hot-melt joint sealant

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US3391846A (en) * 1963-08-08 1968-07-09 Du Pont Heating with antiferromagnetic particles in a high frequency magnetic field
JPS5853935A (en) * 1981-09-28 1983-03-30 Tokyo Ink Kk Electrically conductive and heat-weldable resin composition for plastic and metal
NL9000714A (en) * 1990-03-27 1991-10-16 Stamicarbon Mixt(s). of thermoplastic and ferrite cpd. fusible by EM field energy - useful for welding non-conductive materials and as coating compsn.
DE60122188T2 (en) * 2000-05-02 2007-07-05 Ashland Licensing and Intellectual Property LLC, Dublin TEMPERATURE-CONTROLLED INDUCTION HEATING OF POLYMERIC MATERIALS

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DE3414108A1 (en) * 1983-04-15 1984-10-25 Bixby International Corp., Newburyport, Mass. Shoe reinforcement
US4693775A (en) * 1986-03-06 1987-09-15 United Technologies Automotive, Inc. Hot melt, synthetic, magnetic sealant
JPS64164A (en) * 1987-06-22 1989-01-05 Mitsubishi Cable Ind Ltd Electroconductive composition
JPH061964A (en) * 1992-06-17 1994-01-11 Mitsui Toatsu Chem Inc Hot-melt joint sealant

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GB2376689A (en) 2002-12-24
GB0103771D0 (en) 2001-04-04

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