WO2008000493A1

WO2008000493A1 - Adhesion of polymer structures

Info

Publication number: WO2008000493A1
Application number: PCT/EP2007/005768
Authority: WO
Inventors: Gerardus Lilian Maria Vroomen; Dagmer Koppler
Original assignee: Dsm Ip Assets B.V.
Priority date: 2006-06-29
Filing date: 2007-06-29
Publication date: 2008-01-03

Abstract

The present invention relates to an article comprising at least a first polymer structure adhered to a second polymer structure which second polymer structure comprises a styrene based thermoplastic elastomer, a polyolefin and a metal oxide or metal hydroxide. The metal oxide or metal hydroxide is chosen from Zn- or Mg-(oxide or hydroxide). The polyolefin chosen from a polyolefin homo or copolymer, preferably a propylene homo or copolymer. The styrene based thermoplastic elastomer is chosen from SBS, SEBS, SEPS, SIBS or mixture thereof. The second polymer structure may further comprise a thermoplastic material, a thermoset rubber, a thermoplastic elastomer or mixtures thereof. The article is preferably a laminate, a sheet, a roofing sheet, a film, a seal or a hose.

Description

ADHESION OF POLYMER STRUCTURES

The present invention relates to articles comprising a first polymer structure adhered to a second polymer structure. The present invention further relates to a composition comprising a styrene based thermoplastic elastomer. The present invention also relates to the use of the composition as adhesive composition. The present invention further relates to the use of the composition in laminates, weather strips, sheets, roofing sheets, films, seals or hoses.

Articles comprising a first polymer structure adhered to a second polymer structure are known from for example WO-A-02051634.

In WO-A-02051634 sealing structures for an automobile are disclosed in which a first structure, made of EPDM blended with a semicrystalline random adhesive copolymer, is adhered to a second polymer structure comprising a dynamically vulcanized thermoplastic elastomer. A disadvantage is that the adhesive properties between the polymer structures are still not satisfying. Moreover the elastic properties of the EPDM blended with the semicrystalline random adhesive copolymer will be affected negatively.

There is thus a continuing need for improved adhesion between polymer structures, for example between two EPDM polymer structures or between an EPDM polymer structure and structure of a polymer material with a different composition. There is moreover a continuing need for improving polymer compositions to provide excellent adhesion properties between polymer structures of the same or different polymeric materials while keeping acceptable mechanical properties. Preferably, mechanical properties like for example the elongation at break or the tensile strength are also improved.

The object of the present invention is to provide an article comprising at least a first polymer structure adhered to a second polymer structure which polymer structure shows excellent adhesion properties and in many cases also an improved elongation at break. This object is achieved in that the second polymer structure comprises a styrene based thermoplastic elastomer, a polyolefin and a metal oxide or a metal hydroxide.

Surprisingly it has been found that articles, comprising at least a first polymer structure adhered to a second polymer structure which second polymer structure comprises a styrene based thermoplastic elastomer, a polyolefin and a metal oxide or metal hydroxide, provide excellent adhesive properties and in many cases also a significantly improved elongation at break.

For the purpose of this invention, with a structure is meant a solid component in any shape, for example in the shape of a film, profile or sealing system. Styrene-based thermoplastic elastomers are for example block copolymers or terpolymers having one or two terminal polymeric blocks of for example polystyrene or poly-alpha-methylstyrene, and at least one non-terminal block of an elastomeric polymer, for example polybutadiene or polyisoprene. Typical examples of such block copolymers are those of general form polystyrene-polybutadiene- polystyrene (SBS), polystyrene-poly(ethylene/propylene) (SEP), polystyrene- polyisoprene-polystyrene (SIPS), poly-alpha-methylstyrene-polybutadiene-poly-alpha- methylstyrene, polystyrene-poly(ethylene-propylene)-polystyrene (SEPS), polystyrene- poly(ethylene/butylenes)-polystyrene (SEBS), polystyrene- poly(ethylene/ethylene/propylene)-b-polystyrene (SEEPS), polystyrene-polyisobutylene- polystyrene (SIBS) or crosslinkable styrenic block copolymers produced by Kuraray Co., Ltd under the trademark Septon V. These styrene block copolymers are commercially available from Kraton Polymers LLC under the trademark KRATON, from Dynasol Elastomers under the trademark Calprene, from Kaneka Corporation under the trademark SIBSTAR and from Kuraray Co., Ltd under the trademark Septon. Preferably polystyrene-poly(ethylene/butylenes)-polystyrene (SEBS), polystyrene- polybutadiene-polystyrene (SBS), polystyrene-polyisobutylene-polystyrene (SIBS) or mixtures thereof are used as styrene based thermoplastic elastomer.

The polyolefin in the second polymer structure of the present invention is for example a polyolefin homo or copolymer, preferably an ethylene or propylene homo or copolymers. More preferably a propylene homo or copolymer.

The polyolefin homo- and copolymers can be prepared with a Ziegler- Natta catalyst, a metallocene catalyst or with another single site catalyst.

Examples of ethylene homopolymers are, low-density polyethylene (LDPE) or high-density polyethylene (HDPE). Examples of ethylene copolymers are very low-density polyethylene (VLDPE) , linear low-density polyethylene (LLDPE) or copolymers of ethylene and an alpha-olefin comonomer with 3-20 carbon atoms. Ethylene/alpha- olefin copolymers for example refer to a class of ethylene based copolymers with a density of less than about 0.93 g/cm³ at a molecular weight (Mw) greater than about 20,000. The ethylene/alpha-olefin copolymers preferably have densities from aboutθ.86 to about 0.92 g/cm³. More preferably the ethylene/alpha-olefin copolymers have densities from about 0.88 to about 0.91 g/cm³. The ethylene/alpha- olefin copolymers for example comprise from 95 to 67 parts by weight ethylene and from 5 to 33 parts by weight of an alpha-olefin having from 3 to 8 carbon atoms. Preferably the ethylene/alpha-olefin copolymers comprise from 92 to 65 parts by weight ethylene and from 8 to 35 parts by weight of an alpha-olefin having from 3 to 8 carbon atoms. More preferable the ethylene/alpha-olefin copolymers comprise from 90 to 65 parts by weight ethylene and from 10 to 35 of an alpha-olefin having from 3 to 8 carbon atoms. Examples of alpha-olefins having 3 to 8 carbon atoms are propene, 1-butene, 1-pentene, 1-hexene, and 1 -ethylene-propylene copolymers, ethylene-octene. Commercially available ethylene copolymers are for example EXACT™ or ENGAGE™.

An example of a propylene homopolymer is polypropylene. The propylene homopolymer preferably has an isotactic index, determined by measurement of the solubility in xylene, greater than 85 and more preferably greater than 90. It is preferable for the propylene polymer to have an MWD greater than 5 and generally between 5 and 50. Propylene copolymers include at least two different types of monomers, one of which is propylene, the other which is for example ethylene resulting in propylene-ethylene copolymers. An example of a propylene copolymer with a high ethylene monomer content, is for example known as a reactor TPO and is commercially available under the trademark Hifax®, Adflex® and Softell®. The propylene copolymer may however also comprise other co- monomers than ethylene for example higher alpha-olefins ranging from C₄ to C₂o, for example, 1-butene, 4-methyl-1-pentene, 1-hexene, octene and 1-decene, or mixtures thereof, for example. Preferably, ethylene is copolymerized with propylene, so that the propylene copolymer includes propylene monomer units and ethylene monomer units. In a preferred embodiment, the propylene copolymer contains at least 75 wt% of propylene-monomer units. More preferred the propylene copolymer comprises from 75 to 95 wt% propylene monomer units and from about 5 to 25 wt% of linear or branched alpha-olefin monomer units other than propylene having 2 or from 4 to 20 carbon atoms. Preferably said alpha-olefin is ethylene. The propylene copolymers may be random. The random propylene copolymers preferably have a narrow molecular weight distribution (MWD) for example between 1.5 and 5.0, with a preferred MWD between about 1.5 and 3.2. The random propylene copolymers may comprise isotactically propylene units.

The crystallinity of the random propylene copolymers, measured by the heat of fusion (DSC), is preferably from 2 to 65 % of homoisotactic polypropylene, preferably between 5 to 40 %. The heat of fusion is, for the purpose of this invention, measured by DSC according to the test standard ASTM D3417-97. The random propylene copolymers preferably comprise from about 80 to 94 wt% propylene monomer units and from 6 to 20 percent wt% of an alpha-olefin monomer unit, more preferably, from 84-90 wt% propylene monomer units and from 10-16 wt% of alpha- olefin monomer units. Preferably the alpha-olefin is ethylene. There is no particular limitation on the method for preparing the propylene copolymers. The propylene copolymers may be prepared by copolymerising propylene and the alpha-olefin having 2 or from 4 to 20 carbon atoms, preferably ethylene, in a single stage or multiple stage reactor. Polymerisation methods include high pressure, slurry, gas, bulk, or solution phase, or a combination thereof, using a traditional Ziegler-Natta catalyst or a single- site, metallocene catalyst system. The catalyst used is preferably one, which has a high isospecificity. Preferably a metallocene catalyst system is used. The polymerisation may be carried out by a continuous or batch process and may include use of chain transfer agents, scavengers, or other such additives as deemed applicable. The above-mentioned random propylene copolymers are preferably prepared by the process described in EP-A-969043. These random propylene copolymers are commercially available for example under the trademark Vistamaxx®. The metal oxide or metal hydroxide in the second polymer structure of the present invention is for example an oxide or hydroxide from metals such as magnesium (Mg), zinc (Zn), aluminium (Al), calcium (Ca) or tin (Sn). Preferred are Ca or Mg present as oxide or hydroxide. More preferred is Mg-oxide or-hydroxide. The metal oxide or metal hydroxide is for example present in an amount of 1-75 wt% based on the total weight of the composition used for the second polymer structure. Preferably it is present in an amount of 2-68 wt% based on the total weight of the composition. More preferably it is present in an amount of 5-40 wt% based on the total weight of the composition.

The second polymer structure may further comprise a thermoplastic material, a thermoset rubber, a thermoplastic elastomer or mixtures thereof. Examples of thermoplastic materials are polyurethane, polystyrene and its derivatives, polyimide, polyamide, polyphenylene ether, polycarbonate, styrene- acrylonitrile copolymers, polyoxymethylene, polyethylene terephthalate, polybutylene terephthalate, polyether ether ketone, polyphenylene oxide or fluoropolymers.

Examples of thermoset rubbers are polybutadiene, EPM, EPDM, styrene butadiene, isoprene, trans-isoprene, acrylonitrile rubber, halogenated rubber such as brominated or chlorinated isobutylene-isoprene copolymer rubber, urethane rubber, epichlorohydrine terpolymer rubber, polychloroprene, butadiene styrene vinyl pyridine rubber, natural rubber or mixtures thereof. Preferably EPM or EPDM is used as thermoset rubber. Examples of thermoplastic elastomers are (TPE's) are etherester based TPE's, urethane based TPE's, olefin based TPE's or dynamically vulcanized TPE's.

Examples of olefine based thermoplastic elastomer comprise at least one polyolefin and at least one elastomer. In case that the elastomer is not vulcanised the thermoplastic elastomer is called a TPO. In case that the elastomer is dynamically vulcanised the thermoplastic elastmer is called a dynamically vulcanised TPE or TPV. Examples of polyolefins are homopolymers of ethylene or propylene, copolymers of ethylene and propylene, copolymers of ethylene and an alpha-olefin comonomer with 4-20 carbon atoms or copolymers of propylene and an alpha-olefin comonomer with 4-20 carbon atoms. In case of a copolymer, the content of propylene in said copolymer is preferably at least 75 wt%. Polyolefin homo- and copolymers can be prepared with a Ziegler-Natta catalyst, a metallocene catalyst or with another single site catalyst. Preferably, polypropylene, polyethylene or mixtures thereof are used as polyolefin. More preferably polypropylene is used as polyolefin. The amount of polyolefin is for example less than 50% by weight relative to the total weight the thermoplastic elastomer. Preferably the amount of polyolefin is between 1 and 40% by weight, more preferably between 5 and 30% by weight relative to the total weight the thermoplastic elastomer.

Examples of the elastomers suitable in the olefin based thermoplastic elastomer are ethylene-propylene copolymers, hereinafter called EPM, ethylene- propylene-diene terpolymers, hereinafter called EPDM, styrene-butadiene-styrene rubber (SBS), nitrile butadiene rubber, isobutene-isoprene rubber, styrene-ethylene- butylene-styrene block copolymers (SEBS), butyl rubber, isobutylene-p-methylstyrene copolymers or brominated isobutylene-p-methylstyrene copolymers, natural rubber or blends of these. Preferably, EPDM or EPM is used as elastomer. Most preferably, EPDM is used as elastomer. The EPDM preferably contains 40-80 parts by weight ethylene monomer units, 58-18 parts by weight monomer units originating from an alpha-olefin and 2-12 parts by weight monomer units originating from a non-conjugated diene whereby the total weight of the ethylene monomer units, the alpha-olefin and the non-conjugated diene is 100. As alpha-olefin use is preferably made of propylene. As non-conjugated diene use is preferably made of dicyclopentadiene (DCPD)₁ 5-ethylidene-2-norbomene (ENB), vinylnorbomene (VNB), or mixture of these. In a dynamically vulcanized TPE the elastomer is dynamically vulcanized in the presence of a curing agent such as, sulfur, sulfurous compounds, metal oxides, maleimides, phenol resins, siloxane or peroxides.

The amount of curing agent is preferably between 0,02 and 5% by weight and more preferably between 0,05 and 2% by weight relative to the total weight of the thermoplastic elastomer. A co-agent may also be used during vulcanization of the elastomer. Examples of suitable co-agents are divinyl benzene, sulphur, p-quinondioxime, nitrobenzene, diphenylguanidine, triarylcyanurate, trimethylolpropane-N.N-m-phenylenedirnaleimide, ethyleneglycol dimethacrylate, polyethylene dimethacrylate, trimethylolpropane trimethacrylate, arylmethacrylate, vinylbutylate and vinylstearate. The amount of co-agent is preferably between 0 and 2.00% by weight of the total weight of the thermoplastic elastomer composition. In case that a dynamically vulcanised thermoplastic elastomer is chosen, the hardness varies between 20 Shore A and 60 shore D. Preferably the hardness varies between 30 shore A and 50 Shore D. More preferably the hardness varies between 40 Shore A and 40 Shore D.

The second polymer structure according to the present invention for example comprises between 10-55 wt% of a styrene based TPE, between 10-60 wt% of a propylene copolymer and between 10-60 wt% paraffin oil and between 1-75 wt% of metal (oxide or hydroxide). The second polymer structure preferably comprises between 14-48 wt% of a styrene based TPE, between 15-55 wt% propylene copolymer, between 15-55 wt% of oil and between 2-68 wt% metal (oxide or hydroxide). The second polymer structure more preferably comprises between 20-40 wt% of a styrene based TPE, between 24-50 wt% propylene copolymer, between 20-50 wt% of oil and between 5-40 wt% metal (oxide or hydroxide)

The article according to the present invention comprises a first polymer structure comprising a thermoplastic material, a thermoset rubber, a thermoplastic elastomer or mixtures thereof. The thermoplastic material and the thermoplastic elastomer are fully described herein above. Preferably the first polymer structure comprises a thermoset rubber. Examples of thermoset rubbers are polybutadiene, ethylene-propylene copolymers (EPM), ethylene-propylene-diene terpolymers (EPDM), styrene butadiene, isoprene, trans-isoprene, acrylonitrile rubber, halogenated rubber such as brominated or chlorinated isobutylene-isoprene copolymer rubber, urethane rubber, epichlorohydrine terpolymer rubber, polychloroprene, butadiene styrene vinyl pyridine rubber, natural rubber or mixtures thereof. Most preferred EPM or EPDM is used as thermoset rubber. The first polymer structure may for instance further comprise a polyolefin. Polyolefins are fully described herein above for the second polymer structure. Preferably, the first polymer structure consists essentially of a thermoset rubber.

The first and second polymer structures according to the present invention may contain customary additives. Examples of such additives are reinforcing and non-reinforcing fillers, plasticizers, antioxidants, stabilizers, oil, antistatic agents, waxes, foaming agents, pigments, flame retardants, antiblocking agents and other known agents and are described in the Rubber World Magazine Blue Book, and in Gaethter et al., Plastics Additives Handbook (Hanser 1990). Examples of suitable fillers are calcium carbonate, clay, silica, talc, titanium dioxide, and carbon, in particular carbon black. Examples of suitable oils are paraffinic oil, naphthenic oil, aromatic oil obtained from petroleum fractions. As paraffinic oil for example Sunpar ™ oil may be used. Also highly hydrogenated oil in which the concentration of aromatic compounds is preferably less than 4 wt.% and the concentration of polar compounds is less than 0.3 wt.% may be used. Such oils are for example PennzUltra™ 1199, supplied by Pennzoil in the United States of America now known under the name FHR Ultra™

1199, supplied by Flint Hill Resources, in the United States of America. The amount of oil depends on the required hardness of the polymer structures.

Examples of antiblocking agents are natural silica, fluoropolymers, silicon oil, stearates for example zinc stearate or calcium stearate or fatty acid amides for example kemamide™. Another additive that can optionally be added is a Lewis base such as for instance a metal carbonate or hydrotalcite.

The article according to the present invention may comprise more than one polymer structure be adhered to the second polymer structure. In that case the polymer structures may comprise the same or different polymeric materials chosen from a thermoplastic material, a thermoset rubber, a thermoplastic elastomer or mixtures thereof. Those polymeric materials are fully described hereinabove.

The polymer structures according to the present invention are defined herein to include any substantially flat structure that may be adhered to one another, such as films which include sheets, layers and the like. The term polymer structure also includes any non-flat structure, such as a molded part, extruded or calendering part. The polymer structures of the present invention are preferably extruded, molded or calendering parts.

The extruded parts are for example used in vehicle sealing systems, known as glass run channels, door seals or belt line seals. The fabrication of the glass run channel, door seal or belt line seal may include coloring, low friction coating, or thermoplastic over-molding. The resulting sealing systems have combinations of properties rendering them superior and unique.

The article according to the present invention for example comprises at least one EPDM or TPV extruded part, which is adhered to a molded part comprising styrene-ethylene-butadiene-styrene (SEBS), a propylene copolymer and a metal oxide or metal hydroxide.

The article according to the present invention is for example a laminate, a sheet, a roofing sheet, a film, a seal or a hose. The article according to the present invention is more preferably a seal for example a weather seal for an automobile.

The present invention further relates to a polymer composition comprising a styrene based thermoplastic elastomer, a polyolefin and a metal oxide or metal hydroxide.

Styrene based thermoplastic elastomers are fully described herein above. Preferred are SBS, SEBS, SEPS, SIBS or mixtures thereof.

The metal oxide or metal hydroxide is also fully described herein above. Preferably the metal oxide or hydroxide present in the composition according to the present invention is chosen from zinc-, magnesium-, aluminum-, calcium- or tin- oxide or hydroxide. A metal oxide or hydroxide of magnesium or calcium is preferred. The polymer composition according to the present invention may comprise the metal oxide or metal hydroxide in an amount of 1-75 wt% based on the total weight of the polymer composition. Preferably the polymer composition comprises from 2-68 wt% of the metal oxide or metal hydroxide based on the total weight of the polymer composition. More preferably the polymer composition comprises from 5-40-wt% or even more preferably 8-40 wt% of the metal oxide or metal hydroxide based on the total weight of the polymer composition.

The polyolefin present in the polymer composition according to the present invention is chosen from a polyolefin homo or copolymer as described in full herein above. Preferably the polyolefin is a propylene homo or copolymer. More preferably the polyolefin is a propylene copolymer as described in full herein above. The polymer composition according to the present invention may further comprise a thermoplastic material, a thermoplastic elastomer, a thermoset rubber or mixtures thereof. Examples of thermoplastic materials, thermoplastic elastomers and thermoset rubbers are fully described herein above. The present invention also relates to the use of the second polymer structure as an adhesive structure.

The present invention further relates to the use of the article according to the invention in the form of laminates, weather strips, sheets, roofing sheets, films, seals or hoses. The invention also relates to a process for the production of an article according to the invention, comprising injection molding a composition comprising a styrene based thermoplastic elastomer, a polyolefin and a metal oxide or metal hydroxide into a mold onto a first polymer structure comprising a thermoset rubber.

The mold temperature and the melt temperature are preferably chosen such that there is a good balance between the adhesion, which improves with increasing the temperature, and the integrity of the article produced by the process which decreases with increasing temperature. Another factor to take into account for choosing the mold temperature is the injection molding cycle time. It is desirable that the article may be removed from the mold as quickly as possible after having been formed.

The thermoset rubber structure may be prepared by any method known in the art, for example by extrusion, injection molding or compression molding.

The invention will be illustrated by the following examples without being restricted thereto.

Experimental

Compounds for examples 1 through 10 in table 1 were prepared on a Berstorff ZE 5OA corotating twin screw extruder having L/D ratio of 42/1 at a screw speed of 350 rpm and throughput rate of 350 kg/hour. The process oil and SEBS or SEBS/SIBS were premixed in a blender prior to twin screw melt blending with other ingredients. The melt temperature during twin screw extrusion was found to be roughly around 240⁰C.

The following describes the raw materials used in the examples: - SEBS: Kraton G 1651 from Kraton Polymers LLC - SIBS: Sibstar 103T from Kaneka Corporation - Maleic anhydride grafted SEBS: Kraton FG1901X from Kraton Polymers LLC

- Polypropylene homopolymer: HD120MO from Borealis

- Polypropylene copolymers: Hifax CA 60 A and PP random copolymer Moplen RP340N from Basell - Mineral oil: Ondina 941 from Shell

- High Molecular Weight Mineral Oil: Pioneer 1135 from Hansen & Rosenthal

- Calcium carbonate: Omyacarb 5 AV from Omya

- Silica: Aerosil R8200 from Degussa

- Magnesium hydroxide (Mg(OH)₂: Magnifin HIOA from Martinswerk - Magnesium oxide (MgO): Magnesia 2923 from Magnesia

- Additive: a blend of Irganox 1010, lrgafos 168, and Chimassorb 119 from Ciba Specialty Chemicals at a ratio of 1 : 1 : 1 for heat and UV stabilization.

- Carbon black concentrate: UN 2014 (EVA carrier with 50 wt% loading of carbon black) from Cabot. - Sarlink® 6165NAT (comparative example A) is a standard EPDM based thermoplastic vulcanizates (TPVs) manufactured by DSM Thermoplastic Elastomers under the trademark Sarlink®.

- Santoprene® 121-79W233 (comparative example B) and Santoprene® 121- 65W233 (comparative example C) are specialty EPDM adhesive TPVs manufactured by ExxonMobil under the trademark Santoprene®.

Thermoset EPDM sheets were obtained by vulcanizing a typical commercial glass run channel EPDM compound at 180⁰C for 10 minutes in plaques of 2.0 +/- 0.2 mm thickness using a compression molding machine. The hardness of the EPDM sheets after vulcanization was measured to be about 65 shore A. To measure the level of adhesion between vulcanized EPDM and thermoplastic elastomer compounds, an insert molding technique was used. A fresh cut vulcanized EPDM strip of 100 mmX40 mmX2 mm was first inserted into the mold cavity (150 mmXIOO mmX2 mm) of the injection molding machine. After closing the mold, the thermoplastic elastomer (TPE) compound was injected into the empty portion of the mold cavity through a cloth-hanger gate to form a melt bond to the EPDM polymer structure (strip previously inserted). The typical molding conditions are shown below:

- Injection molding machine temperature setting: 220-230-240-240⁰C (rear-middle- front-nozzle) - Injection pressure: 720 bar - Holding pressure: 360 bar

- Injection time: 0.2 second

- Packing/Holding time: 8 seconds

- Cooling time: 15-18 seconds - Mold temperature: 40⁰C or 67⁰C

- Melt temperature was found to be roughly around 238°C by a hand held thermocouple probe.

After conditioning of the injection molded EPDM-TPE plaques at room temperature for at least 24 hrs, ISO 37:2005 (E) Type 2 dumbbells were cut out of the molded plaques with the interface between EPDM and TPE positioned around the middle of the dumbbells. The adhesion or bond strength between the EPDM and TPE was measured following ISO 37:2005 (E) with a crosshead speed of 200 mm/min. In the results section, the adhesion (or bond) strength between the EPDM structure and the TPE structure is referred to as adhesion to EPDM. An optical strain gage was used to measure the level of elongation at break for each dumbbell shaped specimen with the interface between EPDM and TPE positioned around the middle of the dumbbell; this elongation at break is referred to as the elongation at break (adhesion test) in the results section. The test was repeated three times for each compound and the average values are adhesion to EPDM and the elongation at break (adhesion test) as given in the results section.

The tensile strength and elongation at break of each thermoplastic elastomer compound alone was also determined following ISO 37:2005 (E) standard on injection molded plaques in the direction parallel to flow and are referred to in the results section as tensile strength and elongation at break respectively. The hardness of all the thermoplastic elastomer compounds was measured at room temperature on injection molded plaques according to DIN 53505:2000 standard with 3 second delay (hardness in the results section)

Results Comparative examples 1 through 4 are typical SEBS compounds containing SEBS, processing oil, polypropylene homopolymer or copolymer(s) and stabilization additive. As shown in table 1 , these compounds were found to have adhesion levels similar to the comparative examples A to C conducted using commercially available TPVs.. In example 5, 80 parts of magnesium oxide was added to the formulation. Compared to comparative example 4, this compound was found to have increased level of adhesion and elongation at break in the adhesion test. This translates into higher level of energy required to break the bond between the EPDM structure and the thermoplastic elastomer compound. Similarly, the addition of 10 and 80 parts of magnesium hydroxide in examples 6 and 7 respectively was found to yield much increased level of adhesion to EPDM compared to the compound containing no magnesium hydroxide (comparative example 4) and the comparative examples A through C conducted using commercially available TPVs designed for melt bonding to EPDM thermoset rubbers. Again higher level of adhesion and higher elongation at break translates into higher level of energy required to break the bond between the EPDM structure and the thermoplastic elastomer compound.

In example 8, the process oil was changed from Ondina 941 to Pioneer 1135 (high molecular weight mineral oil). The change in process oil did not affect the adhesion to EPDM significantly. This can be seen by comparing example 8 to example 7 in table 1.

Overall, all the compounds containing metal oxide or metal hydroxide, in particular magnesium oxide or magnesium hydroxide were found to have a much higher level of adhesion and elongation at break in the adhesion tests compared to those that do not contain metal oxide or metal hydroxide, in particular magnesium oxide or magnesium hydroxide.

With example 9 in table 2, SEBS was partially replaced by SIBS. A small amount of maleic anhydride grafted SEBS was also added to the formulation. This compound containing 20 parts of magnesium hydroxide and only 50 parts of polypropylene copolymer was found to have a much lower hardness (40 shore A) compared to the thermoplastic elastomer compounds listed in table 1. In general, lower hardness compounds with a lower amount of thermoplastic polymer such as polypropylene homopolymer and/or copolymer tend to have lower level of adhesion to thermoset rubbers. Surprisingly, this low hardness compound exhibited about 3.0 MPa adhesion level, comparable to commercially available TPVs (Comparative examples A through C ) of a much higher hardness and the SEBS compounds of a much higher hardness to which magnesium oxide and magnesium hydroxide had not been added (comparative examples 1 through 4). In many automotive sealing system applications, softer molding compounds are especially desirable for bonding to EPDM sponge profiles which are soft and flexible. In another set of experiments as shown in table 3, the same compound used in example 7 was molded against the thermoset EPDM strip at a higher mold temperature. Increasing the mold temperature was found to increase the bond strength.

Table la.Compound composition, properties and bond strength to EPDM at mold temperature 4O⁰C

Table i b.Compound composition, properties and bond strength to EPDM at mold temperature 40°C

Table 2. Composition, properties and bond strength of low hardness adhesive compound

Table 3. Effect of mold temperature on bond strength to EPDM

Claims

1. Article comprising at least a first polymer structure adhered to a second polymer structure which second polymer structure comprises a styrene based thermoplastic elastomer, a polyolefin and a metal oxide or metal hydroxide, and which first polymer structure comprises a thermoset rubber.

2. Article according to claims 1 wherein the first polymer structure further comprises a polyolefin.

3. Article according to any claim 1 or 2 characterized in that the metal oxide or metal hydroxide is chosen from Zn-, Al-, Ca-, Sn-or Mg-(oxide or hydroxide).

4. Article according to any one of the claims 1-3 characterized in that the second polymer structure comprises a polyolefin chosen from a polyolefin homo or copolymer.

5. Article according to claim 4 characterized in that the polyolefin copolymer is chosen from a propylene homo or copolymer.

6. Article according to any one of the claims 1-5 characterized in that the styrene based thermoplastic elastomer is chosen from SBS, SEBS, SEPS, SIBS or mixtures thereof.

7. Article according to any one of the claims 1-6 characterized in that the second polymer structure further comprises a thermoplastic material, a thermoset rubber, a thermoplastic elastomer or mixtures thereof.

8. Article according to any one of claims 1-7 characterized in that the first polymer structure comprises a thermoset rubber chosen from EPM or EPDM.

9. Article according to any one of the claims 1-8 characterized in that in case of more than one polymer structure to be adhered to the second polymer structure, the structures may comprise the same or different polymeric materials.

10. Article according to any one of the claims 1-9 characterized in that the polymer structures are each independently extruded, molded or calendering structures.

11. Article according to any one of the claims 1-10 characterized in that at least one EPDM extruded structure is adhered to a molded part comprising styrene- ethylene-butadiene-styrene, a propylene copolymer and a metal oxide.

12. Article according to any one of the claims 1-11 characterized in that the article is a laminate, a sheet, a roofing sheet, a film, a seal or a hose.

13. Article according to claim 12 characterized in that the seal is a weather strip for an automobile.

14. Polymer composition comprising a styrene based thermoplastic elastomer, a polyolefin and a metal oxide or metal hydroxide.

15. Polymer composition according to claim 14 characterized in that the metal oxide or metal hydroxide is chosen from Zn-, Al-, Ca-, Sn-or Mg (oxide or hydroxide).

16. Polymer composition according to any one of the claims 14-15 characterized in that the metal oxide or metal hydroxide is present in an amount of 2-68 wt% based on the total weight of the composition.

17. Polymer composition according to any one of claims 14-16 characterized in that the polyolefin is a propylene homo or copolymer.

18. Polymer composition according to any one of the claims 14-17 characterized in that the composition further comprises a thermoplastic material, a thermoplastic elastomer, a thermoset rubber or mixtures thereof.

19. Polymer composition according to any one of the claims 14-18 characterized in that the styrene based thermoplastic elastomer is chosen from SBS, SEBS, SEPS, SIBS or mixtures thereof.

20. Use of the polymer composition according to any one of the claims 14-19 as an adhesive composition.

21. Use of the polymer composition according to claims 20 in laminates, weather strips, sheets, roofing sheets, films, seals or hoses.

22. Process for the production of an article according to any one of claims 1-13, comprising injection molding a composition comprising a styrene based thermoplastic elastomer, a polyolefin and a metal oxide or metal hydroxide into a mold onto a first polymer structure comprising a thermoset rubber.