EP1497360A1 - Soft chemically foamed thermoplastic vulcanizate for sealing application by robotic extrusion - Google Patents

Abstract

The present invention relates to a foamable thermoplastic elastomer composition (TPE) comprising a thermoplastic rubber, having a Shore A hardness below about 85, a thermoplastic polyolefin resin with a melt flow rate below about 8.0 g/10min and a chemical blowing agent, which compositon is capable of being melt-extrudable by robotic extrusion. The invention further relates to an extruded article obtainable from said composition, a method of making said article by use of robotic extrusion and to an automotive screen having a sealing profile along or to the edge of the glass window screen and other sealing profiles to rigid substrates.

Description

Soft chemically foamed thermoplastic vulcanizate for sealing application by robotic extrusion

Technical Field of the Invention The present invention relates to thermoplastic elastomer compositions (TPE) comprising a thermoplastic rubber, a thermoplastic polyolefin resin and a chemical blowing agent, which composition can be extruded and foamed by robotic extrusion.

The invention further relates to foamed extruded articles obtainable from said composition, a method of making said article by robotic extrusion and to an automotive windscreen having a sealing profile along to the edge of the glass or any other sealing profiles to a more or less rigid article.

Background of the Invention Robotic extrusion facilitates the extrusion of a calibrated profile of a thermoplastic polymer onto articles wherein the articles are positioned in the processing region of an automatic handling unit (robot). The polymer melted in an extruder is fed, via a heated pressure hose, to a heated extruder head which is guided by the automatic handling unit and provided with an extrusion die. The polymer is extruded and deposited on the articles. The connection between the cylinder of the extruder and the extrusion nozzle/die is provided by an electrically heated high pressure hose. The high pressure hose must withstand pressures of at least about 250 bar at operating temperature. The hose comprises an electrical heating coil which provides for a regulated heating of the hose to a temperature of about 200°C. On the other hand, the high pressure hose must be sufficiently flexible for it to be able to follow the movements of the extrusion die without restriction, and for it to not interfere with the movements of the robot. The high pressure hose does inevitably have a certain torsional stiffness by which, in certain circumstances, it can interfere with the extrusion operation.

For example, during a circuit of the manipulation head around a glass pane, the extrusion die is rotated through 360°, and this torsional movement is transmitted to the hose. By this continual torsional loading, the hose is harmed, which results in accelerated wear of the hose and its fixations. Also, the corresponding reaction forces are transmitted by these torsional forces into the manipulating head. This can lead to inaccuracy in the extrusion operation.

United States Patent No. 5,336,349 to Cornils et al discloses a method and an apparatus for providing a surface of an article with a profiled gasket, bead or a profiled frame. According to this method a thermoplastic elastomer is supplied via an extruder and a heated pressure hose to a heated extrusion die. The die is guided by a robot, and the elastomer is extruded and laid by means of the extrusion die onto the surface. For these purposes, thermoplastic elastomers, especially thermoplastic polyolefin elastomers of isotactic polypropylene and ethylene-propylene-diene rubber (EPDM) may be used. The thermoplastic elastomers are not foamed.

United States Patent No. 5,554,325 to Koette et al discloses a process and device for the extrusion of a calibrated profile of a thermoplastic polymer onto an article. Thermoplastic elastomeric vulcanizates (TPVs) that have proven particularly suitable for the described process are, in particular, thermoplastic polyolefin elastomers of isotactic propylene and ethylene-propylene-diene rubber which are commercially available from Advanced Elastomer Systems, L. P., Akron, OH, USA, under the tradename SANTOPRENE^®. Foaming of the elastomers is not disclosed.

Published European patent application EP 0637604 discloses plastic moldings with foam-rubber like properties, made from foamed thermoplastic elastomers comprising a polypropylene/EPDM blended with dynamically crosslinked elastomer fractions and styrene-ethylene/butylene-styrene triblock copolymer/PP blend. United States Patent No. 5,393,796 to Halberstadt discloses a process and apparatus for extruding a soft, low density elastomeric thermoplastic foam from Santoprene^® (US Patents 4,130,535 and 4,311,628) having a Shore A hardness (ASTM D2240-02) of about 64 or less in the presence of a blowing agent. The extruded profiles can be used as weather-strip for sealing doors and windows. For the purpose of extruding the thermoplastic elastomer a single screw extruder having a very large length to diameter ratio of about 32:1 to 60:1 is provided. Robotic extrusion of a thermoplastic elastomer composition being capable of being extruded by robotic extrusion is not mentioned. United States Patent No. 5,051 ,478 to Puydak discloses dynamically vulcanized thermoplastic alloy compositions (DVAs) comprising a polyolefin resin, an elastomer, and an ethylene copolymer resin, having improved surface appearance and softness.

TPV formulations which can be foamed by chemical blowing have the disadvantage that their viscosity is high. High viscosities necessitate unreasonably high pressures during the robotic extrusion process and therefore reduce the commercial applicability of such processes. On the other hand, TPVs having a low viscosity, i.e., a Shore A hardness of less than about 50 suffer from reduced blowing properties, for instance low melt strength. The main reason for this is that despite a solid cell structure being formed, the foamed profile collapses directly after exiting the die.

Summary of the Invention

The invention has as an object the provision of TPVs having low viscosity and Shore A hardness and good flow properties so that they can be extruded and foamed by robotic extrusion while maintaining good chemical blowing properties such as melt-strength of the resulting foam.

It has been a second object of the present invention to provide a foamed, extruded and shaped article having a closed cell structure with smooth surface and a density of between about 0.3 and 0.8 g/cm³ and with good sealability over the temperature range of about -40 to +100°C. It has been a third object of the present invention to provide a method for making a shaped article, for instance, a seal for windscreens and quarter- lights of a vehicle or any other sealing profiles to a more or less rigid article.

In a first embodiment the present invention relates to a foamable thermoplastic elastomer composition comprising

(A) a thermoplastic rubber comprising i. a fully cured rubber; and ii.a thermoplastic polyolefin homopolymer or copolymer wherein said rubber (A) has a Shore A hardness from about 35 to about 85 (measured according to ASTM D2240-02 @ 5 seconds delay);

(B) a thermoplastic resin selected from the group consisting of ethylene vinyl acetate (EVA), terpolymers of C2 to C₁₂ monoolefins and blends thereof; said thermoplastic resin (B) has a melt flow rate from about 0.2 to about 10.0 (measured according to ASTM D1238-01 , 230° C/2.16 kg load); and

(C) a chemical blowing agent.

The extrudable and foamable composition of the invention overcomes the above-described deficiencies and is highly suitable for robotic extrusion, i.e., it possesses a sufficiently high melt strength while its viscosity is in a range which is appropriate for robotic extrusion. Applying the composition according to the present invention in melt extrusion processes, in particular in robotic extrusion processes, leads to foamed extrudates with essentially closed cells, a cell size in the range from about 0.01 to about 1 mm and a specific gravity of the foam in the range from about 0.4 to about 0.8 g/cm³. Detailed Description of the Invention

Thermoplastic rubber (A)

The thermoplastic rubber (elastomer) composition used according to the present invention as component (A) has a combination of both, thermoplastic and elastic properties (thermoplastic elastomers, TPE). It is generally obtained by blending a thermoplastic polyolefin with an elastomeric composition (rubber) in a way such that the elastomer is intimately and uniformly dispersed as a discrete particulate phase within a continuous phase of the thermoplastic. Early work with vulcanized compositions is found in U.S. Patent No. 3,037,954 to Gessler which discloses static vulcanization as well as the technique of dynamic vulcanization wherein a vulcanizable elastomer is dispersed into a resinous thermoplastic polymer and the elastomer is cured while continuously mixing and shearing the polymer blend. The resulting composition (thermoplastic elastomer vulcanizate "TPV") is a microgel dispersion of cured elastomer, such as butyl rubber, chlorinated butyl rubber, polybutadiene, polyisobutene etc. in an uncured matrix of thermoplastic polymer, such as polypropylene.

Accordingly the thermoplastic rubber component (A) may generally be prepared by mixing i. an uncured rubber, and ii. a thermoplastic polyolefin homopolymer or copolymer and; optionally iii.conventional additives and fillers; then melting the mixture under kneading until a homogeneous blend is obtained. The addition of curing agents (also referred to as curatives, crosslinking- or vulcanizing agents) to the blend during the mixing under conditions of heat and shear results in a composition of a fully cured (also referred to as fully vulcanized or fully crosslinked) rubber dispersed in a thermoplastic matrix. The term "rubber" as used herein means any natural or synthetic polymer which can be cured so as to exhibit elastomeric properties. For the purpose of this invention the term "elastomer" is used interchangeably with the term "rubber".

The term "fully cured" in conjunction with the dynamically cured rubber component of this invention denotes that the rubber component to be vulcanized has been cured to a state in which the physical properties of the rubber are developed to impart elastomeric properties to the rubber generally associated with the rubber in its conventional vulcanized state. The degree of cure of the vulcanized rubber can be described in terms of gel content or, conversely, extractable components. Alternatively, the degree of cure can be expressed in terms of cross-link density. Where the determination of extractables is an appropriate measure of the state of cure, the improved thermoplastic elastomeric compositions are produced by vulcanizing the curable rubber component of the blends to the extent that the composition contains, with increasing preference in the order given, no more than about 4, 3, 2, 1 weight percent of the cured rubber component extractable at room temperature by a solvent which dissolves the rubber which is intended to be vulcanized. In general, the less extractables the cured rubber component contains, the better the properties of the TPE are. It follows that compositions comprising essentially no extractable rubber from the cured rubber phase are highly preferable. In terms of the present invention the term "no extractable" means less than about 0.5 percent by weight, ideally 0 percent by weight extractables. Gel content, reported as percent gel is determined by a procedure which comprises determining the amount of insoluble polymer by soaking the specimen for about 48 hours in an organic solvent at room temperature and weighing the dried residue and making suitable corrections based upon knowledge of the composition. Thus, corrected initial and final weights are obtained by subtracting from the initial weight, the weight of soluble components, other than the rubber to be vulcanized, such as extender oils, plasticizers and components of the compositions soluble in organic solvent, as well as that rubber component of the TPV which it is not intended to cure. Any insoluble pigments, fillers, etc., are subtracted from both the initial and final weights. Measurement of Gel Content:

A sample of a thermoplastic elastomer composition of about 100 g is weighed and cut into fine fragments (size: 0.5 mm x 0.5 mm x 0.5 mm). In a closed vessel, the sample is immersed in 30 ml of cyclohexane at 23°C for 48 hours. Then, the sample is taken out, placed on a filter paper and dried at room temperature for not less than 72 hours until a constant weight is reached. From the weight of the dry residue, the weight of all the cyclohexane-insoluble components (e.g., fibrous filler, filler, pigment) other than the polymer component is subtracted. The obtained value is taken as "corrected final weight (Y)". On the other hand, from the sample weight, the weight of the cyclohexane- soluble components (e.g., softener) other than the polymer component and the weight of the cyclohexane-insoluble components (e.g., fibrous filler, filler, pigment) are subtracted. The obtained value is taken as "corrected initial weight (X)". The gel content (content of the cyclohexane-insoluble components) is calculated by the following equation.

Y

Gel - Content[wt. - %] = — 100

According to the present invention said thermoplastic rubber (A) has a Shore A hardness from about 35 to about 85, preferably from about 35 to about 60, most preferably about 35 to about 50 (as measured according to ASTM D2240- 02 @ 5 seconds delay).

In a preferred embodiment the thermoplastic rubber (A) has an LCR-viscosity (laboratory capillary rheometer) of about 20 to about 100 Pa- s, preferably about 55 to about 85 Pa- s, and in a specific embodiment about 68 Pa- s. For preparing the thermoplastic rubber composition used as the component (A) in the composition according to the present invention rubber (i) is mixed with the thermoplastic polyolefin homo- or copolymer (ii) at a temperature sufficient to soften the resin or, more commonly, at a temperature above its melting point where the resin is crystalline at room temperature. After the resin and rubber are intimately mixed, the curative is added. Heating and masticating with shearing at vulcanization temperatures are generally adequate to complete- vulcanization in about 0.5 to about 10 minutes. The curing time can be reduced by elevating the curing temperature. A suitable range of curing temperatures is from about the peak melting point of the resin (about 130°C for HDPE and about 165°C for PP) to about 250°C. More typically, the temperature range is from about 160°C to about 225°C. Preferably the vulcanization is carried out at a temperature ranging from about 170°C to about 200°C.

Dynamic vulcanization is effected by mixing the thermoplastic and elastomer components at elevated temperature on conventional mixing equipment such as roll mills, Banbury mixers, Brabender mixers, continuous mixers, mixing extruders and the like. The compositions may be processed and reprocessed by conventional plastic processing techniques such as extrusion, injection- molding, blow-molding, compression-molding and thermo-forming.

In the foamable thermoplastic elastomer composition of this invention the thermoplastic rubber (A) is used in an amount of about 80 to about 98 parts by weight, preferably about 85 to about 96, most preferred about 91 to about 95 parts by weight, based upon 100 parts by weight of the total of the thermoplastic rubber (A), the olefin plastic (B) and the blowing agent (C).

In the following the individual constituents of the fully cured thermoplastic rubber component (A) are described in more detail.

Rubber (i)

Illustrative, non-limiting examples of rubbers (i) suitable for use in the thermoplastic rubber (A) include rubbers selected from the group consisting of ethylene/alpha-olefin/non-conjugated diene copolymer rubbers, such as ethylene-propylene/non-conjugated diene rubber (EPDM), ethylene/alpha-olefin copolymer rubber wherein the alpha-olefin is of the formula CH₂=CHR and wherein R is a straight or branched alkyl group having 1 to 12 carbon atoms such as propylene, 1-butene, isobutylene, 1-pentene, 1-hexene, 1-heptene, 1- octene, 3-metyl-1-pentene, 4-methyl-1-pentene, 5-methyl-1-hexene, and the like. A preferred ethylene/alpha-olefin rubber is ethylene/propylene copolymer rubber (EPM). Further examples of rubbers are butyl rubber, halogenated butyl rubber, copolymers of C to C isomonoolefins and para-alkylstyrene or their halogenated derivatives, natural or synthetic rubbers, polyisoprene rubber, polybutadiene rubber, styrene/butadiene copolymer rubbers and blends thereof.

The curable or vulcanizable rubbers which can be used in the practice of this invention include both synthetic and natural rubbers; at least one of the rubbers utilized must be vulcanizable.

While polyisobutylene (PIB) is not a true rubber because it cannot be vulcanized, it can be utilized in the practice of this invention in conjunction with a vulcanizable rubber provided that the PIB has a viscosity average molecular weight of about 40,000 to about one million.

The term "nitrile rubber" means an acrylonitrile copolymer rubber. Suitable nitrile rubbers comprise rubbery polymers of 1 ,3-butadiene or isoprene and acrylonitrile. Preferred nitrile rubbers comprise polymers of 1 ,3-butadiene and about 20 to 50 weight percent acrylonitrile. Any nitrile rubber which is a "solid" rubber having an average molecular weight of at least 50,000, and preferably between about 100,000 to 1,000,000 can be used. Commercially available nitrile rubbers suitable for the practice of the invention are described in Rubber World Blue Book, 1980 Edition, Materials and Compounding Ingredients for Rubber, pages 386-406.

Suitable halogenated copolymers of a C₄ to C isomonoolefin and a para- alkylstyrene include copolymers comprising para-alkylstyrene moieties which may be represented by the formula:

wherein R² and R³ are independently selected from the group consisting of hydrogen, alkyl groups having about 1 to about 5 carbon atoms, primary and secondary haloalkyl groups having about 1 to about 5 carbon atoms, and X is selected from the group consisting of bromine, chlorine and mixtures thereof, such as those disclosed in published European Patent application 0355021. Preferably, the alkylstyrene copolymer is a halogenated copolymer of isobutylene and para-methylstyrene, more preferably, the brominated copolymer of isobutylene and para-methylstyrene.

Butyl rubber is a copolymer of an isoolefin and a conjugated multiolefin. The useful rubber copolymers comprise a major portion of isoolefin and a minor amount, preferably not more than about 30 weight percent, of a conjugated multiolefin. The preferred rubber copolymers comprise about 85 to about 99.5 weight percent (preferably about 95 to about 99.5 weight percent) of a C₄ to C₇ isoolefin, such as isobutylene, and about 15 to 0.5 weight percent (preferably about 5 to about 0.5 wt %) of a multiolefin of about 4 to about 14 carbon atoms. These copolymers are referred to in the literature as "butyl rubber."

The term "butyl rubber" as used herein includes the aforementioned copolymers of an isoolefin having about 4 to about 7 carbon atoms and about 0.5 to about 20 weight percent of a conjugated multiolefin of about 4 to about 14 carbon atoms. Preferably these copolymers contain about 0.5 to about 5% conjugated multiolefin. The preferred isoolefin is isobutylene. Suitable conjugated multiolefins include isoprene, butadiene, dimethyl butadiene, piperylene, etc. Commercial butyl rubber is a copolymer of isobutylene and minor amounts of isoprene.

Butyl rubber as above described may be halogenated with from about 0.1 to about 10, preferably, about 0.5 to about 3.0 weight percent chlorine or bromine to make a suitable halobutyl rubber. The chlorinated form of butyl rubber is commonly known as "chlorobutyl rubber" and the brominated form as "bromobutyl rubber."

Another suitable rubber according to the present invention is based on polychlorinated butadienes such as polychloroprene rubber. These rubbers are comercially available under the trade names Neoprene^® (DuPont Dow) and Bayprene^® (Mobay).

In a preferred embodiment of the invention the rubber (i) is an ethylene/alpha- olefin copolymer rubber (EPM) or ethylene/alpha-olefin/non-conjugated diene copolymer rubber (EPDM), the latter being most preferred. The non-conjugated diene monomer can be a straight chain, branched chain or cyclic hydrocarbon diene having from about 6 to about 15 carbon atoms. Examples of suitable non-conjugated dienes are straight chain acyclic dienes such as 1 ,4-hexadiene and 1 ,6-octadiene: branched chain acyclic dienes such as 5-methyl-1 ,4-hexadiene; 3,7-dimethyl-1 ,6-octadiene; 3,7-dimethyl-1 ,7- octadiene and mixed isomers of dihydromyricene and dihydroocinene; single ring alicyclic dienes such as 1 ,3-cyclopentadiene; 1 ,4-cyclohexadiene; 1,5- cyclooctadiene and 1 ,5-cyclododecadiene: and multi-ring alicyclic fused and bridged ring dienes such as tetrahydroindene, methyl tetrahydroindene, dicyclopentadiene; bicyclo-(2,2,1)-hepta-2.5-diene; alkenyl, alkylidene, cycloalkenyl and cycloalkylidene norbornenes such as 5-methylene-2- norbomene (MNB); 5-propenyl-2-norbornene, 5-isopropylidene-2-norbornene. 5-(4-cyclopentenyl)-2-norbomene, 5-cyclohexylidene-2-norbornene, 5-vinyl-2- norbornene and norbornadiene.

Of the dienes typically used to prepare EPDMs, the particularly preferred dienes are 1 ,4-hexadiene (HD), 5-ethylidene-2-norbomene (ENB), 5-vinylidene-

2-norbomene (VNB), 5-methylene-2-norbomene (MNB), and dicyclopentadiene --,,-_---„ ,_

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(DCPD). The especially preferred dienes are 5-ethylidene-2-norbomene (ENB) and 1 ,4-hexadiene (HD).

The ethylene/alpha-olefin/non-conjugated diene rubber contains from about 40 to about 85 weight percent of ethylene, preferably from about 45 to about 80 weight percent, and more preferably in the range of from about 50 to about 75 weight percent, based on the ethylene/propylene/non-conjugated diene rubber. The ethylene/propylene/non-conjugated diene rubber contains from about 0.25 to about 5 weight percent of diene, preferably from about 0.25 to about 2 weight percent and more preferably in the range of from about 0.5 to about 1.2 weight percent. The balance of the ethylene, alpha-olefin, non-conjugated diene elastomeric polymer to about 100 percent will generally be made up of an alpha-olefin which is selected from the group consisting of propylene, 1-butene, 1-hexene, 4-methyl-1 -pentene, 1 -octene, 1-decene and combinations thereof, and the like. The ethylene/propylene/non-conjugated diene rubber which is preferred according to this invention contains propylene as the alpha-olefin and 5-vinyl-2-norbomene as the diene comonomer.

In the thermoplastic rubber component (A) the amount of rubber (i) generally ranges from about 95 to about 10 weight percent, based on the weight of the rubber (i) and thermoplastic resin (ii). Preferably, the rubber content will be in the range of from about 80 to about 20 weight percent of total polymer.

Thermoplastic polyolefin homopolymer or copolymer (ii)

The term "thermoplastic polyolefin" as used herein in conjunction with the description of the thermoplastic elastomer component (A) denotes any polyolefin resin which exhibits thermoplastic properties.

A wide range of thermoplastic resins and/or their mixtures have been used in the preparation of thermoplastic elastomers, including polypropylene, polypropylene copolymers, HDPE, LDPE, VLDPE, LLDPE, polyethylene copolymers, cyclic olefin homopolymers or copolymers as well as olefinic block copolymers, polystyrene, polyphenylene sulfide, polyphenylene oxide and ethylene propylene copolymer (EP) thermoplastics. --,,-_---„ ,_

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Thermoplastic resins useful in the compositions produced by the invention include crystalline and semi-crystalline polyolefin homopolymers and copolymers. They are desirably prepared from mono-olefin monomers having about 2 to about 20, preferably about 2 to about 12, more preferably about 2 to about 7 carbon atoms, such as ethylene, propylene, 1-butene, isobutylene, 1-pentene, 1-hexene, 1-heptene, 1 -octene, 3-methyl-1-pentene, 4-methyl-1- pentene, 5-methyl-1 -hexene, mixtures thereof and copolymers thereof with (meth)acrylates, such as methyl (meth)acrylates.

As used in the specification and claims the term polypropylene" includes homopolymers of propylene as well as reactor copolymers of polypropylene (PPRC) which can contain about 1 to about 20 weight percent of ethylene or an alpha-olefin comonomer of about 4 to about 20 carbon atoms, and mixtures thereof. The polypropylene can be atactic, isotactic or syndiotactic, made with Ziegler-Natta or metallocene catalysts. The PPRC can be either a random or block copolymer. The density of the PP or PPRC can be from about 0.88 to about 0.92 g/cm³; generally, from about 0.89 to about 0.91 g/cm³. Commercially available polyolefins may be used in the practice of the invention. Blends of thermoplastic resins may also be used.

The preferred polyolefin resins are high density polyethylene (HDPE) and polypropylene. While other polyolefin homopolymers and copolymers of ethylene can be utilized in the practice of this invention, the resulting TPE compositions are deficient in high temperature characteristics. Such other polyolefins include low density polyethylene (LDPE), very low density polyethylene (VLPE), linear low density polyethylene (LLDPE) and polybutylene (PB). However, these other polyolefin resins can be incorporated into the thermoplastic elastomer composition (a) of this invention along with the polypropylene (PP) or high density polyethylene (HDPE).

High density polyethylene (HDPE), useful as the polyolefin resin of this invention, has a density of about 0.941 to about 0.965 g/cm³. High density polyethylene is an established product of commerce and its manufacture and general properties are well known to the art. Typically, HDPE has a relatively broad molecular weight distribution, characterized by the ratio of weight average molecular weight to number average molecular weight of from about 20 to about 40.

The term "low density polyethylene" or "LDPE" as used herein means both low and medium density polyethylene having densities of about 0.910 to about 0.940 g/cm³. The terms include linear polyethylene as well as copolymers of ethylene which are thermoplastic resins.

The term "very low density polyethylene" or "VLDPE" is used herein to mean polyethylene having a density below about 0.910 g/cm³ and includes linear polyethylene as well as copolymers of ethylene which are thermoplastic resins. Linear low density polyethylene (LLDPE) is a class of low density polyethylene characterized by little, if any, long chain branching derived from C₃ to C₁₂ alpha- olefins selected from the group consisting of propylene, 1-butene, 1-hexene, 1- octene, 4-methyl-1-pentene; preferably 1-butene or 1-hexene. The processes for producing LLDPE are well known in the art and commercial grades of this polyolefin resin are available. Generally, it is produced in gas-phase fluidized bed reactors or liquid-phase solution process reactors; the former process can be carried out at pressures of about 0.69 to about 2.07 MPa (about 100 to about 300 psi) and temperatures as low as about 100 °C.

The amount of thermoplastic polyolefin (ii) found to provide useful compositions (A) is generally from about 5 to about 90 weight percent, based on the weight of the rubber (i) and thermoplastic polyolefin resin (ii). Preferably, the thermoplastic resin content will range from about 20 to about 80 percent by weight of the total polymer.

Conventional Fillers and Additives

The solid particulate component which is added to the thermoplastic elastomeric composition of the present invention after it has been subjected to dynamic vulcanization under conditions to fully cure the elastomer comprised in the composition sufficiently to prevent penetration of at least a major portion of the solid particulate component into the elastomer may be a filler/fillers, certain additive(s) or mixtures thereof. Once vulcanization is achieved, the fillers and/or additives are added and mixed into the blend. This ensures that in the fully vulcanized DVA the fillers and/or additives will be retained in the thermoplastic phase because they will not be able to penetrate into the cross-linked elastomer phase. However, depending upon the degree to which it is desirable to have some of the filler and/or additive incorporated into the elastomer phase, the fillers and/or additives may be added at the desired level of partial cure of the elastomer phase. As an alternative to the above process, the DVA product may be produced without fillers or additives. The fillers and/or additives may then be added in a later second compounding operation.

Generally adding fillers and/or additives is conventional in the art of rubber compounding. Suitable additives are selected from the group consisting of pigments, antistatic agents, antioxidants, ultraviolet light stabilizers, antiblocking agents, lubricants, processing oils, waxes, coupling agents for fillers and mixtures thereof. The term "filler" as used herein refers to non-reinforcing fillers, reinforcing fillers, organic fillers and inorganic fillers. The fillers may be organic fillers and inorganic fillers (e.g., mineral fillers). Preferably, the filler is an inorganic filler. Suitable fillers include talc, silica, clays, solid flame retardants, calcium carbonate, titanium dioxide, barium sulfate, carbon black, other mineral fillers, and mixtures thereof. The carbon black can be derived from any source and be any type of carbon black such as channel blacks, furnace blacks, thermal blacks, acetylene black, lamp black and the like. Any effective amount of filler may be added. Typically, the filler may be added in an amount of up to about 60 weight percent, preferably ranging from about 2 to about 50 weight percent based on the total thermoplastic dynamically vulcanized composition (A). For specific fillers, these proportions may vary. Carbon black, for instance, is preferably added in an amount ranging from about 1 to about 40 weight percent, more preferably from about 2 to about 20 weight percent, based on the composition (A). It will be understood that for a particular application, the effective amount of filler or additive may well be outside of these ranges. Since the invention concentrates the filler in the thermoplastic phase where it is most needed in the case of reinforcing fillers, a reduction in the quantity of filler to be added may be expected for maintaining the same strength desired.

The suitable additives for the practice of the invention may be added in an amount ranging from about 0.05 to about 5 weight percent, preferably from about 0.05 to about 3 weight percent, based on the total composition. When the suitable additive is an ultraviolet light stabilizer, the ultraviolet light stabilizer may be present in an amount ranging from about 0.05 to about 1.0 weight percent, based on the total elastomeric composition (A).

The term "ultra-violet light stabilizer" (UN. stabilizer, typically a particulate solid at standard temperature and pressure having a molecular weight of at least about 1,000, preferably, at least about 5,000) is used herein to denote compounds which provide stabilization or protection from the degrading effects of ultra-violet light on TPV compositions. The UN. stabilizers do not adversely affect the TPV compositions of the present invention. It has been found that addition of UN. stabilizers to TPV compositions can significantly decrease the crosslinking performance of curatives utilized for halobutyl elastomer materials. Such decrease does not occur to the same extent when the curative system is a maleimide curative system. Suitable UN. stabilizers include hindered amine light stabilizers (HALS) which belong to a class of compounds referred to as "hindered amines." These hindered amines have been found to be effective in stabilizing polymers. See, for example, U.S. Patent No. 4,064,102 the teachings of which are hereby incorporated by reference. Preferred UV stabilizers are the 2,2,4,4-tetramethylpiperidine derivatives such as N,N-bis(2,2,6,6-tetramethyl-4- piperidinyl)-1 ,6-hexanediamine, bis(2,2,6,6-tetra-methyl-4-piperidinyl) decane- dioate, and the reaction product of dimethyl succinate plus 4-hydroxy-2,2,6,6- tetramethyl-1-piperidine-ethanol sold by Ciba-Geigy Corporation under the tradenames Chimassorb 944LD, Tinuvin 770, and Tinuvin 622LD, respectively. The effective amount of UN. stabilizer added will depend upon the particular stabilizer used and the degree of protection desired. The HALS is employed at about 0.01 to about 0.5 wt % of the composition (A), preferably from about 0.02 to about 0.25 wt %, and most preferably from about 0.03 to about 0.15 wt %, based on composition (A). When UN. stabilizers are used, it is preferred that the blends be dynamically vulcanized in the presence of a maleimide cure system although other cure systems discussed below are also useful. The maleimide compound preferably used in the invention is a bismaleimide compound. Among the maleimide compounds, a bismaleimide compound is especially superior in effectiveness and m-phenylene bismaleimide (4,4^' m-phenylene bismaleimide) is preferred. Examples of the bismaleimide are 4,4^'-vinylenediphenyl bismaleimide, p- phenylene bismaleimide, 4,4'-sulfonyldiphenyl bismaleimide, 2,2^'-dithiodiphenyl bismaleimide, 4,4'-ethylene-bis-oxophenyl bismaleimide, 3,3^'-dichloro-4,4^'- biphenyl bismaleimide, o-phenylene bismaleimide, m-phenylene bismaleimide (HVA-2), hexamethylene bismaleimide and 3,6-purine bismaleimides.

Rubber process oils have particular ASTM designations depending on whether they fall into the class of paraffinic, naphthenic or aromatic process oils. They are derived from petroleum fractions. The type of process oil utilized will be that customarily used in conjunction with the rubber component. The ordinarily skilled rubber chemist will recognize which type of oil which should be utilized with a particular rubber. The quantity of rubber process oil utilized is based on the total rubber content, both cured and uncured, and can be defined as the ratio, by weight, of process oil to the total rubber in the TPE. This ratio may range from about above 0 to about 1.5/1 , preferably about 0.2/1 to about 1.0/1 ; more preferably about 0.3/1 to about 0.8/1. Larger amounts of process oil can be used, the deficit being reduced physical strength of the composition. Oils other than petroleum based oils, such as oils derived from coal tar and pine tar, can also be utilized. In addition to the rubber process oils, organic esters and other synthetic plasticizers may be used.

Antioxidants can be added to the rubber composition (A). The particular antioxidant utilized will depend on the rubbers utilized as can synthetic oils such as isoparaffinic oil and more than one type may be required. Their proper selection is well within the ordinary skill of the rubber processing chemist. Antioxidants will generally fall into the class of chemical protectors or physical protectants. Physical protectants are used where there is to be little movement in the part to be manufactured from the composition. These are generally waxy materials which impart a "bloom" to the surface of the rubber part and form a protective coating to shield the part from oxygen, ozone, etc. The chemical protectors generally fall into three chemical groups; secondary amines, phenolics and phosphites. Examples of these types of antioxidants useful in the practice of this invention are hindered phenols, amino phenols, hydroquinones, alkyldiamines, amine condensation products, etc.

Examples for the antioxidants include phenol-based antioxidants, amine-based antioxidants, sulfur-based oxidants, and the like. Examples of the phenol-based antioxidant include 2,6-di-tert-butylphenol (hereinafter "tert-butyl" is referred to as "t-butyl"), 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4-methylphenol, 2,6-di-t-butyl- 4-ethylphenol, 2,4-dimethyl-6-t-butylphenol, 4,4'-methylenebis(2,6-di-t-butyl- phenol), 4,4'-bis(2,6-di-t-butylphenol), 4,4'-bis(2-methyl-6-t-butylphenol), 2,2'-methylenebis(4-methyl-6-t-butylphenol), 2,2'-methylenebis(4-ethyl-6-t-butyl- phenol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 4,4'-isopropylidene bis- (2,6-di-t-butylphenol), 2,2'-methylenebis(4-methyl-6-cyclohexylphenol), 2,2'- methylene-bis(4-methyl-6-nonylphenol), 2,2'-isobutylidenebis(4,6-dimethyl- phenol), 2,6-bis(2'-hydroxy-3^,-t-butyl-5^,-methylbenzyl)-4-methylphenol, 3-t-butyl- 4-hydroxy anisole, 2-t-butyl-4-hydroxy anisole, 3-(4-hydroxy-3,5-di-t-butyl- phenyl) stearyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) oleyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) dodecyl propionate, 3-(4-hydroxy-3,5-di-t- butylphenyl) decyl propionate, 3-(4-hydroxy-3,5-di-t-butylphenyl) octyl propionate, tetrakis{3-(4-hydroxy-3,5-di-t-butylphenyl) propionyloxymethyl} methane, 3-(4-hydroxy-3,5-di-t-butylphenyl) glycerin propionate monoester, an ester of 3- (4-hydroxy-3,5-di-t-butylphenyl) propionate and glycerin monooleyl ether, 3-(4- hydroxy-3,5-di-t-butylphenyl) butylene propionate glycolate ester, 3-(4-hydroxy- 3,5-di-t-butylphenyl) propionate thiodiglycolate ester, 4,4'-thiobis(3-methyl-6-t- butylphenol), 4,4'-thiobis(2-methyl-6-t-butylphenol), 2,2'-thiobis(4-methyl-6-t- butylphenol), 2,6-di-t-butyl-.alpha.-dimethylamino-p-cresol, 2,6-di-t-butyl-4- (N.N'-dimethylaminomethyl-phenol), bis(3,5-di-t-butyl-4-hydroxy benzyl) sulfide, tris{(3,5-di-t-butyl-4-hydroxyphenyl)propionyl-oxyethyl} isocyanulate, tris(3,5-di-t- butyl-4-hydroxyphenyl)isocyanulate, 1 ,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl)- isocyanulate, bis{2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl} sulfide, 1 ,3,5-tris(4-t-butyl-3-hydroxy-2,6-dimethylbenzyl)isocyanulate, tetraphthaloyl- di(2,6-dimethyl-4-t-butyl-3-hydroxybenzyl sulfide), 6-(4-hydroxy-3,5-di-t-butyl- anilino)-2,4-bis(octylthio)-1 ,3,5-triazine, 2,2-thio-{diethyl-bis-3-(3,5-di-t-butyl-4- hydroxyphenyl)}-propionate, N,N'-hexamethylenebis(3,5-di-t-butyl-4-hydroxy- hydrocinnamido), 3,5-di-t-butyl-4-hydroxy-benzyl-phosphate diester, bis(3- methyl-4-hydroxy-5-t-butylbenzyl)sulfide, 3,9-bis[1 ,1 -dimethyl-2-{.beta.-(3-t- butyl-4-hydroxy-5-methylphenyl)-propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]- undecane, 1 ,1 ,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane, 1 ,3,5-trimethyl- 2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, bis{3,3'-bis-(4^,-hydroxy-3,3'-t- butylphenyl)-butyric acidjglycolate ester, and the like.

Examples of the amine-based antioxidant include naphthylamine-based antioxidants such as 1-naphthylamine, phenyl-1-naphthylamine, p-octylphenyl- 1-naphthylamine, p-nonylphenyl-1-naphthylamine, p-dodecylphenyl-1-naphthyl- amine, phenyl-2-naphthylamine; phenylenediamine-based antioxidants such as N.N'-diisopropyl-p-phenylenediamine, N.N'-diisobutyl-p-phenylenediamine,

N,N'-diphenyl-p-phenylenediamine, N.N'-di-p-naphtyl-p-phenylenediamine, N- phenyl-N'-isopropyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylene- diamine, N-1 ,3-dimethylbutyl-N'-phenyl-p-phenylenediamine, dioctyl-p-phenyl- enediamine, phenylhexyl-p-phenylenediamine, phenyloctyl-p-phenylene- diamine; diphenylamine-based antioxidants such as dipyridylamine, diphenylamine, p,p'-di-n-butylphenylamine, p.p'-di-t-butyldiphenylamine, p,p'-di- t-pentyldiphenylamine, p,p'-dinonyldiphenylamine, p.p'-didecyldiphenylamine, p.p'-didodecyldiphenylamine, p.p'-distyryldiphenylamine, p,p'-dimethoxydi- phenylamine, 4,4'-bis(4-alpha,alpha-dimethylbenzoyl)diphenylamine, p-iso- propoxydiphenylamine, dipyridylamine; and phenothiazine-based antioxidants such as phenothiazine, N-methylphenothiazine, N-ethylphenothiazine, 3,7- dioctylphenothiazine, phenothiazine carboxylate ester, and phenoselenazine. Examples of the sulfur-based antioxidant include dioctylthiodipropionate, didecylthiodipropionate, dilaurylthiodipropionate, dimyristylthiodipropionate, distearylthiodipropionate, laurylstearylthiodipropionate, dimyristylthio- dipropionate, distearyl-.beta.,.beta.-thiodibutylate, (3-octylthiopropionic acid) pe- ntaerythritol tetraester, (3-decylthiopropionic acid) pentaerythritol tetraester, (3-laurylthiopropionic acid) pentaerythritol tetraester, (3-stearylthiopropionic acid) pentaerythritol tetraester, (3-oleylthiopropionic acid )pentaerythritol tetraester, (3-laurylthiopropionic acid)-4,4'-thiodi(3-methyl-5-t-butyl-4-phenol)- ester, 2-mercaptobenzimidazole, 2-mercaptomethylbenzimidazol, 2-benz- imidazoldisulfide, dilaurylsulfide, amylthioglycolate, and the like.

The physical antioxidants include mixed petroleum waxes and micro-crystalline waxes. All or a portion of the fillers and/or additives can be added before the dynamic vulcanization step, after partial but before the dynamic vulcanization step or after the dynamic vulcanization step.

In composition (A) the rubber component will be fully vulcanized/crosslinked. Those of ordinary skill in the art will appreciate the appropriate quantities, types of cure systems and vulcanization conditions required to carry out the full vulcanization of the rubber. The rubber can be vulcanized using varying amounts of curative, varying temperatures and varying time of cure in order to obtain the optimum full crosslinking desired. Any known cure system can be used, so long as it is suitable under the vulcanization conditions for the rubber being used and is compatible with the thermoplastic polyolefin resin component of the TPV. These curatives include sulfur, sulfur donors, metal oxides, resin systems, high energy radiation and the like, both with and without accelerators and co-agents. In a further prefered alternative of the present invention crosslinking can also be effected by hydrosilylation crosslinking as disclosed in European published application 0776937. Organic peroxides with an adequate well-known co-agent can be used as cure system except where the butyl rubber is a non-halogenated butyl rubber. The role of the co-agent in peroxide cure systems is to enhance the cure-state and inhibiting chain-fragmentation or scission effect. Specific examples of useful organic peroxides are selected from octanoyl peroxide, lauroyl peroxide, benzoyl peroxide, tert.-butyl peroctoate, p-chlorobenzoyl peroxide, 2,4- dicholorbenzoyl peroxide, cyclohexanone peroxide, tert.-butyl peroxybenzoate, methyl ethyl ketone peroxide, dicumyl peroxide, di-tert.-butyl peroxide, 2,5- dimethyl-2,5-di(benzoylperoxy)hexane 2,5-dimethyl-2,5-di(tert.-butylperoxy)- hexane, di-tert.-butyl diperoxyphthalate, tert.-butylcumyl peroxide, diisopropyl- benzene hydroperoxide, 1 ,3-bis(tert.-butylperoxyisopropyl)benzene tert.-butyl peroxy-pivalate, 3,5,5-trimethylhexanoyl peroxide, 1 ,1-bis(tert.-butyl-peroxy)- 3,5,5-trimethylcyclohexane, 1 ,1-bis(tert.-butyl-peroxy)cyclohexane, etc.; azo compounds such as azobisisobutyronitrile, and the like.

The peroxide-based cure systems may be used with or without co-agents such as ethylene dimethacrylate, polyethylene glycol dimethacrylate, trimethylol propane trimethacrylate, divinyl benzene, diallyl itaconate, triallyl cyanurate, diallyl phthalate, allyl methacrylate, cyclohexyl methacrylate, m-phenylene bis maleimide (HVA-2), and the like.

Phenolic resin curatives are preferred for the preparation of the thermoplastic elastomer vulcanizate of the invention, and such cure systems are well known in the art and literature of vulcanization of rubbers. Their use in vulcanized compositions is more fully described in U.S. Patent No. 4,311 ,628, the disclosure of which is fully incorporated herein by this reference.

A basic ingredient of such system is a phenolic curing resin made by condensation of halogen substituted phenol, C₁-C₁₀ alkyl substituted phenol or unsubstituted phenol with an aldehyde, preferably, formaldehyde, in an alkaline medium or by condensation of bifunctional phenoldialcohols. Dimethylol phenols substituted in the para-position with C₅-C₁₀ alkyl groups are preferred. Halogenated alkyl substituted phenol curing resins prepared by halogenation of alkyl substituted phenol curing resin are also especially suitable. Phenolic curative systems comprising methylol phenolic resins, halogen donor and metal compound are especially recommended, details of which are described in Giller, U.S. Patent No. 3,287,440 and Gerstin et al, U.S. Patent No. 3,709,840. Non-halogenated phenol curing resins are used in conjunction with halogen donors, preferably, along with a hydrogen halide scavenger. Ordinarily, halogenated, preferably brominated, phenolic resins containing about 2 to about 10 weight percent bromine, do not require halogen donor but are used in conjunction with a hydrogen halide scavenger such as metal oxides such as iron oxide, titanium oxide, magnesium oxide, magnesium silicate, silicon dioxide and preferably zinc oxide, the presence of which promotes the crosslinking function of the phenolic resin, however, with rubbers which do not readily cure with phenolic resins, the conjoint use of a halogen donor and zinc oxide is recommended. The preparation of halogenated phenol resins and their use in a curative system with zinc oxide are described in U.S. Patent Nos. 2,972,600 and 3,093,613, the disclosure of which along with the disclosure of the aforesaid Giller and Gerstin patents are incorporated herein by reference. Examples of suitable halogen donors are stannous chloride, ferric chloride, or halogen donating polymers such as chlorinated paraffin, chlorinated polyethylene, chlorosulfonated polyethylene, and polychlorobutadiene (neoprene rubber). The term "activator" as used herein means any material which materially increases the cross-linking efficiency of the phenolic curing resin and includes metal oxides and halogen donors either used alone or conjointly. For further details of phenolic curative systems see "Vulcanization and Vulcanizing Agents," W. Hoffman, Palmerton Publishing Company. Suitable phenolic curing resins and brominated phenolic curing resins are commercially available, for example, such resins may be purchased under the trade names SP-1045, CRJ-352, SP-1055 and SP-1056 from Schenectady Chemicals, Inc. Similar functionally equivalent phenolic curing resins may be obtained from other suppliers. As explained above, sufficient quantities of curatives are used to achieve essentially complete cure of the rubber.

For halogenated butyl rubbers, a preferred cure system is one which is based on ZnO and/or MgO. In this system, the MgO does not act as an activator but as an acid acceptor to stabilize the rubber from dehydrohalogenation. Another preferred cure system for halogenated butyl rubbers comprises ZnO and a maleimide product. Among the maleimide product, a bismaleimide is especially superior in effectiveness and m-phenylene bismaleimide (4,4'-m- phenylene bismaleimide) (HVA-2) preferred. Other examples of the bismaleimide are 4,4'-vinylenediphenyl bismaleimide, p-phenylene bismaleimide, 4,4'-sulfonyldiphenyl bismaleimide, 2,2'-dithiodiphenyl bismaleimide, 4,4'- ethylene-bis-oxophenyl bismaleimide, 3,3'-dichloro-4,4'-biphenyl bismaleimide, o-phenylene bismaleimide, hexamethylene bismaleimide and 3,6-durine bis- maleimides. Usually about 1 to about 15 weight parts, preferably from about 2 to about 10 weight parts of the curative or curative system are used per 10O weight parts of the rubber to be cured.

Thermoplastic resin (B)

According to the present invention suitable thermoplastic resins (B) have a melt flow rate (MFR) of from about 0.2 to about 10.0, preferably from about 0.5 to about 4.0, most preferably from about 1.0 to about 3.5 (as measured according to ASTM D1238-01 at 230°C/2.16 kg load). Preferred thermoplastic resins are selected from the group consisting of

- random or block copolymers of C₂ to C12, preferably C₂ to C-ι₀, most preferably C₂ to C-β- mono-olefins and vinyl acetate,

- terpolymers of C₂ to C₁₂ mono-olefins having a random distribution in structure or a multi-sequence (multi-block) structure, and - blends of said copolymers.

Said vinyl acetate containing copolymers comprise from about 10 to about 40, preferably from about 15 to about 35, most preferably from about 20 to about 30 weight percent of vinyl acetate, based on the total weight of the copolymer. Preferred mono-olefins are selected from the group consisting of ethylene, propylene, 1-butene, 1-hexene, 1 -octene and 4-methyl-1-pentene. Ethylene is the preferred mono-olefin. Preferably, ethylene vinyl acetate (EVA) is used as one alternative thermoplastic resin (B). Typically, the ethylene vinyl acetate comprises from about 10 to about 40, preferably from about 15 to about 35, most preferably from about 20 to about 30 weight percent vinyl acetate, based upon the total weight of the ethylene vinyl acetate. An exemplary EVA comprising about 28 weight percent of vinyl acetate is available from DuPont under the trade designation Elvax^® 265.

Preferred thermoplastic terpolymers are based on ethylene, propylene and an alpha-olefin monomer different from ethylene and propylene. Typically, said terpolymers consist of about .5 to about 19.5 % by weight, more preferably from about 2.0 to about 15.0 % by weight of ethylene monomer, about 80.0 to about 99.0 % by weight, preferably from about 96.0 to about 80.0 % by weight of propylene monomer and about 19.5 to about 0.5 % by weight, preferably from about 2.0 to about 15.0 % by weight of the alpha-olefin monomer containing at least 4 carbon atoms, based on the weight of the thermoplastic terpolymer. The alpha-olefin comonomer used in the preparation of the terpolymer is a mono-olefin and preferably contains about 4 to about 12 carbon atoms, more preferably from about 4 to about 8 carbon atoms. As the alpha-olefin 1-butene, 1-pentene, 1-hexene, 1 -octene and 4-methyl-1-pentene are preferred. Most preferably 1-butene, 1-hexene and 1 -octene are used as the alpha-olefin. Blends of thermoplastic terpolymers can be used as well.

An example on a preferred terpolymer is ethylene-propylene-butene-1 random terpolymer is commercially available under the trade designation Adflex^® X 100 G from Basell.

The preparation of said thermoplastic terpolymers mentioned above is conventional in the art and known to the skilled person. Reference is made to the Ziegler/Natta catalysis-type or metallocene-catalysis -type polymerization.

The thermoplastic resin (B) is used in an amount of about 1 to about 10 parts by weight, preferably about 3 to about 7, most prefered about 4 to about 6 parts by weight, based upon 100 parts by weight of the total of the thermoplastic elastomer composition (A) and the olefin plastic (B) and the chemical blowing agent (C).

Chemical blowing agent (C)

The term "blowing agent" (or in the literature sometimes called "foaming agent") is typically used to describe any substance which alone or in combination with other substances is capable of producing a cellular structure in a polymer mass.

In conjunction with the present invention chemical blowing agents are preferred.

Chemical blowing agents commonly referred to as blowing agents are generally solids that liberate gas(es) by means of a chemical reaction or decomposition when heated. They are necessarily selected for specific applications or processes based on their decomposition temperatures. In this regard, it is important to match the decomposition temperature with the processing temperature of the polymer to be foamed. If the polymer processes at temperatures below that of the chemical blowing agent, little or no foaming will occur. If the process temperature is significantly above the blowing agent's decomposition temperature, poor (overblown, ruptured) cell structure and surface skin quality is likely to result. The blowing agents may be either inorganic or organic. The most common inorganic blowing agent is sodium bicarbonate. Sodium bicarbonate is inexpensive, non-flammable and begins to decompose at a low temperature; however, it is used only to a very limited extent. Differential thermal analysis has shown that sodium bicarbonate decomposes over a broad temperature range and this range is endothermic, contributes to an open cell structure in the finished product, and the released gas (carbon dioxide) diffuses through the polymer at a much greater rate than nitrogen gas. Presently used endothermic chemical blowing or blowing agents are mostly mixtures of sodium bicarbonate and citric acid and/or sodium hydrogen citrate. The citric acid and/or the citrate is incorporated together with the sodium bicarbonate in order to facilitate a complete acid assisted decomposition reaction to produce carbon dioxide gas. The mixture is also available in various polymers (such as polyethylene) as concentrate. The mixture is also available as a hydrophobized acid and carbonate which is a free non-dusting powder. The major advantages associated with utilizing endothermic blowing or blowing agents over their exothermic counterparts include short degassing cycles, small cells, smooth surfaces, weight reductions, reduced cycle times, foamed products which have promptly paintable surfaces, the blowing process is odorless, and the components of the blowing agents are generally regarded as environmentally safe.

According to the present invention, endothermic or exothermic organic or inorganic thermal decomposable blowing agents are employable as the chemical blowing agent (C).

Examples of the thermally decomposable blowing agents which may be used according to the invention include inorganic blowing agents, such as sodium hydrogencarbonate, sodium carbonate, ammonium hydrogencarbonate, ammonium carbonate and ammonium nitrite; nitroso compounds, such as N,N'- dimethyl-N,N'-dinitrosoterephthalamide and N.N'-dinitrosopentamethylene- tetraamine; azo compounds, such as azodicarbonamide, azobisisobutyronitrile, azocyclohexylnitrile, azodiaminobenzene and barium azodicarboxylate; sulfonylhydrazide compounds, such as benzenesulfonylhydraz.de, toluene- sulfonylhydrazide, p,p'-oxybis(benzenesulfonylhydrazide) and diphenylsulfone- 3,3'-disulfonylhydrazide; and azide compounds, such as calcium azide, 4,4'- diphenyldisulfonylazide and p-toluenesulfonylazide.

Preferably endothermic chemical blowing agents comprising a mixture of an organic carboxylic acid and an inorganic carbonate are used. The carboxylic acid can be selected from the group of organic mono-, di-, or polycarboxylic acids. Typically, the organic carboxylic acid is a solid at room temperature. The preferred polycarboxylic acid is citric acid. However, for purposes of the present invention, other suitable carboxylic acids include those of the formula: HOOC- R⁴-COOH wherein R⁴ is a hydrocarbon group containing about 1 to about 8 carbon atoms and which may also be substituted by one or more hydroxyl groups and/or keto-groups and which may also contain at least carbon-carbon double bonds. Also included are salts and half salts. Preferred polycarboxylic acids include citric acid, fumaric acid, tartaric acid, sodium hydrogen citrate and disodium citrate. The preferred inorganic carbonate utilized in the invention is sodium aluminum hydroxy carbonate. However, acceptable results are also achieved by also using sodium bicarbonate as well as alkali and alkaline earth metal carbonates and carbonates generally.

The chemical blowing agent (C) is used in an amount of from about 0.4 to about 4 parts by weight, preferably from about 0.4 to about 3.2, most preferred about from 0.4 to about 1.2 parts by weight of the active ingredient, based upon 100 parts by weight of the total of the cross-linked thermoplastic elastomer composition (A) and the olefin plastic (B) and the blowing agent (C).

In a commercialised blowing agent about 4 to about 40 wt.-% of the active ingredients may be comprised in a polymeric masterbatch (carrier), such as polyethylene or LLDPE.

A blowing assistant may be added according to necessity. Examples of the blowing assistants include compounds of various metals such as zinc, calcium, lead, iron and barium, organic acids such as salicylic acid, phthalic acid and stearic acid, and urea or their derivatives. The blowing assistant has functions of decreasing a decomposition temperature of the blowing agent, accelerating decomposition of the blowing agent, producing uniform cells, etc. Exemplary chemical blowing agents are commercially available under the trade designations Hydrocerol^® BIH 40 (supplied by Clariant), Palmarole^® BA.M4.E (from ADEKA Palmarole) or Tracel^® (from Tramaco).

The foamable thermoplastic elastomer compositions of the present invention are prepared by dry blending or tumble blending the fully cured thermoplastic rubber (A), the thermoplastic resin (B) and the chemical blowing agent (C) in the amounts as specified herein-above.

In an alternative embodiment only the thermoplastic rubber (A) and the thermoplastic resin (B) are dry blended to form a pre-blend which is mixed with a sufficient amount of the chemical blowing agent (C) before charging into the feed hopper of an extruder.

Robotic Extrusion

The thermoplastic elastomer composition according to this invention is supplied via an extruder and a heated pressure hose to a heated extrusion die. The die is guided by a robot, and the elastomer is extruded and laid by means of the extrusion die onto the surface. Thus, the present invention consists of supplying the thermoplastic elastomer to the surface of the article where it is to be applied, if necessary after an appropriate pretreatment of the surfaces. The die is guided by an automatic handling device and the elastomer is extruded and applied by means of the extrusion die on the surface of the article.

For the method according to this invention, usual screw extruders may be used, which heat the thermoplastic elastomeric material to the necessary processing temperature by external cylinder heaters. The melted elastomer is supplied to the extrusion die via a flexible hose, also provided with a suitable heater, which hose must be capable of resisting the high pressures corresponding to the viscosity of the thermoplastic elastomer. The extrusion die is also heated by means of a suitable heater to the necessary processing temperature of the elastomer and is guided by means of a robot, for instance, along the edge of the article. For further particulars about robotic extrusion reference is made to United States Patent No. 5,336,349 to Cornils, et al. the disclosure of which is incorporated herein by reference in its entirety.

To produce a foamed extrudate the dry blend is typically processed in a long- barrel extruder having a barrel length/diameter (L/D) ratio in the range from about 24:1 to about 60:1 , fitted with a screw which provides a compression ratio greater than about 2.5:1 , and a substantially constant pressure on the melt within the barrel. In one embodiment the diameter of said barrel is in the range from about 2.54 cm to about 15.24 cm. The extrudate may also be produced in a tandem- or twin screw-extruder.

Due to the low viscosity of the melted blend as specified above pressures in the range from about 30 to about 150 bar, preferably from about 50 to about 120 bar, most preferably from about 60 to about 100 bar are sufficient for the extrusion of the foamed extrudates according to the invention. The pressure is maintained throughout the barrel of the extruder and the heated hose to prevent foaming before the melt has reached the extrusion die.

The blowing agent used is preferably activated in the feed zone of the extruder. A reverse temperature profile is maintained in the barrel of the extruder. In that reverse temperature profile the temperature in the feed zone near the feed hopper is from about 190°C and about 220°C, preferably up to about 210°C, most preferably about 200°C and the temperature in the discharge zone (die) is from about 150 to about 180 °C, preferably about 170°C. For the special purpose of robotic extrusion according to the present invention the melted elastomer composition is supplied from the discharging zone of the extruder to the extrusion die through a flexible pressure hose, also provided with a suitable heater, which hose must be capable of resisting the high pressures corresponding to the viscosity of the thermoplastic elastomer. The extrusion die is also heated by means of a suitable heater to the necessary processing temperature of the elastomer and is guided by means of a robot along the edge of an work-piece. Depending on the needs the pressure hose may have a length between about 20 cm and about 6.0 m, and a diameter of between about 5 mm and 50 mm.

In one embodiment the die is a tapered conical die having an upstream face and a downstream face said die including a stepped land having a choked funnel-shaped portion terminating in a lateral portion, said lateral portion having a length (L) to diameter (D) ratio in the range from about 3:1 to 1 :3; said choked funnel portion having a conical angle in the range from about 60 to 120 and extending longitudinally in the range from about 0.25 to 1.5 times said barrel's diameter, length of said funnel portion being measured from said upstream face to the upstream end of said lateral land.

In one embodiment the length of said lateral land is from about 0.60 mm to about 5 mm, irrespective of the dimensions of the choked funnel portion. In a preferred embodiment said lateral land is about 1.225 mm to about 2.5 mm axial length, and said choked funnel portion is from about 0.5 to 1.0 times the diameter of said barrel.

For further particulars about the extrusion of foamable elastomers reference is made to published international patent application WO 99/58314 (PCT/US99/10220) and US-A-6,329,439 the disclosure of which is incorporated herein by reference. By means of the method of the present invention, a foamed article with superior properties can be applied directly to the surface of a work-piece, for instance a glass pane. Depending on the circumstances it might be necessary to pretreat the surface with a suitable adhesion promoter.

The foamed extrudate according to the invention has foam-rubber like properties. The foam has a specific gravity of less than about 0.9 g/cm³, preferably of less than about 0.8 g/cm³, most preferably of less than about 0.7 g/cm³. The lowest specific gravity achievable is at least 0.3 g/cm³.

The foam obtained is a substantially closed cell foam. By "substantially closed cell foam" there is meant a foam which contains, with preference in the order given, more than about 95, 96, 97, 98 or 99 % closed cells, the closed cell content being determined in correlation with the water-absorption and by visual examination of the foam surface). Ideally, the foam obtained is of 100 % closed cell structure. This leads to foamed articles having a very low water absorption. The water absorption is determined by the method of ASTM D570-98, and is less than about 5 % by weight, preferably less than about 3 % by weight, most preferably less than about 2 % by weight.

The average cell-size of the foams according to the invention is in the range from about 0.01 to 1 mm, preferably about 0.02 to about 0.5 as determined visually.

The foam advantageously has an average cell size of from about 0.05 to about 2.0, more preferably from about 0.1 to about 1.0 and most preferably about 0.15 to about 0.5 mm determined by visual examination by microscope.

The present invention further relates to an automotive screen having a sealing profile along or to the edge of the glass module manufactured by robotic extrusion. When the glass pane is placed in the window frame of the automobile body, this elastic bends about the peripheral surface of the glass pane and thus ensures an automatic centering of the glass pane in the window opening. Furthermore, the lip fills the gap between the peripheral face of the glass pane and the flange of the window frame, opposite this peripheral face. Instead of this lip, a hose-like hollow profile may be provided, which fulfils the same purpose.

The method and device which has been illustrated above in the case of an automobile glazing with a profiled foamed frame may be used as well in each case where a profiled foamed gasket or band is to be extruded directly onto the surface of any article and anywhere on this surface. They can find utility in the automobile industry as seals or profiles for doors, trunks, hoods or mobile roofs in household appliances such as for refrigerator doors, washing machine seals, in the building industry for prefabricated insulating glazing, door or window seals, and in industry in general for lids or cover seals, pipe gaskets or casing seals, cables or hoses, in textile or clothing industry for clothing seals, reinforcing elastomer band, boot seals and so on. By the method according to the present invention any rigid substrate, such as wood, metal, plasic, concrete stone, can be manufactured having a sealing profile along the edge.

In each case, depending on the nature of the substrate the use of a primer to guarantee a good adhesion might be necessary. It is up to the man skilled in the art to find out which primer is the most adequate to promote the adhesion of a given polymer on each substrate for instance plastic or painted material.

The following examples are presented to illustrate the invention which is not intended to be considered as being limited thereto. In the examples and throughout percentages are by weight unless otherwise indicated.

While in accordance with the patent statutes, the best mode and preferred embodiment have been set forth, the scope of the invention is not limited thereto, but rather by the scope of the attached claims.

Examples

In the Examples the following components have been used:

Thermoplastic rubber (A): Santoprene _®^ 8211-35W237; a dynamically fully cured blend of EPDM and polypropylene

Shore A hardness= 35 (ASTM D2240-02 @ 5 seconds delay), commercially available from Advanced Elastomer Systems, L.P., Akron, U.S., adding about 3.0 wt,-% carbon black (Cabot® PE 2272).

Thermoplastic polyolefin (B): B1: Elvax^® 265; an ethylene vinylacetate (EVA) copolymer containing about 28 % vinylacetate and having a melt flow rate of about 3.7 g/10 min (ASTM D1238-01 @ 213°C/ 2.16 kg)

B2: Elvax^® 360; an ethylene vinylacetate (EVA) copolymer containing about 25 % vinylacetate and having a melt flow rate of about 2.0 g/10 min (ASTM D1238-01 @ 213°C/ 2.16 kg) B3: Adflex^® X 100 G; an ethylene/propylene/ butene-1 terpolymer having a melt-flow rate of about 8.0 g/10 min (ASTM D1238-01 @ 213°C/ 2.16 kg)

B4: Kraton^® G 1650 (Shell), a styrene-ethylene- butene-styrene (SEBS) block copolymer containing 30% styrene by weight and having a melt flow rate of less than about 0.1 g/10 min (ASTM D1238-01 @ 200°C75.0 kg) Chemical blowing agent (C):

C1 : Hydrocerol^® BIH 40 (from Clariant)

40% dispersion of citric acid/bicarbonate in polyethylene C2: Tracel^® IM 7200 (from Tramaco)

The extrusion was carried out by feeding the foamable thermoplastic elastomer composition to a 30 mm single-screw extruder being equipped with a 2 m electrically heated (175°C) high pressure hose and a two different dies being selected from those producing a rod of 3 mm diameter for the extrusion with backpressure and a rod of 10 mm diameter for the extrusion without backpressure. As a result of these different dies the extrusion speeds (measured as screw revolutions per minute of the extruder) reached levels from about 60 to 75 rpm, i.e., low speeds for the low diameter die and higher speeds for the larger diameter die.

Extrusion without back pressure (free flowing from the die exit) and with back pressure (by pressing the die onto the glass plate the adequate back pressure is provided).

The obtained foamed extrudate was tested with respect to its density, surface properties, closed cell content, compression set.

Extrudability: "+" = good (closed cell, smooth surface)

"o" = acceptable

"-" = not acceptable (for instance open celled and rough surfaced)

Foam density: determined according to ISO 1183

Surface smoothness: The raw material has been extruded into strips under standard conditions. The surface smoothness of the extruded strip is measured with a stylus profilometer (Model EMD-04000W5 Surfanalyzer System 4000 including a universal probe with 200 mg stylus force, Federal Products Corp., 1144 Eddy St., P.O. Box 9400, Providence, Rl 02940-9400, or equivalent. The arithmetic average of the surface irregularity (R_a) is used to quantify surface smoothness. The median value of three measurements has been reported.

Closed/Open cell content: As a result of the water absorption according to

ASTM D 570-98

Hardness (Shore A): ASTM D 2240-02 Compression set: ASTM D 395-01 : 24h@RT, 70°C and 100°C with 25% compression

Average cell size: The cell size of the extruded foam was determined by microscope with the Image-Pro Plus Software (from MediaCybemetics, http://www.mediacy.com) as follows: Photos of the foam are measured relative to a known magnification. An image of a piece with a known size and with the same magnification is used as a calibration. Appearance: The appearance of the extruded foam has been assessed visually and rated as follows

"+" = good

"o" = acceptable

"-" = not acceptable TABLE 1

TABLE 2

= not available (due to the absence of stable foams)

Claims

What is claimed is:

1. A foamable thermoplastic elastomer composition comprising

(A) a thermoplastic rubber comprising i. a fully cured rubber; and ii.a thermoplastic polyolefin homopolymer or copolymer wherein said rubber (A) has a Shore A hardness from about 35 to about 85 (measured according to ASTM D2240-02);

(B) a thermoplastic resin selected from the group consisting of random or block copolymers of C₂ to C12 mono-olefins and vinyl acetate, terpolymers of C₂ to C₁₂ mono-olefins, and blends thereof; said thermoplastic resin (B) having a melt flow rate from about 0.2 to about 5.0 (measured according to ASTM D1238-01 at 230°C/2.16 kg load); and (C) a chemical blowing agent.

2. The composition of claim 1 wherein the fully cured rubber (i) is selected from the group consisting of ethylene/alpha-olefin/non-conjugated diene copolymer rubbers, copolymer rubbers of monomers comprising ethylene and at least one other alpha-olefin of the formula CH₂=CHR wherein R is an alkyl residue of about 1 to about 12 carbon atoms, butyl rubber, halogenated butyl rubber, copolymers of C₄ to C₁₂ isomonoolefins and para-alkylstyrene or their halogenated derivatives, natural or synthetic rubbers, polyisoprene rubber, polybutadiene rubber, styrene/butadiene copolymer rubbers, polychloroprene rubber and blends thereof.

3. The composition of claim 1 wherein the fully cured rubber (i) is an ethylene/propylene/non-conjugated diene rubber (EPDM).

4. The composition of claim 1 wherein the thermoplastic polyolefin (ii) is selected from the group consisting of homopolymers or copolymers of olefinic C₂ to C monomers or copolymers thereof with (meth)acrylates.

5. The composition of claim 4 wherein the thermoplastic polyolefin (ii) is a copolymer of ethylene with (meth)acrylates.

6. The composition of anyone of claims 1 wherein the thermoplastic polyolefin (ii) is polypropylene.

7. The composition of claim 1 wherein the ethylene vinyl acetate (B) comprises about 10 to about 40 weight percent of vinyl acetate, based on the total weight of ethylene vinyl acetate.

8. The composition of claim 1 wherein the terpolymer of C₂ to C₁₂ monoolefins (B) is an ethylene-propylene-butene-1 random terpolymer.

9. The composition of claim 1 wherein said chemical blowing agent (C) is selected from the group consisting of endothermic and exothermic chemical blowing agents.

10. The composition of claim 9 wherein the endothermic chemical blowing agent comprises a mixture of a carboxylic acid and an inorganic carbonate.

11. The composition of claim 1 comprising from about 80 to about 98 weight percent of said a thermoplastic rubber (A), based upon the total weight of (A), (B) and (C).

12. The composition of claim 1 comprising from about 1 to about 10 weight percent of said thermoplastic resin (B), based upon the total weight of (A), (B) and (C).

13. The composition of claim 1 comprising from about 1 to about 10 weight percent of said chemical blowing agent (C), based upon the total weight of (A), (B) and (C).

14. A method of producing a foamed extrudate comprising the steps of: (1) charging a foamable thermoplastic elastomer composition comprising

(A) a thermoplastic rubber comprising i. a fully cured rubber; and ii.a thermoplastic polyolefin homopolymer or copolymer wherein said rubber (A) has a Shore A hardness from about 35 to about 85 (measured according to ASTM D2240-02);

(B) a thermoplastic resin selected from the group consisting of random or block copolymers of C₂ to C₁2 mono-olefins and vinyl acetate, terpolymers of C₂ to C₁₂ mono-olefins, and blends thereof; said thermoplastic resin (B) having a melt flow rate from about 0.2 to about 5.0 (measured according to ASTM D1238-01 at 230°C /

2.16 kg load); and

(C) a chemical blowing agent, into the barrel of an extruder comprising plural temperature zones including a feed-zone, a transition-zone, a metering-zone, a front- zone and a discharge-zone;

(2) maintaining a temperature profile within said barrel wherein temperature in said feed-zone is not lower than the temperature of the succeeding zones; and

(3) discharging the extrudate via a heated extrusion die.

15. The method of claim 14 wherein the discharge-zone of the extruder is connected to the extrusion die via a heated high-pressure hose.

16. The method of claim 15 wherein the foamed extrudate of the thermoplastic elastomer is extruded onto an article positioned in a processing region of an automatic handling unit wherein the melted polymer is extruded from the extrusion die while guiding the die along to a surface of said.

17. The method of claim 14 wherein the composition comprises a fully cured rubber (i) selected from the group consisting of ethylene/alpha-olefin/non- conjugated diene copolymer rubbers, copolymer rubbers of monomers comprising ethylene and at least one other alpha-olefin of the formula CH₂=CHR wherein R is an alkyl residue of about 1 to about 12 carbon atoms, butyl rubber, halogenated butyl rubber, copolymers of C₄ to C₁2 isomonoolefins and para-alkylstyrene or their halogenated derivatives, natural or synthetic rubbers, polyisoprene rubber, polybutadiene rubber, styrene/butadiene copolymer rubbers, polychloroprene rubber and blends thereof.

18. The method of claim 14 wherein the composition comprises a fully cured rubber (i) which is an ethylene/propylene/non-conjugated diene rubber (EPDM).

19. The method of claim 14 wherein the composition comprises a thermoplastic polyolefin (ii) selected from the group consisting of homopolymers or copolymers of olefinic C₂ to C₇ monomers or copolymers thereof with (meth)acrylates.

20. The method of claim 14 wherein the composition comprises a copolymer of ethylene with (meth)acrylates as thermoplastic polyolefin (ii).

21. The method of claim 14 wherein the composition comprises polypropylene as thermoplastic polyolefin (ii).

22. The method of claim 14 wherein the composition comprises ethylene vinyl acetate (B) which comprises about 10 to about 40 weight percent of vinyl acetate, based on the total weight of ethylene vinyl acetate.

23. The method of claim 14 wherein the composition comprises a terpolymer of C₂ to Ci₂ monoolefins (B) which is an ethylene-propylene-butene-1 random terpolymer.

24. The method of claim 14 wherein composition comprises a chemical blowing agent (C) which is selected from the group consisting of endothermic and exothermic chemical blowing agents.

25. The method of claim 14 wherein the composition comprises a endothermic chemical blowing agent which comprises a mixture of a carboxylic acid and an inorganic carbonate.

26. The method of claim 14 wherein the composition comprises from about 80 to about 98 weight percent of said a thermoplastic rubber (A), based upon the total weight of (A), (B) and (C).

27. The method of claim 14 wherein the composition comprises from about 1 to about 10 weight percent of said thermoplastic resin (B), based upon the total weight of (A), (B) and (C).

28. The method of claim 14 wherein the composition comprises from about 1 to about 10 weight percent of said chemical blowing agent (C), based upon the total weight of (A), (B) and (C).

29. Extruded foamed article obtainable by a method comprising the steps of:

(1) charging a foamable thermoplastic elastomer composition comprising

(A) a thermoplastic rubber comprising i. a fully cured rubber; and ii. a thermoplastic polyolefin homopolymer or copolymer wherein said rubber (A) has a Shore A hardness from about 35 to about 85 (measured according to ASTM D2240-02); (B) a thermoplastic resin selected from the group consisting of random or block copolymers of C₂ to C₁₂ mono-olefins and vinyl acetate, terpolymers of C₂ to C12 mono-olefins, and blends thereof; said thermoplastic resin (B) having a melt flow rate from about 0.2 to about 5.0 (measured according to ASTM D1238-01 at 230°C / 2.16 kg load); and

(C) a chemical blowing agent, into the barrel of an extruder comprising plural temperature zones including a feed-zone, a transition-zone, a metering-zone, a front- zone and a discharge-zone; (2) maintaining a temperature profile within said barrel wherein temperature in said feed-zone is not lower than the temperature of the succeeding zones; and

(3) discharging the extrudate via a heated extrusion die.

30. Extruded foamed article according to claim 29 selected from the group consisting of seals, profiles, gaskets, cables and hoses.

31. A rigid substrate comprising a sealing profile along the edge manufactured by the steps of:

(1) charging a foamable thermoplastic elastomer composition comprising

(A) a thermoplastic rubber comprising i. a fully cured rubber; and ii. a thermoplastic polyolefin homopolymer or copolymer wherein said rubber (A) has a Shore A hardness from about 35 to about 85 (measured according to ASTM D2240-02);

(B) a thermoplastic resin selected from the group consisting of random or block copolymers of C₂ to C-ι₂ mono-olefins and vinyl acetate, terpolymers of C₂ to C-ι₂ mono-olefins, and blends thereof; said thermoplastic resin (B) having a melt flow rate from about 0.2 to about 5.0 (measured according to ASTM D1238-01 at 230°C / 2.16 kg load); and

(C) a chemical blowing agent, into the barrel of an extruder comprising plural temperature zones including a feed-zone, a transition-zone, a metering-zone, a front-zone and a discharge-zone;

(2) maintaining a temperature profile within said barrel wherein temperature in said feed-zone is not lower than the temperature of the succeeding zones; and

(3) discharging the extrudate via a heated extrusion die along the edge of the rigid substrate.

2. The rigid substrate according to claim 31 having a sealing profile along the edge wherein the substrate is an automotive windscreen.