KR100856166B1 - Foamable polymeric compositions and articles containing foamed compositions - Google Patents

Abstract

(a) 100 parts by weight of one or more optionally hydrogenated block copolymers having a resinous block A of at least two predominantly polymerized non-hydrogenated monovinylarenes and optionally a hydrogenated elastomer block B , Block B prior to hydrogenation is a predominantly polymerized conjugated diene or diene, and the block copolymer has a total apparent molecular weight of at least 250 kg / mol, preferably at least 350 kg / mol and has a substantial weight of at least 18 kg / mol. Molecular weight polymerized monovinylarene block), (b) at least two predominantly polymerized non-hydrogenated monovinylarene resin block A ', and optionally hydrogenated elastomer block B' 5 to 50, preferably 15 to 40 parts by weight, optionally hydrogenated, one or more block copolymers (wherein said block B 'prior to hydrogenation has a small proportion, i.e. up to 25 wt% Derived from polymerized conjugated dienes or dienes, which may be mixed with polymers (e.g., aromatic vinyl), the block copolymers having a total apparent molecular weight in the range of 50 to 180 kg / mol, while resinous block A 'Represents an actual molecular weight in the range of 3 to 20 kg / mol, preferably in the range of 5 to 15 kg / mol), (c) a Vicat softening temperature in the range of 130 ° C. to 180 ° C., an MFR of 0.5 to 30 dg / min and at least 4.5 25 to 80 parts by weight of a linear crystalline polymer containing propylene as a main component, having a polydispersity index, (d) 100 to 250 parts by weight of a softener compatible with blocks B and B ', (e) (a) to 0.01 to 3 wt% of the weight of the primary component up to (e), a chemical solid nucleating agent of the endothermic group mixed with a blowing agent, and optionally (f) PPO compatible with the block copolymer component (a) and And / or any resins, antioxidants, UV-stabilizers, flame retardants, interfacial dogs A foamable composition, useful for making a flexible, heat resistant, foamed thermoplastic elastomeric article containing at least one secondary component selected from nitriles and inorganic fillers.

Foaming composition, block copolymer, nucleating agent, foaming agent, permanent compression rate

Description

FOAMABLE POLYMERIC COMPOSITIONS AND ARTICLES CONTAINING FOAMED COMPOSITIONS

The present invention relates to a foamable composition, ie a polymer composition that can be used to produce a foamed composition. The present invention further relates to pre-blends containing at least two components of the polymer composition and articles containing foamed compositions.

Foamed polymeric compositions are well known in the art and are widely used in the industry for various purposes.

Although compositions containing optionally hydrogenated block copolymers of monovinyl aromatic hydrocarbons and conjugated dienes exhibit interesting properties, the foam compositions available so far have been found in modern foam articles such as automobiles, ships, It does not meet the existing combinations of physical properties required for foam weather seal articles for aircraft and their analogs. Currently required physical properties include foam densities in the range of 0.3 to 0.8 10 ³ kg / m ³ , preferably 0.4 to 0.6 10 ³ kg / m ³ ; Foam density reduction in the range from 25% to 70%, preferably in the range from 33% to 55%; Shore A hardness of less than 70, preferably less than 65; And a compression set of 70% or less, preferably 55% or less (measured on a non-foamed injection molded test plate, 6 mm thick) at 100 ° C.

Only the selectively hydrogenated block copolymers of monovinyl aromatic hydrocarbons and conjugated dienes having a relatively high molecular weight, i.e., a total molecular weight of at least 350,000, result in a final article that exhibits too high hardness when mixed with oils and large quantities of polyolefins. It was found that foamability was maintained up to an acceptable rate of density reduction that resulted.

In contrast, it has been found that selectively hydrogenated block copolymers of monovinyl aromatic hydrocarbons and conjugated dienes, having molecular weights of 180,000 or less, can be foamed without a small amount of polyolefins or polyolefins. However, an important drawback of the foam compositions was poor heat resistance.

Also known in US Pat. No. 6,221,964 is the preparation of foamed compositions containing thermoplastic vulcanizates, which are foamed mechanically by means of water or other physical blowing agents.

In general, the foamed compositions were prepared by mixing EPDM, polyolefin (more specifically polypropylene) and oil as the main component in an extruder together with a crosslinking agent.

Known disadvantages of the foamed compositions derived from thermoplastic vulcanizates are that they readily absorb moisture and the balance between absorbency and tear resistance is not very good. Thus they could not be used for weather seal articles.

US Pat. No. 4,764,535 and US Pat. No. 4,677,133 are known elastomer compositions which can be foamed into elastomeric cellular products. This elastomeric composition contained a mixture of two thermoplastic rubber compounds, a nucleating agent that enhances the hydrophilic structure, an unstable detackifying resin, and optionally a polybutene and / or amorphous polypropylene. However, the final physical properties of the foamed articles did not meet current requirements and, in particular, proved to be lacking in heat resistance.

EP 0875526 A discloses elastomeric foams made from a renewable mixture of thermoplastic vulcanizates and elastomeric thermoplastic polymers, which have two or more poly (styrene) blocks or poly (substituted styrene) blocks per polymer molecule. To a block copolymer, or a polymer having 40 wt% or more of ethylene repeat units, or a combination thereof. It was clearly shown in the table that a composition containing an optionally hydrogenated block copolymer containing poly (styrene) blocks and poly (butadiene) or poly (isoprene) blocks prior to hydrogenation cannot be foamed with water. On the other hand, compositions containing similar non-hydrogenated block copolymers could not meet the requirements for heat resistance and UV resistance.

US 6127444 discloses (a) 100 parts by weight of block copolymers containing at least two outer monovinyl aromatic hydrocarbon blocks and at least one hydrogenated inner conjugated diene block, wherein the total content of monovinyl aromatic hydrocarbons is 20 wt% to 50 wt%, and the total apparent molecular weight is 140,000 g / mol to 400,000 g / mol); (b) plasticiser, 50-250 phr; (c) polybutene-1 polymer having a melt index of 0.05 to 400 at 2.16 kg / 190 DEG C., 10 to 100 phr; And (d) polymer compounds containing blowing agents are known. The invention further relates to the use of the compounds for the preparation of foamed compounds; Foaming method; Masterbatch mixtures; Foamed compounds; And an article comprising the foamed compound. The final physical properties of the foamed articles derived from these compositions have been found to be unable to meet current combinations of requirements, specifically heat resistance.

IT 1317261 incorporates a first component containing at least one thermoplastic elastomer, a plastomer and a plasticizer at 160-210 ° C. with a second component containing an elastomer containing at least one blowing agent, followed by 180 BACKGROUND OF THE INVENTION The production of elastomeric foams and the manufacture of stoppers and corks by compression molding at −210 ° C. are known. This blowing agent was pure or modified azodicarbonamide, or a mixture of NaHCO ₃ and citric acid. The elastomer was styrene-ethylene-butylene copolymer (SEBS), styrene-ethylene-propylene copolymer (SEPS or SEEPS) or styrene-butadiene (SBS). Plastomers were selected from polypropylene, propylene copolymers, ethylene-vinyl acetate copolymers or LDPE. The plasticizer was mineral oil. The shaped product had a Shore A hardness of 65-95. However, such foam compositions have been shown to be unable to withstand mechanical stress at temperatures above 70 ° and are too hard to be used as weatherstrips.

A similar product is known from WO 0102263, which contains a) at least one thermoplastic block copolymer, c) a blowing agent, and optionally d) at least one plasticizer, and additionally b) a melt flow index (2.16) of 0.05 to 400. Provided is a synthetic bottle cap made of a foamed thermoplastic elastomer composition characterized by containing at least one branched polyolefin having kg / 190 DEGC, measured according to ASTMD 1238).

In WO 026103, easily removable synthetic closures are known which are suitable for removable inserts in bottles or containers. In one embodiment, the synthetic stopper contains an ethylene / alpha-olefin copolymer promoted with a thermoplastic elastomer and a metallocene catalyst. In another embodiment, the synthetic stopper may comprise a thermoplastic elastomer containing a styrenic block copolymer; Ethylene / alpha-olefin copolymers; Polypropylene copolymers; And a composition formulated with a component containing a blowing agent, the closure having a Shore A hardness in the range of 60 to 84. This synthetic stopper may additionally contain extending oils and / or processing additives. In optional embodiments, compositions suitable for forming the synthetic plugs of the present invention optionally include thermoplastic elastomeric materials such as thermoplastic polyurethane elastomers (ie, TPUs), polyolefin-based thermoplastic elastomers (ie, TPOs), dynamically vulcanized Thermoplastic elastomers based on elastomer-thermoplastic mixtures (ie TPVs), thermoplastic polyether ester elastomers, thermoplastic elastomers based on halogen-containing polyolefins and polyamide based thermoplastic elastomers.

Flexible, heat-resistant, difficult and complex shaped closed cell extruded articles, wherein the foamed material has a uniform independent bubble structure in all directions and no substantial debris material It will be appreciated that there is still an increasing demand for thermoplastic foamable compositions that can be efficiently processed. It is therefore an object of the present invention to provide an improved thermoplastic elastomer foam which is soft, low viscosity and further exhibits excellent permanent compression and absorbency, as already described herein above.

As a result of extensive research and experiments, the targeted foamable compositions have been surprisingly found.

Disclosure of the Invention

Therefore, the present invention relates to a foamable composition that can be used to prepare a flexible, heat resistant, foamed thermoplastic elastomeric article, the composition comprising at least:

(a) 100 parts by weight of one or more optionally hydrogenated block copolymers having a resinous block A of at least two predominantly polymerized non-hydrogenated monovinylarenes and optionally a hydrogenated elastomer block B , Block B prior to hydrogenation is a predominantly polymerized conjugated diene or diene, and the block copolymer has a total apparent molecular weight of at least 250 kg / mol, preferably at least 350 kg / mol and has a substantial weight of at least 18 kg / mol. Contains a polymerized monovinylarene block of true molecular weight),

(b) optionally at least two block copolymers 5 to 5 having resinous blocks A 'of predominantly polymerized non-hydrogenated monovinylarene and optionally hydrogenated elastomer block B'; 50, preferably 15 to 40 parts by weight (wherein said block B 'before hydrogenation is a major component that may be mixed with other copolymers (e.g., vinyl aromatics) Derived from polymerized conjugated diene or dienes, wherein the block copolymer has a total apparent molecular weight in the range of 50 to 180 kg / mol, while resinous block A 'is 3 to 20 kg / mol, preferably 5 to 15 kg actual molecular weight in the range of / mol),

(c) a straight line containing propylene as the main component having a Vicat softening temperature in the range of 130 ° C to 180 ° C, an MFR of 0.5 to 30 dg / min and a polydisperity index of at least 4.5 25 to 80 parts by weight of the crystalline polymer,

(d) 100 to 250 parts by weight of a softener that is compatible with blocks B and B ',

(e) 0.01 to 3 wt% of the endothermic group's chemical solid nucleating agent mixed with a blowing agent, and, optionally, 0.01 to 3 wt% of the weight of the primary components (a) to (e), and

(f) PPO compatible with the block copolymer component (a) and / or at least one secondary component selected from any of resins, antioxidants, UV-stabilizers, flame retardants, interfacial modifiers and inorganic fillers.

In addition, the present invention contains, or at least contains, a foamed article made from the foamable composition described above, a foaming method using the foamable composition described above, and a composition (a) and at least one (c) and (d). The present invention relates to a pre-blend containing component (b) mixed with (c) and / or (d).

Embodiments of the Invention

Preferred copolymer structures of components (a) and (b) are each of the general formula ABA, (AB) _n X or ABA "B"; And A'B'A ', (A'B') _n X or A'B'A "B", where A, A 'and A "represent poly (monovinylarene) blocks, and B , B ', B "represents a hydrogenated poly (conjugated diene (s)) block, n is an integer greater than or equal to 2 and X is the remainder of the coupling agent.

It is understood that blocks A, A 'and A "are each different, that is, block A is larger than A', in turn A 'is larger than A", while blocks B, B' and B "may be the same or different. Preferably blocks B and B 'will be greater than or equal to B ".

More preferred copolymer component (a) has the general formula ABA or (AB) _n X and has a total apparent molecular weight in the range of 250 to 600 kg / mol, while the poly (monovinyl arene) block in the block copolymer (a) The content is in the range of 20 to 35 wt%.

Monovinyl aromatic monomers are typically styrene, C ₁ -C ₄ alkyl styrene and C ₁ -C ₄ dialkylstyrene, specifically sterin, α-methylstyrene, o-methylstyrene, or p-methylstyrene, 1,3 -Dimethylstyrene, p-tert-butylstyrene or mixtures thereof, most preferably styrene.

Conjugated diene monomers are typically 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene or mixtures thereof containing 4 to 8 carbon atoms, Preferred are conjugated diene monomers such as butadiene and / or isoprene, most preferably butadiene.

Most preferred block copolymers ABA contain substantially pure poly (styrene) blocks, each having an actual molecular weight in the range of 25 kg / mol to 60 kg / mol.

More preferred block copolymer component (b) has the general formula A′B; A ′ or (A′B ′) _n X and has a total apparent molecular weight in the range of 80 to 160 kg / mol.

Most preferred block copolymers, A'B'A 'or (A'B') _n X, contain substantially pure poly (styrene) blocks, each having an actual molecular weight of 5-15 kg / mol.

The preferred weight ratio of the block copolymer components (a) and (b) is 10 to 40 parts by weight of component (b) per 100 parts by weight of component (a).

It will be appreciated that the presence of two block copolymer components, each having a high molecular weight and a low molecular weight, and their specific mutual weight ratios are important. It has been found that if high molecular weight block copolymers are not present in the composition, or only in proportions below the specified range, inferior (too high) permanent compression rates and inferior foam stabilization will occur. It has been found that if low molecular weight block copolymers are not present, or only present in proportions below a certain range, poor foam density due to poor flow and / or poor hardness (too rigid foam) results.

These block copolymer components (a) and (b) are prepared by successive polymerization of each batch and by selective hydrogenation of B, B 'or B "in the block copolymers obtained, or in combination with a crosslinking agent, ABA or (AB) can be _n X block copolymers, each individually prepared by the initial preparation of living diblock AB, which can be selectively hydrogenated sequentially.

For example, block copolymers (a) and (b) may each be prepared by individually bonding at least two diblock copolymer molecules AB or A'B 'together. Since the binding efficiency is not 100%, the block copolymer (a) may comprise an unbound diblock copolymer. However, these block copolymer components (a) and (b) may each consist of a mixture of block copolymers, one of which may be a diblock copolymer.

Examples of binders include tin dichloride, monomethyl dichloride, dimethyltin dichloride, monoethyltin dichloride, diethyltin dichloride, methyltin trichloride, monobutyltin dichloride, dibutyltin dibromide, monochloride dichloride Tin binders such as hexyl tin and tin tetrachloride; Dichlorosilane, monomethyldichlorosilane, dimethyldichlorosilane, diethyldichlorosilane, monobutyldichlorosilane, dibutyldichlorosilane, monohexyldichlorosilane, dihexyldichlorosilane, dibromosilane, monomethyldichlorodiamine Halogenated silicone binders such as bromosilane, dimethyldibromosilane, silicon tetrachloride and silicon tetrabromide; Divinyl aromatic compounds such as divinyl benzene and divinyl naphthalene; Halogenated alkanes such as dichloroethane, dibromoethane, methylene chloride, dibromomethane, dichloropropane, dibromopropane, chloroform, trichloroethane, trichloropropane and tribromopropane; Halogenated aromatic species compounds such as dibromobenzene; Epoxy compounds such as diglycidyl ether of bisphenol-A (eg, EPON ^™ 825 or 826); And other binders such as benzoic esters, CO ₂ , 2-chloroprene and 1-chloro-1,3-butadiene.

Of these, EPON ^TM 825 or 826 diglycidyl ether, dibromobenzene, tetramethoxysilane and dimethyldichlorosilane are preferred.

The block copolymer components (a) and (b) used in the compounds of the present invention can be prepared by any method known in the art, including the full sequential polymerization method, optionally US 3231635. ; US3251905; US3390207; US3598887; And US4219627 and EP 0413294 A; EP0387671; It can be prepared with the re-initiaiton and coupling methods, as illustrated in EP0636654A and WO9422931.

Anionic polymerization of butadiene or similar conjugated dienes results in the polymer backbone (1,2- and 3,4-addition, respectively), which forms a residual branch within the polymer backbone (1,4-addition) or short branches, commonly called vinyl groups. This results in the bonding of the residual unsaturation attached. The degree of 1,2-addition (3,4-addition) can be controlled with a structure modifier such as diethyl ether or ethylglyme (1,2-diethoxyethane). As described in US RE27145E, incorporated herein by reference, the elastomeric physical properties of hydrogenated block copolymers require some short branching. Indeed, good elastomeric properties upon hydrogenation can be found in polymers having a 1,2-addition (3,4-addition) content of conjugated dienes of at least 30 mol% (based on conjugated dienes). For example, 78% 1,2-addition (in the scope of the present invention) is achieved during the polymerization by the presence of about 300 ppm 1,2-diethoxypropane (DEP) in the final solution.

Independent of the monomers and modifications used for all B blocks (B, B ', B "), it is noted that the ethylene content (result of hydrogenation of conjugated dienes added by the 1,4-addition method) should be lower than 70 wt%. Will be understood.

Generally, polymers useful in the present invention are prepared by contacting a monomer or monomers with an organoalkali metal compound in a suitable solvent at a temperature in the range of -150 ° C to 300 ° C, preferably in the range of 0 ° C to 100 ° C. Can be prepared. Particularly effective polymerization initiators are organolithium compounds of the general formula RLi, wherein R is aliphatic, cycloaliphatic, alkyl-substituted alicyclic, aromatic or alkyl-substituted with 1 to 20 carbon atoms. Aromatic hydrocarbon radicals, of which sec-butyl is preferred.

Suitable solvents include solvents useful for solution polymerization of polymers and include aliphatic, cycloaliphatic, alkyl-substituted cycloaliphatic, aromatic and alkyl-substituted aromatic hydrocarbons, ethers, and mixtures thereof. Thus, suitable solvents include aliphatic hydrocarbons such as butane, pentane, hexane and heptane; Alicyclic hydrocarbons such as cyclopentane, cyclohexane and cycloheptane; Alkyl-substituted alicyclics such as methylcyclohexane and methylcycloheptane; Aromatic hydrocarbons such as benzene; And alkyl-substituted hydrocarbons such as toluene and xylene; And ethers such as tetrahydrofuran, diethyl ether and di-n-butyl ether. Preferred solvents are cyclopentane or cyclohexane.

In the finally used block copolymers, the B and B 'and / or B "blocks are preferably hydrogenated selectively to a degree of at least 95%, while the poly (styrene) blocks are not hydrogenated at all, or at most 5%. Only hydrogenated to the extent.

Hydrogenation of such polymers can be carried out in a variety of well-established ways, including hydrogenation in the presence of catalysts such as Raney Nickel, precious metals such as platinum and palladium and soluble transition metal catalysts. Suitable hydrogenation methods that can be used are those in which a diene-containing polymer or copolymer is dissolved in an inert hydrocarbon dilution solution such as cyclohexane and reacted with hydrogen in the presence of a soluble hydrogenation catalyst to hydrogenate. Such methods are described in US Pat. Nos. US 3113986, US 4226952; US 3634549; US 3670054; US 3700633 and US RE27145E. The polymer is such that for producing a hydrogenated polymer having residual unsaturation in the polydiene block, preferably less than 5 wt%, preferably less than 1 wt% and more preferably as close to zero as possible to the original unsaturation prior to hydrogenation. Hydrogenated by the method. Titanium catalysts as disclosed in US Pat. No. 50,39,755 (incorporated herein by reference) may also be used in the hydrogenation process.

Hydrogenation degree can be analyzed using Nuclear Magnetic Resonance (NMR) method.

Preferred examples of component (a) are KRATON® G 1651, KRATON G MD 6917 ES, and KRATON G MD 6933 ES block copolymers, while preferred examples of component (b) are KRATON G 1650, KRATON G 1657, KRATON G1052, KRATON G RP 6924 block copolymer. Most preferred block copolymers (a) are KRATON MD 6933 ES and most preferred block copolymers (b) are KRATON G RP 6924 and KRATON G 1657.

The linear crystalline polyolefin (component c) is preferably a homopolymer or a mixture of polymers, which is a small proportion (ie less than 25 wt% of the monomer mixture) of ethylene or Predominantly contains propylene monomers or copolymers with predominant propylene together with separate alkylenes such as butylene.

Preferred polyolefins are MFR between 2 and 15 dg / min at 230 ° C / 2.16 kg (ISO 1133), Vicat softening temperature (ISO 305, condition A50 [50 ° C, 10N]) in the range from 130 to 170 ° C and polydispersity of at least 4.5 Can be characterized by a polydispersity index. Most preferred component (c) exhibits a broad molecular weight distribution, ie a polydispersity index of at least 5.

The polydispersity index (PI), defined by Zeichner and Patel, relates to the molecular weight distribution through strong correlation with Mw / Mn (Zeichner, GR and Pate, PD, Proc. 2nd World Congr. Chem. Eng 6, 373 (1981). For linear polypropylene (PP), PI is 10 ⁵ divided by the cross-over modulus Gc. This value is measured by means of the isothermal dynamic frequency shift in the linear viscoelastic region of the shaped material.

Examples of suitable crystalline polypropylenes are MOPLEN ^™ HP 502L (with PI of 5.49) and MOPLEN HP 1078 (with PI of 5.29) or mixtures thereof or mixtures thereof with other crystalline polypropylenes.

It will be appreciated that the form of the polymer selected for component (c) is somewhat important for obtaining the density and surface quality of the desired foam. If the melting temperature as a result of inadequate conditions is too high, a composition outside the scope of the present invention may exhibit poor (high) foam density and / or surface quality of the poor (rough) foam. . If the melt viscosity of component (c) is too high to inhibit the growth of appropriate bubbles, the same phenomenon as above occurs.

The preferred weight ratio of polyolefin to the weight of component (a) is 42 to 65 parts by weight per 100 parts by weight of component (a).

Component (d) is preferably a paraffinic or naphthenic plasticizer that is compatible with the B block in the block copolymer component, which leads to low fogging values.

Examples of the paraffinic plasticizers generally used include oils, preferably naphthenic or paraffinic oils and more preferably paraffinic oils. Examples of alternative plasticizers include aliphatic synthetic plasticizers or oligomers of randomly or continuously polymerized styrene and conjugated dienes, oligomers of conjugated dienes such as butadiene or isoprene, liquid polybutene-1, and ethylenepropylene rubber All the compounds have a weight average molecular weight in the range of 0.3 to 30 kg / mol, preferably 0.5 to 25 kg / mol and more preferably 0.5 to 10 kg / mol. Preferred component (d) is PRIMOL ^™ 352 paraffinic oil.

In conventional foam compositions, metal salts of colloidal silicates, carbon blacks and aliphatic acids have been used as nucleating agents. These were used in amounts ranging from 0.25 to 5 wt% relative to the weight of the elastomeric composition. The chemical solid nucleating agent (s) is preferably selected from NaHCO ₃ and a mixture of citric acid or sodium citrate. Preferred amounts of the chemical solid nucleating agent range from 0.5 to 1 wt%, based on the weight of components (a) to (d).

In order to obtain a normal independent bubble structure, a blowing agent as well as a nucleating agent should be used. These two components may be mixed, for example dispersed in a poly (olefin) based masterbatch having a low melting point. For example, HYDROCEROL ^™ BIH40 is an endothermic chemical blowing agent that also acts as a nucleating agent and releases CO ₂ and water. It has now been found that a fairly good normal distribution of the derived gas can be obtained using a small amount of the specific nucleating agent described above. The use of certain combinations of ingredients avoids the use of unstable detackifying resins, which have conventionally been used to obtain a closed, smooth foamed surface.

The foamable compositions of the present invention contain chemical or physical blowing agents, in addition to mixtures with the aforementioned nucleating agents. Generally, the blowing agent may be selected from CO ₂ , N ₂ or water; And non-toxic physical blowing agents such as compounds that decompose above a certain temperature to release nitrogen, carbon dioxide or water to increase the volume of the reaction mass. Nitrogen as well as carbon dioxide are preferred blowing agents.

Such blowing agents are used in amounts of 0.5 to 10 wt%, based on the weight of the total composition. Among the chemical blowing agents, the preferred blowing agent is HYDROCEROL ^™ BIH40 (also acts as nucleating agent). Alternative but less preferred blowing agents include CENITRON ^™ PB 10 (nitrogen release) and CYLACELL ^™ (water vapor release).

The optional PPO resin, if present, is primarily compatible with the block copolymer (a) and in an amount up to 80 parts by weight of the block copolymer component (a), preferably 100 weight of the block copolymer (A). It may be contained in the foamable composition of the present invention in an amount of 20 to 50 parts by weight per part.

As previously pointed out, the foamable compositions of the present invention may also additionally contain secondary components. The amount of secondary components such as blowing agents, primary or secondary antioxidants, UV-stabilizers, surface modifiers (e.g., waxes, silicone oils and chemamides, fluorine polymers) is known in the art. It may be contained as. Inorganic fillers such as CaCO ₃ , talc, TiO ₂ , carbon black may also be contained in amounts of up to 100 parts by weight per 100 parts by weight of the composition (a). In addition, chemical compounds that discharge water, such as metal salts containing hydrated water, metal hydroxides, organic diacids that form anhydrides, and mixtures of components that release water through polycondensation reactions can be used.

The foam according to the invention has a foam density in the range from 0.3 to 0.8 10 ³ kg / m ³ and preferably from 0.4 to 0.6 10 ³ kg / m ³ ; Foam density reduction in the range from 25% to 70%, preferably in the range from 33% to 55%; And Shore A hardness of less than 70, preferably less than 65; And when measured on a 6 mm thick non-foam injection molded test plate made of components (a)-(f) without blowing agent, it is understood that it exhibits a permanent compression ratio of 70%, preferably 55% or less, at 100 ° C. will be.

Another aspect of the invention provides the above components (a), (c) and (d); And components (b), (c) and / or (d) are each directly mixed and optionally mixed with one or more secondary components, which can be used to prepare the complete foamable composition and the foamed article produced thereby. It will be appreciated that it is formed by the pre-blend. This mixing must be carried out in a twin screw extruder.

If a pre-blend composition containing no blowing agent is produced, the pre-blend may additionally be mixed or rapidly mixed with the blowing agent to produce a masterbatch to be used in the actual foaming process.

If a pre-blend composition containing no blowing agents is produced, care must be taken to keep the temperature below the blowing agent decomposition temperature during the mixing process, unless full or partial foaming is desired during the pre-blend operation.

Another aspect of the invention is formed by a foamed flexible weather seal article made of the foamable composition described above.

An article of flexible foamed shape is preferably formed by a method comprising the following steps:

(i) components (a), (c) and (d), respectively, and optionally (f) and a blowing agent; And heating the mixture of the inventive foamable polymer composition prepared by mixing the pre-blends containing components (b), (c) and (d) and a blowing agent to a temperature above the melting point of the thermoplastic elastomer, and

(ii) evacuating the resulting mixture at ambient conditions.

The foaming process can be carried out with any known equipment for use in foaming thermoplastic elastomers.

Preferably, an extruder having an L / D of 20 or more is used, and more preferably an extruder having an L / D of 25 or more is used. The extruder should be able to achieve a melt pressure higher than 10 bar, preferably higher than 15 bar, prior to discharge. The temperature reached in advance in the extruder is above the melting point of the thermoplastic elastomer composition, preferably above 200 ° C.

If a chemical blowing agent is used, the temperature inside the extruder must at least reach the decomposition temperature of the chemical blowing agent.

The temperature of the melt must be precisely controlled at the end of the extruder, specifically just before exiting the die. The melting temperature in the extruder die is preferably lower than 20 ° C. and higher than the vicat softening temperature of component (c) used in the composition. Most preferably the melting temperature is 5-15 ° C. higher than the vicat softening temperature of component (c).

The invention will be elucidated by the following examples, which are not intended to limit the scope of the invention to these specific embodiments.

The basic ingredients used in the foamable compositions tested are listed in Table 1.

The effervescent compositions tested, shown in the various tables below, were prepared based on the processing conditions described above.

Experiment set 1:

The components in Table 2 were mixed directly in a high shear co-rotating twin screw extruder to produce thermoplastic elastomer compositions A to F (comparative experiment) and G (experiment according to the invention, but not preferred as dry-blend)-Table 3 Reference). Physical properties, hardness and permanent compression ratio (CS) were measured on 6 mm thick non-foamed injection molded plates.

In addition to these compositions, the foams and dry-mix with a ready-to-use masterbatch of nucleating agent, here HYDROCEROL BIH40 2wt%. This foamable pre-blend composition was used in a single screw extruder equipped with a tube die, having an outer diameter of 8 mm and a wall-die thickness of 0.8 mm, with an L / D of 20, The composition was heated to 200 ° C. to produce a foamed shape. The die pressure was maintained above 25 bar and the melt pressure was adjusted to approximately 164 ° C. Foam density was measured on foamed tube form.

Table 2 shows that the presence of both components (a) and (b) in the correct proportions is essential for obtaining good physical properties and good density reduction rates. Composition C is very similar to composition B and is expected to produce similar results. Therefore, the physical property of composition C was not measured.

Experiment set 2:

It has been found to be advantageous to prepare the composition in multiple stages rather than to mix all the components in one stage using a twin screw extruder. Thus, in the examples which follow, compositions B or C containing the components (a), (d) and (f) mentioned previously are incorporated into compositions D or containing the components (b), (d) and (f) Dry-mix with E; Additional component (c) was mixed and then mixed with 2 wt% of HYDROCEROL BIH 40. Pre-blends 1 to 5 were foamed according to the method described in Experimental Set 1 above.

Examples 1 to 5 are dry-mix compositions according to the invention. Compositions 1 and G contained exactly the same amount in the same ingredients, but were prepared by different steps of method. It is emphasized in the table that the two step method (dry mix of the various compositions for composition 1) shows a higher density reduction rate than composition G (produced in one step in a twin screw extruder). A dry-mix method is therefore preferred.

It should also be noted that Example 5 contains a mixture of MOPLEN HP 1078 and MOPLEN F30S. This polypropylene mixture had PI = 4.97 and showed good overall properties even though the MOPLEN F30S alone did not have the required PI (3.97).

Experiment set 3:

The following examples again illustrate the importance of various ingingients ratios.

In Table 4, new composition H is presented. This composition was prepared as described above with a co-rotating twin screw extruder. This composition comprises 100 parts Kraton MD6933ES; 200 parts PRIMOL 352; 50 parts MOPLEN HP502; And 0.2 parts of IRGANOX 1010 and PS800, respectively.

The foamable compositions were all prepared by dry-mix method with 2 wt% HYDROCEROL BIH 40.

Composition 7 showed that too low a concentration of component (c) results in insufficient density reduction. Composition 8 contained too much component (b) to have an acceptable permanent compression rate, and composition 11 was too hard because of the high concentration of component (c). Composition H appears to have a good balance of physical properties, but the shape of the foam obtained with this composition does not hold any surface. This open free bubble structure is obtained because pre-foaming occurs in the die of the extruder when the die pressure is too low. Compositions 9 and 10 are examples of correct component ratios that result in the correct balance of physical properties.

Experiment set 4:

As shown in this series of examples, the choice of linear crystalline polymers is important.

The foamable compositions were all prepared by dry-mix method with 2 wt% of HYDROCEROL BIH40.

Although HDPE shows better permanent compression values, such polyolefins are not suitable for the production of low density shapes.

Of the wide range of homopolypropylenes available on the market, only those having a large molecular weight distribution (indicated herein as polydispersity index PI) can be used.

Experiment set 5:

This series of experiments shows the importance of the presence of nucleating agents and blowing agents. The choice of blowing agent plays an important role in the aspect of the final foam shape. This foamable composition used in this experiment comprises 85 parts of Composition B; 10 parts of composition F; 5 parts MOPLEN HP502 and various amounts of nucleating and / or blowing agents were prepared by dry-mixing method. As a result, the composition possessed the following physical properties (before foaming): hardness 3s (Shore A), 58; Hardness 30s (Shore A), 53; CS 70 ° C., 72h = 48; CS 85 ° C. 72h = 50, and CS 100 ° C. 72h = 48.

The appearance of the foamed composition is shown in Table 7.

Experiment set 6:

This series of experiments shows the suitability of nitrogen as a blowing agent. The foamable compositions used in this experiment included 100 parts of (a) MD6933; 16 parts (b) G1657; 59 parts (c) HP1078; 158 parts (d) PRIIMOL 352 and 0.2 parts IRGANOX 1010 and PS800, respectively.

Prior to foaming, the composition had a hardness 3s (Shore A) 58 and a permanent compression rate (100 ° C., 24 h) 52%. 0.5% of HYDROCEROL BIH40 was used as a nucleating agent.

When no additional blowing agent was added, a foam density of 0.86 10 ³ kg / m ³ was obtained (density reduction rate 4%; smooth appearance surface). With the addition of 1.5% HYDROCEROL BIH40 (now also acting as a blowing agent), a foam density of 0.64 10 ³ kg / m ³ (29% density reduction, smooth appearance surface) was seen. When 0.06% nitrogen gas was attached, a foam density of 0.58 10 ³ kg / m ³ was obtained (density reduction rate 36%, smooth appearance surface).

For these foams, the absorbance according to test method ASTM 1056 was measured. The first foam (if no foaming agent was added) had a 0% absorption rate, which is an indication of 100% closed free bubbles. When 1.5% of additional HYDROCEROL BIH40 was added, the absorption rate changed to 9%. When nitrogen gas was added as the blowing agent, the water absorption changed to 0.2%. Preferably, the water absorption is 10% or less.

Claims (15)

(a) 100 parts by weight of one or more optionally hydrogenated block copolymers having a resinous block A which is at least two mostly non-hydrogenated polymerized monovinylarenes and optionally a hydrogenated elastomer block B Most of the block B prior to hydrogenation is polymerized conjugated dienes or dienes, the block copolymers have a total apparent molecular weight of at least 250 kg / mol, and polymerized at a true molecular weight of at least 18 kg / mol. Monovinylarene block), (b) at least two mostly non-hydrogenated polymerized monovinylarenes and optionally hydrogenated one or more block copolymers 5 to 50 having optionally hydrogenated elastomer block B ' By weight (wherein the block B 'prior to hydrogenation was derived from polymerized conjugated dienes or dienes which are the main components that can be mixed with up to 25 wt% aromatic vinyl, the block copolymers ranging from 50 to 180 kg / mol). While having a total apparent molecular weight, Resin Block A 'shows an actual molecular weight ranging from 3 to 20 kg / mol), (c) 25 to 80 parts by weight of a linear crystalline polymer containing propylene as a main component having a bicat softening temperature in the range of 130 ° C to 180 ° C, an MFR of 0.5 to 30 dg / min and a polydispersity index of at least 4.5, (d) 100 to 250 parts by weight of a softener that is compatible with blocks B and B ', (e) 0.01 to 3 wt% of the endothermic group's chemical solid nucleating agent mixed with a blowing agent, based on the weight of the primary components (a) to (e), and optionally (f) flexible, heat resistant, containing at least one secondary component selected from PPO resins, antioxidants, UV-stabilizers, flame retardants, interfacial modifiers and inorganic fillers that are compatible with the block copolymer component (a) A foamable composition, useful for making foamed thermoplastic elastomeric articles. delete delete delete delete delete delete delete delete delete A foamed article derived from the composition of claim 1. Components (a), (c) and (d); Components (b), and (c); Or a pre-blend for producing the foamable composition according to claim 1 containing one of components (b), (c), and (d). The foamable composition of claim 1 wherein the block copolymer has a total apparent molecular weight of at least 350 kg / mol. The foamable composition of claim 1 containing 15 to 40 parts by weight of at least one hydrogenated block copolymer. The foamable composition of claim 1 wherein the resinous block A ′ has an actual molecular weight in the range of 5-15 kg / mol.