WO2008064857A1

WO2008064857A1 - Block-copolymer elastomer

Info

Publication number: WO2008064857A1
Application number: PCT/EP2007/010278
Authority: WO
Inventors: Reinoud Jaap Gaymans; Debby Husken; Sander Rogier Reijerkerk
Original assignee: Stichting Dutch Polymer Institute
Current assignee: Stichting Dutch Polymer Institute
Priority date: 2006-12-01
Filing date: 2007-11-27
Publication date: 2008-06-05
Anticipated expiration: 2009-06-01

Abstract

The invention relates to block-copolymer elastomer comprising soft blocks and hard blocks, wherein the hard blocks consist of repeating units comprising ester, amide, imide, and/or urethane groups, and wherein the block-copolymer elastomer comprises soft end-segments.

Description

BLOCK-COPOLYMER ELASTOMER

The invention relates to a block-copolymer elastomer, more particular to block-copolymer elastomer comprising alternating soft blocks and hard blocks and wherein the hard blocks consist of repeating units comprising ester (E), amide (A), imide (I), and/or urethane (U) groups. Such block-copolymer elastomers are also known as thermoplastic elastomers (TPE), each of which are known, respectively, as TPE-E, TPE-A, TPE-I and TPE-U elastomers.

The invention relates in particular to thermoplastic elastomers which have a good gas or vapor permeability. Applications which require a good transport of volatile substances in the form of vapor or gas are, for example, plastic sheetings used in buildings and constructions, smokable films used sausage casings, food packaging, industrial applications such as membranes for CO₂ recovery, and medical and sanitary applications. Smokable films and TPE-elastomers used in the films are described in US-6,764,753-B2. The known TPE-elastomers from US-6,764,753-B2 are block copolyetherether elastomers have a multiplicity of recurring short chain ester units and long chain ether units joined head-to-tail through ester linkages, said long chain ether units comprise moieties derived from a poly(alkylene oxide) glycol. Said short-chain ester units being represented by the formula [-ODO-C(=O)RC(=O)-] wherein R is a divalent radical remaining after removal of carboxyl groups from a dicarboxylic acid having a molecular weight less than about 300; and D is a divalent radical remaining after removal of hydroxyl groups from a diol having a molecular weight less than about 250; and wherein said copolyetherester(s) contain from about 25 to about 80 weight percent short-chain ester units. The said long-chain ether units being represented by the formula [-OGO-C(=O)RC(=O)-] and G is a divalent radical remaining after the removal of terminal hydroxyl groups from a poly(alkylene oxide)glycol having an average molecular weight of about 400-3500, wherein the amount of ethylene oxide groups incorporated in said one or more copolyetheresters by the poly(alkylene oxide)glycol is from about 20 to about 68 weight percent, preferably from about 25 to about 68 weight percent, based upon the total weight of the copolyetherester(s).

In the smokable films of US-6,764,753-B2 the TPE-elastomer is blended with an aliphatic polyamide. The problem according to US-6,764,753-B2 is that aliphatic polyamide has too low a vapor permeability, in particular at high temprrature, and this problem is claimed to be solved by blending the aliphatic polyamide with the known the TPE-elastomer.

The need for TPE-E, TPE-A, TPE-I and TPE-U elastomers with high gas and/or vapor permeability is described in various other publications as well. For example, US patent US 5,506,204 describes water vapor permeable films of polymeric material of thermoplastic elastomer type based on polyetherester amide, and preferably on polyether block amides, and articles comprising a film of this kind and capable, in particular, of coming into contact with the human body.

US patent US 5,888,597 describes a packaging comprising thermoplastic film based on a polymer containing polyamide blocks and polyether blocks, said polymer being permeable to water vapor, to ethylene, to CO2, and to oxygen, such that the permeability to CO2 is very much greater than the permeability to oxygen. The packaging film said to be particular useful for making sachets in order to conserve fresh fruits, vegetables or meat. Furthermore, gas transport properties of poly (ether-b-amide) segmented block copolymers are described by V.I. Bondar et al in J. Polym. Sci. part B. Polymer Phys. 2000 (38), page 2051 -2062. Gas permeation of poly(amide-6-b- ethyleene oxide) copolymer are describved by J. H. Kim in J. Membrane Science, 190 (2001 ) 179-193, whereas gas permeation properties of poly(ethylene oxide ) poly(butylene terephthalate) block copolymers are described by by S.J. Metz et al. in Macromolecules 2004, 37, 4590-4597.

Thus, it can be concluded that there exists a large interest in block- copolymer elastomers with a high gas and/or vapor permeability, there remains a need to further improve the gas and/or vapor permeability of such block-copolymer elastomers.

Accordingly, the aim of the present invention is to provide a measure to improve the gas and/or vapor permeability properties of block-copolymer elastomer and to provide a block-copolymer elastomer having improved gas and/or vapor permeability properties. This aim has been achieved with the block-copolymer elastomer according to the invention wherein the block-copolymer elastomer comprises soft end- segments.

The effect of the soft end-segments is that the block-copolymer elastomer comprising said groups has a higher gas permeability compared to the corresponding block-copolymer elastomer not comprising such groups. This effect has been observed in various gas permeability measurements performed such corresponding materials. Herein the oxygen (O₂), hydrogen (H₂), methane (CH₄), nitrogen (N₂), helium (He) and carbon dioxide (CO₂) permeability was measured.

Within the context of the present invention soft blocks are defined as polymeric parts of the block copolymer elastomer which constitute a soft amorphous phase. In line herewith the hard blocks are defined as polymeric parts of the block copolymer elastomer which constitute a hard phase. The hard phase can be an amorphous phase having a high glass transition temperature and/or a crystalline phase having a high melting temperature. Typically the soft phase has a glass transition temperature that is significantly lower than the glass transition temperature, respectively the melting temperature of the hard phase.

It is further emphasized, without changing the content of the invention or the intention thereof, that the soft end-segments comprised by the block-copolymer elastomer are distinctly different from the soft segments comprised by the block- copolymer elastomer which are alternated at both sides with hard blocks. The soft end- segments are linked to the other segments in the block-copolymer elastomer only by one such hard block. The soft end segments thus form the polymeric end parts of the block copolyester elastomer. These soft end-segments, or end parts, or even better polymer end parts, form an amorphous phase, either as a combined soft amorphous phase together with the soft blocks alternated by the hard blocks, or as a separate soft amorphous phase next to amorphous phase of the soft blocks alternated by the hard blocks.

In this respect it is clear that soft end segments in the block- copolymer elastomer according to the invention are different from soft end segments within a soft block itself, such as in a polyethylene oxide - polypropylene oxide block copolymer or in a polypropylene oxide polymer end-capped with ethylene oxide groups.

It is further noted that polyesters modified with poly(ethylene glycol) end groups are known. For example, Shulze et al, describe in J. Appl. Polym. Sc, (1997), 64(3), 527-537 (ISSN: 0021 -8995) unsaturated polyesters modified with polyethylene glycol) end groups dissolved in styrene, which modification is applied to influence the solution behaviour of the unsaturated polyesters in styrene. It is noted that these styrene dissolved unsaturated polyesters are curable or so-called thermoset resins, not thermoplastic elastomers as according to the present invention.

Preferably, the glass transition temperature of the soft phase in the block-copolymer elastomer according to the invention is at most 20^QC, more preferably - A -

at most O⁹C, -20⁹C, -30⁹C or even at most -40⁹C and may be as low as -60 ⁹C or even lower.

Also preferably, the glass transition temperature of the amorphous hard phase, or where applicable the melting temperature of the crystalline phase is at least 150⁹C, 180⁹C, 200⁹C or even at least 225⁹C, and may be as high as 280 ⁹C or even higher.

In line with the definitions here above, soft end-segments are herein defined as polymeric end parts of the block copolymer elastomer, which end parts form an amorphous phase. These end-groups can either constitute a separate soft amorphous phase in the block copolymer elastomer, or form a single soft amorphous phase together with the soft blocks which alternated by the hard blockss. Where applicable, the separate soft amorphous phase constituted by the soft end-segments also preferably has a glass transition temperature of at most 20⁹C, more preferably at most O⁹C, -20⁹C₁ -30⁹C or even at most -40⁹C and may be as low as -60 ⁹C or even lower.

There are various ways to make block copolymer elastomers with soft end-segments. Soft end-segments can be created by using different precursor materials for the soft end-segments. These so-called "soft end-segment precursor materials" can be monofunctional, i.e. having one reactive group, difunctional with two reactive groups having different reactivities, and/or polyfunctional with a plurality of reactive groups having different reactivities, and/or by using di- or polyfunctional precursor materials having two, respectively a plurality of reactive groups having the same reactivity in molar excess compared to molar amount of the hard blocks or precursors thereof. With a reactive group comprised by the soft segment precursor material is herein understood a functional group that is capable of reacting with a functional group comprised by hard block precursor materials thereby forming a covalent bond between the soft segment and the hard blocks.

Suitably, the functional groups comprised the precursor materials for the soft end-segments comprise one or more of the following: hydroxyl groups, carboxyl groups or an ester derivative thereof, amine and / or isocyanate groups.

Preferably the soft end-segment is derived from a monofunctional precursor material. The advantage is that the structure of the elastomer is better controlled and a better combination of mechanical properties and gas permeability properties is obtained. Suitable soft end-segments, that may be comprised by the elastomer according to the invention, are soft end-segments derived from polyethers, polyesters, polycarbonates, and/or polysiloxanes.

Preferably, the soft end-segments are derived from polyethers precursoer materials, such as poly(ethyleneoxide) ether, poly(propylene oxide) ether, or poly(tetramethylene oxide) ether, and mixtures and copolymers thereof. In other words, these preferred soft end-segments are polyether end-segments. More preferably, the polyether from which the soft end-segments are derived comprises ether units derived from ethylene-oxide, more preferably, the polyether is a poly(ethyleneoxide) ether.

More preferably, the polyether end-segments are derived from a monofunctional polyether, i.e. a polyether derived from a polyether glycol in which one of the two hydroxyl groups is end-capped. Suitably, the polyether is a polyether glycol end-capped with an alkyl moiety, such as a methyl, an ethyl or a butyl group, thus forming an alkoxy end group. Preferably, the polyether is a poly(ethyleneoxide) ether end-capped with a methyl group.

The soft end-segments, and in particular the soft end-segments derived from a monofunctional polyether, can have a number average molecular weight (Mn) varying over a large range. Suitably the Mn is in the range of 200-3000, but the Mn can also be higher, for example up to 5000 or even 6000 in case of polyether mono functional alcohols, or lower than this range. Preferably, the Mn is in the range of 300- 2000, more preferably 400-1000.

Preferably, the elastomer according to the invention has a total number of end-segments of which the soft end-segments make up for at least 20%. More preferably, the number of soft end-segments in the elastomer according to the invention is at least 50%, more preferably at least 60% and most preferably 75-100%, relative to the total number of end-segments in the elastomer. The advantage of a higher percentage of the end-segments being soft end-segments is that the gas permeability of the elastomer is further increased. The block-copolymer elastomer according to the invention comprises soft blocks alternated with hard blocks. These soft blocks can be derived from different precursor materials, which are at least two-functional. Suitably, the soft blocks are derived from polyethers, polyesters, polycarbonates, and/or polysiloxanes. Also suitably the soft blocks are derived from materials that have, or can be modified with functional groups being reactive with functional groups comprised by precursor materials from which the hard blocks are derived. Suitably, the functional groups comprised the precursor materials for the soft blocks comprise hydroxyl groups, carboxylic acid groups or ester derivatives thereof, and / or amine groups. The precursor materials for the hard blocks suitably comprise hydroxyl groups, carboxylic acid groups or an ester derivative thereof, amine and / or isocyanate groups as the functional groups.

Suitably, the soft blocks in the elastomer according to the invention are derived from di-functional polymer, optionally combined with thfunctional and/or higher functional polymers. As the concentration of end-segments increases, the molecular weight decreases and with that the tensile properties. High molecular weight copolymers with a high soft end-segment concentration can be obtained by adding some polyfunctional components, forming branched structures, which copolymers still have good processability and good mechanical properties. A suitable branching agent, that can be used in combination with hydroxyl and/or amine functional soft block precursor materials, is for example, trimethyl ester of trimesic acid (TMTM), a trifucntional carboxylate methyl ester. The hard segment can also be branched with trifunctional building blocks such as TMTM or trimethylol propane (TMP).

Preferably, the soft blocks are derived from di-functional and optionally trifunctional and/or higher functional hydroxyl functional polyethers. The di- functional hydroxyl functional polyethers are also known as polyether glycols.

Examples of suitable polyether soft blocks are soft blocks derived from poly(ethyleneoxide) glycol, poly(propylene oxide) glycol, or poly(tetramethylene oxide) glycol, and mixtures and copolymers thereof. A suitable polyether copolymer is, for example, polypropylene oxide) glycol end-capped with poly(ethyleneoxide) moieties.

Suitably, the soft blocks in the elastomer according to the invention suitably have a number average molecular weight (Mn) in the range of 500-10,000, although the Mn may also be higher than 10,000 or lower than 500. Preferably the Mn is in the range of 800-5000, more preferably, 1000-3000.

Suitably, the soft blocks in the elastomer according to the invention are derived from polyether diols having a number average molecular weight (Mn) in the range of 500-5,000, although the Mn may also be higher than 5000 or lower than 500. Preferably the Mn is in the range of 800-3000, more preferably, 1000-2000. For the polyether soft blocks having a Mn higher than 5000, or even higher than 3000, suitably polyether diols having a number average molecular weight (Mn) in the range of 500-3000, more preferably 1000-2000, chain extended with di carboxylic ester moieties are used. Suitably, the chain extended moiety can be derived from dimethyl terephthalate (DMT) or dimethyl isophthalate (DMI), by reacting the polyether diol with an adequate amount of DMT and or DMI. The di carboxylic ester chain extended polyether diols are suitably used in TPE-A and TPE-I elastomers. The soft blocks and soft end-segments can be present in a total amount varying over a large range. Preferably, the total amount of soft blocks and soft end-segments incorporated in the elastomer is 20-90 wt.%, more preferably 30-80 wt.%, still more preferably 40-70 wt.%, relative to the total weight of the elastomer.

Very suitably the total amount of soft blocks and soft end-segments is in range of 40-60 wt.%, relative to the total weight of the elastomer.

The soft end-segments, and in particular soft end-segments derived from a monofunctional polyether, can be present in an amount varying over a large range. Suitably this amount is at least 2 wt.%, and as high or even higher than 30 wt.%, preferably in the range of 5-25 wt.% and more preferably in the range of 10-20 wt.%. Herein the weight percentage (wt.%) is relative to the total weight of the elastomer.

The hard blocks in the block-copolymer elastomer according to the invention consists of repeating units comprising ester, amide, imide, and/or urethane groups. Preferably, the repeating units comprise amide groups.

Repeating units comprising ester groups can be derived from hydroxyl functional carboxylic acids, or ester derivatives thereof, and/or from dicarboxylic acids, and/or an and diols. Suitably the hydroxyl functional carboxylic acid, comprises or even is an aromatic hydroxyl functional carboxylic acid. Also suitably, at least one of the dicarboxylic acid and diol comprises an aromatic component.

Preferably, the repeating units comprising ester groups are derived from from aromatic dicarboxylic acids, or ester derivatives thereof, and short chain aliphatic diols. Suitable aromatic dicarboxylic acids are terephthalic acid, isophthalic acid, naphthalene dicarboxylic acid and bis(phenylcarboxylic acid), and combinations thereof. Preferably, the aromatic dicarboxylic acid comprises terephthalic acid. Short chain aliphatic diols are herein understood to be aliphatic diols comprising 2-10 C atoms. Examples of suitable short chain aliphatic diols are ethanediol, 1 ,2-propane diol, 1 ,3-propane diol, 1 ,2-butane diol, 1 ,4-butane diol, and 1 ,6-hexanediol. Preferably the short chain aliphatic diol comprises 1 ,4-butane diol. Most preferably, the repeating units comprising ester groups comprise, or even consist of butyleneterephthalate units.

Repeating units comprising urethane groups can be derived from diisocyanates and diols, which can be either aliphatic or aromatic diisocyanates, and aliphatic or aromatic diols, or any combination thereof.

Suitable aromatic diisocyanates are 2,4-toluene diisocyanate (TDI) and 4,4-diphenyl-methane diisocyanate (MDI), and combinations thereof. Suitable aliphatic diisocyanates are 1 ,6-hexane diisocyanate (HDI), isophoron diisocyanate (IPDI), and 1 ,4-benzene-bis(isoprolyisocyanate) (TMXDI). Suitable aliphatic diols are short chain diols. Short chain aliphatic diols and preferred embodiments thereof are herein understood to be the same as described here above. Also 1 ,6-hexanediol is here a preferred short chain aliphatic diol. A suitable aromatic diol is bisphenol (BPA).

Preferably, at least one of the diisocyanate and diol comprises an aromatic component. More preferably, the repeating units comprising urethane groups are derived from an aromatic diisocyanate and aromatic diol. Most preferably, the repeating units comprising urethane groups comprise, or even consist of units derived from TDI and/or MDI in combination with BPA.

Repeating units comprising imide groups can be derived from diamines, and dianhydrides. Suitably diamines from which the diimides may be derived are 4,4-diamino diphenyl disolfone and 4,4-oxydianiline. Suitably dianhydrides from which the diimides may be derived are pyromellitic anhydride and 3,3,4,4-biphenyl tetracarboxylic dianhydride.

Repeating units comprising amide groups can be derived from amine functional carboxylic acids, or cyclic lactam thereof, and/or from dicarboxylic acids, and/or diamines. A suitable lactam derivative of an amine functional carboxylic acid is caprolactam. The dicarboxylic acid can comprise aromatic as well as aliphatic dicarboxylic acids. Also the diamine can comprise aromatic as well as aliphatic diamines. A suitable combination of an aliphatic dicarboxylic acid and an aliphatic diamine is the combination of adipic acid and 1 ,6 hexane diamine. Hard blocks consisting of repeating units of these components can be described as polyamide 6,6 oligomers. Suitably, at least one of the dicarboxylic acid and diamine comprises an aromatic component. Suitable aromatic dicarboxylic acids are terephthalic acid and isophthalic acid. Suitable diamines are short chain aliphatic diamines, which are herein understood to be aliphatic diamines comprising 2-12 C atoms. Examples of suitable short chain aliphatic diamines are 1 ,4-butane diamine, 1 ,5-pentane diol, 1 ,5- hexanediamine, 1 ,6-diamine, 1 ,8 octane diamine, 1 ,8-nonanedimane, 1 ,9- nonanediamine, 1 ,10-decanediamine, and 1 ,12-octanediamine. Preferably the short chain aliphatic diamine comprises 1 ,4-butane dimine and/or 1 ,6-diamine.

Preferably the repeating units comprising amide groups are derived from terephthalic acid and 1 ,6-diamine. Hard blocks consisting of repeating units of these components can be described as polyamide 6,T oligomers.

Preferably, the hard blocks in the elastomer according to the invention comprise repeating units comprising amide groups.

More preferably, the hard segments comprise repeating units with in total 2-6 amide groups, and in particular 4 amide groups, per hard segment. The advantage thereof is that the elastomer shows a better combination of mechanical properties and gas permeability properties.

Also preferably, at least 70 mole %, and even more preferably 80-100 mol% of the hard segments are uniform in length, i.e. have the same number of repeating units. Also here the advantage is that the elastomer shows a better combination of mechanical properties and gas permeability properties.

The hard blocks in the block-copolymer elastomer according to the invention are suitably present in an amount of 10-90 wt.%, relative to the total weight of the elastomer. Preferably the said amount is in the range of 20-80, more preferably 30- 70 wt.%, relative to the total weight of the elastomer. Very suitably the amount of hard blocks is in range of 40-60 wt.%, relative to the total weight of the elastomer.

In a preferred embodiment, the block-copolymer elastomer of the invention consists of (a) 10-90 wt.% of hard blocks and (b) 10-90 wt.% of soft blocks and soft-end segments, wherein the sum of (a) and (b) amounts to 100 wt.%, of which (c) 5-25 wt.%, relative to the total weight of the elastomer, consists of soft end groups,

In a more preferred embodiment, the block-copolymer elastomer of the invention consists of (a) 20-80 wt.% of hard blocks comprising repeating units comprising amide groups and (b) 20-80 wt.% of soft blocks derived from polyether polyols and soft-end segments derived from monofunctional polyethers, wherein the sum of (a) and (b) amounts to 100 wt.% and of which (c) 5-25 wt.%, relative to the total weight of the elastomer, consists of the soft end groups derived from the monofunctional polyethers.

The block-copolymer elastomer according to the invention can be prepared by various methods. Suitable methods for preparing the elastomer incude melt polymerization processes and solution polymerization processes. Block-copolymer elastomers according to the invention with polyester hard segments and polyether soft blocks and polyether soft end groups are suitably prepared by a melt process. For such a process, melt processes used for preparing block- copolymer elastomers known in the art can be used. Such processes are described, for example, in the prior art US-6,764,753-B2, cited above.

Block-copolymer elastomers according to the invention with polyamide hard segments and polyether soft blocks and polyether soft end groups are suitably prepared by a solvent process. For such a process, solvent processes used for preparing block- copolymer elastomers known in the art can be used. Such processes are described, for example, in the prior art WO 03/070807.

Block-copolymer elastomers with polyamide hard segments with defined length can favorably be prepared by a solvent free process, as far as it regards the preparation itself. The preparation of the precursors of the hard blocks with defined length is suitably done in a solvent. Such a process is described by et al in Polymer, 2003, 4, pages 7043-7053.

Once the precursors of the hard blocks have been prepared and isolated, the block-copolymer elastomers with polyamide hard segments, soft blocks and soft end-groups can be prepared by a process comprising the steps of mixing the (A) precursor of the polyamide hard segment and (B) the precursor materials for the soft end-segments and the soft blocks in the desired ratio, and heating the mixture to a reaction temperature which is above the melting temperature of the precursor of the polyamide hard segment, whereby a reaction starts between (A) and (B). This reaction is suitably carried out in the presence of a catalyst.

The invention also relates to the use of the block-copolymer elastomers with the soft end groups for making products and articles, as well as to products and articles made of these block-copolymer elastomers. Examples of suitable products and articles are films comprising, or consisting of the block-copolymer elastomers with the soft end groups according to the invention. The invention also relates to the use of such films as plastic sheetings in buildings and constructions, as sausage casing, in particular for as smokable film in sausage casings, in products intended for use in contact with the human body, as well as in medical and sanitary products for non-skin contact applications, as packaging film, in particular for making sachets for fresh fruits, vegetables or meat conservation.

The invention is further illustrated with the following Example and Comparative Experiments. Synthesis of T6T6T-dimethyl.

T6T6T-di methyl was prepared as described by J. Krijgsman, D. Husken and R.J. Gaymans in RJ. , Polymer 2003, 44, p. 7043-7053. First, 6T6- diamine was made by the reaction between an excess of HMDA and DMT (8:1 molar ratio). A mixture of HMDA (1.2 mol, 139 g) and DMT (0.15 mol, 29 g) was heated to 80 ⁹C in a 1 L stirred round bottomed flask with nitrogen inlet and a reflux condensor. After approximately 1 h the 6T6-diamine started to precipitate. After 4 h -500 mL toluene was added to the mixture to improve stirring. The product was collected by filtration and washed twice with warm toluene (80 ⁹C) to remove the excess of HMDA. Finally, the product was washed with diethyl ether and dried at room temperature. The product contained impurities (mainly 6T6T6) as analysed by ¹H NMR ^[1). After recrystallisation from n-butyl acetate at 110 ⁹C (15 g/L) the purity of the product became 98%.

Second, a mixture of 6T6-diamine (0.02 mol, 7.2 g) and MPT (0.08 mol, 20.5 g) was dissolved in 400 mL NMP in a 1 L stirred round bottomed flask with nitrogen inlet and a reflux condensor. The mixture was heated to 120 ^QC for 16 h. After cooling, the precipitated product was collected by filtration and washed with NMP, warm toluene (80 ⁹C) and diethyl ether. The purity of the final product was >95% as analysed by ¹H NMR.

Comparative Experiments A and B: Synthesis of PEOv-T6T6T block copolymers.

Block copolymers consisting of poly(ethylene oxide)ether soft blocks and polyamide hard blocks of defined length, being denoted as PEO_X-T6T6T block copolymers, were synthesized by a polycondensation reaction using poly(ethylene oxide)glycol and T6T6T-dimethyl. In the notation PEO_X-T6T6T x represents the number average molecular weight of the PEO segment. The synthesis of PEdooo- T6T6T (Comparative Experiments A) is given as an example.

The reaction was carried out in a 250 mL stainless steel vessel equipped with a magnetic stirrer and nitrogen inlet. The vessel contained T6T6T- dimethyl (10 mmol, 6.86 g), PEO₁₀₀₀ (10 mmol, 10.0 g), Irganox 1330 (0.10 g), 50 mL NMP and catalyst solution (1.0 mL of 0.05 M Ti-(Z-(OC₃Hr)₄) in /π-xylene). The reaction mixture was heated to 180 ⁰C under a nitrogen flow in an oil bath. After 30 min the temperature was increased to 250 ⁰C in 1 h. After 2 h at 250 °C the pressure was slowly reduced (P < 21 mbar) to remove all NMP. Than, the pressure, was further reduced (P < 1 mbar) to allow melt polycondensation for 1 h. The polymer was cooled to room temperature while maintaining the vacuum. Liquid nitrogen was added to the reaction vessel to isolate the polymer. Before analysis, the polymer was dried in a vacuum oven at 50 ⁰C for 24 h.

PEO₂₀₀₀-T6T6T (Comparative Experiments B) was prepared in the same way as described for Comparative Experiments A, but using PEO₂₀₀₀ in stead of PEO1000 in the same molar amount.

Example I: Synthesis of mPEOWPEOinnn/TMTM-T6T6T block copolymer.

A block copolymer comprising poly(ethylene oxide)ether soft blocks, poly(ethylene oxide)ether soft end-segments and polyamide hard blocks of defined length, being denoted as mPE0₅₅o/PEOiooo/TMTM-T6T6T copolymer, was synthesised by a polycondensation reaction. To compensate for the reduction in molecular weight trifunctional trimethyl trimesate (TMTM) monomer was used. The reactants for the polymerisation were mPE0₅₅o (4 mmol, 2.2 g), PEO₁₀₀O (11 -1 mmol, 11.1 g), T6T6T- dimethyl (10.1 mmol, 6.93 g) and TMTM (2 mmol, 0.50 g), 25 mL NMP and catalyst solution (2.6 mL of 0.05 M Ti-(/-(OC₃H₇)₄) in m-xylene). The polymerisation was comparable to the method described for the PE0_1θoo-T6T6T copolymer described here above.

Film preparation Films of approximately 100 μm thickness were prepared from dried copolymers using a Laufer press. The temperature was set approximately 40 ^QC above the melting temperature of the copolymer. First, air was removed from the polymer in the mould by quickly pressurizing the samples followed by depressurizing. This procedure was repeated three times bedfore actually pressing the samples at about 8.5 MPa for 5 minutes. Subsequently, the samples were cooled to room temperature while maintaining the pressure. To prevent sticking of the polymer onto the metal mould, glass fibre reinforced PTFE sheets were used (Bentech type B105).

Gas Permeation Measurements The single gas permeation properties of the copolymer elastomers of

Example I and Comparative Experiments A and B were determined with oxygen (O₂), hydrogen (H₂), methane (CH₄), nitrogen (N₂), helium (He) and carbon dioxide (CO₂) at a temperature of 35 ^QC and a pressure of 4 bar. Single gas permeability values were calculated from the steady state pressure increase in time in a calibrated cvolume at the permeate side, following the constant volume pressure method as described in detail by A. Bos et al in J. Polym. Sci., Polym. Pys. Ed. 36, p. 1547-1556. The gas permeabilities were expressed in Barrer [= 1.10 ¹⁰ cm³ (STP) cm / cm².s.cmHg].

Water absorption The equilibrium water absorption (WA) was measured using pieces of injection moulded polymer bars. The samples were placed above the water level in a desiccator comprising demineralised water and kept in this environment with 100% RH at room temperature for 4 wks. The WA was defined as the weight gain (in wt.%) of the polymer, relative to the initial weight of the polymer sample. The data for the composition and water absorption for the copolymer elastomers of Example I and Comparative Experiments A and B have been collected in Table I, whereas the gas permeability data are presented in Table 2.

Table 1. Composition and water absorption for the copolymer elastomers of Example I and Comparative Experiments A and B.

Table 2 Gas permeabilities at 35^QC [units: Barrer] for the copolymer elastomers of Example I and Comparative Experiments A and B.

These results show that with the copolymer of Example I comprising soft end-blocks according to the invention a large increase in gas permeability is achieved for all gases tested. At the same time a limited increase in water absorption is observed for Example I compared to Comparative Experiment A. It is noted that the total amount of poly(ethylenene oxide) ether groups in Example I is about 6 wt.% higher than in Comparative Experiment A. In Comparative Experiment B, a similar increase in CO2 gas permeability is achieved by extension of the chain length of the polyethylene glycol based soft blocks. For this increase the total content of poly(ethylenene oxide) ether groups had to be increased with about 15 wt.% compared to Comparative Experiment A. This is much more than in Example I. Furthermore, Comparative Experiment B shows much higher water absorption while the gas permeability for the gases other than CO2 are much lower than for Example I. This clearly illustrates that the measure of the soft end-blocks according to the invention is much more effective for increasing the gas permeability and has the accompanying advantage that the increase in water absorption can be kept limited.

Claims

1. Block-copolymer elastomer comprising soft blocks and hard blocks, the hard blocks consisting of repeating units comprising ester, amide, imide, and/or urethane groups, characterized in that the block-copolymer elastomer comprises soft end-segments.

2. Block-copolymer elastomer according to claim 1 , wherein the soft end- segments are polyether end-segments.

3. Block-copolymer elastomer according to claim 2, wherein polyether end- segments are derived from a monofunctional polyether.

4. Block-copolymer elastomer according to claim 3, wherein the monofunctional polyether is a poly(ethyle oxide) end-capped with a methoxy end-group.

5. Block-copolymer elastomer according to any of claims 1 -4, wherein the soft end-segments have a number average molecular weight Mn in the range of 200-3000.

6. Block-copolymer elastomer according to any of claims 1 -5, wherein the soft end-segments are present in an amount of 2-25 wt.% relative to the total weight of the elastomer.

7. Block-copolymer elastomer according to any of claims 1 -6, wherein the soft blocks are derived from di-and/or trifunctional polyethers with a number average molecular weight Mn in the range of 500-5000.

8. Block-copolymer elastomer according to any of claims 1 -7, wherein the hard blocks consist of repeating units comprising amide groups.

9. Use of the block-copolymer elastomers with the soft end groups according to any of claims 1 -8 for making products and articles.

10. Products and articles comprising or consisting of the block-copolymer elastomers with the soft end groups according to any of the claims 1 -9.

1 1. Use of a film comprising or consisting of the block-copolymer elastomers with the soft end groups according to any of claims 1 -9 as plastic sheetings in buildings and constructions, as sausage casing, in products intended for use in contact with the human body, or as a food packaging film.