Hollow body comprising peba in the outer layer

Abstract

The invention relates to a multi-layer hollow body suitable for storing or transporting an aqueous medium, the hollow body having a polyether block amide-containing outer layer.

Description

[0001] Hollow body with PEBA in the outer layer

[0002] In recent years, increasing demands have been placed on the long-term durability of automotive coolant lines, as well as on the high operating temperatures of the line system. Polyamides provide the necessary good mechanical properties, including the required burst pressure resistance at elevated temperatures above 100 °C.

[0003] A mixture of water and antifreeze (usually ethylene glycol) is used as the coolant, although glycols with reduced functionality, such as monoethylene glycol, can also be used. Demineralized or distilled water is often used. Depending on the application, special additives are also used to provide additional corrosion and rust protection. Such coolants have a higher boiling point.

[0004] Pure polyolefin cables exhibit insufficient burst pressure strength in this elevated temperature range; resistance to grease and oil is also limited. However, mono-polyamide cables do not exhibit sufficient hydrolysis resistance; their swelling behavior in coolants also reduces their mechanical strength.

[0005] For this reason, multilayer coolant lines are known in the prior art, which have a polyolefin inner layer and a polyamide outer layer.

[0006] EP0436923A describes partially corrugated multilayer coolant lines consisting of a polyolefin inner layer and a polyamide outer layer, which are optionally bonded together via an adhesion promoter layer.

[0007] The weak point of such pipes is the polyolefin inner layer. It has been shown that polypropylene, in particular, becomes brittle relatively quickly under operating conditions. One cause of this can be the oxygen dissolved in the cooling system or the oxygen diffusing from the outside through the polymer layer(s).

[0008] A common consequence of embrittlement of the inner layer is the formation of microcracks, allowing coolant to penetrate the polyamide outer layer. The resulting hydrolysis leads to a significant reduction in burst strength and ultimately to pipe failure.

[0009] EP1771298A1 describes two- or three-layer pipes as coolant lines. These pipes have a polyolefin inner layer and a polyamide outer layer. The outer layer is composed of aliphatic homopolyamides, preferably PA 6.12. Such pipes exhibit no fractures in the impact test (SAE J2260) after 1000 hours of contact with glycol / water (1 / 1 volume mixture) at 130°C, although they exhibit a steady decrease in elasticity (elongation at break).

[0010] The object of the present invention is therefore to overcome at least one disadvantage of the prior art.

[0011] Surprisingly, it was found that the service life of coolant lines can be increased by using an outer layer containing polyether block amide.

[0012] The invention relates to a multilayer hollow body suitable for storing or transporting an aqueous medium, wherein the hollow body has an outer layer containing polyether block amide.

[0013] A further object of the invention is the use of the hollow bodies for storing or transporting an aqueous medium.

[0014] The aqueous medium preferably contains alcohol. The alcohol has one or more hydroxyl groups, preferably two hydroxyl groups, more preferably two terminal hydroxyl groups. Furthermore, the alcohol is preferably a glycol, particularly preferably ethylene glycol. In addition to alcohol, the aqueous medium optionally contains further additives. The aqueous medium is preferably homogeneous over a wide temperature range, i.e., it is single-phase, containing only one liquid phase. The single-phase nature persists throughout the entire applied temperature range.

[0015] The temperature range is preferably -50°C to +150°C, more preferably -30 to 130°C, particularly preferably -15° to 95°C.

[0016] The additional additives may also contain a solid that partially separates from the solution at low temperatures and redissolves at higher temperatures. For this purpose, the additives must also contain detergents that prevent clumping during cold-induced separation.

[0017] The aqueous medium is preferably a coolant. Thus, the claimed multilayer hollow body is designed for storing or transporting a coolant. More preferably, the multilayer hollow body is a coolant line.

[0018] The hollow bodies according to the invention exhibit a significantly extended service life compared to the prior art, e.g., EP1771298A. A person skilled in the art would assume that the use of a PEBA outer layer would not lead to an extension of the service life, since it is known that PEBA molding compounds exhibit increased oxygen permeability (see Table 3). This would lead to the assumption that the expected embrittlement of the polyolefin inner layer could not be avoided.

[0019] Furthermore, the skilled person would have expected that the moderate hydrolysis resistance of the elastomer layer of the pipe would not extend the service life of the hollow bodies according to the invention.

[0020] However, Fig. 1 shows the surprising reverse effect of using an elastomer-containing polyamide layer as the outer layer.

[0021] The hollow bodies according to the invention, as well as the uses according to the invention, are described below by way of example, without the invention being restricted to these exemplary embodiments. If ranges, general formulas or classes of compounds are given below, these are intended to include not only the corresponding ranges or groups of compounds that are explicitly mentioned, but also all sub-ranges and sub-groups of compounds that can be obtained by removing individual values ​​(ranges) or compounds. If documents are cited within the scope of the present description, their contents are intended to be fully included in the disclosure of the present invention. If % figures are given below, these are in % by weight unless otherwise stated. In the case of compositions, the % figures refer to the total composition unless otherwise stated.Unless otherwise stated, average values ​​given below are mass averages (weight averages). Unless otherwise stated, measured values ​​given below were determined at a pressure of 101325 Pa and a temperature of 25 °C.

[0022] The polyamide units, which may be different, are statistically distributed. Statistical distributions are block-based with any number of blocks and any sequence, or they are subject to a random distribution. They can also be arranged alternately or form a gradient across the polymer chain. In particular, they can also form any mixed forms, in which groups of different distributions may follow one another. Special designs can result in limitations of the statistical distributions. For all areas not affected by the limitation, the statistical distribution remains unchanged.

[0023] The polyamides within the meaning of the present invention can be homopolymers, copolymers, or blends of different polyamides. The differences between the polyamides can be due, for example, to different monomers used in the polymerization, different molecular weight distributions (which can be expressed, for example, in different viscosities), or different numbers of end groups.

[0024] The polyamides are preferably selected from aliphatic and (semi-)aromatic polyamides. Suitable monomers can be ω-amino acids or lactams, resulting in so-called AB polyamides (so-called Perlon type), diamines or diacids, resulting in so-called AA.BB polyamides (so-called nylon type), or corresponding copolyamides of both types. Optionally, the monomers can be substituted, whereby the substituents must be inert with respect to the polymerization / polycondensation and preferably not be Brönsted acids or bases. In the case of the formation of AA.BB polyamides, the monomers can form so-called semi-aromatic polyamides, meaning that only one of the two building blocks, diamine or diacid, has an aromatic core.

[0025] Preferred monomers are selected from aliphatic C4 to C12 lactams or ω-aminocarboxylic acids having 4 to 44 carbon atoms, preferably 4 to 18 carbon atoms; from at least one diamine from the group of aliphatic diamines having 4 to 18 carbon atoms, cycloaliphatic diamines having 7 to 22 carbon atoms and aromatic diamines having 6 to 22 carbon atoms in combination with at least one dicarboxylic acid from the group of aliphatic dicarboxylic acids having 4 to 44 carbon atoms, cycloaliphatic dicarboxylic acids having 8 to 24 carbon atoms and aromatic dicarboxylic acids having 8 to 20 carbon atoms.

[0026] More preferably, the polyamides are selected from PA 8, PA 9, PA 10, PA 11, PA 12, PA 13, PA 14, PA 16, PA 4.6, PA 6.10, PA 6.12, PA 6.13, PA 6.14, PA 6.16, PA 8.10, PA 8.12, PA 8.13, PA 8.14, PA 9.10, PA 9.12, PA 10.10, PA 10.12, PA 10.14, PA 10.16, PA 10.18, PA 12.12, PA 12.14, PA 12.16, PA 6.T, PA 9.T, PA 10.T, PA 12.T and PA 14.T.

[0027] The hollow body according to the invention has at least three layers in its wall, an outer layer (i) made of a molding compound containing an elastomeric polyamide, an intermediate layer (ii) made of a molding compound containing a non-elastomeric polyamide and an inner layer (iii) made of a molding compound containing a polyolefin which does not contain any halogen atoms.

[0028] The polyamide portion of the molding composition of layer (i) of the hollow bodies according to the invention contains an elastomeric polyamide, preferably in a content of at least 20% by weight, more preferably 30% by weight, 40% by weight, 50% by weight, 60% by weight, 70% by weight, 80% by weight, at least 90% by weight and more preferably at least 95% by weight; preferably at most 95% by weight, 90% by weight, 85% by weight, 80% by weight, 75% by weight, 70% by weight, particularly preferably at most 65% by weight; furthermore preferably between 20% by weight and 95% by weight, more preferably between 40% by weight and 85% by weight. The polyamide portion of the molding composition of layer (i) particularly preferably consists of an elastomeric polyamide.

[0029] The elastomeric polyamide is preferably a block copolyamide and preferably contains soft segments (WB) made of polyether and preferably hard segments (HB) made of polyamide. The hard segments have a number-average of 8 or more carbon atoms per amide group. The polyamides of the hard segment are preferably selected from PA 8, PA 9, PA 10, PA 11, PA 12, PA 13, PA 14, PA 16, PA 6.10, PA 6.12, PA 8.10, PA 8.12, PA 8.14, PA 10.10, PA 10.12, PA 10.14, PA 10.16, PA 12.12, PA 12.14, PA 12.16, more preferably from PA 10, PA 11, PA 12, PA 6.10, PA 6.12, PA 10.10, PA 10.12, particularly preferably from PA 11, PA 12, PA 6.10, PA 6.12.

[0030] Preferably, the alkyl chains of the polyether are not branched, i.e. the alkyl chains are preferably linear, more preferably poly-1,2-ethylene glycol, poly-1,3-propylene glycol, poly-1,4-butylene glycol, particularly preferred are poly-1,2-ethylene glycol and poly-1,4-butylene glycol, especially preferred is poly-1,4-butylene glycol.

[0031] Preferably, the polyethers are bonded to the polyamide of the hard segment via an ester group.

[0032] The elastomeric polyamide preferably has soft segments whose molecular weight is lower than the molecular weight of the hard segments. The weight fraction of the soft segments (WB) is preferably from 10 to 49 wt.% based on the total mass of the elastomeric polyamide (WB + HB), more preferably 12 to 40 wt.%, even more preferably 15 to 35 wt.%, and especially preferably 18 to 30 wt.%.

[0033] The molding compound of layer (i) preferably comprises at least 20 wt.% of an elastomeric polyamide as described above, optionally a non-elastomeric polyamide, and at least 0.5 wt.% of a heat stabilizer in the polyamide part of the molding compound. Further preferably, the proportion of elastomeric polyamide is at least 20 up to 99.5 wt.% of the total molding compound of layer (i). More preferably, the proportion of elastomeric polyamide is at least 23, 26, 29, 32, 35, 40 wt.% and at most 99.5, 99, 98, 95, 90, 85, 80, 70 wt.%. Even more preferably, the proportion of elastomeric polyamide is from 26 to 99, particularly preferably from 29 to 95, and especially preferably from 32 to 85 wt.%.

[0034] The elastomeric polyamide is preferably heat-stabilized. Suitable heat stabilizers are aromatic amines. Preferred heat stabilizers are 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (Naugard 445) or N,N'-diphenyl-p-phenylenediamine, bis(4-(1-methyl-1-phenylethyl)phenyl)amine, 2-ethyl-2'-ethoxy-oxal anilide, dimethylglyoxime, 2,2-bipyridine, 1,10-phenanthrolines, ortho-phenylenediamines, 1,2-diaminocyclohexanes, 1,4-diaminobutanes, 8-hydroxyquinolines, urea, and / or substituted ureas. Suitable commercial products are NYLOSTAB S-EED from Clariant. T NAUGARD 445 from Addivant, OKABEST FLEX, OKABEST ULTRA-FLEX, OKABEST S-FLEX, OKABEST S-FLEX2, OKABEST S-FLEX 3, OKAFLEX U and OKAFLEX EM from OKA - Tec or mixtures containing the mentioned amines.

[0035] More preferred heat stabilizers are 4'-bis(a,a-dimethylbenzyl)diphenylamine (Naugard 445) or N,N'-diphenyl-p-phenylenediamine, phenylenediamine, bis(4-(1-methyl-1-phenylethyl)phenyl)amine, NAUGARD 445 from Addivant, OKABEST FLEX, OKABEST ULTRA-FLEX, OKABEST S-FLEX, OKABEST S-FLEX 2, OKABEST S-FLEX 3, OKAFLEX U and OKAFLEX EM from OKA-Tec or mixtures containing the amines mentioned.

[0036] Naugard 445 is particularly preferred.

[0037] The molding composition of layer (i) preferably comprises one or more heat stabilizers in a total amount of 0.5 to 2 wt.%, based on the total mass of the molding composition, more preferably 0.6 to 1.8, further more preferably 0.7 to 1.6, particularly preferably 0.8 to 1.4 and especially preferably 0.9 to 1.2 wt.%.

[0038] The molding compound of layer (i) preferably comprises an elastomeric polyamide whose block copolyamide has a linear polyether in the soft segment, preferably consisting of poly-1,2-ethylene glycol, poly-1,3-propylene glycol, poly-1,4-butylene glycol, particularly preferred are poly-1,2-ethylene glycol and poly-1,4-butylene glycol, especially preferred is poly-1,4-butylene glycol, wherein the polyether is bonded to the hard segment via an ester bond.

[0039] More preferably, the molding compound of layer (i) comprises one or more heat stabilizers and an elastomeric polyamide whose block copolyamide has a linear polyether in the soft segment, preferably consisting of poly-1,2-ethylene glycol, poly-1,3-propylene glycol, poly-1,4-butylene glycol, particularly preferred are poly-1,2-ethylene glycol and poly-1,4-butylene glycol, especially preferred is poly-1,4-butylene glycol, wherein the polyether is bonded to the hard segment via an ester bond. Preferably, the molding compound of layer (i) comprises one or more heat stabilizers and soft segments whose molecular weight is smaller than the molecular weight of the hard segments.

[0040] The molding compound of layer (i) preferably comprises one or more heat stabilizers and, in the polyamide part of the molding compound, preferably at least 20% by weight of an elastomeric polyamide.

[0041] More preferably, the molding composition of layer (i) comprises one or more heat stabilizers in a total amount of 0.5 to 2 wt.%, and soft segments whose molecular weight is smaller than the molecular weight of the hard segments, wherein the proportion of elastomeric polyamide in the molding composition is at least 20 wt.%.

[0042] The molding compositions of layer (i) preferably do not contain any functionalized polyolefin.

[0043] The non-elastomeric polyamides of layer (ii) are preferably amine-terminated, i.e., after determination of the end groups, the number of amine termini is greater than the number of acid termini.

[0044] Those skilled in the art know how the termini of polyamides can be synthesized in a defined manner. This is done using so-called regulators. In the case of nylon-type polyamides, this can simply be a stoichiometric excess of one of the two components. In the case of amine-terminated non-elastomeric polyamides, the diamines are used in excess.

[0045] Alternatively, a so-called external regulator is added; this can be done for both polyamide types (Perlon and nylon). These regulators can be, for example, monofunctionalized aliphatic or aromatic compounds for polyamide formation, thus creating inert termini for polyamide formation. Alternatively, diamino-functionalized or diacid-functionalized aliphatic or aromatic compounds can be used as regulators (for Perlon types).

[0046] The amine-terminated polyamides preferably have an amount of amine end groups of 30 mmol / kg to 70 mmol / kg and particularly preferably of 40 mmol / kg to 60 mmol / kg.

[0047] The ratio of amine termini to acid termini is preferably 4 to 12.

[0048] Furthermore, the relative solution viscosity is preferably in the range 1.9 to 2.3.

[0049] In a further embodiment, amine-terminated polyamides with lower relative solution viscosity may also be additionally included, which may increase the amount of amine end groups up to 100 mmol / kg.

[0050] The person skilled in the art knows how the end groups of polyamides are determined; they are preferably determined by titration, more preferably by the methods of the examples.

[0051] Preferably, the molding compound of layer (ii) does not contain any further polyamide.

[0052] The polyamide-containing molding compositions according to the invention preferably contain further additives.

[0053] Preferred additives are oxidation stabilizers, UV stabilizers, hydrolysis stabilizers, impact modifiers, pigments, dyes and / or processing aids.

[0054] In a preferred embodiment, the molding compositions contain an effective amount of an oxidation stabilizer, and more preferably an effective amount of an oxidation stabilizer in combination with the effective amount of a copper-containing stabilizer. Suitable oxidation stabilizers include, for example, aromatic amines, sterically hindered phenols, phosphites, phosphonites, thiosynergists, hydroxylamines, benzofuranone derivatives, acryloyl-modified phenols, etc. Such oxidation stabilizers are commercially available in a variety of types, for example under the trade names Irganox 1010, Irganox 1098, Irgafos 168, P-EPQ, or Lowinox DSTDP. In general, the molding compositions contain about 0.01 to about 2 wt.%, and preferably about 0.1 to about 1.5 wt.%, of an oxidation stabilizer.

[0055] In addition, the molding compounds can also contain a UV stabilizer or a HALS-type light stabilizer. Suitable UV stabilizers are primarily organic UV absorbers, such as benzophenone derivatives, benzotriazole derivatives, oxalanilides, or phenyltriazines. HALS-type light stabilizers are tetramethylpiperidine derivatives; these are inhibitors that act as free radical scavengers. UV stabilizers and light stabilizers can be used advantageously in combination. Both are commercially available in a variety of types; the manufacturer's instructions can be followed regarding dosage.

[0056] The molding compounds may additionally contain a hydrolysis stabilizer such as a monomeric, oligomeric or polymeric carbodiimide or a bisoxazoline.

[0057] Furthermore, the molding compounds can contain impact modifiers. Impact-modifying rubbers for polyamide molding compounds are state of the art. They contain functional groups derived from unsaturated functional compounds that are either polymerized into the main chain or grafted onto the main chain. The most common are EPM or EPDM rubbers radically grafted with maleic anhydride. Such rubbers can also be used together with an unfunctionalized polyolefin such as isotactic polypropylene, as described in EP0683210A2 (US5874176A) and / or EP2132030A2 (US2010 / 0183837A1).

[0058] Suitable pigments and / or dyes are, for example, carbon black, organic color pigments, iron oxide, zinc sulfide, ultramarine, nigrosine, pearlescent pigments.

[0059] Suitable processing aids include paraffins, fatty alcohols, fatty acid amides, stearates such as calcium stearate, paraffin waxes, montanates or polysiloxanes.

[0060] The aforementioned polyamides of the non-elastomeric molding compound are in principle suitable, together with the aforementioned elastomeric polyamides, to form the polyamide portion of layer (i) as a soft segment, whereby the hard segments must be acid-terminated.

[0061] The molding compositions of layer (ii) preferably comprise a functionalized polyolefin, preferably an impact modifier.

[0062] The polyolefin of layer (iii) preferably contains polypropylene as the majority component (with more than 50 wt%). In a more preferred embodiment, the polyolefin contains at least 0.5 wt%, at least 0.6 wt%, at least 0.7 wt%, at least 0.8 wt%, or at least 0.9 wt%, as well as a maximum of 20 wt%, a maximum of 15 wt%, a maximum of 12 wt%, a maximum of 10 wt%, or a maximum of 8 wt% of polymerized ethene. In addition, up to 15 wt% of 1-butene can be polymerized.

[0063] The polyolefin molding compound of the inner layer (iii) can in principle contain any commercially available type of polypropylene, for example isotactic or syndiotactic homopolypropylene, a random copolymer of propene with ethene and / or butene-1, an ethylene-propylene block copolymer, a thermoplastic elastomer based on polypropylene, and the like. It can contain an impact-modified component such as EPM or EPDM rubber or SEBS. In addition, the usual auxiliaries and additives can be included, for example pigments or fillers such as carbon black, titanium dioxide, zinc sulfate, silicates or carbonates, or processing aids such as waxes, zinc stearate, or calcium stearate. Proportions of polypropylene in the molding compound are at least more than 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, or at least 90% by weight.

[0064] Particularly preferably, the polyolefin used in the innermost layer (iii) has a melt flow rate (MFR) according to ISO 1133 (230 °C / 2.16 kg) in the range from 0.1 to 3 g / 10 min, particularly preferably in the range from 0.15 to 2 g / 10 min, especially preferably in the range from 0.18 to 1.5 g / 10 min and very particularly preferably in the range from 0.2 to 1 g / 10 min.

[0065] The polyolefin of the innermost layer (iii) is particularly preferably a propene-ethene block copolymer, frequently also referred to as a heterophasic copolymer. Such heterophasic copolymers can be produced, for example, in a two-phase process that proceeds approximately as follows: First, a highly isotactic polypropylene is produced, e.g., using a Ziegler-Natta catalyst; under certain circumstances, a small amount of ethene may be present, resulting in a random polymer. This material acts as the matrix of a heterophasic copolymer. In a second reaction step (optionally in a different reactor), a second catalyst, e.g., a metallocene catalyst, is optionally introduced. Ethylene then copolymerizes with propene, with this polymerization taking place in cavities of the first polymer. As a result, the second polymer is incorporated there.

[0066] More preferably, the polyolefin contains a heat stabilizer. This can be, for example, a sterically hindered phenol or a sulfur compound, such as a dialkyl ester of thiopropionic acid or a thiodiethylene diester. Such compounds are commercially available; of course, mixtures of different heat stabilizers can also be used.

[0067] Furthermore, the polyolefin preferably contains a metal deactivator, which is preferably phenol-based.

[0068] Particularly preferred is a stabilizer mixture containing as heat stabilizer at least one sterically hindered phenol and at least one sulfur compound and a metal deactivator.

[0069] The amount of stabilizers is preferably 0.3 to 2 wt.%, more preferably 0.5 to 1.5 wt.% and particularly preferably 0.7 to 1.2 wt.%, based on the total mass of the polyolefin.

[0070] Furthermore, the polyolefin preferably comprises a nanoscale filler. This at least one filler is preferably selected from color particles and particles that reduce thermal conductivity. Preferred color particles are carbon black particles. The polyolefin inner layer (layer iii) preferably has a thickness of at least 0.3 mm and particularly preferably of at least 0.4 mm. The total wall thickness of the tube is preferably in the range from 0.8 to 2.5 mm, particularly preferably in the range from 0.9 to 2 mm and especially preferably in the range from 1 to 1.5 mm; the outer diameter of the tube is preferably in the range from 8 to 50 mm, particularly preferably in the range from 10 to 40 mm and especially preferably in the range from 12 to 30 mm.

[0071] In a second possible embodiment, the inner layer (iii) contains a further layer (iiia), and this layer (iiia) is located between layer (ii) and layer (iii).

[0072] Layer (iiia) is preferably modified, while layer (iii) is preferably unmodified. The modification is preferably an adhesion modification. Apart from adhesion modification, different polyolefin molding compounds can be used for the layer materials.

[0073] The molding compound of the adhesion promoter layer (iiia) preferably comprises a polyolefin,

[0074] The polyolefin of layer (iiia) can be a propylene / ethylene copolymer modified with an unsaturated epoxide and optionally with an ester or salt of an unsaturated carboxylic acid or a vinyl ester of a saturated carboxylic acid. These are, for example, propylene / ethylene / alkyl acetate / glycidyl (meth)acrylate copolymers or propylene / ethylene / alkyl (meth)acrylate / glycidyl (meth)acrylate copolymers; or copolymers of propylene with an unsaturated carboxylic acid anhydride and / or with an unsaturated carboxylic acid that can be partially neutralized by a metal (Zn) or an alkali metal (Li), and optionally with an ester of an unsaturated carboxylic acid or a vinyl ester of a saturated carboxylic acid. These are, for example, propylene / vinyl acetate / maleic anhydride copolymers, propylene / alkyl (meth)acrylate / maleic anhydride copolymers or propylene / Zn or Li (meth)acrylate / maleic anhydride copolymers.which is acid-, anhydride- or epoxy-modified.

[0075] The density of the functionalized polyolefin is advantageously between 0.86 and 0.965 g / ml.

[0076] More preferably, the polyolefin is functionalized by a carboxylic acid anhydride.

[0077] The functionalized polyolefin is particularly preferably a maleic anhydride-grafted propylene copolymer.

[0078] The multilayer hollow bodies according to the invention are preferably used for storing or transporting an aqueous medium. Figure 1 shows the elongation at break of pipes as a function of aging. The diamonds and solid line correspond to pipe R3 of the prior art design according to EP1771298A, the circles and dotted line correspond to pipe R2 according to the invention, and the filled circles and dashed line correspond to pipe R1 according to the invention. This demonstrates the improved mechanical stability under identical aging conditions compared to the prior art.

[0079] Figure 2 shows an example pipe with layers (i), (ii), (iiia) and (iii).

[0080] Methods:

[0081] End-group determinations

[0082] Carboxylate end groups:

[0083] 2.0 g (expected value below 15 mmol / kg) or 1.0 g (expected value above 15 mmol / kg) of the sample are weighed into a weighing container. Approximately 40 ml (or 20 ml) of benzyl alcohol are added to the thermostatted titration vessel. The sample is then transferred to the benzyl alcohol and dissolved under inert gas while stirring. The dissolution time is 10 min (or 15 min).

[0084] After dissolution, 3 drops of indicator solution are added and quickly titrated with potassium hydroxide solution (KOH in water) (concentration 0.1 mol / l).

[0085] Amino end groups:

[0086] Weigh 0.5 g of the sample and add 50 ml of m-cresol. The sample is dissolved within one hour by heating to 100°C (or 140°C if necessary). After cooling to room temperature, 5 ml of methanol are added, and the potentiometric titration is started. A blank value of the solvent mixture is subtracted for evaluation.

[0087] Relative solution viscosity:

[0088] The determination was carried out according to ISO 307: Granules were dissolved in m-cresol at 100°C at a concentration of 0.005 g / ml for 2 hours. The measurement was carried out using a Schott AVS Pro III at 25°C. Materials:

[0089] PA1 : Impact modified, heat stabilized PA12 with amino end group excess without fillers

[0090] PA2: Unfilled, unmodified, amine-regulated PA12 with a relative solution viscosity of 2.1

[0091] VESTAMID F: Color granules based on PA12

[0092] Polyolefin (PO): Polypropylene, RTP199X111239, Stabilized polypropylene extrusion molding compound from RTP

[0093] Adhesion promoter (HV): Maleic acid functionalized polypropylene from Mitsui, Admer QB520 E

[0094] Table 1a: Composition of elastomeric polyamides

[0095] Table 1 b: PEBA Blends: Blends of PEBA3 with PA2 plus 1 wt% Naugard 445, 2.3 wt% VESTAMID F and 0.02 wt% Ceasit PC

[0096] These elastomeric polyamide blends were compounded using a twin-screw extruder.

[0097] For pipe production, 1% Naugard 445 was added to the elastomeric polyamides PEBA3 and PEBA5 using a twin-screw extruder. Example 1:

[0098] Production of pipes:

[0099] Four-layer pipes with an outer diameter of 8 mm and a wall thickness of 1 mm were produced on a multi-layer line. The melt temperature was 250°C. The extrusion speed was 12 m / min.

[0100] Table 2: Pipes R1 to R3 according to the manufacturing description of Example 1: inner layer and adhesion promoter identical for all samples.

[0101] Pipe R3 corresponds to a coolant line according to EP1771298A. Examples R1 and R2 are according to the invention.

[0102] Example: Application resistance of pipes (combination of heat and hydrolysis stress)

[0103] The pipes are cut into 3m long sections and connected in a hot air oven for up to 2000 h at 130°C with a recirculating flow of an ethylene glycol-water mixture (1 / 1 [V / V]); the outside temperature was also 130°C.

[0104] In preparation for the mechanical test, the pipes are rinsed several times with demineralized water, cut into pieces of 180 mm length and stored for at least 16 hours at standard climate (23°C / 50% relative humidity).

[0105] The specimens were tested in a tensile test machine based on DIN 527-2 (2012) to determine elongation at break. The test temperature was 23°C and the test speed was 100 mm / min (5 specimens). Table 3: Elongation at break of the pipes according to Example 1

[0106] The advantages of the pipes according to the invention over the prior art are an extended service life combined with improved elongation at break (elongation at break). These values ​​are shown in Fig. 1.

[0107] Hydrolysis resistance:

[0108] Injection-molded test specimens (sawn middle sections of multi-purpose rods) consisting of the listed blends according to Table 1b were treated in an autoclave in an ethylene glycol-water mixture (1 / 1 [V / V]) at 130°C.

[0109] To determine stability, the Charpy impact factors were determined at -40°C. ISO 179-1:2010 was applied to unnotched specimens. Table 4: Charpy impact strength [kJ / m 2 ], mean values ​​of 6 specimens

[0110] It is evident that the impact strength decreases with increasing polyether block amide content. Oxygen permeability:

[0111] The oxygen permeability was determined in duplicate on extruded films with a thickness of approximately 100 μm according to ISO 15105 under air atmosphere with nitrogen as the carrier gas. The atmospheric conditions were 23°C and 50% relative humidity.

[0112] Humidity.

[0113] Table 3: Oxygen permeation: It can be seen that the permeability of PEBA3 is about twice as high as that of the pure hard block polymer.

Claims

Claims:

1. A hollow body suitable for storing or transporting an aqueous medium, the wall of which has at least three layers, the layers being constructed from the outside to the inside as follows: i. a layer of a molding compound containing an elastomeric polyamide, ii. a layer of a molding compound containing a non-elastomeric polyamide, iii. a layer of a molding compound containing a polyolefin which does not contain any halogen atoms.

2. Hollow body according to claim 1, wherein the elastomeric polyamide of layer (i) is a block copolyamide having hard and soft segments, the soft segments of which are polyethers.

3. Hollow body according to at least one of claims 1 or 2, wherein the elastomeric polyamide of layer (i) is a block copolyamide whose soft segments are polyethers, the polyethers having a linear chain.

4. Hollow body according to at least one of claims 2 to 4, wherein the polyether is bonded to the hard segments via an ester bond.

5. Hollow body according to at least one of claims 1 or 2, wherein the molding compound of layer (i) contains no functionalized polyolefin.

6. Hollow body according to at least one of the preceding claims, wherein the molding compound of layer (i) comprises a heat stabilizer.

7. Hollow body according to claim 1, wherein the non-elastomeric polyamide of layer (ii) is an amine-terminated polyamide.

8. Hollow body according to claim 1, wherein the polyolefin of layer (iii) is a non-functionalized hydrocarbon.

9. Hollow body according to claims 1 or 8, wherein the polyolefin of layer (iii) contains polypropylene.

10. Hollow body according to claims 1, 8 or 9, wherein layer (iii) contains a further layer (iiia), and this layer (iiia) lies between layer (ii) and layer (iii).

11. Hollow body according to claim 8, wherein the further layer (iiia) comprises a modified polyolefin.

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