CA2145254A1

CA2145254A1 - Multilayer plastic pipe

Info

Publication number: CA2145254A1
Application number: CA002145254A
Authority: CA
Inventors: Stefan Rober; Hans Jadamus; Hans Ries
Original assignee: Huels AG
Current assignee: Evonik Operations GmbH
Priority date: 1994-03-24
Filing date: 1995-03-22
Publication date: 1995-09-25
Also published as: JP3970345B2; US5554426A; ES2219650T3; JPH07266474A; EP0673762A3; DE4410148A1; DE59510907D1; EP0673762A2; BR9501173A; EP0673762B1

Abstract

A multilayer plastic pipe comprising polyamide and polyvinylidene fluoride and having adhesion between the layers and improved resistance to chemical agents such as, for example, methanol-containing fuels is provided.
The typical use properties of polyamide and polyvinyl-idene fluoride are not to be impaired by the measures required for achieving adhesion between the layers.

This is achieved by means of multilayer plastic pipes consisting at least of I. a layer based on a moulding composition of poly-amide, and II. a layer adjacent to layer I and based on a moulding composition comprising a mixture of a) from 97.5 to 50% by weight of polyvinylidene fluoride and b) from 2.5 to 50% by weight of an acrylate co-polymer, with the layers adhering to one another.

By means of the invention it is possible to obtain multilayer plastic pipes having the desired improved property profile.

Description

- 214~2~4 ~uls Aktiengesellschaft - 1 - O.Z. 4834 Patentabteilung Multilayer plastic pipe The invention relates to a multilayer plastic pipe.

Plastic pipes of polyamide are known and are used for a variety of applications. To perform their function, the pipes have to be, inter alia, inert to the medium flowing in them and also resistant to high and low temperatures and mechanical stresses.

Single-layer pipes are not always able to fulfil the necessary requirements. In the transport of, for example, aliphatic or aromatic solvents, fuels or the like, they display considerable disadvantages, such as inadequate barrier action towards the medium, undesired dimensional changes or insufficient mechanical stressability.

Attempts have been made to eliminate these disadvantages by means of multilayer pipes (DE-A 35 10 395; 37 lS 251;
38 21 723; 40 01 125; 40 01 126). However, the practical application of these proposals has revealed that although individual disadvantages can be avoided, the overall property profile is still unsatisfactory.

FR-P 2 602 515 describes a two-layer pipe having an outer layer of polyamide 11 and an inner layer of plasticized polyvinylidene fluoride. However, investigations have shown that the barrier action towards the medium flowing through is unsatisfactory. In addition, the lack of adhesion is a considerable disadvantage.

The permeation of methanol-containing fuels, in par-ticular, could be reduced only insufficiently by means of the abovementioned proposals.

Reducing the permeation by use of new types of inter-mediate layers is of decisive importance, particularly because the permissible emission values are being reduced ever further by legal requirements.

214525~1 - 2 - O.Z. 4834 The unpublished German Patent Application P 43 26 130.2 discloses thermoplastic multilayer composites of PVDF and polyamide. To achieve adhesion of the layers to one another, the PVDF contains small amounts of a polyglutar-imide. However, multilayer pipes are not explicitlydescribed in this document.

It is an object of the present invention to develop a polyamide pipe having a good barrier action towards the medium being transported, in particular towards methanol-containing fuels, a satisfactory dimensional stability,e.g. at high and low temperatures, and also a satisfac-tory mechanical stressability. It is here absolutely necessary for the layers to adhere to one another without use of a layer of coupling agent. Of course this adhesion should also be maintained during prolonged action of the medium being transported.

This object is achieved by means of a multilayer plastic pipe consisting at least of I. a layer based on a moulding composition of poly-amide, and II. a layer adjacent to layer I and based on a moulding composition comprising a mixture of a) from 97.5 to 50% by weight of polyvinylidene fluoride and b) from 2.5 to 50% by weight of an acrylate co-polymer, with the layers adhering to one another.

_ _ 3 _ O.Z. 4834 The components II a and II b are preferably used in a weight ratio of from 97.5 to 80 : from 2.5 to 20 and particularly preferably from 96 to 90 : from 4 to 10.

Suitable components I are, first and foremost, aliphatic homopolyamides and copolyamides. Examples which may be mentioned are 4.6, 6.6, 6.12, 8.10 and 10.10 polyamides or the like. Preference is given to 6, 10.12, 11, 12 and 12.12 polyamides. [The numbering of the polyamides corresponds to the international standard, with the first digit(s) indicating the number of carbon atoms of the starting diamine and the last digit(s) indicating the number of carbon atoms of the dicarboxylic acid. If only one number is given, this means that the polyamide has been made from an a,~-aminocarboxylic acid or from the lactam derived therefrom, see H. Domininghaus, Die Runstoffe und ihre Eigenschaften, page 272, VDI (1976).]

If copolyamides are used, these can contain, for example, adipic acid, sebacic acid, suberic acid, isophthalic acid, terephthalic acid as co-acid or bis(4-aminocyclo-hexyl)methane, trimethylhexamethylenediamine, hexa-methylenediamine or the like as co-diamine.

The preparation of these polyamides is known (e.g.: D.B.
Jacobs, J. Zimmermann, Polymerization Processes, p. 424-467; Interscience Publishers, New York (1977); DE-B 21 52 194).

Likewise suitable as polyamides are mixed aliphatic/arom-atic polycondensates such as are described, for example, in US-A 2 071 250, 2 071 251, 2 130 523, 2 130 948, 2 241 322, 2 312 966, 2 512 606, 3 393 210 or in Kirk-Othmer; Encyclopedia of Ch~mical Technology, 3rd edition, vol. 18, Wiley & Sons (1982), pp. 328 and 435. Further polycondensates which are suitable as polyamides are poly(ether esteramides) or poly(etheramides). Such products are described, for example, in DE-A 27 12 987, 25 23 991 and 30 06 961.

- 4 - O.Z. 4834 Both polyamides having predominantly amino terminal groups and those having predominantly carboxylic acid terminal groups can be used. Preference is given to polyamides having predominantly amino terminal groups.

The molecular weight (number average) of the polyamides is above 4,000, preferably above 10,000. The relative viscosity (~rel) is here preferably in the range from 1.65 to 2.4.

The polyamides can contain up to 40~ by weight of other thermoplastics, if these do not interfere with the properties of the invention. Mention may here be made, in particular, of polycarbonate [H. Schnell, Chemistry and Physics of Polycar~onates, Interscience Publishers, New York (1981)], Acrylonitrile-styrene-butadiene copolymers [Houben-Weyl, Methoden der organischen Chemie, vol. 14/1, Georg Thieme Verlag Stuttgart, pp. 393-406; Ullmanns Encyclopadie der technischen Chemie, 4th edition, vol.
19, Verlag Chemie Weinheim (1981), pp. 279-284], acrylo-nitrile-styrene-acrylate copolymers [Ullmanns Encyclopadie der technischen Chemie, 4th edition, vol.
19, Verlag Chemie Weinheim (1981), pp. 277-295], acrylo-nitrile-styrene copolymers [ullm~ns Encyclopadie der technischen Chemie, 4th edition, vol. 19, Verlag Chemie Weinheim (1981), p. 273 ff.] or polyphenylene ethers (DE-A 32 24 691 and 32 24 692; US-A 3 306 874, 3 306 875 and 4 028 341).

If required, the polyamides can be toughened. Suitable modifiers are, for example, ethylene-propylene or ethyl-ene-propylene-diene copolymers (EP-A-0 295 076), polypen-tenylene, polyoctenylene or random or block copolymers of alkenylaromatic compounds and aliphatic olefins or dienes (EP-A-0 261 748). Furthermore, the impact-toughening rubbers used can be core/shell rubbers having a visco-elastic core of (meth)acrylate, butadiene or styrene-butadiene rubber with glass transition temperatures Tg < -10C, with the core may be crosslinked.

21~S2~
_ _ 5 _ O.Z. 4834 The shell can be built up of styrene and/or methyl meth-acrylate and/or further unsaturated monomers (DE-A
21 44 528, 37 28 685). The proportion of impact-toughen-ing components should be selected in such a way that the desired properties are not impaired.

Component II a contains polyvinylidene fluoride, which is preferably used in unplasticized form. Preparation and structure of the polymer are known (Hans R. Kricheldorf, Handkook of Polymer Synthesis, Part A, Verlag Marcel Dekker Inc. New York - Basel - Hongkong, pp. 191 ff.;
~unststoff-~andbuch, 1st edition, vol. XI, Carl Hanser Verlag Munich (1971), pp. 403 ff.).

According to the invention, the polyvinylidene fluoride present can also be a copolymer based on vinylidene fluoride which contains up to 40~ by weight of other monomers. Examples which may be mentioned of such addi-tional monomers are: trifluoroethylene, ethylene, propene and hexafluoropropene.

The polyvinylidene fluoride used according to the inven-tion generally has a melt flow index of < 17 g/10 min,preferably from 2 to 13 g/10 min (DIN 53 735).

The component II b used in the layer II is an acrylate copolymer containing at least the following basic build-ing blocks:

i) from 14 to 85% by weight, preferably from 35 to 70% by weight, of R~

~,C~
I

Akyl 21452~
- 6 - O.Z. 4834 ii) from 0 to 75~ by weight, preferably from 10 to 75~ by weight, of 1~2 R~
-~-T-~ f-o~ --N-- ~o iii) from 0 to 15% by weight of COOH
iiii) from 7 to 20% by weight, preferably 5from 8 to 12% by weight, of R~. R4 -- (CH2)m C--(CH2)m--C--o~C O C~o In the specified formulae Alkyl = methyl, ethyl, propyl, butyl, pentyl, hexyl Rl to R5 = H or (CnH2n+l) with n = 1 to 6 and m = 0 or 1, with the radicals Rl to R5 being identical or different.
Preference is given to those basic building blocks in which Rl to R5 are methyl radicals. Likewise, Alkyl is preferably methyl. Furthermore, m is preferably 1.

The acrylate copolymers are prepared in a known manner by polymerization of the corresponding monomers. In the case of m = 0 and R4 = H, the basic building block iiii) is derived, for example, from maleic anhydride, while in 2I~52a4 - 7 - O.Z. 4834 the case of m = 1, the basic building block iiii) is formed by saponification of two adjacent units of the component i) and subsequent cyclization.

In a preferred embodiment, the basic building block ii) is present in an amount of from 10 to 75~ by weight, particularly preferably from 20 to 40% by weight. Such polymers are also described as polyglutarimides. These are poly(alkyl acrylates), in which two adjacent carboxylate groups have been reacted to form a cyclic acid imide. The imide formation is preferably carried out using ammonia or primary amines such as, for example, methylamine. Here, because of the presence of water in the imide formation reaction, part of the basic building blocks i) is saponified to give the basic building blocks iii) and iiii). The products and their preparation are known (Hans R. Kricheldorf, Handbook of Polymer Synthesis, Part A, Verlag Marcel Dekker Inc. New York -Basel - Hongkong, pp. 223 ff.; H. G. Elias, Ma~romolek~le, Huthig und Wepf Verlag Basel - Heidelberg - New York; US-A 2 146 209, 4 246 374).

The acrylate copolymers used according to the invention generally have a melt flow index of < 30 g/10 min, preferably from 0.2 to 15 g/10 min.

To increase the low-temperature impact toughness, the acrylate copolymers can additionally contain appropriate modifiers. Examples which may be mentioned are core/shell polymers having a polybutyl acrylate core and a shell of polymethyl methacrylate and/or polyglutar-imide. Apart from the examples given, further modifiers are possible.

To the moulding compositions for the layers I and II may be added conventional auxiliaries and additives such as, for example, flame retardants, stabilizers, plastici-zers, processing aids, viscosity improvers, fillers, here particularly those for improving the electrical - 8 - O.Z. 4834 conductivity, pigments or the like. The amount added of the specified agents is to be selected in such a way that the desired properties are not seriously affected.

The preparation of the moulding composition for the layer II is carried out according to conventional and known processes by melt mixing of the components II a and II b in a mixer providing good compounding, such as, for example, a twin-screw compounder, at temperatures which depend on the melting points of the components II
a and II b, generally at temperatures between 200 and 300C.

The preparation of the component II from the components IIa and IIb can also be carried out directly in the processing extruder in which the component II is processed for the production of the thermoplastic multi-layer composite with the layer I.

The requirement for as high as possible a barrier action towards the medium being transported can be met all the better, the smaller the content of component II b in the moulding composition for the layer II. For example, the barrier action towards methanol-containing fuels of mixtures comprising 95% by weight of polyvinylidene fluoride polymers (component II a) and 5~ by weight of an acrylate copolymer of the invention (component II b) is only inconsequentially poorer than the barrier action of pure polyvinylidene fluoride.

The multilayer pipes can additionally contain further layers of polyvinylidene fluoride polymers which are adjacent to layer II, but not to layer I. Likewise, the multilayer pipes can contain further layers of polyamide which are adjacent to layer I or layer II.

In particular, the pipes can contain further layers I
and/or II which have been made electrically conductive and have a surface resistance of less than 109 Q. These 214~25~
_ _ g _ O.Z. 4834 layers which have been made electrically conductive are preferably used on the inside.

A further embodiment comprises making the layer II
itself electrically conductive.

The layers are made electrically conductive by known methods. For example, an addition is made of up to about 15 ~ by weight of, for example, conductivity black, carbon fibres or the like.

The multilayer pipes of the invention can also be built up in such a way that, in addition to the layers I and II, they contain a) at least one layer based on a polyolefin and b) at least one layer based on a conventional coupling agent for bonds between polyolefin and polyamide, with the layer of coupling agent being directly between the layer I and the layer based on a polyolefin.

Examples of polyolefins which may be mentioned are polyethylene and polypropylene. In principle, any commercial type of these can be used. Suitable examples are thus: linear polyethylene of high, medium or low density, LDPE, ethylene copolymers containing relatively small amounts (up to a maximum of about 40% by weight) of comonomers such as n-butyl acrylate, methyl methacrylate, maleic anhydride, styrene, vinyl alcohol or the like, isotactic or atactic homopolypropylene, random copolymers of propene with ethene and/or 1-butene, ethylene-propylene block copolymers and other similar polymers. Such polyolefins can also contain an impact-toughening component such as, for example, EPM or EPDM rubber or SEBS.

Suitable coupling agents for bonds between polyolefins 214525~
- 10 - O.Z. 4834 and polyamide are known. They are based on polyolefin which is modified by suitable reactive groups. The reactive groups can here be introduced either by copolymerization together with the olefin or by means of a grafting reaction. In the grafting reaction, a preformed polyolefin is reacted in a known manner with an unsaturated functional monomer and, advantageously, a free-radical donor at elevated temperature.

Suitable reactive groups are, for example, acid an-hydride groups, carboxylic acid groups, epoxide groups, oxazoline groups or trialkoxysilane groups. Of these, preference is given to using acid anhydride groups.
Coupling agents containing more than 0.1 ~ by weight of anhydride groups are particularly suitable.

Suitable coupling agents are available, inter alia, under the trade names BYNEL tDuPont), PRIMACOR (Dow), POLYBOND (BP), OREVAC (Elf), HERCOPRIME (Hercules), EPOLENE (Eastman), HOSTAMONT (Hoechst), EXXELOR (Exxon) and ADMER (Mitsui Petrochemical). The coupling agents are selected according to the criteria which are known to those skilled in the art with the aid of the corres-ponding product descriptions. In the multilayer pipes of the invention, all adjacent layers adhere to one another.

Table 1 shows some examples of layer arrangements in multilayer plastic pipes of the invention.

In a preferred embodiment, the layers are arranged and the thickness of the layers is selected in such a way that the layers II lie as close as possible to the mîddle of the multilayer pipe wall. This measure improves the low-temperature impact toughness of the multilayer pipes.

Furthermore, it is preferred that the thickness of the layer II is selected in such a way that it makes up from 2I~525~

- 11 - O.Z. 4834 2 to 40% of the total wall thickness and, in particular, from 5 to 30~ of the total wall thickness.

The manufacture of the multilayer plastic pipes can be carried out, for example, by coextrusion.

The multilayer plastic pipes of the invention have exceptionally good resistance and barrier action against diffusion towards chemical agents, solvents and fuels.
In addition, the layers adhere to one another so that, for example on thermal expansion, bending or thermofor-ming of the multilayer pipe, no shearing of the variouslayers from one another occurs. This good adhesion between the layers is maintained even on prolonged contact with fuels, in particular even methanol-contai-ning fuels.

214525~

- 12 - O.Z. 4834 Table l: Layer arrangement of multilayer plastic pipes of the invention (buildup from out-side to inside) 5Layer arrangement Configuration No.

1 Layer I
Layer II
2 Layer I
Layer II (conductive) 3 Layer I
Layer II
Layer I

4 Layer I
Layer II
Layer I (conductive) Layer I
Layer II
Layer I
Layer II
Layer I

6 Layer I
Layer II
Layer I
Layer II (conductive) 21~525~
- 13 - O.Z. 4834 Table 1 (continuation) Layer arrangement Configuration No.
s 7 Layer I
Layer II
Layer I
Layer II
Layer I (conductive) 8 Layer I
Layer II
Layer of polyvinylidene flu-oride copolymers 9 Layer I
Layer II
Layer of polyvinylidene flu-oride copolymers (conductive) Layer I
Layer I (other type of polyamide) Layer II

11 Layer II
Layer I

12 Layer of polyolefin Layer of coupling agent Layer I
Layer II

35 The plastic pipes of the invention are preferably used for the transport of (petro)chemical materials or in the motor vehicle sector for conveying bra~e, cooling and hydraulic fluids and also fuel, including, in particular, methanol-containing or ethanol-containing 21952~
- 14 - O.Z. 4834 fuel. A further application of the multilayer pipes is the manufacture from them of hollow bodies such as tanks or filling ports, in particular for the motor vehicle sector. The manufacture of these hollow bodies is carried out, for example, by a blow moulding process following coextrusion.

The parameters specified were determined by means of the following measurement methods.

The determination of the solution viscosity (relative viscosity ~r~l ) Of the polyamides is carried out using a 0.5~ by weight strength m-cresol solution at 25C in accordance with DIN 53 727/ISO 307.

For determination of the ~mi no terminal groups, 1 g of the polyamides is dissolved in 50 ml of m-kresol at 25C. The solution is titrated potentiometrically with perchloric acid.

For determination of the carboxyl terminal groups in the polyamides, 1 g of polycondensate is dissolved in 50 ml of benzyl alcohol under a blanket of nitrogen at 165C.
The solution time is a maximum of 20 minutes. The solu-tion is titrated with a solution of KOH in ethylene glycol (0.05 mol KOH/l) against phenolphthalein until the colour changes.

The dete ination of the melt flow index of the acrylate copolymers is carried out at 230C and under a load of 3.8 kg (DIN 53 735).

The dete. in~tion of the melt flow index of the poly-vinylidene fluorides is carried out at 230C and under a load of 5 kg (DIN 53 735).

The testing of the mechanical separability at the inter-face is carried out using a metal wedge (cutting angle:

5 degrees; loading weight: 2.5 kg) which is used to try 2 ~ ~
- 15 - O.Z. 4834 to separate the material interface layer to be tested.
If separation occurs at the interface between the com-ponents, the adhesion is poor. If, on the other hand, separation occurs completely or partially within one of the two components, good adhesion is present.

The deter~ination of the diffusion of fuel constituents is carried out on pipes using a fuel mixture (fuel M 15:
42.5 parts by volume of isooctane, 42.5 parts by volume of toluene and 15 parts by volume of methanol) at 60C.
The test specimens, having a length of 500 mm, have the fuel mixture running through inside. The determination of the fuel diffusion is carried out by the activated carbon adsorption method. The diffusion is measured as loss in mass over time (measurement every 24 hours). The measure given is the loss in mass recorded per unit area which is measured when the diffusion process is at equilibrium, i.e. when the loss in mass determined per 24 hours no longer changes with time.

Examples denoted by letters are not according to the invention.

Examples Component I

PA 1: Polyamide 12 (~rel: 2.1; plasticizer content: 0;
amino terminal group content: 9 mmol/kg;
carboxyl terminal group content: 48 mmol/kg;
VESTAMI D~ L 2140 - HULS AG) PA 2: Polyamide 12 (~rel: 2.1; plasticizer content per 100 parts by weight of polyamide: 15 parts by weight of N-n-butylbenzenesulphonamide; amino terminal group content: 9 mmol/kg; carboxyl terminal group content: 48 mmol/kg; VESTAMID~ L
2124 - HULS AG) 21~525~
. .
- 16 - O.Z. 4834 PA 3: Polyamide 12 (~ 2.1; plasticizer content per 100 parts by weight of polyamide: 15 parts by weight of N-n-butylbenzenesulphonamide; amino terminal group content: 50 mmol/kg; carboxyl S terminal group content: 8 mmol/kg) PA 4: Polyamide 612 (~r~l 1.9; plasticizer content:
0; amino terminal group content: 93 mmol/kg;
carboxyl terminal group content: 29 mmol/kg) PA 5: Moulding composition consisting of a. 100 parts by weight of polyamide 12 (~r~l 2.1;
plasticizer content: 0; amino terminal group content: 9 mmol/kg; carboxyl terminal group content: 48 mmol/kg) and b. 4 parts by weight of commercial conductivity black (Ketjenblack~ EC 300 - AXZO) Component II

PVDF 1: Polyvinylidene fluoride (melt flow index: 13 g/10 min, DYFLORD LE - HULS AG).

PVDF 2: Polyvinylidene fluoride (melt flow index:
8.5 g/10 min, DYFLORD EE - HULS AG).

PVDF 3: Polyvinylidene fluoride consisting of a) 100 parts by weight of polyvinylidene fluoride (melt flow index: 8.5 g/10 min, DYFLOR~ EE -HULS AG) and b) 6 parts by weight of commercial conductivity black (XetjenblackD EC 300 - AKZO).

21~52~
- 17 - O.Z. 4834 The polymers used for the component II b are built up of the building blocks denoted above by i) to iiii), with Alkyl and Rl to R5 being methyl in each case and m being 1.

% by weight of i)100 14 11 57 % by weight of ii)0 86 80 30 % by weight of iii) 0 0 6 3 % by weight of iiii) 0 0 3 10 Melt flow index 0.8 0.4 0.4 0.4 [g/10 min]

Zl: Mixture consisting of a) 50 % by weight of PVDF 1 and b) 50 % by weight of Pl Z2: Mixture consisting of a) 50 % by weight of PVDF 1 and b) 50 % by weight of P2 Z3: Mixture consisting of a) 50 ~ by weight of PVDF 1 and b) 50 % by weight of P3 z4: Mixture consisting of a) 50 % by weight of PVDF 1 and b) 50 % by weight of P4 21452~1 - 18 - O.Z. 4834 Z5: Mixture consisting of a) 90 ~ by weight of PVDF 1 and b) lO ~ by weight of P4 Z6: Mixture consisting of a) 95 % by weight of PVDF 2 and b) S ~ by weight of P4 Z7: Mixture consisting of a) 90 % by weight of PVDF 3 and b) lO % by weight of P4 The preparation of the mixtures was carried out in a twin-screw compounder at a composition temperature of 260C.

Production of the multilayer pipes according to the Examples 1 to 12 and Comparative Examples A to G (see Table) The pipes were produced on a laboratory extrusion facil-ity using a five-layer die (in the production of the two-, three- and four-layer pipes, the channels not required remain closed). The barrel temperatures were 230C (PA 1, PA 2, PA 3); 2S0C (PVDF 1, PVDF 2, PVDF 3, Z 1 to Z 7) and 280C (PA 4, PA 5).

The tubes produced had an external diameter of 8 mm and a total wall thickness of 1 mm.

2I4525~
- 19 - O.Z. 4834 Table 2: Experiments not according to the invention Experiment Composition of Diffusion Mechanically separable layers from [g/(d m2)] at the interfaces outside to at 60C
inside after after storage storage at 23C in fuel~

A PA 1 (1.0 mm) 600 ***) t**) (single-layer pipe) B PA 2 (1.0 mm) 410 ***) t** ) (single-layer pipe) C PA 1 (0.9 mm) 30 yes yes PVDF 1 (0.1 mm) D PA 2 (0.9 mm) **) yes yes 2 1 (0.1 mm) E PA 2 (0.8 mm) 30 yes yes Z 1 (0.1 mm) (PA 2 from (PA 2 from PVDF 1 (0.1 mm) Z 1) Z 1) F PA 3 (0.9 mm) **~ yes yes Z 2 (0.1 mm) G PA 4 (0.9 mm) **) yes yes Z 3 (0.1 mm) *) Storage at 23C for 20 days in standard fuel M 15 (42. 5% by volume of isooctane, 42.5% by volume of toluene and 15% by volume of methanol) **) Diffusion was not determined.
***) Single-layer pipe; there is no interface.

214525~
-- 20 - O.Z. 4834 Table 3: Experiments accordinq to the invention Experiment Composition ofDiffusion Mechanically separable layers from[g/(d m2)] at the interfaces outside to at 60C
inside after after storage storage at 23C in fuel*

1 PA 1 (0-8 mm) 40 no no Z 5 (0.2 mm) Z PA 1 (0.9 mm) 60 no no Z 6 (0.1 mm) 3 PA 2 ( 0 . 8 mm) < 30 no no Z 6 (0.1 mm) PVDF 1 (0.1 mm) 4 PA 2 (0.8 mm) 50 no no Z 6 (0.1 ~n) PVDF 3 (0.05 mm) PA 3 (0.9 mm) 75 no no Z 7 (0.1 mm) 6 PA 4 (0.8 mm) < 35 no no z 4 (0.1 mm) PVDF 2 (0.1 mm) 7 PA 2 ( 0 . 45 mm) 60 no no Z 6 (0.1 mm) PA 2 (0.45 mm) 21452~
- 21 - O.Z. 4834 Table 3: Experiments according to the invention (continuation) Experiment Composition ofDiffusion Mechanically separable*
layers from[g/(d m2)] at the interfaces outside to at 60C
inside after after storage storage at 23C in fuel~

8 PA 2 (0.45 mm) < 60 no no Z 6 (0.1 mm) PA 3 (0.4 mm) Z 7 (0.05 mm) 9 PA 1 (0.8 mm) 70 no no Z 5 (0.1 mm) PA 5 (0.1 mm) PA 2 (0.3 mm) < 60 no no Z 6 (0.05 mm) PA 2 (0.3 mm) Z 6 (0.05 mm) PA 2 (0.3 mm) 11 PA l (0.5 mm) 65 no no Z 5 (0.05 mm) PA 1 (0.3 mm) Z 5 (0.05 mm) PA 5 (0.1 mm) 12 z 6 (O.2 mm) 60 no no PA 3 (0.8 mm) *) Storage at 23C for 20 days in standard fuel M 15 (42.5 % by volume of isooctane, 42.5% by volume of toluene and 15% by volume of methanol)

Claims

1. Multilayer plastic pipe, comprising at least of I. a layer based on a moulding composition of poly-amide, and II. a layer adjacent to layer I and based on a moulding composition comprising a mixture of a) from 97.5 to 50% by weight of polyvinylidene fluoride and b) from 2.5 to 50% by weight of an acrylate copolymer, with the layers adhering to one another and the acrylate copolymer of the component II b) containing at least the follow-ing basic building blocks:
i) from 14 to 85% by weight of ii) from 0 to 75% by weight of iii) from 0 to 15% by weight of iv) from 7 to 20% by weight of where m = 0 or 1, Alkyl = methyl, ethyl, propyl, butyl, pentyl, hexyl and R1 to R5 = H or (CnH2n+1) with n = 1 to 6 and can be identical or different.

2. Multilayer plastic pipe according to claim 1, wherein layer II comprises a moulding composition of a mixture comprising a) from 97.5 to 80% by weight of polyvinylidene fluoride and b) from 2.5 to 20% by weight of acrylate copolymer.

3. Multilayer plastic pipe according to claim 1, wherein layer II comprises a moulding composition of a mixture comprising a) from 96 to 90% by weight of polyvinylidene fluoride and b) from 4 to 10% by weight of acrylate copolymer.

4. Multilayer plastic pipe according to claim 1, wherein component II b) contains the following basic building blocks:
i) from 35 to 70% by weight of ii) from 10 to 75% by weight, preferably from 20 to 40% by weight, of iii) from 0 to 15% by weight of iv) from 8 to 12% by weight of where m = 0 or 1, Alkyl = methyl, ethyl, propyl, butyl, pentyl, hexyl and R1 to R5 = H or (CnH2n+1) with n = 1 to 6 and can be identical or different.

5. Multilayer plastic pipe according to claim 4, wherein m = 1.

6. Multilayer plastic pipe according to any one of claims 1 to 5, wherein layer I comprises a moulding composition based on polyamide 12.

7. Multilayer plastic pipe according to any one of claims 1 to 5, wherein both Alkyl and R1 to R5 are methyl groups.

8. Multilayer plastic pipe according to any one of claims 1 to 5, wherein component II a) contains a vinylidene fluoride copolymer.

9. Multilayer plastic pipe according to any one of claims 1 to 5, wherein layer I or layer II has been made electrically conductive and has a surface resistance of less than 109.OMEGA..

10. Multilayer plastic pipe according to any one of claims 1 to 5, wherein component II a) contains a polyvinylidene fluoride having a melt flow index of less than 17 g/10 min.

11. Multilayer plastic pipe according to any one of claims 1 to 5 wherein component II a) contains a polyvinylidene fluoride having a melt flow index of from 2 to 13 g/10 min.

12. Multilayer plastic pipe according to any one of claims 1 to 5, wherein said pipe contains more than one layer I
or it contains more than one layer II.

13. Multilayer plastic pipe according to any one of claims 1 to 5, wherein said pipe contains further layers compris-ing polyvinylidene fluoride which are adjacent to layer II, but not to layer I.

14. Multilayer plastic pipe according to claim 13, wherein the further layers comprising polyvinylidene fluoride have been made electrically conductive and have a surface resistance of less than 109.OMEGA..

15. Multilayer plastic pipe according to any one of claims 1 to 5, wherein the innermost layer has been made electrically conductive and has a surface resistance of less than 109.OMEGA..

16. Multilayer plastic pipe according to any one of claims 1 to 5, wherein in addition to the layers I and II, it contains a. at least one layer based on a polyolefin and b. at least one layer based on a conventional coupling agent for bonds between polyolefin and polyamide, arranged in such a way that the layer based on the coupling agent (b) lies directly between the layer I and the layer based on the polyolefin (a).

17. Use of the multilayer plastic pipe according to any one of claims 1 to 5 for the transport of (petro)chemical materials.

18. Use of the multilayer plastic pipe according to any one of claims 1 to 5 in the motor vehicle sector for conveying brake, cooling and hydraulic fluids and also fuel.

19. Use of the multilayer plastic pipe according to any one of claims 1 to 5 for manufacturing hollow bodies.

20. Use of the multilayer plastic pipe according to any one of claims 1 to 5 for manufacturing filling ports or tanks in the motor vehicle sector.