JP2004256096A - Fuel tank with a multilayer structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plastic fuel tank with a multilayer wall structure having a barrier layer with considerably low leakage of hydrocarbon. <P>SOLUTION: The fuel tank comprises a tank wall constituting the inner side of the fuel tank, a barrier layer, and at least one structure layer surrounding the barrier layer. The tank wall has an inner wall facing the inner side of the fuel tank and made of a mixture of polyamide and polyolefin. The barrier layer generally surrounds the inner wall. Preferably, the tank wall is formed of multilayer parison, and formed into a final shape by blow-molding. The tank wall has a pinch line in an area where the parison is closed during the blow-molding. In the inner wall, a part of the inner wall is engaged with another part of the inner wall to clamp the parison, so that a continuous interior layer of the tank wall is formed to not have a penetration hole. An adhesive layer is provided between the barrier layer and the structure layer. A damper layer is provided between the interior layer and the barrier layer. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a fuel tank for an automobile, and more particularly to a fuel tank made of a multilayer plastic.

  The original U.S. application to which this application claims priority is a continuation-in-part of U.S. patent application Ser. No. 09 / 782,485, filed on Feb. 13, 2001.

  European Patent EP 742236 describes a gasoline tank comprising the following five layers.

High-density polyethylene (HDPE) layer Binder layer Polyamide (PA) or a copolymer (EVOH) containing ethylene units and vinyl alcohol units Binder layer HDPE layer

  A sixth layer can be added between the layer consisting of the binder and the layer consisting of HDPE. This sixth layer is made up of scrap from the manufacturing that comes with forming the tank. Scrap is very small in complex tanks. These scraps and complex tanks are then milled until granules are obtained. The ground material is then melted again and extruded directly in a tank coextrusion plant. The pulverized material may be melted and re-granulated by an extruder such as a twin screw extruder before being reused.

  In another example, the recycled product can be mixed with HDPE from the two extreme layers of the tank. For example, virgin HDPE granules and recycled product granules can be mixed. These two recycled products can be used in combination. Recycled material can be up to 50% of the total weight of the tank.

  EP 731308 describes a tube comprising an inner layer consisting of a mixture of polyamide and a polyolefin having a matrix of polyamide, and an outer layer consisting of polyamide. These pipes based on polyamide are used to transport gasoline, especially for transporting gasoline from a car tank to a car, and, although not of a larger diameter, between the dispensing pump and the underground storage tank. Useful for transferring hydrocarbon fuel in stands.

  In another form of tube, a layer of a polymer of ethylene units and vinyl alcohol units (EVOH) may be placed between the inner and outer layers. A structure consisting of an inner layer / EVOH / outer layer is advantageously used.

  The tanks described in EP 742 236, which do not have a barrier layer in direct contact with gasoline, have in fact barrier properties, but they are not sufficient if it is desired to have very low gasoline leakage. . EP 731308 describes a tube in which the outer layer is made of polyamide and the barrier layer is in direct contact with gasoline, and this layer made of polyamide has a mechanical strength of the assembly. Is necessary for A novel structure having excellent barrier properties and useful for various articles, such as gasoline tanks for automobiles, has now been found.

  SUMMARY OF THE INVENTION The present invention relates to a plastic fuel tank having a multilayer wall structure, wherein the barrier layer forms the exposed surface of the wall and is preferably in direct contact with the fuel being filled in the tank. The barrier layer of the structure of the invention constitutes one of the exposed surfaces of the structure, ie it is not the inner layer of the wall structure. A fuel tank structure embodying the present invention has HDPE / barrier layer or HDPE / binder / barrier layer walls. In addition, "HDPE" represents high density polyethylene.

Preferably, the structure of the fuel tank comprises the following layers in sequence:
A first layer made of high density polyethylene (HDPE),
A layer comprising a binder,
A second layer of EVOH or a mixture based on EVOH; and
Optionally, a third layer comprising polyamide (A) or a mixture of polyamide (A) and polyolefin (B).

  Hereinafter, in this specification, the second layer or a combination of the second layer and the third layer is referred to as a “barrier layer” and forms the outer surface of the wall structure.

  The present invention is particularly suitable for fluids such as automotive gasoline or volatile hydrocarbon fuels by virtue of a structure that avoids permeation and does not pollute the environment.

  It is an object, feature and advantage of the present invention that it has a significantly lower emission of hydrocarbon-based fuels, can easily meet stringent environmental protection standards and demands, is composed of economical manufacturing methods and assemblies, and has a long useful life. Providing a plastic fuel tank having a long life.

  These and other objects, features, and advantages of the present invention will become apparent from the following detailed description of the best mode, the appended claims, and the accompanying drawings.

  Referring now to the drawings in more detail, FIG. 1 shows a plastic fuel tank 10 for an automobile embodying the present invention. The tank wall 12 has a flanged plastic refueling neck or pipe 14 that is heat welded to the wall, and a fuel pump module 18 with a cover flange 20. As shown in FIG. 2, the wall 12 includes a first layer 22 of exposed outer HDPE, a second layer 24 of inner exposed EVOH, and a combination of the first and second layers. Adhesive has a binder layer 26 between them. The second layer 24 is in contact with the liquid fuel in the tank 10 and mainly serves as a vapor barrier, and the first layer 22 functions mainly on the strength and structural hardness of the tank. The adhesive layer bonds or adheres the different first and second layers.

  FIG. 3 shows an inner first layer 22 of HDPE, an outer exposed second layer 24 of EVOH, and a binder layer between them that adheres the first and second layers together. 26 shows the structure of the modified wall 12 ′ of the fuel tank 10 having 26. In both forms of the tank, the second vapor barrier layer 26 of EVOH also has a third film or layer 28 of polyamide (A) or a mixture of polyamide (A) and polyolefin (B). Is preferred.

  Preferably, the fuel tank 10 extrudes all layers simultaneously and then adheres together to a hollow parison placed in a mold having a cavity having the desired shape and profile of the tank, and blows the parison into the fuel tank. It is formed by forming into.

  The first layer 22 is high density polyethylene (HDPE), which may also have carbon black or polyblack mixed therein for coloring, and re-ground scrap material from the manufacture of the fuel tank 10 And / or a re-ground layer of HDPE composed of recovered and re-ground HDPE. Preferably, the first layer 22 and the reground layer are of substantially the same composition. The adhesive layer can be composed of a variety of materials and is necessary for applying a layer of HDPE to the second layer of the vapor barrier, thereby passing various breakdown resistance specifications in the automotive industry The required structural integrity of the fuel tank 10 is increased. The second vapor barrier layer is necessary to reduce the amount of hydrocarbon vapors that escape or escape through the wall 12 of the fuel tank, which is primarily composed of HDPE.

  Typical multilayer plastic fuel tank walls 10 have a thickness of about 3 mm to 10 mm, with an optimal total wall thickness being about 5 to 6 mm. Typical values for the individual layers in the multi-layer plastic fuel tank 10 are as follows. The first layer 22 comprises about 90-97% of the total wall thickness. The binder or adhesive layer 26 comprises about 1-4% of the total wall thickness. And, the second layer 24 or the second and third layers 24, 28 of the vapor barrier make up about 2-6% of the total wall thickness. These ranges of thicknesses for the individual layers are merely exemplary and can be easily modified in the manufacture of the fuel tank 10 when co-extruding a parison for the fuel tank wall 12.

  During production operation of the fuel tank 10, the thickness of the individual layers must be controlled to ensure optimal performance and quality of the fuel tank 10 used. The thickness of the first layer 22 of polyethylene is important because it provides structural protection to the vapor barrier layers 24, 28 and also provides the strength and structural integrity of the fuel tank 10 itself. It is. The thickness of the adhesive layer 26 is important to ensure sufficient adhesion between the adjacent layer of HDPE and the vapor barrier layers 24,28. Finally, the thickness of the vapor barrier layers 24, 28 is important to prevent hydrocarbon vapors from permeating through the fuel tank 10 into the atmosphere.

  With respect to the first layer, high density polyethylene (HDPE) is described in Kirk-Othmer, 4th Edition, Vol. 17, 704 and 724-725. According to ASTM D 1248-84, it is an ethylene polymer having a density at least equal to 0.940. The designation HDPE relates to both ethylene homopolymers and ethylene-based copolymers with small proportions of olefins. The density is preferably between 0.940 and 0.965. In the present invention, the MFI of HDPE is preferably 0.1 to 50. Examples are Eltex B 2008® with a density of 0.958 and an MFI of 0.9 (in g / 10 min, at 190 ° C. under 2.16 kg), FINATHENE® MS201B from FINA, and Lupolen® 4261 AQ from BASF may be mentioned.

  With respect to the second layer, the EVOH copolymer is also called a saponified ethylene-vinyl acetate copolymer. The saponified ethylene-vinyl acetate copolymer which can be used according to the present invention is a copolymer having an ethylene content of 20 to 70 mol%, preferably 25 to 70 mol%, and the degree of saponification of the vinyl acetate component is 95 mol% or more. It is. If the ethylene content is less than 20 mol%, the barrier properties under conditions of high humidity are not as high as desired, whereas if the ethylene content exceeds 70 mol%, the barrier properties deteriorate. If the degree of saponification or hydrolysis is less than 95 mol%, the barrier properties are sacrificed.

  The expression "barrier properties" means impervious to gases, liquids, especially oxygen, and gasoline for motor vehicles. The present invention more particularly relates to a barrier property against volatile hydrocarbon hydrocarbon fuels such as gasoline or gasoline for automobiles.

  Of these saponified copolymers, those having a melt flow index in the range of 0.5 to 100 g / 10 minutes under hot conditions are particularly useful. Preferably, the MFI is selected between 5 and 30 (g / 10 min, 230 ° C, under 2.16 kg). Note that the abbreviation of “MFI”, that is, “melt flow index” indicates a flow velocity in a molten state.

  The saponified copolymer includes α-olefins such as propylene, isobutene, α-octene, α-dodecene, α-octadecene, unsaturated carboxylic acids or salts thereof, partial alkyl esters of the acids, and complete alkyl esters. , Nitriles, amides and anhydrides, and other comonomer components, such as unsaturated sulfonic acids or salts thereof, in small proportions.

  As regards the mixtures based on EVOH, they are such that the EVOH forms a matrix, ie it is at least 40% by weight, preferably at least 50% by weight in the mixture. Other components of the mixture are selected from polyolefins, polyamides, and any functional polymers.

As a first example of these mixtures based on EVOH of the second layer, mention may be made of a composition (by weight) consisting of:
-55 to 99.5 parts of EVOH copolymer-0.5 to 45 parts of polypropylene and compatibilizer, wherein the ratio thereof is such that the ratio of the amount of polypropylene to the amount of compatibilizer is 1 to 5. It is.

  Preferably, the ratio of EVOH MFI to polypropylene MFI is greater than 5, more preferably 5-25. Preferably, the MFI of the polypropylene is 0.5-3 (g / 10 min, 230 ° C, under 2.16 kg). According to one advantageous form, the compatibilizer is a polyethylene having a polyamide graft, which is (i) a copolymer of ethylene and a grafted or copolymerized unsaturated monomer X. And (ii) a reaction with a polyamide. The copolymer of ethylene and the grafted or copolymerized unsaturated monomer X is a copolymer of X, which is an ethylene-maleic anhydride copolymer and an ethylene-alkyl (meth) Copolymers such as can be selected from acrylic acid esters-maleic anhydride, these copolymers comprising 0.2 to 10% by weight of maleic anhydride and 0 to 40% by weight of alkyl (meth) acrylic acid esters %. According to another advantageous embodiment, the compatibilizer is obtained by reacting (i) a propylene homopolymer or a copolymer consisting of a grafted or copolymerized unsaturated monomer X and (ii) a polyamide. And a polypropylene having a polyamide graft. Preferably, X is grafted. The monomer X is preferably an anhydride of an unsaturated carboxylic acid such as, for example, maleic anhydride.

As a second example of these mixtures based on EVOH of the second layer, a composition consisting of:
EVOH copolymer 50 to 98% by weight
1-50% by weight of polyethylene
A compatibilizer comprising a mixture of a polymer selected from LLDPE polyethylene or a metallocene, and a polymer selected from an elastomer, a very low density polyethylene and a metallocene polyethylene, wherein the mixture is an unsaturated carboxylic acid or a functional derivative of this acid. 1-15% by weight of compatibilizer co-grafted with

Preferably, this phase dosage, the ratio of the MFI ₁₀ / MFI ₂ is between 5 and 20. MFI ₂ is a mass melt flow index measured at 190 ° C. under a load of 2.16 kg according to ASTM D 1238, and MFI ₁₀ is compliant with ASTM D 1238 at 190 ° C. under a load of 10 kg. Is a mass melt flow index measured.

A third example of these mixtures based on EVOH in the second layer may include a composition consisting of:
50 to 98% by weight of an EVOH copolymer,
1 to 50% by weight of an ethylene-alkyl (meth) acrylate copolymer,
1 to 15% by weight of a compatibilizer formed by the reaction of (i) a copolymer of ethylene and a grafted or copolymerized unsaturated monomer X and (ii) a copolyamide.

  Preferably, the copolymer of ethylene and the grafted or copolymerized unsaturated monomer X is a copolymer of X, which is a copolymer of ethylene and maleic anhydride, or ethylene, It is a copolymer comprising a copolymer of an alkyl (meth) acrylate and maleic anhydride. Preferably, these copolymers comprise from 0.2 to 10% by weight of maleic anhydride and from 0 to 40% by weight of alkyl (meth) acrylate.

With respect to the third layer of polyamide (A) and mixtures of polyamide (A) and polyolefin (B), the term "polyamide" means the product of the following condensation.
One or more amino acids, such as aminocaproic acid, 7-aminoheptanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid, of one or more lactams, such as caprolactam, enanthol lactam and lauryl lactam;
-Diacids such as isophthalic acid, terephthalic acid, adipic acid, azelaic acid, suberic acid, sebacic acid, and dodecanedicarboxylic acid, and hexamethylenediamine, dodecamethylenediamine, meta-xylenediamine, bis (p-aminocyclohexyl) methane And one or more salts or mixtures of diamines such as trimethylhexamethylenediamine

  Examples of polyamides may include PA6 and PA6-6. It is also advantageously possible to use copolyamides. Copolyamides resulting from the condensation of at least two α, ω-aminocarboxylic acids, or two lactams, or one lactam and one α, ω-aminocarboxylic acid may be mentioned. Copolyamides resulting from the condensation of at least one α, ω-aminocarboxylic acid (or lactam), at least one diamine and at least one dicarboxylic acid may also be mentioned.

  Examples of lactams may include lactams having from 3 to 12 carbon atoms on the main ring, which may be substituted. For example, β, β-dimethylpropiolactam, α, α-dimethylpropiolactam, amylolactam, caprolactam, caprylactam, lauryllactam, and the like can be mentioned.

Examples of α, ω-aminocarboxylic acids include aminoundecanoic acid and aminododecanoic acid. Examples of dicarboxylic acids include sodium or lithium salts of adipic acid, sebacic acid, isophthalic acid, butanedioic acid, 1,4-cyclohexanedicarboxylic acid, terephthalic acid, sulfoisophthalic acid, dimerized fatty acids (these dimerized fatty acids). dimer content of the fatty acid is at least 98%, preferably hydrogenated) and, HOOC- dodecanedioic acid (CH _{2) 10} -COOH and the like can be mentioned.

  The diamine can be an aliphatic diamine having 6 to 12 atoms and can be an aryl and / or saturated ring. Examples include hexamethylenediamine, piperazine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, 1,5-diaminohexane, 2,2,4-trimethyl-1,6-diaminohexane, diamine Polyol, isophoronediamine (IPD), methylpentamethylenediamine (MPDM), bis (aminocyclohexyl) methane (BACM), bis (3-methyl-4-aminocyclohexyl) methane (BMACM) and the like can be mentioned.

  Examples of copolyamides include copolymers of caprolactam and lauryl lactam (PA6 / 12), copolymers of caprolactam, adipic acid and hexamethylenediamine (PA6 / 6-6), caprolactam, lauryl lactam, adipic acid and hexamethylene Diamine copolymer (PA6 / 12 / 6-6), caprolactam, lauryl lactam, 11-aminoundecanoic acid, azelaic acid and hexamethylenediamine copolymer (PA6 / 6-9 / 11/12), caprolactam, Copolymers of lauryl lactam, 11-aminoundecanoic acid, adipic acid and hexamethylene diamine (PA6 / 6-6 / 11/12), and copolymers of lauryl lactam, azelaic acid and hexamethylene diamine (PA6-9) / 12) and the like.

  Preferably, the copolyamide is selected from PA6 / 12 and PA6 / 6-6. The advantage of these copolyamides is that their melting points are lower than PA6.

  An amorphous polyamide having no melting point can also be used.

  The MFI of the polyamide of the present invention and the mixture of the polyamide and the polyolefin is measured at a temperature of 15 to 20 ° C above the melting point of the polyamide according to the rules of the art. For mixtures based on PA6, the MFI is measured at 235 ° C. under 2.16 kg. For mixtures based on PA6-6, the MFI is measured at 275 ° C. under 1 kg.

  Mixtures of polyamides may be used. Preferably, the MFI of the polyamide is between 1 and 50 g / 10 min.

  Replacing some of the polyamide (A) with a copolymer containing polyamide blocks and polyether blocks, ie, from at least one of the above polyamides and at least one copolymer containing polyamide blocks and polyether blocks. Use of such a mixture would not depart from the scope of the present invention.

Copolymers containing polyamide blocks and polyether blocks result from the copolycondensation of reactive end-containing polyamide sequences with reactive end-containing polyether sequences, in particular:
1) Polyoxyalkylene sequences with dicarboxylic acid chain ends and polyamide sequences with diamine chain ends 2) Cyanoethylation and hydrogenation of α, ω-dihydroxylated aliphatic polyoxyalkylene sequences known as polyether diols Polyoxyalkylene sequence having diamine chain ends obtained by addition 3) Polyamide sequence having dicarboxylic acid chain ends Polyamide diol having dicarboxylic acid chain ends and polyamide sequence having dicarboxylic acid chain ends, and the obtained product is in this specific case. Is a polyetheresteramide. These copolymers are advantageously used.

  Polyamide sequences having dicarboxylic acid chain ends result, for example, from the condensation of α, ω-aminocarboxylic acids, lactams or dicarboxylic acids and diamines in the presence of chain-limiting dicarboxylic acids.

  The polyether can be, for example, polyethylene glycol (PEG), polypropylene glycol (PPG), or polytetramethylene glycol (PTMG). The latter is also known as polytetrahydrofuran (PTHF).

The number average molar mass _Mn of the polyamide sequence is from 300 to 15000, preferably from 600 to 5000. The mass _{Mn of the} polyether sequence is between 100 and 6000, preferably between 200 and 3000.

  The polymer having a polyamide block and a polyether block may also consist of randomly arranged units. These polymers can be prepared by the simultaneous reaction of a polyether and a polyamide block precursor.

  For example, it is possible to react a polyether diol, a lactam (or an α, ω-amino acid) and a chain-limiting diacid in the presence of a small amount of water. Polymers are obtained which essentially have polyether blocks, polyamide blocks of very variable length, but also have various reagents, which react randomly and are arranged randomly along the polymer chain.

  Regardless of whether they result from the copolycondensation of a previously prepared polyamide with a polyether sequence or from a one-step reaction, these polymers having polyamide and polyether blocks are, for example, 20 It has a Shore D hardness of ~ 75, preferably 30-70, and an intrinsic viscosity of 0.8-2.5 measured in meta-cresol at 250 ° C at an initial concentration of 0.8 g / 100 ml. The MFI value can be between 5 and 50 (235 ° C. under 1 kg load).

  The polyether diol blocks are co-polycondensed with polyamide blocks having carboxylic acid ends or aminated such that they are converted to polyether diamines and condensed with polyamide blocks having carboxylic acid ends. Or used as either one. They can also be mixed with polyamide precursors and chain-limiting agents to produce polymers containing polyamide blocks and polyether blocks with randomly arranged units.

  Polymers having a polyamide block and a polyether block are described in U.S. Pat. Nos. 4,331,786, 4,115,475, 4,195,015, 4,839,441, 4,864,014 and 4,864,014. No. 4,230,838 and 4,332,920.

  The ratio of the amount of the copolymer having the polyamide block and the polyether block to the amount of the polyamide is preferably from 10/90 to 60/40 on a weight basis. For example, a mixture of (i) PA6 and (ii) a copolymer containing a PA6 block and a PTMG block, and (i) PA6 and (ii) a copolymer containing a PA12 block and a PTMG block. And the like.

  As regards the polyolefin (B) of the mixture of polyamide (A) and polyolefin (B) in the third layer, it may or may not be functionalized, or it may have at least one functionality and / or at least one It may be a mixture of two non-functional. For simplicity, the functionalized polyolefin (B1) and the non-functionalized polyolefin (B2) are described below.

Unfunctionalized polyolefins (B2) are, on a regular basis, homopolymers or copolymers of α-olefins or diolefins, such as, for example, ethylene, propylene, 1-butene, 1-octene or butadiene. . By way of example, the following may be mentioned:
Polyethylene homopolymer and copolymer, particularly LDPE, HDPE, LLDPE (linear low density polyethylene), VLDPE (ultra low density polyethylene) and metallocene-based polyethylene Propylene homopolymer or copolymer Ethylene / propylene, EPR ( Ethylene / propylene-rubber), and ethylene / α-olefin copolymers such as ethylene / propylene / diene (EPDM) styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), A styrene / isoprene / styrene (SIS) or styrene / ethylene-propylene / styrene (SEPS) block copolymer; a salt or ester of an unsaturated carboxylic acid such as an alkyl (meth) acrylate (eg, methyl acrylate); Or It is selected from vinyl esters of saturated carboxylic acids vinyl acid, and at least one product, a copolymer of ethylene, Note that, as a percentage of the comonomers, it is possible up to 40 wt%.

  The functionalized polyolefin (B1) can be an α-olefin polymer containing reactive units (functional groups), such reactive units being acid, anhydride or epoxy functional groups. As an example, an unsaturated epoxide such as glycidyl (meth) acrylate, or a carboxylic acid such as (meth) acrylic acid or a corresponding salt or ester (in the latter case, a metal such as Zn is completely used). Or can be partially neutralized), or alternatively, grafted or binary or terpolymerized with an anhydride of a carboxylic acid such as maleic anhydride. (B2) may be mentioned. The functionalized polyolefin is, for example, a PE / EPR mixture, in which the weight ratio can vary within wide limits, for example from 40/60 to 90/10. The mixture is co-grafted with an unsaturated carboxylic acid, especially with maleic anhydride, with a grafting ratio of, for example, 0.01 to 5% by weight.

The functionalized polyolefin (B1) may be selected from the following (co) polymers grafted with maleic anhydride or glycidyl methacrylate. The graft ratio is, for example, 0.01 to 5% by weight:
PE, PP, for example, a copolymer of propylene, butene, hexene, or octene and ethylene containing 35 to 80% by weight of ethylene, ethylene / propylene copolymer, EPR (abbreviation of ethylene-propylene-rubber), and Ethylene / α-olefin copolymers such as ethylene / propylene / diene (EPDM) copolymers Styrene / ethylene-butene / styrene (SEBS), styrene / butadiene / styrene (SBS), styrene / isoprene / styrene (SIS) Or a styrene / ethylene-propylene / styrene (SEPS) block copolymer containing up to 40% by weight of vinyl acetate and an ethylene-vinyl acetate (EVA) copolymer containing up to 40% by weight of alkyl (meth) acrylate. Ethylene-alkyl (meth) acrylate A copolymer comonomers consisting of ether containing up to 40 wt%, ethylene - vinyl acetate (EVA), and an alkyl (meth) acrylate copolymer

  The functionalized polyolefins (B1) are also grafted with maleic anhydride and then condensed with monoaminopolyamides (or polyamide oligomers), containing mainly propylene, ethylene / propylene copolymers (EP-A- Products described in JP-A-0342066).

The functionalized polyolefin (B1) may also be a binary or ternary copolymer consisting of at least the following units: (1) ethylene, (2) alkyl (meth) acrylate or saturated carboxylate, and (3) anhydride such as maleic anhydride or (meth) acrylic acid, or glycidyl (meth) acrylate Examples of the latter type of functionalized polyolefin, to which epoxies can be mentioned, are the following copolymers: In the copolymer, ethylene is preferably at least 60% by weight, and in the copolymer, the ternary monomer (functional group) is, for example, 0.1 to 10% by weight of the copolymer. is there:
Ethylene / alkyl (meth) acrylate / (meth) acrylic acid or maleic anhydride or glycidyl methacrylate copolymer Ethylene / vinyl acetate / maleic anhydride or glycidyl methacrylate copolymer ethylene / vinyl acetate or alkyl (meth) acrylic acid Ester / (meth) acrylic acid or maleic anhydride or glycidyl methacrylate copolymer

  In the aforementioned copolymer, the (meth) acrylic acid may be salified with Zn or Li.

  The term “alkyl (meth) acrylate” in (B1) or (B2) represents C1 to C8 alkyl of methacrylic acid and acrylic acid, and is methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate , 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate and ethyl methacrylate.

  Moreover, the above-mentioned polyolefins (B1) may also be crosslinked by any suitable method or agent (diepoxy, diacid, peroxide, etc.). A `` functionalized polyolefin '' can also be a mixture of the above-described polyolefins with a difunctional reagent such as diacid, dianhydride, diepoxy, or at least difunctionalized, capable of reacting with the latter. Of polyolefins.

  The copolymers mentioned above, namely (B1) and (B2), can be copolymerized in a random or block manner and can have a linear or branched structure.

  The molecular weight, MFI index and density of these polyolefins can also vary within wide limits, as will be appreciated by those skilled in the art. MFI, abbreviation for melt flow index, is the flow velocity in the molten state. It is measured according to ASTM standard 1238.

  Preferably, the unfunctionalized polyolefin (B2) is a polypropylene homopolymer or copolymer, and a homopolymer or ethylene of ethylene and a higher α such as butene, hexene, octene or 4-methyl-1-pentene. -Selected from copolymers with olefin type comonomers. For example, PP, high-density PE, medium-density PE, linear low-density PE, low-density PE, and ultra-low-density PE may be used. It is known by those skilled in the art that these polyethylenes are produced by "radical-mediated" methods, by "Ziegler" type catalysts or, more recently, by so-called "metallocene" catalysts.

  Preferably, the functionalized polyolefin (B1) comprises any polymer consisting of α-olefin units and units having reactive polar functional groups such as epoxy, carboxylic acid or carboxylic anhydride functional groups. Selected. Examples of such polymers include terpolymers of ethylene, alkyl acrylate and maleic anhydride or glycidyl methacrylate, such as ELF Atochem S.A. A. Or a polyolefin grafted with maleic anhydride, such as ELF Atochem S.D. A. And terpolymers of ethylene, alkyl acrylate and (meth) acrylic acid. Polypropylene homopolymers or copolymers grafted with carboxylic anhydrides and then condensed with polyamide or monoaminopolyamide oligomers may also be mentioned.

  The MFI of (A) and the MFI of (B1) and (B2) can be selected from a wide range, but in order to facilitate the dispersion of (B), the MFI of (A) is It is recommended that it be larger.

  If the proportion of (B) is small, for example from 10 to 15 parts, it is sufficient to use an unfunctionalized polyolefin (B2). The ratio of (B2) and (B1) in phase (B) depends on the amount of functional groups present in (B1) and their reactivity. Preferably, a (B1) / (B2) weight ratio ranging from 5/35 to 15/25 is used. If the proportion of (B) is small, it is also possible to use only one mixture of polyolefins (B1) in order to obtain crosslinking.

  According to a first preferred embodiment of the present invention, the polyolefin (B) comprises (i) high-density polyethylene (HDPE) and (ii) polyethylene (C1), an elastomer, an ultra-low-density polyethylene and an ethylene-based copolymer. (C2), wherein the mixture (C1) + (C2) is co-grafted with an unsaturated carboxylic acid.

  According to a second preferred form of the invention, the polyolefin (B) is a copolymer of (i) polypropylene and (ii) propylene and a grafted or copolymerized unsaturated monomer X. It consists of a polyolefin produced by the reaction between (C3) and polyamide (C4).

  According to a third preferred form of the present invention, the polyolefin (B) comprises (i) LLDPE, VLDPE or metallocene-based polyethylene, and (ii) ethylene-alkyl (meth) acrylate-maleic anhydride copolymer. Consists of

  According to a fourth preferred form of the invention, the polyamide (A) comprises (i) a polyamide and a mixture consisting of (ii) a copolymer containing PA6 and PTMG blocks, and (i) a polyamide; , (Ii) a mixture comprising a copolymer containing a PA12 block and a PTMG block. The weight ratio of the copolymer to the polyamide is between 10/90 and 60/40.

  According to the first embodiment, the polyolefin (B) comprises (i) LLDPE, VLDPE or metallocene-based polyethylene, and (ii) an ethylene-alkyl (meth) acrylate-maleic anhydride copolymer. According to a second variant, the polyolefin consists of a bifunctionalized polymer containing at least 50 mol% of ethylene units, and it can react to form a crosslinked phase.

For the first form, the ratio is preferably as follows (by weight):
Polyamide 60-70%
5-15% of co-grafted mixture of (C1) and (C2)
The remainder is for high density polyethylene, for high density polyethylene, the density is preferably between 0.940 and 0.965 and the MFI is between 0.1 and 5 g / 10 min (190 ° C., 2.16 kg).

  Polyethylene (C1) may be selected from the polyethylenes mentioned above. Preferably, (C1) is a high density polyethylene (HDPE) having a density of 0.940 to 0.965. The MFI (2.16 kg, 190 ° C.) of (C1) is 0.1 to 3 g / 10 minutes.

  The copolymer (C2) can be, for example, an ethylene / propylene elastomer (EPR) or an ethylene / propylene / diene elastomer (EPDM). (C2) may also be a very low density polyethylene (VLDPE), which is either an ethylene homopolymer or a copolymer of ethylene and an α-olefin. (C2) also comprises (i) unsaturated carboxylic acids, their salts, their esters, (ii) vinyl esters of saturated carboxylic acids, (iii) unsaturated dicarboxylic acids, their salts, their esters, their esters. It may be a copolymer of ethylene and at least one product selected from hemiesters and anhydrides thereof. Preferably, (C2) is EPR.

  Preferably, 60 to 95 parts of (C1) are used for 40 to 5 parts of (C2).

  The mixture of (C1) and (C2) is grafted with an unsaturated carboxylic acid, ie (C1) and (C2) are cografted. The use of a functional derivative of this acid would not depart from the scope of the present invention. Examples of unsaturated carboxylic acids are carboxylic acids containing 2 to 20 carbon atoms, such as, for example, acrylic acid, methacrylic acid, maleic acid, fumaric acid or itaconic acid. The functional derivatives of these acids include, for example, anhydrides, ester derivatives, amide derivatives, imide derivatives of unsaturated carboxylic acids, and metal salts (such as alkali metal salts).

  Unsaturated dicarboxylic acids containing from 4 to 10 carbon atoms and their functional derivatives, especially their anhydrides, are grafting particularly preferred monomers. These grafted monomers include, for example, maleic acid, fumaric acid, itaconic acid, citraconic acid, allylsuccinic acid, 4-cyclohexene-1,2-dicarboxylic acid, 4-methyl-4-cyclohexene-1,2 -Dicarboxylic acid, bicyclo (2,2,1) hept-5-ene-2,3-dicarboxylic acid, x-methylbicyclo (2,2,1) hept-5-ene-2,3-dicarboxylic acid, anhydride Maleic acid, itaconic anhydride, citraconic anhydride, allyl succinic anhydride, 4-cyclohexene-1,2-dicarboxylic anhydride, 4-methylene-4-cyclohexene-1,2-dicarboxylic anhydride, bicyclo (2,2, 1) Consisting of hept-5-ene-2,3-dicarboxylic acid and x-methylbicyclo (2,2,1) hept-5-ene-2,2-dicarboxylic anhydrideMaleic anhydride is advantageously used.

  Various known methods can be used to graft the grafting monomer to the mixture consisting of (C1) and (C2). For example, this can be accomplished by heating the polymers (C1) and (C2) to an elevated temperature, about 150 to about 300 ° C., with or without a radical generator, in the presence or absence of a solvent. It can be carried out.

  In the mixture of (C1) and (C2) obtained by the above-mentioned method and modified by grafting, the amount of the grafted monomer can be selected by an appropriate method. It is preferably 0.01 to 10%, more preferably 600 ppm to 2%, based on the weight of (C1) and (C2). The amount of grafted monomer is measured by analyzing the succinic acid functionality by FTIR spectroscopy. The MFI of the co-grafted (C1) and (C2) is 5 to 30 g / 10 min (190 ° C., 2.16 kg), preferably 13 to 20 g / 10 min.

Preferably, the co-grafted mixture of (C1) and (C2) has an MFI ₁₀ / MFI ₂ ratio of greater than 18.5. Note that MFI ₁₀ represents the flow velocity at 190 ° C. under a load of 10 kg, and MFI ₂ represents the flow velocity under a load of 2.16 kg. Preferably, the co-grafted mixture of (C1) and (C2) has an MFI ₂₀ of less than 24. MFI ₂₀ represents the flow rate at 190 ° C. under a load of 21.6 kg.

For the second aspect of the invention, the ratio is preferably as follows (by weight):
Polyamide 60-70%
Polypropylene 20-30%
3 to 10% of a polyolefin formed by the reaction of a copolymer (C3) composed of propylene and a grafted or copolymerized unsaturated monomer X with a polyamide (C4)
The MFI of the polypropylene is preferably less than 0.5 g / 10 min (230 ° C., 2.16 kg), preferably 0.1-0.5. Such products are described in EP 647681. The grafted product of this second aspect of the invention is described herein.

  Starting with the preparation of (C3), it is either a copolymer of propylene and an unsaturated monomer X or a polypropylene onto which the unsaturated monomer X has been grafted. X is an unsaturated monomer that can be copolymerized with propylene or grafted onto polypropylene, which has a functional group that can react with the polyamide. The functional group can be, for example, a carboxylic acid, dicarboxylic anhydride or epoxide. Examples of the monomer X may include unsaturated epoxides such as (meth) acrylic acid, maleic anhydride, and glycidyl (meth) acrylate. Maleic anhydride is advantageously used. With respect to the polypropylene being grafted, X can be grafted onto a polypropylene alone or copolymer, such as an ethylene-propylene copolymer containing primarily (unit moles) propylene. Preferably, (C3) is one to which X is grafted. Grafting is an operation known per se.

(C4) is a polyamide or a polyamide oligomer. Polyamide oligomers are described in EP 342066 and FR 2291225. The polyamide (or oligomer) (C4) is the product of the condensation of monomers already mentioned above. Mixtures of polyamides may be used. PA-6, PA-11, PA12, copolyamides containing units 6 and 12 (PA-6 / 12) and copolyamides based on caprolactam, hexamethylenediamine and adipic acid (PA-6 / 6.6) ) Is advantageously used. The polyamide or oligomer (C4) may contain acid, amine or monoamine ends. In order for the polyamide to contain monoamine terminals, it is sufficient to use a chain-limiting agent of the general formula R ₁ -NHR ₂ . In the formula, R ₁ is hydrogen or a linear or branched alkyl group containing up to 20 carbon atoms. R ₂ is a group having up to 20 linear or branched alkyl or alkenyl carbon atoms, a saturated or unsaturated cycloaliphatic group, an aromatic group, or a combination of the above. The limiting agent may be, for example, laurylamine or oleylamine.

  Preferably, (C4) is PA-6, PA-11, or PA-12. The ratio by weight of C4 in C3 + C4 is preferably 0.1 to 60%. The reaction between (C4) and (C3) is preferably performed in a molten state. For example, (C3) and (C4) can be mixed in an extruder, typically at a temperature of 230-250C. The average residence time of the molten material in the extruder can be from 10 seconds to 3 minutes, preferably from 1 to 2 minutes.

For the third form, the ratio is preferably as follows (by weight):
Polyamide 60-70%
Ethylene-alkyl (meth) acrylate-maleic anhydride copolymer 5 to 15%
The remainder is LLDPE, VLDPE or metallocene-based polyethylene. Preferably, the density of the polyethylene is between 0.870 and 0.925, and the MFI is between 0.1 and 5 (190 ° C., 2.16 kg).

  Preferably, the ethylene-alkyl (meth) acrylate-maleic anhydride copolymer is from 0.2 to 10% by weight of maleic anhydride, up to 40% by weight of alkyl (meth) acrylate, preferably 5 to 40% by weight. %. Their MFI is 2-100 (190 ° C., 2.16 kg). Alkyl (meth) acrylates have already been mentioned above. The melting point is 80-120 ° C. These copolymers are commercially available. They are produced by radical-mediated polymerization at temperatures that can be between 200 and 2500 bar.

For the fourth embodiment, the ratio is preferably as follows (by weight).
According to a first variant,
60-70% of a mixture of a polyamide and a polymer containing a polyamide block and a polyether block
Ethylene-alkyl (meth) acrylate-maleic anhydride copolymer 5 to 15%
The remainder is LLDPE, VLDPE or metallocene-based polyethylene. Preferably, its density is between 0.870 and 0.925 and its MFI is between 0.1 and 5 (190 ° C., 2.16 kg).

  Preferably, the ethylene-alkyl (meth) acrylate-maleic anhydride copolymer is from 0.2 to 10% by weight of maleic anhydride, up to 40% by weight of alkyl (meth) acrylate, preferably 5 to 40% by weight. %. Their MFI is 2-100 (190 ° C., 2.16 kg). Alkyl (meth) acrylates have already been mentioned above. The melting point is 80-120 ° C. These copolymers are commercially available. They are produced by radical-mediated polymerization under pressures which can be between 200 and 2500 bar.

According to the second form,
40-95% of a mixture of polyamide and a polymer containing polyamide blocks and polyether blocks
Mixture of ethylene-alkyl (meth) acrylate-maleic anhydride copolymer and ethylene-alkyl (meth) acrylate-glycidyl methacrylate copolymer 60 to 5%
Copolymers with anhydrides are defined in the first aspect. The ethylene-alkyl (meth) acrylate-glycidyl methacrylate copolymer contains up to 40% by weight of alkyl (meth) acrylate, preferably 5 to 40%, and up to 10% by weight of unsaturated epoxide, preferably It may contain 0.1-8%. Preferably, the alkyl (meth) acrylate is selected from methyl (meth) acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate and 2-ethylhexyl acrylate. The amount of alkyl (meth) acrylate is preferably 20-35%. The MFI is preferably 5 to 100 (unit: g / 10 minutes, 190 ° C, 2.16 kg), and the melting point is 60 to 110 ° C. This copolymer can be obtained by radical-mediated polymerization of the monomers.

A catalyst may be added to facilitate the reaction between the epoxy and the anhydride functionality. Among the compounds that can facilitate the reaction between the epoxy function and the anhydride function, mention may in particular be made of:
Dimethyllaurylamine, dimethylstearylamine, N-butylmorpholine, N, N-dimethylcyclohexylamine, benzylmethylamine, pyridine, 4-dimethylaminopyridine, 1-methylimidazole, tetramethylethylhydrazine, N, N-dimethylpiperazine, Tertiary such as a mixture of tertiary amines containing 16 to 18 carbon atoms known as N, N, N ', N'-tetramethyl-1,6-hexanediamine, dimethyltallowamine Amine,
Tertiary phosphines such as triphenylphosphine alkyldithiocarbamate zinc acid

  Preparation of the mixture in the third layer can be carried out by mixing the various components together in the molten state in equipment commonly used in the thermoplastic polymer industry.

  The first layer may be composed of a layer of virgin HDPE and a layer of recycled polymer obtained from the scrap of transport or storage equipment or convenient equipment described in the prior art already mentioned. . This recycled layer is located on the binder layer side. Hereinafter, these two layers will be referred to by the term "first layer" for the sake of brevity.

  The thickness of the first layer may be between 2 and 10 mm, the thickness of the second layer may be between 30 and 500 μm, and the thickness of the third layer may be between 30 μm and 2 mm. The total thickness is usually 3 to 10 mm.

  A layer of a binder may also be placed between the second and third layers. Examples of binders may include the functionalized polyolefins (B1) described above. The binder between the first layer and the second layer and the binder between the second layer and the third layer may be the same or different. In the following description of the binder, the term "polyethylene" refers to both homopolymers and copolymers. Such products have been described previously in the third layer of polyolefin.

  As a first example of a binder, in the first preferred form of the third layer, mention may be made of the mixtures of (C1) and (C2) described above which are co-grafted.

As a second example of a binder, a mixture consisting of:
A polyethylene (D1) having a density of 0.910 to 0.940, and a polymer (D) itself composed of a mixture of a polymer (D2) selected from an elastomer, an ultra-low density polyethylene and a metallocene-based polyethylene. The mixture (D1) + (D2) comprises 5 to 30 parts of the polymer co-grafted with an unsaturated carboxylic acid and 95 to 70 parts of polyethylene (E) having a density of 0.910 to 0.930. The mixture consisting of (D) and (E)
Its density is 0.910 to 0.930,
The grafted unsaturated carboxylic acid has a content of 30 to 10000 ppm and an MFI (according to ASTM D1238, 190 ° C., 2.16 kg) of 0.1 to 3 g / 10 min. MFI stands for melt flow index.

  The density of this binder is preferably between 0.915 and 0.920. Preferably (D1) and (E) are LLDPE, preferably having the same comonomer. The comonomer may be selected from 1-hexene, 1-octene and 1-butene.

As a third example of a binder, a mixture consisting of:
A polymer (F1) composed of polyethylene (F1) having a density of 0.935 to 0.980 and a polymer (F2) selected from an elastomer, a very low-density polyethylene and an ethylene-based copolymer (F2) 5-30 parts of said polymer, wherein said mixture (F1) + (F2) is co-grafted with an unsaturated carboxylic acid;
Consisting of 95 to 70 parts of polyethylene (G) having a density of 0.930 to 0.950,
The mixture consisting of (F) and (G)
Its density is from 0.930 to 0.950, preferably from 0.930 to 0.940;
Those having a grafted unsaturated carboxylic acid content of 30 to 10000 ppm and an MFI (melt flow index) of 5 to 100 measured at 190 ° C. and 2.16 kg in accordance with ASTM D1238.

  As a fourth example of a binder, grafted with maleic anhydride, having an MFI of 0.1 to 3, a density of 0.920 to 0.930 and containing 2 to 40% by weight of n-decane insoluble matter at 90 ° C. Polyethylene. To determine the n-decane insolubles, the grafted polyethylene is dissolved in n-decane at 140 ° C, the solution is cooled to 90 ° C and the product precipitates. The mixture is then filtered and the insoluble content which precipitates out is% by weight and is collected by filtration at 90 ° C. When the content is 2 to 40%, the binder has excellent gasoline resistance.

  Preferably, the grafted polyethylene is diluted into ungrafted polyethylene and the binder is 2-30 parts of the grafted polyethylene having a density of 0.930-0.980 and a density of 0.910-0. 940, preferably 0.915 to 0.935, such as a mixture with 70 to 98 parts of ungrafted polyethylene.

As a fifth example of a binder, a mixture consisting of:
50-100 parts of polyethylene homopolymer or copolymer (J) having a density of 0.9 or more, polypropylene homopolymer or copolymer (K1), poly (1-butene) homopolymer or copolymer (K2) And the amount of a polymer (K) 0 to 50 parts (J) + (K) selected from a polystyrene homopolymer or a copolymer (K3) is 100 parts,
A mixture consisting of (J) + (K) is grafted with at least 0.5% by weight of a functional monomer,
The grafted mixture itself may comprise at least one polyethylene homopolymer or copolymer (L) or at least one polymer (M) of elastomeric nature or a mixture of (L) and (M). It is like being diluted.

  According to one aspect of the invention, (J) is LLDPE with a density of 0.91 to 0.930, the comonomer of which contains 4 to 8 carbon atoms. According to another aspect of the invention, (K) is HDPE, preferably having a density of at least 0.945, preferably a density of 0.950 to 0.980.

  Preferably, the functional monomer is maleic anhydride, the content of which is 1 to 5% by weight of (J) + (K).

  Preferably, (L) is LLDPE wherein the comonomer contains 4 to 8 carbon atoms, preferably its density is at least 0.9, preferably 0.910 to 0.930.

  Preferably, (L) or (M) or (L) + (M) is 97-75 parts for (J) + (K) 3-25 parts. The amount of (J) + (K) + (L) + (M) is 100 parts.

  A sixth example of a binder may include a mixture of polyethylene of HDPE, LLDPE, VLDPE or LDPE type, 5-35% of grafted metallocene-based polyethylene, and 0-35% of elastomer, for a total of 100%. .

As a seventh example of a binder, a mixture consisting of:
At least one polyethylene or ethylene-based copolymer, at least one polymer selected from polypropylene or propylene-based copolymer, poly (1-butene) homopolymer or copolymer, polystyrene homopolymer or copolymer, Preferably made of polypropylene,
The mixture is grafted with a functional monomer, the grafted mixture itself optionally being in at least one polyolefin, or in at least one polymer of elastomeric nature, or Are diluted in a mixture of In said mixture being grafted, the polyethylene is preferably at least 50% by weight of the mixture, preferably 60-90% by weight.

  Preferably, the functional monomer is selected from carboxylic acids and their derivatives, acid chlorides, isocyanates, oxazolines, epoxides, amines or hydroxides, preferably unsaturated dicarboxylic anhydrides.

As an eighth example of a binder, a mixture consisting of:
At least one LLDPE or VLDPE polyethylene consisting of at least one ethylene-based elastomer selected from ethylene-propylene copolymers and ethylene-butene copolymers,
This mixture of polyethylene and elastomer is grafted with an unsaturated carboxylic acid or a functional derivative of this acid,
The cografted mixture is optionally diluted in a polymer selected from a polyethylene homopolymer or copolymer, and a styrene block copolymer,
The binder has the following.
(A) the ethylene content is 70 mol% or more; (b) the content of the carboxylic acid or its derivative is 0.01 to 10% by weight of the binder, and
(C) The ratio of MFI ₁₀ / MFI ₂ is 5 to 20. MFI ₂ is a mass melt flow index measured at 190 ° C. under a load of 2.16 kg according to ASTM D1238, and MFI ₁₀ is a mass based on ASTM D1238 at 190 ° C. under a load of 10 kg. It is a melt flow index.

  The various layers in the structure of the present invention, including the layer comprising the binder, may also contain at least one additive selected from:

Filler (mineral filler, refractory filler, etc.)
Fiber Dye Pigment Optical brightener Antioxidant UV stabilizer

Specific examples The following products were used.
EVOH D: An ethylene-vinyl alcohol copolymer containing 29 mol% of ethylene, MFI8 (210 ° C, 2.16 kg), melting point 188 ° C, crystallization temperature 163 ° C, Tg (glass transition temperature) 62 ° C.

A mixture of polyamide and polyolefin for a third layer, known as ORGALLOY®, was prepared and made from the following product.
Polyamide (A)
PA1: medium viscosity copolyamide 6 / 6-6 having a melting point of 196 ° C. and a flow index of 4.4 g / 10 min according to ASTM 1238 at 235 ° C. under 1 kg weight
PA2: Medium viscosity copolyamide 6 / 6-6 having a melting point of 196 ° C. and a flow index of 6.6 g / 10 min according to ASTM 1238 at 235 ° C. under 1 kg weight.
Polyolefin (B2)
LLDPE: linear low-density polyethylene having a density according to ISO1872 / 1 of 0.920 kg / l and a flow index of 1 g / 10 min according to ASTM 1238 at 190 ° C. under a weight of 2.16 kg HDPE: ISO1872 / 1 High density polyethylene polyolefin (B1) having a density of 0.952 kg / l and a weight of 2.16 kg at 190 ° C. and a flow index of 0.4 g / 10 min according to ASTM 1238 (B1)
B1-1: This is a carrier PE containing 3000 ppm of maleic anhydride and having a flow index of 1 g / 10 min according to ASTM 1238 at 190 ° C. under a weight of 2.16 kg.
Antioxidant Anti1: Antioxidant of hindered phenol type Anti2: Second antioxidant of phosphite type

  The copolyamide, polyolefin and functional polyolefin are obtained from three independent gravimetric devices (or by simply drying-premixing the various granules), 40 mm in diameter, L / D = 40 (9 sleeves + 4 struts, That is, the Werner-Pfleiderer (total length of 10 sleeves) is introduced into the hopper of the co-rotating twin-screw extruder. The total flow rate of the extruder is 50 kg / h, the screw rotation speed is 150 rpm, the sleeves 3/4, 6/7 and 7/8 and the temperature of the material at the exit of the die is The extruded rods, each at 245, 263, 265 and 276 ° C., are granulated and then dried in an oven under vacuum at 80 ° C. for 8 hours. The compositions are given in Table 1 below (ratio by weight).

ORGALLOY® 1: a mixture of polyamide 6 and a polyolefin corresponding to the third preferred form of the third layer, consisting of:
PA6 65 parts MFI is 0.9 g / 10 min, density is 0.920, linear low-density polyethylene is 25 parts by weight, 91/6/3, and MFI is 5 (190 ° C., 2 .16 kg) of a binder composed of 10 parts of a copolymer composed of ethylene, butyl acrylate, and maleic anhydride, which is referred to as a binder 2a to a binder 2d. The details are given in Table 2 below.

Second Preferred Embodiment As clearly shown in FIG. 4, a multi-layer plastic fuel tank 50 has a tank wall 52, which comprises six layers made of a polymer material. Starting from the outside of the tank and proceeding inward, the fuel tank comprises an outer layer 54, preferably made of HDPE, an intermediate layer 56, preferably made of recycled or recycled material, an adhesive layer 58, and a barrier layer 60 made of EVOH. And an inner layer 64. The inner layer 64 is a polyamide, or a mixture of a polyamide and a polyolefin, or an alloy such as ORGALLOY®. The alloy may then have the aforementioned components. Similarly, the HDPE layer, the reclaimed material layer, the adhesive layer, the damper layer, and the EVOH layer may have the above-mentioned composition.

  The HDPE may be FINATHENE® MS201 having a specific gravity of about 0.950. Each of the adhesive layer 58 and the damper layer 62 may be maleic anhydride linear low density polyethylene sold under OREVAC® 18334. Barrier layer 60 may be an EVOH copolymer. Such a copolymer is sold under the name SOARNOL® DT2903 and is even distributed by ATFINA in Europe and SOARUS in the United States.

  The intermediate layer 56 is made of a recovered, crushed and recycled material or a scrap material, and is a mixture of various materials, and forms the fuel tank 50. Optionally, the reclaimed material is not an ORGALLOY® matrix because the regrind is diluted with HDPE to maintain compatibility with the HDPE outer layer 54. Conveniently, when the regrind is diluted, extra regrind is made, which is used elsewhere, for example, in various housings, support members, or other members. In that case, a matrix based on ORGALLOY or nylon is effective and increases resistance to hydrocarbon vapor permeation.

  The damper layer 62 is provided between the barrier layer 60 and the inner layer 64 to increase the rigidity of the fuel tank and to withstand various impact tests known in the art. Although not required, the damper layer 62 may be made of the same material as the adhesive layer 58 and serve as an adhesive between the ORGALLOY layer and the EVOH layer so that they can be easily bonded. The direct coupling of the ORGALLOY layer and the EVOH layer, at least in some designs, reduces the rigidity of the fuel tank. The ORGALLOY layer does not dissipate the impact energy sufficiently and does not protect the relatively brittle thin EVOH layer. Therefore, the damper layer is provided between the ORGALLOY layer and the EVOH layer to absorb impact energy and increase the rigidity of the fuel tank against impact and collision.

  To facilitate compatibility with processing on current extrusion blow molding machines, the outer layer of HDPE has the same thickness as a conventional six-layer fuel tank, and a regrind layer adjacent to the outer layer. And an adhesive layer between the regrind layer and the EVOH barrier layer, and another adhesive layer between the barrier layer and the inner layer. In view of the high capital cost of the fuel tank extrusion blow molding machine, it is preferred that the equipment currently used for conventional six-layer fuel tanks can be used to form the aforementioned multi-layer fuel tank 50. Therefore, the ORGALLOY inner layer 64 is 30% of the total thickness of the fuel tank wall 52, the damper layer 62 is about 5% of the fuel tank wall thickness, and the barrier layer 60 is 3% of the tank wall thickness. The adhesive layer 58 is 3% of the tank wall thickness, the middle layer 56 is 40% of the total tank wall thickness, and the outer layer 54 is 19% of the total tank wall thickness. Of course, these thicknesses describe the presently preferred embodiment and can be varied as desired within the scope of the current fabrication machine. Also, further changes may be made if new or different machines are employed. Experiments have shown that the hydrocarbon barrier properties of the inner layer 64 of ORGALLOY do not change significantly in the range of about 10-40% of the fuel tank wall of the inner layer 64, providing flexibility in the design of the fuel tank 50. . Desirably, the ORGALLOY material is extruded in the same extruder suitable for polyethylene as in a conventional six-layer fuel tank. Thus, the fabrication and fabrication of the multi-layer fuel tank 50 is very flexible, fully applicable to current processing equipment, uses the same machine, and has no significant replacements.

  As configured above, the multi-layer fuel tank 50 exhibits exceptional barrier performance against hydrocarbons as compared to conventional six-layer fuel tanks. This is why the inner layer 64 of ORGALLOY provides an excellent barrier to hydrocarbons, and more significantly prevents hydrocarbon penetration than HDPE. Thus, the fuel tank has a first barrier layer including the ORGALLOY inner layer 64 and a second barrier layer including the EVOH barrier layer 60. These barrier layers 60 and inner layers 64 are sequentially provided to significantly improve the permeation of hydrocarbons in the fuel tank 50 as a whole. Both the EVOH barrier layer 60 and the ORGALLOY inner layer 64 are at least essentially continuous, reducing or eliminating perforations in the fuel tank 50.

  In fact, as shown in FIG. 5, even in the region of the pinch line 70 of the blow molded fuel tank 50, the permeation of hydrocarbons along the pinch line 70 is significantly reduced. In a blow-molded fuel tank, the parison is surrounded by blow molding, the mold is closed, and the parison expands in the mold. Closing the mold closes the parison, forming a pinch line where the parison closed between the molds. Transmission along the pinch line is a problem in conventional six-layer fuel tanks. This is because the EVOH barrier layer is not continuous in the pinch area. Because, in a conventional six-layer fuel tank, the EVOH barrier layer is not sealed in the pinch area, and a permeation hole is formed between that part of the barrier layer, through which hydrocarbon vapors easily pass. escape. In the multi-layer fuel tank described herein, there are no permeation holes in the inner layer 64 even though there are similar holes in the barrier layer 60 (as shown in FIG. 5). Thus, the permeation of hydrocarbons through the pinch line 70 is significantly reduced. Although the theoretical and numerical grounds are not clear, it is estimated that about 20 to 30% of the hydrocarbon escape from the conventional six-layer fuel tank occurs in the area of the pinch line. Therefore, the continuous inner layer 64 of the fuel tank 50 significantly reduces the leakage of hydrocarbons from the fuel tank 50 even in the region of the pinch line 70.

  Further, as shown in FIG. 5, the ORGALLOY inner layer 64 has a function different from that of the conventional HDPE inner layer of the six-layer fuel tank. Desirably, the ORGALLOY inner layer 64 provides a reasonably flat inner surface 72 in the region of the pinch line 70 to significantly reduce or eliminate the problems of conventional six-layer fuel tanks. In conventional six-layer fuel tanks, the flow of material during the pinch process is difficult to predict and manage. Notches or protrusions are typically formed on the inner surface of the HDPE inner layer in the region of the pinch line. This notch may, for example, reduce the rigidity of the fuel tank with respect to internal pressure. According to the experimental data, the multilayer fuel tank 50 has excellent mechanical properties against internal pressure and the like, and a remarkable improvement in the fuel tank destructive test performance is seen. Data from certain experimental results show that fuel tank 50 exhibits increased internal pressure capacity, about 20-35% larger than a conventional six-layer fuel tank. In addition to forming a continuous, relatively flat inner surface 72, the ORGALLOY layer has a lower viscosity than polyethylene, and the thickness or stiffness of the EVOH barrier layer in the region of the pinch line 70 is reduced by a conventional six layer. It has no effect to the extent found in fuel tanks. Desirably, in the region of the pinch line 70, the barrier layer 60 of the multi-layer fuel tank is not as thin as in a conventional six-layer fuel tank. As a result, even in the region of the pinch line 70 of the multilayer fuel tank 50, the resistance to permeation of hydrocarbons is further improved.

  The multi-layer fuel tank 50 has significantly improved resistance to permeation of hydrocarbons as compared to conventional six-layer fuel tanks, and satisfies the very strict emission standards that are being reviewed or put into effect, for example, in California. . These standards are, for example, LEVII and PZEV, which require a significant reduction in vehicle emissions. Some designs with conventional six-layer fuel tanks may meet the requirements of LEVII, but do not meet the more stringent requirements of PZEVI. The multi-layer fuel tank 50 of the above-described embodiment satisfies the requirements of PZEV with extremely excellent resistance to hydrocarbon permeation. Roughly speaking, with respect to the barrier performance of various materials used for polymer fuel tanks in non-alcohol or low alcohol such as CARB PHII, if HDPE has a transmittance of 1000, ORGALLOY is about 1.5 and HDPE of HDPE is about 1.5. 1/600. By comparison, EVOH has a transmittance of 0.6. Therefore, it can be seen that ORGALLOY is a significantly better barrier against hydrocarbon emissions than HDPE. Because it is based on nylon, it is somewhat susceptible to fuels containing alcohol, but ORGALLOY has a greater resistance to hydrocarbon permeation than HDPE. Referring also to the approximate transmittance, HDPE has a transmittance of 1000 for high alcohol fuels such as the test fuel TF1 containing 10% ethanol, while ORGALLOY has a transmittance of about 225. Therefore, even with high alcohol fuels, ORGALLOY has a permeability of 1/4 or less than HDPE.

When the multi-layer fuel tank 50 is configured as described above, the tank is less resistant to permeation of hydrocarbons when using non-alcoholic or low-alcohol fuel compared to a conventional six-layer fuel tank. It is improved to about 0.5 to 1/3. In general, if the transmittance is assumed to be 100 when the conventional six-layer fuel tank uses such fuel, the fuel tank 50 has a transmittance of about 30 to 40. Similarly, fuel tank 50 has a permeability of about 1/2 that of a conventional six-layer fuel tank for a high alcohol fuel such as TF1. Assuming that the transmittance is 100 when the conventional six-layer fuel tank is a high alcohol fuel, the fuel tank 50 has a transmittance of about 45 to 55. Further, the fuel tank 50 has a test result of a transmittance of about 45 to 55, and the fuel tank 50 has a large reduction in emission, about 4 to 7 mg / day for CARB PhII, and an average of 5 mg / day, For TF1, it is about 7-10 mg / day, averaging 8 mg / day. These results were obtained from an 80 week soak test on a 70 liter fuel tank at a temperature of 40 ° C. The tank has an area of about 2.1 m ² and the length of the pinch line is about 2 m. In tests under the same conditions on a conventional fuel tank of the same dimensions, the conventional six-layer fuel tank is more than twice as transmissive for CARB PhII and about 60% higher for TF1. It is believed that the transmittance does not change significantly over the design life of the fuel tank over 15 years.

  Desirably, the multi-layer fuel tank dramatically reduces emissions of generally aromatic pollutants. Aromatics are generally benzene, toluene, ethyltoluene, xylene, heavy aromatics. Even with a fuel containing high alcohol, if the total permeability of the fuel tank 50 is about one-half that of the conventional six-layer fuel tank, the emission of aromatics from the fuel tank 50 will be reduced to one-half of the conventional six-layer fuel tank. It is 10. Thus, the highest pollutant emissions are dramatically reduced in the fuel tank 50. Alcohol and oxide emissions are also greatly reduced in the fuel tank 50.

  Further, because the inner layer 64 provides a stable, thick, continuous inner barrier layer, the hydrocarbon permeation resistance of the fuel tank 50 is consistent from tank to tank, day to day, and month to month. Further, the permeation resistance has a very small variation even in the processing and manufacturing of the fuel tank 50. Conversely, in a conventional six-layer fuel tank, variations in the thickness of the EVOH layer in any part of the fuel tank significantly deteriorate the hydrocarbon permeability. Since the EVOH layer is relatively expensive and brittle, it is important to control the thickness of the EVOH layer over the entire fuel tank. In a conventional six-layer fuel tank, the EVOH layer substantially determines the resistance to permeation of hydrocarbons. Therefore, some conventional six-layer fuel tanks meet certain strict emission standards, but all or many of the conventional six-layer fuel tanks on a certain production line may vary due to variations in processing of manufacturing machines, the surrounding environment, processing workers, and the like. It is unlikely that fuel tanks will meet these stricter standards.

  Furthermore, the ORGALLOY inner layer 64, ie, the fuel tank 50, has superior mechanical performance at higher temperatures as compared to a fuel tank using an HDPE inner layer, such as a conventional six-layer fuel tank. The ORGALLOY inner layer 64 has a significantly higher melting point than the HDPE layer, typically in the range of about 375-400 ° F. HDPE has a melting point in the range of about 255-275 ° F. Therefore, even when the temperature of the fuel tank 50 increases, the deformation of the tank wall 52 is small, and the risk of the inner layer 64 being melted by hot fuel returning to the fuel tank from the engine main supply pipe or the like is reduced or eliminated. In some diesel fuel systems, the fuel returns at elevated temperatures up to 255 ° F., which is in the range of the melting point of HDPE, dissolving HDPE, or at least locally or temporarily affecting tank stiffness. In contrast, fuel returned at a temperature of 255 ° F. has no significant effect on the ORGALLOY inner layer 64. This is because the layer has a higher melting point. The rigidity of the fuel tank 50 is better than that of a conventional six-layer fuel tank at least in a certain temperature range, particularly at a high temperature, as measured by an impact test. Because the fuel tank 50 has improved stiffness, the thickness of the tank wall 52 can be reduced, which can reduce weight and cost.

  Although generally described with respect to a blow-molded fuel tank having a pinch line, the structure of the fuel tank described herein may be used in a thermoformed tank, where a pair of halves of the fuel tank are made separately. They are joined by welding or the like. The ORGALLOY inner layer 64 is also continuous in this case. This is because the inner layer of one tank half is welded to the inner layer of the other tank half. The twist reduces or eliminates the permeation holes. In a thermoformed tank, the fuel tank is formed in two separate halves and thus extends around the entire circumference. Therefore, in conventional thermoformed fuel tanks, the weld line between the two tank halves can be a significant source of hydrocarbon leakage. This source of hydrocarbon leakage is significantly reduced or eliminated in the fuel tank of the present invention configured as described above. This is because the perforations are at least partially reduced or eliminated, i.e., the continuous inner wall is made of a material that significantly prevents the permeation of hydrocarbons through the tank wall 52.

  The foregoing description of the preferred embodiments is illustrative of these embodiments and does not limit the invention. For a person skilled in the art, various substitutions and modifications are possible within the scope of the invention described in the claims. For example, the outer layer 54 of HDPE is unnecessary if the regrind intermediate layer 56 is in the form of a matrix based on nylon. Because both the HDPE layer and the regrind layer are unnecessary. These elements are formed of a nylon-based material to facilitate welding other elements such as the fuel pump module vent valve and flange to the nylon matrix outer layer (if the HDPE layer is not used). . Furthermore, although the barrier layer of the last-described embodiment has been described as being formed of EVOH and ORGALLOY, other materials may be used. EVOH may be replaced by other materials that are resistant to hydrocarbon permeation. Similarly, the inner layer may be formed of polyamide or another mixture of polyamide and polyolefin instead of ORGALLOY. As another example, the EVOH material described with respect to barrier layer 60 may be formed of another polyamide or a mixture of a polyamide and a polyolefin, such as, for example, ORGALLOY. This is desirable when a multi-layer fuel tank is used for non-alcoholic or low alcohol fuels. This is because materials such as polyamides or mixtures of polyamides and polyolefins, such as ORGALLOY, are good barriers to hydrocarbon permeation, especially with non-alcoholic fuels. Although the case where the fuel tank 50 is blow-molded or thermoformed has been described, as still another example, the fuel tank 50 may be formed by stacking a polyethylene film or the like to form a layer made of a hydrocarbon barrier material. good. Of course, other materials can be used in the formation of the fuel tank depending on the application within the scope of the present invention.

1 is a perspective view of a plastic fuel tank for a vehicle according to a preferred embodiment of the present invention. FIG. 2 is a partial sectional view of a wall of the fuel tank of FIG. 1. FIG. 9 is a partial sectional view of a modified example of a wall of a fuel tank embodying the present invention. FIG. 5 is a partial sectional view of a fuel tank wall according to a second preferred embodiment of the present invention. FIG. 5 is an enlarged partial sectional view showing a portion of a tank wall in a pinch line region of the fuel tank of FIG. 4.

Explanation of reference numerals

Reference Signs List 10 fuel tank 12, 12 'wall 14 pipe 16 flange 18 fuel pump module 20 cover flange 22 first layer 24 second layer 26 binder layer 28 third layer 50 fuel tank 52 tank wall 54 outer layer 56 middle layer 58 Adhesive layer 60 Barrier layer 62 Damper layer 64 Inner layer 70 Pinch line

Claims (11)

A fuel tank,
A tank wall forming the interior of the fuel tank, the tank wall facing the interior of the fuel tank, having an inner layer of a mixture of polyamide and polyolefin;
A barrier layer generally surrounding the inner layer;
At least one structural layer surrounding the barrier layer;
The above-mentioned fuel tank, comprising: The tank wall is formed of a multilayer parison and is blow molded to a final shape, the tank wall having a pinch line in the area where the parison is closed during blow molding;
In the inner layer, a portion of the inner layer is engaged with another portion of the inner layer to pinch the parison to form the continuous inner layer of the tank wall so that there are no perforations. 2. The fuel tank according to claim 1, wherein:   The fuel tank according to claim 1, wherein an adhesive layer is provided between the barrier layer and the structural layer.   The fuel tank according to claim 1, wherein a damper layer is provided between the inner layer and the barrier layer.   The fuel tank according to claim 1, wherein the inner layer has a continuous inner surface, the inner surface contacting fuel in the fuel tank. The tank wall is
An outer layer,
A barrier layer,
An adhesive layer between the outer layer and the barrier layer;
A damper layer between the barrier layer and the inner layer;
The fuel tank according to claim 1, further comprising:   The fuel tank according to claim 6, wherein the adhesive layer and the damper layer are formed of the same material.   7. The fuel tank according to claim 6, wherein a regrind material layer is provided between the outer layer and the barrier layer.   9. The fuel tank according to claim 8, wherein the regenerated material layer is provided between the outer layer and the adhesive layer.   9. The fuel tank according to claim 8, wherein the regrind layer has a matrix structure based on nylon.   9. The fuel tank according to claim 8, wherein the regenerated material layer has a matrix structure based on polyethylene.

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