CN104943304A - Fuel tank - Google Patents

Abstract

A fuel tank comprises a multilayer wall constituted at least of one layer based on a reinforced thermoplastic composition and of one inner layer, intended to be in contact with the fuel, based on a non-reinforced thermoplastic composition, wherein the thickness of the inner layer is at least 20% of that of the multilayer wall. The fuel tank is used as a fuel tank of a hybrid vehicle.

Description

fuel tank

This application is a divisional application of the original application number 201080027986.1, the filing date is June 3, 2010, and the invention title is "Fuel storage tank or filling pipe for such storage tank".

The present invention relates to a fuel tank or a filler pipe for such a tank and also to their use as a tank/pipe in hybrid engine vehicles.

A hybrid engine generally refers to the combination of an internal combustion engine and an electric motor.

There is a general operating principle for hybrid engines, which consists in operating the electric motor, or the internal combustion engine, or both simultaneously, according to the model.

One of these specific principles is as follows:

During the static phase (when the vehicle is at a standstill), both engines are switched off;

At start-up, it is the electric motor that sets the movement of the vehicle up to higher speeds (25 or 30km/h);

When higher speeds are reached, the internal combustion engine takes over;

In the case of rapid acceleration, both engines operate simultaneously, which makes it possible to have equal or even higher accelerations than engines of the same power;

During deceleration and braking phases, kinetic energy is used to charge the battery (it should be noted that this function is not available in all hybrid engines currently commercially available).

This principle leads to the fact that the internal combustion engine does not run constantly and thus that the purification phases of the canister (activated carbon filter which prevents the release of fuel vapors into the atmosphere) cannot be performed normally, because during these purification phases, any Optionally pre-heated air is circulated through the canister to regenerate the canister (ie, to desorb fuel vapors sorbed therein), before allowing this air to enter the engine for combustion therein. Furthermore, hybrid vehicles were developed to reduce fuel consumption and exhaust emissions, making it more difficult or even impossible to manage the engine to burn fuel vapors from the canister without degrading engine performance.

Therefore, the fuel tanks of these engines are usually pressurized (typically to a pressure of about 300 to 400 mbar) in order to limit the load on the canister, which is usually performed by a functional element located after the vent valves, This element is called FTIV (Fuel Tank Isolation Valve). This element consists of a safety valve (calibrated to the maximum working pressure of the tank) and an electronic control to be able to bring the tank to atmospheric pressure before filling. As a result, especially in the case of plastic tanks, these must have improved mechanical strength compared to conventional fuel tanks for internal combustion engines.

Solutions currently on the market consist of a metal tank of great thickness, which considerably increases the weight of the tank and thus increases fuel consumption and exhaust emissions.

Other known solutions to the above pressure problems may include increasing the wall thickness of the plastic tank and/or using internal reinforcement (rods, dividers, etc.) The solution generally has a negative impact on the weight, reduces the working volume of the tank and increases the cost of the tank. Another solution could consist in providing the tank with attachment studs (or kiss points, i.e. local welds of the lower and upper walls), but this solution Resulting in a reduction in the working volume of the tank.

Another solution is described in the patent US 5,020,687, which consists in attaching a reinforcing fabric to the outer wall of the tank, this attachment being carried out by extruding-blowing The fabric is overmolded in the manufacturing process of air molding, which is introduced into the mold before the parison in which the tank will be obtained after blow molding the parison.

However, this solution has several drawbacks:

In fact, this fabric produces only localized reinforcement at the place where it is attached;

In the long run, the diffusion of fuel vapors through the tank wall may cause expansion problems, or even a loss of adhesion of the fabric to the tank wall, thus reducing the reinforcing effect;

Due to the technology used, there are various limitations regarding the thickness of the fibers and/or the geometry of the mold;

And finally: this type of reinforcer is relatively expensive.

A subject of the present invention is therefore a fuel tank or a filler pipe for such a tank, which has good long-term mechanical strength and which does not suffer from the disadvantages mentioned above.

Based on the idea of using a reinforced plastic composition, i.e. a plastic in which already dispersed/mixed (e.g. in the molten state of the plastic using an extruder) there is a reinforcement (specifically a fiber reinforcement substances), which are known per se, but do not use such a composition in the inner layer of a multilayer tank (ie the inner layer that comes into contact with the fuel), but (if appropriate) only in the outer layer and/or used in an intermediate layer. In fact, the Applicant has observed that when the inner layer of tanks comprises a reinforcement (in particular: when it comprises fibres), the crash strength of these tanks is substantially reduced to such an extent that They no longer pass these standards set by the motor vehicle manufacturer. In another aspect, after providing a non-reinforced inner layer, the inner layer has a sufficient thickness (the value of this thickness depends on the composition of the layer, but the thickness is generally at least 20%, or 30% of the relative thickness % or even 40%), this reduction is no longer observed, and even better: in some cases even a substantial improvement can be observed.

The present invention therefore relates to a fuel tank or a filler pipe for such a tank, comprising a multilayer wall made of at least one layer based on a reinforced thermoplastic composition and an inner layer intended to come into contact with the fuel and based on an unreinforced thermoplastic composition.

The fuel used in the tank/tube according to the present invention is expected to be gasoline, diesel, biofuel, etc. and may have an alcohol content of 0 to 100%.

The expression "tank or tube" is understood to mean any tank or tube obtained by molding or coextruding at least two of the aforementioned layers.

A molding operation which may be used to manufacture a tank or tube of limited length according to the invention may be of any nature so long as it involves the use of a mold which can determine the shape of the tank or tube. This molding operation can be performed, for example, starting from a preform or directly by introducing gelled thermoplastic into the mould.

This molding operation can also in particular be associated with a blow molding operation. It can also be followed by a subsequent assembly step, especially by soldering. If the molding operation is carried out starting from a preform, this preform can in particular be obtained by coextrusion or co-injection.

Very good results have been obtained using molding by coextrusion-blow molding, molding by co-injection-welding or molding by thermoforming. Preferably, the multilayer tank or tube is produced by coextrusion-blow molding (blow moulding). In the latter case, it is possible to use a continuous extrusion technique or a build-up extrusion technique or a sequential extrusion technique, all techniques familiar to the person skilled in the art.

The term "thermoplastic" is understood to mean any thermoplastic polymer, including thermoplastic elastomers and also blends thereof. The term "polymer" should be understood to mean both homopolymers and copolymers (in particular binary or terpolymers), for example random copolymers, linear block copolymers, other block copolymers and graft copolymers, etc.

The plastic of the inner layer and the plastic of the reinforcing layer may (and preferably do) have the same properties. In the case of fuel tanks this is usually polyolefin. The term "polyolefin" is understood to mean any olefin homopolymer, any copolymer comprising at least two different olefins and any copolymer comprising at least 50% by weight of a plurality of units derived from olefins. Several polyolefins can also be used in the blend. More specifically, the blend may contain, in addition to virgin polyolefin, a proportion of regenerated polyolefin, or a blend of regenerated resins in a certain proportion, which Such a blend results from (i) grinding of residues obtained at different stages of manufacturing the multilayer tank or tube and/or (ii) regeneration and disposal of end-of-life fuel tanks. This blend may also comprise a polyolefin of plant origin or from another renewable source (biomaterial).

Preferably, the polyolefin is a polyethylene. Very good results have been obtained with a high density polyethylene (HDPE).

These plastic compositions may include a variety of conventional additives, such as provided stabilizer(s), lubricants, pigments and other "fillers", however the additive(s) of the inner layer do not have a reinforcing effect and /or are present in such an amount that they do not have a significant effect on their mechanical properties.

The term "reinforced" is understood, in the context of the present invention, to mean a mixture comprising a reinforcement or reinforcements in a dispersed state (i.e. in a "free" state mixed with the plastic). "The form of the particles, as opposed to knitted or entangled particles (fibers) as in a woven fiber or mat), is at such an amount that it has a significant effect on the mechanical properties of the composition. At this stage, a distinction should be made between (i) microscopic fillers/reinforcements and (ii) nanofillers, for microscopic fillers/reinforcements at high filling levels (typically greater than 10%) Significant effects on these properties are obtained, whereas for nanofillers a dramatic change in these properties is obtained with only a few percent reinforcement.

Generally, these are fiber reinforcements (carbon fibers, natural fibers, glass fibers, etc.), beads (e.g. glass beads, generally hollow beads) or small pieces (e.g. talc, clay, montmorillonite, vermiculite , expanded graphite, graphene). They are preferably fibers. Of course, powders (carbon black, chalk, talc, barium sulphate, etc.) are generally not considered reinforcements within the context of the present invention, except for those reinforcements which may have a significant influence on the mechanical properties of the composition. Glass fibers and especially short and long glass fibers give good results in the context of the present invention. For short fibers, good results have been obtained by dispersion, in HDPE, fibers based on E-glass (specifically equipped with a sizing and/or a compatibilizer, such as PE-g-MAH) Has a diameter between 10 and 20 μm and an initial length between 2 and 8 mm.

According to a preferred variant, glass fibers are chosen as reinforcement, which reinforcement is specifically combined in an amount (preferably homogeneously, usually by mixing in an extruder in order to produce masterbatch pellets) into a In the intermediate layer and very particularly in a layer resulting from grinding as described above, the amount is from 10% to 50% (by weight compared to the total weight of the mixture), or even from 20% to 40% %, a content of about 30% usually gives good results.

In fact, the Applicant has blow molded a correspondence between these 2 layers of virgin PE with an inner layer of about 45% relative thickness (relative to the total thickness of the wall) and an outer layer of 20% relative thickness. Based on pure HDPE ( 4261AG, a bottle with a density of 0.945 g/ ^cm3 and a HLMI of 6 g/10 min (190 °C/21.6 kg) in a single-layer construction, and based on the same HDPE but including a layer of industrial regrind, as defined above 6-tier storage tank for bottles. The Applicant varied the glass fiber content in several tests and presents the corresponding observed properties in a table at the end of the description.

In particular, when it comprises at least one layer based on polyethylene, the tank according to the invention preferably also comprises a barrier layer and/or preferably has been subjected to a surface treatment (for example: a fluorine sulfonation or a sulfonation). Preferably, it comprises a barrier layer, also of a thermoplastic, usually the non-reinforced inner layer of the tank, or an intermediate layer between the inner layer and the reinforced layer.

In the context of this variant of the invention, the barrier resin that can be used may be of any nature known to the person skilled in the art, as long as it is a polymer or copolymer compatible with the molding technique in question . It can also be a mixture of different barrier resins. Among the resins that can be used, mention is made in particular of polyamides or copolyamides, or random ethylene/vinyl alcohol (EVOH) copolymers.

The term "polyamide" is understood to mean any homopolymer based on one amide unit, any copolymer comprising at least two different amide units and any copolymer comprising at least 50% by weight of units derived from amides thing. It is immaterial whether the amide units under this definition are obtained by opening the rings of a cyclic polyamide or by polycondensation of dicarboxylic acids with diamines. Several polyamides are also available as a blend. As examples of polyamides that can be used there may be mentioned (non-limiting): PA-6, PA-11, PA-12 and n-mXD6 (polyarylamide). PA-6 is generally preferred.

Favorable results have been obtained in the case where the barrier resin is EVOH and in particular between 2 layers of HDPE (usually by inserting two layers of PE based bonding at the 2 interfaces of EVOH/HDPE agent) has an intermediate barrier layer based on EVOH. Favorable results have also been obtained in the case where the barrier resin is an aramid of the n-mXD6 type constituting the inner layer of the structure.

The layer comprising the barrier resin may also include certain additives known to those of ordinary skill in the art, which may or may not be polymeric, such as stabilizers, lubricants, and the like.

Preferably, the layer comprising the barrier resin consists essentially of barrier resin.

Typically (and occasionally with HDPE and EVOH or HDPE and polyamide) the barrier resin is incompatible with the thermoplastic resin of the other layers of the tank/pipe. In general, therefore, at least one or even two layers of adhesive are provided between the barrier layer and the one or two other layers in contact with it. Alternatively or additionally, a binder compatible with the thermoplastic resin may be mixed with the resin.

Preferably, the adhesive discussed above comprises at least one functionalized polyolefin.

The expression "functionalized polyolefin" is understood to mean any polyolefin comprising, in addition to units derived from olefins, a plurality of functional monomeric units. These functional monomer units may be incorporated in the polyolefin, incorporated in the main chain, or incorporated in the side chain. They can also be incorporated directly in the backbone of the main main chain and side chains, for example, by copolymerizing one or more functional monomers with the olefin monomer(s) or can result in one or more Multiple functional monomers are grafted onto the chain. In this case, the polyolefin/functionalized polyolefin blend can especially be produced in a separate step by reactive processing in the gelling step included in the process for manufacturing the tank or pipe.

In this variant of the invention, these functional monomer units are chosen from carboxylic acids, dicarboxylic acids and anhydrides corresponding to said dicarboxylic acids. Thus, these units generally result from the copolymerization or grafting of at least one unsaturated monomer having these same functional groups. As examples of monomers which may be used, mention may in particular be made of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, maleic anhydride, fumaric anhydride and itaconic anhydride. Preferably, these functional monomer units result from the copolymerization or grafting of maleic anhydride.

The functionalized polyolefins described are therefore well known to the person skilled in the art and are commercially available.

In case the polyolefin is a polyethylene, it is particularly advantageous to make the functionalized polyolefin a polyethylene grafted with maleic anhydride (PE-g-MAH), that is, these functional mono The monomer unit is obtained by grafting maleic anhydride onto polyethylene.

A multilayer tank or pipe according to the invention may advantageously comprise one or more additional layers comprising a recycled plastic, preferably as an intermediate layer (i.e. between 2 other layers layer in between).

The expression "recycled plastics" is understood to mean the grinding of residues obtained at different stages of the manufacture of hollow bodies, in particular the tanks/pipes according to the invention, or the processing of such bodies at the end of their service life Plastic obtained by grinding.

In this variant, reinforcements can be incorporated in the recycled plastic layer or layers. In order to do this, the particles are collected from the above-mentioned grind, and they are mixed with a pellet of a masterbatch including fillers, and this mixture is then conveyed to the above-mentioned coextrusion-blowing molding equipment. One extruder is sufficient. Alternatively, the regrinds can be used to produce a masterbatch with the desired reinforcement composition. This variant is preferred because it enables as much of the grounds as possible to be reused.

In a particularly advantageous embodiment of the multilayer tank or pipe according to the invention, the multilayer tank or pipe comprises 6 layers: an inner layer (I) based on non-reinforced HDPE, preferably based on PE-g - a first adhesive layer (A1) of MAH, a layer (B) comprising a barrier resin, preferably EVOH, a second adhesive layer (A2), preferably based on PE-g-MAH, A layer (R) based on recycled resin comprising a reinforcement, preferably glass fibers, and an outer layer (E) based on HDPE.

In this embodiment, it is advantageous to have the relative distribution of the thicknesses as follows (for a total thickness of 1 to 10 mm, or even 3 to 7 mm; usually around 6 mm): I: 30%-50%, A1: 1%-3 %, B: 1%-3%, A2: 1%-3%, R: 30%-60%, E: 5%-20%. The following structure is advantageously used (to within a few percent): for each of these layers I/A1/B/A2/R/E correspondingly the % of the overall thickness is 39/2/2/2/45 /10.

According to a particular embodiment, the layer E (in contact with the atmosphere) comprises a compound based on carbon black for the purpose of protection against UV radiation.

Also advantageously, a multilayer structure with 2 or 3 layers comprising: one (inner) layer based on n-MXD6, one layer based on reinforced HDPE (optionally containing adhesive), and optionally (if the HDPE layer does not contain any adhesive) one adhesive layer.

The invention also relates to the use of a tank/tube as described above as a fuel tank for a hybrid vehicle. This tank/pipe can also be used in conventional vehicles, where the reinforcement obtained can be used to avoid the use of metal straps which are generally used when the tank is fastened to the underbody of the vehicle body Prevents creep of the lower wall of the tank.

It should also be noted that the reinforcement obtained by the subject matter of the invention can be combined with the use of other known reinforcements, such as the above-mentioned straps, attachment pins, internal reinforcements (rods, dividers objects), overmolded fabrics, etc., and any other type of internal and external reinforcement.

The combination of the present invention with these known technologies makes it possible to reduce the size and/or number of attachment pins, internal reinforcements (rods, dividers), overmolding fabric, etc. Thus, the weight of the final solution is minimized and the working volume of the tank is maximized.

Claims (10)

1. a fuel tank, comprise a kind of compound wall, this compound wall at least by based on the thermoplastic compounds strengthened a layer and be intended to contact with fuel and an internal layer based on a kind of thermoplastic compounds of non-reinforcing is formed, the thickness of wherein said internal layer is at least 20% of the thickness of described compound wall.

2. fuel tank according to claim 1, wherein, the thickness of described internal layer is at least 30% of the thickness of described compound wall.

3. fuel tank according to claim 1, wherein, the thickness of described internal layer is at least 40% of the thickness of described compound wall.

4. fuel tank according to claim 1, wherein, the thickness of described internal layer is 30% to 50% of the thickness of described compound wall.

5., according to the fuel tank one of Claims 1-4 Suo Shu, described fuel tank is molded by coextrusion-blow molding or common injection-welding and produces.

6. according to the fuel tank one of item Claims 1-4 Suo Shu, wherein, the thermoplastic compounds of described enhancing comprises the mixture of thermoplastic and a kind of fortifier or multiple fortifier, and described fortifier is in the state of dispersion, and its content is greater than 10%.

7. fuel tank according to claim 6, wherein, the content of described fortifier is 10%-50%, or 20%-40%.

8. fuel tank according to claim 6, wherein, described fortifier comprises: fiber, and described fiber comprises carbon fiber, natural fiber or glass fibre; Beading, described beading comprises glass beading or beading hollow generally; Or small pieces, described small pieces comprise talcum, clay, imvite, vermiculite, expanded graphite or Graphene.

9. fuel tank according to claim 8, wherein, described fortifier is the short glass fiber of dispersion, and its diameter is 10 μm-20 μm, and initial length is 2mm-8mm.

10. the fuel tank according to any one in above claim is as the purposes of the fuel tank of motor vehicle driven by mixed power.