Fluid or steam conveying system with a weld seam made from a coextruded laminate

The present invention is a method for connecting one or multilayer plastic hollow bodies with connecting elements such. as connection nipples, Threaded sleeve, sealing covers or valves. The connection is made by means of a Finished or finished finished a coextrudate produced performed.

Plastic hollow bodies are mostly by blow molding, including all variants thereof, for example, suction blow molding, or by extrusion. However, it is also Embodiments are conceivable in which the hollow body of thermoformed extruded sheets, the previously been thermoformed, is welded together. Moreover, are also Hollow body known that z. B. are rotationsgesintert or injection molded from polyamides. It is also conceivable, pipes, or by conventional extrusion by means of a pipe Disk calibration or by means of shaping jaws (principle of the corrugated pipe deduction) be prepared to provide at the ends with caps and thus also produce a container. Regardless of the manner of manufacture of the container is of usually with threaded connections, pouring or filler neck and openings or with Nipples to provide for the connection of cables. This is especially true for Fuel tank, where additional and connecting nipples for lines Filler neck shall be welded also various valves.

often also in pipelines is a need, taps, valves or cover attach.

In particular when hollow bodies consisting of polyethylene as a main component a single or consist multilayered wall, the problem arises that a permanent seal of Threaded or bayonet with conventional technology (screw and Rubber seal) because of the high creep of the polyethylene poorly to is realized. The problem is compounded when to store the or leading Liquids (such as plant protection agents, solvents, fuels or oils) or the wall swell associated components or when by changing temperatures Materials alternately can expand or shrink. In this case it is advantageous if the corresponding connection element consists of a hard, non-creeping and possibly also only slightly is to no swelling material and the Tank or pipe wall welded or by means of extrusion coating or Umblasen with this connected is. this, however, is a tolerance of one another in direct contact stationary and joined together materials needed because the only way to permanently reliable and tight connection can be achieved.

In the case of a plastic fuel tank occurs another problem. As part of the increasingly stringent requirements for the reduction of hydrocarbon emissions from Motor vehicles are those containers Today predominantly in multi-layer design prepared with up to 6 layers, where one of these layers one against the permeation of Fuel components much more blocking layer. Openings in the Tank bladder are cut to weld additional components that make regarding the permeation of fuel components, however, a weak point. If the on the openings aufzuschweißenden connection elements made of the same material as the Gas cap, usually polyethylene, so the permeation at these points is higher than at other locations of the multilayer composite. Prior art has been mainly the Welding of nipples, connections and valves or valve covers that fully made of polyethylene and have no separate barrier. such a assembled tank is no longer capable of becoming the increasingly fierce Requirements sure to exist as such. B. under the headings "LEV-II" and "P-ZEV" are known from the future US emission protection legislation by CARB.

In addition to a low-permeation cover the breakthroughs also proves the connection of lines to a plastic fuel tank as problematic as between welded nipples made of polyethylene and connected to these pipelines can quickly cause leaks due to the creep of the polyethylene. one of Cost reasons advantageous connection between nipple and pipeline by means of so-called The quick connector is not possible because the pressure of the O-ring seals to a crawl the polyethylene and thus very soon leads to unacceptable leakage. The same applies to Connection of the filler neck and tank. For this reason, such Compounds usually with the aid of short elastomer hoses and clamps executed. Although the leakage can be avoided by the use of elastomeric tubing will; in this case, but make the hoses even the weak point as they in are highly permeable to hydrocarbons. Hoses made very good blocking fluoroelastomers, however, are extremely expensive. In addition, the compound is of Polyethylene nipple or steel bung by rubber tubing to a non-creeping Connecting element, such. As glass fiber reinforced polyamide, expensive to manufacture and expensive. Thus, there is the requirement that such solutions by cheaper and better Systems should be replaced.

If you want to run the nipple directly so that the creep is avoided, as must this glass fiber-reinforced molding compositions are used. There are however no suitable reinforced polyethylene types that the further mechanical requirements the connection are grown. Furthermore, the strength of a weld joint between a fiber-filled and an unfilled polymer is not sufficiently high. It therefore components must be found, which on the one hand with the can connect tank material cohesively, on the other hand, better Features relating to the blocking effect and creep than z. B. polyethylene.

From DE-PS 42 39 909 is known a connection is attempted with these problems to solve. There, a tubular piece is made of a creep-prone material A one side with a second material B, which has a low tendency to creep, molded. In the contact area between the two materials having this tubular Formations so a layer structure AB. However, this connection technology has in practical tests can not prove. With fuel contact material A swells namely heavily on. Since the swelling to one side by the material B is hindered, swells and creeps the material in the other directions away, so that after some time the a power transmission, secondly, the tightness of the connection is no longer is guaranteed. is reinforced this phenomenon even under mechanical stress and / or dehydration of this tubular nozzle. The proposed Modification of the two materials to achieve adhesion between the two Molding compounds used rather leads to deterioration because the modified material (Usually polyethylene) swells even more and also the blocking effect by the Modification is significantly worse.

In DE-PS 195 35 413 describes a way, a connection element produce two materials A and B, in which a between the materials A and B form-fitting bond is present. At the same time between A and B is a embedded adhesion-promoting molding composition, which additionally comprises a cohesive composite results. The weaker creeping material B can on a container whose outer skin from a compatible with B and weldable material is to be welded. In the development of this component, it has been found that the compatibilizing the two materials, while the realization of the weldability Tank material is a difficult problem to solve, and thus only a few suitable Material combinations can be developed at great expense. On the other Page is one to manufacture by injection molding element is usually a Bond between two, in exceptional cases, between three, different molding compounds limited. This limitation is primarily for the reason that the materials only enter into an intimate chemical and thus reliable connection when in "melt be melt processed "by co-injection. elements of three or more Materials have to be generally prepared via multi-step processes in which respectively, a melt is sprayed onto an already solidified component (overmolding process). Here, usually the one hand the bond strength is significantly worse than a processing melt in melt. Secondly, too many costly Manufacturing steps required when three or more materials are applied to one another have to.

Another problem in the case of the aforementioned connecting elements results from the fact that by welding a multi-component element in a polyethylene exported welding flange has, on the polyethylene outer skin of the tank, a relatively thick Polyethylene intermediate layer between the barrier layer of the tank and the blocking of the skin Element remains the fuel constituents first between weld and diffuse barrier parallel to the surface and then the connecting element into the past Free will be issued. Here it would be advantageous to provide the locking component of the Connection element or the valve cover as close as possible to the barrier layer To zoom bring to hereby available for diffusion keeping passage area as small as possible. but to the narrow limits are set, since the one of injection molding, from reasons the thickness of the weldable flange component can not be reduced. Secondly, in the conventional welding processes, such. as the mirror welding, not arbitrarily displaced much melt and thus the thickness of the Liner can be reduced. Available welding pressure, flexibility of the tank and bladder Solidification rate of the molding material to be joined to the narrow limits set.

The object of the present invention is therefore to provide a possibility for preparing propose corresponding compounds in which the above mentioned problems by an appropriate geometric configuration of the transition region between a Hollow body, the jacket is on the outer surface of a material A, and one of these binding to the second component, the at least one layer of the contains material B can be avoided.

In particular, this connection should be looking for an opportunity, so to realize that a multitude of different combinations of materials included can be.

This object is achieved by a connecting element, which contains the following components:<sl><li>I. A connection element as well</li><li>II. A coextruded multilayer composite, which consists of at least two layers,</li></sl>wherein the components I and II. are cohesively connected to one another.

The invention is also a liquid or vapor leading system, the includes connection element of the invention, wherein this, for example by means Welding or molding, is connected to the single- or multilayer hollow body.

The invention further is a single- or multi-layer hollow body with the coextruded multilayer composite or the connection element of the invention is firmly bonded.

The connecting element used in the invention may consist of a molding composition which comprises is unreinforced, reinforced or filled. For example, glass, carbon, Aramidoder Metal fibers are used as reinforcing agent. The molding composition may also be equipped electrically conductive additives anti electrostatically. Your polymer base is for example, a polyamide such as a polyphthalamide, PA46, PA6, PA66, PA612, PA1012, PA1212, PA11 or PA12, a polyester such as Polyethylene terephthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate or Polybutylene 2,6-naphthalate or a fluoropolymer such as polyvinylidene fluoride. It can However, any other polymer may be used, the sufficient rigidity and Resistance to liquid or vaporous medium has such. B. Polyphenylene sulfide, mixed aliphatic / aromatic polyamide such. B. PA6T / MPMDT, Polyamide blends such. B. Ultramid® T or TROGAMID® BX (PA6,3T / PA66 Blend) or aliphatic polyketone.

The connection element may be either single-layer construction or of 2, 3, 4, 5, or more layers. can a layer thereof, for example, a barrier layer respect to the liquid or vaporous medium or an antielectrostatic be modified layer.

Examples of suitable connecting elements are connecting nipples, threaded sleeve, Cap, valves, bayonet, quick connector (quick connectors) Threaded; but also the connection of entire assemblies is possible such. B. Activated carbon filters, expansion tanks or filter housings.

The co-extruded multi-layer composite has at least one layer B with the can be connecting element firmly bonded, and a layer A, the the with Hollow body can also be firmly bonded. Prerequisite here is that the Layers A and B can be joined by coextrusion together cohesively.

this, however, are only a few known combinations. Usually must Here one of the materials used are modified, often with a Worsening performance properties is connected (eg. As lower Locking action, higher swelling, inferior mechanical properties). Examples of a two-layer structure would be the following combinations:<sl><li>Polyamide (here and in the following examples, optionally with an excess of Amino end) / maleic anhydride functionalized polyethylene or polypropylene;</li><li>Polyamide / polyester, the bearing by means of functional groups polymers is adhesion-modified;</li><li>Polyamide / polyester, with the help of di- or polyfunctional compounds is adhesion-modified, wherein the functional groups, for example, anhydride, epoxy, can be oxazoline or isocyanate;</li><li>Polyamide / fluorine polymer which is functionalized with maleic anhydride;</li><li>Polyamide / fluoropolymer by adding an acrylate or methacrylate is adhesion-modified.</li></sl>

If one uses between the layers A and B an adhesive layer C, so can the Materials of the layers A and B purely by the function request z. B. with respect Blocking effect, weldability and mechanics are selected. Moreover, it is by arranging a plurality of adhesive layers (C1, C2, etc.) possible two Layers to connect A and B with each other, the only one directly with Adhesive layer C would not connect.

As a further layer, the coextruded multilayer composite, a barrier layer against included diffusion of fuel and the like, such as EVOH. to a to achieve optimum protection against permeation, the barrier layers of the coextruded be Multilayer composite and the hollow body preferably as close as possible to one another or brought in contact with each other as possible.

The coextruded multilayer composite, for example, the construction Polyethylene / tie / EVOH / tie / polyamide or polyethylene / tie / PVDF / bonding agent / polyamide have. Corresponding composites with polyesters, Polyacetals, polyphthalamide, polyphenylene sulfide, or other coating materials are possible.

The composition of the invention can be used according coextruded Multilayer composites is disclosed, for example in the following publications: EP-A-0509211, EP-A-0569683, EP-A-0601295, EP-A-0618390, EP-A-0637511, EP-A-0649739, EP-A-0 673 762, EP-A-0686797, EP-A-0729830, EP-A-0878509, EP-A-0982122, EP-A-1 031 411, EP-A-1065048, DE-A-100 64 333, DE-A-100 64 334 and DE-A-100 65 177, EP-A-0 777 578, EP-A-0991720, WO 200123796, US 5736610, EP-A-0791153, EP-A-0 731 307, EP-A-0731308, DE-A-198 03 134, EP-A-0428833, DE-A 37 15 251, EP-A-0 912 330, EP-A-0436923, EP-A-0925913, US 6176268, EP-A-0635108, FR-A-2 707 724, EP-A-1118807 and EP-A-1002980.

The co-extruded multi-layer composite composed in particular of 3, 4, 5, 6 or more Layers.

The coextruded multilayer composite may be made depending on the type of connection to be realized a coextruded film or sheet, a coextruded tube (possibly by means of Mold jaws shaped) or by coextrusion or Coextrusionssaugblasformen Composite produced exist. Optionally matching pieces thereof cut out or punched out. Another forming the multilayer composite before Connection with the connecting element or in front of the connection with the single or multi-layer hollow body, if desired, for example by thermoforming or Thermoforming possible; this may be before or after any cutting or punching done.

The hollow body is for instance a container or a pipe. examples for this are Plastic fuel tank or tanks, containers for activated carbon filter, bubble tank, Filler Necks or pipes, for example for fuel, brake fluid, Hydraulic fluid, or coolant.

The compound of the coextruded multilayer composite with the hollow body may by means of carried conventional welding methods or by insertion into the mold used for the production the hollow body is used by means of blow molding or rotational molding. The connection in this case is facing by melting of the container material Composite surface based simultaneous chemical reaction at the interface or based physical material compatibility. The connection with the connecting element then takes place via a welded connection between the connection element and the already the hollow body appended coextrusion.

On the other hand, it is also possible first to coextrusion with the Connection element to connect. This can by back injection molding by inserting the Coextrusionsverbunds into an injection mold and insert molding with the material of done connecting element or by welding the Coextrusionsverbunds with the connecting element. The subsequent communication with the hollow body is again as previously described by welding or by insertion into the mold.

Analogous to the procedure described in this example, it is also possible, to add branches or tabs on pipes.

The hollow body may be composed one layer or of 2, 3, 4, 5, 6 or more layers consist. He may in particular a barrier layer and / or an antielectrostatic Equipped layer.

The invention by means of specific embodiments is exemplary are explained.

The <b>figure 1</b> shows an injection molded connection nipple <b>(1)</b> from a glass fiber filled Polyamide, of a coextruded film consisting of a polyamide <b>(2)</b> a functionalized polyethylene <b>(3)</b> and a high density polyethylene (HDPE) <b>(4)</b>connected is. The so realized element is a single- or multilayer tank mainly HDPE <b>(5)</b> welded.

Another embodiment is obtained according to <b>figure 2</b> from an injection-molded socket of a polybutylene terephthalate <b>(6)</b> at the collar, a multilayered, means Back deduction (corrugated pipes) manufactured cone is welded. The cone has the Layer structure polybutylene terephthalate <b>(7)</b>/ Tie <b>(8th)</b>/ HDPE <b>(9)</b> (Adhesion promoter eg BYNEL® CXA 4157). He is a multi-layer Krafttstofftank<b>(10)</b>welded, which is shown here in three layers, but also the structure (from the inside to outside) HDPE / tie / EVOH / tie may have / regrind / HDPE. Corresponding layered tanks are prior art (eg. B. Siewert, H. Thielen, M .:<sl><li>Trends in coextrusion, plastics <u>88</u> (1998) 8, pp 1218 ff.). By conical design of the welding point, the gap between the EVOH barrier layer of the Tanks and also very good barrier to fuels polybutylene terephthalate (As shown in Figure 1) to a newly executed weld reduced are what the permeation losses reduced. A corresponding conical design of coextruded component can also be obtained by thermoforming of coextruded sheets achieve or films.</li></sl>

In accordance with the further requirements for the purpose of the connection can here Embodiment shown the sleeve can be varied. Thus, additional elements in their z. B., such as O-rings or retaining devices for sealing and locking a optionally be inserted filler neck, be included.

A further improvement can be obtained if a welding partner wavy is formed. Thus, starting from the in<b>figure 2</b> Solution illustrated, the wall pulled down the multilayer fuel tanks at the cone along and waved it be. This has the advantage that worn during welding at the peaks Material becomes; Schmelzeabtrag this is received by the wave troughs. By Of material to get at least in places up to the barrier layer of the tank, whereby the gap between the barrier layer of the tank and the barrier layer of the cone yet is further reduced.

Another example is the connection of a threaded flange <b>(11)</b> z. B. for fixing the pump unit to tank <b>(12)</b> called <b>(Figure 3).</b> The threaded either as shown here, from an unreinforced or reinforced with glass fibers of polybutylene terephthalate, or of a polyamide, which is optionally fiber-reinforced. The structure of the coextrudate <b>(7; 8; 9)</b> corresponds to that in the figure 2. (If the threaded Polyamide is, the layer is <b>(7)</b> also made of polyamide.) Depending on the embodiment of the Flange (planar or conical), the co-extruded intermediate layer is either of a film round punched (flat) or for example by deep drawing from a flat sheet produced (conical). The use of other materials such. As polyoxymethylene, Polyphthalamide, or polyphenylene sulfide is also inventively.

To weld the partners conically together, but still having a planar to weld surface work, it makes sense, the already existing surveys Tank which serve to stiffening to use. These are produced by a planar section opened, whereupon at this point, the welding is performed. This also makes is, for example compared to the embodiment shown in the <b>figure 1</b> shows the Permeation reduced.

The layer arrangement and thickness of the individual layers in the respective coextrusion is the adapt requirements for the welding process or insert molding. Especially have proved to be coextruded multilayer composites whose outer layers (ie, Layers which are connected to the connecting body or the connection member) have a thickness of 0.4 to 1.5 mm. Of course, however, other Layers distributions according to the invention.

Basically, the connecting element and the hollow body at least to the connecting layers consist of a thermoplastic. Any other layers or lots may optionally consist of a thermosetting plastics or metal. At the coextruded multilayer composite made all the layers of a thermoplastic Molding composition.

Using the invention, a permanently fixed connection between the connection element and hollow body are achieved while reducing environmentally harmful emissions.