Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
  • B29C45/14778—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles the article consisting of a material with particular properties, e.g. porous, brittle
  • B29C45/14786—Fibrous material or fibre containing material, e.g. fibre mats or fibre reinforced material
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/12—Moulds or cores; Details thereof or accessories therefor with incorporated means for positioning inserts, e.g. labels
  • B29C33/123—Moulds or cores; Details thereof or accessories therefor with incorporated means for positioning inserts, e.g. labels for centering the inserts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
  • B29C45/14065—Positioning or centering articles in the mould
  • B29C45/14073—Positioning or centering articles in the mould using means being retractable during injection
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
  • B29C45/14336—Coating a portion of the article, e.g. the edge of the article
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
  • B29L2031/00—Other particular articles
  • B29L2031/712—Containers; Packaging elements or accessories, Packages
  • B29L2031/7172—Fuel tanks, jerry cans

Definitions

• a method of injecting a tank wall comprising a localized reinforcing ply is provided.
• the present invention is concerned with methods of manufacturing objects having thin walls and requiring localized reinforcements. More particularly, the invention relates to a method of manufacturing by injection of tanks for equipping motor vehicles.
• thermo molding The manufacture of tanks by thermo molding is widely known in the industry and, traditionally, operates in a single operation during which successively is carried out by injection a cylindrical web of thermoplastic material forming a parison, it closes a mold around said parison still hot and plastic, and a gas is injected under pressure so as to press the parison against the walls of the mold.
• These localized reinforcements are then in the form of fabrics formed of fibers or reinforcing threads, oriented or not, and impregnated with a thermoplastic material capable of fusing with the material forming the reservoir.
• the reinforcing fibers may be of synthetic, natural or metallic origin.
• the laying of a localized reinforcement can be done, according to a first method, by applying the reinforcement on the external wall of the tank after the tank has been extracted from the mold and cooled.
• the reinforcement is brought to a temperature close to the melting temperature of the thermoplastic material that composes it, and is then applied under pressure to the wall of the pre-heated tank.
• a second method when use is made of a device for blow molding a parison in a mold, the laying of localized reinforcements is done before the introduction of the parison into the mold.
• the reinforcement is brought before a temperature close to the melting temperature of the material impregnating the son that compose it and, using a suitable device, is placed on the outer surface of the parison or directly in the mold in the zone intended to form the tank part requiring a particular reinforcement.
• This method is well suited for the production of large capacity tanks with high loads and which require thick reinforcements.
• thermoplastic material in a mold designed for this purpose.
• This embodiment makes it possible, among other things, to manufacture reservoirs at relatively low costs.
• the invention proposes to provide a particularly economical solution for producing a wall, intended for example to form the wall of a tank, by injection under pressure and at a predetermined temperature of a thermoplastic material in a mold, said wall comprising at least one localized reinforcing ply of predetermined thickness and formed of reinforcement son embedded in a thermoplastic material compatible with the thermoplastic material forming said wall and having a predetermined melting temperature.
• the method according to the invention is characterized in that the reinforcing ply is deposited in the injection mold at a temperature substantially equal to the ambient temperature of a workshop and that the injection temperature of the thermoplastic material forming the wall, the melting temperature of the thermoplastic material coating the reinforcing threads and the thickness of the reinforcing ply are adjusted so that the material coating the reinforcing threads is melted during the injection phase.
• the method makes it possible to overcome all the movements of material in the mold.
• the method according to the invention may also comprise multiple implementation modes making it possible to optimize the performance of the final product, the characteristics of which, taken separately or in combination, are as follows:
• the temperature of the workshop is between 15 ° C and 30 ° C.
• thermoplastic material forming the wall and the thermoplastic material coating the reinforcing threads are chosen from materials such as
• HDPE high polyethylene, polyamides or polyphthalamides.
• the reinforcing ply comprises entangled reinforcing threads.
• the reinforcement ply comprises one or more plies of reinforcing threads, each ply of reinforcing threads being composed of reinforcing threads parallel to each other, and the plies of reinforcing threads being arranged so that the reinforcing threads of a ply together with the reinforcing threads of the other plies form definite and non-zero angles.
• the reinforcing ply comprises woven reinforcement threads.
• the thickness of the reinforcement ply is less than or equal to 0.7 mm, and preferably less than or equal to 0.5 mm.
• the reinforcing threads are embedded between two films of thermoplastic material, so that the thickness of thermoplastic material on the back of the reinforcing threads is less than or equal to 0.2 mm, and preferably less than or equal to 0.05 mm.
• the difference between the melting temperature of the thermoplastic material coating the reinforcing son of the reinforcement ply and the injection temperature of the thermoplastic material forming said wall is between 60 ° C and 115 ° C.
• the injection temperature of the thermoplastic material forming said wall is between 190 ° C. and 330 ° C.
• a pressurization time of the material in the mold is greater than 0.3 minutes and preferably greater than 0.5 minutes.
• a temperature of the mold during the introduction of the reinforcing ply is between 30 ° C and 140 ° C.
• the reinforcing ply is preformed to the final shape that it is desired to impart to it in the mold, before it is introduced into the mold.
• the reinforcing ply is anchored to a pre-established position in the mold by means of a plurality of needles and / or retractable shims, able to disappear at the end of the injection phase of the material forming said wall.
• a height of the needles and / or wedges is adjusted so as to position the reinforcing ply at predefined and non-zero distances from the walls of the mold.
• Figure 1 shows a general and schematic view of an injection press.
• FIG. 2 represents a schematic sectional view of the fixed part and the mobile part of the injection mold comprising means for positioning the reinforcing ply.
• FIG. 3 represents the fixed plate of a mold in which a reinforcing ply has been positioned before closing the mold.
• FIG. 4 represents a perspective view of the bottom wall of a tank, comprising a reinforcing ply, and obtained using the method according to the invention.
• FIG. 1 represents a standard-type injection press 1 comprising an injection screw 10 rotatably mounted in a heating sleeve 11. Upstream of the screw is a receptacle 12 in which the granules of material to be injected are introduced.
• the screw opens, via an injection nozzle 15, into an injection mold comprising a fixed plate 13 and a movable plate 14 whose inner space defines the shape and the volume of the part 20 to be injected. at high temperature.
• Cooling circuits 16 are provided in the fixed plate and the mobile plate to reduce the temperature of the material after the injection phase so as to allow solidification, before extraction, and just after the opening of the mold by translation. of the movable plate 14.
• This device makes it possible to produce parts made of thermoplastic material of high quality with a high efficiency. It turns out to be particularly suitable for the realization of medium or reduced size tanks, which will be achieved by injecting two separate parts to be joined, for example by heat sealing, to form the final reservoir.
• the tank is made of thermoplastic material.
• Thermoplastic means any thermoplastic polymer, including thermoplastic elastomers, and mixtures thereof.
• the term "polymer” denotes both homopolymers and copolymers (especially binary or ternary). Examples of such copolymers are, but are not limited to: random copolymers, block copolymers, block copolymers and graft copolymers.
• thermoplastic polymer or copolymer whose temperature of melting is below the decomposition temperature are suitable.
• Synthetic thermoplastics having a melting range spread over at least 10 degrees Celsius are particularly suitable. Examples of such materials are those having a polydispersion of their molecular weight.
• polystyrene resin polystyrene resin
• thermoplastic polyesters polyketones
• polyvinyls halogenated polyvinyls
• PVDH polyvinyl fluoride
• PA polyamides
• a mixture of polymers or copolymers may also be used, as well as a mixture of polymeric materials with inorganic, organic and / or natural fillers such as, for example, but not limited to: carbon, clays, salts and the like. inorganic derivatives, natural or polymeric fibers.
• These materials may contain additives such as stabilizers, reinforcing fillers or plasticizers.
• PE polyethylene
• HDPE high density polyethylene
• the reinforcing ply is in the form of fibers or reinforcement son embedded in a thermoplastic material also called prepreg (pre-impregnated).
• son or reinforcing fibers prepreg can be of synthetic origin, natural or metallic.
• Prepreg is an alternative to reinforcements or so-called dry fabrics, without any coating material and made of synthetic or natural fibers or metal strands.
• the reinforcement can be in many forms; it is generally a plate comprising cut fibers or long fibers or continuous fibers which may or may not be woven.
• the cut fibers have final lengths of a few tens / hundreds of microns.
• the residual lengths are a few millimeters.
• Continuous fibers or continuous filaments are used in the case where the length of the fibers used is several centimeters.
• the son plies can be simply superimposed on each other, or include weft son and chain son in the manner of a fabric.
• the most commonly used woven reinforcing plies are formed of two layers of yarn woven together.
• Continuous fibers are, however, preferred and in particular nonwoven continuous fibers and randomly distributed (so-called multidirectional fibers). While being less expensive than long woven fibers, they have the advantage of distributing the stresses more uniformly. They also have the advantage, in the context of the invention, of having a lower density of fibers, ie a higher proportion of voids which are advantageously filled with thermoplastic coating material in order to facilitate the welding .
• the fiber content in the reinforcement is preferably at least 30%, preferably at least 60% or even at least 45% of the total mass of the prepreg.
• These fibers may be based on glass, carbon, a polymer (such as a polyamide, for example aromatic such as aramid), or even be natural fibers such as hemp or sisal. It is preferably glass fibers (type E, S or other).
• the fibers of the fibrous reinforcement according to the invention are preferably compatible with the thermoplastic material and therefore, as a rule, compatible with polyolefins and in particular with HDPE. In order to obtain this compatibility, it is possible to size (surface treat) the fibers with a compatibilizing substance such as a silane.
• a reactive HDPE binder can also be used. In this context, reactive functions of maleic anhydride type can be advantageously used.
• the fibrous reinforcement comprises a thermoplastic material compatible with that of the reservoir, or even identical thereto.
• a thermoplastic material compatible with that of the reservoir, or even identical thereto.
• it is usually polyethylene and in particular HDPE.
• thermoplastic material is preferably melted around / in the mass of fibers so as to form a homogeneous sheet / plate having on at least a portion of its surface, thermoplastic material so as to facilitate the welding.
• this can be done by compression molding, injection molding, projection molding, vacuum molding or even calendering.
• the method of producing the reinforcement will be compression molding (continuous pressing process between 2 rolls) or projection molding. Prepregs reinforced with continuous woven fibers give good results with this method.
• the reinforcement covers at least part of an area where a component is fixed (for example: the filling chute where the filling pipe is just fixed) and includes a barrier layer so that it fulfills both a reinforcing function (in this often fragile zone) and a waterproofing function.
• the reinforcement is advantageously obtained by compression molding a multilayer sheet including a barrier layer (and preferably a sheet comprising an EVOH layer between two layers of HDPE), a fiber mat (from preferably: non-woven and randomly distributed continuous glass fibers) and a HDPE sheet.
• the mechanical strength imparted to the tank bottom is related to the type of yarn, the type of weaving and the diameter of the yarns used.
• the son are coated between two films of material, so as to impregnate the free spaces between the son and to form a thin layer on the back of the son, and to promote their adhesion to the material forming the object to be reinforced.
• the material coating the wires is chosen to be compatible with the injected material forming the wall to be injected. That is to say that the impregnating material of the son is able to bond intimately by melting with the injected material. It is therefore preferable to choose a material of the same nature as the material forming the wall. In the case of support for the present description, a prepreg impregnated with an HDPE satisfies this condition.
• the reinforcing ply is introduced into the mold at the workshop temperature which is usually between 15 ° C. and 30 ° C.
• the method according to the invention is therefore based on the fact that the amount of energy required to ensure the melting of the material forming the reinforcing ply is provided by the injected material in the liquid state.
• This thermal energy therefore comprises at least the portion of energy to ensure the temperature rise of the reinforcement to the melting temperature of the material that composes it, and the energy to be supplied to ensure the melting of this material, so that it mixes, at least on a surface layer, with the injected material.
• a first factor lies in the choice of the mass of the prepreg, and therefore its thickness.
• a good compromise for low capacity tanks is obtained with a prepreg having a total thickness of less than 0.7 mm and preferably less than 0.5 mm.
• thermoplastic material on the back of the wire is less than 0.2mm and preferably less than 0.05mm.
• This value, measured in a direction normal to the surface of the prepreg, corresponds to the smallest thickness of material available between a wire and said surface.
• a second factor to take into account is the melting temperature of the material forming the prepreg which should be as low as possible relative to the temperature of the injected material at the time of its introduction into the mold. It appears in this regard that the difference between the melting temperature of the thermoplastic material coating the reinforcing son and the injection temperature of the thermoplastic material forming said wall must be between 60 ° C and 115 ° C.
• the third factor is the injection temperature of the material into the mold.
• this temperature for a material of HDPE type is usually between 190 ° C and 245 ° C, and can go up to 280 ° C for some grades of HDPE.
• the melting temperature of the material coating the prepreg son should usefully be less than 140 ° C or even 120 ° C, which is entirely compatible with the nature of the materials used. To adjust the melting temperature of the HDPE forming the prepreg, it adjusts its grade and the length of the polymer chains that compose it.
• the injection temperature can nevertheless reach 330 ° C in the case of a material such as PA6 or PPA.
• the melting temperature of the material coating the reinforcing threads of the prepreg can then be adjusted accordingly.
• the fourth factor relates to the cooling power of the mold, and consequently the thermal energy that is removed from the injected material and can not be restored to prepreg.
• This last factor is particularly difficult to regulate in that it also determines the demolding temperature and the cycle time of the machine.
• a temperature below 40 ° C provides an acceptable result, and a temperature of 30 ° C is a preferred choice.
• the mold can reach much higher temperatures, of the order of 135 ° C or even 140 ° C, at the time of introduction of the prepreg,
• the last factor relates to the duration of time under pressure, before opening the mold. This time depends on the thickness of the injected wall and the temperature of the mold at the beginning of the injection. Good results are obtained with a duration under pressure greater than 0.3 minutes and preferably greater than 0.5 min.
• a relative increase in the thickness of the prepreg will result in a greater need for thermal energy, which can be satisfied by an increase in the injection temperature or by an increase in the temperature of the mold and the duration under pressure.
• the choice of the melting temperature of the material forming the prepreg is then adjusted accordingly.
• Another advantage that can be obtained at a lower cost is the possibility of place the sheet at a precise distance from each of the inner walls of the mold.
• wedges 17 or retractable needles 16 on which the reinforcing ply 30 is anchored in a precise geometric position.
• the needles are adjusted to a predetermined height h relative to the inner walls of the mold. This distance h is not necessarily constant. A few tenths of seconds before the end of the injection of the material, the needles or wedges are then retracted and the final volume of the wall is introduced into the mold and put under a given set pressure.
• This embodiment also makes it possible to optimize the resistance of the wall as a function of the forces undergone, in that it becomes possible to place the prepreg at an optimum location with respect to the neutral fiber of the wall.
• Figure 3 shows the prepreg 30 after installation on the wedges, just before the closure of the movable plate and the injection of the material into the mold.
• FIG. 4 illustrates the final result after injection of the portion of the tank bottom 21 comprising an opening around which said reinforcement 30 is installed.
• Another advantage of the invention lies in the fact that, when the part of the wall intended to be reinforced is not a flat or developable surface, it is possible to impart to the prepreg, by any method that is not the same. object of the present invention, a determined permanent deformation.
• the reinforcing ply is then preformed to the final shape that it is desired to impart to it in the mold. It is then avoided that the movements of material related to the movements of the reinforcing threads occur during the shaping of the sheet in the mold. The geometric characteristics of the molded wall are improved accordingly.
• the invention is not limited to the embodiments that are the subject of the present description and other embodiments will become clear to those skilled in the art. It is in particular possible to vary the nature of the injected material, and in the foregoing explanations will be found all of the information likely to guide a person skilled in the art to produce by injection a wall comprising a reinforcement.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)
• Casting Or Compression Moulding Of Plastics Or The Like (AREA)
• Moulding By Coating Moulds (AREA)

Applications Claiming Priority (2)

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Citations (1)

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• 2014
  • 2014-12-26 WO PCT/FR2014/053563 patent/WO2015101748A1/fr active Application Filing
  • 2014-12-26 US US15/108,956 patent/US20160354957A1/en not_active Abandoned
  • 2014-12-26 CN CN201480071783.0A patent/CN105873739B/zh not_active Expired - Fee Related
  • 2014-12-26 EP EP14833523.5A patent/EP3089855A1/fr not_active Withdrawn

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