DE102016216447B4 - Process for producing a shell-shaped molded plastic part and additive container - Google Patents

Abstract

Method for producing a shell-shaped molded plastic part (1) from thermoplastic by injection molding using fluid injection technology with at least one wall and with at least one fluid channel (5) extending in or on the wall, which is formed in one piece with the wall, wherein The method comprises the following method steps: - Providing an injection molding device with a tool with an article cavity (12) that defines the outer contour of the plastic molded part (1), at least one meandering first groove channel (14) being provided in a wall of the article cavity (12) , - Filling the article cavity (12) with a plasticized molding compound made of thermoplastic material, - Injecting a fluid into the filled article cavity (12) through the groove channel (14) while displacing a liquid core of the molding compound into at least a first overflow cavity (11a) of the tool , so that in the plastic molding (1) an integrated fluid channel (5) is formed, and- demoulding of the plastic molded part (1), characterized in that a part of the molding compound is displaced into a second overflow cavity (11b), a first and in the wall of the article cavity (12) a second groove channel section (14a, 14b) is provided, into which a fluid is injected at the same time, so that two sections of an integrated fluid channel (5) are formed, the two sections of the integrated fluid channel (5) after the thermoplastic molding compound has solidified together are connected using a prefabricated connecting bridge (17).

Description

The invention relates to a method for producing a shell-shaped molded plastic part from thermoplastic material by injection molding using fluid injection technology.

The invention further relates to an additive container for holding a urea solution for selective catalytic exhaust gas denitrification from shell-shaped plastic molded parts according to the method according to the invention, in particular an additive container comprising at least one shell-shaped plastic molded part of the type described above, for storing an aqueous additive or an aqueous liquid which has a first volume for Storage of the liquid and a second volume through which a heat transfer medium can flow, which is separate from the first volume, the second volume being designed as a meandering fluid channel extending on a container wall with a flow connection and a return connection for the heat transfer medium.

A generic container is for example from the DE 10 2012 020 040 B4 known. This publication relates to a device for storing and conveying an aqueous additive, in particular for catalytic exhaust gas denitrification in a motor vehicle, comprising a storage container which encloses a storage volume, at least one feed pump for the additive and means for heating at least parts of the storage volume or a separate melting volume, wherein the storage container is shown at least partially as a double wall, and wherein a volume of the storage container through which the heat transfer medium can flow comprises several channels, which can be flowed through individually or together with the heat transfer medium and define different heating zones in the bottom and / or in the wall of the storage container.

The production of a double-walled storage container is relatively complex. In the DE 10 2012 020 040 B4 To produce such a double-walled storage container, it is proposed to place several container shells or entire containers in one another with the interposition of spacers.

The heat transfer from the heat transfer medium to the volume enclosed by the storage container is in need of improvement, since the heat transfer medium first has to heat the container wall directly delimiting the storage medium.

Another liquid container for motor vehicles is from, for example EP 1 473 447 A1 known. This document relates to a liquid container for motor vehicles, in particular for an aqueous urea solution, in which a heater for the urea solution is integrated in the container wall, in such a way that no heating parts protrude into the container interior in which the liquid is located. The heating consists of heating pipes which are connected to a cooling circuit of the internal combustion engine. As an alternative to the heating pipes through which the heat transfer medium of the cooling circuit flows, the publication proposes the use of an electrical heater. The heater should preferably be installed so that no parts of the heater or the heating pipes protrude into the interior of the container.

Such a configuration of the heating means that the heat transfer from the heat transfer medium to the liquid in the storage container or to ice that may be located there is not optimal.

A method according to the preamble of claim 1 is known from the DE 10 2011 055 311 A1 known.

A comparable procedure is out of the JP 2013-056481 A known.

JP H11-114 997 A describes a method in which a resin is cooled through a cavity surface to achieve high viscosity and a resin is thermally insulated through a cavity surface side to achieve low viscosity.
US 6 367 503 B1 describes a tank in which a bead is connected to the wall of a molded plastic part by means of a web forming a material bridge.

The invention is therefore based on the object of providing a method for producing a shell-shaped molded plastic part with an integrated heating wall which is relatively simple. The invention is furthermore based on the object of providing an additive container made of shell-shaped molded plastic parts which are suitable for storing and heating an aqueous additive using a liquid heat transfer medium, the additive container preferably being designed in such a way that an optimal heat transfer from the heat transfer medium to the stored liquid is guaranteed.

The object is first achieved by a method having the features of claim 1.

Finally, the object is achieved by an additive container for holding a Urea solution for selective catalytic exhaust gas denitrification from shell-shaped molded plastic parts with the features of claim 4.

Advantageous embodiments of the invention are covered by the respective subclaims.

• - Bereitstellen einer Spritzgießvorrichtung mit einem Werkzeug mit einer Artikelkavität, die die Außenkontur des Kunststoffformteils definiert, wobei in einer Wand der Artikelkavität wenigstens einen mäanderförmig verlaufender erster Nutkanal vorgesehen ist,
• - Füllen der Artikelkavität mit einer plastifizierten Formmasse aus thermoplastischen Kunststoff,
• - Injizieren eines Fluids in die gefüllte Artikelkavität durch den Nutkanal unter Verdrängung einer flüssigen Seele der Formmasse in wenigstens eine erste Überlaufkavität des Werkzeuges, sodass in dem Kunststoffformteil ein integrierter Fluidkanal ausgebildet wird, und
• - Entformen des Kunststoffformteils. Die Fluid-Injektionstechnik ist grundsätzlich zur Herstellung von spritzgegossenen Rohren aus thermoplastischen Kunststoff bekannt.

One aspect of the invention relates to a method for producing a shell-shaped plastic molded part from a thermoplastic by injection molding using fluid injection technology with at least one wall and with at least one fluid channel which extends in or on the wall and is formed integrally with the wall , the method comprising the following steps:

• Providing an injection molding device with a tool with an article cavity, which defines the outer contour of the molded plastic part, at least one meandering first groove channel being provided in a wall of the article cavity,
• Filling the article cavity with a plasticized molding compound made of thermoplastic,
• Injecting a fluid into the filled article cavity through the groove channel, displacing a liquid core of the molding compound into at least one first overflow cavity of the tool, so that an integrated fluid channel is formed in the plastic molded part, and
• - De-molding of the molded plastic part. The fluid injection technology is basically known for the production of injection molded pipes made of thermoplastic.

Injection molding processes using fluid injection technology as such are mainly known for the production of pipes that extend in a straight line. The fluid injection technique involves injecting a jet of water under high pressure into an article cavity of an injection molding tool filled with plasticized plastic, whereby a liquid core of the thermoplastic is displaced by means of the water into an overflow cavity or secondary cavity, which is released after the polymer filling via slide valves.

For injection molding, at least one extrusion device for the plasticization of thermoplastic plastic and a tool with an article cavity are used, which specifies the outer shape of the shell-shaped molded plastic part. In the method according to the invention, the article cavity is expediently first filled in a single closure with a corresponding amount of thermoplastic and plasticized molding compound. By means of an injection device, a fluid will then be injected into the filled article cavity under high pressure, with displacement of a liquid core of the molding compound into at least one overflow cavity of the tool. The length of the groove channel and the amount of the molding compound displaced are selected such that this process is completed before the plasticized molding compound has completely crystallized.

In this way, an integrated fluid channel can be formed, which is molded in one piece into a wall of the shell-shaped molded plastic part or molded onto it.

A meandering groove channel is preferably provided in the wall of the article cavity, which defines the contour of a meandering rib or a meandering bead. Meandering in the sense of the present application means as much as loop or serpentine. The groove channel can run over parts of the shell-shaped molded plastic part.

Any thermoplastic polymer can be provided as a thermoplastic molding composition in the sense of the invention, for example a thermoplastic plastic can be provided as a thermoplastic molding composition, which is selected from a group comprising polyethylene, high density, polyamide, polyamide 6, polyamide 12, polyurethane, polycarbonate, Acrylonitrile-butadiene-styrene copolymer, polyketones, polystyrene, polypropylene, thermoplastic elastomers based on olefins, crosslinked thermoplastic elastomers based on olefins, thermoplastic elastomers based on urethane, thermoplastic polyester elastomers and thermoplastic copolymers.

The aforementioned method steps are preferably carried out in the order in which they are listed.

In the method according to the invention, it is provided that a subset of the molding compound is displaced into a second overflow cavity. Basically, this takes into account the knowledge that the formation of a relatively long meandering fluid channel could possibly take a time that would be greater than the crystallization time of the plasticized molding compound. If an overflow cavity is already provided on a section of the groove channel, the displaceable volume flow of plasticized molding compound can be increased overall, so that the injection time for the fluid can be shortened.

For example, a first subset of the molding compound can first be displaced into the first overflow cavity, then a second subset of the molding compound can be displaced into the second overflow cavity to be ousted. The first overflow cavity can, for example, be connected to the groove channel after a first partial length of the groove channel. The liquid core of the molding compound is then displaced into the first overflow cavity until it is completely filled. The displaced material is then displaced into the second overflow cavity which is expediently provided at the end of the groove channel. The volume of the first overflow cavity is dimensioned such that it only takes up the first subset of the molding compound. A slide or a valve for closing the first overflow cavity is not required in this variant.

The first overflow cavity can alternatively be closed by means of a valve after receiving a partial filling, preferably half the filling.

In another variant of the method according to the invention it is additionally provided that a first and a second groove channel or a first and a second groove channel section are provided in the wall of the article cavity, in which a fluid is injected at the same time, so that two sections of an integrated fluid channel are formed . The sections formed in this way can be connected to one another, for example, after the thermoplastic molding compound has solidified, preferably using a prefabricated cable bridge which is welded to the sections of the fluid channel thus produced.

It is preferably provided that a flow connection and a return connection for the fluid channel are integrally molded onto the shell-shaped molded plastic part. The connections can be designed, for example, in the form of connection nipples with a profile for strangling a connection line.

Water is preferably used as the fluid. In the context of the invention, however, the use of a gaseous injection medium is also useful and possible.

A variant of the invention relates to an additive container for holding a urea solution for selective catalytic exhaust gas denitrification. The additive container consists of shell-shaped molded plastic parts made of thermoplastic material for storing an aqueous additive or an aqueous liquid, which has a first volume for storing the liquid and a second volume through which a heat transfer medium can flow, which is separate from the first volume, the second volume being meandering fluid channel extending on a container wall is formed with a flow connection and a return connection, the additive container being characterized in that the fluid channel is an integral part of the container wall and is molded onto the container wall or molded into the container wall.

Such an additive container is intended for fixed installation in a motor vehicle. At least one container wall of the container is designed as a heating wall for limiting the liquid volume, the meandering fluid channel running in the heating wall preferably being connected to the heat transfer circuit of the internal combustion engine with a flow connection and with a return connection.

For example, a container wall forming the bottom of the additive container can be formed with a meandering fluid channel. Additionally or alternatively, side walls of the additive container can also be designed accordingly. The additive container is expediently composed of exactly two shell-shaped plastic molded parts, a lower shell-shaped plastic molded part being formed with a meandering fluid channel extending in a container wall forming the bottom of the additive container. An upper part of the additive container can be formed, for example, from a conventional shell-shaped molded plastic part.

The fluid channel of the shell-shaped molded plastic part according to the invention is formed from the thermoplastic plastic of the wall, i.e. molded in one piece or molded in one piece or integral in the sense of the present invention excludes the registration of separate components in the form of pipes, heating strikes or heating coils or heating wires.

In the case of the molded plastic part according to the invention, it is provided that the fluid channel runs in a protruding bead which extends on the wall of the molded plastic part. This ensures that the fluid channel is at least partially flowed around the fluid channel, so that an optimal heat transfer from the heat transfer medium circulating through the fluid channel to the stored and to be heated liquid is ensured.

In a preferred variant of the shell-shaped molded plastic part according to the invention, it is provided that the bead is connected to the wall of the molded plastic part by means of at least one web forming a material bridge. In this way, the fluid channel can be largely enclosed with the liquid to be stored. Thanks to the web, the bulge protrudes relatively far into the volume to be stored.

In order to prevent the bead from hindering the distribution of the liquid to be stored in the additive container, it can be provided that the web has window-like openings. Alternatively, provision can be made to connect the bead to the wall of the molded part by means of a plurality of material bridges or webs.

The shell-shaped molded plastic parts are expediently injection molded from thermoplastic plastic, using the fluid injection technique or water injection technique described above. A gas can of course also be used as the fluid. The fluid channel according to the invention can also be produced using the so-called projectile injection technique.

The fluid channel preferably extends on a side of the container wall facing the first volume, the fluid channel running in a bead-shaped profile on the container wall. In this way it is possible for the fluid channel to be flowed around over part of its circumference by the fluid to be stored, so that the heat transfer to the fluid is optimal.

The invention is explained below with reference to an embodiment shown in the drawings.

• 1 eine perspektivische Darstellung eines schalenförmigen Kunststoffformteils,
• 2 eine weitere perspektivische Darstellung des schalenförmigen Kunststoffformteils gemäß 1,
• 3 einen Querschnitt durch das schalenförmige Kunststoffformteil,
• 4 einen vergrößerten Teilschnitt durch einen Fluidkanal des schalenförmigen Kunststoffformteils,
• 5 eine schematische Querschnittsansicht durch Teile der gefüllten Artikelkavität,
• 6 eine Schnittansicht durch einen Anschluss des Fluidkanals als Vorlaufanschluss oder Rücklaufanschluss für ein Wärmeträgermedium,
• 7 einen Querschnitt durch ein schalenförmiges Kunststoffformteil gemäß einem zweiten Ausführungsbeispiel der Erfindung,
• 8 eine Draufsicht auf das in 7 dargestellte schalenförmige Kunststoffformteil,
• 9 eine Ansicht des schalenförmigen Kunststoffformteils gemäß der Erfindung, die die Anschlüsse zur Wasserinjektion und an die Überlaufkavitäten veranschaulicht und
• 10 eine der 9 entsprechende Ansicht, die die Wasserinjektion in erste und zweite Nutkanalabschnitte der Artikelkavität veranschaulicht.

Show it:

• 1 1 shows a perspective illustration of a shell-shaped molded plastic part,
• 2nd a further perspective view of the shell-shaped molded plastic part according to 1 ,
• 3rd a cross section through the shell-shaped molded plastic part,
• 4th 3 shows an enlarged partial section through a fluid channel of the shell-shaped molded plastic part,
• 5 2 shows a schematic cross-sectional view through parts of the filled article cavity,
• 6 2 shows a sectional view through a connection of the fluid channel as a flow connection or return connection for a heat transfer medium,
• 7 3 shows a cross section through a shell-shaped molded plastic part according to a second exemplary embodiment of the invention,
• 8th a top view of the in 7 illustrated bowl-shaped molded plastic part,
• 9 a view of the bowl-shaped molded plastic part according to the invention, illustrating the connections for water injection and to the overflow cavities and
• 10th one of the 9 corresponding view illustrating the water injection into first and second groove channel sections of the article cavity.

1 shows a bowl-shaped molded plastic part 1 , which forms the lower shell of an additive container, not shown, for storing an aqueous additive in a motor vehicle. The additive container can be provided, for example, as a urea container for the selective catalytic exhaust gas denitrification on these motor vehicles.

The shell-shaped molded plastic part 1 is designed as an injection-molded half-shell made of thermoplastic, for example made of HDPE. The shell-shaped molded plastic part 1 includes sidewalls 2nd as well as a circumferential mounting flange 3rd for joining with another bowl-shaped molded plastic part to a closed additive container which encloses a storage volume for the additive. A floor wall 4th of the shell-shaped molded plastic part 1 is a heating wall with an integrated fluid channel 5 educated. The fluid channel 5 extends from a flow connection 6 to a return connection 7 through which the fluid channel 5 can be connected to a heat transfer circuit of an internal combustion engine. The fluid channel 5 extends in the manner of a heating coil in a serpentine shape on the bottom wall of the shell-shaped molded plastic part 1 , the fluid channel 5 bead-shaped in that of the shell-shaped plastic molding 1 limited volume protrudes.

The shell-shaped molded plastic part 1 according to the 1 and 2nd was obtained by injection molding thermoplastic, preferably by injection molding HDPE using the so-called fluid injection technique. In the 1 and 2nd are the location of a sprue 8th as well as an enema 9 and a spout 10th shown for water injection. With 11 an overflow cavity in the injection molding tool is shown schematically.

The shell-shaped molded plastic part 1 is produced, for example, from one shot, ie with a filling of the tool, not shown. Lupolen GX 5038, for example, can be used as HDPE. This is a trade name.

A schematic sectional view through an injection mold filled with a thermoplastic molding compound in the area of an article cavity 12th of the injection mold is in 5 shown. In the article cavity 12th delimiting wall 13 is a groove channel 14 formed the outer contour of the fluid channel 5 certainly.

The enema 9 for water injection opens at one end of the groove channel 14 into the article cavity 12th , the spout 10th is at the other end of the groove channel 14 in the article cavity 12th connected. After filling the article cavity 12th With the plasticized molding compound, water is injected into the groove channel at a pressure of approximately 200 megapascals (MPa) using an injection device of the injection mold 14 pressed in. The water displaces within the groove channel 14 a liquid soul of the molding compound in the overflow cavity 11 which, in a variant of the method according to the invention, is dimensioned in such a way that it can accommodate the entire displaced molding compound. This results in the formation of the fluid channel 5 a, such as in 4th is shown. The fluid channel 5 forms one to one side of the shell-shaped molded plastic part 1 protruding bead 15 . This side of the shell-shaped molded plastic part 1 forms the side facing the storage volume of the additive container to be manufactured, as is also the case in the sectional view in FIG 3rd can be seen.

In the injection mold, the method according to the invention is also in the area of the inlet 9 and in the area of the outlet 10th of the hot runner (fluid channel 5 ) Connection nipple 16 integrally formed, the a flow connection and a return connection of the fluid channel 5 form. The shape of the connection nipple 16 is the in 6 shown sectional view.

Reference is now made to the 9 and 10th , which are each schematic of the course of the groove channel 14 in the article cavity 12th and the location of the inlet 9 and first and second overflow cavities 11a , 11b illustrate.

Unlike when using 1 The method variant explained is in another method variant of the invention, which is based on 9 a first and a second overflow cavity are explained 11a , 11b provided, the first overflow cavity 11a on half the flow path length of the groove channel 14 in the groove channel 14 flows and the second overflow cavity 11b to the end of the groove channel 14 connected. In this variant of the method, a subset of the plasticized molding compound is first placed in the first overflow cavity 11a repressed. As soon as the water injected under high pressure is half the flow path within the groove channel 14 has covered, the further molding compound, ie a second subset of the molding compound in the second overflow cavity 11b displaced until the fluid channel 5 is fully trained. This makes it possible to obtain a higher volume flow of plasticized molding compound from the groove channel 14 to displace, so that for example a flow path length of the fluid channel 5 of more than 1.9 m can be achieved. The achievable flow path length depends on the crystallization time of the polymer melt. As long as the polymer melt (plasticized molding compound) is not yet crystalline, plastic molding compound can be displaced by water injection.

Another procedure is based on 10th illustrated. In this variant of the tool it is provided that the groove channel 14 in a first and a second groove channel section 14a , 14b is divided. The first and the second groove channel section 14a , 14b are acted upon in parallel with water. As in the exemplary embodiment of the method described above, the tool comprises a first overflow cavity 11a and a second overflow cavity 11b . At the first groove channel section 14a is a first enema 9a connected to the second groove channel section 14b is a second enema 9b connected. Water under high injection pressure of, as already mentioned, about 200 MPa becomes the first enema 9a and the second enema 9b parallel, ie abandoned at the same time, so that two fluid channel sections are formed in parallel, which also means the flow path length of the fluid channel 5 is significantly extended. The two sections of the fluid channel 5 are by means of a connecting bridge 17th to a single fluid channel 5 connected.

The 7 and 8th show a variant of the design of the shell-shaped molded plastic part 1 according to the invention, wherein the fluid channel 5 by means of bars 18th , which form material bridges, with a wall of the shell-shaped molded plastic part 1 connected is. In this way it is ensured that the meandering bead 15 that the fluid channel 5 encloses, relatively far from the bottom wall 4th of the shell-shaped molded plastic part 1 protrudes and thus dips relatively deep into the stored and heated liquid.

So that the bead 15 which in the from the shell-shaped plastic molded parts 1 formed additive container does not form an obstacle to the stored liquid is a multitude of webs 18th provided as hinted at in 8th is shown. Instead of a multitude of bridges 18th Window-like openings can also be provided in a continuous web.

At the in 7 variant shown are the webs 18th and the mess 15 symmetrical, they can also be asymmetrical to improve the ability to demold the shell-shaped molded plastic part 1 from the injection mold.

Reference list

1

bowl-shaped molded plastic part

2nd

side walls

3rd

Mounting flange

4th

Bottom wall

5

Fluid channel

6

Flow connection

7

Return connection

8th

Sprue

9

enema

9a

first enema

9b

second enema

10th

Spout

10a

first outlet

10b

second outlet

11

Overflow cavity

11a

first overflow cavity

11b

second overflow cavity

12th

Article cavity

13

Wall of the tool

14

Groove channel

14a

first groove channel section

14b

second groove channel section

15

bead

16

Connection nipple

17th

Connecting bridge

18th

Walkways

Claims (5)

Process for producing a shell-shaped molded plastic part (1) from thermoplastic by injection molding using fluid injection technology with at least one wall and with at least one fluid channel (5) extending in or on the wall, which is formed in one piece with the wall, wherein The method comprises the following method steps: - Providing an injection molding device with a tool with an article cavity (12) that defines the outer contour of the molded plastic part (1), at least one meandering first groove channel (14) being provided in a wall of the article cavity (12) , - Filling the article cavity (12) with a plasticized molding compound made of thermoplastic material, - Injecting a fluid into the filled article cavity (12) through the groove channel (14) while displacing a liquid core of the molding compound into at least a first overflow cavity (11a) of the tool , so that molded in the plastic eil (1) an integrated fluid channel (5) is formed, and - demolding of the plastic molding (1), characterized in that a part of the molding compound is displaced into a second overflow cavity (11b), a first in the wall of the article cavity (12) and a second groove channel section (14a, 14b) are provided, into which a fluid is injected at the same time, so that two sections of an integrated fluid channel (5) are formed, the two sections of the integrated fluid channel (5) after the thermoplastic molding compound has solidified are connected to one another using a prefabricated connecting bridge (17). Procedure according to Claim 1 , characterized in that first a first subset of the molding compound is displaced into the first overflow cavity (11a) and that a second subset of the molding compound is then displaced into the second overflow cavity (11b). Procedure according to Claim 1 or 2nd , characterized in that water is used as the fluid. Additive container for holding a urea solution for selective catalytic exhaust gas denitrification manufactured according to one of the Claims 1 - 3rd , a first volume for storing the liquid and a second volume through which a heat transfer medium can flow, which is separate from the first volume, made of shell-shaped molded plastic parts (1) made of thermoplastic material, at least one shell-shaped molded plastic part comprising at least one wall serving as a heating wall is designed to limit a liquid volume, the wall having at least one fluid channel (5) extending in a meandering manner over the heating wall for guiding a heat transfer medium, the fluid channel (5) having a flow connection (6) and a return connection (7) for the heat transfer medium, wherein the fluid channel (5) is molded in one piece into the wall of the molded plastic part (1) or molded onto it, the fluid channel (5) extending on a side of the container wall facing the first volume and the fluid channel (5) in a bead-shaped profile on the Container wall runs, the fluid channel ( 5) extends in a protruding bead (15) extending on the wall of the plastic molded part (1), characterized in that the bead (15) is connected to the wall of the plastic molded part by means of at least one web (18) forming a material bridge. Additive container after Claim 4 , characterized in that the web (18) has window-like openings.

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