EP4669508A1

EP4669508A1 - DEVICE FOR INJECTING A FOAMABLE MATERIAL INTO A MOLD AND METHOD FOR PRODUCEING FLAT FOAMED COMPONENTS

Info

Publication number: EP4669508A1
Application number: EP24705707.8A
Authority: EP
Inventors: Philipp BEISER; Christina SCHWARZE; Carsten Ellersiek
Original assignee: BASF SE
Current assignee: BASF SE
Priority date: 2023-02-24
Filing date: 2024-02-23
Publication date: 2025-12-31
Also published as: WO2024175771A1; MX2025009934A; CN120752125A; JP2026507077A

Abstract

220924WO01 16 A device for injecting a foamable material into a mold and a process for producing flat foamed components 5 Abstract The invention relates to a device for injecting a foamable material into a mold (27) for forming flat foamed components, comprising a tube (31) having a first end (35) with which the tube can be connected to a nozzle (21) of an injection device, and a stream separator (33) for dividing 10 the foamable material into at least two partial streams, the stream separator (33) being placed at a second end (37) of the tube (31) opposite of the first end (35). The invention further relates to a process producing flat foamed components using such a device. 15 (Figure 3)

Description

A device for injecting a foamable material into a mold and a process for producing flat foamed components

Description

The invention relates to a device for injecting a foamable material into a mold for forming flat foamed components and a process for producing flat foamed components by providing a foamable material in an injection device and injecting the foamable material through a nozzle into a mold.

Foamed components usually are produced by injecting a foamable material into a mold. Such a foamable material may be for example a polymer melt which comprises a blowing agent or a multicomponent system. If the foamable material is a multicomponent system, the system usually comprises at least two components which form a polymer by reaction and additionally a blowing agent. If the blowing agent is a physical blowing agent, the blowing agent evaporates by the reaction heat. If a chemical blowing agent is used, the blowing agent reacts with one of the components of the polymer, e.g. the isocyanate if the polymer is a polyurethane, thereby forming a gas like carbon dioxide. Due to the volume expansion by forming the gas either by evaporation or by chemical reaction, the foam is produced.

Particularly for forming flat foamed components in a discontinuous process, a predefined amount of the foamable material is injected into the mold. In the mold the blowing agent expands, thereby completely filling the mold with the foam. However, as the foamable material usually reaches only a specific area in the mold during injection, a foamed component may be formed which may have unevenly distributed cells or cells having different sizes. This uneven distribution usually leads to a foamed component with local density differences.

For producing foamed components with a uniform density distribution, it is known for example from EP-A 3278 949 to fill the mold with a reactive mixture, wherein a jet of the reactive mixture is injected into the mold forming a puddle in an intermediate area of the mold, a forward sliding of the puddle of the reactive mixture is caused by means of the jet and after the puddle reached a predefined position, injection of the reactive mixture is continued to fill with over-packing the mold.

WO-A 2013/164274 describes a process in which a foam-forming reaction mixture is introduced into a mold under variable injection pressure. Due to the variable injection pressure, the reaction mixture is injected to different areas in the mold and, thus, a more homogeneous density distribution is obtained.

Another process for injecting the reaction mixture to different areas of a mold is disclosed in EP- A 2 366 525. Here the reaction mixture is injected into the mold with different flow rates and injection speed to pour the reaction mixture into different deposition zones of the mold. JP-A 2006-142125 describes a process for filling a mold for producing a foamed polyurethane article by using a comb nozzle with a large number of holes in a straight pipe. This nozzle, however, is used for applying the reaction mixture onto a belt or a carrier, wherein the comb nozzle or the belt is moved. Therefore, this nozzle cannot be used for producing a foamed component in a closed mold.

It was an object of the present invention to provide a device and a process for forming a foamed component, which allows for a simple injection process without changing the injection parameters during injection and which easily can be applied to conventional injection devices.

This object is achieved by a device for injecting a foamable material into a mold for forming flat foamed components, comprising a tube having a first end with which the tube can be connected to a nozzle of an injection device, and a stream separator for dividing the foamable material into at least two partial streams, the stream separator being placed at a second end of the tube opposite of the first end, such that the at least two streams enter the mold separately.

The process for producing flat foamed components comprises:

(a) providing a foamable material in an injection device;

(b) injecting the foamable material through a nozzle into a mold; wherein the device for injecting the foamable material is connected to the nozzle of the injection device so that the foamable material is divided into at least two partial streams entering the mold.

Surprisingly it has shown that when connecting a tube with a stream separator to the nozzle of the injection device flat foamed components with an essentially even distribution and size of the cells can be produced.

“Flat components” in the sense of the present invention are components having a length of at least 7 times the height of the component and a width in a range between 4 times the height of the component and 0,8 times the length of the component. The length preferably is in a range from 7 to 300 times the height of the component and particularly in range from 30 to 150 times the height of the component and the width preferably is in a range from 4 to 75 times the height of the component and preferably from 5 to 25 times the height of the component.

The width and the length of the component in the sense of the present invention correspond to the length of a line along the longitudinal axis of the tube between two opposite points on which the line intersects the peripheral surface of the component and the longest line perpendicular to and intersecting the longitudinal axis of the tube between two opposite points on which the line perpendicular to the longitudinal axis of the tube intersects the peripheral surface of the component, wherein the longer line corresponds to the length of the component and the shorter line corresponds to the width of the component, and the height is the maximum height.

The flat component produced by the inventive process may have a base of any shape and with constant height or with varying height. Preferably, the flat component has a base with an ax- isymmetric geometry and a constant height and particularly preferably, the flat component produced by the inventive process has a rectangular base and a constant height. Irrespective of the shape of the base, the component may comprise for example grooves, tongues, pitches or steps along at least one lateral face. In this context, if the flat component has a varying height, the “base” corresponds to the intersecting plane spanned by the length and the width of the component or, if the component with varying height has a flat surface perpendicular to the height of the component, the “base” corresponds to this flat surface. If the component has a constant height, the “base” corresponds to one of the surfaces perpendicular to the height of the component and, if the surfaces perpendicular to the height of the component have different sizes to the larger surface. The “lateral faces” of the component having a constant height are the surfaces connecting the surfaces perpendicular to the height of the component.

The flat foamed component may be for example a foamed panel or a composite element. If the flat foamed component is a composite element, it usually comprises a first and a second sheet and a foamed layer between the first and second sheets.

Flat components produced by the inventive process for example are wall or roof elements for walk-in cooling cells, several sorts of doors, sandwich elements for construction, fridge doors, elements for refrigeration trucks (walls, roof, doors).

For producing the flat component, the device for injecting the foamable material preferably is arranged such that the exit of the tube is directed to the geometric center of the component. If the flat component has a rectangular base, the tube preferably enters the mold for producing the component at the center of one of the sides with largest surface. If the flat component has a triangular base, the tube preferably enters at that tip of the triangle, which limits the shortest height of the triangle. If the base of the flat component has four or more edges or an irregular shape, the tube preferably enters the mold at a position on the peripheral surface where the perpendicular to the longest distance between two opposite points on the edge of the base of the component which intersects the geometric center of the component intersects the peripheral surface. Independent of the position the tube enters the mold, it is preferred that the tube is arranged such that the longitudinal axis of the tube intersects the geometric center of the mold.

As the nozzle through which the foamable material leaves the injection device usually has a circular cross sectional area, the tube which is connected to the nozzle also has a circular cross sectional area. For a sufficient cross sectional area at the outlet of the tube, the stream separator preferably has an elliptical base and for separating the foamable material into two streams, the stream separator has a straight edge opposite the base. If the stream separator has an elliptical base, the straight edge preferably lies in the plane which is spanned by the major axis of the elliptical base and a perpendicular to the elliptical base which intersects the major axis.

For separating the foamable material into two streams, the stream separator further is arranged in such a way that the straight edge faces towards the nozzle and the base of the stream separator faces towards the cavity of the mold.

The lateral faces of the stream separator between the base and the straight edge may have plane surfaces. In this case, the stream separator has the shape of an elliptical cylinder obliquely truncated to the base on both sides of the major axis.

However, preferably, the surface is bent and corresponds to the edge of the base at the base and becomes planer in direction to the straight edge.

For separating the foamable material evenly into two streams, it is further preferred that the stream separator has a cross sectional area in the shape of an isosceles triangle. If the stream separator has an elliptical base and the surface of lateral faces is bent, it is preferred if each cross sectional area perpendicular to the major axis of the elliptical base has the shape of an isosceles triangle.

The isosceles triangle having the minor diameter of the elliptical base as base may have any suitable vertex angle. Preferably, the vertex angle is in a range between 10° and 150°, more preferred in a range from 20° to 70° and particularly in a range between 30° and 90°. The appropriate angle depends on the ratio of the length to the width of the foamed component. The smaller the ratio of length to width, the larger the vertex angle.

Depending on the shape of the cavity in the mold and, thus, the shape of the foamed component which is produced by using the device for injecting a foamable material into the mold, it may be necessary to use different stream separators.

Further, to set the direction with which each stream is injected into the mold and further to have openings through which each stream is fed into the mold having a required size, the tube preferably comprises two opposing cutouts at that end where the stream separator is located. Particularly preferably, the cutouts are symmetrical to the straight edge of the stream separator. The geometrical shape of the cutouts may be any suitable shape, for example rectangular, triangular, or in the shape of a semi-ellipse or a semi-circle. Particularly preferably, the cutouts have the shape of a semi-ellipse or a semi-circle.

If it is intended to use the injection device with different molds, it may be necessary to provide different stream separators. For this purpose, the stream separators should be releasably connected to the tube, wherein each type of releasable connection can be used. Such connections for example are screw connections, bayonet coupling, clips, latches, or spring lock. For an easy change of the stream separator, it is preferred to use clips, latches, bayonet coupling or spring locks for connecting the stream separator the tube.

The stream separator and the tube may be made of the same material or of different materials. Suitable materials the tube and the stream separator can be made of may be metals, for example steel, aluminum, brass, or polymers like PE, PP, PU, PA, PC, wherein the tube and the stream separator may be made of different materials. Preferably, the material the stream separator is made of is suitable for 3D-printing, extrusion or injection molding. Particularly preferably, the tube is made of steel or PP and the stream separator is made of PP.

For producing the foamed component, the foamable material is provided in an injection device and injected from the injection device through a nozzle into a mold. For injecting the foamable material, the tube with the device as described above is connected to the nozzle for dividing the foamable material into at least two streams. After filling the mold, the foamable material cures, thereby forming the foam. After curing, the thus formed foamed component is removed from the mold and fresh foamable material can be injected into the mold for producing a foamed component.

The injection device used for injecting the foamable material may be any injection device known to a skilled person. Preferably the injection device using the device for injecting a foamable material into a mold is an injection device for injecting foamable materials comprising at least two components which react to form the polymer and a blowing agent. Such an injection device for example is a mixing head for injecting a multicomponent system into the mold.

Multicomponent systems which can be injected into the mold for forming the foamed component preferably are systems comprising a mixture of two components which react and thus form the polymer and a blowing agent. Suitable multicomponent systems are all systems in which monomers and/or oligomers are mixed and then react to form a polymer and which can contain a blowing agent to form a foam.

Such multicomponent systems for example comprise at least one polyisocyanate (A), at least one isocyanate-reactive compound (B) and at least one chemical and/or physical blowing agent (C). Further, the multicomponent system may comprise at least one catalyst (D), stabilizers, and in some cases flame retardants and/or other additives (E). In this case, suitable polyisocyanates (A) for example are methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI) or hexamethylene diisocyante (HDI) and the isocyanate-reactive compounds (B) for example are polyether polyols.

The polyisocyanates (A) are the aromatic polyfunctional isocyanates known in the prior art. Such polyfunctional isocyanates are known and may be produced by methods known per se. The polyfunctional isocyanates may in particular also be used as mixtures, so that the component (A) in this case comprises different polyfunctional isocyanates. Polyisocyanate (A) is a polyfunctional isocyanate having two (hereinbelow also referred to as diisocyanates) or more than two isocyanate groups per molecule. The isocyanates (A) are in particular selected from the group consisting of aromatic polyisocyanates, such as 2,4- and 2,6-toluene diisocyanate and the corresponding isomer mixtures, 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanate and the corresponding isomer mixtures (also known as monomeric diphenylmethane or MM DI), for example mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates, mixtures of at least one isomer of diphenylmethane diisocyanate and higher-nuclear homologues of diphenylmethane diisocyanate which have at least 3 aromatic nuclei and a functionality of at least 3 and are also known as polyphenyl-polymethylene polyisocyanates or polymeric MDI. The isomers and homologues of MDI are generally obtained by distillation of crude MDL In addition to dinuclear MDI (MM DI) polymeric MDI also comprises one or more polynuclear condensation products of MDI having a functionality of more than 2, in particular 3 or 4 or 5. Polymeric MDI is known and is often described as polyphenyl-polymethylene polyisocyanate. Also employable as isocyanate (A) are mixtures of 4,4'-, 2,4'- and 2,2'-diphenylmethane diisocyanates and polyphenylpolyethylene polyisocyanates (crude MDI) and mixtures of crude MDI and toluene diisocyanates. Particularly suitable are 2,2'-, 2,4'- or 4,4'-diphenylmethane diisocyanate (MDI) and mixtures of two or three of these isomers, 1 ,5-naphthylene diisocyanate (NDI), 2,4- and/or 2,6-toluene diisocyanate (TDI), 3,3'-dimethyldiphenyl diisocyanate, 1 ,2-diphenylethane diisocyanate and/or p-phenylene diisocyanate (PPDI).

The polyisocyanates of the component (A) particularly preferably comprise 2,2'-MDI or 2,4'-MDI or 4,4'-MDI or mixtures of monomeric diphenylmethane diisocyanate or mixtures of monomeric diphenylmethane diisocyanate and higher-nuclear homologues of MDI. The average functionality of a polyisocyanate comprising polymeric MDI may vary in the range from about 2.2 to about 4, preferably from 2.4 to 3.8 and in particular from 2.6 to 3.0. Polyfunctional isocyanates or mixtures of two or more MDI-based polyfunctional isocyanates are known and are commercially available from BASF Polyurethanes GmbH under the trade names Lupranat® M20, Lupranat® M50, Oder Lupranat® M70.

The employed isocyanate-reactive compounds (B) may be selected from any compounds having isocyanate-reactive groups known in polyurethane chemistry, preferably compounds having on average at least 1.5 isocyanate-reactive groups, such as hydroxyl groups, -NH groups, NH2 groups or carboxylic acid groups, preferably NH2 or OH groups and in particular at least 1.5 OH groups. The average functionality of the compounds of the component (B) towards isocyanate groups is in the range from at least 1 .5, preferably 1 .6 to 8.0, particularly preferably 2 to 5.0 and in particular 3 to 4.5.

The compounds having at least two isocyanate-reactive hydrogen atoms (B) comprise at least one polyether polyol.

In a preferred embodiment the polyether polyol has a hydroxyl number of preferably 100 - 1000 KOH/g and is produced by alkoxylation of a starter or starter mixture.

The polyether polyols are produced by known processes, for example by anionic polymerization of one or more alkylene oxides having 2 to 4 carbon atoms with customary catalysts. Preferred alkoxylation catalysts are KOH and aminic alkoxylation catalysts.

Suitable alkylene oxides include for example tetrahydrofuran, 1 ,3- and 1 ,2-propylene oxide, 1 ,2- and 2,3-butylene oxide, styrene oxide, ethylene oxide and preferably 1 ,2-propylene oxide.

The polyether polyol may have a hydroxyl number of 100 - 1000 mg KOH/g, preferably of 200 - 800 mg KOH/g, particularly preferably 250 - 500 mg KOH/g.

Blowing agents (C) used for producing the rigid polyisocyanurate foams preferably include water, formic acid and formic acid-water mixtures. These react with isocyanate groups to form carbon dioxide and carbon monoxide. Since these blowing agents liberate the gas via a chemical reaction with the isocyanate groups they are referred to as chemical blowing agents. Physical blowing agents, such as low-boiling hydrocarbons, can be employed in addition. Suitable physical blowing agents include in particular liquids which are inert toward the polyisocyanates (A) and have boiling points below 100°C, preferably below 50°C, at atmospheric pressure and therefore evaporate under the influence of the exothermic polyaddition reaction.

Employable physical blowing agents include for example alkanes, such as heptane, hexane, n- and isopentane, preferably industrial mixtures of n-pentane and isopentane, n-butane and isobutane and propane, cycloalkanes, such as cyclopentane and/or cyclohexane, ethers, such as furan, dimethyl ether and diethyl ether, ketones, such as acetone and methyl ethyl ketone, alkyl carboxylates, such as methyl formate, dimethyl oxalate and ethyl acetate and halogenated saturated and unsaturated hydrocarbons, such as methylene chloride, dichloromonofluoromethane, difluoromethane, trifluoromethane, difluoroethane, tetrafluoroethane, chlorodifluoroethane, 1 ,1- dichloro-2,2,2-trifluoroethane, 2,2-dichloro-2-fluoroethane and heptafluoropropane and unsaturated hydrocarbons, such as trifluoropropenes and tetrafluoropropenes, such as (HFO-1234), pentafluoropropenes, such as (HFO-1225), chlorotrifluoropropenes, such as (HFO-1233), chlorodifluoropropenes, chlorotetrafluoropropenes and hexafluorobutenes, and also mixtures of one or more of these components. Preference is given to tetrafluoropropenes, pentafluoropropenes, chlorotrifluorpropenes and hexafluorobutenes, wherein the unsaturated, terminal carbon atom bears at least one chloro or fluoro substituent. Examples include 1 ,3,3,3-tetrafluoropropene (HFO-1234ze); 1 ,1 ,3,3-tetrafluoropropene; 1 ,2,3,3, 3-pentafluoropropene (HFO-1225ye); 1 ,1 ,1- trifluoropropene; 1 ,1 , 1 ,3, 3-pentafluoropropene (HFO-1225zc); 1 ,1 , 2, 3, 3-pentafluoropropene (HFO-1225yc); 1-chloro-2,3,3,3-tetrafluorpropene (HFO-1224yd); 1 ,1 , 1 ,2, 3-pentafluoropropene (HFO-1225yez); 1-chloro-3,3,3-trifluoropropene (HCFO-1233zd); 1 ,1 , 1 ,4,4, 4-hexafluorobut-2- ene (HFO-1336mzz). It is also possible to use mixtures of these low-boiling-point liquids with one another and/or with other substituted or unsubstituted hydrocarbons.

Also suitable are organic carboxylic acids, for example formic acid, acetic acid, oxalic acid, ricin- oleic acid and carboxyl-containing compounds. Catalysts (D) used for producing the rigid polyisocyanurate foams according to the invention are in particular compounds which markedly accelerate the reaction of the compounds comprising reactive hydrogen atoms, in particular hydroxyl groups, of the components (B) to (E) with the polyisocyanates (A).

Advantageously employed compounds include for example basic polyurethane catalysts, for example tertiary amines, such as triethylamine, tri butyl amine, dimethylbenzylamine, dicyclohexylmethylamine, dimethylcyclohexylamine, N,N,N',N'-tetramethyldiaminodiethyl ether, bis(dimethyl- aminopropyl)urea, N-methyl- or N-ethylmorpholine, N-cyclohexylmorpholine, N,N,N',N'-tetra- methylethylenediamine, N,N,N,N-tetramethylbutanediamine, N,N,N,N-tetramethylhexane-1 ,6- diamine, pentamethyldiethylenetriamine, bis(2-dimethylaminoethyl) ether, dimethylpiperazine, N-dimethylaminoethylpiperidine, 1 ,2-dimethylimidazole, 1-azabicyclo(2,2,0)octane, 1 ,4-diazabi- cyclo(2,2,2)octane (Dabco) and alkanolamine compounds, such as triethanolamine, triisopropanolamine, N-methyl- and N-ethyldiethanolamine, dimethylaminoethanol, 2-(N,N-dimethylami- noethoxy)ethanol, N,N',N"-tris(dialkylaminoalkyl)hexahydrotriazine, for example N,N',N"-tris(di- methylaminopropyl)-s-hexahydrotriazine and triethylenediamine.

However, further suitable catalysts include metal salts, such as iron(ll) chloride, zinc chloride, lead octoate and tin salts, such as tin dioctoate, tin diethylhexoate and dibutyltin dilaurate and mixtures of tertiary amines and metal salts, in particular organic tin salts. Contemplated catalysts further include: amidines, such as 2,3-dimethyl-3,4,5,6-tetrahydropyrimidine, tetraalkylammonium hydroxides, such as tetramethylammonium hydroxide, alkali metal hydroxides, such as sodium hydroxide and alkali metal alkoxides, such as sodium methoxide and potassium isopropoxide, alkali metal carboxylates, and alkali metall salts of long-chain fatty acids having 8 to 20 carbon atoms and optionally pendant OH-groups.

Contemplated catalysts further include incorporable amines, preferably amines having an -OH, - NH or -NH2 function, for example ethylenediamine, triethanolamine, diethanolamine, ethanolamine and dimethylethanolamine. Incorporable catalysts may be regarded as compounds of the component (B) as well as compounds of the component (D).

It is also possible to carry out the reactions without catalysis. In this case, it is usual to utilize the catalytic activity of amine-started polyols.

Contemplated catalysts for the trimerization reaction of the excess NCO groups with one another further include: isocyanurate-forming catalysts, for example ammonium ion salts or alkali metal salts, especially ammonium carboxylates or alkali metal carboxylates, alone or in combination with tertiary amines. Formation of isocyanurate leads to flame-retardant PIR foams which are preferably used in rigid foam for technical applications, for example in the construction industry as insulation sheet or sandwich elements.

The reaction mixture for producing the polyisocyanate foam according to the invention may optionally also be admixed with further auxiliaries and/or additives (E). These include for example surface-active substances, foam stabilizers, cell regulators, fillers, light stabilizers, dyes, pigments, anti-hydrolysis agents, fungistatic and bacteriostatic substances.

In a preferred embodiment components B to E are mixed to form an isocyanate-reactive component.

For producing the foamed component, usually each component is fed separately into a space of a mixing head and then injected into the mold by driving a piston into the space of the mixing head, by which the mixture formed in the space is injected into the mold through the nozzle of the mixing head.

Embodiments of the invention are shown in the figures and explained in more detail in the following description.

In the figures:

Figure 1 shows schematically a process for producing foamed components;

Figure 2 shows an inventive device for injecting a foamable material in top view;

Figure 3 shows a cross-sectional view of an inventive device for injecting a foamable material;

Figure 4 shows a side view of an inventive device for injecting a foamable material;

Figure 5a shows a tube of the inventive device for injecting a foamable material;

Figure 5b shows the tube of figure 5a in a position rotated by 90°;

Figure 6a shows a stream separator of the inventive device for injecting a foamable material;

Figure 6b shows the stream separator of figure 6a in a position rotated by 90°;

Figure 7 shows the distribution of the foamable material in a mold.

Figure 1 shows schematically a process for producing foamed components.

For producing the foamed components from a multicomponent system, particularly a two-com- ponent system, a first component is provided in a first container 1 and a second component is provided in a second container 3. The first container 1 is connected to a mixing head 5 by means of a first connecting line 7 and the second container 3 is connected to the mixing head 5 by a second connecting line 9. The first connecting line 7 comprises a first dosing unit 11 for dosing the first component into the mixing head 5 and the second connecting line 9 comprises a second dosing unit 13 for dosing the second component into the mixing head 5. In the mixing head 5, the first component and the second component are mixed and for producing a foam, also a blowing agent 15 is added to the mixing head 5.

In the mixing head 5, the components are mixed and then injected through a nozzle 21 into a mold 27. In the mold 27, the mixture containing the first and the second components cures and forms a polymer. Due to the blowing agent, the polymer forms a foam.

For a uniform distribution of the cells in the foam a device for injecting the foamable material is used which comprises a tube and a stream separator. Such a device is shown in figure 2 in top view, in figure 3 in a cross-sectional view and in figure 4 in a side view.

A device 29 for injecting the foamable material comprises a tube 31 and a stream separator 33. The tube 31 has a circular cross sectional area and is connected with a first end 35 to the nozzle 21 of the mixing head 5. At a second end 37 opposite the first end, the stream separator 33 is connected to the tube 31 .

As can be seen in the top view of figure 2, the stream separator 33 has an elliptical base 39. By using the elliptical base, the foamable material is not redirected by 90° but by a smaller angle and, thus, has a flow direction oblique to the longitudinal axis 41 of the tube.

For dividing the foamable material into two partial streams, the stream separator 33 has a straight edge 43. The stream separator 33 is placed in the tube 31 in such a way that the straight edge 43 faces the nozzle 21 of the mixing head 5. Accordingly, the base 39 of the stream separator 33 points in the direction of the mold 27.

For avoiding a reduction in the cross sectional area through which the foamable material flows, cutouts 45 are provided in the tube 31 . The cutouts 45 preferably have a semi-circular or semielliptical shape and are placed such that the line connecting the uppermost points 47 of the cutouts 45 runs perpendicular to the straight edge 43 of the stream separator 33.

Besides the geometry shown here, it is also possible that the tube may have any other cross sectional shape, for example an elliptical shape, a rectangular shape, a square shape or any other shape. However, as the nozzle of an injection device like a mixing head usually has a circular shape, it is preferred to use a tube with a circular shape. Also the base of the stream separator 33 may have any suitable shape, besides the shown elliptical shape for example a circular shape, a rectangular shape or a square shape. The shape of the base of the stream separator 33 thereby depends on the cross sectional shape of the tube 31 . If the tube has a circular cross sectional shape, it is preferred to use a stream separator 33 with an elliptical base. If a tube with an elliptical cross sectional shape is used, the stream separator 33 also may have an elliptical base or alternatively a circular base. If a tube with a square cross sectional shape is used, it is preferred to use a stream separator with a rectangular shape and if a tube is used with a rectangular shape, the base of the stream separator may have a rectangular or square shape. In this context, rectangular means each rectangular shape except a square shape.

Further, the cutouts 45 also may have any other shape, for example a triangular, a rectangular or a square shape. However to avoid foamable material to deposit at the corners of such shapes, it is preferred that the cutouts 45 have a semi-circular shape, a semi-elliptical shape or the shape of a circular segment.

The surfaces 48 of the stream separator 33 may be plane or bent. Independently of whether the surfaces 48 are plane or bent, it is preferred that the cross sectional shape of the stream separator 33 at the minor diameter of the elliptical base has the shape of an isosceles triangle. Preferably, the surfaces 48 of the stream separator 33 are bent in such a way, that each cross sectional shape of the stream separator 33 perpendicular to the major diameter of the elliptical base has the shape of an isosceles triangle.

The isosceles triangle having the minor diameter of the elliptical base as base may have any suitable vertex angle. Preferably, the vertex angle is in a range between 10° and 80°, more preferred in a range from 20° to 70° and particularly in a range between 30° and 60°.

The tube 31 of the inventive device for injecting a foamable material into a mold is shown in more detail in figures 5a and 5b.

Particularly for easily change the stream separator 33, it is preferred to connect the stream separator 33 releasably to the tube 31 . Such a releasable connection is for example a screw connection, a bayonet coupling or a coupling with latches, clips or spring-lock. In the embodiment shown here in figures 5a to 6b, the stream separator 33 is connected to the tube by means of clips. For coupling the stream separator 33 to the tube 31 , the tube 31 comprises recesses 49 into which the clips of the stream separator 33 engage. To avoid that foamable material leaves the tube at the position of the recesses 49, it is important that the recesses do not form openings in the wall of the tube.

A stream separator 30 which can be attached to the tube 31 shown in figures 5a and 5b is shown in figures 6a and 6b.

For attaching the stream separator to the tube, the stream separator 33 comprises a first clip 51 and a second clip 53. Each clip 51 , 53 comprises a flat spring which ends in a thickening 55, which has such a size that it fits into the recess 49 of the tube 31 .

Depending on the shape of the mold and the foamed component to be produced, due to this design, the stream separator 33 can be easily changed.

The distribution of the foamable material in the mold is shown in figure 7. Due to the stream separator, the foamable material is not injected parallel to the axis of the tube but divided into two partial streams. Each stream forms a puddle 57 in the mold 27, the puddles growing during injection of the foamable material.

After the foamable material is injected into the mold, the components in the foamable material start to react, thereby forming the polymer. Due to the blowing agent, the complete mold is filled with the foam. Experiments using the inventive device for injecting a foamable material into a cuboid mold have shown that by using the stream separator 33 a much more homogeneous distribution of the cells and density distribution of the foam can be achieved than when using the tube without stream separator.

When injecting the foamable material without the device for injecting the foamable material, the density of the foam in the center of the foamed component is remarkably higher than at the edges. However, if the device for injecting the foamable material is used, a homogeneous density distribution can be achieved.

List of reference numbers

I first container

3 second container

5 mixing head

7 first connecting line

9 second connecting line

I I first dosing unit

13 second dosing unit

15 blowing agent

21 nozzle

27 mold

29 device for injecting a foamable material

31 tube

33 stream separator

35 first end of tube 31

37 second end of tube 31

39 base of stream separator 33

41 longitudinal axis of tube 31

43 straight edge of stream separator 33

45 cutout

47 uppermost point

48 surface of stream separator 33

49 recess

51 first clip

53 second clip

55 thickening

57 puddle

Claims

1 . A device for injecting a foamable material into a mold (27) for forming flat foamed components, comprising a tube (31) having a first end (35) with which the tube can be connected to a nozzle (21 ) of an injection device, and a stream separator (33) for dividing the foamable material into at least two partial streams, the stream separator (33) being placed at a second end (37) of the tube (31 ) opposite of the first end (35) , such that the at least two streams enter the mold (27) separately.

2. The device according to claim 1 , wherein the stream separator (33) has an elliptical base (39) and a straight edge (43) opposite the base (39).

3. The device according to claim 1 or 2, wherein the stream separator (33) has a cross sectional area in the shape of an isosceles triangle.

4. The device according to any of claimsl to 3, wherein the stream separator (33) has the shape of an elliptical cylinder obliquely truncated to the base on both sides of the major axis.

5. The device according to any of claims 1 to 4, wherein the tube (31) comprises two opposing cutouts (45) at the end where the stream separator (33) is located.

6. The device according to claim 5, wherein the cutouts (45) are symmetrical to the straight edge (43) of the stream separator (33).

7. The device according to any of claims 1 to 6, wherein the stream separator (33) is releas- ably connected to the tube (31 ).

8. The device according to claim 7, wherein the stream separator (33) is connected to the tube by clips, latches, bayonet coupling, or spring lock.

9. The device according to any of claims 1 to 8, wherein the injection device is a mixing head (5) for injecting a multicomponent system into the mold (27).

10. A process for producing flat foamed components, the process comprising:

(a) providing a foamable material in an injection device;

(b) injecting the foamable material through a nozzle (21) into a mold (27); wherein a device for injecting the foamable material according to any of claims 1 to 9 is connected to the nozzle (21) of the injection device so that the foamable material is divided into at least two partial streams entering the mold.

11. The process according to claim 10, wherein the foamable material is a multicomponent system.

12. The process according to claim 11 , wherein the multicomponent system comprises at least one polyisocyanate, at least one isocyanate-reactive compound and at least one chemical and/or physical blowing agent.

13. The process according to any of claims 10 to 12, wherein the flat foamed component is a rectangular foamed plate.

14. The process according to any of claims 10 to 13, wherein the flat foamed component is a composite element comprising a first and a second sheet and a foamed layer between the first and second sheets.