Method for producing extruded foamed bodies

BACKGROUND OF THE INVENTION The present invention relates to a passage, in the form of molar pieces or board, of 14.4 to 56.1 kg / m³ (0.9-3.5 lb / ft³) The invention relates primarily to thermoplastic extruded foams which have been foamed in vacuo. Extruded plastic foams can be used very advantageously in many fields, e.g. insulation, packaging, decoration, etc. One of the most important applications of polystyrene * bök is to provide heat island nutrition ·

The surface quality of extruded plastic foams is an important parameter from both a commercial and aesthetic point of view. Users require ogysnlstss bobs.

The quality of the surface of the foams is influenced by the amount of beads and bands, the appearance of the foam, and the roughness. Beads are foam defects that appear on the foam surface as a white area or bump. Bands on the surface of the foam are defects that appear in the form of a whitish white crust on the surface of the foam. A foamy appearance is a surface that is grainy and not uniform in appearance. · The concept of foamy appearance is also used to describe the difference between a foamed body and the surface of a tea. These defects can be extremely detrimental to the properties of the foamed * 3 ** products, particularly those relating to thermal insulation, compressive strength, and water resistance.

--------- The quality of the surface can be influenced by controlling the arrows on the extruder tool or controlling the pressure exerted on the extruded foam teas. It would be desirable to have a method that is capable of controlling the surface. In addition, it would be even easier for a blonde to simply control the surface.

Today, governments and environmentalists are calling for significant efforts to reduce or even eliminate the use of fluorocarbons (CFCs) used as aerosol propellants, refrigerants, foaming agents, and in electronics and aerospace.

The general procedure for making foamed bodies generally includes the following steps! The polymer is e.g. polystyrene is heat-plaqueized, one or more liquid foaming agents are added and, under conditions which allow the incorporation of the volatile foam removal agent, and at the same time to prevent foaming of the mixture, are thoroughly mixed into the plasticized polymer. A thoroughly blended mixture of the polyerol and the foam remover (or agents), which may also contain nucleating agents, flame retardants, plasticizers, etc., is cooled by reducing the pressure of the mixture so that foam is formed from the mixture, thus can produce. The foamed bodies having the property of extraction can be produced by extrusion of the cooled plasticized polymer-foam blend mixture under reduced pressure. In certain extrusion processes, the foamable mixture is extruded into a vacuum chamber where expansion of the foam occurs at a pressure below atmospheric. Examples of vacuum foam extraction apparatuses and methods are disclosed in U.S. Pat. Nos. 3,504,1008, 3,169,272 and 3,822,331. U.S. Patents. One problem with the use of vacuum extrusion techniques is related to the removal of material from the vacuum chamber, particularly when the material is delicate or fragile, e.g. polystyrene foam in the form of large panels or lumps. 3,704,083 and 4,044,004 provide the solution to this problem. U.S. Pat. Further modifications and repairs of the extrusion apparatus include the apparatus disclosed in U.S. Patent No. 4,109,310. U.S. Pat.

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The present invention is 14.4-56.1 kg / m³ (0.9-3.5 lb / ft³) is a process for the production of an endless foamed body with as few surface pegs, beads, bands, foam-like appearance and ridges as possible. The procedure consists of the following steps:

(A) plasticizing a mixture of at least one thermoplastic polymer and at least one nucleating agent;

(B) adding to the molten polymer at least one hebosolester from: 1,1-dichloro-2,2,2-trifluoroethane, 1-chloro-1,1-dlfluoroethane, 1,1,1,2 -tetrafluoroethane, 1,1-dichloro-1-fluoroethane, 1-chloro-1,1,1,2-tetrafluoroethane, or a mixture of two or more of the above compounds;

(C) mixing the foaming agent and the mixture obtained in step (A) at a pressure that prevents the foam material and a foamable polymer mixture;

(0) extruding the resulting foamable mixture into a space where the mixture expands to foamed bodies through a suitably formed oxtrusion die maintained at 10-76.7 ° C (50-170 ° F);

(6), the resulting foamed bodies are cooled.

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A, • ♦ · ··· • · · · · · · «

In one embodiment of the present invention, a pressurized space of less than atmospheric pressure is produced in an elongated chamber, the foamable plastic mixture penetrates through an extrusion die at one end and the foamed body exits through a water bath. The foamed bodies produced by the process of the present invention are characterized in that they have the desired bulk density and have an average cell size of a cell having a relatively small cell size of about 10 cm. They are 0.5 m or less, have high compressive strength, and have a higher number of inches per unit volume compared to other products.

For a better understanding of the invention, the following is an illustration of the solution.

Figure 1 is a schematic side view of an apparatus useful for carrying out the method of the present invention; sectional view;

Figure 2 is an enlarged top plan view of a fan-shaped nozzle system and forming mechanism on the inlet side of the chamber;

Fig. 3 is a schematic schematic representation of one of the piston cylinders used to float the forming rollers or other overhead conveyors; and Fig. 4 is a joint sometime representation of a temperature control of an extruder die outlet.

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- 7 The parts and percentages in the patent and the claims represent weight ratios,

The following thermoplastic materials may be foamed and extruded by the process of the present invention, e.g. poly (vinylidene chloride) formed by copolymerization of substituted aromatic vinyl polymers (homo- or copolymers), pollen (phenylone ether), polyvinyl chloride, vinylidene chloride (60 parts) and acrylonitrile (20 parts)_t poliolefinekfpl. polyethylene and ethylene_} and copolymers of vinyl acetic or ethyl acrylate, etb. Mixtures of such tipue resins can be foamed according to the method of the present invention. For example, a mixture of polystyrene and a poly (phenylene resin) can be used to form foamed bodies according to the invention. In the process of the invention, the thermoplastic resins are preferably processed with alkenyl substituted aryl polymers.

The aromatic polyolefins which are extruded and expanded by the process of the present invention comprise at least 50% by weight of an alkenyl substituted aroma compound of the formula (X):

The term "aromatic hydrocyanic group" or "aromatic halogen containing benzene homologues" means hydrocyanoeoporphic,

R is hydrogen or methyl.

- 8 The polymer remaining monomer contains at least one ethylenically unsaturated monomer capable of copolymerising with the aromatic compound.

The alkenyl-substituted aromatic compound represented by the general formula (X) may in certain processes be a compound of the general formula (II) wherein

R¹, R³, R⁴, R⁵ and R⁶ independently hydrogen, chloro or bromo, or C 1 -C 4 alkyl, 2, and R or hydrogen, the substituents have the meanings provided that the total number of carbon atoms in the monomer does not exceed 12.

Alkenyl-substituted aromatic monomers include styrene, o-methylstyrene, o -methyl-azirol, m-methyl-styrene, p-methyl-styrene, o-k-chloro-azirol, p »chloro *, styrene, 2, 6-dichloro-styrene, o-bromo-styrene, etc. Examples of the ethylenically unsaturated monomer which can be copolymerized with the styrene derivatives listed above include methylstacrylate, acrylic nitrile, malic anhydride, methyl maleic anhydride, methylene boronic anhydride, and the like.

Amongst the aromatic polymers substituted with an alkenyl group, the styrene-type polymers are preferred. Polystyrenes can be copolymers of homopolymers of styrene or their copolymers and one or more unsaturated monomers of the copolymerizable ethylene type. These are the types of polymers that can be used for this purpose • »· ·········»

Υ »*« ··· '·!

- 9 styrene copolymers are commercially available from a variety of sources, in several grades with different molecular weights. The molecular weights of the polymers can be determined by a variety of methods known to those skilled in the art, such as viscosity determination, refraction and ultracentrifugal sedimentation. The flow rate of the polymer melt through an orifice of a given cross-section, also referred to as a melt flow index (MFI), can also provide information about molecular weight conditions. The MFI method is a relatively low-cost, easy-to-implement technique * Details of the method can be found in many publications, e.g. PO Flory Princes of Polymer Chemistry was published in Elmen (Cornell University Press, Ithaca, New York, 1953). Polymers having a molecular weight of from 100,000 to 500,000 are generally useful, preferably from 150000 to 450000, and more preferably from 250000 to 350000.

Useful styrene polymers (hereinafter referred to as polystyrenes) are commercially available and the polystyrenes thus obtained differ in several properties, e.g. melt flow indexes are different. Polystyrenes are available, for example, from ARCO Chemlcal Cempany * under the generic trademark D * UEN6, such as OYLEN a, and from Polyear Ltd, (similar to Ontario).

« • 4 ·« * · · ·· · «

The properties of the extruded foamed products obtained by the process of the invention can be controlled and modified by selecting the molecular weight of the polymer used in the manufacture. For example, the production of lower density polystyrene foams can be simplified using high molecular weight polymers, and the production of higher density foamed bodies can be simplified using polymers of lower molecular weight or higher viscosity.

Special styrene copolymers can be prepared, for example, from the following blends x 70% sitit and 30% acrylonitrile 80% sitit and 20% vinyl toluene; 75% sitit and 25% methyl methacrylate; etc

The volatile and liquid foaming thousands used in the process of the present invention include at least one of the compounds listed below x 1-chloro-1,1-difluoroethane (HCFC-142b), 1,1,1,2-tetra-fluoro- ethane (HFC-1334a), 1-chloro-1,2,2,2-tetrafluoroethane (R-141), 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124); or a mixture of two or more of the compounds listed herein. Preferred foaming agents are 1-chloro-1,1-difluoroethane and 1-chloro-1,2,2,2-tetrafluoroethane and a mixture of the two. 3 to 16 parts or more of the blowing agent per 100 parts of polymer are added to the plasticized aromatic polymer, which is substituted by heating. Modifying the amount of blowing agent blended into the polymer, blowing stone • ·

In addition to the dependence on the quality of the components that make up the crayfish, it offers the ability to produce extruded foam teas with different characteristics.

In addition to the above-described blowing agents, a second blowing agent may be used in step (B) of the process. Examples of such optional foaming agents include dichlorodifluoromethane (R-12), chlorodifluoromethane (R-22), carbon dloxld, pentane, hexane, methyl chloride, ethyl chloride, or a mixture of two or more of the compounds listed herein. The above group also includes all isomers of the listed compounds. For example, butane in the list may include isobutene, n-butane, and the like. The blowing agent may be used in any proportion in the blend provided that the surface properties of the foam remain satisfactory. In a preferred embodiment of the process according to the invention, the second foaming sponge is present in less than 50% by weight of the blowing agent mixture. Examples of blowing agent combinations include: R-142b / R-22, with ratios ranging from 80:20 to 50:50; R-142b / R-12, with a ratio of 60:40 to 20:80; R-124 / ethylene chloride, ratios from 50:50 to 80:20; R-134a / R-123, with a ratio of 80:20 to 50:50; R-134a or R-142b or R-22 / carbon dioxide in ratios from 99: 1 to 95-5 and R-134a or R-142b or R124 or R-22 / psnane in a ratio of 75:25 to 25 : Up to 75.

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In the process, the foaming agent for the ion may be added to the alkenyl substituted aromatic starting material by any of the methods. In one embodiment, the blowing agent, or blend of blowing agent thousands, is directly applied to a device for aiding and mixing the material, e.g. injection into an extruder. When more than one blowing agent is used, it is possible to inject them separately into the molten material. In a preferred embodiment of the process of the present invention, the tandem extruders 10 shown in Figure 1 are used in such a way that the first extruder performs the introduction and mixing of the foaming agent while the mammalian extruder controls the mixing and cooling of the material. The foamable polymer blend may contain, in addition to the molten polymer blowing agent (s), and will generally contain other additives, which will modify certain properties and / or properties. Nuclear cells can reduce the primary cell size. Materials that can be used as nucleating agents include talc, calcium silicate, calcium carbonate, indigo and others. The nucleating agent is added in an amount of 0.05-5.0 parts per 100 parts of the polymer to the foamable polymer. It is customary to add plasticizers to the mixture to be foamed, such as liquid paraffin, hydrogenated coconut oil, etc. Other useful additives are flame retardants and ethanol stabilizers.

From the extruder, the aluminized polymer foam blowing agent blend enters a zone where the blend expands. Although this zone may be atmospheric pressure, in the preferred embodiment of the process according to the invention, the zone is under reduced pressure, i.e. the pressure is less than atmospheric. This can be accomplished by the expansion zone comprising a vacuum chamber in which the pressure is controlled to the desired level and the expandable polymer blend expands from the chamber to foamed bodies. The pressure inside the vacuum canister can be varied so that foamed bodies of different properties (cell size, cell volume and density) can be obtained according to the desired characteristics. The vacuum chamber pressure is less than 91.4 kPa (27 Hg m), generally in the range of 6.77 to 91.4 kPa. In some embodiments, the pressure is maintained between 6.77 kPa and 67 kPa. Generally, by increasing the vacuum (at lower pressure), the foaming of the mixture increases, resulting in lower foam densities.

In a preferred embodiment of the process of the invention, shown in Figure 1, the outlet end 12 of the secondary extruder described above is adapted to fit and seal the upper end 13 of the bent tunnel 14 (which encloses the vacuum chamber 15). , the lower end 16 of the tunnel is submerged in the water tank 17 which seals the other end of the vacuum chamber. The water bath allows the finished product to be removed from the chamber while maintaining the vacuum. The extruded polystyrene foam produced in the vacuum chamber advances through the chamber, · ···

- 14 and then the atmospheric pressure from the vacuum chamber on the other side of the water seal through the layer. In addition to maintaining the vacuum in the chamber, the water bath also provides cooling of the affected body inside the chamber.

In operation, the extruded extruded foam 20 generally exits a die 20, shown in more detail in Figure 2, and the blend expansion and foam formation are controlled by curved cylinders 22 located below and above the outlet plane. The foam 24 exiting the spout, the lower and upper rollers shown in the figure, which comprise the driven disk row 25 on bent shafts, is shaped in thickness and extended to a final width. As shown in the figure, 5 such driven rows of disks are disposed below and above the fan spout 20. Further thickness and evenness control can be achieved by passing the foam panel between the even, lower and upper conveyor belts 27. The density of the foam is partly determined by the vacuum in the chamber. Once exposed to the thickness, width and smoothness of the extruded foam, the water bath is passed through a conveyor belt 30 equipped with a gear, while the foam cools through and passes through the film layer and becomes more solid. Any suitable device, such as a waterproofing device, may be used to transfer the foam to the watertight. conveyor shown in the figure. In a preferred embodiment of the process of the invention, ··· · · • 9

- 15 the foamed bodies are carried through the water by an upper conveyor belt, the foam adheres to the belt through the weight of the species. In the preferred embodiment shown in the figure, the extrusion die 20 is fan-shaped and has an arcuate orifice 32, and the mixture ejected from this fan-shaped die is further molded by the floating forming rollers shown. As shown in Figures 2 and 3. As illustrated in FIG. 6B, for better control of the rollers 22 and the conveyor belt 27, they can be hinged by the piston roller assemblies. The piston rod 36 of such piston rollers is connected to a guide shaft 37 which holds the corresponding roller or conveyor belt. For each of these, it is possible to have such a piston audio assembly.

Compressed air is supplied from the air source 41 via the pressure regulator 42 and the check valve 43 via the conduit 40 to the lower part of the cylinders. In this way, by controlling the pressure of the air introduced into the cylinder, it is possible to float the curved cylinder 22 against the weight of the pneumatic mechanism. Once floating, air is fed to one side of the piston cylinder from the feed 46 through the conduit 45, the regulator 47 and the control valve 48 so that the effect of the cylinders on the foamed bodies can be precisely controlled. The radii of the curved cylinders 22 are different and therefore their tare weights also differ. As soon as the hsnner is in a floating state, only a slight pressure difference is applied, so that the force exerted by the cylinder is gentle.

In general, the method of the present invention controls the temperature of the extrusion die outlet. The extrusion die outlet temperature is in the range of 10-76.7 ° C (50-170 ° F), preferably in the range 21.1-76.7 ° C (70-170 ° F).

As shown in FIG. 4, the fan-shaped extrusion die 20, e.g. can be like the one shown in U.S. Patent No. 4,364,722. U.S. Pat. No. 4,123,125, which has an oil circulation system near the 50 orifices of the extrusion die 32 arc. The outlet is provided with openings 51 and 52 for oil inlet and outlet, so that the temperature of the outlet can be controlled by controlling the temperature of the circulating oil. As shown by the arrows, the oil enters at the 51 stubs and exits at the 52 stubs. The circulation of the oil is provided by the pump 53, which is bound to the beer by the oil cooler 54 and the oil heater 55. The temperature of the oil leaving the tool is sensed by the temperature controller 56 and compared with the set value, and then, if necessary, regulates the amount of water from the source 58 to the oil cooler 54 via the control valve 57. In this way, the temperature of the outlet can be controlled and maintained within this desired range, the heat from the hot metal portion of the outlet being removed by the oil. A temperature indicator and a pressure indicator 61 on the pressure side of the pump are placed in front of the oil cooler. The oil heater is controlled by the temperature switch 62 via the power ramp 63, but this is used during the heating up phase. The oil required for the system is obtained from the gut 64 through the valve 65 and the oil flow is indicated by the flow meter 66.

Concerning the details of the vacuum chamber, the mold mechanism and the fan-shaped extrusion die, 4,199,310; 4,234,529; ah 4,364,722 this. Reference is made to U.S. Patents.

Alkenyl-ceoport substituted polyaromatic foamed bodies produced by the process of the present invention have the following properties: density: ca. 14.4-56.1 kg / m³ (0.9-3.5 lb / ft³), preferably

14.4-32 kg / m³ (0.9-2 lb / ft³) or 14.4-25.2 kg / m³(0.9-1.6 lb / ft³);

Average cell size: less than 0.5 mm, preferably less than 0.3 mm;

cell numerical low density at low 6100 / cm, particularly low at 9150 / cm³;

20.8-25.2 kg / m³ 12200 / cm³; 32 kg / no /³ above a density of 18300 / cm³.

The following examples illustrate the process of the invention and the foamed bodies produced by the process of the invention. The general process and equipment used in the examples, unless otherwise stated, are the following: Initially, a plasticized blend of polystyrene polymer, water-polished polystyrene polymer, talcum and flame retardant is prepared by blowing the foam a mixture is obtained. A nucleating agent and a flame retardant are added to the foamable polymer blend. The foamable mixture is extruded through an outlet of the extruder to one end of an elongated cassette under vacuum, where the foamable mixture is expanded under controlled conditions to form a continuous panel of 122 cm (48 in) wide, the thickness of the board can be varied as desired.

1-6. In the examples, the fan-shaped extruder millimeter has an arc length of 41.8 cm (16.468 in) and a radius of 24.13 cm (9.5 in) and an angle of 120 °. As the foamable mixture is extruded into the vacuum chamber, the expansion of the foamable mixture is controlled by curved cylinders positioned below and above the outlet plane and within the desired range of 3.81-5.08 cm (1.5-2.0 in). a 122 cm wide infinite board is produced. Other board thicknesses can be obtained by controlling the extrusion tool opening and the position of the curved cylinders * The infinite foam board passes through the vacuum chamber and then in a water bath »·« • · ·

- 19 passes cools down and becomes more fragile. After passing through the water bath, the endless foam boards are pulled over, aligned as needed, and cut into the opposite sides of the chamber.

In accordance with the process of the present invention, foam boards leaving the vacuum chamber are tested in known manner for density, cell size, cell number, compressive strength, factor K and other assay considerations. The average cell size is the average of the cell dimensions defined in the X, Y, and Z directions. The X direction is the direction of the extrusion process, Y is perpendicular to the technological advancement direction, and Z is the thickness. The compressive strength of the foam bodies produced by the process of the present invention is determined in accordance with ASTM Test C165-83. * Investigation of the compressive strength properties of thermal insulators ** c. standard assay method.

Further details of the process and the apparatus implementing it are given in the description of the examples.

100 Partial crude shear polymer / ARCO Dylene 09 Melt Flow Index (MFI) 0.5 /, 19.4 parts shredded polystyrene, 0.45 part talc, and 0.95 part flame retardant plastic. We introduce 11.9 parts of the foam blender into the plastic first,

<img file="HUT58595A_D0001.tif" />

* 20 having an Injection R-142b: R-22 (60:40) to give a foamable polymer blend. The foaming agent was injected at 28269 kPa (4100 psi). The melt temperature was 481.6 ° C (485 ° F). The vacuum value in each example was 51.6 kPa (17 Hg in.). Further details of the process and some fractions of foamed bodies are provided by

First is shown in Table II.

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<img file="HUT58595A_D0002.tif" />

(in) 1,477 - 1,408 1,427 1,450

<td>u s</td><td>§ 3 w *</td><td>3 w</td>

<td></td><td> 8 -</td><td>She</td>

<td>X</td><td></td><td></td>

<td> «3</td><td></td><td></td>

<td>u</td><td></td><td></td>

<td>SS</td><td>S o&gt;</td><td>ü</td>

<td>you</td><td> 8 ”*</td><td>She</td>

<td></td><td>S 8</td><td> 3</td>

<td>Ό</td><td> * *</td><td> *</td>

<td>rí</td><td> 8 ”</td><td>She</td>

<td></td><td> 3 8</td><td></td>

<td>•SHE</td><td> &lt;· ·</td><td> &lt;*</td>

<td>T&gt;</td><td> ** «·</td><td>Q</td>

<td></td><td></td><td></td>

<td>"Ο</td><td></td><td></td>

<td> *9</td><td> 1 1</td><td> 1</td>

<td>• o r4</td><td> 3 3</td><td></td>

<td></td><td> • «</td><td>«t</td>

<td>&gt; • H</td><td></td><td>Q</td>

<td></td><td></td><td></td>

• · * · * «

- 22 As shown in the table; the surface quality of the foam bodies produced ranges from froth-like appearance to excellent as the extrusion die outlet temperature is reduced from 92.2 ° C to 32.2 ° C (Examples 1-6). The temperature of the melt leaving the extruder does not change significantly because the extrusion pressure increases as the extrusion die outlet temperature decreases. The appearance of the surface is shown in Figure 5. In example, it is rated slightly mild, and is already of satisfactory quality for certain types of applications, but in grades 2-4. Highly qualified products from Examples 1 to 4 are preferred. In certain applications, e.g. graphic arts, providing a highly qualified interface is desirable.

ZJUMUéK

100 A crude styrene polymer / ARCO Dylene 08 - Melt Flow Index (MFI) of 5.0, 15.11 parts of shredded polystyrene is prepared from 0.55 parts of talc and 0.85 parts of flame retardant in a plastic mixture. 11.5 parts of a blowing agent mixture of R-142biR-22 (20t80) are added to the plastic mixture to form a foamable polymer blend. The blowing agent was injected at 31717 kPa (4600 psi). The melt temperature was 231.1 ° C (448 ° F). The vacuum in each example was 44 kPa (13 Mg in.). Further details of the process and some properties of the foamed bodies are shown in Table 2.

<img file="HUT58595A_D0003.tif" />

Features of polystyrene foam boards

<td>Example</td><td> 7</td><td> 8</td><td> 9</td>

<td>extruder silver outlet</td><td></td><td></td><td></td>

<td>temperature of ° C</td><td> 65,6</td><td> 76,7</td><td> 87,8</td>

<td>° F</td><td> 150</td><td> 170</td><td> 190</td>

<td>extrusion pressure (kPa)</td><td> 4496</td><td> 4109</td><td> 3903</td>

<td>(PSXG)</td><td> 652</td><td> 596</td><td> 566</td>

<td>extruded melt temperature</td><td></td><td></td><td></td>

<td>(° C)</td><td> 130</td><td> 129,4</td><td> 129,4</td>

<td> (^eF)</td><td> 266</td><td> 265</td><td> 265</td>

<td>Product features</td><td></td><td></td><td></td>

<td colspan="2">the quality of the surface is very good</td><td>I'm very frothy</td><td>I'm very frothy</td>

<td>beer burn (kg / a³)</td><td> 23,39</td><td> 25,47</td><td> 25,15</td>

<td>(Lb / ft³)</td><td> 1,46</td><td> 1,59</td><td> 1,57</td>

<td>average cell size (mm)</td><td> 0,35</td><td> 0,30</td><td> 0,31</td>

<td>cellulose (1 / cm³)</td><td> 11763</td><td> 18219</td><td> 17206</td>

<td>(1 / ln^s)</td><td> 192763</td><td> 298554</td><td> 281955</td>

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- 24 As shown in Table 2, the surface quality of the stopped foamed teas varies from very frothy to very good, when the oil temperature is 7.8 ° C to 65.8 ° C (190- 150 ° F) (Examples 7-9). The temperature of the melt leaving the extruder does not change significantly, as the extrusion die pressures increase as the die die temperature decreases. 8 and

9th The quality of the products obtained in Examples 1 to 4 is unacceptable, their surface is highly foamed, while the product of Example 7 is very advantageous. In certain applications, e.g. graphical application ^ highly qualified surface properties are desirable. If R-12 accounts for the greater part of the foam-thinner composition used, the temperature of the oil at the outlet of the extrusion tool may be varied within a narrow range. As can be seen from the above description and the examples, the process for producing the foamed or tablet shaped foamed bodies of the present invention, when the foamable mixture is extruded into a pressurized atmosphere, is of satisfactory quality and in some cases improved by temperature control Surface characteristics allow the production of products. The process provides an economical solution with relatively little work to control the surface properties of the foamed bodies.

&lt;·» 25 *·

Although the process has been described in relation to reeds, it will be appreciated by those skilled in the art that many modifications will be possible. Thus, the invention encompasses all modifications that fall within the scope of the claims.