PatentDe  


Dokumentenidentifikation EP0873230 07.04.2005
EP-Veröffentlichungsnummer 0000873230
Titel SEMI-KONTINUIERLICHES VERFAHREN ZUR HERSTELLUNG VON POLYMEREN SCHAUMSTOFFEN IM FESTEN ZUSTAND
Anmelder University of Washington, Seattle, Wash., US
Erfinder SCHIRMER, G., Henry, Spartanburg, US;
HOLL, Roland, Mark, Seattle, US;
KUMAR, Vipin, Seattle, US
Vertreter derzeit kein Vertreter bestellt
DE-Aktenzeichen 69534047
Vertragsstaaten AT, BE, CH, DE, DK, ES, FR, GB, GR, IE, IT, LI, LU, MC, NL, PT, SE
Sprache des Dokument EN
EP-Anmeldetag 12.12.1995
EP-Aktenzeichen 959447129
WO-Anmeldetag 12.12.1995
PCT-Aktenzeichen PCT/US95/16370
WO-Veröffentlichungsnummer 0096018486
WO-Veröffentlichungsdatum 20.06.1996
EP-Offenlegungsdatum 28.10.1998
EP date of grant 02.03.2005
Veröffentlichungstag im Patentblatt 07.04.2005
IPC-Hauptklasse B29C 44/34

Beschreibung[en]
Technical Field of the Invention

This invention relates generally to methods, apparatus and products for the production of articles of foamed polymers and more particularly to methods for the semi-continuous production of such materials. The foamed polymers may be microcellular with average bubble size in the range 2-25 µm or have bubble sizes that are smaller or larger than microcellular foams. The foamed polymers are normally closed-cell, non-porous materials.

Background of the Invention

Solid state foamed polymers are generally closed cell plastic foams which contain a large number of very small cells or bubbles. Typically, such foams have a bubble density of more than 108 cells per cm3 with bubble diameters in the order of 10 µm. Compared with conventional solid polymers, solid state foamed polymers offer the possibility of a 20-80% reduction in material used while maintaining the essential mechanical properties of the polymer at relatively high levels. This in turn offers significant savings in material and transportation costs. Such lightweight polymers are particularly useful for applications where weight is a critical factor, for example in aircraft. In addition, preliminary data suggests that the microcellular polymers possess improved toughness and fatigue strength. This can be explained by the simple fact that these foams are derived from a polymer in the plastic solid state as opposed to the melt state. When an amorphous polymer is stretched at or slightly above its glass transition temperature, the resulting stretched polymer is oriented to the degree that it is stretched. Solid state foams, therefore exhibit cell walls of polymer in the oriented state.

Foamed polymers derived from the melted state have cell walls which are in the unoriented state. Unoriented cell walls derived from the melt state and oriented cell walls derived from the solid state have analogous properties to hot blown or unoriented films and oriented films, respectively. Hot blown films show low tensile strength, high elongation, little shrink and shrink force and poor flex life. Oriented films, on the other hand, show high tensile strength, low elongation, high shrink and shrink force and high flex life.

From this analogy one can see that foams derived from the solid state are uniquely different from foams derived from the melt state. It is not surprising, then, that properties such as toughness and fatigue strength would be quite different from foams derived from the melt state.

It is known that microcellular polymers can be produced by a two-step batch process in which a solid polymer is first exposed to a non-reacting gas, such as carbon dioxide or nitrogen, at elevated pressure for a period of time sufficient to achieve a concentration of gas in the polymer which is sufficient to permit bubble nucleation. The minimum gas concentration required for bubble nucleation varies with the gas/polymer system. For example, with polycarbonate and carbon dioxide a foam may be formed employing 20-120 mg of carbon dioxide per gram of polycarbonate. A higher gas concentration leads to nucleation of a higher number of bubbles which results in small bubble size in the foam. The gas concentration may be uniform or nonuniform. Uniformity of concentration leads to a more homogeneous bubble structure.

After exposure to the gas the polymer is subsequently returned to normal pressure, producing a supersaturated sample, and heated to the foaming temperature, which is above the glass transition temperature of the gas-saturated polymer, thereby causing a large number of bubbles to nucleate in the polymer. The polymer is held at the foaming temperature for a period of time sufficient to achieve a foam of the desired density and then cooled to quench bubble nucleation and growth.

The average bubble size is, in part, governed by the number of bubbles that nucleate which, in turn, is influenced by the concentration of gas in the polymer. The density of the microcellular polymer can be controlled by varying the gas saturation pressure, the foaming time and the foaming temperature.

Using this process, microcellular foams have been successfully produced from many different amorphous polymers, such as polyvinyl chloride (PVC), polycarbonate, polystyrene and ABS copolymer. For example, U.S. Patent No. 4,473,665 describes the production of microcellular polystyrene by saturation with nitrogen. For a review of recent advances in the field of microcellular polymers, see Kumar, V. (1993) Progress in Rubber and Plastics Technology, Vol. 9, pp. 54-70.

While methods for the production of discrete blocks, or sections, of microcellular polymer are well known in the art, attempts to produce continuous sheets or strips of these materials using the two-step process described above have been unsuccessful. Saturation of rolled polymer sheets with non-reacting gas is ineffective, with the gas being absorbed only at the exposed surfaces of the roll. On subjecting the gas-treated roll to elevated temperatures, foaming occurs only at the periphery of the polymer sheet.

Current methods for continuous production of microcellular polymer sheets consist of die-extruding molten polymer containing a foaming agent and passing the extruded polymer through a pair of cooled rollers (see, for example, U.S. Patent No. 4,456,571). Park and Suh have produced continuous microcellular filaments by saturating a molten polymer with a gas at a specific temperature and pressure prior to initiating bubble nucleation by raising the temperature of the polymer while maintaining the gas pressure at the level used for saturation (Park, C. and Suh, N.P., "Extrusion of a Microcellular Filament", Cellular Polymers, V.Kumar and S.G. Advani, editors; MD Vol. 38, ASME, 1992, p. 69).

U.S. Patent 4,761,256 to Hardenbrook et al. discloses a method for the continuous production of a microcellular plastic web material with an integral unmodified smooth skin, wherein a gas-impregnated plastic web is continuously delivered to a degassing device. The gas-impregnated plastic web is produced either by die extrusion under sufficiently high pressure to prevent bubble nucleation or by continuously drawing a nonimpregnated web through a pressurized chamber containing an inert gas. The latter technique is practical only for relatively thin webs, and will necessarily require a very large pressure chamber and complex dynamic seals in order to achieve sufficient gas concentration in the polymer.

There thus continues to be a need in the art for a simple, effective and inexpensive method for the continuous or semi-continuous production of microcellular polymer articles, sheets or filaments.

Summary of the Invention

It is an object of the present invention to provide a method and apparatus for the semi-continuous production of microcellular polymer articles, sheets or filaments as well as foamed polymers where the average bubble size is outside of the range 2 to 25 µm (less than 2 µm or greater than 25 µm), which is traditionally considered a microcellular foam.

It is a further object of the present invention to provide a method for producing microcellular polymer articles, sheets or filaments for minimal cost.

It is an additional object of the present invention to provide such a method which can be performed simply and with commonly available blowing gases with optional use of nucleating agents. Calcium carbonate and other known nucleating agents may be employed.

It is yet a further object of the present invention to provide such a method which employs inert gases that are not environmentally hazardous.

Still a further object of the present invention is to provide foamed polymer articles, sheets or filaments derived from the above method, and foamed articles, sheets or filaments having cell walls of polymer in the oriented condition.

These and other objectives are achieved according to the present invention by providing a gas channeling or exposing means interleaved or positioned between the layers of a polymer article, sheet or filament.

According to one aspect of the invention, there is provided a method for foaming polymeric materials, comprising the steps of:

  • (a) interleaving an article of polymeric material with a gas channeling means;
  • (b) exposing the interleaved article at elevated pressure to a non-reacting gas which is soluble in the polymer for a time sufficient to achieve a desired concentration of gas within the polymer, thereby forming an exposed polymeric article which is at least partially gas-saturated;
  • (c) separating the exposed polymer article from the interleaved gas channelling means; and
  • (d) heating the exposed polymer article sufficiently to initiate bubble nucleation and to achieve desired bubble growth.

According to another aspect of the invention, there is provided an apparatus for foaming polymeric materials, comprising;

  • (a) gas channelling means which is interleaved between the layers of a polymer article to form an interleaved article;
  • (b) means for saturating the interleaved article with a non-reacting gas which is soluble in the polymer;
  • (c) means for heating the polymer to initiate bubble nucleation and bubble growth;
  • (d) means for cooling the polymer to terminate bubble nucleation and bubble growth;
  • (e) means for mounting the saturated interleaved article in proximity to the heating and cooling means;
  • (f) means for separating the polymer article from the interleaved gas channelling means;
  • (g) means drawing the separated polymer article through the heating and cooling means; and
  • (h) means for tensioning the polymer article prior to drawing through the heating and cooling means.

According to a further aspect of the invention, there is provided a polymeric structure comprising:

  • (a) a plurality of shaped, foamable polymeric articles;
  • (b) gas channeling means interleaved between said polymeric articles, said polymeric articles being at least partially saturated with a gas at elevated pressure, no bubble nucleation having taken place in the polymeric material.

The gas channeling or exposing means preferably comprises a layer of flexible, gas permeable material, such as gauze, porous paper sheet, non-woven material, or particulate material, such as cornstarch. It has been found that use of the gas exposing material facilitates the permeation of gas into the body of the article, sheet or filament, enabling gas to enter the polymer surface and thereby reducing the time of gaseous diffusion into the polymeric article.

In a preferred embodiment of the present invention, a sheet of solid polymer is placed on a sheet of gas permeable material and the two layers of material rolled to form a roll consisting of layers of polymer interleaved with gas permeable material. The roll of interleaved polymer and gas permeable material can then be successfully foamed using the following process.

The interleaved roll is saturated under elevated pressure with a non-reacting gas which is soluble in the polymer for a time sufficient to achieve a desired concentration of gas within the polymer. After returning to normal pressure, the polymer sheet is gradually unrolled, separated from the gas permeable material, and drawn through a heating station for a time sufficient to achieve the desired foam density. Such a heating station may be a hot liquid bath e.g. a hot water bath, a hot gas or gases, a radiant heater or other means, where the saturated polymer is heated to the foaming temperature to initiate bubble nucleation and growth. After passing through the heating station, the polymer is cooled, for example, by drawing through a cold water bath, to quench bubble nucleation and growth. In order to prevent puckering of the foamed sheet, the polymer is held under tension while it is drawn through the heating and cooling stations.

Preferably, the drawing means comprises two rollers which engage the end of the polymer article and rotate in opposing directions.

The amount of bubble growth, and therefore the density of the resulting foam, is controlled by varying the heating station temperature and/or the rate at which the sheet moves through the heating and cooling step of the process. Preferably, bubble nucleation and growth is initiated by heating the exposed polymer article to a temperature in the range of about 80°C to about 200°C. Amorphous or semi-crystalline polymers with a maximum of about 30% crystallinity which have been quenched to the amorphous state and which can be foamed by the two-step batch process described above may also be successfully treated using the present invention. These include, for example, polystyrene, PVC, PMMA, polycarbonate, ABS copolymers and polyethylene terephthalate (PET). As used herein, the term "non-reaching gas" refers to a gas which does not react with the polymer being foamed. Gases which may be usefully employed in the present invention include nitrogen, carbon dioxide, air and argon.

An array of shaped polymeric articles spaced apart by gas channeling or interleaving means may be assembled so that it can be readily moved into and out of a pressure chamber. The array can preferably be a roll of polymeric sheet material wherein a porous paper sheet is interleaved between surfaces of the polymeric sheet so that the surfaces of the rolled sheet material will be exposed to gas within a pressure chamber. The array can also comprise a stack of polymeric sheets with porous paper, particulate material, or netting cr non-woven material separating the polymeric sheets. Folded, festooned, or wicket supported arrays can also be used.

The present invention provides a simple and effective way to form semi-continuous microcellular sheets of many different polymers, at minimal cost. The blowing gases employed are inexpensive, non-hazardous and readily available.

The above-mentioned and additional features of the present invention and the manner of obtaining them will be best understood by reference to the following more detailed description.

Detailed Description of the Invention

In accordance with the present invention, semi-continuous sheets or strips of microcellular polymers are produced by first forming a roll of solid polymer sheet with a gas channeling means interleaved between the layers of polymer. The gas channeling means preferably consists of a layer of flexible gas permeable material. While porous paper sheet is a preferred material, other gas permeable materials, such as particulate material, gauze, mesh, and woven or non-woven fabrics, may also be successfully employed in the present invention. Polymers which may be successfully foamed using the present invention include polystyrene, PVC, polycarbonate, ABS, Polysulfone, styrenebutadiene copolymer, polyamides, PMMA, and PET. In general, the class of glassy amorphous polymers with glass transition temperatures above ambient temperature are suitable for the present invention.

The roll of polymer sheet and gas channeling material is exposed under elevated pressure to a non-reacting gas which is soluble in the polymer for a time sufficient to achieve a desired concentration of gas-within the polymer. This step is generally carried out at room temperature (around 21 °C), although a higher temperature may be employed to accelerate diffusion of the gas within the polymer. The pressure can be varied above tank supply pressure with booster pumps. For example, the preferred range when employing CO2 is about 0.34 to 6.55 MPa (50 to 950 psi) tank pressure. This can be increased to over 6.89 MPa (1,000 psi) wich a suitable booster pump. A pressure as high as 9.65 MPa (1400 psi) is thought to be usable. The actual pressure chosen will depend on the desired final foam density and average bubble size. The preferred gas can depend upon the polymer being treated. For example, carbon dioxide is the preferred gas for use in foaming PET, PVC and polycarbonate, while nitrogen is the preferred gas for use in foaming polystyrene. The amount of time for which the polymer roll is exposed to gas varies with the thickness of the solid polymer sheet, the specific polymer-gas system, the saturation pressure, and the diffusion rate into the polymer, and is generally determined experimentally. However, periods of between 3 and 100 hours are typically employed. For example, when saturating a 0.51 mm (0.020 in) thick sheet of PET with CO2 a saturation time of between about 15 to 30 hours is preferred.

Following saturation of the polymer-gas permeable material roll, the roll is returned to normal pressure and mounted in proximity to a heating station, such as a hot water or glycerine bath maintained above the glass transition temperature of the gas-saturated polymer. The saturated polymer sheet is gradually unwound, separated from the gas permeable material and heated by drawing under tension through the heating station. The polymer sheet is thereby foamed in a continuous manner. After passing through the heating station, the polymer sheet is drawn through a cooling station, such as a cold water bath, a set of chilled rollers or simply air, to cool the polymer and stop bubble nucleation and growth. The temperature of the heating station as well as the rate at which the polymer sheet is drawn through the heating and cooling stations can be varied to provide sheets of varying bubble size and density.

The process described herein converts a roll of polymer sheet of a finite length into a roll of foamed sheet. The length of the solid polymer sheet that can be processed depends on the polymer-gas system. Once the polymer roll (permeated with a gas channeling means such as porous paper sheet) has been exposed to gas and is taken out from the pressure vessel to atmospheric pressure, the gas begins to leave the polymer sheet. Thus the roll must be processed into a foam promptly, within a certain "window cf processability," to avoid excessive loss of gas from the polymer, which can result in an undesirable variation in the density of the foam produced. Thus, to obtain foamed sheets with a consistent density, only a finite length of the solid polymer sheet can be processed at one time. For this reason, the method of the present invention has been termed a "semi-continuous" process. The semi-continuous nature of the process, however, does not in principle limit the rate of production of the foamed sheets. A sufficient number of semi-continuous lines can be operated in parallel to meet any production rate requirements.

Example 1.

A strip of PET Kodapak 9921 film measuring 5.18 m (17 ft) long, 76.2 mm (3 in.) wide and 0.51 mm (0.020 in) thick was placed on a strip of paper towel having similar dimensions. The resultant PET-paper towel strip was then wound onto a tubular core to form a roll having alternate layers of PET and paper towel. This roll was placed in a pressure vessel and exposed to carbon dioxide at a pressure of 4.83 MPa (700 psi) for 24 hours.

Following saturation with carbon dioxide, the PET-paper towel roll was removed from the pressure vessel, mounted on a spindle and suspended above a hot water bath maintained at 90 °C. The end of the saturated PET strip was gradually unwound from the roll, separated from the paper towel, and held under tension by threading through a spring-loaded clamp. Bubble nucleation was initiated and the PET strip foamed by drawing the strip through the hot water bath. Bubble growth was then quenched by drawing the strip through a cold water bath maintained at 0 °C. The PET strip was continuously drawn through the two water baths at a rate of approximately 10 cm/sec by engaging the strip between two rollers rotating in opposite directions.

The saturated PET strip began to foam immediately upon entering the hot water bath as indicated by a change in the transparency of the sheet from clear to opaque. The entire surface of the PET strip became opaque within 5 seconds of entering the bath, indicating that the carbon dioxide had permeated throughout the body of the PET-paper towel roll and fully saturated the roll. The foamed strip was flat and smooth, with even edges, and had a final length of 7.31 m (24 ft.), width of 114.3 mm (4.5 in.) and thickness of 0.76 mm (0.030 in.) The specific gravity of the foam was 0.3, compared with solid PET specific gravity of 1.3.

Comparative Examples.

A strip of PET film 5.18 m (17 ft) long, 76.2 mm (3 in.) wide and 0.51 mm (0.020 in.) thick was placed on a strip of paper towel having similar dimensions. The resultant PET-paper towel strip was coiled co form a roll having alternate layers of PET and paper towel and saturated with carbon dioxide as described in Example 1.

Following saturation with carbon dioxide, the PET-paper towel roll was removed from the pressure vessel and foamed by placing in a hot water bath maintained at a temperature slightly below 100 °C for 10 minutes. Bubble nucleation and growth was quenched by placing the roll in a cold water bath maintained at 0 °C for 5 minutes. On uncoiling the roll, it was found that foaming had occurred in a very uneven fashion with more foaming occurring on the outer surfaces of the polymer roll and less towards the middle. It was fpund that the foamed polymer roll had a wavy or puckered appearance.

Another strip of PET was processed as in Example 1, except that the strip was not interleaved with a gas channeling or diffusion means. It was not possible to foam this strip.

Example 2

A PET 5000 roll, 609.6 mm (24 in) wide x 0.51 mm (0.020 in) thick x 60.96 m (200 ft) long was pressurized to 5.17-5.52 MPa (750-800 psi.). The material foamed to 0.74 mm (0.029 in) thick x 812.8 mm (32 in) wide. Foaming speed was 18.29 m/min (60 ft/min) into hot water (96 °C) and exit speed was 27.4 m/min (90 ft/min).

Example 3

Similar conditions to Example 2 were run for a PET 6000 roll which expanded to a comparable extent. The resulting material specific gravities were: 1.3 unfoamed 0.5 foamed.

Example 4

PET G material was exposed to pressure under similar conditions to Examples 2 and 3. The material was subsequently foamed in 96 °C water. The resulting material specific gravity was 1.25 unfoamed and 0.17 foamed.

Although the present invention has been described in terms of specific embodiments, changes and modifications can be carried out without departing from the scope of the invention which is intended to be limited only by the scope of the appended claims.


Anspruch[de]
  1. Verfahren zum Schäumen von polymeren Materialien, umfassend die Schritte:
    • (a) Interleaving bzw. Einschießen eines Artikels aus polymerem Material mit einem Gas-Kanalisierungsmittel;
    • (b) Unterwerfen des durchgeschossenen Artikels bei einem erhöhten Druck einem nicht-reagierenden Gas, welches in dem Polymer löslich ist, während einer ausreichenden Zeit, um eine gewünschte Konzentration von Gas in dem Polymer zu erzielen, unter Bildung eines exponierten polymeren Artikels, welcher zumindest teilweise gasgesättigt ist;
    • (c) Separieren des exponierten Polymerartikels von dem eingeschossenen bzw. dazwischen gelegten Gas-Kanalisierungsmittel; und
    • (d) ausreichendes Erhitzen des exponierten Polymerartikels zur Initiierung einer Blasennukleierung und zur Erzielung des gewünschten Blasenwachstums.
  2. Verfahren nach Anspruch 1, wobei eine Vielzahl an Artikeln mit Gas-Kanalisierungsmitteln eingeschossen wird.
  3. Verfahren nach Anspruch 1, weiterhin umfassend den Schritt des Abkühlens des Polymerartikels nach einer/einem Blasennukleierung und -wachstum.
  4. Verfahren nach Anspruch 1 oder 2, wobei der Polymerartikel eine in raffartiger Weise gefaltete Endlosfolie bzw. -bahn ist.
  5. Verfahren nach Anspruch 1 oder 2, wobei der polymere Artikel ein Stapel von polymeren Bahnen bzw. Folien ist.
  6. Verfahren nach Anspruch 1 oder 2, wobei der polymere Artikel eine Rolle von polymerem Material ist.
  7. Verfahren nach Anspruch 1 oder 2, wobei das Gas-Kanalisierungsmittel eine Folie aus flexiblem gasdurchlässigen Material umfasst.
  8. Verfahren nach Anspruch 7, wobei das flexible gasdurchlässige Material ein poröses Papierblatt ist.
  9. Verfahren nach Anspruch 1 oder 2, wobei das Gas-Kanalisierungsmittel teilchenförmiges Material ist.
  10. Verfahren nach Anspruch 1, wobei Blasennukleierung und -wachstum durch Erhitzen des exponierten Polymerartikels auf die Glasübergangstemperatur des exponierten Polymers initiiert werden.
  11. Verfahren nach Anspruch 10, wobei Blasennukleierung und -wachstum durch Ziehen bzw. Recken des exponierten Polymerartikels durch ein Heizmittel, gewählt aus der Gruppe bestehend aus heißen Flüssigbädern, heißem Gas oder Gasen und Strahlungsheizern, initiiert werden.
  12. Verfahren nach Anspruch 11, wobei der exponierte Polymerartikel unter Spannung gehalten wird, während er durch das Heizmittel gezogen wird.
  13. Verfahren nach Anspruch 1, wobei Blasennukleierung und -wachstum durch Kühlen des exponierten Polymerartikels beendet werden.
  14. Verfahren nach Anspruch 1 oder 2, wobei der Polymerartikel gewählt ist aus der Gruppe bestehend aus Polystyrol, Polyvinylchlorid, Polycarbonat, PMMA, ABS-Copolymeren und Polyethylenterephthalat.
  15. Verfahren nach Anspruch 1 oder 2, wobei das nicht reagierende Gas gewählt ist aus der Gruppe bestehend aus Stickstoff, Kohlendioxid und Luft.
  16. Verfahren nach Anspruch 1 oder 2, wobei der Polymerartikel Polyethylenterephthalat ist und das nicht-reaktive Gas Kohlendioxid ist.
  17. Verfahren nach Anspruch 16, wobei das Gas-Kanalisierungsmittel eine Bahn bzw. Folie aus flexiblem gasdurchlässigen Material ist.
  18. Verfahren nach Anspruch 17, wobei das gasdurchlässige Material ein poröses Papierblatt ist.
  19. Verfahren nach Anspruch 18, wobei der eingeschossene Artikel Kohlendioxid bei einem Druck im Bereich von etwa 0,34 MPa (50 psi) bis etwa 9,65 MPa (1400 psi) ausgesetzt wird.
  20. Verfahren nach Anspruch 16, wobei der eingeschossene Artikel Kohlendioxid für einen Zeitraum zwischen etwa 3 und etwa 100 Stunden ausgesetzt wird.
  21. Verfahren nach Anspruch 16, wobei Blasennukleierung und -wachstum durch Erhitzen des exponierten Polymerartikels auf eine Temperatur im Bereich von etwa 80°C bis etwa 200°C initiiert werden.
  22. Verfahren nach Anspruch 16, wobei Blasennukleierung und -wachstum durch Kühlen des exponierten Polymerartikels gelöscht bzw. beendet werden.
  23. Verfahren nach Anspruch 3, wobei das Kühlen durch Ziehen des Polymerartikels durch ein Mittel zum Kühlen bewerkstelligt wird.
  24. Verfahren nach Anspruch 23, wobei das Kühlen des Polymerartikels durch Ziehen des Polymerartikels durch kalte Luft bewerkstelligt wird.
  25. Verfahren nach Anspruch 23, wobei das Kühlen des Polymerartikels durch Ziehen des Polymerartikels durch kaltes Wasser bewerkstelligt wird.
  26. Vorrichtung zum Schäumen polymerer Materialien, umfassend:
    • (a) Gas-Kanalisierungsmittel, welches zwischen den Schichten eines Polymerartikels zur Bildung eines eingeschossenen Artikels eingeschossen wird;
    • (b) Mittel zum Sättigen des eingeschossenen Artikels mit einem nicht reagierenden Gas, welches in dem Polymer löslich ist.
    • (c) Mittel zum Erhitzen des Polymers zur Initiierung der Blasennukleierung und des Blasenwachstums;
    • (d) Mittel zum Kühlen des Polymers zur Beendigung der Blasennukleierung und des Blasenwachstums;
    • (e) Mittel zum Montieren des gesättigten eingeschossenen Artikels in der Nähe des Heiz- und Kühlmittels;
    • (f) Mittel zum Trennen des Polymerartikels von dem eingeschossenen Gas-Kanalisierungsmittel;
    • (g) Mittel zum Ziehen des getrennten Polymerartikels durch das Heiz- und Kühlmittel; und
    • (h) Mittel zum Spannen des Polymerartikels vor dem Ziehen durch das Heiz- und Kühlmittel.
  27. Vorrichtung nach Anspruch 26, wobei das Gas-Kanalisierungsmittel ein flexibles gasdurchlässiges Material umfasst.
  28. Vorrichtung nach Anspruch 27, wobei das Gas-Kanalisierungsmittel ein poröses Papierblatt umfasst.
  29. Vorrichtung nach Anspruch 26, wobei das Gas-Kanalisierungsmittel teilchenförmiges Material ist.
  30. Vorrichtung nach Anspruch 26, wobei das Gas-Sättigungsmittel ein Druckbehälter ist.
  31. Vorrichtung nach Anspruch 26, wobei das Heizmittel gewählt ist aus der Gruppe bestehend aus einem heißen Flüssigkeitsbad, heißem Gas oder Gasen und Strahlungsheizgeräten.
  32. Vorrichtung nach Anspruch 26, wobei das Kühlmittel ein Kaltwasserbad ist.
  33. Vorrichtung nach Anspruch 26, wobei das Ziehmittel bzw. Zugeinrichtung zwei Walzen umfasst, die das Ende des Polymerartikels aufnehmen und sich in entgegengesetzten Richtungen drehen.
  34. Vorrichtung nach Anspruch 26, wobei das Montierungsmittel eine Spindel umfasst.
  35. Polymere Struktur, umfassend:
    • (a) eine Vielzahl an geformten schäumbaren Polymerartikeln:
    • (b) Gas-Kanalisierungsmittel, eingeschossen zwischen den Polymerartikeln, wobei die Polymerartikel zumindest teilweise mit einem Gas bei erhöhtem Druck gesättigt werden, wobei es zu keiner Blasennukleierung in dem polymeren Material kam.
  36. Polymere Struktur nach Anspruch 35, wobei der Artikel eine in raffartiger Weise gefaltete Folie mit Gas-Kanalisierungsmitteln zwischen den benachbarten Folienoberflächen ist.
  37. Polymere Struktur nach Anspruch 35, wobei der Artikel eine Rolle von polymerer Folie mit einem zwischen den Rollen einer Folie eingeschossenen Gas-Kanalisierungsmittel ist.
  38. Polymere Struktur nach Anspruch 36 oder 37, wobei das Einschussmaterial poröse Papierbahnen bzw. -blätter sind.
  39. Polymere Struktur nach Anspruch 35, wobei das polymere Material gewählt ist aus der Gruppe bestehend aus PET, Polysulfon, Styrol-Butadien-Copolymer, Polystyrol, PVDC, Polyamiden und Polycarbonat.
  40. Polymere Struktur nach Anspruch 35, wobei das polymere Material mit Gas, gewählt aus der Gruppe bestehend aus Kohlendioxid, Luft, Argon und Stickstoff, gesättigt wird.
  41. Polymere Struktur nach Anspruch 35, wobei das Einschussmaterial gewählt ist aus der Gruppe bestehend aus teilchenförmigen Material, porösem nicht-gewebtem Material und gewebtem Material.
Anspruch[en]
  1. A method for foaming polymeric materials, comprising the steps of:
    • (a) interleaving an article of polymeric material with a gas channeling means;
    • (b) exposing the interleaved article at elevated pressure to a non-reacting gas which is soluble in the polymer for a time sufficient to achieve a desired concentration of gas within the polymer, thereby forming an exposed polymeric article which is at least partially gas-saturated;
    • (c) separating the exposed polymer article from the interleaved gas channelling means; and
    • (d) heating the exposed polymer article sufficiently to initiate bubble nucleation and to achieve desired bubble growth.
  2. The method of claim 1 wherein a plurality of articles are interleaved with gas channeling means.
  3. The method of claim 1 further comprising the step of cooling the polymer article after bubble nucleation and growth.
  4. The method of claim 1 or 2 wherein the polymeric article is a continuous sheet folded in a festooned manner.
  5. The method of claim 1 or 2 wherein the polymeric article is a stack of polymeric sheets.
  6. The method of claim 1 or 2 wherein the polymeric article is a roll of polymeric material.
  7. The method of claim 1 or 2 wherein the gas channelling means comprises a sheet of flexible, gas permeable material.
  8. The method of claim 7 wherein the flexible, gas permeable material is porous paper sheet.
  9. The method of claim 1 or 2 wherein the gas channeling means is particulate material.
  10. The method of claim 1 wherein bubble nucleation and growth is initiated by heating the exposed polymer article to above the glass transition temperature of the exposed polymer.
  11. The method of claim 10 wherein bubble nucleation and growth is initiated by drawing the exposed polymer article through a heating means selected from the group consisting of hot liquid baths, hot gas or gases, and radiant heaters.
  12. The method of claim 11 wherein the exposed polymer article is held under tension while being drawn through the heating means.
  13. The method of claim 1 wherein bubble nucleation and growth is terminated by cooling the exposed polymer article.
  14. The method of claim 1 or 2 wherein the polymer article is selected from the group consisting of polystyrene, polyvinyl chloride, polycarbonate, PMMA, ABS copolymers and polyethylene terephthalate.
  15. The method of claim 1 or 2 wherein the non-reacting gas is selected from the group consisting of nitrogen, carbon dioxide and air.
  16. The method of claim 1 or 2 wherein the polymer article is polyethylene terephthalate and the nonreactive gas is carbon dioxide.
  17. The method of claim 16 wherein the gas channelling means is a sheet of flexible, gas permeable material.
  18. The method of claim 17 wherein the gas permeable material is porous paper sheet.
  19. The method of claim 18 wherein the interleaved article is exposed to carbon dioxide at a pressure in the range of about 0.34 MPa (50 psi) to about 9.65 MPa (1400 psi).
  20. The method of claim 16 wherein the interleaved article is exposed to carbon dioxide for a period of between about 3 and about 100 hours.
  21. The method of claim 16 wherein bubble nucleation and growth is initiated by heating the exposed polymer article to a temperature in the range of about 80°C to about 200°C.
  22. The method of claim 16 wherein bubble nucleation and growth is quenched by cooling the exposed polymer article.
  23. The method of claim 3 wherein the cooling is accomplished by drawing the polymer article through a means for cooling.
  24. The method of claim 23 wherein the cooling of the polymer article is accomplished by drawing the polymer article through cold air.
  25. The method of claim 23 wherein the cooling of the polymer article is accomplished by drawing the polymer article through cold water.
  26. An apparatus for foaming polymeric materials, comprising:
    • (a) gas channelling means which is interleaved between the layers of a polymer article to form an interleaved article;
    • (b) means for saturating the interleaved article with a non-reacting gas which is soluble in the polymer;
    • (c) means for heating the polymer to initiate bubble nucleation and bubble growth;
    • (d) means for cooling the polymer to terminate bubble nucleation and bubble growth;
    • (e) means for mounting the saturated interleaved article in proximity to the heating and cooling means;
    • (f) means for separating the polymer article from the interleaved gas channelling means;
    • (g) means for drawing the separated polymer article through the heating and cooling means; and
    • (h) means for tensioning the polymer article prior to drawing through the heating and cooling means.
  27. The apparatus of claim 26 wherein the gas channelling means comprises a flexible, gas permeable material.
  28. The apparatus of claim 27 wherein the gas channelling means comprises porous paper sheet.
  29. The apparatus of claim 26 wherein the gas channelling means is particulate material.
  30. The apparatus of claim 26 wherein the gas saturation means is a pressure vessel.
  31. The apparatus of claim 26 wherein the heating means is selected from the group consisting of hot liquid bath, hot gas or gases, and radiant heaters.
  32. The apparatus of claim 26 wherein the cooling means is a cold water bath.
  33. The apparatus of claim 26 wherein the drawing means comprises two rollers which engage the end of the polymer article and rotate in opposing directions.
  34. The apparatus of claim 26 wherein the mounting means comprises a spindle.
  35. A polymeric structure comprising:
    • (a) a plurality of shaped, foamable polymeric articles;
    • (b) gas channelling means interleaved between said polymeric articles, said polymeric articles being at least partially saturated with a gas at elevated pressure, no bubble nucleation having taken place in the polymeric material.
  36. The polymeric structure of claim 35 wherein the article is a festooned, folded sheet with gas channelling means between the adjacent sheet surfaces.
  37. The polymeric structure of claim 35 wherein the article is a roll of polymeric film with gas channelling means interleaved between the rolls of film.
  38. The polymeric structure of claim 36 or 37 wherein the interleaving material is porous paper sheets.
  39. The polymeric structure of claim 35 wherein the polymeric material is selected from the group consisting of PET, polysulfone, styrenebutadiene copolymer, polystyrene, PVDC, polyamides, and polycarbonate.
  40. The polymeric structure of claim 35 wherein the polymeric material is saturated with gas selected from the group consisting of carbon dioxide, air, argon and nitrogen.
  41. The polymeric structure of claim 35 wherein the interleaving material is selected from the group consisting of particulate material, porous non-woven material, and woven material.
Anspruch[fr]
  1. Procédé pour le moussage de matières polymères, comprenant les étapes consistant :
    • (a) à imbriquer un article de matière polymère avec un moyen de cheminement de gaz ;
    • (b) à exposer l'article imbriqué à une pression élevée à un gaz non réactif qui est soluble dans le polymère pendant un temps suffisant pour atteindre une concentration désirée du gaz dans le polymère, en formant ainsi un article polymère exposé qui est au moins partiellement saturé de gaz ;
    • (c) à séparer l'article polymère exposé du moyen de cheminement de gaz imbriqué ; et
    • (d) à chauffer l'article polymère exposé suffisamment pour déclencher une nucléation de bulles et pour parvenir à une croissance de bulles désirée.
  2. Procédé suivant la revendication 1, dans lequel une pluralité d'articles est imbriquée avec un moyen de cheminement de gaz.
  3. Procédé suivant la revendication 1, comprenant en outre l'étape de refroidissement de l'article polymère après nucléation et croissance de bulles.
  4. Procédé suivant la revendication 1 ou 2, dans lequel l'article polymère est une feuille continue pliée de manière festonnée.
  5. Procédé suivant la revendication 1 ou 2, dans lequel l'article polymère est un empilement de feuilles polymères.
  6. Procédé suivant la revendication 1 ou 2, dans lequel l'article polymère est un rouleau de matière polymère.
  7. Procédé suivant la revendication 1 ou 2, dans lequel le moyen de cheminement de gaz comprend une feuille de matière flexible perméable aux gaz.
  8. Procédé suivant la revendication 7, dans lequel la matière flexible perméable aux gaz est une feuille de papier poreux.
  9. Procédé suivant la revendication 1 ou 2, dans lequel le moyen de cheminement de gaz est une matière en particules.
  10. Procédé suivant la revendication 1, dans lequel la nucléation et la croissance de bulles sont déclenchées en chauffant l'article polymère exposé à une température supérieure à la température de transition vitreuse du polymère exposé.
  11. Procédé suivant la revendication 10, dans lequel la nucléation et la croissance de bulles sont déclenchées en tirant l'article polymère exposé à travers un moyen de chauffage choisi dans le groupe consistant en des bains d'un liquide chaud, un ou plusieurs gaz chauds et des systèmes de chauffage par rayonnement.
  12. Procédé suivant la revendication 11, dans lequel l'article polymère exposé est maintenu sous tension tout en étant tiré à travers le moyen de chauffage.
  13. Procédé suivant la revendication 1, dans lequel la nucléation et la croissance de bulles sont interrompues par refroidissement de l'article polymère exposé.
  14. Procédé suivant la revendication 1 ou 2, dans lequel l'article polymère est choisi dans le groupe consistant en polystyrène, poly(chlorure de vinyle), polycarbonate, PMMA, copolymères ABS et poly(téréphtalate d'éthylène).
  15. Procédé suivant la revendication 1 ou 2, dans lequel le gaz non réactif est choisi dans le groupe consistant en azote, dioxyde de carbone et air.
  16. Procédé suivant la revendication 1 ou 2, dans lequel l'article polymère est le poly(téréphtalate d'éthylène) et le gaz non réactif est le dioxyde de carbone.
  17. Procédé suivant la revendication 16, dans lequel le moyen de cheminement de gaz est une feuille de matière flexible perméable aux gaz.
  18. Procédé suivant la revendication 17, dans lequel la matière perméable aux gaz est une feuille de papier poreux.
  19. Procédé suivant la revendication 18, dans lequel l'article imbriqué est exposé à du dioxyde de carbone à une pression comprise dans l'intervalle de 0,34 MPa (50 psi) à environ 9,65 MPa (1400 psi).
  20. Procédé suivant la revendication 16, dans lequel l'article imbriqué est exposé à du dioxyde de carbone pendant une période de temps d'environ 3 à environ 100 heures.
  21. Procédé suivant la revendication 16, dans lequel la nucléation et la croissance de bulles sont déclenchées en chauffant l'article polymère exposé à une température comprise dans l'intervalle d'environ 80°C à environ 200°C.
  22. Procédé suivant la revendication 16, dans lequel la nucléation et la croissance de bulles sont désactivées par refroidissement de l'article polymère exposé.
  23. Procédé suivant la revendication 3, dans lequel le refroidissement est effectué en tirant l'article polymère à travers un moyen de refroidissement.
  24. Procédé suivant la revendication 23, dans lequel le refroidissement de l'article polymère est effectué en tirant l'article polymère à travers de l'air froid.
  25. Procédé suivant la revendication 23, dans lequel le refroidissement de l'article polymère est effectué en tirant l'article polymère à travers de l'eau froide.
  26. Appareil pour le moussage de matières polymères, comprenant :
    • (a) un moyen de cheminement de gaz qui est imbriqué entre les couches d'un article polymère pour former un article imbriqué ;
    • (b) un moyen pour saturer l'article imbriqué avec un gaz non réactif qui est soluble dans le polymère ;
    • (c) un moyen pour chauffer le polymère afin de déclencher la nucléation de bulles et la croissance de bulles ;
    • (d) un moyen pour refroidir le polymère afin d'interrompre la nucléation de bulles et la croissance de bulles ;
    • (e) un moyen pour monter l'article imbriqué saturé à proximité du moyen de chauffage et du moyen de refroidissement ;
    • (f) un moyen pour séparer l'article polymère du moyen de cheminement de gaz imbriqué ;
    • (g) un moyen pour tirer l'article polymère séparé à travers le moyen de chauffage et le moyen de refroidissement ; et
    • (h) un moyen pour mettre sous tension l'article polymère avant de le tirer à travers le moyen de chauffage et le moyen de refroidissement.
  27. Appareil suivant la revendication 26, dans lequel le moyen de cheminement de gaz comprend une matière flexible perméable aux gaz.
  28. Appareil suivant la revendication 27, dans lequel le moyen d'acheminement de gaz comprend une feuille de papier poreux.
  29. Appareil suivant la revendication 26, dans lequel le moyen d'acheminement de gaz est une matière en particules.
  30. Appareil suivant la revendication 26, dans lequel le moyen de saturation de gaz est un récipient résistant à la pression.
  31. Appareil suivant la revendication 26, dans lequel le moyen de chauffage est choisi dans le groupe consistant en un bain d'un liquide chaud, un ou plusieurs gaz chauds et des systèmes de chauffage par rayonnement.
  32. Appareil suivant la revendication 26, dans lequel le moyen de refroidissement est un bain d'eau froide.
  33. Appareil suivant la revendication 26, dans lequel le moyen de tirage comprend deux rouleaux qui viennent en prise avec l'extrémité de l'article polymère et qui tournent dans des sens opposés.
  34. Appareil suivant la revendication 26, dans lequel le moyen de montage comprend une broche.
  35. Structure polymère comprenant :
    • (a) une pluralité d'articles polymères façonnés, aptes au moussage ;
    • (b) un moyen de cheminement de gaz imbriqué entre lesdits articles polymères, lesdits articles polymères étant au moins partiellement saturés d'un gaz à une pression élevée, aucune nucléation de bulles n'ayant eu lieu dans la matière polymère.
  36. Structure polymère suivant la revendication 35, dans laquelle l'article est une feuille pliée festonnée avec un moyen de cheminement de gaz entre les surfaces de feuille adjacentes.
  37. Structure polymère suivant la revendication 35, dans laquelle l'article est un rouleau de film polymère avec un moyen de cheminement de gaz imbriqué entre les spires du film.
  38. Structure polymère suivant la revendication 36 ou 37, dans laquelle la matière à imbriquer consiste en feuilles de papier poreux.
  39. Structure polymère suivant la revendication 35, dans laquelle la matière polymère est choisie dans le groupe consistant en PET, polysulfone, copolymère styrène-butadiène, polystyrène, PVDC, polyamides et polycarbonates.
  40. Structure polymère suivant la revendication 35, dans laquelle la matière polymère est saturée d'un gaz choisi dans le groupe consistant en dioxyde de carbone, air, argon et azote.
  41. Structure polymère suivant la revendication 35, dans laquelle la matière à imbriquer est choisie dans le groupe consistant en une matière en particules, une matière non tissée poreuse et une matière tissée.






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A Täglicher Lebensbedarf
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G Physik
H Elektrotechnik

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