Ulllted States Patent
`
`
`Karabedian et al.
`
`
`
`[19]
`
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`[11] Patent Number:
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`
`
`[45] Date of Patent:
`
`
`5,925,450
`
`
`
`*Jul. 20, 1999
`
`US005925450A
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`
`
`1/1984 Johnson etal.
`4,424,287
`......................... .. 521/74
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`1%/Iay(:rC1sae:ta:i ...........................
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`Z1333 §ZiZ1‘I:*;?a;;';;';1:“...
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`8/1995 K b d’
`5,443,769
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`1.
`264/46.1
`5,674,602 10/1997 K:i:b:di:: :t:1.
`.. 428/304.4
`
`
`
`
`
`
`FOREIGN PATENT DOCUMENTS
`
`
`
`11/1979 Australia .
`
`
`
`
`
`
`
`7952724
`
`
`
`Primary Examiner—Daniel Zirker
`
`
`
`
`
`ABSTRACT
`[57]
`The method of making polystyrene foam for foam products
`
`
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`
`
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`
`
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`
`
`
`which comprises utilizing atmospheric gases as the blowing
`agents or preferably mixing one or more of these gases and
`
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`
`
`
`
`
`
`
`
`
`
`
`
`
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`a biending agent Which is n0n'V0iaiiie at
`ine extrusion
`temperatures, introducing the mixture to a molten thermo-
`
`
`
`
`
`
`plastic polystyrene resin containing nucleating agents such
`
`
`
`
`
`
`
`as sodium bicarbonate and citric acid and extrudin
`the
`
`
`
`
`
`
`
`
`
`.
`g
`.
`thermoplastic in the form of a foam. The resultant foam has
`
`
`
`
`
`
`
`
`substantially no residual blowing agent,
`is dimensionally
`
`
`
`
`
`
`stable at ambient temperatures and when used with a non-
`
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`
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`Volatile blending agent can be made with small amounts of
`
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`
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`blowing agent permitting cooling of the melt without high
`
`
`
`
`
`
`
`
`loading on the extruder. The foam may be coextruded with
`
`
`
`
`
`
`
`
`one or more layers of thermoplastic film so that the resultant
`
`
`
`
`
`
`
`
`product is adapted for use for plates, cups, food containers
`
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`
`
`
`
`
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`or packaging and for labels for containers such as glass and
`
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`plastic containers and for labels that are shrunk in place on
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`a Container.
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`19 Claims, 3 Drawing Sheets
`
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`0075/01.‘ SUPPLY
`
`[54] POLYSTYRENE FOAM SHEET
`
`
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`
`
`Inventors;
`
`
`
`[75]
`
`
`
`
`
`iflinies A_V1V{a]n)';libel:1iaili;1To]edo:1onio;
`aurice
`I
`ac We er, Bar Stown’
`
`
`
`K»
`
`.
`,
`,
`,
`[73] Assign” ¥V1V°d‘l‘5'iOiit‘li‘°‘5 Piastic Products inc->
`
`
`
`
`
`
`
`
`o e o,
`10
`
`[*] Notice:
`
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`
`
`This patent is subject to a terminal dis-
`
`
`
`
`
`claimer.
`
`
`
`
`
`
`[21] Appl. No.: 08/944,591
`[22]
`Filed:
`Oct 6’ 1997
`
`
`
`
`Related U_S_ Application Data
`
`
`
`
`
`
`
`[51]
`
`
`
`
`
`
`
`
`
`
`[63] Continuation of application No. 08/117,961, Sep. 7, 1993,
`Pat, No, 5,674,602, which is a continuation of application
`
`
`
`
`
`
`N0~ 07/752,430, A118 30; 1991, abaI1d0I16d, Which is ii
`
`
`
`
`
`
`
`Continuation Of application No‘ 07/5389291’ Jun‘ 14’ 1990’
`
`
`
`
`
`
`Pat. No. 5,082,608.
`
`
`
`
`
`Int. Cl.6 ............................ .. B32B 3/26; B29C 41/00;
`
`
`
`
`
`
`
`B29C 17/00
`
`
`....................... .. 428/304.4; 264/51; 264/230;
`
`
`
`
`264/342 R; 264/342 RE
`
`
`[58] Field of Search ......................... .. 428/304.4; 264/51,
`
`
`
`
`
`
`264/230, 342 R, 342 RE
`
`
`
`
`[52] U.S. Cl.
`
`
`
`[56]
`
`
`
`References Cited
`
`
`
`U.S. PATENT DOCUMENTS
`
`
`
`3/1974 Greenberg ............................... .. 264/50
`
`
`
`
`9/1977 Luthra .................................. .. 264/45.5
`
`
`
`
`
`3,796,779
`
`4,049,768
`
`
`'9 '46“”7
`,4ca/maz,470/2
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`42
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`PAGE 1 OF 11
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`Jul. 20, 1999
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`Sheet 1 of3
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`5,925,450
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`U.S. Patent
`
`
`
`
`Jul. 20, 1999
`
`
`Sheet 2 of3
`
`
`
`5,925,450
`
`
`
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`PAGE 3 OF 11
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`PAGE 3 OF 11
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`

`
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`U.S. Patent
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`
`
`
`Jul. 20, 1999
`
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`
`Sheet 3 of3
`
`
`
`5,925,450
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`
`
`PAGE 4 OF 11
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`PAGE 4 OF 11
`
`

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`5,925,450
`
`
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`2
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`charges are introduced by means of a free piston-cylinder
`
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`
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`combination given motive power by said supply gas source.
`
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`
`
`
`
`Although this patent mentions the use of a number of
`
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`
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`atmospheric gases, no claim was made as to any beneficial
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`
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`results as to the product and no commercial use has been
`
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`made of such a process.
`
`
`
`Among the objectives of the present invention are to
`
`
`
`
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`
`
`
`provide a method of making polystyrene foam wherein the
`
`
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`
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`method utilizes atmospheric gases as blowing agents which
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`are inherent in the atmosphere; wherein the blowing agent is
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`substantially entirely released when the polystyrene foam is
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`extruded; wherein the melt can be cooled to normal process
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`levels and not create high loading on the extruder or shear
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`heat from high polymer viscosity; wherein the amount of
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`shrinkage can be controlled as may be required for the
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`ultimate use of the foam; wherein the density and cell size
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`can be controlled; and which utilizes conventional extrusion
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`apparatus.
`
`In accordance with the invention, the method of making
`
`
`
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`
`
`polystyrene foam comprises mixing an atmospheric gas such
`
`
`
`
`
`
`
`as carbon dioxide, nitrogen or air and preferably a non-
`
`
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`
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`volatile blending agent, introducing the gas or the mixture to
`
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`
`
`
`
`
`
`a molten thermoplastic polystyrene resin containing nucle-
`
`
`
`
`
`
`
`ating agents such as sodium bicarbonate and citric acid and
`
`
`
`
`
`
`
`
`
`extruding the thermoplastic in the form of a foam. The
`
`
`
`
`
`
`
`
`resultant foam has substantially no residual blowing agent,
`
`
`
`
`
`
`
`is dimensionally stable at ambient temperatures and when
`
`
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`
`used with a non-volatile blending agent can be made with
`
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`small amounts of blowing agent permitting melt cooling
`
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`without high loading on the extruder. The foam may be
`
`
`
`
`
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`
`
`
`coextruded with one or more layers of a thermoplastic film
`
`
`
`
`
`
`
`so that the resultant product is adapted for use for plates,
`
`
`
`
`
`
`
`
`
`
`cups, food containers or packaging and for labels for con-
`
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`
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`
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`tainers such as glass and plastic containers and for labels that
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`are shrunk in place on the container.
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`DESCRIPTION OF THE DRAWINGS
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`FIG. 1 is a schematic drawing of an extrusion apparatus
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`utilized in the method.
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`FIG. 2 is a partly schematic diagram of a portion of the
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`extrusion apparatus.
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`FIG. 3 is a schematic drawing of an apparatus utilized in
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`the process downstream of the extruder.
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`FIG. 4 is a partly schematic diagram of a modified form
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`of extrusion apparatus.
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`DESCRIPTION
`
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`In accordance with the invention, an atmospheric gas such
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`as carbon dioxide, nitrogen or air alone or preferably com-
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`bined with a blending agent which is non-volatile at the
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`extrusion temperatures such as a high molecular weight ester
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`having low volatility at high temperatures is introduced into
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`the thermoplastic molten polystyrene melt, and the mixture
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`is extruded.
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`Where a mixture of atmospheric gas and a blending agent
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`which is non-volatile at the extrusion temperatures is used,
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`the atmospheric gas and the non-volatile blending agent may
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`be mixed prior to introduction or separately.
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`Referring to FIG. 1, the atmospheric gas is supplied to the
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`first stage of a tandem extruder system through a pressure
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`regulator, heater, two stage gas booster and accumulator,
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`mass flow meter control valve, second heater and pressure
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`regulator to the molten massive plastic material in the first
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`or primary extruder section. Where the liquid non-volatile
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`blending agent such as the non-volatile ester is used, it is
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`1
`POLYSTYRENE FOAM SHEET
`
`MANUFACTURE
`
`
`
`
`This application is a continuation of application Ser. No.
`
`
`
`
`
`
`08/117,961 filed Sep. 7, 1993, now U.S. Pat. No. 5,674,602,
`
`
`
`
`
`
`
`
`
`which is a continuation of application Ser. No. 07/752,430
`
`
`
`
`
`
`filed Aug. 30, 1991 and now abandoned, which is a con-
`
`
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`
`
`
`
`
`tinuation of application Ser. No. 07/538,291 filed Jun. 14,
`
`
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`
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`
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`1990, now U.S. Pat. No. 5,082,608.
`
`
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`
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`This invention relates to manufacture of foam and par-
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`ticularly the manufacture of polystyrene foam.
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`BACKGROUND AND SUMMARY OF THE
`
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`
`
`INVENTION
`
`In the manufacture of polystyrene foam,
`it has been
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`common to utilize blowing agents such as chlorofluorocar-
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`bons solely or together with alkanes, usually pentane or
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`isopentane. Such a foam is usually made by extrusion. Due
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`to the solubility of chlorofluorocarbons and certain alkanes
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`in polystyrene, the extrusion melt viscosity is reduced and
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`this permits sufficient cooling of the melt so that high load,
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`indicated by amperage, will not be applied to the extruder
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`drive motor.
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`Pentane and chlorofluorocarbons such as Freon 11 and 12,
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`for example, are partially soluble in polystyrene and reduce
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`the melt viscosity enabling the extruder adequately to cool
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`and extrude the molten plastic material at lower loads and
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`temperatures in order to generate a good smooth foam
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`surface and appearance, small cell size control for opacity
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`and other foam physical properties such as orientation,
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`shrinkage characteristics and stiffness. Loss of residual
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`blowing agent over a period of time, however, creates a
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`shrinkage in the sheet material, an increase in thickness and
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`an increase in softening point temperature as the residual
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`blowing agent is reduced.
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`Where the foam is intended for use as a label on glass or
`
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`
`plastic containers wherein the label is shrunk in place, the
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`foam material is extruded and stretched in one direction
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`more than the other. Preferably, the label material is coex-
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`truded with a plastic film. The gradual
`loss of residual
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`blowing agent causes the label material to vary in shrinkage
`
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`characteristics.
`
`U.S. Pat. No. 4,424,287 is directed to a polymer foam
`
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`
`
`
`
`process for making thermoformed articles wherein the blow-
`
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`ing agent comprises at least an atmospheric gas and at least
`
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`one volatile plasticizing blowing agent. As stated in this
`
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`patent, early attempts to mix normally liquid hydrocarbons
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`and normally gaseous blowing agents have not been suc-
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`cessful and it is necessary that great care be exercised in
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`production of a polymer foam with highly-volatile blowing
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`agents such as carbon dioxide even in such a mixture.
`
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`
`Accordingly, as set forth in this patent,
`it was thought
`
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`
`necessary to utilize both the inert gas such as carbon dioxide
`
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`and a volatile plasticizing organic blowing agent such as
`
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`pentane and to thermoform the articles immediately after
`
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`
`
`extrusion.
`
`U.S. Pat. No. 4,436,679 discloses a method of making
`
`
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`
`
`
`foam wherein water and natural gas are introduced into a
`
`
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`
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`melt.
`
`U.S. Pat. No. 4,470,938 discloses a method of utilizing
`
`
`
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`
`
`
`atmospheric gases for forming thermoformed articles
`
`
`
`
`
`
`wherein the process includes introducing, to a molten resin
`
`
`
`
`
`
`
`charge under pressure, a gas blowing agent from a supply
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`gas source of comparatively higher pressure, said introduc-
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`ing being by means of discrete uniform volumetric charges
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`of gas into said resin, wherein said discrete volumetric
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`PAGE 5 OF 11
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`PAGE 5 OF 11
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`

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`5,925,450
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`
`3
`pumped to an accumulator and thereafter to a mass flow
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`meter and control valve for injection into the plastic material
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`downstream of the point of injection of the atmospheric gas.
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`Alternatively,
`the blending agent can be mixed with the
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`atmospheric gas in a static mixer and injected at a single
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`point of injection. The blended material then passes to the
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`secondary conditioning or cooling extruder and is extruded
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`in the form of a tubular web that is preferably cooled from
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`the inside and outside.
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`Referring to FIG. 2, in a preferred form of the invention,
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`the internal cooling mandrel M onto which the tubular
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`material is passed is located relative to the extruder die D
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`such that the frustoconical web W forms an angle Awith the
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`axis of the extruder that is preferably greater than 45° and
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`ranges between 45° and 90°. In addition, the cooling air is
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`supplied to the exterior of the tubular web closely adjacent
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`the extruder die lip and is caused to flow parallel to the web
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`W. Specifically,
`the air is supplied at an acute angle B
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`tangentially of the web W as it is expanded outwardly to cool
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`the external surface of the web W. This flow of air causes
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`additional ambient air to be drawn to supplement the air
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`being supplied for maximum cooling by turbulent flow.
`Cooling of the web and moving the web at an angle greater
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`than 45° minimize and substantially eliminate axially
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`extending corrugations which occur in making foam mate-
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`rials with atmospheric gases.
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`In the form of the invention shown in FIG. 4, in addition
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`to the arrangement in FIG. 2, there is provided a tapered
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`cooling ring R adjacent the front of the cooling mandrel. The
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`ring R is cooled by lines L and includes annular recesses R1
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`and R2 that are connected by a line P to a vent valve V to the
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`atmosphere. As the web W contacts and passes over the
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`tapered cooling ring R, which is maintained at a temperature
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`independent of that of the mandrel M, further cooling of the
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`web occurs at a smaller diameter than that of the mandrel.
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`As the web cools, a force is required to pull and stretch the
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`web over the tapered cooling ring creating a tension between
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`the mandrel M and the conventionally used pull rollers. The
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`provision of the annular recesses R1, R2 being vented
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`through a vent port produces a partial vacuum as the web
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`moves across in contact with the cooling ring R maintaining
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`the web in good contact with the cooling ring R. By use of
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`the valve,
`the degree of venting can be increased or
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`decreased such that the degree of vacuum can be increased
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`or decreased.
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`It has been found that utilizing a percentage of atmo-
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`spheric gas by weight of less than 3% by weight produces
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`satisfactory results.
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`It has been found that when a non-volatile blending agent
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`such as an ester is also used, the method permits the ready
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`processing of the polystyrene melt by cooling without high
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`loading on the extruder and so that the blowing agent is
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`substantially entirely released upon extrusion of the foam.
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`The resultant product has controlled rate of shrinkage with-
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`out change in aging, cell size, opacity, stiffness, smoothness,
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`caliper, density, low cost, but most important environmen-
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`tally acceptable.
`As used herein, the non-volatile blending agent comprises
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`a high molecular weight agent which is non-volatile at the
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`extrusion temperatures such as 300-325° F. The molecular
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`weight of the non-volatile blending agent preferably ranges
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`between 350 and 450. Non-volatile blending agents which
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`have produced satisfactory results comprise diisodecyl
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`adipate, ditridecyl adipate and trioctyl trimellitate.
`The aforementioned non-volatile blending agents can be
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`used alone or in blends or mixtures for control and adjust-
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`ment of viscosity.
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`PAGE 6 OF 11
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`4
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`include a nucleating
`The thermoplastic material must
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`agent such as sodium bicarbonate and citric acid, as is well
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`known in the art.
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`For use in extruding a polystyrene foam sheet which has
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`functional properties suitable for use in application by
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`shrinkage from a formed sleeve to conform to the contour
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`shape of a container to perform as a label,
`the method
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`comprises utilizing other atmospheric gases such as carbon
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`dioxide, nitrogen or air as the sole and exclusive blowing
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`agent for producing said foam sheet. The method preferably
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`incorporates the injection of the high molecular weight
`non-volatile blending agent having very low volatility at
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`extrudate temperatures (e.g., 300° F.-325°
`into the poly-
`mer melt. Such material provides a solvating action weak-
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`ening intermolecular bonding of the polymer and reducing
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`melt viscosity. Preferably, directly downstream following
`the injection of the organic fluid, air (carbon dioxide, nitro-
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`gen or air, or blends thereof) after having been compressed
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`in excess of extruder injection point pressure (typically, in
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`excess of 3000 PSI), is injected through a second injection
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`port into the polymer.
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`As indicated in FIG. 1, the extrusion equipment used may
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`be a conventional tandem system employing two extruders
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`working in conjunction with each other whereby the first
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`extruder melts the polymer mixed with nucleating agent,
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`which accepts by injection and mixes in a blowing agent and
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`transfers said mix to a second extruder which cools the melt
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`and conveys it into an annular die which transforms the
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`melted mass into a continuous sheet foam.
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`No extrusion equipment modifications such as screw
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`designs, die designs, or special mixing devices are neces-
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`sary. Standard type pumps as suitable for organic fluids and
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`as suitable for boostering industrial type gas pressure with
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`appropriate metering devices which are known to those
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`skilled in the art are the only equipment changes by addition
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`or modification.
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`In the past, CFCs (chlorofiuorocarbons) or HCFCs
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`(hydrochlorofiuorocarbons) and alkanes (usually pentane or
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`isopentane) were commonly used as blowing agents in the
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`industry to produce polystyrene foam sheet which is con-
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`verted into a variety of products such as disposable cups,
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`meat trays, egg cartons, etc. Such fiuorocarbons and alkanes
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`are partially soluble in polystyrene hence reducing the melt
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`viscosity and permitting process cooling of the extruder melt
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`without creation of high load or power demand on the
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`extruder drive motor.
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`The use of blowing agents such as atmospheric type inert
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`gases (carbon dioxide, nitrogen, air) create two significant
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`differences compared to CFCs, HFCs or alkanes:
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`(1) The amount (usage) of blowing agent
`is greatly
`reduced. For example, the following table illustrates
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`approximate comparative amounts of blowing agent
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`needed to produce a label type foam in the caliper range
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`of 5-12 mils having a density area around 12-20 PCF:
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`TABLE 1
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`Usage %
`
`5-7
`3-5
`
`
`3-5
`
`1-3
`1-2
`
`.5-1
`
`
`.5-1
`
`
`Blowing Agent
`
`Freon 11
`Freon 12
`
`
`Pentane/Isopentane
`Freon 22
`Carbon dioxide
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`Air
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`
`Nitrogen
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`PAGE 6 OF 11
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`

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`5,925,450
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`6
`importance on the shrinkage rate and on-set of shrinkage
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`temperature in order to obtain a smooth conformance of the
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`foam to the contour of the container shape without wrin-
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`kling. Use of a volatile blowing agent presents a variable in
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`shrinkage properties so that consistent label application may
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`not be achieved in order to obtain a smooth conformance
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`with the container. Also, in some cases the increased need
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`for heat to shrink leads to a blistering effect on the printed
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`label surface diminishing the aesthetic appearance of the
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`label.
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`The present method utilizes atmospheric gases (including
`air, nitrogen, carbon dioxide or mixtures thereof) and pref-
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`erably contemplates injecting into the melt a non-agent
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`volatile blending agent such as a high molecular weight ester
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`having excellent stability to heat whereby it is resistant to
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`decomposition with heat and within practical purposes can
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`be considered as nonvolatile in the application process of
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`polystyrene foam extrusion. While the number of non-
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`volatile blending agents meeting such criteria is limited,
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`ditridecyl adipate and trioctyl trimellitate or blends thereof
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`for viscosity adjustment have successfully been utilized,
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`diisodecyl adipate being considered marginally acceptable
`for inclusion to the list due to a slightly higher tendency to
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`volatilize with heat exposure.
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`Organic materials were evaluated in the laboratory by
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`exposing them to conditions more extreme than encountered
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`in extrusion. Each material was placed in a wide mouth open
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`cup and held at a temperature of 155° C. with measurement
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`of volatile loss at different time intervals. Data on the three
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`liquid blending agents above were as follows:
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`TABLE 4
`
`
`Name
`
`
`Diisodecyl Adipate
`
`
`Ditridecyl Adipate
`
`
`Trioctyl Trimellitate
`
`
`
`
`Molecular
`
`
`
`Weight
`
`
`
`427
`510
`550
`
`
`
`
`
`% Volatility @ 155° C.
`
`
`After 2 hours
`24 hours
`
`
`0.3
`6.0
`0.2
`2.8
`0.6
`1.5
`
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`Examples of materials which did not meet the acceptable
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`criteria for use are illustrated as follows:
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`TABLE 5
`
`
`Molecular
`
`
`
`Weight
`
`
`
`373
`316
`303
`430
`
`
`
`
`
`
`
`
`% Volatility @ 155° C.
`
`
`After 2 hours
`24 hours
`
`
`1.7
`24.1
`
`
`4.3
`60.4
`
`
`97.0
`14.0
`
`
`2.1
`27.5
`
`
`
`
`
`Name
`
`
`Diisodecyl Adipate
`
`Dibutyl Sebacate
`
`
`Diisobutyl Azelate
`
`Triethylene
`
`Glycolcaprate-
`
`caprylate
`
`
`
`
`
`
`The embodiment of the invention wherein the method
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`includes injecting a non-volatile blending agent having
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`highly selective heat resistance to decomposition and vola-
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`tility while using an atmospheric type gas for the blowing
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`agent can include a valving arrangement whereby the two
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`materials are premixed and injected in the same port or the
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`materials are injected into separate ports if the extruder is so
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`equipped with two individual ports. No special mixing
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`devices are necessary and no extruder screw modifications
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`
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`are needed. As known by those familiar with the art, a pump
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`adequate for handling the liquid non-volatile blending agent
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`and a pump for pumping atmospheric gas capable of build-
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`10
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`15
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`20
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`25
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`30
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`35
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`40
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`45
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`50
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`55
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`60
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`65
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`
`5
`
`It can be seen that carbon dioxide is effective in a much
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`lower amount than prior blowing agents for comparable
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`densities. With nitrogen and air, even lesser amounts are
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`needed.
`
`(2) Inasmuch as the atmospheric gases are relatively
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`
`insoluble in the polystyrene, the resultant foam material
`
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`can be stored and used at various times without any
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`
`substantial change in the properties thereof including
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`
`
`the shrinkage properties.
`This may be contrasted to fluorocarbons and alkanes
`
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`
`
`
`which are soluble in polystyrene and reduce the melt vis-
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`
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`
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`cosity enabling the extruder to convey or advance the
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`material at lower power loads with considerable latitude to
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`
`cool the melt to around 300° F. before exiting from the die
`
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`as necessary to generate good smooth foam without ruptured
`
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`cells and obtain other foam sheet physical properties such
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`shrinkage characteristics and stiffness. Due to the solubility
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`
`of the CFCs and alkanes approximately half or greater of the
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`amount of these type materials injected remains dissolved in
`
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`
`
`the polystyrene after emerging from the die. These materials
`
`
`
`
`
`
`
`
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`are volatile and will gradually evaporate from the sheet with
`
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`
`
`
`
`
`
`
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`age over a period of months. Label stock intended for
`
`
`
`
`
`
`
`
`
`application onto a container or bottle by use of shrinkage
`
`
`
`
`
`
`
`
`
`obviously requires that shrinkage properties be a part of the
`
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`
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`sheet characteristics. The CFCs and alkanes act as plasti-
`
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`
`
`
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`
`
`
`cizers in polystyrene lowering the Tg of the polymer and
`
`
`
`
`
`
`
`
`
`enhancing shrinkage upon application of sufficient heat. The
`
`
`
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`
`
`
`amount of shrinkage and the temperature at which shrinkage
`
`
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`
`
`
`will start is dependent upon how much residual CFC or
`
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`
`
`
`alkane is present in the sheet.
`
`
`
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`The following data illustrates the effect of temperature on
`
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`shrinkage of a sheet containing 2% residual fluorocarbon.
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`Sample used was 7 mil caliper with 20 PCF density:
`
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`
`
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`
`
`Temperature
`
`200° F.
`210° F.
`
`
`220° F.
`230° F.
`
`240° F.
`
`250° F.
`
`
`
`TABLE 2
`
`% Machine Direction Shrinkage
`
`
`
`6.0
`14.0
`
`
`45.0
`55.0
`
`60.0
`
`62.0
`
`
`
`
`
`However, as stated fluorocarbon are volatile at room
`
`
`
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`
`
`temperature and the amount of fluorocarbon will gradually
`
`
`
`
`
`
`
`decrease with age. Rate of loss is obviously dependent upon
`
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`
`
`
`storage conditions, whether in roll form, width of web, etc.
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`
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`
`
`In an accelerated lab test with a sample sheet, exposed for
`
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`
`
`
`test purposes the shrinkage rate of loss is illustrated as
`
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`
`
`
`
`follows using 210° F. to simplify data:
`
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`
`TABLE 3
`
`% Machine Direction Shrinkage
`
`
`
`@210° F.
`
`14.0
`10.0
`9.0
`8.0
`7.0
`6.0
`
`
`
`Aging Period (weeks)
`
`
`
`
`
`UI-BU-)l\)>—*©
`
`In a process where foam labels are applied by shrinkage
`
`
`
`
`
`
`
`
`onto a container or bottle, high applicating speeds such as
`
`
`
`
`
`
`
`500-1000 units/minute are used. This places significant
`
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`
`PAGE 7 OF 11
`
`PAGE 7 OF 11
`
`

`
`5,925,450
`
`
`
`8
`
`
`
`TABLE 8
`
`
`7
`
`ing the pressure to the area of 3000-4000 PSI to permit
`
`
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`
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`
`
`
`
`injection into the extruder is necessary. Accordingly, a
`
`
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`
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`metering system appropriate for use with each material is
`
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`
`
`
`required to control the usage rate.
`
`
`
`
`
`The method of the present invention is especially advan-
`
`
`
`
`
`
`
`tageous for making foam material to be used in fabricating
`
`
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`
`
`
`structures where a foam sheet must be shrunk. Labels as well
`
`
`
`
`
`
`
`
`as disposable cups are well known examples of such appli-
`
`
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`
`
`
`
`
`
`cations. Sheet material for both of these type applications
`
`
`
`
`
`
`
`
`have been produced within the embodiment of this invention
`
`
`
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`
`
`
`
`with corresponding conversion to end use products. In label
`
`
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`
`
`
`
`stock with a caliper use range of 5-12 mils and density area
`
`
`
`
`
`
`
`
`
`
`of 18-22 PCF, a usage rate of non-volatile blending agent of
`
`
`
`
`
`
`
`
`approximatley 1.0% of the foam weight has been preferred.
`
`
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`
`
`
`
`
`For cup stock in the caliper range of 16-22 mils and density
`
`
`
`
`
`
`
`
`
`
`area of 12-14 PCF, a usage rate of 2.0% of the foam weight
`
`
`
`
`
`
`
`
`
`has been successful.
`
`
`
`To evaluate the benefit of the non-volatile blending agent,
`
`
`
`
`
`
`
`
`the following data was determined from tests on motor load
`
`
`
`
`
`
`
`
`
`measured by amperage and melt temperature at entry into
`
`
`
`
`
`
`
`the die. Ditridecyl adipate was used as the non-volatile
`
`
`
`
`
`
`
`
`
`
`
`blending agent:
`
`TABLE 6
`
`
`Amount
`
`Blending Agent
`
`
`
`Cooling
`
`Amperage
`
`
`0
`
`1.5
`
`0
`1.5
`
`
`
`119
`
`93
`
`105
`95
`
`
`
`Melt Temp.
`
`
`of
`
`318
`
`318
`
`329
`322
`
`
`
`Blowing Agent
`
`
`Nitrogen
`
`Nitrogen
`
`Carbon dioxide
`Carbon dioxide
`
`
`
`
`
`the addition of the blending agent
`As can be seen,
`
`
`
`
`
`
`
`
`
`
`functions to reduce the amperage required to maintain the
`
`
`
`
`
`
`
`same or lower melt temperature.
`
`
`
`
`Another advantage of use of the non-volatile blending
`
`
`
`
`
`
`
`
`agent is that it will lower the Tg of the polymer and hence
`
`
`
`
`
`
`
`
`
`enhance onset of shrinkage at lower temperatures of the
`
`
`
`
`
`
`
`
`foam upon application of heat as previously indicated as
`
`
`
`
`
`
`
`
`
`needed in certain industrial applications. The relative effect
`
`
`
`
`
`
`
`of the concentration of the use of blending agent is indicated
`
`
`
`
`
`
`
`
`by the following data:
`
`
`
`
`
`
`
`TABLE 7
`
`Machine direction percent shrinkage * where
`
`
`
`
`the organic fluid is diisodecyl adipate.
`
`
`
`
`
`% Blending Agent
`@200° F.
`@210° F.
`@220° F.
`
`
`
`
`
`
`3.4
`5.0
`0
`23.0
`0.5
`3.9
`7.8
`32.0
`
`
`
`
`4.9
`1.0
`15.0
`41.0
`
`
`
`
`6.6
`1.5
`16.5
`48.5
`
`
`
`
`11.5
`2.0
`18.1
`