United States Patent
`Rivera et al.
`
`
`
`
`
`[19]
`
`1llllllllllllllll||||l||l|||l|||||ll|lllll|lll|||l|||l||l|l||||||l|l|||||||
`
`
`US005895614A
`
`
`
`
`[11] Patent Number:
`
`
`
`[45] Date of Patent:
`
`5,895,614
`
`
`Apr. 20, 1999
`
`
`
`
`
`'
`
`4,572,740
`
`
`
`............................. 264/50
`
`
`
`
`
`
`.
`
`.
`
`
`
`
`
`
`2/1986 Kretzschmann et al. .
`
`
`
`
`
`
`13$ -
`
`
`
`
`416327027
`9/1937 P -
`
`
`43 293
`2/1989 Aklyama ct 31'
`
`
`
`4,931,434
`6/1990 Broom eta]. .
`4,946,871
`8/1990 B1:1chtaeta1..
`
`
`
`
`4,959,397
`9/1990 B ' hta ta]. .
`
`
`
`
`5,059,631
`10,1991 H1333 efal_ _
`
`
`
`
`5,039,533
`2/1992 Park.
`
`
`
`5,098,782
`3/1992 Hovis et al. .
`
`
`
`
`
`
`
`
`l()Io1t‘1i);et a1.
`,
`.
`OI]
`
`
`
`5,208,266
`5/1993 Yamazaki .
`
`
`
`
`
`
`5,225,451
`7/1993 Rogers et al.
`5246.975
`9/1993 Pontifi-
`
`
`
`5,290,822
`3/1994 Rogers et al.
`
`
`
`5,340,340
`3/1994 Park et al.
`.
`
`
`
`
`
`
`
`5/343/453
`9/1994 P0395-
`S,348,984
`9/1994 Lee .
`
`
`
`5,366,675
`11/1994 Needham.
`
`
`
`
`
`
`,
`,
`31‘
`.
`
`
`
`5,411,684
`5/1995 Tusim at al’ .
`
`
`
`
`
`
`
`
`6/1995 Lee .
`5,428,093
`
`
`
`Examiner—Allan R. KUhHS
`Attomey, Agent, or Fir/n~—Arnold White & Durkee
`
`
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`
`
`
`
`
`
`
`[75]
`
`[54] METHOD OF FORMING A
`
`
`
`
`
`MICROCELLULAR FOAM PLANK
`
`
`
`
`
`Inventors: Patricia J. Rivera. Cambridge. Mass.;
`Lisa A. Nickerson. Lake George; Kim
`
`
`
`
`
`A B1 Queensbuly both of N Y
`
`
`
`
`
`y‘
`'
`'
`'
`'
`,
`_
`,
`
`
`
`
`
`
`[73] Assigneez Tenneco Protective Packaging Inc.,
`
`
`
`Glens Fa11S~ N-Y~
`
`
`
`
`
`[21] App}. No_; 03/599,733
`
`
`
`
`
`[22] Filed:
`Aug. 20, 1996
`
`
`
`
`Related US. Application Data
`
`
`
`[Xx ,
`[60]
`
`
`Provisional application No. 60/002,624, Aug. 22, 1995.
`
`
`
`
`
`
`
`Int. Cl.° ............................ B29C 44/20; B29C 44/46
`[51]
`
`
`
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`
`
`[52] U.S. C1.
`.................................. 264/50: 264/51; 264/53
`
`
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`-
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`
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`
`
`[53] Field of Search ................................... 264/51. 53. 50
`[56]
`References Cited
`
`
`
`
`
`
`............................ S21/95
`
`
`
`
`
`
`
`................. 428/159
`
`IS.
`
`
`U
`2/1972 Cronin .
`3,644,230
`
`
`
`3,766,099 10/1973 Kawai et al.
`.
`
`
`
`
`6/1976 Ifleiner et a].
`3,966,651
`
`
`
`
`4,101,467
`7/1978 Pad: 6, 81 ‘
`
`
`
`
`4,110,259
`3/1973 Eh‘-enfl-eund _
`
`
`
`4,129,530 12/1973 P311; en a]_ .
`
`
`
`
`4,214,054
`7/1980 Watanabe et al. .
`
`
`
`
`3/1930 K0m01i -
`42171319
`
`
`
`
`
`
`
`4,251,584
`2/1981 Van lingelen et a].
`
`
`
`11‘; §°]1“15 ~ ml
`,
`,
`.
`.
`eywang e
`
`
`
`
`.
`4,387,169
`6/1983 Zabmcki et 31.
`
`
`
`
`.
`4,473,665
`9/1984 Martini-Vvedensky et a1.
`
`
`
`
`6/1985 Kobayashi et al.
`....................... 521/59
`4,525,486
`
`
`
`
`
`
`[57]
`
`ABSTRACT
`
`_
`_
`_
`,
`_
`
`
`
`
`
`Blendedlplon-'c1;ossl11;ked p31y01§§1ncf0£ll]p0S1UODSfi whiclfi 1:
`processa e 1|] 0 a oame pr
`ne-ce 1:
`aving a
`u
`
`
`
`
`
`
`structure, including a polyolefin. optionally a copolymer of
`
`
`
`
`
`an olefin and a different ethylenic monomer. and effective
`
`
`
`
`
`
`
`
`amount of a fatty acid compound permeability control agent.
`
`
`
`
`
`
`
`and an gffectjve amount of a nucleating agent. Aprocess of
`
`
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`
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`
`
`
`
`
`
`
`
`preparing fine—ce1led foam products from the blended
`-
`-
`_
`
`
`
`
`
`
`
`composition. and the final fine celled foam products.
`
`
`
`22 Claims, No Drawings
`
`
`
`
`
`PAGE 1 OF 6
`
`BOREALIS EXHIBIT 1011
`
`BOREALIS EXHIBIT 1011
`
`PAGE 1 OF 6
`
`

`
`1
`
`METHOD OF FORMING A
`
`
`MICROCELLULAR FOAM PLANK
`
`
`
`
`
`5,895,614
`
`
`
`
`2
`foam. which offers crosslinked foam product. with a finer
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
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`
`
`cell count typically greater than 50 cells per inch and a soft.
`non-abrasive feel while also providing capability to be
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`recycled. whereas crosslinked foam does not. The process
`includes forming a mixture of a polyolefin. optionally a
`
`
`
`
`
`
`
`
`
`
`
`
`copolymer of an olefin and a different ethylenic monomer.
`an effective amount of a fatty acid compound permeability
`
`
`
`
`
`
`
`agent. an effective amount of a nucleating agent and an
`
`
`
`
`
`
`
`effective amount of isobutane blowing agent. dissolved in
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`the polyolefin and copolymer. under pressure. The mixture
`has a temperature at which the viscosity of the mixture is
`
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`
`
`suflicient to retain the blowing agent when the mixture is
`
`
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`
`
`allowed to expand The mixture is extruded into a holding
`zone maintained at a temperature and pressure which does
`
`
`
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`
`
`
`not allow the resulting mixture to foam. The extrusion is
`
`
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`
`
`done without an extrusion die. The holding zone has an
`
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`outlet die defining an orifice opening into a zone of lower
`
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`
`
`pressure at which the mixture foams. An openable gate
`
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`closes the die orifice and periodically the gate is opened and
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`substantially concurrently therewith mechanical pressure is
`applied by a movable ram of the mixture to eject the mixture
`
`
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`
`
`
`from the holding zone through the die orifice into the zone
`
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`
`
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`
`
`of lower pressure. at a rate greater than that at which
`
`
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`
`substantial foaming in the die orifice occurs and less than
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`
`that at which substantial irregularities in cross-sectional area
`
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`
`
`or shape occurs. The ejected mixture is permitted to expand
`unrestrained in at least one dimension to produce an elon-
`
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`
`
`
`
`
`gated cellular body.
`In the invention process. using the accumulator process
`
`
`
`
`
`
`
`described in U.S. Pat. No. 4.323.528. flat fine-celled closed
`
`
`
`
`
`
`
`plank structures can be produced
`
`
`
`
`The invention further involves an expanded non-
`
`
`
`
`
`
`
`crosslinked low or high density polyolefin foam having a
`
`
`
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`
`
`
`fine-celled closed structure. which is prepared by the inven-
`
`
`
`
`
`
`
`tion process.
`
`
`The invention foam is a plank foam with dimensions of
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`typically 108 inches by 24 inches by 2 inches (or 3 inches).
`The invention foam will replace bun stock crosslinked foam.
`
`
`
`
`
`
`
`
`
`Manufacturers of such crosslinked foam include Sentinel.
`
`
`
`
`
`
`Voltek. and Monarch Rubber Company. The invention foam
`
`
`
`
`
`
`
`
`is a fine—cell (microcellular). soft material. The invention
`
`
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`
`
`
`foam is preferably made with low density polyethylene.
`
`
`
`
`
`
`
`ethylene vinyl acetate or ethylene methyl acrylate. isobutane
`blowing agent. a fatty acid (glycerol monostearate) to pre-
`
`
`
`
`
`
`
`vent collapse of the foam. and a nucleating agent. for
`
`
`
`
`
`
`
`
`
`example. crystalline silica or sodium bicarbonate-citric acid
`
`
`
`
`
`
`or tale. The invention non-crosslinked foam compares favor-
`
`
`
`
`
`
`
`
`ably to many of the physical characteristics of a crosslinked
`
`
`
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`
`
`foam. However. unlike crosslinked foam. the invention foam
`
`
`
`
`
`
`
`
`is recyclable.
`
`
`DETAILED DESCRIPTION OF THE
`
`
`INVENTION
`
`
`
`
`
`
`
`The invention involves non-crosslinked polyolefin foam
`
`
`
`
`
`
`which offers the properties of a crosslinked product with
`
`
`
`
`
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`
`
`fine-celled (microcellular) structure with cell counts typi-
`
`
`
`
`
`
`
`cally greater than 50 cells per inch and a soft. non-abrasive
`
`
`
`
`
`
`
`
`
`feel while also providing capability to be recycled (whereas
`
`
`
`
`
`
`
`crosslinked foam does not).
`
`
`
`
`The foamed product
`is prepared from a blend of a
`
`
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`
`
`
`
`polyolefin and a copolymer of an olefin and a different
`
`
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`
`(nonionic) ethylenic monomer. Preferably the polyolefin is a
`
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`
`
`low density ethylene homopolymer. Preferably the copoly-
`mer is an ethylene vinyl acetate copolymer or an ethylene
`
`
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`
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`methyl acrylate copolymer. The copolymers are usually soft
`or have low stijfness.
`
`
`
`
`
`
`
`
`
`10
`
`15
`
`20
`
`25
`
`
`30
`
`
`
`
`35
`
`
`40
`
`45
`
`
`50
`
`55
`
`
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`
`
`
`
`
`
`This application claims the benefits of U.S. Provisional
`
`
`
`
`
`
`Application 60/002.624 filed Aug. 22. 1995.
`BACKGROUND OF THE INVENTION
`
`
`1. Field of the Invention
`
`
`
`
`The invention relates to non-crosslinked low or high
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`density polyolefin foam having a fine-celled closed structure
`and a process of preparing the low or high density polyolefin
`
`
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`
`
`foam.
`
`2. Background Art
`
`
`
`Non-crosslinked foams in the prior art made with the
`
`
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`
`
`
`
`
`herein described extrusion accumulator process typically
`
`
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`
`
`
`had cells within the 20 to 30 cells per inch range. Attempts
`
`
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`
`
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`
`
`to make the non-crosslinked thick cross-sectional foams
`
`
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`
`
`with a higher cell count resulted in non-flat/wavy foam.
`
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`voids. ripples. or the like.
`
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`
`
`BROAD DESCRIPTION OF THE INVENTION
`
`
`
`
`The main objectives of the invention is to cure the
`
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`problems of the above stated prior art and to provide a
`non-crosslinked foam product. which offers the properties of
`
`
`
`
`
`
`
`a crosslinked foam product. but with a finer cell count
`
`
`
`
`
`
`
`
`
`typically greater than 50 cells per inch and a soft. non-
`
`
`
`
`
`
`
`
`
`
`abrasive feel while providing capability to be recycled.
`
`
`
`
`
`
`
`
`which is extrinsic to a crosslinked foam product. Other
`
`
`
`
`
`
`
`objectives and advantages of the invention are set out herein
`
`
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`
`
`
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`
`
`or are obvious herefrom to one skilled in the art.
`
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`The objectives and advantages of the invention are
`
`
`
`
`
`
`
`achieved by the compositions. foams and processes of the
`
`
`
`
`
`
`invention.
`
`The invention involves a blended non-crosslinked poly-
`
`
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`
`
`
`olefin composition which is processable into a foamed
`
`
`
`
`
`
`
`
`
`
`
`
`product. preferably foamed plank. comprising a polyolefin.
`optionally a copolymer of an olefin and a diiferent ethylenic
`
`
`
`
`
`
`monomer. an effective amount of a fatty acid compound
`
`
`
`
`
`
`permeability agent. and an effective amount of a nucleating
`
`
`
`
`
`
`
`
`
`
`
`
`
`agent. The non-crosslinked foamed product of the invention
`offers the properties of a crosslinked foam product and has
`
`
`
`
`
`
`
`
`a finer cell count typically greater than 50 cells per inch and
`
`
`
`
`
`
`
`
`
`
`
`a soft. nonabrasive feel. The non-crosslinked foamed prod-
`
`
`
`
`
`
`
`
`uct has the capability of being recycled. which is extrinsic to
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`a crosslinked foamed product. To improve the softness of the
`
`
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`
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`foam product. the optional copolymer is a copolymer of an
`
`
`
`
`
`
`olefin and an ester monomer. To improve the strength and/or
`
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`
`
`
`
`
`stiffness of the foam product. an ionomer resin can be
`
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`
`included in the blend. Isobutane blowing agent is also
`
`
`
`
`
`
`
`usually present in an amount of from 5 to 30 parts. best from
`
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`
`10 to 20 parts. per 100 parts of the polymer blend compo-
`
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`
`
`sition during the operation/process of preparing the foam.
`
`
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`
`
`Preferably the polyolefin is polyethylene. Preferably the
`copolymer is ethylene vinyl acetate copolymer or ethylene
`
`
`
`
`
`
`methyl acrylate copolymer. Preferably the fatty acid com-
`
`
`
`
`
`
`
`
`pound stability agent is glycerol monostearate. Preferably
`
`
`
`
`
`
`the nucleating agent is (a) crystalline silica. or (b) sodium
`
`
`
`
`
`
`
`
`
`bicarbonate-citric acid. or (c) talc.
`
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`
`
`In the most preferred blended polymer composition the
`
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`polyolefin is low density polyethylene. the copolymer is
`
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`
`
`ethylene methyl acrylate copolymer. the fatty acid com-
`
`
`
`
`
`
`pound permeability control agent is glycerol monostearate
`and the nucleating agent is crystalline silica.
`
`
`
`
`
`
`The invention also involves a process for preparing an
`
`
`
`
`
`
`
`
`
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`
`
`expanded non-crosslinked low or high density polyolefin
`
`65
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`
`PAGE 2 OF 6
`
`PAGE 2 OF 6
`
`

`
`
`3
`
`
`
`
`
`
`Examples of the thermoplastic polyolefins are polyethyl-
`enes and polypropylenes. The polyethylenes can be HDPE,
`
`
`
`
`
`
`
`MDPE. LDPE and LLDPE.
`
`
`
`Examples of the ethylene copolymers are ethylene vinyl
`
`
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`
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`
`
`
`acetate copolymers. ethylene-1-butene copolymers. ethyl-
`ene methyl acrylate copolymers. ethylene-acrylic acid
`
`
`
`
`
`
`copolymers. and the like.
`
`
`
`
`The amount of the polyolefin in the polymer blend
`
`
`
`
`
`
`
`
`
`typically is 5 to 95 percent. preferably about 85 percent
`
`
`
`
`
`
`
`based on the total weight of the polymer blend composition
`
`
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`
`
`
`(excluding the blowing agent).
`The amount of the copolymer of an olefin and a different
`
`
`
`
`
`
`
`ethylenic monomer in the polymer blend typically is 5 to 25
`
`
`
`
`
`
`percent. preferably about 12 percent. based on me total
`
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`
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`
`
`
`weight of the polymer blend composition (excluding the
`
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`
`
`
`
`blowing agent). In the copolymer. the different ethylenic
`monomer is preferably used in the amount of about 5 to 20
`
`
`
`
`
`
`percent. based on the total weight of the copolymer.
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`To improve softness. copolymers containing esters. such
`as. ethylene methyl acrylate (EMA) or ethylene vinyl acetate
`
`
`
`
`
`
`
`
`(EVA). can be added to the mixture with a total ester
`
`
`
`
`
`
`
`
`
`monomer content of the final product (or the polymer
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`blended composition. excluding the blowing agent) in the
`range of up to 20 percent. preferably about 2.4 percent. to
`
`
`
`
`
`
`
`allow best control of the process.
`
`
`
`
`
`
`The melt indices for some of the preferred components of
`
`
`
`
`
`
`
`
`the invention blends are:
`
`
`
`
`
`Material
`
`EMA
`
`EVA (UE 630)
`
`
`PE
`
`
`
`
`Melt Index (g1nsl10 min.)
`
`
`
`2.0
`
`1.8
`
`1.8-2.2
`
`
`A fatty acid compound permeability control agent
`is
`
`
`
`
`
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`added to the polymer blend composition to enhance dimen-
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`sional stability in the foam product. Preferred fatty acid
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`permeability control agents include amides and esters of
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`Cl2_24 fatty acids. Such permeability control agents are
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`taught in U.S. Pat. Nos. 3.644.230 and 4.214.054. which are
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`incorporated herein by reference. Preferred individual per-
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`meability control agents include steryl steararnide. glycerol
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`monostearate. glycerol monobehenate. and sorbitol
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`monostearate. The most preferred permeability control agent
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`is glycerol monostearate. Typically. such fatty acid com-
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`pound permeability control agents are employed in an
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`amount ranging from about 0.1 to about 5 parts per hundred
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`parts of the polymer blend composition (excluding the
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`blowing agent). or preferably about 1.5 weight percent based
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`on the polymer blend composition (excluding the blowing
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`agent) to prevent foam collapse.
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`The fatty acid compound permeability control agents
`include partial esters of long chain fatty acids with polyols.
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`fatty acid amides. complete esters of fatty acids. etc. Some
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`further examples thereof are glycerol distearate. glyceryl
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`monobenzoate and sorbitan monooleate.
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`The nucleating agent is used to regulate cell size within
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`the foam. The nucleating agent preferably is (a) crystalline
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`silica. or (b) sodium bicarbonate citric acid. or (c) talc. The
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`most preferred nucleating agent is crystalline silica and is
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`typically used in amounts of 10 to 25 percent by weight.
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`most preferably about 13 to 17 weight percent. based upon
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`the weight of the total composition (excluding the blowing
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`agent). The preferred sodium bicarbonate—citric acid nucle-
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`ating agents are commercially available under the trademark
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`HYDROCEROL. The preferred sodium bicarbonate-citric
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`PAGE 3 OF 6
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`5,895,614
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`4
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`acid is Hydrocerol CF-70 or Hydrocerol CF-40 (a
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`particulate/powder of. respectively. a 70 or 40 percent
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`concentration of sodium bicarbonate and citric acid in a wax
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`and polyethylene base in pellet form). The nucleating agent
`is typically used in amounts of from 0.1 to 5 percent by
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`weight. preferably 0.2 to 2 percent by weight. most prefer-
`ably about 0.5 weight percent. based upon the weight of the
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`total composition (excluding the blowing agent).
`In U.S. Pat. No. 4.572.740 (column 3. line 18). it is
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`disclosed that “hydrocerol” nucleating agent is also a blow-
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`ing agent. The melt temperature (i.e.. approximately. 220°
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`F.) of the invention is well below the temperature in U.S. Pat.
`
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`No. 4.572.740. Therefore. the “hydrocerol” nucleating agent
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`is purely a nucleating agent in the invention process.
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`Other nucleating agents. such as. clay. mica. titanium
`
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`oxide. zinc oxide. calcium silicate. and metallic salts of fatty
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`acids such as barium stearate. zinc stearate and aluminum
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`stearate. can be used. Nucleating agents are usually finely
`divided and may be pelletized. encapsulated. and the like.
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`The polymer blend composition can also contain up to 10
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`percent. preferably about 3 percent. based upon the total
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`weight of the polymer blend composition (excluding the
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`blowing agent). of an ionomeric resin. The ionomeric resin
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`is a cation initiated crosslinked polymer of ethylene and a
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`vinyl acid. preferably a zinc or sodium ion initiated
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`crosslinked polymer of ethylene and methacrylic acid. An
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`ionomer is a thermoplastic polymer that
`is ionically
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`crosslinked to form bonds between the acid groups within a
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`chain and neighboring chains. ‘The ionomers improve the
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`strength and/or the stiffness of the microcellular foam
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`planks. In general. ionomers are transparent. resistant to
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`abrasion and solvents. have excellent electrical properties.
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`and have outstanding puncture and low temperature impact
`resistance. Ionomeric resins are recyclable. (Note that the
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`ionomeric resin is not a crosslinking agent regarding the
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`foam of the invention.)
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`The preferred blowing agent used is isobutane. One or
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`more conventional or useful blowing agents can be used.
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`Such other suitable volatile blowing agents include halocar-
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`bons such as fluorocarbons and chlorofluorocarbons; hydro-
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`halocarbons such as hydrofluorocarbons and
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`as.
`hydrochlorofluorocarbons,
`such
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`dichlorotetrafluoroethane. dichlorodifluoroethane. dichlo-
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`romonofluoromethane and trichloromonofluoromethane;
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`alkylhalides. such as methyl chloride and ethyl chloride;
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`hydrocarbons such as alkanes or alkenes; carbon dioxide.
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`nitrogen. argon. water; and the like. Examples of useful
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`alkanes having from 2 to 9 carbon atoms are ethane.
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`propane. butane. pentane. is isopentane. hexane. isohexane.
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`heptane. and the like.
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`The invention foam structure is formed by the extrusion
`
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`accumulator process disclosed in US. Pat. No. 4.323.528.
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`which is incorporated herein by reference. The process for
`
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`producing large size. low or high density. elongated ther-
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`moplastic cellular bodies includes the forming of a mixture
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`of a thermoplastic polymer-copolymer blend composition
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`and the isobutane blowing agent dissolved therein under
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`pressure and at a temperature at which the viscosity of the
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`mixture is sufficient to retain the isobutane blowing agent
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`when the mixture is allowed to expand. The mixture is
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`extruded into a holding zone under conditions that prevent
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`the mixture from foaming. The holding zone has an outlet
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`die orifice opening into a zone of lower pressure and
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`temperature at which the mixture foams. The outlet die
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`orifice must be designed to allow the expansion of the fine
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`celled foam to the appropriate stated width dimensions. An
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`PAGE 3 OF 6
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`5,895,614
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`5
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`openable gate closes the die orifice. Periodically the gate is
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`opened and substantially concurrently mechanical pressure
`is applied by a movable ram on the mixture. preferably while
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`scraping the sides of the holding zone with the ram. to eject
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`the mixture from the holding zone through the die orifice at
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`a rate in excess of that at which substantial foaming in the
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`die orifice occurs and less than that at which substantial
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`irregularities in the cross-sectional area or shape of the
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`cellular body occurs. preferably 9.000 lb/hour to 11.000
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`lb/hour. most preferably the foam ejection rate of 10.500
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`lb/hour. The ejected mixture is permitted to expand unre-
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`strained in at least one dimension to produce the elongated
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`thermoplastic cellular body. The apparatus for producing
`elongated thermoplastic cellular bodies includes an extruder
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`for feeding a mixture of the thermoplastic polymer blend
`and the plasticizing isobutane blowing agent at a tempera-
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`ture suitable for producing a cellular body when the mixture
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`is subjected to lower pressure. and an expandable holding
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`chamber receiving the mixture from the extruder and main-
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`taining the mixture in a molten state at a pressure above the
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`foaming pressure thereof. There is ram means for ejecting
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`the mixture out of the holding chamber. a die having an
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`orifice. preferably in line with the ram means. through which
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`the mixture is ejected from the holding chamber by opera-
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`tion of the ram means. and gate means contacting the
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`exterior surface of the die for closing and sealing the die
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`orifice while the holding chamber is being filled
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`The conditions in the extruder portion of the extrusion-
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`accumulator apparatus for the invention foam typically are:
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`Temperatures: Feed/Metering: 300° to 425°. preferably 320°
`to 400° F. Cooling: 120° to 230° F.. preferably 150° to
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`180° F.
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`Pressures: 600 to 2000 psi. preferably 650 to 1.000 psi.
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`The conditions in the accumulator for the invention foam
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`typically are:
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`Temperatures: 190° to 225° F.. preferably 210° to 221° F.
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`Pressures: 200 to 1.000 psi. preferably 400 to 600 psi.
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`Extruded foam planks with cell size typically of the herein
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`stated invention formed by extrusion using an extruder with
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`an extrusion die. in the case of uncrosslinked PE or PE/EVA.
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`have surface ripples. corrugations. warping and the like. To
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`the contrary. the non—crosslinked PE/EVA or PE/EMA foam
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`planks of the invention. which are formed by the extrusion
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`accumulator system. do not have surface ripples. corruga-
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`tions or warping. The foam planks of the invention have
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`smooth flat surfaces. The invention process produces micro-
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`cellular or fine celled foam structures and planks with cell
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`counts usually within the range of 50 to 120 cpi. ideally
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`greater than 70 cpi. The invention foam planks are substan-
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`tially composed of closed cells.
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`The process and polymer blend compositions of the
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`invention are particularly useful in producing polyolefin
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`foam planks. especially polyethylene foam planks. For
`example. low density polyethylene foam with a density in
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`the range of 1.2 to 2.6 pcf can be produced. The foam has
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`a fine-celled closed structure containing greater than 50 cells
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`per inch. The foam is made in plank form with finished
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`nominal dimensions of 2% inches by 24 inches by 108
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`inches. Using the accumulator process. as described i.r1 U.S.
`
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`Pat. No. 4.323.528. such flat foamed plank structure has
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`10
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`6
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`been produced. Another example is that low density poly-
`ethylene foam planks having the same specifications as the
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`preceding foam planks except that the finished nominal
`dimensions are 3% inches by 24 inches by 108 inches. Foam
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`planks can be made in Varying widths and length. High
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`density polyethylene foam planks having a density of about
`4 pcf or greater can be produced by the invention process
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`and from the invention polymer blend compositions.
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`To accelerate the release of the isobutane blowing agent
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`from the ejected thermoplastic foam. the ejected thermo-
`plastic foam can be subjected to heat below any level having
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`adverse eifect on the thermoplastic foam or can be perfo-
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`rated so as to create a series of narrow channels in and/or
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`through the thermoplastic foam.
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`The invention thermoplastic foams are recyclable in that
`the basic chemical nature of thermoplastic usually does not
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`change significantly as a result of the extrusion process.
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`Thermoplastic materials can generally be reground and
`recycled into a usable form. Thermosets undergo a
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`crosslinking reaction when the temperature is raised above
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`a certain point. The crosslinking forms a three dimensional
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`network which remains intact when the temperature is
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`reduced. This causes an irreversible change in the material
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`and. therefore. can not be recycled like thennoplastic mate-
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`rials.
`
`By way of summary. the product is a polyolefin foam with
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`a density in the range of about 1.2 and about 9.0 pcf. The
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`polyolefin foam planks can be low density. e.g.. density of
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`about 1.2 to about 2.6 pcf. or high density. e.g.. density of
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`about 4.0 to 9.0 pcf. The polyolefin is usually low density
`polyethylene. The foam is made in plank form. e.g.. with
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`nominal dimensions of 24 inchesx 108 inches><2 to 3'/2
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`inches. The foam has a fine-celled structure containing 50 to
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`120 cells per inch (cpi). Using the accumulator process as
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`
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`described in U.S. Pat. No. 4.323.528. the invention process
`
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`is able to produce a flat foamed plank structure. The foam is
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`a non-crosslinked thermoplastic material and is recyclable.
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`unlike crosslinked foam. Like crosslinked foam. the inven-
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`tion foam is smooth to the touch and passes the surface
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`abrasion resistance as required of the packaging of Class A
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`surfaces. This invention foam is physically comparable with
`
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`
`a crosslinked foam product with recyclability as an added
`
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`bonus. The invention foam can be white or colored and can
`
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`also contain additives. such as. UV stabilizers. antistats.
`
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`
`
`pigments. antioxidants. etc. To improve softness. ethylene
`
`
`
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`
`
`copolymers containing esters such as ethylene vinyl acetate
`
`
`
`
`
`
`
`(EVA) or ethylene methyl acrylate (EMA) can be added to
`
`
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`
`
`the LDPE. The total ester monomer content of the final
`
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`product (excluding the blowing agent) is in the range of 0.1
`
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`
`to 10 (or 20) percent. To improve stifiness of the ester
`
`
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`
`
`
`
`
`
`
`modified foam. an ionomeric resin can be added in the range
`
`
`
`
`
`
`
`
`of up to 5 percent [e.g.. 0.01 to 5 (or 10) percent]. The
`
`
`
`
`
`
`
`
`
`invention foam is preferably made with a crystalline silica
`
`
`
`
`
`
`
`nucleating agent or a sodium bicarbonate nucleating agent or
`
`
`
`
`
`
`a talc nucleating agent. and isobutane as the sole blowing
`
`
`
`
`
`
`
`
`
`agent. Glycerol monostearate (most preferred) or a similar
`
`
`
`
`
`
`fatty acid compound can be used as the permeability control
`
`
`
`
`
`
`
`
`agent.
`
`A comparison of prior art cros slinked foam materials with
`
`
`
`
`
`
`invention non—crosslinked foam materials follows:
`
`
`
`
`
`
`MATERIALS
`
`
`Sentinel
`
`MC1900e
`
`
`
`Sentinel
`
`MC1900
`
`
`Inven.
`
`
`Inven.
`
`
`
`Inven.
`
`PEIEVAI
`
`
`
`PAGE 4 OF 6
`
`PAGE 4 OF 6
`
`

`
`
`
`5,895,614
`
`
`
`PEJEVA
`
`2 wk test
`
`2
`
`70-80
`
`6
`
`
`
`19
`
`44
`
`10
`
`<0.05
`
`
`
`<2%
`
`<2%
`
`6%
`
`
`<2%
`
`<2%
`
`<4%
`
`
`Ionomer
`
`4 wk test
`
`
`
`70-80
`8.2
`
`
`
`
`
`15.6
`
`
`
`<2.5%
`6.5%
`<5%
`
`
`
`
`
`
`<2%
`<2.5%
`
`
`
`
`7
`
`xlpe
`
`literature
`
`
`2
`
`169
`
`8.5
`
`
`15
`
`40
`
`
`PFJEMA
`
`2 wk test
`
`2
`
`70-80
`
`7.6
`
`
`
`12.5
`
`
`2
`
`169
`
`4.5
`
`
`20
`
`50
`
`
`8
`
`0.05 max
`
`
`
`
`7
`
`0.05 max
`
`
`
`
`<2%
`
`
`<2%
`
`
`<2%
`
`<2%
`
`<4%
`
`
`6%
`
`6%
`
`6%
`
`
`<2%
`
`<2%
`
`<2%
`
`
`PROPERTIES
`
`
`xlpe/eva
`
`literature
`
`
`
`
`Density
`
`CPI
`
`Comp. Strength
`
`25%
`
`Comp. Sets
`
`
`Tensile
`
`Strength (psi)
`
`
`Tear Resistance
`
`
`(P11)
`
`Water
`
`Absorption (ps)
`
`
`Therm. Stab. %
`
`
`shrink
`
`
`
`CMD
`MD
`
`Thick
`
`Die Cut, %
`
`
`CMD
`
`MD
`
`Thickness
`
`
`
`What is claimed is:
`
`
`1. A process for preparing a non-crosslinked polyolefin
`
`
`
`
`
`
`foam elongated cellular body having a fine-celled closed
`
`
`
`
`
`
`
`structure. said fine-celled structure having a cell count
`
`
`
`
`
`
`
`greater than 50 cells/inch. said process comprising the steps
`
`
`
`
`
`
`
`
`of:
`
`melting a polyolefin and a copolymer of an olefin mono-
`
`
`
`
`
`
`mer and an ethylenic monomer different from the
`
`
`
`
`
`
`
`
`monomer of said polyolefin to form a polymeric blend.
`
`
`
`
`
`
`the amount of said copolymer being in the range of
`
`
`
`
`
`
`
`from 5 to 25 percent by weight of said blend;
`
`
`
`
`
`forming a mixture of said blend. an amount of fatty acid
`
`
`
`
`
`
`
`efiective to provide stability. and an amount of a
`
`
`
`
`
`
`
`nucleating agent suflicient
`to produce a cell count
`
`
`
`
`
`
`
`greater than 50 cells/inch;
`
`
`
`dissolving an efiective amount of a blowing agent in said
`
`
`
`
`
`
`mixture to form a blowing-agent—containing mixture;
`
`
`
`
`then
`
`extruding said blowing—agent-containing mixture into a
`
`
`
`
`
`holding zone;
`
`
`maintaining said holding zone at conditions. including
`
`
`
`
`
`
`temperature and pressure. at which said blowing-agent-
`
`
`
`
`
`
`containing mixture does not foam;
`
`
`
`
`
`transferring said blowing-agent-containing mixture into
`
`
`
`
`
`an expansion zone; and
`
`
`
`
`permitting said blowing-agent-containing mixture to
`
`
`
`
`
`expand in the expansion zone to produce said elongated
`
`
`
`
`
`
`
`cellular body.
`
`
`2. The process of claim 1 wherein said polyolefin is
`
`
`
`
`
`
`
`
`selected from the group consisting of polyethylene and
`
`
`
`
`
`
`
`
`
`polypropylene.
`3. The process of claim 2 wherein said polyethylene is
`
`
`
`
`
`
`
`
`selected from the group consisting of HDPE. MDPE. LDPE
`
`
`
`
`
`
`
`and LLDPE.
`
`
`4. The process of claim 1 wherein said copolymer is
`
`
`
`
`
`
`
`