(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2009/0110855 A1
`McCarthy et al.
`(43) Pub. Date:
`Apr. 30, 2009
`
`US 20090110855A1
`
`(54) FILLED POLYSTYRENE COMPOSITIONS
`AND USES THEREOF
`
`(51) Int- Cl
`
`Publication Classi?cation
`
`(75) Inventors:
`
`Donald C. McCarthy, Appleton,
`WI (US); William Pucci,
`Winneconne, WI (US); Anthony J.
`swl‘mtek’ Neenah’ WI (Us)
`Correspondence Address:
`PATENT GROUP GA030-43
`GEORGIA-PACIFIC LLC
`133 PEACHTREE STREET, NE
`ATLANTA GA 30303-1847 US
`’
`(
`)
`Dixie Consumer Products LLC’
`Atlanta’ G A (Us)
`
`(73) AssigneeZ
`
`(21) App1_ NO;
`
`11/928,280
`
`(22) F?ed;
`
`Oct, 30, 2007
`
`(200601)
`3323 27/08
`(200601)
`B29C 47/04
`(200601)
`3323 9/00
`(52) us. Cl. .................. .. 428/35.7; 264/211.24; 428/339
`
`ABSTRACT
`(57)
`.
`1
`f
`.d
`1
`.
`.
`h
`T e present invention provi es po ymer ormu ations con
`taining 20 to about 40 Weight percent of a ?ller, such as
`calcium carbonate. Multilayer polymer structures containing
`a ?ller in at least one layer of the multilayer structure, and
`methods of making these multilayer structures, are also dis
`closed. Articles of manufacture, such as food service articles,
`including cups, lids, plates, trays, containers, cutlery, and the
`like, derived from these formulations and multilayer struc
`tures are also provided in the present invention.
`
`MULTILAYER PGLYMER STRUCTURE
`
`CAP LAYER
`INNER LAYER
`MISCELLANEOUS LAYER
`CGRE LAYER
`HISCELLANiUUS LAYER
`EJUTER LAYER
`CAP LAYER
`
`Page 1 of 21
`
`BOREALIS EXHIBIT 1074
`
`

`
`Patent Application Publication
`
`Apr. 30, 2009 Sheet 1 0f 5
`
`US 2009/0110855 A1
`
`MULT ILAYER POLYMLR SYRUCTURE
`
`INNER LAYER
`CORE LAYER
`OUKR LAYER
`
`Fig. I
`
`MULT ILAYER POLYMER STRUCTURE
`
`INNER LAYER
`CORE LAYER
`0mm LAYER
`CAP LAYER
`
`Fig. 2
`
`MULULAYER POLYMER STRUCTURE
`
`INNER LAYER
`MESCELLANEOUS LAYER
`90m: LAYER
`MESCELLANEDUS LAYER
`ouYgR LAYgR
`Fig. 3
`
`MULT ILAYER PGLYMER STRUCTURE
`
`CAP LAYER
`ENNER LAYER
`MISCELLANEOUS LAYER
`CURE LAYER
`MISCELLANEOUS LAYER
`OUKR LAYER
`CAP LAYER
`
`Fig. 4
`
`Page 2 of 21
`
`

`
`Patent Application Publication
`
`Apr. 30, 2009 Sheet 2 0f 5
`
`US 2009/0110855 Al
`
`6000
`
`5000
`
`4000
`
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`
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`CALCIUM CARBONATE (PERCENT)
`
`Fig. 5
`
`0 RESiN B
`I RESZN {I
`at? RESiN A
`
`30
`20
`E0
`CALCIUM iIARBONATE (PERCENT)
`
`40
`
`Fig. 6
`
`Page 3 of 21
`
`

`
`Patent Application Publication
`
`Apr. 30, 2009 Sheet 3 0f 5
`
`US 2009/0110855 A1
`
`NNN
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`DEA
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`CALIIIUM EARBONATE (PERCENT )
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`
`Fig. 7
`
`0 RESIN D
`II RESIN E
`ak RESIN A '“
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`CALCIUM CARBONATE (PERC?NT )
`
`30
`
`40
`
`Fig. 8
`
`Page 4 of 21
`
`

`
`Patent Application Publication
`
`Apr. 30, 2009 Sheet 4 0f 5
`
`US 2009/0110855 A1
`
`ill *9 am
`
`0
`
`L . w, I
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`Fig. 8
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`EALCiUM EARBONAT£ (PEREENT)
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`40
`
`Fig. 10
`
`Page 5 of 21
`
`

`
`Patent Application Publication
`
`Apr. 30, 2009 Sheet 5 0f 5
`
`US 2009/0110855 A1
`
`000.000
`
`500.000
`
`A
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`m.
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`Fig. I]
`
`Page 6 of 21
`
`

`
`US 2009/0110855 A1
`
`Apr. 30, 2009
`
`FILLED POLYSTYRENE COMPOSITIONS
`AND USES THEREOF
`
`BACKGROUND OF THE INVENTION
`
`[0001] The present invention relates generally to polymer
`formulations containing a ?ller, and in particular, to multi
`layer polymer structures containing a ?ller in at least one
`layer of the multilayer structure. Articles of manufacture,
`such as food service articles, derived from such formulations
`and structures are also provided in the present invention.
`These food service articles can include cups, lids, plates,
`trays, containers, cutlery, and the like, Which are produced in
`varied polymer processing operations including, for example,
`injection molding, sheet extrusion, and thermoforming.
`[0002] Reducing the cost of polymer formulations, struc
`tures, and end-use articles is continually desired, but not
`easily achieved. The performance properties of the end-use
`article generally must be maintained to ensure ?tness for use
`in the desired application. Such properties can include the
`strength, durability, ?exibility, stiffness, impact resistance,
`and crack resistance of the article. Simply reducing gauge or
`thickness (i.e., doWngauging) usually adversely impacts one
`or more physical properties to the detriment of the doWn
`gauged article, as compared to What is expected of the current
`product in the marketplace and by the consumer.
`[0003] One method to reduce cost is to add an inexpensive
`?ller, such as calcium carbonate, With a cost loWer than that of
`the polymer, to a polymer formulation. Essentially, one dis
`places a more expensive polymer component With a less
`expensive ?ller component at a loading, for example, of 20%
`or more in the polymer formulation or the overall structure.
`[0004] For some polymers, the addition of a ?ller such as
`calcium carbonate can improve certain physical properties of
`the polymer article. In others, such as polystyrene, the addi
`tion of a ?ller is generally disadvantageous for the strength
`properties of the polymer article, as discussed in US. Pat. No.
`4,101,050, the disclosure of Which is incorporated herein by
`reference in its entirety.
`[0005] Additionally, ?llers suitable for use in the present
`invention have a density greater than that of the base polymer
`resin, such as polystyrene. Therefore, increasing ?ller content
`at the expense of the polymer resin content decreases yield,
`i.e., less end-use articles can be produced from a given Weight
`of the ?lled polymer formulation. Furthermore, part Weight
`increases, especially for articles produced in large quantities,
`can dramatically increase other doWnstream costs, such as
`shipping and freight costs.
`[0006] Hence, in order to maintain the yield or the part
`Weight to Within about 10-15% of that of the original un?lled
`polymer article, attempts to doWngauge or reduce sheet or
`Wall thickness are often employed. For formulations With
`polystyrene, such a strategy can further deteriorate the end
`use properties of the ?lled article to a level that is unaccept
`able for that product in the marketplace.
`[0007] Attempts to improve the properties of both ?lled and
`un?lled polystyrene formulations using blends With other
`polymers, such as conventional polyole?ns (e.g., loW density
`polyethylene), are also problematic. Manufacturing pro
`cesses involving the fabrication of polymers into desired end
`use articles generally reclaim Waste, trim, start-up scrap, or
`other similar material in order to maintain economic feasibil
`ity. Hence, the use of dissimilar polymers in an attempt to
`improve the properties of a polystyrene formulation can lead
`to problems in reclaiming and reusing such Waste material.
`
`[0008] Thus, to this point, it has been commercially
`impractical to produce ?lled polystyrene materials for certain
`end-use applications With 20% or greater ?ller content, While
`the ?lled article is thinner in gauge than the current un?lled
`article, yet With the same or improved physical properties.
`Certain ?lled polystyrene formulations and structures have
`been discussed in the prior art and are knoWn to the skilled
`artisan, but these disclosures have failed to address the needs
`or solve the problems noted above, nor provide any speci?c
`guidance in this regard. Accordingly, it is to these ends that
`the present invention is directed.
`
`BRIEF SUMMARY OF THE INVENTION
`
`[0009] The present invention discloses novel multilayer
`polymer structures and methods of making such structures.
`These multilayer polymer structures comprise from 20 to
`about 40 Weight percent of the at least one ?ller. Such struc
`tures can be used to produce a variety of articles of manufac
`ture, such as food services articles, including cups, lids,
`plates, trays, containers, and cutlery.
`[0010] Multilayer polymer structures in accordance With
`the present invention comprise a core layer having a ?rst side
`and a second side, the core layer comprising at least one ?ller;
`an inner layerpositioned on the ?rst side of the core layer; and
`an outer layer positioned on the second side of the core layer.
`Each of the core layer, the inner layer, and the outer layer,
`independently, comprise at least one high impact polystyrene
`(HIPS) polymer. The at least one HIPS polymer has an elas
`tomeric material content of at least about 7 percent by Weight,
`an average particle siZe of the elastomeric material from
`about 1 to about 10 microns, and a mineral oil content of less
`than about 4 percent by Weight. Additionally, the at least one
`HIPS polymer is characterized by a melt ?oW rate of less than
`about 12 and a ?exural modulus from about 200,000 to about
`400,000 psi.
`[0011] These multilayer polymer structures have a unique
`and unexpected combination of stiffness/rigidity properties
`and strength/impact properties. These structures solve an
`unmet need in the marketplace by alloWing an un?lled poly
`styrene-based product or article to be replaced With a ?lled
`structure having 20% or more of at least one ?ller, such as
`calcium carbonate. The resulting ?lled product can be thinner
`in gauge than the incumbent un?lled structure, yet have the
`desired attributes of superior toughness combined With com
`parable or superior rigidity or stiffness.
`[0012] The present invention also provides a method of
`making a multilayer polymer structure, Wherein the multi
`layer polymer structure comprises from 20 to about 40 Weight
`percent of at least one ?ller having a density of greater than
`about 2 g/cc. One such method comprises providing a core
`layer, an inner layer, and an outer layer, and coextruding the
`core layer betWeen the inner layer and the outer layer to
`produce the multilayer polymer structure. In this aspect, the
`core layer comprises at least one high impact polystyrene
`(HIPS) polymer and from about 25 to about 50 Weight percent
`of the at least one ?ller. Each of the inner layer and the outer
`layer, independently, also comprise at least one HIPS poly
`mer. The at least one HIPS polymer has an elastomeric mate
`rial content of at least about 7 percent by Weight, an average
`particle siZe of the elastomeric material from about 1 to about
`10 microns, and a mineral oil content of less than about 4
`percent by Weight. The at least one HIPS polymer is further
`characterized by a melt ?oW rate of less than about 12 and a
`?exural modulus from about 200,000 to about 400,000 psi.
`
`Page 7 of 21
`
`

`
`US 2009/0110855 A1
`
`Apr. 30, 2009
`
`[0013] Although this method speci?es coextrusion as the
`process to produce a multilayer polymer structure, the present
`invention is not so limited. Multilayer structures of this inven
`tion can formed by any process knoWn to af?x similar or
`dissimilar polymer layers together, including combinations
`of tWo or more different processes. Additionally, further steps
`can be employed to convert the multilayer polymer structure
`into a ?nished article of manufacture, such as, for example,
`the process of thermoforming.
`[0014] Various articles of manufacture can be produced
`from the compositions and multilayer polymer structures of
`the present invention, including food service articles, such as
`cups, lids, plates, trays, containers, cutlery, and the like. In
`one aspect of the present invention, a multilayer food service
`article comprising 20 to about 40 Weight percent of at least
`one ?ller is provided. This multilayer food service article
`comprises a core layer having a ?rst side and a second side,
`the core layer comprising at least one ?ller; an inner layer
`adjacent to the ?rst side of the core layer; and an outer layer
`adjacent to the second side of the core layer. Each of the core
`layer, the inner layer, and the outer layer, independently,
`comprise at least one HIPS polymer. This HIPS polymer has
`an elastomeric material content of at least about 7 percent by
`Weight, an average particle siZe of the elastomeric material
`from about 1 to about 10 microns, and a mineral oil content of
`less than about 4 percent by Weight. The at least one HIPS
`polymer is characterized further by having a melt ?oW rate of
`less than about 12 and a ?exural modulus from about 200,000
`to about 400,000 psi.
`[0015] According to another aspect of the present inven
`tion, a multilayer cup is provided. This cup comprises a core
`layer having a ?rst side and a second side, the core layer
`comprising calcium carbonate; an inner layer adjacent to the
`?rst side of the core layer; an outer layer adjacent to the
`second side of the core layer; and a cap layer adjacent to the
`outer layer, the cap layer comprising crystal polystyrene.
`Each of the core layer, the inner layer, and the outer layer,
`independently, comprise at least one HIPS polymer. The at
`least one HIPS polymer has an elastomeric material content
`from about 7 percent to about 10.5 percent by Weight, an
`average particle siZe of the elastomeric material from about 2
`to about 8 microns, and a mineral oil content of less than about
`4 percent by Weight. The at least one HIPS polymer is char
`acteriZed by a melt ?oW rate of less than about 3.6 and a
`?exural modulus from about 225,000 to about 325,000 psi. It
`is contemplated that this multilayer cup contains from 20 to
`about 40 Weight percent of calcium carbonate, from about 4 to
`about 9 Weight percent of elastomeric material, and less than
`5 Weight percent crystal polystyrene.
`[0016] In another aspect, a masterbatch composition is pro
`vided. A masterbatch can be described generally as a compo
`sition or formulation containing a high loading or concentra
`tion of an additive or ?ller in a carrier resin. The masterbatch
`composition is subsequently let doWn in, and blended With,
`another polymer at a certain percentage to give the ?nal
`Weight percent of the ?ller or additive desired in the formu
`lation. The present invention discloses a novel masterbatch
`composition comprising from about 50 to about 85 Weight
`percent of at least one ?ller. Such a masterbatch composition
`comprises at least one HIPS polymer and the at least one ?ller.
`Generally, the HIPS polymer has an elastomeric material
`content of at least about 7 percent by Weight, an average
`particle siZe of the elastomeric material from about 1 to about
`10 microns, and a mineral oil content of less than about 4
`
`percent by Weight. Further, the at least one HIPS polymer is
`characterized by a melt ?oW rate of less than about 12 and a
`?exural modulus from about 200,000 to about 400,000 psi.
`[0017] A single layer polymer structure, or one or more
`layers in a multilayer polymer structure, can comprise these
`masterbatch compositions. One such example is a single layer
`in a multilayer polymer structure, Where the single layer
`comprises a masterbatch composition containing about 70 to
`about 75 Weight percent calcium carbonate, as the ?ller, and
`at least one HIPS polymer With characteristics as described
`above.
`
`BRIEF DESCRIPTION OF THE FIGURES
`
`[0018] FIG. 1 presents an illustration of a 3-layer multilayer
`polymer structure according to one aspect of the present
`invention.
`[0019] FIG. 2 presents an illustration of a 4-layer multilayer
`polymer structure according to one aspect of the present
`invention.
`[0020] FIG. 3 presents an illustration of a 5-layer multilayer
`polymer structure according to one aspect of the present
`invention.
`[0021] FIG. 4 presents an illustration of a 7-layer multilayer
`polymer structure according to one aspect of the present
`invention.
`[0022] FIG. 5 presents a plot of the tensile strength at yield
`(psi) versus Weight percent of calcium carbonate for ?lled
`polystyrene formulations containing Resin A, Resin C, and
`Resin D.
`[0023] FIG. 6 presents a plot of the tensile strength at break
`(psi) versus Weight percent of calcium carbonate for ?lled
`polystyrene formulations containing Resin A, Resin C, and
`Resin D.
`[0024] FIG. 7 presents a plot of the notched IZod impact
`strength (ft-lbs/in) versus Weight percent of calcium carbon
`ate for ?lled polystyrene formulations containing Resin A,
`Resin C, and Resin D.
`[0025] FIG. 8 presents a plot of the unnotched IZod impact
`strength (ft-lbs/in) versus Weight percent of calcium carbon
`ate for ?lled polystyrene formulations containing Resin A,
`Resin C, and Resin D.
`[0026] FIG. 9 presents a plot of the elongation at break (%)
`versus Weight percent of calcium carbonate for ?lled poly
`styrene formulations containing Resin A, Resin C, and Resin
`D.
`[0027] FIG. 10 presents a plot of the elongation at yield (%)
`versus Weight percent of calcium carbonate for ?lled poly
`styrene formulations containing Resin A, Resin C, and Resin
`D.
`[0028] FIG. 11 presents a plot of the ?exural modulus (psi)
`versus Weight percent of calcium carbonate for ?lled poly
`styrene formulations containing Resin A, Resin C, and Resin
`D.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`[0029] The present invention discloses novel multilayer
`polymer structures and methods of making such structures.
`These multilayer polymer structures comprise from 20 to
`about 40 Weight percent of at least one ?ller. Multilayer
`polymer structures in accordance With the present invention
`comprise:
`[0030] (a) a core layer having a ?rst side and a second side,
`the core layer comprising at least one ?ller;
`
`Page 8 of 21
`
`

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`US 2009/0110855 A1
`
`Apr. 30, 2009
`
`[0031] (b) an inner layer positioned on the ?rst side of the
`core layer; and
`[0032] (c) an outer layer positioned on the second side of
`the core layer;
`[0033] Wherein:
`[0034] each of the core layer, the inner layer, and the outer
`layer, independently, comprise at least one high impact poly
`styrene (HIPS) polymer,
`[0035] Wherein the at least one HIPS polymer has an elas
`tomeric material content of at least about 7 percent by Weight,
`an average particle siZe of the elastomeric material from
`about 1 to about 10 microns, a mineral oil content of less than
`about 4 percent by Weight, and
`[0036] Wherein the at least one HIPS polymer is character
`iZed by a melt ?oW rate of less than about 12 and a ?exural
`modulus from about 200,000 to about 400,000 psi.
`[0037] Applicants disclose several types of ranges in the
`present invention. These include, but are not limited to, a
`range of Weight percent of ?ller in a multilayer polymer
`structure, a range of Weight percent of elastomeric material in
`a HIPS polymer, a range of average particle siZe of the elas
`tomeric material, a range of mineral oil content in a HIPS
`polymer, a range of melt ?oW rate of a HIPS polymer, a range
`of ?exural modulus of a HIPS polymer, and a range of Weight
`percent of crystal polystyrene in a multilayer polymer struc
`ture. When Applicants disclose or claim a range of any type,
`Applicants’ intent is to disclose or claim individually each
`possible number that such a range could reasonably encom
`pass, as Well as any sub-ranges and combinations of sub
`ranges encompassed therein. For example, by a disclosure
`that the Weight percent of at least one ?ller in the multilayer
`polymer structure is from 20 to about 40 Weight percent,
`Applicants intend to recite that the Weight percent can be
`selected from 20, about 21, about 22, about 23, about 24,
`about 25, about 26, about 27, about 28, about 29, about 30,
`about 31, about 32, about 33, about 34, about 35, about 36,
`about 37, about 38, about 39, or about 40. Additionally, the
`Weight percent of the at least one ?ller can be Within any range
`from 20 to about 40 (for example, the Weight percent is in a
`range from about 22 to about 38 percent), and this also
`includes any combination of ranges betWeen 20 and about 40
`(for example, 20 to about 25 percent and about 30 to about 35
`percent). Likewise, all other ranges disclosed herein should
`be interpreted in a manner similar to this example.
`[0038] Applicants reserve the right to proviso out or
`exclude any individual members of any such range, including
`any sub-ranges or combinations of sub-ranges Within the
`stated range, that can be claimed according to a range or in
`any similar manner, if for any reason Applicants choose to
`claim less than the full measure of the disclosure, for
`example, to account for a reference that Applicants may be
`unaWare of at the time of the ?ling of the application.
`[0039] While compositions, formulations, polymer struc
`tures, articles, and methods are described in terms of com
`prising various components or steps, these compositions, for
`mulations, polymer structures, articles, and methods can also
`“consist essentially of” or “consist of” the various compo
`nents or steps.
`
`Polystyrene Polymers
`[0040] The present invention utiliZes polymers of vinyl
`aromatic compounds Which have been modi?ed With an elas
`tomeric material. One such vinyl aromatic polymer suitable
`for use in the present invention is polystyrene (PS). Polysty
`
`rene Which has been modi?ed With an elastomeric material is
`often referred to as rubber-modi?ed polystyrene or high
`impact polystyrene (HIPS). Generally, HIPS comprises a
`polystyrene polymer having discrete particles of an elasto
`meric material dispersed throughout the styrene polymer
`matrix.
`[0041] HIPS materials are generally obtained by polymer
`iZing, or copolymeriZing, the vinyl aromatic monomer (e. g.,
`styrene) in the presence of the elastomer material. Polymer
`iZing in the presence of the elastomeric material generally
`results in a superior product to blended products (e.g., equiva
`lent impact strength at loWer elastomer incorporation), but
`blended products and other means of incorporating the elas
`tomeric material into the polystyrene (PS) polymer can be
`employed. Thus, HIPS polymers manufactured in accordance
`With any conventional process knoWn to those of skill in the
`art can be used in the present invention.
`[0042] An elastomeric material canbe a natural or synthetic
`rubber or any elastomeric material that acts as a toughening
`agent When dispersed in a polymer matrix. Suitable elasto
`meric polymers for modifying vinyl aromatic polymers such
`as polystyrene generally have a glass transition temperature,
`Tg, less than Zero and often less than —200 C. Examples of
`suitable elastomeric polymers include, but are not limited to,
`homopolymers of C4-C6 1,3-dienes (e.g., polybutadiene,
`polyisoprene), copolymers of one or more vinyl aromatic
`monomers and one or more C4-C6 1,3-dienes (e.g., styrene
`butadiene copolymers), copolymers of ethylene and propy
`lene (e. g., ethylene-propylene rubber or EPR), terpolymers of
`ethylene, propylene, and a diene (e. g., EPDM rubber), and the
`like, or combinations thereof. In other aspects of this inven
`tion, the elastomeric material is selected from a polybutadi
`ene, a polyisobutylene, a polybutene, a polyisoprene, a sty
`rene-butadiene copolymer, or a mixture or combination of
`one or more of these materials.
`[0043] Numerous HIPS polymer grades are readily avail
`able from several PS resin suppliers and are often selected
`based on the requirements of the end-use application and the
`mode of processing (sheet extrusion, injection molding, etc.)
`to be employed. Table I lists several polystyrene resin grades
`that Will be discussed throughout this disclosure. Table I also
`includes nominal or data sheet properties for each respective
`HIPS polymer resin grade. These resin grades are commer
`cially available from Chevron Phillips Chemical Company,
`DoW Chemical Company, and Total Petrochemicals.
`[0044] Polybutadiene and polyisobutylene are the pre
`dominant elastomeric materials in the commercial grades
`listed in Table I. For instance, Resins C, G, H, and I contain
`both of these elastomeric materials. Resin E, hoWever, con
`tains polybutadiene but does not contain polyisobutylene.
`Resins C and I contain higher levels of cis-polybutadiene than
`trans-polybutadiene, While the opposite is true for Resins E, F,
`G, and H. Generally, HIPS grades With higher cis-polybuta
`diene content, as compared to trans, have superior environ
`mental stress crack resistance (ESCR) and are more ?exible at
`the same elastomeric content in the HIPS resin.
`[0045] As noted above, a HIPS polymer comprises a poly
`styrene matrix having dispersed therein particles of an elas
`tomeric material. The average particle siZe of the elastomeric
`material in the HIPS polymer can be controlled during the
`manufacture of the HIPS polymer. HIPS polymers having
`average particle siZes of the elastomeric material in the range
`from about 1 to about 10 microns are useful in the present
`invention. Further, the average particle siZe can be from about
`
`Page 9 of 21
`
`

`
`US 2009/0110855 A1
`
`Apr. 30, 2009
`
`2 to about 8 microns in another aspect of this invention. In yet
`another aspect, the average particle siZe of the elastomeric
`material in the HIPS polymer is from about 2 to about 4
`microns. In accordance With a different aspect of the present
`invention, the average particle siZe of the elastomeric material
`is from about 6 to about 8 microns. The average particle siZe
`of the elastomeric material can be determined by any means
`knoWn to those of skill in the art, such as from particle siZe
`distribution curves determined via commercially available
`particle siZe analyZers.
`[0046] It has been discovered that the Weight percent of the
`elastomeric material in the HIPS polymer should be at least
`about 7 percent for the multilayer polymer structures to have
`the unique properties disclosed herein. In another aspect, the
`HIPS polymer has an elastomeric material content in a range
`from about 7 percent to about 15 percent by Weight. Altema
`tively, the percent of the elastomeric material in the HIPS
`polymer can be from about 8 percent to about 13 percent, or
`from about 8 percent to about 11 percent, by Weight, in other
`aspects of this invention. Yet, in still another aspect of the
`present invention, the Weight percent of the elastomeric mate
`rial is in a range from about 7 percent to about 10.5 percent. In
`a further aspect, the Weight percent of the elastomeric mate
`rial in the HIPS polymer is from about 8 percent to about 10.5
`percent.
`[0047] In this invention, the HIPS polymer has a lubricant
`or mineral oil content of less than about 4 percent by Weight.
`In another aspect, the lubricant or mineral oil content is less
`than about 2 percent by Weight. Yet, in another aspect, the
`HIPS polymer resin contains substantially no added lubricant
`or mineral oil (e.g., less than 0.5 percent).
`[0048] Generally, polystyrene polymersiWhether crystal
`PS or HIPSihave superior strength properties at higher
`molecular Weights. Melt ?oW rate is inversely related to
`molecular Weight and, therefore, polystyrene polymers hav
`ing a loWer melt ?oW rate typically have superior strength
`properties. In addition to affecting the strength properties of
`the resulting polystyrene article or product, the melt ?oW rate
`of the polystyrene polymer is often selected based on the
`mode of fabrication employed, such as injection molding
`versus sheet extrusion, to ensure good processability in the
`respective mode of fabrication. In balancing these strength
`and processability considerations, the HIPS polymer
`employed in the multilayer polymer structures of this inven
`tion should have a melt ?oW rate of less than about 12. Melt
`?oW rate data has units of g/ 10 min, and is measured at 20000
`using a 5-Kg Weight in accordance With ASTM D1238. In
`other aspects of the present invention, the melt ?oW rate is less
`
`than about 10, less than about 8, or less than about 5. In a
`further aspect, the melt ?oW rate of the HIPS polymer is less
`than about 3.6. In a different aspect, the melt ?oW rate of the
`HIPS polymer is in a range from about 2.8 to about 3.5.
`[0049] It is further contemplated that HIPS polymers hav
`ing a ?exural modulus from about 200,000 to about 400,000
`psi can be employed in this invention. Flexural modulus is one
`measure of the stiffness or rigidity of an article, and is
`expressed in units of psi and is determined in accordance With
`ASTM D790. In another aspect of the present invention, a
`HIPS polymer having a ?exural modulus in a range from
`about 225,000 to about 350,000 psi can be used. Further, the
`?exural modulus can be in a range from about 275,000 to
`about 325,000 psi, or from about 225,000 to about 250,000
`psi, in other aspects of the invention. In a different aspect, a
`HIPS polymer having a ?exural modulus in a range from
`about 225,000 to about 325,000 psi can be used in the present
`invention.
`[0050] Another measure of stiffness or rigidity is tensile
`modulus. Tensile modulus is determined using ASTM D638
`and has units of psi. HIPS polymers having a tensile modulus
`from about 175,000 to about 350,000 psi are Within the scope
`of the present invention. In another aspect, a HIPS polymer
`having a tensile modulus in a range from about 190,000 to
`about 310,000 psi can be used. The tensile modulus can be in
`a range from about 290,000 to about 310,000 psi, or from
`about 190,000 to about 250,000 psi, in other aspects of the
`invention.
`[0051] In one aspect of this invention, the modulus or stiff
`ness of a formulation containing a PS or HIPS grade With at
`least one ?ller should increase, generally, in a linear fashion
`With the Weight percentage of the at least one ?ller in the
`formulation. Thus, in this aspect, an increase in ?exural
`modulus or tensile modulus With ?ller loading alloWs the
`polymer structure to be doWngauged While maintaining the
`same rigidity as that of the thicker un?lled polymer structure.
`Such a feature is demonstrated, for instance, in FIG. 11 in
`Example 1 that folloWs.
`[0052] In addition to HIPS polymer resin grades, other
`polystyrene grades can be employed in certain aspects of this
`invention. Crystal PS, often referred to as general purpose PS,
`is a polystyrene polymer Which has not been modi?ed With an
`elastomeric material. Articles produced from crystal PS gen
`erally have excellent clarity and stiffness, i.e., a high ?exural
`modulus or ?ex modulus. HIPS polymers, as compared to
`crystal PS, are opaque and generally have superior impact
`strength, ?exibility, and some grades have superior environ
`mental stress crack resistance (ESCR).
`
`TABLE I
`
`Polystyrene resins and properties.
`
`Properties
`
`Resin A
`
`Resin B
`
`Resin C
`
`Resin D
`
`Resin E
`
`Resin F
`
`Resin G Resin H
`
`Resin I
`
`4
`
`13
`
`3.8
`
`2.8
`
`3.5
`
`3.0
`
`3.2
`
`3.2
`
`3.0
`
`340,000
`
`320,000
`
`230,000
`
`250,000
`
`300,000
`
`300,000
`
`240,000
`
`250,000
`
`191,000
`
`370,000
`
`300,000
`
`240,000
`
`240,000
`
`310,000
`
`290,000
`
`225,000
`
`225,000
`
`232,000
`
`Melt Flow
`(g/ 10 min.)
`Tensile
`Modulus
`(Psi)
`Flexural
`Modulus
`(Psi)
`
`Page 10 of 21
`
`

`
`US 2009/0110855 A1
`
`Apr. 30, 2009
`
`TABLE I-continued
`
`Polysyrene resins and properties.
`
`Properties
`
`Resin A
`
`Resin B
`
`Resin C
`
`Resin D
`
`Resin E
`
`Resin F
`
`Resin G Resin H
`
`Resin I
`
`Flexural
`Strength
`(Psi)
`Elastomeric
`Material
`Content
`(%)
`Particle Size of
`Elastomeric
`Material
`(microns)
`Notched Izod
`(ft-lbs/in)
`Mineral Oil
`Content
`(%)
`Elongation at
`Break
`(%)
`
`8,300
`
`5,700
`
`5,000
`
`5,800
`
`6,300
`
`5,600
`
`4,200
`
`4,500
`
`5,400
`
`5.5
`
`6.0
`
`11
`
`8.5
`
`8.0
`
`8.5
`
`9.5-10.0
`
`9.5-10.0
`
`9.0-10.5
`
`2.7
`
`2.3
`
`6.8
`
`7.2
`
`2.5
`
`2.1
`
`6.8
`
`6.8
`
`6.0-8.0
`
`1.9
`
`1.75
`
`2.1
`
`6.25
`
`2.9
`
`2.0
`
`2.3
`
`2.75
`
`3.0
`
`4.0
`
`2.4
`
`3.0
`
`2.7
`
`1.0
`
`2.7
`
`0
`
`2.6
`
`0.2
`
`45
`
`45
`
`65
`
`55
`
`55
`
`65
`
`85
`
`65
`
`62
`
`Fillers
`[0053] At least one ?ller is employed in the structures and
`formulations of the present invention. Suitable ?llers include,
`but are not limited to, calcium carbonate, calcium sulphate,
`magnesium carbonate, magnesium hydroxide, silica, alu
`mina, aluminum oxide, aluminum trihydrate, antimony
`oxide, talc, mica, clays (e.g., kaolin), ?y ash, cellulosic ?bers,
`glass ?bers, glass ?akes, gl