Method for preparing foamed styrene copolymer

Abstract

A method of making a foamed styrenic copolymer, the method comprising: reacting a styrenic copolymer with an ionomer to form a composition; and contacting a blowing agent with the composition to form a foamed styrene polymer. An article formed from a composition comprising a styrene copolymer, an ionomer, and a blowing agent.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. patent application serial number 17 / 743,957, filed on May 13, 2022, entitled “High Melt Strength Polystyrene Compositions and Methods of Making and Using the Same,” the entire contents of which are incorporated herein by reference for all purposes.

[0003] STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0004] none. background Technical Field

[0006] The present disclosure relates generally to polystyrene compositions. More specifically, the present disclosure relates to expanded polystyrene compositions having lower foam density and improved surface quality. Background Art

[0007] Polystyrene compositions (e.g., expanded polystyrene compositions) can be used in a variety of applications. Expanded polystyrene has the advantages of low cost and excellent physical properties (e.g., high structural strength, low density). Extruded polystyrene (XPS) foam produced with hydrocarbon blowing agents is commonly used to make a variety of items, such as disposable foam packaging (meat trays, clam shells, etc.). Summary of the invention

[0008] Disclosed herein is a method for preparing a foamed styrene copolymer, the method comprising: reacting a styrene copolymer with an ionomer to form a composition; and contacting a blowing agent with the composition to form a foamed styrene polymer.

[0009] Also disclosed herein is an article formed from a composition comprising a styrene copolymer, an ionomer, and a blowing agent.

[0010] Also disclosed herein is a foamed polystyrene comprising (i) a styrene copolymer; (ii) an ionomer; and (iii) a blowing agent, wherein the ionomer is present in an amount of about 500 ppm to about 2500 ppm; wherein the blowing agent is present in an amount of about 1% to about 10%, and wherein the foamed polystyrene has a density of about 0.040 g / cc to about 0.100 g / cc.

[0011] BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a graph showing the melt strength of Example 1 sample.

[0013] Figure 2 is a graph showing the relationship between density and blowing agent concentration for samples from Example 2.

[0014] Figure 3 This is a photograph of surface defects formed in the sample of Example 3. DETAILED DESCRIPTION

[0015] As mentioned above, XPS foam is used to make a variety of products. Many manufacturers try to reduce the density (lightweight) of their final products to reduce the cost of resin, transportation or taxes. Products made from XPS are typically produced using rolls of polystyrene sheets in a thermoforming process, or directly extruded into panels that are prone to surface corrugation. Foam corrugation can produce surface defects, thereby increasing recycling, waste, customer complaints and manufacturer costs. Therefore, there is a need for a foamed polystyrene composition that can provide a low-density final product with a reduced incidence of surface defects.

[0016] Disclosed herein are expanded polystyrene compositions with improved melt strength and methods of making and using the same. In one aspect, a polymer composition comprises a styrene copolymer and an ionomer. The composition can produce expanded polystyrene that exhibits increased melt strength, characterized in that a relatively low density polystyrene foam is formed. These compositions prepared as described herein will be referred to as polystyrene compositions with improved melt strength (PSIMS).

[0017] In one aspect, PSIMS includes styrene, wherein the styrene may be a homopolymer or may optionally include one or more comonomers. Styrene, also known as vinylbenzene, ethylbenzene, and phenylethylene, is an organic compound represented by the chemical formula C8H8. Styrene is widely used commercially, and the term "styrene" as used herein includes various substituted styrenes (e.g., α-methylstyrene), ring-substituted styrenes (e.g., p-methylstyrene), disubstituted styrenes (e.g., p-tert-butylstyrene), and unsubstituted styrenes.

[0018] In one aspect, the content of styrene in the PSIMS is from about 95 wt % to about 99.99 wt % (weight percent (wt.%)), or from about 96 wt % to about 99.99 wt %, or from about 97 wt % to about 99.99 wt %. Herein, the weight percentages are based on the total weight of the composition. In one aspect, styrene constitutes the remainder of the PSIMS when other ingredients are considered.

[0019] In some aspects, the styrene polymer further comprises a comonomer which forms a styrene copolymer with styrene when polymerized. Examples of these comonomers include, for example, but not limited to: α-methylstyrene; halogenated styrene; alkylated styrene; acrylonitrile; esters of (meth)acrylic acid with alcohols having 1-8 carbon atoms; N-vinyl compounds such as vinyl carbazole, maleic anhydride; compounds containing two polymerizable double bonds, such as, but not limited to, divinylbenzene or butanediol diacrylate; or combinations thereof. The comonomer may be present in an effective amount to impart one or more properties desired by the user of the composition. The effective amount may be determined by a person of ordinary skill in the art. For example, the content of the comonomer in the styrene copolymer may range from about 0.05% by weight to about 5% by weight, or from about 0.5% by weight to about 5% by weight or from about 1% by weight to about 5% by weight.

[0020] In some aspects, the styrene copolymer also includes an elastomer, and the resulting composition can be a high impact composition (HIC). The HIC includes an elastomeric phase, which is embedded in a polystyrene matrix to produce a composition with higher impact resistance. In one aspect, the styrene copolymer composition is a HIC comprising a conjugated diene monomer as an elastomer. Non-limiting examples of conjugated diene monomers suitable for use in the present disclosure include, but are not limited to, 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 2-methyl-1,3-butadiene, and 2-chloro-1,3-butadiene. Alternatively, the HIC includes an aliphatic conjugated diene monomer as an elastomer. Without limitation, examples of aliphatic conjugated diene monomers suitable for use in the present disclosure include C4 to C9 dienes, such as butadiene monomers. Blends or copolymers of diene comonomers can also be used. The elastomer can exist in an effective amount to produce one or more user-desired properties. The effective amount can be determined by a person of ordinary skill in the art.

[0021] In one aspect, the PSIMS comprises an ionomer for facilitating the incorporation of a blowing agent into the composition. In one aspect, the ionomer is a metal acrylate. Non-limiting examples of ionomers suitable for use in the present disclosure include zinc dimethacrylate, stearyl methacrylate, hydroxyethylmethacrylate, or a combination thereof. In one aspect, the ionomer comprises zinc dimethacrylate. The content of the ionomer in the PSIMS is from about 500 ppm to about 2500 ppm, or from about 500 ppm to about 2000 ppm, or from about 1000 ppm to about 2000 ppm.

[0022] In one aspect, the production method of PSMIS includes contacting styrene monomer, optional comonomer and ionomer with at least one initiator. Any initiator capable of forming free radicals and promoting styrene polymerization can be used. Such initiators are well known in the art and include, but are not limited to, organic peroxides. Examples of organic peroxides that can be used to initiate polymerization include, but are not limited to, diacyl peroxides, peroxydicarbonates, monoperoxycarbonates, peroxyketones, peroxyesters, dialkyl peroxides, hydroperoxides, or combinations thereof. The selection of initiator and effective amount will depend on many factors (e.g., temperature, reaction time) and can be selected by those skilled in the art to meet the desired process requirements. Polymerization initiators and effective amounts thereof are described in U.S. Patent Nos. 6,822,046; 4,861,127; 5,559,162; 4,433,099 and 7,179,873, each of which is incorporated herein by reference in its entirety for all purposes.

[0023] In one aspect, the polymerization reaction to form PSMIS can be carried out in a solution polymerization or bulk polymerization process. Bulk polymerization, also known as bulk polymerization, refers to the polymerization of monomers in the absence of any medium other than the monomers and catalysts or polymerization initiators. Solution polymerization refers to a polymerization process in which the monomers and polymerization initiators are dissolved in a non-monomer liquid solvent at the beginning of the polymerization reaction. The liquid is also usually a solvent for the resulting polymer or copolymer.

[0024] The polymerization process can be intermittent or continuous. In one aspect, the polymerization reaction can be carried out using a continuous production process in a polymerization device including a single reactor or multiple reactors. For example, the polymer composition can be prepared using an upflow reactor. The reactor and conditions for producing the polymer composition are disclosed in U.S. Patent No. 4777210, the entire contents of which are incorporated herein by reference for all purposes.

[0025] The temperature range for producing PSIMS can be selected to be consistent with the operating characteristics of the equipment used to perform the polymerization. In one aspect, the temperature range for polymerization can be 90°C to 240°C. In another aspect, the temperature range for polymerization can be 100°C to 180°C. In another aspect, the polymerization reaction can be carried out in multiple reactors, and each reactor has an optimal temperature range. For example, the polymerization reaction can be carried out in a reactor system using a first polymerization reactor and a second polymerization reactor, and the first polymerization reactor and the third polymerization reactor can be a continuous stirred tank reactor (CSTR) or a plug flow reactor. In one aspect, the polymerization reactor used to produce PSIMS includes multiple reactors, wherein the first reactor (such as a CSTR), also called a prepolymerization reactor, can be operated in a temperature range of 90°C to 135°C, and the second reactor (such as a CSTR or a plug flow reactor) can be operated in a temperature range of 100°C to 165°C.

[0026] The polymer product effluent from the first reactor may be referred to herein as a prepolymer. When the prepolymer reaches the desired conversion, it may be passed through a heating device into a second reactor for further polymerization. The polymer product effluent from the second reactor may be further processed as known to those of ordinary skill in the art and described in detail in the literature. After the polymerization reaction is complete, the PSIMS is recovered and subsequently processed, such as devolatized, granulated, etc.

[0027] In one aspect, PSIMS may also contain necessary additives to impart desired physical properties, such as increasing gloss or color. Examples of additives include, but are not limited to, chain transfer agents, talc, antioxidants, UV stabilizers, lubricants, mineral oils, plasticizers, and the like. The above additives may be used alone or in combination to form various formulations of the composition. For example, stabilizers or stabilizing agents may be used to help protect the polymeric composition from degradation due to exposure to excessive temperatures and / or excessive ultraviolet light. These additives may be included in amounts effective to impart the desired properties. The effective amounts and methods of including these additives in the polymer composition are known to those skilled in the art. For example, one or more additives may be added after PSIMS recovery, such as during compounding such as granulation. Alternatively, such additives may be added during the formation of PSIMS or may be added to one or more other components of PSIMS.

[0028] In one aspect, the PSIMS comprises a blowing agent. Herein, a blowing agent refers to a substance capable of producing a honeycomb structure in various materials (such as polymers, plastics, and metals) that undergo hardening or phase change through a foaming process. In one aspect, blowing agents suitable for use in the present invention include: nitrogen, carbon dioxide, water, air, pentane, hexane, ethylene dichloride, isobutane, or a combination thereof. The blowing agent may be contacted with the PSIMS in an amount of about 1% to about 10%, or about 2% to about 6%, or about 3% to about 4%.

[0029] In one aspect, the PSIMS is contacted with a blowing agent and the components are thoroughly mixed, for example, by mixing or extrusion. In one aspect, the styrene copolymer is plasticized or melted by heating in an extruder and is thoroughly contacted and mixed with a blowing agent, such as isobutane, at a temperature of about 315°F to about 460°F, or about 155°F to 460°F, or about 155°F to about 240°F.

[0030] Alternatively, the styrene copolymer can be contacted with the blowing agent prior to introducing the mixture into the extruder (such as by bulk mixing), during the introduction of the polymer composition into the extruder, or a combination of both.

[0031] In one aspect, the foamed PSIMS composition can then be passed through a relaxation zone at the final stage of the extruder before being directed to the die where it is cooled. The PSIMS can be cooled from a temperature of 150° C. to 210° C. to a temperature of 40° C. to 100° C. under continuous stirring before being extruded through the die. Methods for preparing foamed polystyrene compositions are described in U.S. Pat. Nos. 5,006,566 and 6,387,968, the entire contents of which are incorporated herein by reference for all purposes.

[0032] Without being bound by theory, the presence of ionomers (e.g., ZDMA) in the polystyrene chains of PSIMS increases the polymer melt strength that forms the foam cell walls. Thus, more of the blowing agent remains in the melt during the expansion of the blowing agent, thereby reducing cell collapse.

[0033] In one aspect, the PSIMS can be characterized by an increase in melt strength. For example, the PSIMS melt strength can be shown to be from about 0.035N to about 0.048N, or from about 0.038N to about 0.045N, or from about 0.039N to about 0.041N.

[0034] In one aspect, the PSIMS can be characterized by a melt flow rate comparable to that of an otherwise similar styrene copolymer composition that does not contain the ionomer in the amounts disclosed herein. For example, the PSIMS can have a melt flow rate ranging from about 1.0 g / 10 min (grams per 10 minutes) to about 5.0 g / 10 min, or from about 1.2 g / 10 min to about 3.0 g / 10 min, or from about 1.5 g / 10 min to 1.8 g / 10 min, as determined according to ASTM D-1238.

[0035] In one aspect, the PSIMS can be characterized by reduced density. For example, the density of the PSIMS can be from about 0.040 g / cc to about 0.100 g / cc, or from about 0.045 g / cc to about 0.090 g / cc, or from about 0.050 g / cc to about 0.080 g / cc.

[0036] The PSIMS of the present disclosure can be converted into articles by any suitable method. Articles can be produced simultaneously with the mixing and / or foaming of the PSIMS (e.g., on a continuous integrated production line), or can be produced after the mixing and / or foaming of the PSIMS (e.g., on a separate production line, such as an end-use compounding and / or thermoforming production line). In one aspect, as described herein, the PSIMS is mixed and foamed by extrusion or compounding, and then the molten PSIMS is fed to a molding process (e.g., a mold, a die, a spreader bar, etc.) that shapes the PSIMS. The foaming of the PSIMS can occur before, during, or after molding.

[0037] In one aspect, molten PSIMS is injected into a mold, where the PSIMS foams and fills the mold to form a molded article. In one aspect, the PSIMS is formed into a sheet and then subjected to further processing steps such as thermoforming to produce an article. Examples of articles that can be formed from PSIMS include: food packaging; office supplies; plastic lumber or alternative lumber; patio decks; structural supports; laminate flooring compositions; polymer foam substrates and decorative surfaces such as crown molding; weather-resistant outdoor materials; promotional signs and displays; home furnishings and consumer products; building insulation; cosmetic packaging; outdoor alternative materials, etc. Other articles are obvious to those of ordinary skill in the art.

[0038] The PSIMS of the present disclosure advantageously provides an increase in the incorporation of a blowing agent into a styrene copolymer, thereby resulting in a foamed polymer having a reduced density. For example, the PSIMS disclosed herein is an expanded polystyrene comprising (i) a styrene copolymer; (ii) an ionomer; and (iii) a blowing agent, wherein the ionomer is present in an amount of about 500 ppm to about 2500 ppm; wherein the blowing agent is present in an amount of about 1% to about 10%, and wherein the density of the expanded polystyrene is from about 0.040 g / cc to about 0.100 g / cc. In an alternative aspect, the ionomer is present in an amount of about 500 ppm to about 2500 ppm; wherein the blowing agent is present in an amount of about 5% to about 6%, and wherein the density of the expanded polystyrene is less than about 0.100 g / cc.

[0039] Example

[0040] These aspects have been generally described, and the following examples are provided as specific aspects of the present disclosure to demonstrate its practice and advantages. It should be understood that the examples are given by way of illustration and are not intended to limit the specification or claims in any way.

[0041] Example 1

[0042] The melt flow rate of PSIMS of the type disclosed herein was studied. Specifically, the polystyrene containing zinc dimethacrylate (designated as sample 595T) exhibited a melt flow rate comparable to that of the control polystyrene composition (designated as sample 585). The melt flow rate of both samples was found to be 1.6 g / 10 min as measured according to ASTM D-1238.

[0043] The melt strength of sample 595T was compared to the melt strength of a control polystyrene composition designated as sample 585. Both samples were foamed using isobutane as a blowing agent and 0.5 wt % talc as a nucleating agent. The second extruder temperature was adjusted to maintain a die discharge pressure of 1100 psi to 1200 psi. A 5 mm rod die was used. A gear pump was used to maintain a throughput of about 6.5 pounds per hour (lbs / hr). Figure 1 Results of melt strength analysis are shown.

[0044] Example 2

[0045] The ability to form low density polystyrene compositions using PSIMS of the present disclosure was studied. Specifically, foamed samples of the 595T composition were prepared using 4% to 6.2% isobutane blowing agent and compared to the 585 composition also containing 4% to 6.2% isobutane blowing agent. The results are shown in Figure 2The 595T sample showed lower density at higher isobutane concentrations (4-6.2%). When the amount of blowing agent (isobutane) was from 3.5% to 6.2% isobutane, the foam density of PSIMS (sample 595T) was about 11% lower than the foam density of the 585 control sample.

[0046] Example 3

[0047] The ability of the polystyrene compositions of the present disclosure to form articles with fewer surface defects was studied using PSIMS. The effect on surface waviness was evaluated by adding a 595T sample to a lab scale foam production line behind a 585 sample while maintaining the same processing conditions and blowing agent concentration of 5% isobutane. Once the processing conditions were stable and the 595T foam was produced, the samples were collected. The 595T sample showed an improvement in surface waviness compared to the 585 control sample. Overall, the 595T sample had a smoother surface with fewer surface ridges. The foam showed Figure 3 middle.

[0048] Other public content

[0049] The following enumerated aspects of the present disclosure are provided as non-limiting examples.

[0050] A first aspect is a method of making a foamed styrene copolymer, the method comprising: reacting a styrene copolymer with an ionomer to form a composition; and

[0051] A blowing agent is contacted with the composition to form a foamed styrene polymer.

[0052] The second aspect is the method of the first aspect, wherein the reaction occurs during extrusion.

[0053] The third aspect is the method of any one of the first to second aspects, wherein the styrene copolymer comprises styrene, ring-substituted styrene, disubstituted styrene, unsubstituted styrene or a combination thereof.

[0054] The fourth aspect is the method of any one of the first to third aspects, wherein the styrene copolymer comprises α-methylstyrene, p-methylstyrene, p-tert-butylstyrene or a combination thereof.

[0055] The fifth aspect is the method according to any one of the first to fourth aspects, wherein the styrene copolymer further comprises a comonomer.

[0056] The sixth aspect is a method as described in any one of the first to fifth aspects, wherein the comonomer includes α-methylstyrene; halogenated styrene; alkylated styrene; acrylonitrile; esters of (meth)acrylic acid and alcohols having 1 to 8 carbon atoms; vinyl carbazole, maleic anhydride; divinylbenzene; butanediol diacrylate; or a combination thereof.

[0057] The seventh aspect is the method according to any one of the first to sixth aspects, wherein the styrene copolymer further comprises an elastomer.

[0058] The eighth aspect is the method of any one of the first to seventh aspects, wherein the elastomer comprises a diene monomer, an aliphatic conjugated diene monomer, or a combination thereof.

[0059] The ninth aspect is the method described in any one of the first to eighth aspects, wherein the elastomer comprises 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene or a combination thereof.

[0060] The tenth aspect is the method of any one of the first to ninth aspects, wherein the styrene copolymer is high impact polystyrene.

[0061] The eleventh aspect is the method of any one of the first to tenth aspects, wherein the content of the styrene copolymer is about 95 wt % to about 99 wt % based on the total weight of the composition.

[0062] A twelfth aspect is the method of any one of aspects 1 to 11, wherein the ionomer comprises a metal acrylate.

[0063] The thirteenth aspect is the method according to any one of the first to twelfth aspects, wherein the metal acrylate comprises zinc dimethacrylate, stearyl methacrylate salt, hydroxyethyl methacrylate salt or a combination thereof.

[0064] A fourteenth aspect is the method of any one of aspects one to thirteen, wherein the ionomer comprises zinc dimethacrylate.

[0065] A fifteenth aspect is the method of any one of aspects one to fourteen, wherein the ionomer is present in an amount of about 500 ppm to about 2500 ppm based on the total weight of the composition.

[0066] A sixteenth aspect is the method of any one of aspects one to fifteen, wherein the melt strength of the composition is from about 0.035N to about 0.048N.

[0067] The seventeenth aspect is the method of any one of the first to sixteenth aspects, wherein the melt flow rate of the composition is from about 1 g / 10 min to about 5 g / 10 min.

[0068] The eighteenth aspect is the method of any one of the first to seventeenth aspects, wherein the composition has a density of about 0.04 g / cc to about 0.08 g / cc.

[0069] The nineteenth aspect is the method of any one of the first to eighteenth aspects, wherein the blowing agent comprises nitrogen, carbon dioxide, water, air, pentane, hexane, ethylene dichloride, isobutane or a combination thereof.

[0070] A twentieth aspect is an article formed from a composition comprising a styrene copolymer, an ionomer, and a blowing agent.

[0071] Although different aspects are shown and described, various changes can be made to them by those skilled in the art without departing from the spirit and content of the present invention. The aspects described herein are examples only and are not intended to constitute limitations. Many changes and modifications to the aspects disclosed herein are possible and are within the scope of the present disclosure. When numerical ranges or limits are clearly indicated, it should be understood that these clear ranges or limits include repeated ranges or limits of the same magnitude falling within the clearly indicated ranges or limits (e.g., about 1-10 includes 2, 3, 4, etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). The term "optionally" is used relative to any element of the claim to indicate that a subject element is required or not required. All alternatives are within the scope of the claims. It should be understood that the use of broader terms (e.g., including, including, having, etc.) provides support for narrower terms (e.g., consisting of, substantially consisting of, substantially comprising, etc.).

[0072] Therefore, the scope of protection is not limited by the description listed above, but only by the appended claims, and the scope of the claims includes all equivalents of the subject matter of the claims. Each claim is incorporated into the specification as an aspect of the present disclosure. Therefore, the claims are further descriptions and supplements to the aspects disclosed herein. The discussion of references herein does not admit that they are prior art to the present disclosure, especially any references whose publication date may be after the priority date of this application. The disclosures of all patents, patent applications and publications listed herein are incorporated herein by reference, which provide exemplary, procedural or other detailed supplements to the contents stated herein.

Claims

1. A method for preparing a foamed styrene copolymer, the method comprising: reacting a styrene copolymer with an ionomer to form a composition; and A blowing agent is contacted with the composition to form a foamed styrene polymer, wherein the ionomer is present in an amount of about 500 ppm to about 2500 ppm and the blowing agent is present in an amount of about 1% to about 10%.

2. The method of claim 1, wherein: The reaction takes place during extrusion.

3. The method of claim 1, wherein: The styrene copolymer includes styrene, ring-substituted styrene, di-substituted styrene, unsubstituted styrene or a combination thereof.

4. The method of claim 1, wherein: The styrene copolymer includes α-methylstyrene, p-methylstyrene, p-tert-butylstyrene or a combination thereof.

5. The method of claim 1, wherein: The styrene copolymer also includes a comonomer.

6. The method of claim 5, wherein: The comonomer includes α-methylstyrene; halogenated styrene; alkylated styrene; acrylonitrile; esters of (meth)acrylic acid and alcohols having 1 to 8 carbon atoms; vinyl carbazole, maleic anhydride; divinylbenzene; butanediol diacrylate; or a combination thereof.

7. The method of claim 1, wherein: Styrene copolymers also include elastomers.

8. The method of claim 7, wherein: The elastomer includes a diene monomer, an aliphatic conjugated diene monomer, or a combination thereof.

9. The method of claim 7, wherein: The elastomer includes 1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, or a combination thereof.

10. The method of claim 7, wherein: Styrene copolymers are high impact polystyrene.

11. The method of claim 1, wherein: The styrene copolymer is present in an amount of about 95 wt % to about 99 wt % based on the total weight of the composition.

12. The method of claim 1, wherein: Ionomers include metal acrylates.

13. The method of claim 12, wherein: The metal acrylate includes zinc dimethacrylate, stearyl methacrylate salt, hydroxyethyl methacrylate salt or a combination thereof.

14. The method of claim 1, wherein: The ionomer includes zinc dimethacrylate.

15. The method of claim 1, wherein: The ionomer is present in an amount of about 500 ppm to about 2000 ppm based on the total weight of the composition.

16. The method of claim 1, wherein: The melt strength of the composition is from about 0.035N to about 0.048N.

17. The method of claim 1, wherein: The composition has a melt flow rate of about 1 g / 10 min to about 5 g / 10 min.

18. The method of claim 1, wherein: The composition has a density of about 0.04 g / cc to about 0.1 g / cc.

19. The method of claim 1, wherein: The blowing agent includes nitrogen, carbon dioxide, water, air, pentane, hexane, ethylene dichloride, isobutane or a combination thereof.

20. An article formed from a composition comprising a styrene copolymer, an ionomer, and a blowing agent.

21. A foamed polystyrene comprising: (i) Styrene copolymers; (ii) ionomers; and (iii) a blowing agent, wherein The ionomer content is about 500 ppm to about 2500 ppm; wherein the blowing agent content is about 1% to about 10%, and wherein the expanded polystyrene has a density of about 0.040 g / cc to about 0.100 g / cc.

22. The expanded polystyrene according to claim 21, wherein The ionomer is present in an amount of about 500 ppm to about 2500 ppm; wherein the blowing agent is present in an amount of about 5% to about 6%, and wherein the density of the expanded polystyrene is less than about 0.100 g / cc.

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