FOAMABLE POLYOLEFIN COMPOSITIONS AND METHODS THEREOF

Abstract

Foamed propylene-based reactor made polyolefins, and articles made therefrom, are described. The compositions have a resin that is a reactor made propylene based random copolymer or terpolymer with high comonomer content, combined with a foaming agent. The foaming agent can be at least one physical blowing agent or at least one chemical foaming agent, and may include optional nucleating agents. Reactor made copolymers and terpolymers have a large range of high comonomer content and therefore have physical properties such as increased flexibility, high gloss, lower sealing temperature, and improved compatibility with other polyolefins. These properties translate into a broad scope of potential applications and foamed architecture. This allows the combination of the copolymer or terpolymer, and foaming agents to be fine-tuned for selected foaming application.

Claims

1. A foam composition comprising: a reactor made polyolefin composition comprising a crystalline random copolymer having: a) a first propylene-based copolymer or terpolymer selected from the group comprising: i) a copolymer of propylene and ethylene, wherein the content of the ethylene is between 1-7 wt %; ii) a copolymer of propylene and at least one C.sub.4-C.sub.8 alpha-olefin, wherein the content of the alpha-olefin is between 2-14 wt %; iii) a terpolymer of propylene, ethylene, and at least one C.sub.4-C.sub.8 alpha-olefin, wherein the content of ethylene is between 0.5-4.5 wt % and the content of the alpha-olefin is between 2-6 wt %, wherein the total content of said ethylene and said at least one alpha-olefins in equal to or lower than 6.5 wt %; and/or b) a second propylene-based copolymer or terpolymer selected from the group comprising: i) a copolymer of propylene and at least one C.sub.4-C.sub.8 alpha-olefin, wherein the content of the alpha-olefin is between 8-30 wt %; ii) a terpolymer of propylene, ethylene, and at least one C.sub.4-C.sub.8 alpha-olefin, wherein the content of ethylene is between 1-7 wt % and the content of the alpha-olefin is between 6-8 wt %, wherein the total content of said ethylene and said at least one alpha-olefins in equal to or lower than 6.5 wt %; wherein said first propylene-based copolymer is present in a 0 to 80 wt % and said second propylene-based is present at a 20 to 100 wt %.

2. The foam composition of claim Error! Reference source not found., wherein said crystalline random copolymer has a melt flow rate between 2 to 15 g/10 min (ASTM D 1238).

3. The foam composition of claim Error! Reference source not found., wherein said reactor made polyolefin composition is foamed using at least one physical blowing agent (PBA) or at least one chemical foaming agent (CFA).

4. The foam composition of claim 3, wherein said reactor made polyolefin composition is combined with a masterbatch comprising at least one nucleating agent.

5. The foam composition of claim 4, wherein said physical blowing agent is selected from a group comprising highly pressurized CO.sub.2, N.sub.2, air, propane, isobutane, butane, CFC-derivatives, argon, or combinations thereof.

6. The foam composition of claim 4, wherein said chemical foaming agent is in the same masterbatch as at least one nucleating agent or in a different masterbatch as at least one nucleating agent.

7. The foam composition of claim 6, wherein the total amount of masterbatch in the foam composition is 5 wt % by weight or less of said reactor made polyolefin composition.

8. The foam composition of claim 3, wherein said chemical foaming agent is endothermic or exothermic.

9. The foam composition of claim 3, wherein said chemical foaming agent acts as a nucleating agent.

10. An article comprising a foamed reactor made polyolefin composition according to claim 1.

11. The article of claim 10, said article being a sheet, a strand, a tube, or a container.

12. A foam composition comprising: a reactor made polyolefin composition comprising a crystalline propylene/ethylene random copolymer having: a) from about 4.5 wt % to about 8 wt % of ethylene, and; b) from about 92 wt % to about 95.5 wt % of propylene wherein said crystalline propylene/ethylene random copolymer has a melt flow rate between 0.3 and 15 g/10 min (ASTM D 1238).

13. The foam composition of claim 12, wherein said reactor made polyolefin composition is foamed using at least one physical blowing agent (PBA) or at least one chemical foaming agent (CFA).

14. The foam composition of claim 13, wherein said reactor made polyolefin composition is combined with a masterbatch comprising at least one nucleating agent.

15. The foam composition of claim 14, wherein said physical blowing agent is selected from a group comprising highly pressurized CO.sub.2, N.sub.2, air, propane, isobutane, butane, CFC-derivatives, argon, or combinations thereof.

16. The foam composition of claim 14, wherein said chemical foaming agent is in the same masterbatch as at least one nucleating agent or in a different masterbatch as at least one nucleating agent.

17. The foam composition of claim 16, wherein the total amount of masterbatch in the foam composition is 5 wt % by weight or less of said reactor made polyolefin composition.

18. The foam composition of claim 13, wherein said chemical foaming agent is endothermic or exothermic.

19. The foam composition of claim 13, wherein said chemical foaming agent acts as a nucleating agent.

20. An article comprising a foamed reactor made polyolefin composition according to claim 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0040] FIG. 1 displays a schematic of the Catalloy process. Image courtesy of LyondellBasell (Houston, Tex.).

[0041] FIG. 2 displays exemplary extrusion process conditions for a monolayer foamed sheet formed from presently disclosed novel composition of a RACO or terpolymer and a masterbatch having an endothermic chemical nucleating and foaming agent.

[0042] FIG. 3A displays the cell size distribution for Adsyl 5C30F foam strands and FIG. 3B is a histogram of cell size distributions for Adsyl 5C30F foam strands. Adsyl 5C30F is a commercially available product from LyondellBasell (Houston, Tex.).

[0043] FIG. 4 displays trends for number of cells and range of cell sizes for foam sheet samples K17218 and K17219, prepared using Adsyl 7416XCP. Adsyl 7416XCP is a commercially available product from LyondellBasell (Houston, Tex.).

[0044] FIG. 5 displays the cell size distribution for multiple RACO and terpolymer foam monolayer sheets.

DEFINITIONS

[0045] As used herein, the term copolymer refers to a polyolefin that contains two types of alpha-olefin monomer units. It does not refer to an alloy of two homopolymers.

[0046] As used herein, the terms comonomer or comonomers refers to the type or types of monomers that are the minor components in the polymer chain. As an illustration, the ethylene is the comonomer in a random copolymer of propylene with ethylene, and ethylene and butene are the comonomers in a terpolymer of propylene with ethylene and butene.

[0047] As used herein, the terms random copolymer or RACO refers to a polymer that contains two types of monomer units such that the comonomer units are randomly distributed throughout the polymer chain.

[0048] As used herein, the term terpolymer refers to a polymer that contains three types of monomer units such that the two types of comonomer units are randomly distributed throughout the polymer chain.

[0049] As used herein, the term -olefin or alpha-olefin means an olefin of the general formula CH2=CHR, wherein R is a linear or branched alkyl containing from 1 to 10 carbon atoms. The -olefin can be selected, for example, from 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene, and the like.

[0050] The term reactor made is used to refer to polyolefins that are made in a reactor system.

[0051] As used herein, the term base resin refers to the reactor made propylene-based RACO or terpolymer resin with high comonomer content that is being foamed by at least one chemical foaming agent or at least one physical blowing agent. The phrase high comonomer content means that a monomer other than propylene is present in an amount of greater than about 5 wt %.

[0052] A foam is a continuous three-dimensional network or cellular structure of a solid or liquid phase, which surrounds a gaseous phase dispersed therein. In a polymeric foam, such as those presently disclosed, the solid phase is a polymeric resin, which forms the cell walls in the continuous cellular phase. The cellular fraction of the foam is the amount of foam that is in the cells or the gaseous phase.

[0053] The terms chemical foaming agent and chemical blowing agent are used interchangeably to denote chemical compounds that undergo a decomposition reaction during polymer processing that results in the production and release of gas. These compounds can be inorganic or organic, and the decomposition can be endothermic (need energy to initiate decomposition) or exothermic (release energy during decomposition). The energy needed to initiate decomposition can be supplied during processing of the polymer.

[0054] In some embodiments, the at least one chemical foaming agent can also act as a nucleating agent, and may be referred to as a nucleating chemical foaming agent.

[0055] Physical blowing agents are distinguishable from chemical foaming agents because they undergo a change of state during processing to generate gas. Compressed, liquified gases can be utilized as physical blowing agent, wherein they are injected into a polymer melt under high pressure. As pressure is relieved, the gas becomes less soluble in the melt, resulting in the formation of cells.

[0056] As used herein, the term masterbatch refers to premixed compositions having one or more solid or liquid additives used to impart other properties to the base resin. The masterbatches used in the present foamed compositions can include at least one chemical foaming agent or at least one nucleating agent or both, as well as include additives that do not interfere with the base resin's ability to foam. As masterbatches are already premixed compositions, their use alleviates issue of insufficient dispersion of the chemical foaming agent(s) and/or nucleating agent(s).

[0057] The terms melt flow rate and MFR are used interchangeably to refer to the measure of the ability of the melt of the base resin to flow under pressure. The melt flow rate is determined by ASTM D 1238L (Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer) unless otherwise noted. ASTM D 1238L measures the melt flow rate at 230 C. and 2.16 Kg of weight. The melt flow range is a range of melt flow rates.

[0058] All concentrations herein are by weight percent (wt %) unless otherwise specified.

[0059] The use of the word a or an when used in conjunction with the term comprising in the claims or the specification means one or more than one, unless the context dictates otherwise.

[0060] The term about means the stated value plus or minus the margin of error of measurement or plus or minus 10% if no method of measurement is indicated.

[0061] The use of the term or in the claims is used to mean and/or unless explicitly indicated to refer to alternatives only or if the alternatives are mutually exclusive.

[0062] The terms comprise, have, include and contain (and their variants) are open-ended linking verbs and allow the addition of other elements when used in a claim.

[0063] The phrase consisting of is closed, and excludes all additional elements.

[0064] The phrase consisting essentially of excludes additional material elements, but allows the inclusions of non-material elements that do not substantially change the nature of the presently disclosed compositions and methods.

[0065] The following abbreviations are used herein:

TABLE-US-00001 ABBREVIATION TERM CBA chemical blowing agent CFA chemical foaming agent MFR Melt flow rate MB-A Masterbatch A MB-B Masterbatch B MB-C Masterbatch C MB-D Masterbatch D MB-E Masterbatch E PBA physical blowing agent PE polyethylene PP polypropylene RACO Random copolymer SEM scanning electron microscopy wt % Weight percent

DESCRIPTION OF EMBODIMENTS OF THE DISCLOSURE

[0066] The disclosure provides novel foamable compositions of reactor made random polypropylene copolymer (RACO) or terpolymer polyolefins with improved physical properties over currently available foamed polyolefins. The RACOs and terpolymers used herein have a high comonomer content of greater than about 5 wt %, allowing these polyolefins to have a wide range of rigidity, melt temperatures, and other physical properties, allowing the resulting foams to be available for a broad variety of applications. For instance, certain foamed compositions with more rigid copolymers or terpolymers can be used in the automotive industry for spare tire packaging, whereas softer, less rigid copolymers or terpolymers can be foamed for use as shipping materials or food packaging. Additionally, the foaming agents needed to create the voids in the foams can be selected to elicit certain cell characteristics in the copolymers or terpolymers, further increasing the breadth of applications. Articles produced from the foamable compositions are also described.

[0067] Any reactor made random copolymer or terpolymer polyolefin having a propylene monomer as the base and having a high comonomer content (greater than about 5 wt %) with a final melt flow rate (MFR) between 0.1 and about 15 g/10 min (per ASTM D 1238L) can be used per the presently described methods.

[0068] In one aspect, the reactor made propylene-based polyolefin can be a crystalline copolymer having: (A) 20-80% by weight of one or more propylene-based components selected from the group consisting of propylene/ethylene copolymers containing 1-7% of ethylene; copolymers of propylene with one or more C.sub.4-C.sub.8 alpha-olefins, containing 2-10% of the C.sub.4-C.sub.8 alpha-olefins; terpolymers of propylene with ethylene and one or more C.sub.4-C.sub.8 alpha-olefins, containing 0.5-4.5% of ethylene and 2-6% of C.sub.4-C.sub.8 alpha-olefins, provided that the total content of ethylene and C.sub.4-C.sub.8 alpha-olefins in the terpolymer is equal to or lower than 6.5%; and (B) 20-80% of one or more propylene-based components selected from the group consisting of copolymers of propylene with one or more C.sub.4-C.sub.8 alpha-olefins, containing from more than 10% to 30% of C.sub.4-C.sub.8 alpha-olefins; terpolymers of propylene with ethylene and one or more C.sub.4-C.sub.8 alpha-olefins, containing 1-7% of ethylene and 6-15% of C.sub.4-C.sub.8 alpha-olefins. The MFR values of the precursor composition comprising the same components (A) and (B) in the above proportions (MFR (1)) is from 0.3 to 5 g/10 min, and the MFR values (MFR (2)) obtained by subjecting the precursor composition to degradation a precursor composition is from 2 to 15 g/10 min, with a ratio of MFR (2) to MFR (1) is from 2 to 20.

[0069] Alternatively, the reactor made propylene-based polyolefin can be a crystalline copolymer having: (A) 0-80% by weight of one or more propylene-based components selected from the group consisting of propylene/ethylene copolymers containing 1-7% of ethylene; copolymers of propylene with one or more C.sub.4-C.sub.8 alpha-olefins, containing 2-14% of the C.sub.4-C.sub.8 alpha-olefins; or terpolymers of propylene with ethylene and one or more C.sub.4-C.sub.8 alpha-olefins, containing 0.5-4.5% of ethylene and 2-6% of C.sub.4-C.sub.8 alpha-olefins, provided that the total content of ethylene and C.sub.4-C.sub.8 alpha-olefins in the terpolymer is equal to or lower than 6.5%; and (B) 20-100% of one or more propylene-based components selected from the group consisting of copolymers of propylene with one or more C.sub.4-C.sub.8 alpha-olefins, containing from more than 8% to 30% of C.sub.4-C.sub.8 alpha-olefins; or terpolymers of propylene with ethylene and one or more C.sub.4-C.sub.8 alpha-olefins, containing 1-7% of ethylene and 6-18% of C.sub.4-C.sub.8 alpha-olefins. The melt flow rate of this copolymer can be between 2.0 and 15.0 g/10 min.

[0070] Alternatively, the reactor made propylene-based polyolefin can be a RACO having a crystalline propylene/ethylene random copolymer having from about 4.5 wt % to about 8 wt % of ethylene, and from about 92 wt % to about 95.5 wt % of propylene. The melt flow rate of this copolymer can be between 0.3 and 15.0 g/10 min.

[0071] In yet another alternative, the reactor made propylene-based polyolefin can be a reactor made propylene-based RACO having: (A) 20-60% of a copolymer of propylene with ethylene, wherein the content of ethylene is about 1 wt % to about 5 wt % of ethylene; and, (B) 40-80% of a terpolymer of propylene with ethylene and a C.sub.4-C.sub.8 -olefin, wherein the content of ethylene is about 1 wt % to about 5 wt % and the content of the C.sub.4-C.sub.8 -olefin is about 7 wt % to 12 wt %. The total content of ethylene in the RACO is between about 1 wt % to about 5 wt %, and the total content of the C.sub.4-C.sub.8 -olefin in the RACO is between about 2.8 wt % to about 9.6 wt %. The melt flow rate of this copolymer can be between 0.3 and 15.0 g/10 min.

[0072] All of the random copolymers and terpolymers described above are exemplary and show the wide variation in the formulations that allows for the broad use of the reactor made RACO and terpolymer polyolefin resins, and the foamed extrudates in the present disclosure. In addition to the random copolymers and terpolymer formulas above, the polyolefins for the current compositions can also include any of the formulas described in EP0674991, EP1025162, and U.S. Pat. No. 6,395,831, each of which is incorporated herein in its entirety for all purposes. The polyolefins can also be prepared by any of the reactor processes described in EP0674991, EP1025162, and U.S. Pat. No. 6,395,831 as well.

[0073] In yet more embodiments, the random copolymers or terpolymer is prepared using a multi-stage gas phase polymerization process. In some embodiments, the multi-stage gas phase polymerization process is the Catalloy process from LyondellBasell (Houston, Tex.). The Catalloy process, shown in FIG. 1, utilizes a unique combination of catalysts, two or three independent fluidized bed reactors, and multiple monomer capability to expand the performance of the resulting polyolefins by delivering new functionalities. The Catalloy process can make a random copolymer or terpolymer in each gas phase reactor, creating an alloy of copolymers and/or terpolymers while in the reactors. This process allows for the incorporation of higher amounts of comonomer into the polyolefin, including two different comonomers in the same reactor, compared to conventional polypropylene production processes. The high comonomer content, as well as the presence of multiple comonomers, translates to a new combination of thermal, physical and optical properties for the resulting RACOs or terpolymers. The benefits of using the Catalloy-produced copolymers and terpolymer include the ease of processing, ability to make resins with a wide range of polymer compositions, and unique thermal properties including, but not limited to, low seal initiation temperature. As such, commercially available Catalloy polymers from LyondellBasell (Houston, Tex.) can be used in the present compositions as the base resin for the foams, including Adsyl products.

[0074] To create a foamed cellular structure using any of the above-described reactor made propylene-based RACOs or terpolymers, each base resin can be mixed with a chemical foaming agent or a physical blowing agent, and an optional nucleating agent.

[0075] The reactor made RACO or terpolymer base resins can be combined with at least one chemical foaming agent (CFA). The chemical foaming agents that are acceptable for use with the present disclosure develop gas in the resin by way of thermal decomposition or chemical reactions. In some embodiments, the CFA decomposes during the extrusion process to produce and release a gas into the extruding polymer to foam the resin. To ensure proper dispersion of the CFAs, the CFAs are in a masterbatch that uses a carrier resin that is compatible with at least one polymer or monomer in the polyolefin base resin, such as ethylene or propylene. This allows for the CFAs to create consistent cells morphologies with controlled size distributions throughout the extruded and foamed reactor made propylene-based RACO or terpolymer resins.

[0076] Many CFAs are known in the art and/or are commercially available. Exemplary organic CFAs include azo and diazo compounds (e.g. azodiacarbonamides), hexahydrophthalic acid and hydrazines, including their salts and anhydrides (e.g. sulfonylhydrazides or triazines), N-nitroso compounds, azides, sulfonyl semicarbazides, triazoles and tetrazoles, urea derivatives, guanidine derivatives, and esters. Exemplary inorganic CFAs include ammonium carbonate, and carbonates of alkali metals, including sodium bicarbonate and citric acid. The CFAs can also include mixtures of acids and metals, mixtures of organic acids with inorganic carbonates, mixtures of nitrites and ammonium salts.

[0077] At least one optional nucleating agent may also be combined with the CFA(s). In some embodiments, at least one CFA is present in the same masterbatch comprising the optional nucleating agent, or at least one CFA is present in a separate masterbatch, or the at least one CFA acts as the nucleating agent. Nucleating CFAs help with property enhancement, improved molding or extrusion productivity, and increased transparency for many polyolefins. In masterbatches with nucleating agents and multiple CFAs, at least one CFA can be the nucleating agent. Alternatively, any or all of the CFAs used in the present composition can be nucleating. Further, one or more of the CFAs in the masterbatch can be endothermic such that it does not decompose in the reactor made propylene-based RACO or terpolymer resin until the extrusion process. This is because endothermic CFAs need heat to activate that is provided by the extrusion process.

[0078] In other aspects of the present disclosure, multiple masterbatches can be mixed with the reactor made propylene-based RACO or terpolymer resin to achieve the desired cell morphology of the resulting foam. The final concentration of the masterbatch in the foamed resin may be limited to 5% of the weight of the foamed resin. Alternatively, the final concentration of the masterbatch in the foamed resin may be between 0.25 and 3 wt %.

[0079] Reactor made propylene-based RACO or terpolymer resins have a wide range of physical properties, which lead to flexible formulations when mixed with select CFAs to achieve specific cell size, cell distributions and cell stabilities. This combination allows for the composition to be fine-tuned to form a foam structure with enhanced stability and performance characteristics. Thus, the resulting foams can then have a wide range of physical properties, density reduction, cell size, cell pattern, and/or cell stability. This allows the foams to be available for a variety of applications in the e.g. automobile, shipping, food packaging industries, and the like.

[0080] The CFAs can be chosen to produce large (above 150 microns in diameter) or small cell sizes (below 120-150 microns in diameter), and a wide or narrow distribution of cell sizes. In some applications, narrow distributions of cell sizes are desirable. In some embodiments, the desired cell sizes are in a range of 25-55 microns, as these foams can be classified as fine-celled foams. However, the desired cell density will depend on the application for the foam. For instance, low cell density foams are more flexible and are better for many applications such as thermal insulation and comfort (e.g. furniture and car seating) but high cell density can be used for more rigid foams, such as energy-absorbing application, pipes, appliances, food and drink containers. Since the mechanical strength of a polymer foam can be proportional to the foam density, the application of the foam dictates the range of foam density to be produced.

[0081] In addition to cell size and density, the CFAs can be chosen to achieve certain flexibility in the resulting foamed extrudate.

[0082] Alternatively, the reactor made RACO or terpolymer base resin, in melt form, can be combined with a physical blowing agent such as CO.sub.2, N.sub.2, isobutane, or CFC-derivatives, and foamed. The process conditions for the blowing agents are controlled to tune the cellular phase, cell size, and other cell features of the resulting foam.

[0083] When using PBAs, the reactor made RACO or terpolymer base resin can also optionally be combined with a masterbatch having at least one nucleating agent. The PBA and the nucleating agent work synergistically to achieve desired cell morphology, including both large (above 150 microns in diameter) or small cell sizes (below 120-150 microns in diameter), and a wide or narrow distribution of cell sizes. As above, the final concentration of the masterbatch's in the foamed resin may be limited to 5% of the weight of the foamed resin. Alternatively, the final concentration of the masterbatch in the foamed resin may be between 0.25 and 3 wt %.

[0084] Articles of various shapes and sizes can be formed using foamed compositions comprising any of the reactor made RACO or terpolymer base resin presently disclosed.

[0085] The presently disclosed base resin compositions are exemplified with respect to the disclosure below. However, these are exemplary and the methods can be broadly applied to any reactor made propylene-based RACOs and terpolymers base resin with a high comonomer content, and chemical foaming agent or physical blowing agents.

[0086] The following description demonstrates various embodiments, and is intended to be illustrative, and not unduly limit the scope of the appended claims. Those of skill in the art should appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the disclosure herein. In no way should the following be read to limit, or to define, the scope of the appended claims.

[0087] Base polymer: A series of commercially available Catalloy random copolymer and terpolymer resins with high comonomer content from LyondellBasell, (Houston, Tex.) were extruded with a foaming agent, foamed, and analyzed per the methods described below. The examples utilized resins from the Adsyl product line. These base polymer resins were chosen as they have a wide range of comonomer type and content which translates into large number of potential applications. Further, these resins have moderate melt elasticity and melt strength, which is desirable for foam production.

[0088] The Adsyl product line includes propylene-based terpolymers formed by polymerizing propylene with a high ethylene and butene comonomer content. These polymers have superb sealing properties, good opticals, a broad operating window, and are suitable for metallization. They are also compatible with PE and PP. Additionally, the Adsyl product line also has RACO copolymers with either high ethylene or high butene content.

[0089] Together, this selection of commercially available resins provides a broad scope of thermal, physical and optical properties for investigating the applicability of the proposed methods.

[0090] Chemical foaming agents: A series of commercially available masterbatches containing at least one chemical foaming agent were obtained for combination with a propylene-base polymer. Masterbatch A (MB-A) contains an endothermic chemical nucleating and foaming agent used in a concentration of 1.5-2.25 wt %. The CFA in MB-A is also used for the creation of cells to reduce density and improve throughput in medium density extrudate. Masterbatch B (MB-B) contains an olefinic nucleating agent that was used in a concentration of 0.75-1.0 wt %. The CFA in MB-B is used to improve cell dispersion, size and uniformity in extrusion processes producing chemical foam. Masterbatch C (MB-C) contains an endothermic/exothermic blended chemical foaming agent in a concentration of 1 wt %. The CFA in MB-C is used for both injection molding and extrusion applications to create cells in medium density extrudate. Masterbatch D (MB-D) contains a chemical foaming agent at a concentration of 2.5 wt %. Masterbatch E (MB-E) contains a nucleating agent used at a concentration of 1 wt % and was combined with one of the other masterbatches described above having a CFA.

[0091] A masterbatch with at least one CFA was mixed with the resins before being extruded and foamed. The use of one nucleating chemical foaming agent is sufficient to foam the chosen base polymer, but mixes of chemical foaming agents may be desired to fine-tune the characteristics of the foamed extrudate.

[0092] Unless otherwise noted, the selected masterbatches were dry blended with the base resin before the melt stage.

[0093] CFA Foam Extrusion: A variety of sample compositions with CFAs were prepared and extruded as foamed strands for an initial analysis. The base polymer and masterbatches were dry blended and extruded without modifications to the extrusion equipment or the resin grade. The foam strand samples were then analyzed for cellular phase, cell size, and other cell features.

[0094] From the characterization results of the foam strands, certain sample compositions with CFAs were extruded as sheets. For the sheets, the base polymer and masterbatches were dry blended and extruded as multi-layer sheets (Mode 2) to produce foamed sheets that were about 40 mm thick. Certain foam sheet samples underwent further analysis for density, density reduction compared to the base polymer alone, cell size, and other cell features.

[0095] No modifications to the extrusion equipment or the resin grade were needed to produce the sample foamed sheets. FIG. 2 displays exemplary process conditions for the extrusion of a foamed sheet in this case a monolayer foamed sheet sample using the Masterbatch A. These conditions did not significantly vary for the different foamed sheets. The dashed box in FIG. 2 highlights Barrel Zone 2, which uses a higher temperature than Barrel Zones 1 and 3, to activate the chemical foaming agent.

[0096] Foam Characterization: Morphological characterization of the cellular structure of the foamed Catalloy extrudates were determined by optical microscopy and scanning electron microscopy (SEM). Foam samples were cryo-microtomed in the direction perpendicular to extrusion using a Leica MZ6 Ultramicrotome with a diamond knife at 40 C. The thin cross-sections were examined by optical microscopy (Olympus BX51 Compound Microscope) with both transmitted light and cross-polarized light. The bulk cross-sections were examined using an SEM (Hitachi S-3500N or SU8230) in high vacuum mode at accelerating voltage of 5 kV. SEM images were captured at the same low magnification (25) to allow for the whole extrudate cross-section of each sample to be included in a single image. Prior to SEM imaging, the bulk cross-section specimens were coated with Pt using a sputter coater (Emitech K550X) to eliminate charging from SEM electron beam.

[0097] Olympus Stream Essentials image software was employed to perform image analysis on SEM images where the cells displayed as dark holes are dispersed in the lighter polymer matrix. For this type of cellular morphology, the particle analysis function of the software is the most suitable means to measure the size and number of cells in each foam cross-section. To ensure accurate results, prior to image analysis, each SEM image was examined and manually corrected using Adobe Photoshop software to enhance the contrast between the cells and the solid phase. The gray value thresholds that distinguish cells from the solid phase in image analysis were adjusted based on each individual image so that the greatest number of cells were counted. To ensure consistency, no further manual editing of image detection was conducted after automatic image analysis by Stream Essentials software. The average cell size or radius, cumulative cell area distribution, and morphology of the cells (open or closed) were determined from the images.

[0098] Density measurements were made according to the standard test methods established in ASTM D792-13 using displacement by water or alcohol. The reduction in density was calculated based on the density of the base polymer for each example without any foaming agents added.

CFA Foamed Strands

[0099] Foamed strands of Adsyl 5C30F were prepared using CFAs, and analyzed for the largest reduction in density compared to the unfoamed resin and the smallest cell size. The compositions and results for the preliminary samples are shown in Table 1.

TABLE-US-00002 TABLE 1 Preliminary compositions for foamed strands NOMINAL DENSITY of CELL SOLID DENSITY DENSITY OF DIAMETER POLYOLEFIN REDUCTION EXAMPLE FOAM (g/cm.sup.3) (microns) (g/cm.sup.3) PERCENT Terpolymer Adsyl 5C30F, 2% Masterbatch A 0.50 240 0.90 44% Adsyl 5C30F, 1.5% Masterbatch A 0.55 275 0.90 39% Adsyl 5C30F, 1.5% Masterbatch 0.51 130 0.90 43% A, 1% Masterbatch B Adsyl 5C30F, 1.5% Masterbatch 0.54 165 0.90 40% A, 1% Masterbatch E Adsyl 5C30F, 1% Masterbatch C 0.40 400 0.90 56% Adsyl 5C30F, 1% Masterbatch 0.36 335 0.90 60% C, 1% Masterbatch B Adsyl 5C30F, 1% Masterbatch 0.43 305 0.90 52% C, 1% Masterbatch E

[0100] The Adsyl 5C30F samples with 1.5% MB-A combined with 1% of MB-B or MB-E in Table 1 were chosen for additional characterization, including image analysis. The results for the addition analysis are shown in Table 2.

TABLE-US-00003 TABLE 2 Characterization of select foamed strands Average Relative Cellular Fraction of Cell Average Standard Strand Foam Strand MB-A MB-B MB-E Phase Cellular Cell Diameter Cell area Deviation Diameter Sample No. Polyolefin (wt %) (wt %) (wt %) (m.sup.2) Phase (%) Count (m) (m.sup.2) (%) (m) S-2017- Adsyl 1.5 1 2463464.07 41.60 333 97.05 7397.79 157.69 2745.99 005158 5C30F S-2017- Adsyl 1.5 1 2174788.98 36.61 273 100.71 7966.26 137.87 2750.24 005159 5C30F

[0101] From the image analysis, the selected extruded strands in Table 2 were found to have circular cross-sections, with diameter measurements in the 2.75 mm range. These foamed compositions show slight variations in rigidity and size, reflecting different foaming agent compositions and levels of foam expansion.

[0102] All of the optical images were taken with the lowest possible magnifications from the microscope so the largest areas of the foam cross-sections can be included. The cellular morphology varied from strand sample to strand sample. In general, the cell sizes were smaller near the strand surface where the polymer melts experience the higher shear forces during processing. The sizes of the cells gradually increase with the distance from the surface. Near the core, many small cells appeared to aggregate to form a large cell of an irregular shape due to the low shear force of the polymer melt, making it incapable of dispersing individual cells during either the initial bubble formation, or due to the high extensional force of the melt causing the cell rupture during cell growth. In some samples, the observed larger cells may be a result of the disappearance of cell walls that separate individual cells. However, cell walls tend to collapse because they are too thin to withstand low temperature microtoming that is used to prepare the samples for analysis.

[0103] SEM was used to confirm the variations of cell sizes with the distance from the strand surface and to observe the cell aggregations. Some of the aggregates formed clusters of cells with the existence of solid walls between neighboring cells. Others formed larger cell aggregates of irregular shapes. Many of the cells in the foam strand samples were non-spherical. A foaming polymer melt tends to be stable when the gas bubbles were strictly spherical in shape to minimize the interfacial area and the capillary pressure; however, the bubbles become elongated in the extrusion direction, resulting in the non-uniform distribution of the mechanical stresses during foaming. The gas bubbles would tend to expand along the directions of minimum local stress to produce the anisotropic shapes of cells. In addition, the degree of freedom is higher in the extrusion direction during foaming because it has less geometric constraints.

[0104] The SEM images did not show the enclosure of these hemispherical cells. Although SEM images can show individual cells within the large cell aggregates that are connected to each other, there is no morphological evidence to characterize any of these foam samples as open-cell foam in overall view.

[0105] Cells were not uniformly dispersed in the solid polymer. For this type of foam, cell size analysis provides comprehensive and valuable characteristics of foam structures to differentiate various foam samples. Some morphological parameters, such as wall thickness and cell packing geometry, were not measurable or meaningful.

[0106] Table 2 lists results of cell counts, average cell sizes, and relative standard deviations obtained by Stream Essentials image software through particle analysis. The sizes of cellular phase and area fractions of cellular phase were calculated based on these results and measured strand diameters. The cell phase area fractions for these samples are below 42%.

[0107] The use of Masterbatch C appeared to achieve the largest reduction in the resin's density, with a reduction of 52% or higher, whereas Masterbatch A had a range between 39 and 44%.

[0108] The cell size, however, was smallest when combining Masterbatch A with a second Masterbatch, showing cell size as low as 130 microns in diameter. These results illustrate the fine-tuning of the foaming agents in the masterbatches to elicit desired properties from each base polymer. As shown in Table 2, the average cell sizes fall within the range of about 97 to 100 m of the equivalent diameter, thus they are classified as small-celled foams.

[0109] The results of cell size measurements were further analyzed for size distribution. As displayed in FIG. 3A (cumulative number of cells vs. cell radius) and FIG. 3B (cell size histograms), and also shown in Table 2, these foam strand samples are not symmetric. The curves in FIG. 3A indicate that the foaming agent composition is the source of major differences in cell formation. The range of variations within each pair of foams produced from the same resin was relatively broad. The cell dimension detected most frequently in each foam sample is in the smallest particle size range. This type of particle size distribution results in a relatively high standard deviation in cell size measurements.

[0110] In conclusion, the base resins used in the strand examples were able to form foam. This foamability was unexpected for two reasons. First, reactor made propylene-based RACO and terpolymers such as Adsyl base resins are not heterophasic copolymers with a semi-crystalline matrix component and a partially amorphous bipolymer component. These two components were considered to be necessary to form a foam. However, the present examples show that both components are not needed. Second, the reactor made propylene-based RACO and terpolymer base resin used in the present compositions have a lower melt strength when compared to polyolefins with a high molecular weight bipolymer component. A high melt strength is needed to foam polyolefins, thus making these polymers poor foaming candidates. However, the present compositions were capable of producing foamed strands. Further, the selected foamed strands compositions were small-celled foams that had smaller cells seen near the surface while larger cells of irregular shapes are located near the core. It is generally known in the art that small cell structures tend to have a smaller negative impact on mechanical properties than large cell structures. The density reductions were up to 70% when compared to the base resin.

[0111] These results show that not only are the Catalloy reactor made RACO and terpolymers polyolefins with high comonomer content capable of being foamed but that the character of the foams (e.g. cell size, density reduction, etc) can be tuned by the choice of chemical foaming agent(s) and/or the addition of one or more nucleating agents. Further, due to the breadth of possible applications for foamed polyolefins, perceived imperfections for certain applications, such as the foamed strands with inconsistent cells sizes, can still find many uses.

CFA Foamed Sheets

[0112] Based on the results from the foamed strand tests, additional Adsyl grades were used to prepare CFA foamed sheets. The compositions were foamed as either single layer sheets (mode 1) or as multi-layered sheets (mode 2). Like the foamed strands, Masterbatch A and Masterbatch B were utilized for the CFA foamed sheets. The foam sheets were produced by dry-blending a combination of Masterbatch A and Masterbatch B with the selected base Adsyl resin, and extruding with an 8-inch flat die to prepared foam sheets with a target thickness of 40 mil (about 1 mm).

[0113] The compositions of each CFA foamed sheet of different Adsyl grades, and the results of the density testing according to ASTM D792, are shown in Tables 3 and 4. Table 3 displays the results for the multilayer samples (Mode 2), with FIG. 4 showing the cumulative cell area distribution for the each composition, with the density labeled. The results for the monolayer samples (Mode 1), are given in Table 4 and FIG. 5.

TABLE-US-00004 TABLE 3 Exemplary Adsyl foamed sheets Density Average Sample MB-A MB-B Density reduction Density Cell radius No. (wt %) (wt %) Mode (g/cm.sup.3) (%) (lb/ft.sup.3) (microns) Adsyl 7416XCP Unfoamed 0 0 0.900 57 Control K17218 1.75 0 2 0.7154 21 44.7 15 K17219 1.75 0.75 2 0.7086 21 44.2 18

[0114] The chemical foaming agents were able to reduce the density for each of the tested base polymers resins. A good range of reduction, up to about 25%, was experienced with these foamed sheet samples.

[0115] Table 3 displays the results using Adsyl 7416XCP that was extruded as a multilayer sheet. Sample No. K17218 produced foam with a density of 44.7 lb/ft3, a 21% reduction. Sample No. K17219 used the same concentration of Masterbatch A but added 0.75 wt % of Masterbatch B. This composition resulted in a comparable density reduction of 21%, too. Average cell radius for Example No. K17218 was 15 microns while Example No. K17219 attained a cell radius of 18 microns.

[0116] Additional examples using Adsyl 7416XCP were foamed as single layer sheets. The results in Table 4 show how changes in the Masterbatch compositions and/or concentrations can affect the features of the foam. Example No. K19011 had the same masterbatch composition as No. K17219, and similar results were seen between Mode 1 and 2. However, increasing the content of Masterbatch A for Example No. K19012 increased the density reduction by about 6%. Thus, the concentration of Masterbatch A appears to have a greater influence on the density reduction for Adsyl 7416XCP foams. Similar results were seen with the Adsyl 5C30F foams, wherein the addition of Masterbatch B did not increase the density reduction.

TABLE-US-00005 TABLE 4 Exemplary Adsyl foamed sheets Foam Solid Density Average Cell Sample MB-A MB-B Density Density reduction Density Diameter No. (wt %) (wt %) Mode (g/cm.sup.3) (g/cc) (%) (lb/ft.sup.3) (microns) Adsyl 5C30F K19013 1.5 0 1 0.8007 0.9 11 50 28 K19014 1.5 0.75 1 0.8063 0.9 10 50 29 K19015 2.25 0.75 1 0.7019 0.9 22 44 28 Adsyl 6C30F K19007 1.5 0 1 0.8084 0.9 10 50 25 K19008 1.5 0.75 1 0.7438 0.9 17 46 27 K19009 2.25 0.75 1 0.668 0.9 26 42 28 Adsyl 3C30F-HP K19016 1.5 0 1 0.7988 0.9 11 50 36 K19017 1.5 0.75 1 0.784 0.9 13 49 33 K19018 2.25 0.75 1 0.7589 0.9 16 47 24 Adsyl 7416XCP K19011 1.75 0.75 1 0.7286 0.9 19 45 26 K19012 2.25 0.75 1 0.6726 0.9 25 42 28

[0117] As explained above, the Adsyl resins are not heterophasic copolymers with a semi-crystalline matrix component and a partially amorphous bipolymer component. Second, the reactor made RACO and terpolymers do not have long chains or high molecular weight component. As such, these polyolefins have a lower melt strength when compared to polyolefins with these features. Thus, these resins were considered a poor choice for foaming. However, based on the foaming results obtained from the initial examples, different grades of this reactor made random copolymers and terpolymers were mixed with varying combinations of masterbatches and foamed as monolayer sheets. The results in Table 4 illustrate how the different grades of these reactor made random copolymers and terpolymers unexpectedly foamed with changes to the masterbatches.

[0118] The foamed compositions produced using Adsyl 6C30F as a base resin displayed an increase in cell size radius as the amount of Masterbatch A increased, as did Adsyl 7416XCP. In contrast, Adsyl 3C30F-HP displayed a decrease in cell radius with increasing Masterbatch A. The Adsyl grades showed density reduction as the amount of Masterbatch A increased and as Masterbatch B was added.

[0119] As before, SEM was used to confirm the variations of cell sizes with the distance from the monolayer surface of the exemplary sheets in Table 4, and to observe the cell aggregations. Some of the aggregates formed clusters of cells with the existence of solid walls between neighboring cells. Others formed larger cell aggregates of irregular shapes. Many of the cells in the foam monolayer samples were non-spherical due to becoming elongated during the extrusion process.

[0120] The cell diameters were also reduced down to about 25-55 microns, thus these foams can be classified as small-celled foams. Further, each sample was predominantly closed-cell foams as the foam cells are isolated from each other and cells are surrounded by complete cell walls. This desirable feature is helpful in selecting applications for the foamed compositions. The foam samples also showed variations of cell size and shape with the distance from the foam surface. Smaller cells were seen near the surface while larger cells of irregular shapes were located near the core, suggesting that the foam structure depends strongly on the rheological behavior of the base resin and the equipment used for foaming.

[0121] The results from each of the foam samples demonstrate that multiple Adsyl grades can be successfully foamed as sheets or strands using chemical foaming agents. Similarly, foaming abilities with PBAs, with and without nucleating agents, are expected to be equally successful. The foamed extrudates displayed a large range of properties, allowing for a broad amount of applications. Further, the selection of chemical foaming agents or combinations thereof, and nucleating agents, can be utilized to tune the features of the foam extrudate for select applications. Additionally, it was noted that the foaming of the different reactor made random copolymers and terpolymers did not need modification to the hardware of the system, which could reduce down time and capital costs.

[0122] The following references are incorporated by reference in their entirety.

[0123] ASTM D792-13, Standard Test Methods for Density and Specific Gravity (Relative Density) of Plastics by Displacement

[0124] ASTM D 1238L, Standard Test Method for Melt Flow Rates of Thermoplastics by Extrusion Plastometer

[0125] EP0674991

[0126] EP1025162

[0127] U.S. Pat. No. 6,395,831