This application claims the benefit of European Patent Application

EP17382124.0 filed 10 March, 2017

The present disclosure relates to polymeric foams, particularly to closed-cell polymeric foams, and processes for their preparation.

BACKGROUND ART

Microcellular foams were first described at Massachusetts Institute of

Technology, USA, in the early eighties, in response to a challenge by food and film packaging companies to reduce the amount of polymer used in their industries. As most of these applications used solid, thin-walled plastics, reducing their densities by conventional foaming processes that produced bubbles larger than 250 microns was not feasible due to excessive loss of strength. Thus the idea to create microcellular foam was born, where there could be, for example, 100 bubbles across 1 mm thickness, and expect to have a reasonable strength for the intended applications.

It is currently well known that most of the physical properties of microcellular foams are superior to those of conventional foams with higher cell sizes. Due to this reason in the last years the idea of reducing even more the cell size to create materials with improved properties has appeared and due to this sub- microcellular foams and nanocellular foams have been developed.

Reaching very high cell density is not a simple task and only a few patents have been disclosed up to know. For thermoplastic polymers, three main strategies can be distinguished.

The first strategy is based on an homogeneous nucleation process in which a high gas uptake is needed and due to this, extreme processing conditions are used (very high pressures, very high pressure drop rates or even low saturation temperatures). In addition, polymers with high affinity to the gas phase are used.

A second approach is the use of nanoparticles as nucleating agents for the cells. This strategy is based on an heterogeneous nucleation process.

The third approach is the use of block copolymers creating a disperse phase (micelles) in which the cells are nucleated. This second phase has a high affinity for the gas phase and the number micelles should be high enough to produce submicrocellular and nanocellular foams. This strategy is also based on an heterogeneous nucleation process.

In addition to the previous processes, continuous production by extrusion of these submicrocellular and nanocellular polymers has also been described.

The above mentioned strategies have several drawbacks. In the case of the one based on an homogeneous nucleation process the main issue is that it is necessary to produce the foams using very high pressures, very high pressure drop rates and/or saturation temperatures below 0°C. Due to this, it would be really difficult to up-scale this technology to produce these materials by high output production process such as extrusion foaming.

In the case of the one based on a heterogeneous nucleation process by using nanopartides there are two main problems. The first one is to achieve the required degree of dispersion of the nanopartides in the polymer matrix, more than 10 ¹¹ particles/cm ³ . The second one is that in general it is also needed the use of high pressures and high pressure drop rates to obtain the number of cells required.

Finally, in the strategy based on the use of block copolymers the main issue is that the block copolymers used need to have several characteristics:

possibility of creating by self-assembly micelles with a small size able to reach the required number of more than 10 ¹¹ micelles/cm ³ , the micelles should have a high affinity with the gas phase, in addition the micelles should have a lower glass transition temperature than the polymer matrix. These requirements restrict, in a significant way, the number of systems that could be used to produce microcellular and nanocellular foams by using this strategy.

None of the previous methods allow obtaining submicrocellular and nanocellular foams using processing conditions compatible with industrial process and using raw materials easily available in which the dispersion of the second phase (the one used to nucleate the cells ) is not an issue.

Some examples of thermoplastic particle foams obtained from two

incompatible thermoplastic polymers are known in the art. Thus, for example in EP2144959 it is described thermoplastic particle foams wherein the cell membranes have a nanocellular or fibrous structure, and wherein the polymer matrix comprises a continuous phase which is rich in styrene polymer and a disperse polyolefin-rich phase. It is mentioned that the polymer mixture can be produced by mixing the two incompatible thermoplastic polymers in an extruder.

Document US201 1287929 discloses foam compositions having an open-cell morphology, with an average cell size in the micro- / macrocellular range (650-1400 μιτι). Polymeric foams disclosed in this document are prepared by chemical foaming processes with peroxide as reticulant agent, wherein the examples therein disclosed have a polyacrylate polymer component content of 56 parts per hundred rubber and polyolefin polymer content of 44 parts per hundred rubber.

Document US20170130023 refers to a method for producing open-cell polymethyl methacrylate (PMMA) polymer nanofoams

In view of the above, a need still exists in the state-of-art for providing a new submicrocellular and nanocellular closed-cell foams and methods of preparation thereof which are reliable and industrially scalable.

SUMMARY The present disclosure relates to closed-cell polymeric foams having a polymer matrix which comprises a continuous polymer phase and a disperse polymer phase. The continuous polymer phase comprises at least one acrylate polymer selected from a polyacrylate polymer, a polyalkylacrylate polymer and mixtures thereof in a concentration of at least 90 % w/w of the total continuous polymer phase weight; and the disperse polymer phase comprises at least a polyolefin polymer in a concentration of at least 90 % w/w of the total disperse polymer phase weight; the amount of continuous polymer phase is comprised of from 80 % w/w to 99.8 % w/w of the total polymer matrix.

Surprisingly, the closed-cell polymeric foams of the present disclosure show an improvement in the mechanical properties in comparison with other polymeric foams of the state of the art, particularly, the closed-cellpolymeric foams show impact resistance, glass transition temperature, and storage modulus properties within unexpected ranges which simultaneously are not present in any of the polymeric foams of the prior art. The mechanical properties such as toughness and strain at break are also improved, this enables their utilization as lightweight structural support, and in several areas such as catalysis, thermal insulation, sound insulation, electromagnetic shielding and tissue engineering. In a second aspect, the present disclosure provides a process for producing the closed-cellpolymeric foams herein disclosed, which comprises

a) preparing a polymer mixture having a continuous phase and a disperse phase, the continuous phase comprising at least one of a

polyacrylate polymer, a polyalkylacrylate polymer and mixtures thereof, and the disperse phase comprising at least a polyolefin polymer,

b) impregnatig the mixture with a blowing agent to produce an expandable polymeric mixture;

c) foaming the expandable polymeric mixture to produce the

submicrocellular polymeric foam;

wherein the foaming step is performed at a saturation pressure in the range of

1 -30 MPa and at a temperature in the range of 50-120 °C.

With regard to the specific conditions for carrying out the process of the invention, the skilled person would know how to adjust the parameters of each of the steps indicated above in the light of the description and examples of the present invention.

Furthermore, in a third aspect of present disclosure, it is provided a closed- cell polymeric foam having a polymer matrix comprising a continuous polymer phase and a disperse polymer phase; the continuous polymer phase comprising at least one of a polyacrylate polymer, a polyalkylacrylate polymer and mixtures thereof in a concentration of at least 90 % w/w of the total continuous polymer phase weight; and the disperse polymer phase

comprising at least a polyolefin polymer in a concentration of at least 90 % w/w of the total disperse polymer phase weight; the amount of continuous polymer phase is comprised of from 80 % w/w to 99.8% w/w of the total polymer matrix, obtainable by the process of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which:

Fig. 1 . SEM micrographs of the cellular structure of several foams produced after CO ₂ saturation at 25°C, at 30MPa (Fig. 1A), 10 MPa (Fig. 1 B) and 5MPa (Fig. 1 C) from neat polyalkylacrylate (PMMA, Comparative example CE1 Table I).

Fig. 2. SEM micrographs of the cellular structure of several foams produced after CO ₂ saturation at 25°C, at 30MPa (Fig. 2A), 10 MPa (Fig. 2B) and 5MPa (Fig. 2C) from a polyalkylacrylate/polyolefin mixture (PMMA/EBA, Example E1 Table I).

Fig. 3. SEM micrographs of the cellular structure of several foams produced after CO ₂ saturation at 25°C, at 30MPa (Fig. 3A), 10 MPa (Fig. 3B) and 5MPa (Fig. 3C) from a polyalkylacrylate/polyolefins mixture (PMMA/EBA-EVOH, Example E2 Table I).

Fig. 4. SEM micrographs of the cellular structure of several foams produced after CO ₂ saturation at 10MPa, at 25°C (Fig. 4A), 75°C (Fig. 4B) and 90°C (Fig. 4C) from neat polyalkylacrylate (PMMA, Comparative Example CE1 Table I).

Fig. 5. SEM micrographs of the cellular structure of several foams produced after CO ₂ saturation at 10MPa, at 25°C (Fig. 5A), 75°C (Fig. 5B) and 90°C (Fig. 5C) from a polyalkylacrylate/polyolefin mixture (PMMA/EBA, Example E1 Table I).

Fig. 6. SEM micrographs of the cellular structure of several foams produced after CO ₂ saturation at 10MPa, at 25°C (Fig. 6A), 75°C (Fig. 6B) and 90°C (Fig. 6C) from a polyalkylacrylate/polyolefins mixture (PMMA EBA-EVOH, Example E2 Table I). Wherein PMMA refers to poly(methylmethacrylate), EBA refers to ethylene- butyl acrylate and EVOH refers to ethylene-vinyl alcohol.

DETAILED DESCRIPTION For the purposes of the invention, any ranges given include both the lower and the upper end-points of the range. Ranges given, such as temperatures, times, sizes, concentrations, and the like, should be considered approximate, unless specifically stated. As it is generally accepted in the art, foams are defined as materials containing gaseous voids surrounded by a denser matrix, which is usually a liquid or solid. Depending on the composition, cell morphology, and physical properties, polymer foams can be categorized as rigid or flexible foams.

According to the size of the foam cells, polymer foams can be classified as macrocellular (with cell sizes higher than 1000 μιτι), microcellular (with cell sizes comprised from 1 μιτι to 1000 μιτι), submicrocellular (with cell sizes comprised from 30 nm to 3 μιτι), and nanocellular (with cell sizes comprised from 1 nm to 100 nm). As noted, an acceptable overlapping in the values of the different classification is generally accepted. That overlapping is due to the term "cell size" is generally linked to a distribution of cell sizes, which may be narrow or broad. Thus, a "submicrocellular cell size" must be understood as an average cell size which falls within a distribution of cell size around 1 μιτι. Polymer foams can also be defined as either closed-cell or open-cell foams.

In closed-cell foams, the voids are isolated from each other and cavities are surrounded completely by the cell wall. In open-cell foams, cell walls are broken and the structure consists mainly of ribs and struts. Generally, closed cell foams have lower permeability, leading to better insulation properties. Closed cell foams are usually characterized by their rigidity and strength, in addition to the high R-value (Resistance to heat flow). Relative density (p _re i). It is defined as the density of the foamed material (p _f ) divided by the density of the solid material before foaming (p _s ). Density of solid samples was measured with a gas pycnometer (Mod. AccuPyc II 1340, Micromeritics), and density of foamed samples (p _f ) was determined with using the water-displacement method based on Archimedes' principle. A density determination kit for an AT261 Mettler-Toledo balance has been used for this purpose.

Porosity (P). It is volume fraction (in percentage) of the gas phase. It is calculated using the following equation:

Expansion ratio. It is defined as the inverse of the relative density (p _re i).

Cell density (N _v ). It is defined as the number of cells per cubic centimeter in the foams. This number was calculated using Kumar's theoretical

approximation (Kumar V, Suh NP. Polym Eng Sci 1990; 30(20):1323-1329). In this method, no direct measurements of cell dimensions over SEM

micrographs are required, only the micrograph area (A) in cm ² and the total number of cells (n) contained in the micrograph are measured. From these values N _v can be calculated using the following equation:

Cell nucleation density (N ₀ ): It is defined as number of cells per cubic centimetre of the unfoamed solid material. This parameter can be calculated using the following equation:

Average cell size (φ): The three dimensional average cell size was obtained with a specialized software (Pinto J, Solorzano E, Rodriguez-Perez MA, de Saja JA. J Cell Plast 2013;49(6):555-575) based on ImageJ/FIJI (Abramoff MD, Magalhaes PJ, Ram SJ. Biophot Int 2004;1 1 (7):36-42). This software provides the cell size distribution, the average cell size (φ), the standard deviation of the cell size distribution (SD), the cell anisotropy ratio

distribution, the average cell anisotropy ratio, the asymmetry coefficient (AC), the cell density N _v and the cell nucleation density (N ₀ ). All these parameters are defined as it is described in Pinto J, Solorzano E, Rodriguez-Perez MA, de Saja JA. J Cell Plast 2013;49(6):555-575 Anisotropy ratio is defined as the ratio between the average cell size in two perpendicular directions.

Potential nucleation density is defined as the ratio between the number of nucleants and the volume of an individual nucleant. For a nucleating agent it is calculated using the following equation: [Spitael, P.; Macosko, C. W.;

Mcclurg, R. B.. Macromolecules 2004, 37, 6874-6882, Zhai, W.; Yu, J.; Wu, L; Ma, W.; He, J.. Polymer 2006, 47, 7580-7589)

Nucleants ω p _c

Where ^ω ρ is the nucleating agent content, Pc is the density of the blend under study (polymer containing the nucleating agent), ^p p is the density of the nucleating agent and ^v p is the volume of one individual particle of the nucleating agent.

Nucleation efficiency for a given nucleating agent is defined using the following equation:

Ce ll nucleation density (¾}

Nucleation Efficiency = r

" ^* Po tential nucleation density

It accounts for the efficiency of the nucleating agent. A value of 1 for this parameter means that each nucleating particle is able to create one cell in the final foam. A value much lower than one means that the nucleating agent has a poor efficiency and/or that processes that reduce the number of cells in the foam such as coalescence or coarsening are playing a key role during the production of the material.

Degeneration Ratio: It is defined as the inverse of the Nucleation Efficiency. In the context of the present disclosure, the term "percentage (%) by weight" refers to the percentage of each ingredient of the combination or composition in relation to the total weight.

The term "polymer", unless indicated otherwise, refers to both homopolymer and copolymer. Unless otherwise indicated, "copolymer" includes block copolymer, graft copolymer, alternating copolymer and random copolymer.

The term "alkylacrylate monomer" refers to derivatives of alkylacrylic acid and the term "acrylate monomer" referes to derivatives of acrylic acid. Thus the term "polyacrylate polymer" refers to polymerized acrylate monomers, whereas the term "polyalkylacrylate polymer" refers to polymerized

alkylacrylate monomers. A "alkylacrylate" polymer can be a copolymer containing both alkylacrylate monomers and acrylate monomers and as such can be both an alkylacrylate polymer and an acrylate polymer.

The polymeric foams of the present disclosure have a polymer matrix which comprises a continuous polymer phase and a disperse polymer phase. In this context, the continuous polymer phase defines a plurality of cells therein. In accordance with some embodiments of the present disclosure, the closed- cell polymeric foams may show an average cell size in the range of submicrocellular cell sizes, i.e. ranging from 30 nm to 3 μιτι; in some embodiments the average cell size ranges from 300 nm to 2.8 μιτι; in some other embodiments, the average cell size ranges from 600 nm to 2.75 μιτι. In accordance with some embodiments, the average cell size ranges from 500 nm to 2.6 μιτι.

In accordance with some embodiments of the present disclosure, both the continuous polymer phase and the disperse polymer phase may contain one or more additives. Therefore, the additives may be present in the continuous polymer phase, in the disperse polymer phase or in both phases

simultaneously. Preferably the additives are present in both polymer phases simultaneously, thus allowing an homogeneous distribution thereof in the polymeric foam.

Several additives may be used such as fillers (for example, talc, silica, titania, magnesia, calcium carbonate, carbon black, graphite, magnesium silicate or clays such as kaolinite and montmorillonite); flame retardants (for example, halogenated flame retardants, such as hexabromocyclododecane and brominated polymers,or phosphorous flame retardants such as

triphenylphosphate, dimethyl methylphosphonate, red phosphorous or aluminium diethyl phosphinate); acid scavengers (for example, calcium stearate, magnesium oxide, zinc oxide, tetrasodium pyrophosphate or hydrotalcite); antioxidants (for example, sterically hindered phenols, phosphites and mixtures thereof ); pigments and blowing agent stabilizers. Sterically hindered phenols are well known in the art and refer to phenolic compounds which contain sterically bulky radicals, such as tert-butyl, in close proximity to the phenolic hydroxyl group thereof. In particular, they may be characterized by phenolic compounds substituted with tert-butyl groups in at least one of the ortho positions relative to the phenolic hydroxyl group. In a particular embodiment, the sterically hindered phenol has tert-butyl groups in both ortho-positions with respect to the hydroxyl group. Representative hindered phenols include pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4- hydroxyphenyl)propionate), 1 ,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4- hydroxybenzyl) benzene, n-octadecyl-3(3,5-di-tert-butyl-4-hydroxyphenyl) propionate, 4,4'-methylenebis(4-methyl-6-tert-butylphenol), 4,4'-thiobis(6-tert- butyl-o-cresol), 6-(4-hydroxyphenoxy)-2,4-bis(n-ocytlthio)-1 ,3,5-triazine, 2,4,6- tris(4-hydroxy-3,5-di-tert-butyl-phenoxy)-1 ,3,5-triazine, di-n-octadecyl- 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, 2-(n-octylthio)ethyl-3,5-di-tert- butyl-4-hydroxybenzoate, and sorbitol hexa-(3,3,5-di-tert-butyl-4-hydroxy- phenyl) propionate.

In accordance with an embodiment, the continuous polymer phase comprises at least one of a polyacrylate polymer, a polyalkylacrylate polymer and mixtures thereof, in combination with one or more additives. In a particular embodiment, the continuous polymer phase comprises at least one of a polyacrylate polymer, a polyalkylacrylate polymer and mixtures thereof in a concentration comprised from 90 to 99.9 % w/w of the total continuous polymer phase weight, preferably from 95 to 99.8 % w/w of the total continuous polymer phase weight, yet more preferably from 97 to 99.7 % w/w of the total continuous polymer phase weight; the rest being additives such as fillers, flame retardants, acid scavengers, antioxidants, pigments and blowing agent stabilizers; being the sum total of components of the continuous polymer phase 100% w/w.

In accordance with an embodiment, the disperse polymer phase comprises at least a polyolefin polymer in combination with one or more additives. In a particular embodiment, the disperse polymer phase comprises at least a polyolefin polymer in a concentration comprised from 90 to 99. 9 % w/w of the total disperse polymer phase weight, preferably from 95 to 99.8 % w/w of the total disperse polymer phase weight, yet more preferably from 97 to 99.7 % w/w of the total disperse polymer phase weight; the rest being additives such as fillers, flame retardants, acid scavengers, antioxidants, pigments and blowing agent stabilizers; being the sum total of components of the disperse polymer phase 100% w/w.

In a particular embodiment, the composition of the invention comprises, either in the continuous polymer phase, in the disperse polymer phase or in both the continuous and the disperse polymer phase simultaneously, from 0.01 to 0.3 % w/w, preferably 0.1 -0.15 % w/w of at least one antioxidant selected from sterically hindered phenols, aromatically substituted phosphites and mixtures thereof. In an embodiment, the antioxidant is a mixture of a sterically hindered phenol and an aromatically substituted phosphite, e.g. a mixture of

pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) and tris(2,4-di-tert-butylphenyl)-phosphite.

In accordance with an embodiment of the present disclosure, the disperse polymer phase comprises at least a homopolymer or copolymer of ethylene or a homopolymer or copolymer of propylene having a minimun content of ethylene or propylene of 50 % w/w based on the total of the disperse polymer phase. In accordance with a particular embodient, the disperse polymer phase comprises an homopolymer or copolymer of ethylene having a minimun content of ethylene of 50 weight percent based on the total of the disperse polymer phase. Preferably, the homopolymer or copolymer of ethylene have a minimun content of ethylene of 55 % w/w; yet more preferably 60 % w/w; still more preferably 65 % w/w: being particularly preferably 70 % w/w. Examples of suitable copolymers of ethylene include ethylene-vinyl acetate (EVA), ethylene-butyl acrylate (EBA), ethylene-vinyl-alcohol (EVOH) copolymers and mixtures thereof (EBA-EVOH and EVA-EVOH) and low density polyethylene (LDPE) or linear low density polyethylene (LLDPE). Examples of LDPE or LLDPE polymers are ethylene-propylene copolymers, ethylene-butene copolymers, ethylene-hexene copolymers, and ethylene- octene copolymers.

In accordance with another preferred embodiment, the disperse polymer phase comprises an homopolymer or copolymer of propylene having a minimun content of propylene of 50 weight percent based on the total of the disperse polymer phase. Preferably, the homopolymer or copolymer of propylene have a minimun content of ethylene of 55 % w/w; yet more preferably 60 % w/w; still more preferably 65 % w/w: being particularly preferably 70 % w/w.

Examples of suitable copolymers of propylene include heterophasic or impact copolymers, plastomers and propylene-ethylene-butene terpolymers.

In the context of the present disclosure, heterophasic copolymers are copolymers having polypropylene homopolymer as a continuous phase and a disperse phase of ethylene-propylene rubber which shows the following properties: Flexural Modulus higher than700 MPa (UNE-EN ISO 178 standard method) and Charpy Notched Impact Strength (23°C) comprised from 3KJ/m ² and 70 KJ/m ² (UNE-EN ISO 179/1 standard method).

In the context of the present disclosure, the term terpolymer refers to polymers having two co-monomers ramdonly distributed showing the following properties: Flexural Modulus lower thanl 100 MPa (UNE-EN ISO 178 standard method) and Charpy Notched Impact Strength (23°C) comprised from 3KJ/m ² and 50 KJ/m ² (UNE-EN ISO 179/1 standard method).

In the context of the present disclosure, the term plastomer refers to a polymer having a co-monomer higher than 5 % w/w randomly distributed showing the following properties: Flexural Modulus <700 MPa (UNE-EN ISO 178 standard method) and Charpy Notched Impact Strength (23°C) comprised from 6KJ/m ² and 70 KJ/m ² (UNE-EN ISO 179/1 standard method).

In accordance with an embodiment of the present disclosure, the continuous polymer phase comprises at least one of a polyacrylate polymer, a

polyalkylacrylate polymer and mixtures thereof. Examples of suitable polyalkylacrylate and polyacrylate polymers include poly(methylmethacrylate) (PMMA), poly(ethylmethacrylate) (PEMA), poly(butylmethacrylate) (PBMA), poly(methylacrylate) (PMA), poly(ethylacrylate) (PEA), poly(butylacrylate) (PBA), copolymers of methylmethacrylate and/or ethylmethacrylate with methylacrylate, ethylacrylate, butylacrylate, butylmethacrylate, acrylic acid, methacrylic acid, vinyl acetate or acrylonitrile. Preferably, the

polyalkylacrylate polymer is PMMA. Particularly preferred examples of mixtures are PMMA/PMEA, PMMA/PMBA, PMMA/PMA, PMMA/PBA and PMMA/PEA.

The continuous polymeric phase may contain a mixture of one or more polyalkylacrylates; or a mixture of one or more polyacrylates and one or more polyalkylacrylates; or alternatively a mixture of one or more polyacrylates.

In accordance with a preferred embodiment of the present disclosure, the amount of continuous polymer phase is comprised of from 80 % w/w to 99.8 % w/w of the total polymer matrix; yet more preferably from 85 % w/w to 99.5 % w/w; still more preferably frorm 90 % w/w to 98 % w/w.

In accordance with a particularly preferred embodiment of the present disclosure, the continuous polymer phase comprises at least one of a polyacrylate polymer, a polyalkylacrylate polymer and mixtures thereof selected from poly(methylmethacrylate) (PMMA), poly(ethylmethacrylate) (PEMA), poly(butylmethacrylate) (PBMA), poly(methylacrylate) (PMA), poly(ethylacrylate) (PEA), poly(butylacrylate) (PBA), copolymers of methylmethacrylate and/or ethylmethacrylate with methylacrylate,

ethylacrylate, butylacrylate, butylmethacrylate, acrylic acid, methacrylic acid, vinyl acetate or acrylonitrile, in a concentration comprised from 90 to 99.9 % w/w of the total continuous polymer phase weight, preferably from 95 to 99.8 % w/w of the total continuous polymer phase weight, yet more preferably from 97 to 99.7 % w/w of the total continuous polymer phase weight; the disperse polymer phase comprises a copolymer of ethylene selected from ethylene- vinyl acetate (EVA), ethylene-butyl acrylate (EBA), ethylene-vinyl-alcohol (EVOH) copolymers and mixtures thereof (EBA-EVOH and EVA-EVOH) and low density polyethylene (LDPE) or linear low density polyethylene (LLDPE), in a concentration comprised from 90 to 99.9 % w/w of the total disperse polymer phase weight, preferably from 95 to 99.8 % w/w of the total disperse polymer phase weight, yet more preferably from 97 to 99.7 % w/w of the total disperse polymer phase weight; and wherein the amount of continuous polymer phase is comprised of from 80 to 99.8% w/w of the total polymer matrix, preferably from 82 to 99.8 % w/w, yet more preferably from 85 % w/w to 99.5 % w/w, even more preferably from 90 to 98 % w/w of the total polymer matrix.

In accordance with a particular preferred embodiment of the present disclosure, the continuous polymer phase comprises at least one of poly(methylmethacrylate) (PMMA), poly(ethylmethacrylate) (PEMA), poly(butylmethacrylate) (PBMA), poly(methylacrylate) (PMA),

poly(ethylacrylate) (PEA) and poly(butylacrylate) (PBA) in a concentration comprising from 95 % to 99.8 % w/w of the total continuous polymer phase weight; the disperse polymer phase comprises a copolymer of ethylene selected from ethylene-vinyl acetate (EVA), ethylene-butyl acrylate (EBA), ethylene-vinyl-alcohol (EVOH) copolymers and mixtures thereof (EBA-EVOH and EVA-EVOH) and low density polyethylene (LDPE) in a concentration comprising from 95 % to 99.8 % w/w of the total disperse polymer phase weight; and wherein the amount of continuous polymer phase is comprised of from 90 % w/w to 98 % w/w of the total polymer matrix. In accordance with another particularly preferred embodiment of the present disclosure, the continuous polymer phase have poly(methylmethacrylate) polymer, being the concentration of poly(methylmethacrylate) (PMMA) in the range of 99.5 % w/w to 99.8 % w/w of the total continuous polymer phase weight; and the disperse polymer phase comprises a copolymer of ethylene selected from ethylene-vinyl acetate (EVA), ethylene-butyl acrylate (EBA), ethylene-vinyl-alcohol (EVOH) copolymers (EVOH) and mixtures thereof (EBA-EVOH and EVA-EVOH) and low density polyethylene (LDPE) in a concentration in the range of 99.5 % w/w to 99.8 % w/w of the total disperse polymer phase weight; and wherein the amount of continuous polymer phase is comprised of from 85 % w/w to 90 % w/w of the total polymer matrix. Another aspect of the present invention refers to processes for producing the submicrocellular polymeric foams herein disclosed. The process may be a batch process, a semi-continuous process or a continuous extrusion foam process. The skilled person in the art knows different preparation processes which may be applicable to the preparation of both the continuous or the disperse polymer phase. The continuous phase may be prepared for example by melt- blending together the at least one of a polyacrylate polymer, a

polyalkylacrylate polymer and mixtures thereof, to form a continuous polymer phase. The disperse polymer phase may be prepared by a similar process.

The mixture of continuous polymer phase and disperse polymer phase is impregnated with a blowing agent to produce an expandable polymeric mixture.

The blowing agent may be selected from any blowing agent commonly known in the art. Suitable blowing agents include any one or combination of more than one of inorganic gases such as argon, nitrogen, carbon dioxide, water and air; organic blowing agents such as aliphatic and cyclic hydrocarbons having from one to nine carbons including methane, ethane, n-propane, iso- propane, n-butane, iso-butane, n-pentane, iso-pentane, neo-pentane, cyclobutane and cyclopentane; fully and partially halogenated alkanes and alkenes having from one to five carbons, preferably the ones that are chlorine-free (e.g., difluoromethane (HFC-32), perfluoromethane, ethyl fluoride (HFC- 161 ), 1 , 1 ,- difluoroethane (HFC- 152a), 1 ,1 ,1 -trifluoroethane

(HFC- 143a), 1 ,1 ,2,2-tetrafluoroethane (HFC- 134), 1 ,1 ,1 ,2 tetrafluoroethane (HFC- 134a), pentafluoroethane (HFC-125), perfluoroethane, 2,2- difluoropropane (HFC-272fb), 1 ,1 ,1 -trifluoropropane (HFC-263fb), 1 ,1 ,1 ,2,3,3, 3-heptafluoropropane (HFC-227ea), 1 ,1 ,1 ,3,3-pentafluoropropane (HFC- 245fa), and 1 , 1 ,1 ,3,3-pentafluorobutane (HFC-365mfc)); aliphatic alcohols having from one to five carbons such as methanol, ethanol, n-propanol, and isopropanol; carbonyl containing compounds such as acetone, 2-butanone, and acetaldehyde; ether containing compounds such as dimethyl ether, diethyl ether, methyl ethyl ether; carboxylate compounds such as methyl formate, methyl acetate, ethyl acetate; carboxylic acid and chemical blowing agents such as azodicarbonamide, azodiisobutyronitrile, benzenesulfo- hydrazide, 4,4-oxybenzene sulfonyl semi-carbazide, p-toluene sulfonyl semi- carbazide, barium azodicarboxylate, Ν,Ν'- dimethyl-N,N'- dinitrosoterephthalamide, trihydrazino triazine and sodium bicarbonate.

Preferably the blowing agent comprises CO ₂ , N ₂ , n-pentane, n-butane, s- butane, s-pentane and mixtures thereof.

The blowing agent concentration in an expandable polymer composition is preferably comprised from 10 % w/w to 40 % w/w relative to total expandable polymeric mixture weight; more preferably from 15 % w/w to 30 % w/w; yet more preferably from 20 % w/w to 28 % w/w.

Impregnation step with the blowing agent is preferably performed at a pressure of at least 5 MPa, preferably at least 10 MPa; and at a temperature of at least 10°C, preferably 25°C.

In accordance with a particular embodiment, the foaming step is performed at a saturation pressure in the range of 1 -30 MPa, preferably from 10 to 25 MPa; and at a temperature comprised of from 50-120 °C preferably 70-1 10°C. The closed-cell polymeric foam according to the present disclosure is characterized by having a cell density, measured according to the method described in Kumar et al., Polym Eng Sci 1990; 30(20):1323-1329, comprised from 10 ¹⁰ to 10 ¹⁸ cells/cm ³ ; preferably from 10 ¹¹ to 10 ¹⁶ cells/cm ³ . Furthermore, the submicrocellular polymeric foam of the present disclosure has a porosity percentage comprised from 50 % to 99.9%; preferably from 60% to 90%.

The closed-cell polymeric foam according to the present disclosure may be characterized by a relative density comprised from 0.1 to 0.6, preferably from 0.1 to 0.45, more preferably from 0.1 to 0.4.

The closed-cell polymeric foam according to the present disclosure may be characterized by an impact resistance, measured according to UNE-EN ISO 179/1 standard method , comprised from 1 -30 KJ/m ² ; preferably from 1 -20 KJ/m ² ; more preferably from 1 -15 KJ/m ² .

The closed-cell polymeric foam according to the present disclosure may be characterized by a glass transition temperature, measured according to UNE- EN ISO 1 1357-1 :2010 and ISO 1 1357-3:1 1 , comprised from 60-180 °C;

preferably from 1 15-129 °C, more preferably from 1 17-126 °C.

The closed-cell polymeric foam according to the present disclosure may be characterized by an storage modulus, measured according to DMA analysis, comprised from 200-500 MPa; preferably from 200-400 MPa; more preferably from 220-380 MPa.

Furthermore, in accordance with a preferred embodiment of the present disclosure, the closed-cell polymeric foam according to the present disclosure may be characterized by having

i) a relative density comprised from 0.1 to 0.6

ii) an impact resistance, measured according to UNE-EN ISO 179/1 standard method , comprised from 1 -30 KJ/m ² ;

iii) a glass transition temperature, measured according to UNE-EN ISO

1 1357-1 :2010 and ISO 1 1357-3:1 1 , comprised from 60-180 °C; and

iv) an storage modulus, measured according to DMA analysis, comprised from 200-500 MPa. In accordance with another particular preferred embodiment, the closed-cell polymeric foam according to the present disclosure may be characterized by having

i) a relative density comprised from 0.1 to 0.4

ii) an impact resistance, measured according to UNE-EN ISO 179/1 standard method , comprised from 1 to 15 KJ/m ² ;

iii) a glass transition temperature, measured according to UNE-EN ISO 1 1357-1 :2010 and ISO 1 1357-3:1 1 , comprised from 1 15 to 129 °C; and

iv) an storage modulus, measured according to DMA analysis, comprised from 200 to 400 MPa.

Foaming may be performed by any foaming technique known in the art which is suitable for preparing thermoplastic polymeric foams including batch tank foaming and extrusion foaming.

Batch tank foaming process comprises providing a thermoplastic polymer matrix that contains any optional additives into a pressure vessel (tank), providing blowing agent into the vessel and pressurizing the inside of the vessel with a pressure high enough so as to dissolve the blowing agent in the thermoplastic polymer matrix to a desired concentration. Once a desired concentration of blowing agent is dissolved in the thermoplastic polymer matrix, the pressure in the vessel is relieved while the thermoplastic polymer matrix is in a softened state at the foaming temperature, and the

thermoplastic polymer matrix is allowed to expand into a thermoplastic polymeric foam article.

An extrusion process can be continuous or semi-continuous (for example, accumulative extrusion). An extrusion foam process comprises providing a foamable composition in an extruder at an initial pressure and in a softened state and then expelling the foamable composition at a foaming temperature into an environment of lower pressure than the initial pressure to initiate expansion of the foamable composition into a thermoplastic polymer foam. A general extrusion process comprises preparing a foamable polymer composition by mixing a thermoplastic polymer with a blowing agent in an extruder by heating the thermoplastic polymer composition in order to soften it, mixing a blowing agent composition together with the softened

thermoplastic polymer composition at a mixing (initial) temperature and initial pressure which precludes expansion of the blowing agent to any meaningful extent (preferably, that precludes any blowing agent expansion), desirably cooling the foamable polymer composition to a foaming temperature rather than using the initial temperature as the foaming temperature, and then expelling the foamable composition through a die into an environment having a temperature and pressure below the foaming temperature and initial pressure. Upon expelling the foamable composition into the lower pressure environment the blowing agent expands the thermoplastic polymer into a thermoplastic polymer foam. The process also comprises the steps of desirably, cooling the foamable composition after mixing and prior to expelling it through the die. In a continuous process, the foamable composition is expelled preferably at an essentially constant rate into the lower pressure environment, to enable essentially continuous foaming. Additionally, accumulative extrusion is a semi-continuous extrusion process that comprises: 1 ) mixing a thermoplastic material and a blowing agent composition to form a foamable polymer composition; 2) extruding the foamable polymer composition into a holding zone which is maintained at a temperature and pressure which do not allow the foamable polymer composition to foam; the holding zone having a die defining an orifice opening into a zone of lower pressure at which the foamable polymer composition foams and an openable gate closing the die orifice; 3) periodically opening the gate while substantially concurrently applying mechanical pressure by means of a movable ram on the foamable polymer composition to eject it from the holding zone through the die orifice into the zone of lower pressure, and 4) allowing the ejected foamable polymer composition to expand into foam.

In the present disclosure, physical and mechanical properties were determined according to standards. Particularly, the glass transition temperature (Tg), the melting temperature (Tm) and crystallinity were determined by Differential Scanning Calorimetry (DSC) according to UNE-EN ISO 1 1357-1 :2010 and ISO 1 1357-3:1 1 and the melt flow index (MFI) at 230°C and 3,8 Kg according to UNE-EN ISO 1 133:2001 .

Prior to mechanical or viscoelastic characterization, the polymeric foam samples of the invention were polished using a polishing machine (model LaboPOI2-LaboForce3, Struers) equipped with a silicon carbide grinding paper (P 180) to obtain homogeneous surfaces and to remove the outer solid or dense skin of the samples (Pinto J, Pardo S, Solorzano E, Rodriguez- Perez MA, Dumon M, de Saja JA. Defect Diffus Forum 2012;326-328:434- 439).

After polishing, samples had an average thickness of around 5 mm. Then, solid and polished samples were machined in different ways according to the test to be performed. Thus, DMA samples were prepared using a precision cutting machine Mod. 1000 from IsoMet. The test pieces were prepared to be approximately 2 mm in thickness, 7 mm in width, and 25 mm in length.

A 0.5 J pendulum for Charpy impact testing Frank was used in order to determine the mechanical behavior at high strain rates. At least three specimens were used for each sample, all of them carried out at controlled humidity and temperature and performed according to UNE-EN ISO 179-1 . Viscoelastic behavior of foamed samples both at room temperature and as a function of temperature was analyzed using a dynamic mechanical analyzer model DMA 7 from Perkin Elmer. The experiments were performed in a three- point bending configuration with a frequency of 1 Hz and a dynamic stress of 3- 10 ⁴ kPa for foams and of 1 ^■ 10 ⁵ kPa for the solids. A static stress of 1 ,2 times the value of the dynamic stress was applied in all the conducted tests.

Measurements as a function of temperature were carried out at a rate of 3 °C/min from 0 to 1 10 °C. The onset of temperature was maintained constant during 3 min before starting the experiment in order to assure an equilibrium temperature.

Some values given were determined according to internal methods or using conventional techniques. Particularly, the foamed and solid sample densities were determined by water displacement method, based on Archimedes' principle, using the density determination kit for an AT261 Mettler-Toledo balance. At least three measurements were carried out for each sample produced.

%CO ₂ uptake

The total amount of gas uptake was calculated as the percentage of weight increment of the sample due to the gas sorption. The final weight of the samples after the whole saturation process was evaluated from the

desorption vs. time curve, which was registered with a Metier-Toledo balance. This curve can be extrapolated to zero desorption time in order to obtain the total amount of gas uptake during saturation as described in Tang, M.; Du, T.-

B.; Chen, Y.-P. Sorption and diffusion of supercritical carbon dioxide in polycarbonate. J. Supercrit. Fluids 2004, 28, 207-218.

The cellular structure of foamed samples was analyzed by SEM using an FEI Quanta 200FEG scanning electron microscope according to the following procedure. Foams were frozen in liquid nitrogen and fractured to assure that the microstructure remained intact. The fractured surface was coated with gold using a sputter coater (model SCD 004, Balzers Union). Some of the key parameters of the cellular structure were obtained with a specialized software (Pinto J, Solorzano E, Rodriguez-Perez MA, de Saja JA. J Cell Plast

2013;49(6):555-575) based on ImageJ/FIJI (Abramoff MD, Magalhaes PJ, Ram SJ. Biophot Int 2004;1 1 (7):36-42). This software provides the cell size distribution, the average cell size (φ), the standard deviation of the cell size distribution (SD), the cell anisotropy ratio distribution, the average cell anisotropy ratio, the asymmetry coefficient (AC), the cell density N _v (number of cells per cubic centimeter of the foam), and the cell nucleation density N ₀ (number of cells per cubic centimetre of the solid precursor). The number of cells per cubic centimeter of the foamed material (N _v ) was calculated using Kumar's theoretical approximation (Kumar V, Suh NP. Polym Eng Sci

1990;30(20):1323-1329). In this method, no direct measurements of cell dimensions over the micrograph are required, only the micrograph area (A) and the total number of cells (n) contained are measured. From these values and the magnification factor of the micrograph (M), N _v can be calculated using

Eq. (1 ):

This method also provides an expression (Eq. (2)) to estimate the cell nucleation density (N ₀ , number of cells per cubic centimetre of the solid unfoamed material) from N _v and the relative density of the foam (p _re i). This equation assumes that coalescence did not occur during the cell growing and stabilization stages:

Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and/or equivalents thereof are possible. Furthermore, all possible combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow.

Throughout the description and claims the word "comprise" and variations of the word, are not intended to exclude other technical features, additives, components, or steps. Furthermore, the word "comprise" encompasses the case of "consisting of. For the purposes of the invention the expressions "obtainable", "obtained" and equivalent expressions are used

interchangeably, and in any case, the expression "obtainable" encompasses the expression "obtained".

Additional objects, advantages and features of the invention will become apparent to those skilled in the art upon examination of the description or may be learned by practice of the invention. The following examples and drawings are provided by way of illustration, and they are not intended to be limiting of the present invention. Furthermore, the present invention covers all possible combinations of particular and preferred embodiments described herein.

EXAMPLES Materials:

PLEXIGLAS V825 (PMMA) is a thermoplastic acrylic resin (PMMA) supplied by Arkema.

ALCUDIA PA27003 (EBA) is an Ethylene Butyl acrylate resin (EBA) supplied by Repsol Quimica.

EVAL F171 B (EVOH) is an Ethylene Vinyl Alcohol (EVOH) resin supplied by Kuraray.

ALCUDIA PE003 (LDPE) is a Low Density Polyethylene resin (LDPE) supplied by Repsol Quimica.

ALCUDIA PA539 (EVA) is an Ethylene Vinyl Acetate resin (EVA) supplied by Repsol Quimica.

Example 1 . Preparation of Polyalkylacrylate/Polyolefin blends

Examples E1 -E7 and Comparative Examples CE1 -CE3 were obtained by blending Polyalkylacrylate and Polyolefins with different Polyalkylacrylate and Polyolefin amounts (from 5 to 70 wt%) in an extruder (Table I). All the materials were dried at 50 °C during 10 h prior to the extrusion. In particular, a ZSK-25 Coperion's twin screw extruder was operated using a temperature profile of 160 to 225°C at 12 Kg/h and 200 rpm. Pellets from each blend were obtained using a continuous cutting machine operating at the end of the extrusion line. In all cases ca. 1000 ppm of a mixture 50:50 of Irganox 1010 and Irgafos 168 were added. Example CE1 was prepared without using Polyolefin material. Example E2 and Comparative Example CE3 were prepared using a masterbatch of two Polyolefins (75% EBA/25%

EVOH). A 50/50 mixture of Irganox 1010 and Irgafos 168 (ca. l OOOppm) was not added in Examples E5. Polyalkylacrylate/Polyolefin blends generated following this procedure were no transparent and macroscopically

homogeneous.

The physical properties of the novel Polyalkylacrylate/Polyolefin compositions are summarized in Table II.

Table I: Polyalkylacrylate/Polyolefin blended compositions (Examples E1 -E7 and Comparative Examples CE1 -CE3)

Example Polyalkylacrylate, Repsol's Commercial Polyolefin Additives Re-extrusion

CE1 99.9% PLEXIGLAS V825 (PMMA) - Y N

E1 89.9% PLEXIGLAS V825 (PMMA) 10% ALCUDIA PA27003 (EBA) Y N

CE2 30% PLEXIGLAS V825 (PMMA) 69,9% ALCUDIA PA27003 (EBA) Y N

10% (75% ALCUDIA PA27003

E2 89.9% PLEXIGLAS V825 (PMMA) Y N

(EBA)/25% EVAL F171 B (EVOH))

69,9% (75% ALCUDIA PA27003

CE3 30% PLEXIGLAS V825 (PMMA) Y N

(EBA)/25% EVAL F171 B (EVOH))

E3 89.9% PLEXIGLAS V825 (PMMA) 10% ALCUDIA PE003 (LDPE) Y N

E4 89.9% PLEXIGLAS V825 (PMMA) 10% ALCUDIA PA539 (EVA) Y Y

E5 90% PLEXIGLAS V825 (PMMA) 10% ALCUDIA PA27003 (EBA) N Y

E6 89.9% PLEXIGLAS V825 (PMMA) 10% ALCUDIA PA27003 (EBA) Y Y

E7 94.9% PLEXIGLAS V825 (PMMA) 5% ALCUDIA PA27003 (EBA) Y N

Table I I: Physical properties of the novel Polyalkylacrylate/Polyolefin compositions

Solid Precursors

Polyacrylates and Polyolefin pellets were first dried in vacuum (680 mm Hg) at 50°C during 24 h before processing. Then, they were compression molded into precursors of 4 mm in thickness using a two-hot plates press. The temperature of the press was fixed at 250°C. The material was first molten without pressure for 8.5 min, then it was compacted under a constant pressure of 21 .8 bars for another minute and finally it was cooled down under the same pressure. The samples showed a good surface appearance with no presence of air bubbles inside the parts. Finally, these molded precursors were cut at 2.5 x 2.5 x 4 mm ³ dimensions and used later for foaming.

The physical properties of the novel Polyalkylacrylate/Polyolefin solid precursors are summarized in Table III. The disperse phase diameter of the solid precursor is calculated in the same way as average cell size.

Table I II: Physical properties of the novel Polyalkylacrylate/Polyolefin solid precursors E1 0.63 ± 0.07 0.51

CE2

E2 0.49 ± 0.04 0.56

CE3

E3 0.9 ± 0.1 0.50

E4 0.61 ±0.07 0.61

E5 0.78 ± 0.08 0.69

E6 0.65 ± 0.04 0.60

E7 0.4 ± 0.1 0.4

* SD, normalized standard deviation; Φ, disperse phase diameter

Solid State Foaming Production Process Foaming experiments were carried out in a high pressure vessel (model PARR 4681 ) provided by Parr Instrument Company, with a capacity of 1 L and capable of operating at a maximum temperature of 350°C and a maximum pressure of 41 MPa. The reactor is equipped with an accurate pressure pump controller (model SFT-10) provided by Supercritical Fluid Technologies Inc., and it is controlled automatically to keep the pressure at the desired values.

The vessel is equipped with a clamp heater of 1200 W, and its temperature is controlled via a CAL 3300 temperature controller. The CO ₂ vessel

temperature and pressure were monitored in the course of the process.

Therefore, a collection of experiments were performed using the so-called solid state foaming process (Goel SK, Beckman EJ. Cell Polym 1993;

12(4):251 -274; Nawaby AV, Handa YP, Liao X, Yoshitaka Y, Tomohiro M. Polym Int 2007; 56(1 ):67-73). This process with amorphous polymers has three stages: saturation (under fixed gas pressure and temperature), desorption (room pressure and temperature), and foaming of the sample (at a temperature over or near the effective Tg of the polymer).

Comparative examples CE2 and CE3 consisted of 30% PLEXIGLAS V825 and 69.9% Polyolefins supplied commercially by Repsol Quimica SA do not foam and show values of density/disperse phase diameter as expected for the solid precursors. A. Process Conditions Effect

A preliminary study of Process Conditions Effects were conducted with the samples E1 , E2 and CE1 . In this study it was decided to work at room temperature during the saturation stage and at three different pressures (30 MPa, 10 MPa and 5 MPa) in order to obtain different microcellular and nanocellular foams. All samples were saturated during 24 h to assure equilibrium dissolution of CO ₂ in the polymer. After the saturation process, the pressure inside the vessel was released. During the desorption step, the temperature of the samples decreased to values clearly below room temperature, indicating adiabatic depressurization, so when samples were removed from the pressure vessel they are cooled and solid (Pinto J,

Reglero-Ruiz JA, Dumon M, Rodriguez-Perez MA. J Supercrit Fluids

2014;94:198-205). Unlike previous studies, in this one a step of controlled foaming is introduced in order to control the final density of the samples. Foaming of the samples was carried out in a thermostatic water bath at temperatures of 25, 75 and 90 °C and times between 40 s and 5 min.

The physical properties of the novel Polyalkylacrylate/Polyolefin foams are summarized in Table IV.

All the resulting structures were closed and those obtained at 90 °C were bimodal. Independently of the process conditions, densities achieved with mixture of materials were lower than with the reference material. This result is very interesting and unpredictable, since although those materials with a second phase absorb lower gas amounts, they show lower densities.

Higher expansion ratios (near 4) were obtained when the foaming

temperature was increased up to 90 °C. Values obtained are very high for this process and very difficult to achieve.

Table IV: Physical properties of the novel Polyalkylacrylate/Polyolefin foams: Process Condition Effect 3

Example Absorbed C0 ₂ , % P (kg/m ) Expansion Ratio p- Relative φ(μιπ) SD/φ AC

SATURATION CE1 30.33 557.4 ±26.9 2.13 0.467 0.54 0.66 1.06 PRESSURE - FOAMING E1 27.89 489.5 ± 19.9 2.35 0.425 1.44 0.58 1.58 TEMPERATURE

- 30 MPa- 25°C E2 27.49 512.2 ±26.1 2.26 0.442 1.08 0.56 0.91

SATURATION CE1 23.57 614.4 ±48.9 1.94 0.515 1.14 0.53 1.59 PRESSURE - FOAMING E1 22.39 478.5 ±8.2 2.40 0.415 1.64 0.54 0.99 TEMPERATURE

- 10 MPa-25°C E2 21.98 455.9 ±66.6 2.54 0.393 1.66 0.59 0.81

SATURATION CE1 21.53 594.1 ± 18.5 1.93 0.516 1.04 0.52 1.91 PRESSURE - FOAMING E1 20.41 540.1 ±5.2 2.13 0.469 1.50 0.54 1.13 TEMPERATURE

- 5 MPa- 25°C E2 19.96 528.2 ±6.9 2.19 0.456 1.38 0.67 1.12

SATURATION CE1 23.57 511.7 ±9.9 2.24 0.445 1.01 0.59 1.70 PRESSURE - FOAMING E1 22.40 414.6 ±21.5 2.77 0.360 1.93 0.56 0.70 TEMPERATURE

-10 MPa- 75°C E2 21.99 445.8 ±5.3 2.59 0.385 1.10 0.71 1.25

SATURATION CE1 23.57 320.4 ±1.6 3.59 0.278 1.34 0.64 2.57 PRESSURE - FOAMING E1 22.40 281.6 ±6.2 4.08 0.245 2.56 0.57 1.35 TEMPERATURE

-10 MPa- 90°C E2 21.99 285.3 ±0.7 4.06 0.246 2.55 0.68 1.43

Nv No Nucleation Degeneration

Example

(cells/cm ) (cells/cm ) Efficiency Ratio

SATURATION 13

CE1 6.60 -10 ¹² 1.46 -10 - - PRESSURE -

FOAMING E1 3.72 -10 9.01 -10 ¹¹ 0.96 1.04

TEMPERATURE - 12

30 MPa- 25°C E2 5.07 -10 ¹¹ 1.19 -10 0.64 1.56

SATURATION 12

CE1 6.57 -10 ¹¹ 1.35 -10 - - PRESSURE -

FOAMING E1 2.55 -10 6.20 -10 ¹¹ 0.66 1.51

TEMPERATURE - 10 MPa-25°C E2 2.34 -10 5.39 -10 ¹¹ 0.29 3.45

SATURATION 12

CE1 8.10 -10 1.56 -10 - - PRESSURE -

FOAMING E1 3.00 -10 6.40 -10 ¹¹ 0.68 1.46

TEMPERATURE - 5 MPa- 25°C E2 3.89 -10 ¹¹ 8.54 -10 ¹¹ 0.46 2.18

SATURATION 12

CE1 8.47 -10 1.58 -10 - - PRESSURE - 11

FOAMING E1 1.70 -10 4.72 -10 0.50 1.98

TEMPERATURE - 12

10MPa-75°C E2 8.82 -10 2.29 -10 0.81

SATURATION 12

CE1 5.64 -10 ¹¹ 2.02 -10 - - PRESSURE -

FOAMING E1 8.57 -10 ¹⁰ 3.50 -10 ¹¹ 0.37 2.67

TEMPERATURE - 11

10MPa-90°C E2 8.65 -10 ¹⁰ 3.51 -10 0.19 5.29

As the saturation pressure decreases, changes in the average cell size value are minimal in the mixture type materials, which would indicate that in these materials the nucleation process seems to be governed by the presence of the dispersed phase. This result is of great importance because it indicates that it has been possible to generate a system with heterogenous nucleation in which the foaming pressures do not influence the final result, aspect necessary to be able to process the material in continuous processes.

B. Polyolefin Chemical Composition Effect: Cellular structure

In this study it was decided to work with different Polyolefin Chemical Compositions at room temperature during the saturation stage and at a saturation pressure of 10 MPa. As in the previous paragraph, all samples were saturated during 24 h to assure equilibrium dissolution of CO ₂ in the polymer. After the saturation process, the pressure inside the vessel was released. During the desorption step, the samples temperature decrease to values clearly below room temperature (adiabatic depressurization), so when samples are removed from the pressure vessel they are cooled and solid (Pinto J, Reglero-Ruiz JA, Dumon M, Rodriguez-Perez MA. J Supercrit Fluids 2014;94:198-205). Foaming of the samples was carried out in a thermostatic water bath at 75 °C and times between 40 s and 5 min.

The physical properties of the novel Polyalkylacrylate/Polyolefin foams are summarized in Table V.

Table V: Physical properties of the novel Polyalkylacrylate/Polyolefin foams: Polyolefin Chemical Composition Effect on cellular structure

Saturation Pressure 10 MPa and Foaming Temperature 75°C

. Efficiency = Nucleation Efficiency

. Ratio = Degeneratio Ratio

C. Polvolefin Chemical Composition Effect: Mechanical Properties

The mechanical response of novel Polyalkylacrylate/Polyolefin foams was studied by means of a dynamic mechanical analyzer (DMA) and Charpy Impact Test. The physical properties of the novel Polyalkylacrylate/Polyolefin foams are summarized in Table VI.

Table VI: Physical properties of the novel Polyalkylacrylate/Polyolefin foams: Polyolefin Chemical Composition Effect on mechanical properties.

Saturation Pressure 10 MPa - Foaming Temperature 75°C

The results show that the mechanical properties normalized by the square of the relative density of polymeric foams present higher values than those of pure PMMA foams (CE1 ). In particular, compared to commercial

polyalkylacrylate resins, polymeric foam compositions according to this invention present higher impact resistance, glass transition temperature and storage modulus normalized by the square of the relative density. In addition, these polymeric compositions have excellent relative and absolute densities. Therefore, a good balance between mechanical properties and sustainability of the materials is obtained in the polymeric compositions of this invention.

REFERENCES CITED IN THE APPLICATION 1 . EP2144959

2. Kumar V, Suh NP. Polym Eng Sci 1990;30(20):1323-1329

3. Pinto J, Solorzano E, Rodriguez-Perez MA, de Saja JA. J Cell Plast 2013;49(6):555-575 4. Abramoff MD, Magalhaes PJ, Ram SJ. Biophot Int 2004;1 1 (7):36-42

5. Spitael, P.; Macosko, C. W.; Mcclurg, R. B.. Macromolecules 2004, 37, 6874-6882

6. Zhai, W.; Yu, J.; Wu, L; Ma, W.; He, J.. Polymer 2006, 47, 7580-7589 7. UNE-EN ISO 179/1

8. UNE-EN ISO 1 1357-1 :2010

9. ISO 1 1357-3:1 1

10. UNE-EN ISO 1 133:2001

1 1 . Pinto J, Pardo S, Solorzano E, Rodriguez-Perez MA, Dumon M, de Saja JA. Defect Diffus Forum 2012;326-328:434-439

12. Tang, M.; Du, T.-B.; Chen, Y.-P. J. Supercrit. Fluids 2004, 28, 207-218

13. Goel SK, Beckman EJ. Cell Polym 1993;12(4):251 -274

14. Nawaby AV, Handa YP, Liao X, Yoshitaka Y, Tomohiro M. Polym Int 2007;56(1 ):67-73

15. Pinto J, Reglero-Ruiz JA, Dumon M, Rodriguez-Perez MA. J Supercrit Fluids 2014;94:198-205