WO2022219445A1

WO2022219445A1 - Encapsulated phase change material, method and articles

Info

Publication number: WO2022219445A1
Application number: PCT/IB2022/053027
Authority: WO
Inventors: Hassan Sahouani; Sithya S. Khieu; Milind B. Sabade; Ryan J. ROGERS; Timothy YAMAYA; Ignatius A. Kadoma; Stephen M. Sanocki; Yaohua GAO
Original assignee: 3M Innovative Properties Company
Priority date: 2021-04-14
Filing date: 2022-03-31
Publication date: 2022-10-20

Abstract

Presently described are capsules comprising a phase change material encapsulated in a shell material wherein both the phase change material and shell material are biodegradable and/or compostable. In some embodiments, the shell is a crosslinked polyacid salt material. Methods of making capsules, packaging articles comprising encapsulated phase change material, and methods of making packaging articles are also described.

Description

ENCAPSULATED PHASE CHANGE MATERIAL, METHOD AND ARTICLES

Summary

Phase change materials (i.e. PCMs) are substances with a high heat of fusion that, when melting or solidifying, can store and release large amounts of energy at a certain temperature (that is, undergoing a phase change). During a phase change such as melting or freezing, molecules rearrange themselves and cause an entropy change that results in the absorption or release of latent heat. Throughout a phase change, the temperature of the material itself remains constant. Some exemplary common PCMs include salts, hydrated salts, fatty acids, and paraffins. PCM phase transition occurs at nearly constant temperature and unlike storage medium such as water; PCM captures 5-14 times more heat per unit volume. Thus, PCMs may be used as thermal energy storage medium for shipping and transportation articles. Further, unlike dry ice, the phase transition of PCMs do not release carbon dioxide.

Various encapsulated PCMs have been described in the art. Even though PCMs typically can be reused, eventually such materials require disposal. Thus, industry would find advantage in PCMs encapsulated in a biodegradable and/or compostable material.

Presently described are capsules comprising a phase change material encapsulated in a shell material wherein both the phase change material and shell material are biodegradable and/or compostable. The capsules typically have an average diameter of no greater than 10 mm. In some embodiments, the capsules have an average diameter of less than 1000, 900, 800, 700, 600, 500, 400, 300, 200, or 100 microns. The shell material is typically in contact with an unencapsulated phase change material. In some embodiments, the shell is a crosslinked polyacid salt material. In some embodiments, the polyacid salt material comprises crosslinked units of polyacid salt having a weight average molecular weight of at least 10,000 g/mole.

In other embodiments, methods of making capsules are described. In one embodiment, a method is described comprising forming a dispersion of a (e.g. unencapsulated) solid or liquid phase change material in an aqueous solution comprising a polyacid salt material; forming the dispersion into droplets; and contacting the droplets with an ionic crosslinker.

In other embodiments, a packaging article is described comprising encapsulated PCM as described herein; and a protective covering adjacent the capsules. The protective covering is also preferably biodegradable and/or compostable.

The encapsulated PCMs described herein as well as cold chain packaging, articles, and devices comprising such encapsulated PCMs can provide precise temperature control, which allows for the safe transport of vaccines and pharmaceuticals year-round, without active refrigeration. Brief Description of the Drawings

FIG. 1 is a Differential Scanning Calorimetry curve of an illustrative encapsulated PCM as described herein.

Detailed Description

The capsules described herein comprise a phase change material. PCMs maintain the desired temperature of an article to be transported during shipment. As such, the one or more PCMs may have one or more of the following qualities: fine tunability over a wide range of physical properties; resilient to temperature and jostling during shipping; freezing without much supercooling; ability to melt congruently; compatibility with a variety of conventional materials; chemical stability; non corrosive; non-flammable; and nontoxic. In some embodiments, the PCM(s) are compostable and/or biobased. The PCM may take the form of a liquid, gel, hydrocolloid, or three-dimensional solid shape (e.g., a rectangle, square, or brick).

Suitable PCMs may be an organic material, an inorganic material, or a combination thereof. Representative examples include salts, hydrated salts, fatty acids and esters, paraffins, and/or mixtures thereof. Because different phase change materials means for changing phases undergo phase change (or fusion) at various temperatures, the particular material that is chosen for use in the device may depend on the temperature at which the packaging is desired to be kept. Phase changes such as melting can be determined by Differential Scanning Calorimetry (using the test method further described in the examples). In some embodiments, the PCM has a phase change, such as melting in a temperature range from about -135°C to about 40°C. The desired phase change range within this range may depend on the intended use of the packaging. For example, food cold chain packaging is typically between about -36°C to about 25 °C. Biologic or pharmaceutical cold chain packaging is typically between about -135°C to about 40°C.

In some embodiments, as depicted in FIG. 1 the PCM has at least one melting temperature of less 40°C, 35°C, 30°C, or 25°C. In some embodiments, the PCM has at least one melting temperature of at least -40°C, -35°C, -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, 15°C.

In some embodiments, the PCM is a paraffin having 13 to 28 carbon atoms. The melting temperature of a paraffin hydrocarbon is related to the number of carbon atoms. For example, n- tridecane has a melting temperature of -5.5°C; n-tetradecane has a melting temperature of 5.9°C; n-pentadecane has a melting temperature of 10°C, n-hexadecane has a melting temperature of 18.2, n-heptadecane has a melting temperature of 18.2 and n-octadecane has a melting temperature of 28.2. It is appreciated that paraffins typically comprises a mixtures of molecules having different chain lengths. In some embodiments, the PCM preferably has a sharp malting point, as illustrated in FIG. 1. Notably the melting temperature peak is within a 10, 9, 8, 7, 6, or 5 degree temperature range.

Although paraffin PCMs can be preferred for some (e.g. cold chain packaging) embodiments, the method described herein is suitable for encapsulating a variety of hydrophobic PCMs which can be dispersed in water. Hydrophobic crystalline PCM materials include for example 2,2-dimethyl- 1, 3 -propanediol, 2-hydroxymethyl-2-methyl-l, 3 -propanediol, acids of straight or branched chain hydrocarbons such as eicosanoic acid and esters such as methyl palmitate, and fatty alcohols.

Other exemplary phase change materials or means for changing phases useable in the present cold chain packaging, devices, and articles may include compositions produced in accordance with the process as described in U.S. Pat.No.6,574,971, that have the desired phase change temperature and other characteristics described above. The materials of U.S. Pat. No. 6,574,971 include fatty acids and fatty acid derivatives made by heating and catalytic reactions, cooling, separating and recirculating. The reactant materials include a fatty acid glyceride selected from the group consisting of oils or fats derived from soybean, palm, coconut, sunflower, rapeseed, cotton seed, linseed, caster, peanut, olive, safflower, evening primrose, borage, carboseed, animal tallows and fats, animal greases, and mixtures thereof. In accordance with the processes of U.S. Pat. No. 6,574,971, the reaction mixture is a mixture of fatty acid glycerides that have different melting temperatures and the reaction is an interesterification reaction, or the reaction mixture includes hydrogen and the reaction is hydrogenation, or the reaction mixture is a mixture of fatty acid glycerides and simple alcohols and the reaction is an alcoholysis reaction.

Additional exemplary PCMs include those listed in the following documents: U.S. Patent Nos. 9,850,415; 9,914,865; 10,119,057; and 10,745,604, each of which is incorporated by reference in their entirety herein.

In typical embodiments, the PCM is typically not pre-encapsulated. Thus, the phase change material lacks a second encapsulate such as gelatin, polyurethane, polyurea, urea- formaldehyde, urea-resorcinol-formaldehyde, melamine-formaldehyde. Thus, an unencapsulated PCM is encapsulated with crosslinked polyacid salt material as described. Further, the crosslinked polyacid salt material is in contact with an unencapsulated phase change material. Exemplary Polyacid Salt Materials

Presently described are capsules comprising a phase change material encapsulated in a shell. The shell material is biodegradable and/or compostable.

In some embodiments, the shell comprises a crosslinked polyacid salt material.

A polyacid is a polyelectrolyte containing acid groups on a substantial fraction of the polymerized units thereof. Most common acid groups are -COOH, -SO₃H, or - PQ₃H₂. Polyelectrolytes can be divided into "weak" and "strong" types. A "strong" polyelectrolyte is one that dissociates completely in solution for most pH values. A "weak" polyelectrolyte, by contrast, has a dissociation constant (pKa or pKb) in the range of ~2 to ~10, meaning that it will be partially dissociated at intermediate pH. Thus, weak polyelectrolytes are not fully charged in solution, and moreover their fractional charge can be modified by changing the solution pH, counter-ion concentration, or ionic strength.

In some embodiments, the encapsulant may be characterized as a crosslinked salt of a weak polyelectrolyte, such a polyacrylic acid. Poly(acrylic acid) (PAA) is a synthetic (e.g. high- molecular weight) polymer of acrylic acid. Poly(methacryiic acid) (PMAA) is a synthetic (e.g. high-molecular weight) polymer of methacrylic acid. In typical embodiments, PMAA is less favored due to its odor. In some embodiments, the poly(meth)acrylic acid is a homopolymer of acrylic acid or methacrylic acid. In other embodiments, poly(meth)acrylic acid is a copolymer of (meth)acrylic acid and a second (e.g. carboxylic) acidic comonomer, such as maleic acid. In oilier embodiments, the poly(metli)aeryiic acid is a copolymer of acrylic acid crosslinked with a non- acidic comonomer such as an ally ether of pentaerythritol, sucrose or propylene. In yet another embodiments, the poly(meth)acrylic acid may be described as sodium polyacrylate, the reaction product of acrylic acid (H₂C=CHCOOH) and its sodium salt (H₂C=CHCOONa). Sodium polyacrylate copolymer comprises (e.g. alternating) polymerized units of both acrylic acid and sodium acrylate. Thus, poly(meth)acrylic acid and (e.g. sodium) monovalent salts thereof can further comprise various comonomers provided the poly(meth)acrylic acid or monovalent salt thereof is soluble in distilled water or a (e.g. 10 wt.%) sodium hydroxide solution. In favored em bodiments, comonomer(s) used in the preparation of the poiy(meth)acrylic acid salt are monomers wherein the homopolymer of such monomer is biodegradeable and/or compostable.

In a water solution at neutral pH, poly(meth)acryhc acid is an anionic polymer, i.e. many of the side chains of poly(meth)acrylic acid will lose their protons and acquire a negative charge. Poly(meth)acrylic acid and salts thereof have the ability to absorb and retain water and swell to many times their original volume prior to crosslinking

Monovalent salts of (meth)polyacrylic acid are commercially available. Although sodium salts of (meth)polyacryiic acid are common, the monovalent salt can be a different monovalent alkali metal or ammonium. Further, monovalent salts of polyacrylic acid can he prepared by combining polyacrylic acid with a strong base, such as sodium hydroxide. Some representative structures of poly (meth)acry lie acid are depicted as follows:

It is appreciated that the poly(meth)acrylic acid salt may have various combinations of the depicted repeat units of these representative structures. In some embodiments, the poly(meth)acrylic acid salt may comprise a combination of polymerized units of acrylic acid and acrylic acid salt. Polyacids and salts thereof (e.g. (meth)acrylic acid and the monovalent (e.g. sodium) salt thereof) are available at various weight average molecular weights, ranging from about 1,000 (IK) g/mole to about 5,000,000 (5M) g/mole. In some embodiments, the polyacid and/or salt thereof has a weight average molecular weight of at least 2, 3, 4, 5, 6, 7, 8, 9,000 g/mole. In some embodiments, the polyacid and/or salt thereof having a weight average molecular weight of at least 10K, 15K, 20K, 25K, 30K, 35K, 40K, 45K, or 50K g/mole. When the molecular weight is too low, it can be difficult to encapsulate the PCM. In some embodiments, the polyacid and/or salt thereof has a molecular weight of no greater than 1M, 500K, 350K, 250K, or 100K. In some embodiments, the polyacid and/or sodium salt thereof has a molecular weight of no greater than 90K, 80K, 70K, 60K, or 50K When the molecular weight is too high, the viscosity of the polyacid salt solution can be difficult to process. The preferred molecular weight can be obtained by selection of a single polyacid and/or salt thereof. Alternatively, the preferred molecular weight can be obtained by a (e.g. weight-averaged) mixture of polyacids and/or salts thereof. The crosslinked polyacid salt material comprises crosslinked units of polyacid salt having a weight average molecular weight as just described.

The monovalent (e.g. sodium) salt of the polyacid is ionically crosslinked with a cation having a valency of two or more . Suitable cations include for example magnesium, calcium, zinc, barium, strontium, aluminum, iron, manganese, nickel, cobalt, copper, cadmium, lead, or mixtures thereof. Mixtures of cations can be utilized. In one embodiment, a calcium salt, such as calcium chloride is utilized to crosslink the monovalent (e.g. sodium) salt of poly(meth)acrylic acid. Thus, the crosslinked polyacid salt material comprises cationic groups having a valency of at least two. Stated differently, the crosslinked polyacid salt material comprises (e.g. carboxylic) acid groups ionically bonded with cations having a valency of at least two . Whereas crosslinked polyacid typically has the appearance of a transparent gel, the highly crosslinked polyacid salt precipitates as a white solid from the aqueous solution. The crosslinked polyacid salt material may or may not comprise some remaining monovalent (e.g. sodium) salt. The encapsulant comprises at least 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 wt.% or greater of crosslinked polyacid salt.

In some embodiments, the encapsulant comprises a crosslinked (e.g. sodium) salt of polyacid, in the absence of other polymers.

In other embodiments, the encapsulant comprises a crosslinked (e.g. sodium) salt of polyacid and a second polymer. In some embodiments, polyacid may be blended with other non- ionic polymers such as polyethylene oxide, poly-N-vinyl pyrrolidone, polyacrylamide, and cellulose ethers). In another embodiment, polyacid can he combined with oppositely charged polymers such as chitosan and (e.g. anionic) surfactants. In yet another example, the polyacid can be blended with gelatin. In favored embodiments, the second polymer, when present, is a biodegradeable and/or compostable material.

The crosslinked polyacid salt material is typically compostable and/or biodegradable. The compostability and biodegradability of polyacid materials has been described in the literature. (See for example https://www.irowater.com/research-biodegradability-polyacrylic-acid-polymers/) In some embodiments, the PCM is compostable and/or biodegradable. In some embodiments, the capsules comprising a phase change material encapsulated in a crosslinked polyacid salt material are compostable and/or biodegradable.

The term “compostable” refers to materials, compositions, or articles that meet the standard ASTM D6400 or ASTM D6868. It should be noted that those two standards are applicable to different types of materials, so the material, composition, or article need only meet one of them, usually whichever is most applicable, to be “compostable” as defined herein. Particularly, compostable materials, compositions, or articles will also meet the ASTMD5338 standard. Particularly, compostable materials, compositions, or articles will also meet one or more of the EN 12432, AS 4736, or ISO 17088 standards. More particularly, compostable materials, compositions, or articles will also meet the ISO 14855 standard. It should be noted that the term “compostable” as used herein is not interchangeable with the term “biodegradable.” Something that is “compostable” must degrade within the time specified by the above standard or standards into materials having a toxicity, particularly plant toxicity, that conform with the above standard or standards. The term “biodegradable” does not specify the time in which a material must degrade nor does it specify that the compounds into which it degrades pass any standard for toxicity or lack of harm to the environment. For example, materials that meet the ASTM D6400 standard must pass the test specified in ISO 17088, which addresses “the presence of high levels of regulated metals and other harmful components,” whereas a material that is “biodegradable” may have any level of harmful components.

Method of Encapsulating PCM

PCM encapsulation is a process of containing the PCM within a different material, preferably isolating the PCM from its surroundings. This is especially beneficial when the PCM is a liquid, corrosive, or reactive material. The outer crosslinked polyacid material may be characterized as an encapsulant or a shell.

The PCM can be encapsulated in the (e,g, polyacid salt) biodegradable and/or compostable shell material using any suitable chemical and/or physical technique.

In one embodiment, the method of encapsulating a PCM comprises forming a dispersion of a phase change material in an aqueous solution comprising a poly(meth)acrylic acid salt material; forming the dispersion into droplets; and contacting the droplets with an ionic crosslinker.

The step of forming a dispersion of a phase change material in an aqueous solution comprising a poly(meth)acrylic acid salt material typically comprises dissolving a polyacid salt in deionized water. The polyacid salt material can be purchased. In some embodiments, the concentration of polyacid salt in the aqueous dispersion is at least 25, 30, or 35 wt.% and typically no greater than 50, 45, or 40 wt.%. Alternatively, the method may comprise forming a polyacid salt material by dissolving a polyacid in a monovalent (e.g. 3-10 wt.% sodium hydroxide) salt solution, thereby forming the polyacid monovalent salt.

A (e.g. hydrophobic, non-water soluble) PCM material can be dispersed in the polyacid monovalent salt solution using various techniques. The PCM may be solid or liquid at the dispersion temperature. In one embodiment, a PCM that is solid a 25°C is melted and slowly added as a liquid to the polyacid monovalent salt solution while mixing with a high-shear mixer (e.g. 2000 rpm with a VWR Power Max Elite Dual Speed Mixer). In some embodiments, the concentration of (e.g. liquid) PCM in the dispersion is at least 5, 10, or 15 wt.% and typically no greater than 30, 25, or 20 wt.%. However, solid PCM’s can be added at higher concentrations.

In typical embodiments, a surfactant may be added to the dispersion. The amount of the surfactant can be at least 0.5, 1 or 2 wt.% and typically no greater than about 5 wt.%. Various surfactants are known in the art. In some embodiments, the composition comprises at least one non-ionic surfactant. Nonionic surfactants have no ions and thus have no electric charge. Nonionic surfactants typically derive their polarity from having a (e.g. oxygen-rich) polar portion of the molecule at one end and a large organic molecule (e.g. alkyl or alkenyl group containing from 6 to 30 carbon atoms) at the other end. The oxygen component is usually derived from short polymers of ethylene oxide or propylene oxide. Nonionic surfactants include for example alkyl polysaccharides, amine oxides, fatty alcohol ethoxylates, alkyl phenol ethoxylates, and ethylene oxide/propylene oxide block copolymers. One suitable surfactant is polyoxyethylene (20) sorbitan monolaurate. The surfactant may or may not be present in the final encapsulated PCM.

The step of forming the dispersion into droplets can be accomplished using various techniques. In one suitable method of forming microencapsulated PCM particles, the PCM dispersed in the aqueous solution of polyacid monovalent salt is sprayed, for example by using an atomizer nozzle to form a fine mist of droplets that descend into a solution of a multivalent salt, such as calcium chloride. In another embodiment of forming larger microencapsulated PCM particles, the dispersion can be dripped into the polyacid monovalent salt solution (e.g. using a burette). The step of forming the dispersion into droplets can be done using various other techniques. The particle size and shape of the capsules can vary depending on the method of delivering the dispersion.

When the outer polyacrylic acid salt encapsulant contacts the multivalent salt, the monovalent (e.g. sodium) atom are ionically exchanged for the multivalent (e.g. calcium) ion thereby ionically crosslinking the (e.g. carboxylic) acid groups.

PCM Capsules

In some embodiments, the capsules are relatively small having a particle size of less than 1000 microns. In some embodiments, the capsules have an average diameter of less than 1000, 900, 800, 700, 600, 500, 400, 300, 200, or 100 microns. In some embodiments, the capsules have an average diameter of at least 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 microns. In some embodiments, the capsules have an average diameter of at least 15, 20, 25, 30, 35, 40, 45, or 50 microns. Relatively small capsules may be described as microcapsules.

In other embodiments, the capsules may be characterized as macrocapsules having a particle size of 1000 microns (1 mm) or greater. In this embodiment, the capsules may have an average diameter of at least 1.5, 2, 2.5, or 3 mm. In some embodiments, the capsules have an average diameter no greater than 10, 9, 8, 7, 6, or 5 mm.

The capsules may be characterized as beads having a spherical shape. Alternatively, the capsules may have a non-spherical shape. When the capsules have a non-spherical shape, the average refers to the maximum dimension.

The capsules can comprise various amounts of PCM depending on the PCM and size of the capsules. In some embodiments, the capsules comprise at least 50, 55, 60, 65, 70, 75 or 80 wt.% of PCM, based on the total weight of the capsules. In one emboidments, such high loadings can be achieved when a solid PCM having a large particle size is encapsulated as described herein. In other embodiments, the capsules (e.g. containing a liquid PCM) may comprise at least 25, 30,

35, or 40 wt.% PCM, based on the total weight of the capsules. In some embodiments, the capsules comprise no greater than 60, 55, or 50 wt.% PCM, based on the total weight of the capsules.

FIG. 1 depicts Differential Scanning Calorimetry curves of an illustrative encapsulated PCM. With reference to FIG. 1, the encapsulated PCM typically comprises at least one melting temperature peak (e.g. at 23°C) that is the melting temperature of the unencapsulated phase change material. In some embodiments, the encapsulated PCM comprises more than one melting temperature. For example, if the capsules comprise a mixture of two different encapsulated PCM materials more than one melting temperature may be evident. Further, if the PCM material comprises a mixtures of different molecules, more than one melting temperature may be evident. In some embodiments, such as depicted in FIG. 1, the encapsulated PCM may optionally comprise a second melting temperature peak at about 0°C attributed to water present in the encapsulant (shell). The melting temperature peak height can be minimized by thoroughly drying the encapsulated PCM for a longer period of time/and or at higher temperatures. Alternatively, the melting temperature peak height at about 0°C can be increased by drying the encapsulated PCM for a shorter period of time or at lower temperatures. Alternatively, the melting temperature peak height can be increased by exposing the dried encapsulated PCM to water or high humidity.

As also depicted in FIG. 1, the encapsulated PCM typically comprises at least one crystallization temperature peak (e.g. at 25°C and 30°C,) that is the crystallization temperature of the unencapsulated phase change material. In some embodiments, the encapsulated PCM comprises more than one crystallization temperature. For example, if the capsules comprise a mixture of two different encapsulated PCM materials more than one crystallization temperature may be evident. Further, if the PCM material comprises a mixtures of different molecules, more than one crystallization temperature may be evident.

Articles Comprising PCM Capsules

The capsules described herein may be used in any application relating to the transfer and/or storage of heat. Specific examples include, but are not limited to, the use of these materials in HVAC systems and construction materials for residential and commercial buildings, home furnishings and automobile upholstery, heat sinks for computers, etc. food serving trays, medical wraps

Capsules described herein can be incorporated inside a clothing article such as a coat or vest or other article for the purpose of absorbing body heat to increase the wearer's comfort level and thus to increase the length of time that the wearer can engage in a physical activity. The encapsulated phase change materials can be used in a variety of products such as firefighting garments, hazmat suits, specialized clothing for foundry workers, armed forces, etc.

Cold Chain Packaging Articles and Devices

The cold chain packaging, articles, and devices comprise the encapsulated PCM as described herein and one or more protective coverings that are adjacent to the encapsulated PCM and that protect the encapsulated PCM and/or an item in the packaging (such as, for example, a vaccine or pharmaceutical) from the environment during shipping and transport.

As used herein, the term “packaging” refers to articles or devices or items that are used to transport, store, or protect goods. Some exemplary packaging includes, for example, mailers, envelopes, bags, and pouches. Exemplary Protective Coverings

Desired protective coverings of the present disclosure enclose or contain and protect the encapsulated PCM and/or article being packaged. The protective covering may be a single layer of material or multiple layers of material. Where multiple layers of materials are used, the multiple layers may be bonded or adhered in any suitable way including, for example, heat-sealing (e.g., induction welding or impulse sealing) or adhesive sealing. The protective coverings may have one or more of the following qualities.

In some embodiments, the protective covering has a low thickness to reduce weight and/or to aid in manufacturing and/or cost. In some embodiments, the thickness of the protective covering is typically at least 25 micrometers and no greater than 250 micrometers. In some embodiments, the thickness is less than 50 micrometers. In other embodiments, the thickness is at least 50, 100, or 150 micrometers.

In some embodiments, high durability and/or puncture resistance are important characteristics of a protective covering such that the covering maintains its integrity in a shipping environment where the package may be roughly handled or may encounter sharp or jagged edges of products or other packaging. These features also aid in preventing leakage of the phase change material(s) such that the phase change material could leak out of the package, and thus be unable to keep the temperature constant, or the phase change material(s) could come into contact with the shipped product, potentially reducing its efficacy or polluting it. As such, in some embodiments, the protective covering has a sufficiently high tensile strength. In some embodiments, the protective covering has a tensile strength of as measured according to ASTM D-882-18 of at least 5, 6, 7, 8, 9, or 10 MPa. In some embodiments, the protective covering has a tensile strength of no greater than 50, 45, 40, 35, 30, 25, 20 or 15 MPa. In some embodiments, the protective covering has a tensile modulus of at least 100, 150, 200, 250, 300, 350, 400, 450, or 500 MPa. In some embodiments, the protective covering has a tensile modulus of no greater than 3,500, 3,000, 2,500, 2,000, 1,500, 1,000, or 500 MPa. The tensile strength and modulus can be in a first (e.g. machine) direction or in a (e.g. cross) or in other words orthogonal direction to the first direction.

In some embodiments, the protective covering has sufficient elongation to provide adequate containment of the one or more phase change materials and the item to be transported during shipping. In some embodiments, the elongation of the protective covering is at least 1, 2, 3, 4, or 5% and typically no greater than 50, 45, 40, 30, 25, 20, 15, 10, or 5% as measured according to ASTM D-882-18.

In some embodiments, the protective covering has an Elmendorf tear force of at least 0.5, 0.6, 0.7, 0.8, 0. 9 or 1 Mpa. In some embodiments, the protective covering has an Elmendorf tear force of no greater than 3, 2.5, 2, 1.5, or 1 Mpa. The Elmendorf tear force can be in a first (e.g. machine) direction or in a (e.g. cross) or in other words orthogonal direction to the first direction.

Additional characteristics that are important include one or more of resistance to leakage, breathability (minimal breathability may be preferred), freeze/thaw performance (the ability to maintain integrity of the package over a wide range of temperatures, as stated herein), thermal formability, resistance to staining, resistance to odor, and/or water resistance.

In some embodiments, the protective covering has a peak load of at least 10, 15, 20 or 25 N. In some embodiments, the protective covering has a peak load of no greater than 50, 45, 40,

35, 30, or 25 N. In some embodiments, the protective covering has an Energy/A₀ to Peak (N.m/cm²) of at least 0.5, 0.6, 0.7, 0.8, 0. 9 or 1. In some embodiments, the protective covering has an Energy/A₀ to Peak (N.m/cm²) of no greater than 5, 4, 3, 2, or 1. These properties pertain to the puncture/impact resistance of the protective covering according to the test method described in the examples.

In some embodiments, the protective covering has a (e.g. heat-sealed) seam, such as in the case of a pouch. The seam strength can be evaluated according to the test method described in the examples. In some embodiments, the seam has a tear energy of at least 0.5, 1, or 1.5 KgF.cm. In some embodiments, the seam has a tear energy of no greater than 30, 25, 20, 15, 10 or 5 KgF.cm. In some embodiments, the seam has a peel peak load of at least 5, 6, 7, 8, 9, or 10 N. In some embodiments, the seam has a peel peak load of no greater than 40, 35, 30, 25, 20, 15, or 10 N.

Further, the pouch including the encapsulated PCM exhibits no leakage when tested according to the Freeze/Thaw Test described in greater detail in the examples.

In some embodiments, the protective covering is biodegradable and/or compostable, as previously described.

The protective coverings described herein may include a bio-based polymer.

Exemplary bio-based polymers include polybutylene succinate (PBS), poly(lactic acid) (which is sometimes known as PEA, and as used herein is intended to encompass both poly(lactic acid) and poly(lactide)), poly(glycolic acid) (which as used herein is intended to encompass both poly(glycolic acid) and poly(glycolide)), poly(caprolactone), poly(lactide-co-glycolide), copolymers of two or more of lactic acid, glycolic acid, and caprolactone, polyhydroxyalkanoate

(PHA), polyester urethane, degradable aliphatic-aromatic copolymers, poly(hydroxybutyrate)

(PHB), copolymers of hydroxybutyrate and hydroxy valerate, poly(ester amide), polyhydroxy hexanoate (PHH), cellulosic ester, and cellulose.

The protective coverings described herein may include a bio-based polymer and a bio based hydrophobic agent. As used herein, the term “hydrophobic” in reference to an agent, refers to an agent that exhibits an advancing water contact angle of at least 90°. Exemplary bio-based hydrophobic agents include plant-based waxes and plant-based oils. Exemplary bio-based hydrophobic agents include, but are not limited to, ethylene bis(stearamide) (EBS), castor wax, palmitic acid, linoleic acid, arachidic acid, palmitoleic acid, butyric acid, stearic acid, and triglyceride. In some embodiments, the protective covering includes between 0.5 and 15 polymer weight percent of the bio-based hydrophobic agent. In some embodiments, the protective covering includes more than 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, or 5.0 polymer weight percent of the bio-based hydrophobic agent. In some embodiments, the protective covering includes less than 15, 14, 13, 12, 11, or 10 polymer weight percent of the bio-based hydrophobic agent.

In some embodiments, the bio-based polymer and optional bio-based hydrophobic agent is in the form of a fdm or a film layer.

In some embodiments, the bio-based polymer and optional bio-based hydrophobic agent protective covering is in the form of a nonwoven sheet. Spun bonding is one particularly useful method of manufacturing nonwoven sheets of such materials. Exemplary spun bonding processes that produce nonwovens useful for the packaging articles described herein are described in U.S. Patent No. 3,803,817, but other processes may also be employed. Some additional exemplary suitable nonwovens include those that are spunbonded, melt-blown, spunlace, air laid, wet-laid or carded materials, and combinations thereof.

In some embodiments, the protective covering comprises a cellulosic layer the may include one or more of any type of paper such as, for example kraft paper or cardboard) or bleached paper.

In some embodiments, the protective cover is a multilayer construction comprising various combinations of the above described fdm layers, nonwovens, and cellulosic layers.

In some embodiments, the protective cover is a multilayer construction comprising a bio based fdm layer and a bio-based nonwoven or a bio-based fdm layer and a bio-based cellulosic layer such as Kraft paper. In some embodiments, the thickness of the bio-based fdm layer is at least 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 microns. In some embodiments, the thickness of the bio-based fdm layer is no greater than 50 or 25 microns.

Some exemplary protective coverings that satisfy one or more of the above characteristics are described in US patent application 63/199,350 fried 12-21-2020 and 83589WO004 fried April 14, 2021; incorporated herein by reference.

Any of the above constructions may include additional components including, for example, pigments and dyes including, for example, compostable or bio-based pigments and dyes. Exemplary compostable pigments and dyes include PLA masterbatch colorings available from Clariant Corp. (Minneapolis, MN, USA) under the OM or OMB lines of products, or those available from Techmer PM LLC (Clinton, TN, USA) under the PLAM or PPM lines of products. Typically, when colorings are employed, they are blended with the other coating components at an amount of 0.5% - 5% by weight.

In some embodiments, an optional layer is added to improve / lower the oxygen transmission rate (OTR). Some exemplary such layers include polyvinyl alcohol (PVOH) or ethylene vinyl alcohol (EVOH).

Any known method of forming these multi-layer constructions may be used including, for example, extrusion of one layer onto another layer and/or coating one layer with another layer. It is possible to use a combination of the foregoing two approaches in any embodiment of the articles described herein. In some embodiments, the adjacent layers may be completely overlapping in surface area. In other embodiments, the adjacent layers are only partially overlapping in surface area (i.e., a coating need not be applied to the entirety of the base layer or sheet, but can be on only part of the base layer or sheet).

In some embodiments, one or more protective covering layers are embossed. In some embodiments, the protective covering is embossed. In some embodiments, one of the protective covering or a protective covering layer includes projections or posts, as is described in U.S. Patent Application No. 63/011,024, (Matter No. 82723US002) assigned to the present assignee.

Exemplary Packaging Containers

The packaging constructions of the present disclosure protect the article being transported during transport and maintain the article at a constant desired temperature. The packaging devices, containers, and constructions described herein include one or more protective coverings described herein and one or more PCMs described herein. The packaging devices, constructions, or containers of the present disclosure may have one or more of the following characteristics.

In some embodiments, the packaging devices, containers, or constructions are compostable and/or biobased.

In some embodiments, the packaging devices, containers, or constructions have a high thermal insulation R value. A thermal insulation R value can be provided in SI units of Km²/W (aka RSI) or in imperial (US) units of ft².°F.h/BTU. A thermal insulation (US) R value per inch of at least 2, or 5, or higher is preferred, dictated by the temperature requirements and time duration desired. A thermal insulation (US) R value per inch is between about 2 and about 8 for EPS, PET, PUR type insulation with Aerogels having (US) R-values in the R-10 to R-30 range per inch and Vacuum Insulated Panels (VIP) with (US) R-values that can often exceed 40 and as be as high as 60 per inch. In some embodiments, the packaging devices, containers, or constructions have dimensional stability, which refers to the protective covering or packaging container has at least one dimension which decreases by no greater than 10% in the plane of the material or nonwoven when heated to a temperature at or within 15°C or 20°C above a glass transition temperature of the fibers of the fabric while in an unrestrained condition.

In some embodiments, the packaging devices, containers, and constructions have sufficient strength to maintain the integrity of the package during shipment. A packaging container may be dropped, jostled, or otherwise subjected to blunt forces during shipment and thus the packaging is preferably strong enough with withstand such forces.

The packaging devices, containers, and constructions and/or protective covering should be useful in a wide range of temperatures (as disclosed herein) and conditions, including a variety of humidity conditions. The packaging devices, containers, and constructions should be able to withstand freezing/thawing and should be able to withstand limited amounts of rain and liquid spillage that may occur during shipping/transport.

Within a typical vaccine cold chain, vaccines are packaged into individual vials which in turn are bundled together in inner packs for transport. They often include even larger groupings of cold boxes and vaccine carriers as well. PCMs are typically incorporated in sealed pouches to form PCM pillows. Prior to wrapping PCM pillows intimately around the inner packs or cold boxes and vaccine carriers, they are pre-conditioned in refrigerator or freezers to the desired temperatures for duration of transportation. Depending upon the cold chain transportation requirements, insulation material such as PET fibers, Styrofoam pallets, Aerogels, polyurethane (PUR), phenolic foam insulations, expanded polystyrene (EPS) foam or vacuum insulated panels (VIP) is often employed.

The packaging container may be any desired shape, size, or construction. Some exemplary constructions include mailers, envelopes, bags, boxes, and pouches. In some states, the packaging construction includes an opening through which the article to be shipped passes when placed in the packaging container. In some states, the packaging container is fully sealed and closed after placement of the article to be shipped within the packaging container. The packaging constructions of the present disclosure may also include one or more mechanisms or features to facilitate easy opening of the packaging article after it is sealed. Exemplary features include perforations, scoring, zip-tops, embedded pull-strings, wires, or combinations thereof. When an opening or flap is present, one or more of these features may be present near the opening or flap to facilitate opening the packaging article near the opening or flap, or they may be present on a different part of the packaging article. While these features, when employed, are most commonly in a straight line parallel to at least one edge of the packaging article no particular configuration is required; other shapes or layouts can be used depending on the intended use of the packaging article.

Some embodiments of the packaging construction further include an insulating material such as, for example, a foam (open or closed cell), aerogel, cardboard, urethane, expanded polystyrene, and/or fabric loaded with foam or aerogel.

The method of forming the shipping container, article, or device will depend on what design and style of shipping container, article, or device is desired. Pouches and envelopes can be formed as described in U.S. Patent Application Publication Nos. US/20160229622, US/20190226744, US/20090230138; bags can be formed as described in U.S. Patent No. 6,412,545 and Korean Patent No. 20-0492210; boxes can be formed as described in U.S. Patent

Application Publication No US/20200317423; PCT Patent Application Publication No. WO/2017048793; U.S. Patent Nos. 10,501,254; 9,376,605; 10,451,335; 9,950,851; and 9,429,350.

The encapsulated PCMs and (e.g. cold-chain) packaging articles described herein can be used to ship or package various temperature-sensitive items such as food, biologies, or medication including, but not limited to, vaccines.

Materials Used in the Examples

DSC - Differential Scanning Calorimetry The DSC analysis of the microencapsulated PCM was performed as follows: About 3-7 mg of a sample was crimped in a Tzero aluminum pan and placed in a Model DSC Q2000 DSC (obtained from TA Instruments, Eden Prairie, MN) for analysis. The reference was a crimped blank Tzero aluminum pan. The sample and the reference were kept free of contamination such as oils. The test was carried out in an heat-cool-heat cycle and the conditions were set as follows: starting temperature of 35°C; heating rate of 10°C/min°C/min; upper temperature of 250°C/min °C; cooling rate of 5°C/min; and a lower temperature of -100°C. At the end of the test cycle, the collected data was analyzed and the Heat Flow (W/g) was plotted against Temperature (°C).

Various parameters were derived from the DSC as defined as follows:

T_c - refers to the crystallization peak temperature of the first cooling scan, described as T_pc in ASTM D3418-12.

T_m - refer to the melting peak temperature of the second heating scan described as T_pm in ASTM D3418-12.

Preparation of pre-encapsulation composition:

A pre-encapsulation composition was prepared using the materials summarized below, in Table 1, in the following manner: NaOH was added to the DIW in 4000 mL glass container. This was stirred until completely dissolved. To this, was added the PAA and the whole was stirred until completely mixed. This resulted in a solution of PAA sodium salt. To this solution of PAA sodium salt, PS20 was added and the whole was stirred to blend the PS20.

PCM23 was then heated to 30°C to ensure it was melted. The molten PCM was added to the PAA sodium salt/PS20 solution and the whole was sheared at 2000 rpm with a VWR Power Max Elite Dual Speed Mixer sold by VWR, Radnor, PA to prepare a dispersion.

Table 1: Pre-encapsulation composition

Example 1: Preparation of microencapsulated PCM particles

The dispersion prepared as described above in “preparation of pre-encapsulation composition” was fed into an EXAIR SR1020SS atomizer nozzle obtained from by Exair Corp. Cincinnati, OH powered by inhouse compressed air at 30 psi pressure. The atomization jet was directed down into a 20-Liters, 10 wt. % calcium chloride solution in water contained in a plastic container. Air was constantly bubbled in this calcium chloride solution to disperse the particles. At the end of the atomization, the content of the plastic container was sheared again with the VWR Power Max Elite Dual Speed Mixer to break apart particle clumps and allow the calcium chloride to reach all the particles. The content was then decanted and air dried to recover microencapsulated PCM particles. The resulting microencapsulated PCM was inspected with an optical microscope. The size of the microcapsules ranged from 5 to 100 microns, averaging about 50 microns. Example 2: Preparation of macroencapsulated of PCM beads

The dispersion prepared as described above in “preparation of pre-encapsulation composition” was poured into a burette. The latter was adjusted to drip constantly into a 20-Liters, 10 wt. % calcium chloride solution in water contained in a plastic container. Air was constantly bubbled in this calcium chloride solution to disperse the formed particles. At the end of this process, the contents of the plastic container were decanted and air dried, resulting in approximately 3 mm beads of macroencapsulated PC.

The encapsulated PCM of Example 1 was analyzed via Differential Scanning Calorimetry. The results are depicted in FIG. 1.

Materials Used in the Examples 3 and 4

General Method for Forming Protective Coverings-I:

Protective coverings according to the Examples described below were formed via a melt extrusion process using a 58-millimeter (mm) twin screw extruder (Model DTEX58t, obtained from Davis- Standard, Pawcatuck, CT), operated at a 260°C extrusion temperature, with a heated hose (260°C) leading to a 760 mm drop die (obtained from Cloeren Inc., Orange, TX) with 686 mm deckles: 0-1 mm adjustable die lip, single layer feed-block system. Solid feed coating material was fed at a rate of 50 pounds per hour (22.7 kilograms per hour) into the twin screw system at the conditions described above. The resultant molten resin formed a thin sheet as it exited the die and was cast directly into a nip of two rolls. The surface roughness of the steel roll was set at 75 Roughness Average by use of a sleeve (American Roller Company, Union Grove, WI) against the cast film side, and a silicon rubber nip roll (80-85 durometer; from American Roller Company, Union Grove, WI) was set against the other side of the film melt. The film melt was pressed between the two nip rolls with a nip force of about 70 Kilopascals (KPa), at a line speed that was adjusted to provide the desired coating thickness. In an alternative method, once the melt left the die, it was laminated to a substrate (e.g., paper or nonwoven material) via a nip system as described above. If the protective covering was to be applied on both opposed major surfaces of the substrate, then the coating step was repeated in a second step.

Method of Making Pouches from Protective Coverings:

The protective coverings prepared as described in Examples described below were used to make pouches that were filled with the microencapsulated PCM particles of Example 1. The pouches were made using a manual impulse sealer (Model El-458, obtained from Uline, Pleasant Prairie, WI). Approximately 6” x 16” (15 cm x 41 cm) wide of protective coating material was folded in half having the coated side on the inside, then the edges of the folded web were heat sealed using the same impulse sealer to create approximately 6” x 8” (15 cm x 20 cm) pouches.

Method for Testing Seam Strength:

The seam strength of pouches made using the General Method of Making Pouches from Protective Coverings was determined using the procedures outline in ASTM F88/F88M, “Standard Test Method for Seal Strength of Flexible Barrier Materials.” Test specimens 2.5 cm (1 in) wide were cut from the pouches perpendicular to the seam, with at a length of at least 5.1 cm (2 in) of material on either side of the seam. Samples were conditioned overnight in a controlled temperature and humidity room at 22.8 ± 1.1 °C (73.1 ± 2 °F) and 50 ± 2% relative humidity prior to testing. Specimens were loaded into a constant-rate-of-extension tensile tester (Model MTS ALLIANCE RT/50 TESTING MACHINE, obtained from MTS Systems Corporation, Eden Prairie, MN) with a 1000 N load cell at an initial jaw separation of 3.8 cm (1.5 in). The sample was pulled until seam separation using an extension rate of 25 cm/min (10 in/min), and the average peak load and total energy of six specimens per sample were recorded. The seam width was measured, and the seam strength was calculated as the peak load divided by the seam width.

Method for Tensile Test:

Tensile strength, % elongation at break, and 1% secant modulus of protective coverings made according to the Examples described below were determined using the procedures described in ASTM D-882-18, “Test Method for Tensile Properties of Thin Plastic Sheeting”. For these tests a pull speed of 10 in/min (5 cm/min) was used, and samples were tested in both the machine direction (MD) and the cross-web (transverse) direction (CD).

Method for Elmendorf Tear Resistance Test:

Elmendorf tear resistance of protective coverings made according to the Examples described below were determined using the procedures described in ASTM D-1922-15, “Test Method for Propagation Tear Resistance of Plastic Film and Thin Sheeting by Pendulum Method”. The samples were tested in both the machine direction (MD) and the cross-web (traverse) direction (CD).

Method for Puncture/Impact Resistance Test:

Puncture/Impact resistance of protective coverings made according to the Examples described below were determined using the procedures described in ASTM D-1709-16a, “Test Methods for Impact Resistance of Plastic Film by the Free-Falling Dart Method” (Method A).

Method for Freeze/Thaw Test:

The pouches made using the General Method of Making Pouches from Protective Coverings was were tested by filming them with 230 mF of microencapsulated PCM particles of Example 1. The filled pouches were sealed and left in room temperature overnight to check for leakage. Then the sealed pouches were placed in a freeze/thaw chamber set at -17.8°C. The pouches were conditioned at -17.8°C for 24 hours and then thawed out to room temperature. The thawed pouches were visually inspected for leakage.

The protective covering of Example 3 was prepared by coating one major surface of a Kraft paper- 2 with a protective covering using the General Method for Forming Protective coverings-I described above. The Example 3 protective covering was a film having a thickness of 8.4 micrometers and had a composition of 50 wt. % BioPBS FD92-PB, 47.5% FZ91, and 2.5 wt. % CASTORWAX MP-80. Example 4

The protective covering of Example 4 was prepared by coating one major surface of a nonwoven, INGEO 6202D, with a protective covering using the General Method for Forming Protective coverings-I described above. The Example 4 protective covering was a film having a thickness of 4.2 micrometers and had a composition of 97.5 wt. % BioPBS FZ91-PB and 2.5 wt. % CASTORWAX MP-80.

Examples 3 and 4 protective coverings prepared as described above were tested using the test methods described above (e.g., method for testing seam strength, tensile test, Elmendorf tear resistance, puncture/impact resistance, freeze/thaw test). The results of the tests are summarized below in Tables 1 and 2 below.

Table 1.

Table 2.

Claims

What is claimed is:

1. Capsules of a phase change material encapsulated in a shell material wherein both the phase change material and shell material are biodegradable and/or compostable.

2. The capsules of claim 1 wherein the capsules have an average diameter of no greater than 10 mm.

3. The capsules of claims 1-2 wherein the capsules have an average diameter of less than 1000, 900, 800, 700, 600, 500, 400, 300, 200, or 100 microns.

4. The capsules of claims 1-3 wherein the shell material is in contact with an unencapsulated phase change material.

5. The capsules of claims 1-4 wherein the shell is a crosslinked polyacid salt material.

6. The capsules of claim 5 wherein the crosslinked polyacid salt material comprises cationic groups having a valency of at least two.

7. The capsules of claims 5-6 wherein the crosslinked polyacid salt material comprises carboxylic acid groups ionically bonded with cations having a valency of at least two.

8. The capsules of claims 5-7 wherein the crosslinked polyacid salt material comprises crosslinked units of polyacid salt having a weight average molecular weight of at least 10,000 g/mole.

9. The capsules of claims 5-8 wherein the crosslinked polyacid salt material comprises at least 50, 60, 70, 80, or 90 wt.% of polymerized units of poly(meth)acrylic acid salt.

10. The capsules of claims 1-9 wherein the capsules comprise at least 25, 30, 35, or 40 wt. % of phase change material based on the total weight of the capsules.

11. The capsules of claims 1-10 wherein the phase change material has a melt temperature of less than 25°C.

12. The capsules of claims 1-11 wherein the capsules are biodegradable and/or compostable.

13. A method of making capsules comprising: forming a dispersion of a phase change material in an aqueous solution comprising a polyacid salt material; forming the dispersion into droplets; contacting the droplets with an ionic crosslinker.

14. The method of claim 13 further comprising forming a polyacid salt material by dissolving a polyacid in a monovalent salt solution.

15. The method of claims 13-14 further characterized by claims 2-12.

16. A packaging article comprising: the capsules of claims 1-15; and a protective covering adjacent the capsules.

17. The packaging article of claim 16 wherein the protective covering comprises a fdm, a nonwoven, a cellulosic material, or a combination thereof.

18. The packaging article of claims 16-17 wherein the protective covering comprises a bio-based polymer.

19. The packaging article of claims 16-18 wherein the protective covering is biodegradable and/or compostable.

20. The packaging article of claims 16-19 wherein the packaging article is biodegradable and/or compostable.

21. A packaging article comprising: capsules of a phase change material encapsulated in a shell material wherein both the phase change material and shell material are biodegradable and/or compostable; and a protective covering adjacent to capsules, wherein the covering is biodegradable and/or compostable.

22. The packaging article of claim 21 wherein the capsules are according to claims 2-15.

23. The packaging article of claims 21-22 wherein the protective covering is according to claims according to claims 18-21.