Recycled foam

Abstract

This document provides a method for recycling polyolefin foam, comprising: a) providing a mixture comprising fragments of polyolefin foam and an aqueous composition comprising dispersed polyolefin particles; and b) removing water from the mixture. A composition comprising a mixture comprising polyolefin foam and an aqueous composition comprising dispersed polyolefin particles is also provided. An article is also provided, formed by a method comprising removing water from the composition.

Description

Technical Field

[0001] This invention relates to a method for recycling polyolefin foam. Prior Technology

[0002] Polyolefin foams are used in a variety of applications, including protective encapsulation (e.g., padding for electronic products during transport), building and construction applications (e.g., pipe insulation), recreational items (e.g., swim noodles and fitness mats), and automotive applications. The recycling of foams is increasingly necessary after use, or after they have been manufactured for one purpose but are intended for a different purpose. Post-consumer recycled (PCR) or post-industrial recycled (PIR) foams can be recycled by first mechanically reducing the foam to relatively small fragments (if the foam is not already in relatively small fragments), and then sintering the foam fragments using one or more adhesives to form larger, usable articles. Some adhesives used in this manner may be contaminated with organic solvents and suffer from various health and environmental drawbacks due to the use of organic solvents.

[0003] US 7,837,831 discloses paper towels made from an aqueous dispersion containing olefin polymers and natural or synthetic cellulose fibers.

[0004] There is a need for a method for recycling polyolefin foams, which employs an aqueous adhesive that effectively binds together fragments of polyolefin foams to form new, useful polyolefin foam articles. Summary of the Invention

[0005] The following is the content of the invention.

[0006] The first aspect of this invention is a method for recycling polyolefin foam, comprising: a) Provide a mixture containing i) Fragments of polyolefin foam, and ii) An aqueous composition comprising dispersed polyolefin particles, and b) Remove water from the mixture.

[0007] The second aspect of the present invention is a composition comprising... i) Fragments of polyolefin foam, and ii) Aqueous composition containing dispersed polyolefin particles.

[0008] The third state sample of the present invention is an article formed by a method comprising removing water from the composition of the second state sample. Simple Explanation of the Diagram

[0009] none Implementation

[0010] The following are specific embodiments of the present invention.

[0011] As used herein, unless the context clearly indicates otherwise, the following terms have the specified definitions.

[0012] As used herein, a polymer is a relatively large molecule composed of reaction products of smaller chemical repeating units. Polymers can have linear, branched, star-shaped, cyclic, hyperbranched, cross-linked, or combinations thereof structures; polymers can have a single type of repeating unit (“homogene”), or can have more than one type of repeating unit (“copolymer”). Copolymers can have various types of repeating units arranged randomly, sequentially, in blocks, otherwise, or any mixture or combination thereof. Polymers have a number average molecular weight of 1,000 or higher.

[0013] As used in this article, "polymer weight" means the dry weight of the polymer.

[0014] As used herein, a "thermoplastic" polymer is a polymer that meets the following criteria: A thermoplastic polymer is solid in the temperature range from absolute zero to Tsolid, with Tsolid below 200°C. At temperatures equal to or above Tsolid (Tflow), a thermoplastic polymer becomes soft enough to be shaped under gravity or mechanical forces. When the thermoplastic polymer is cooled back to or below Tsolid, it largely retains its new shape. This softening can be caused by glass transition, melt transition, other softening processes, or combinations thereof.

[0015] Molecules that can react with each other to form repeating units of a polymer are referred to herein as "monomers". The repeating units formed in this way are referred to herein as "polymerized units" of monomers.

[0016] An olefin is a hydrocarbon compound that contains exactly one carbon-carbon double bond and no carbon-carbon triple bonds. Olefins can be linear, cyclic, branched, or a combination thereof. A polyolefin is a polymer in which 40% by weight or more of the polymeric units are olefins.

[0017] As used herein, "vinyl ester" is a compound having the formula R 3C-C(O)-O-CR=CR 2, wherein each R group is, independently of all other R groups, hydrogen, or a substituted or unsubstituted organic group. As used herein, "(meth)acrylic acid" means acrylic acid, methacrylic acid, or a mixture thereof. As used herein, "(meth)acrylic ester" means an ester of (meth)acrylic acid, wherein the ester group is a substituted or unsubstituted C1-C20 alkyl group. As used herein, "diene" is a hydrocarbon compound having exactly two carbon-carbon double bonds and no carbon-carbon triplets. Dienes can be linear, branched, cyclic, or a combination thereof.

[0018] As used herein, a carboxylic acid compound is any of the following: a carboxylic acid having a carboxyl group in a neutral, cationic, or mixture thereof; a carboxyl salt; a carboxyl ester; or a mixture thereof. A sulfonate compound is a compound having a sulfonic acid group, which may be in a neutral, anionic, salt, ester, or mixture thereof.

[0019] As used herein, a "foam" is a solid article containing multiple cells. A cell is a volume filled by gas, partially or completely surrounded by a solid material. When 50% or more of the cells are completely surrounded by a solid material, the foam is called a "closed-cell" foam. Other foams are called "open-cell" foams. A foam in which 50% or more by weight is a polyolefin is called a "polyolefin foam." If a polyolefin foam contains more than one polyolefin, the polyolefin having the largest weight percentage in the foam is referred to herein as the "major" polyolefin in the foam. If a polyolefin foam contains exactly one polyolefin, that polyolefin is the major polyolefin.

[0020] Fragments of polyolefin foam with a size not exceeding 20 cm are referred to herein as “fragments”. Fragments of polyolefin foam may be found in the form of discoverable fragments, or larger fragments of polyolefin foam may be reduced to fragments, for example by one or more mechanical processes, such as grinding, cutting, shearing, breaking, other mechanical processes, or any combination thereof.

[0021] As used herein, "particle" refers to a discrete item. A particle can be solid or liquid. As used herein, the "diameter" of a particle is considered the diameter of a virtual sphere with the same volume as a real particle. The "height-to-width" ratio of a particle is the ratio of its maximum dimension to its minimum dimension. If its height-to-width ratio is 2:1 or less, the particle is referred to herein as "non-fibrous." By weight, "polyolefin particles" contain 50% by weight or more polyolefin.

[0022] As used herein, an "aqueous" composition is a composition containing 30% by weight or more water by weight. An aqueous medium is a continuous liquid medium containing 50% by weight or more water by weight. When particles are distributed in a liquid medium, the particles are referred to herein as being "dispersed" in the liquid medium. Particles dispersed in a liquid medium can form compositions commonly labeled as slurries, dispersions, emulsions, latexes, some other types of compositions, or combinations thereof. The aggregate of particles dispersed in a liquid medium is characterized by its volume-average diameter, which can be measured by light scattering, for example, using a Coulter LS230 device (Beckman Coulter Co., Indianapolis, IN, USA). The particle size distribution quotient is defined herein as the quotient obtained by dividing the volume-average particle size Dv by the number-average particle size Dn.

[0023] The melting temperature of the polymer was measured using differential scanning calorimetry (DSC). An endothermic peak was observed at the melting temperature.

[0024] The crystallinity of a polymer is measured by observing the heat of fusion at the melting point as observed in the DSC assessment. "Crystallinity" is determined by normalizing the observed heat of fusion to the heat of fusion of a 100% crystallized sample of the same polymer, and is expressed as a percentage.

[0025] The weight-average molecular weight (Mw) of a polymer sample is measured by light scattering in a diluted polymer solution using the intercept of a Zim plot of scattering intensity versus polymer concentration and scattering angle. The polydispersity index is defined as the quotient obtained by dividing the weight-average molecular weight (Mw) by the number-average molecular weight (Mn).

[0026] The glass transition temperature (Tg) of the polymer sample was measured by DSC at 10 °C / min and used as the midpoint of the step change in the heat flux curve.

[0027] The melt index ("I2") of the polymer is measured according to ASTM D1238, conditions 190°C / 2.16 kg. I2 is expressed in grams of melt per 10 minutes (g / 10 min).

[0028] The ratios presented in this document are represented as follows. For example, if a ratio is referred to as 3:1 or greater, then the ratio can be 3:1, or 5:1, or 100:1, but not 2:1. This representation can be expressed in general terms as follows. When a ratio is referred to as X:1 or greater in this document, it means that the ratio is Y:1, where Y is greater than or equal to X. For another example, if a ratio is referred to as 15:1 or less, then the ratio can be 15:1, or 10:1, or 0.1:1, but not 20:1. Generally speaking, when a ratio is referred to as W:1 or less in this document, it means that the ratio is Z:1, where Z is less than or equal to W.

[0029] Preferably, the volume average particle size of the dispersed particles in the aqueous composition is 10 micrometers or less; more preferably 5 micrometers or less; more preferably 2.5 micrometers or less; more preferably 1.5 micrometers or less. Preferably, the volume average particle size of the dispersed particles in the aqueous composition is 0.05 micrometers or greater; more preferably 0.1 micrometers or greater; more preferably 0.2 micrometers or greater. Preferably, the particle size distribution quotient of the dispersed particles in the aqueous composition is 2 or less; more preferably 1.9 or less; more preferably 1.7 or less; more preferably 1.5 or less.

[0030] Examples of suitable aqueous compositions containing dispersed polyolefin particles are disclosed, for example, in U.S. Patents 5,688,842, 8,053,503, and 8,163,837.

[0031] Based on the total weight of the particles, the polyolefin particles preferably contain the following amounts of polyolefin: 50% by weight or more; more preferably, 60% by weight or more; more preferably, 70% by weight or more; more preferably, 80% by weight or more; more preferably, 90% by weight or more.

[0032] Preferably, the polyolefin particles contain one or more "first polyolefins". In the "first polyolefin", the polymeric units of the olefin are present in the following amounts based on the weight of the first polyolefin: 70% by weight or more; more preferably, 80% by weight or more; more preferably, 90% by weight or more. Preferably, the first polyolefin contains polymeric units of one or more primary monomers, optionally one or more comonomers, and optionally one or more additional monomers. The primary monomer is ethylene, propylene, or a mixture thereof. The comonomer is selected from the group consisting of one or more dienes, one or more vinyl esters, one or more compounds of the formula H₂C═CHR (wherein R is a C₂-C₂₀ straight-chain, branched, or cyclic alkyl group; or a C₆-C₂₀ aryl group), and mixtures thereof.

[0033] In the first polyolefin, preferably, based on the weight of the polymerization units of the primary monomer, the polymerization units of the primary monomer are 90% to 100% ethylene polymerization units or 90% to 100% propylene polymerization units; more preferably, 90% to 100% ethylene polymerization units; even more preferably, 100% ethylene polymerization units. In the first polyolefin, preferably, based on the weight of the first polyolefin, the amount of polymerization units of the primary monomer is 65% or more; more preferably, 75% or more. In the first polyolefin, preferably, based on the weight of the first polyolefin, the amount of polymerization units of the primary monomer is 100% or less; more preferably, 99% or less; even more preferably, 90% or less.

[0034] Regarding one or more comonomers, if one or more dienes are used in the first polyolefin, they are preferably C4-C20 linear, branched, or cyclic dienes. If one or more vinyl esters are used in the first polyolefin, they are preferably vinyl acetate. If one or more compounds having the formula H₂C═CHR (as defined above) are used in the first polyolefin, they are preferably 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 3-methyl-1-pentene, 1-heptene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and mixtures thereof; more preferably 1-heptene, 1-hexene, 1-octene, 1-decene, 1-dodecene, and mixtures thereof. In the first polyolefin, the comonomer preferably includes one or more compounds of the formula H₂C═CHR. In the first polyolefin, preferably, the amount of the compound of formula H₂C═CHR, based on the weight of the comonomer, is 50% by weight or more; more preferably, 75% by weight or more; more preferably, 90% by weight or more; more preferably, 100% by weight. Preferably, based on the weight of the first polyolefin, the amount of polymeric units of the comonomer in the first polyolefin is 0 to 25% by weight, more preferably 1% to 25% by weight.

[0035] Regarding the additional monomers in the first polyolefin, preferably, any additional monomers used are different from any primary monomers and different from any comonomers. Preferably, the first polyolefin contains a small amount or no polymerization units of additional monomers. That is, the amount of polymerization units of additional monomers present in the first polyolefin, based on the weight of the first polyolefin, is preferably 0 to 10% by weight; more preferably, 0 to 1% by weight; and even more preferably, 0% by weight.

[0036] Preferably, the first polyolefin is thermoplastic. Preferably, the crystallinity of the first polyolefin is less than 50%, more preferably less than 25%. Preferably, the weight-average molecular weight of the first polyolefin is 15,000 or higher; more preferably, 20,000 or higher. Preferably, the weight-average molecular weight of the first polyolefin is 5,000,000 or lower; more preferably, 1,000,000 or lower. Preferably, the molecular weight polydispersity index of the first polyolefin is 1.01 or higher; more preferably, 1.5 or higher; more preferably, 1.8 or higher. Preferably, the molecular weight polydispersity index of the first polyolefin is 40 or lower; more preferably, 20 or lower; more preferably, 10 or lower.

[0037] Preferably, the glass transition temperature of the first polyolefin is 50°C or lower; more preferably, 40°C or lower. Preferably, the glass transition temperature of the first polyolefin is 25°C or higher; more preferably, 30°C or higher. Preferably, the melting temperature of the first polyolefin is 140°C or lower; more preferably, 130°C or lower; more preferably, 120°C or lower. Preferably, the melt index of the first polyolefin, in grams per 10 minutes, is 0.001 or higher; more preferably, 0.5 or higher; more preferably, 100 or higher. Preferably, the melt index of the first polyolefin, in grams per 10 minutes, is 1,000 or lower; more preferably, 800 or lower; more preferably, 700 or lower.

[0038] Examples of suitable first polyolefins include, for example, the following: heterogeneous branched polyolefins, including linear low-density polyethylene (LLDPE) and copolymers; heterogeneous branched ultra-low linear density polyethylene (ULDPE); homogeneous branched linear copolymers of ethylene and one or more α-olefins other than ethylene; and substantially homogeneous branched linear copolymers of ethylene and one or more α-olefins other than ethylene.

[0039] Preferably, the aqueous composition further contains one or more dispersants. The dispersant molecules may be soluble in the continuous aqueous phase, or may be attached to one or more polyolefin particles, or may be partially present on the surface of the polyolefin particles and partially present in the continuous aqueous phase. Suitable dispersants include non-polymeric carboxylic acid compounds, non-polymeric sulfonate compounds, olefin / (meth)acrylic acid copolymers, sulfated or phosphated polyoxyethylene alcohols, ethylene oxide / propylene oxide / ethylene oxide block copolymers, primary and secondary alcohol ethoxylates, alkyl glycosides, alkyl glycerides, and mixtures thereof.

[0040] In non-polymeric carboxylic acid compounds, it is preferable that the carboxylic acid moiety of its molecule contains 8 or more carbon atoms; more preferably, 12 or more carbon atoms; even more preferably, 15 or more carbon atoms. In non-polymeric carboxylic acid compounds, it is preferable that the carboxylic acid moiety of its molecule contains 60 or fewer carbon atoms; more preferably, 30 or fewer carbon atoms. In non-polymeric carboxylic acid compounds, it is preferable that the cation is selected from salts of alkali metal cations, alkaline earth cations, ammonium cations, alkylammonium cations, or mixtures thereof.

[0041] Preferably, the dispersant comprises one or more olefin / (meth)acrylic acid copolymers. In the olefin / (meth)acrylic acid copolymer, it is more preferably a copolymer comprising polymeric units of ethylene, propylene, or mixtures thereof. In the olefin / (meth)acrylic acid copolymer, preferably, based on the weight of all polymeric units of the olefin monomer, the polymeric units of the olefin monomer are 90% to 100% by weight of ethylene polymeric units, or 90% to 100% by weight of propylene polymeric units; more preferably, 90% to 100% by weight of ethylene polymeric units; even more preferably, 100% by weight of ethylene polymeric units. In the olefin / (meth)acrylic acid copolymer, preferably, based on the weight of the olefin / (meth)acrylic acid copolymer, the amount of polymeric units of the olefin monomer is preferably 40% by weight or more; more preferably, 50% by weight or more. In the olefin / (meth)acrylic acid copolymer, preferably, the amount of polymeric units of the olefin monomer is 98% by weight or less, more preferably 95% by weight or less, more preferably 90% by weight or less, and more preferably 70% by weight or less.

[0042] In the olefin / (meth)acrylic acid copolymer, preferably, the olefin / (meth)acrylic acid copolymer contains 2% by weight or more of (meth)acrylic acid polymeric units based on the weight of the olefin / (meth)acrylic acid copolymer. More preferably, the amount of (meth)acrylic acid polymeric units in the olefin / (meth)acrylic acid copolymer is 5% by weight or more; more preferably, 10% by weight or more; more preferably, 30% by weight or more. Preferably, the amount of (meth)acrylic acid polymeric units in the olefin / (meth)acrylic acid copolymer is 60% by weight or less; more preferably, 50% by weight or less.

[0043] The olefin / (meth)acrylic acid copolymer optionally contains one or more additional monomer polymerization units; that is, monomers other than olefin monomers and (meth)acrylic acid. Preferably, the olefin / (meth)acrylic acid copolymer contains a small amount or no additional monomer polymerization units. That is, preferably, the amount of additional monomer polymerization units present in the olefin / (meth)acrylic acid copolymer is 0 to 10% by weight, more preferably, 0 to 1% by weight, and even more preferably, 0% by weight.

[0044] Preferably, the aqueous composition contains one or more first polyolefins and one or more dispersants. Preferably, the weight ratio of the first polyolefin to the dispersant is 300:1 or lower. Preferably, the weight ratio of the first polyolefin to the dispersant is 0.5:1 or higher.

[0045] When the dispersant contains one or more olefin / (meth)acrylic acid copolymers, preferably, the weight ratio of the first polyolefin to the olefin / (meth)acrylic acid copolymer is 20:1 or lower; more preferably, 10:1 or lower; even more preferably, 6:1 or lower. When the dispersant contains one or more olefin / (meth)acrylic acid copolymers, preferably, the weight ratio of the first polyolefin to the dispersant is 0.5:1 or higher; more preferably, 0.75:1 or higher; even more preferably, 1:1 or higher.

[0046] When the dispersant contains one or more non-polymeric carboxylic acid compounds, preferably, the weight ratio of the first polyolefin to the non-polymeric carboxylic acid compound is 300:1 or lower; more preferably, 200:1 or lower; even more preferably, 120:1 or lower. When the dispersant contains one or more non-polymeric carboxylic acid compounds, preferably, the weight ratio of the first polyolefin to the non-polymeric carboxylic acid compound is 5:1 or higher; more preferably, 10:1 or higher; even more preferably, 16:1 or higher.

[0047] The aqueous composition contains a continuous liquid medium and also contains dispersed polyolefin particles. The amount of water in the continuous liquid medium is preferably 50% by weight or more; more preferably 75% by weight or more; and even more preferably 85% by weight or more.

[0048] Preferably, the amount of polyolefin in the aqueous composition is 25% by weight or higher, more preferably 30% by weight or higher, more preferably 35% by weight or higher, and more preferably 40% by weight or higher, based on the weight of the aqueous composition. More preferably, the amount of polyolefin in the aqueous composition is 75% by weight or lower, more preferably 70% by weight or lower, more preferably 60% by weight or lower, and more preferably 50% by weight or lower, based on the weight of the aqueous composition.

[0049] Preferably, the pH of the aqueous component is 5 or higher; more preferably, 7 or higher. Preferably, the pH of the aqueous component is 11.5 or lower; more preferably, 11 or lower. Optionally, the pH of the aqueous component can be adjusted by including one or more acids or bases in the aqueous component.

[0050] This invention also relates to the use of fragments of polyolefin foam. Preferably, the polyolefin foam is recycled. Preferably, based on the weight of the foam, the polyolefin is present in the foam in the following amounts: 60% by weight or more; more preferably, 70% by weight or more; more preferably, 80% by weight or more. In the polyolefin foam, preferably, based on the weight of the polymerization units of the primary monomer, the amount of the polymerization units of the primary monomer is 90% to 100% by weight of ethylene polymerization units, or 90% to 100% by weight of propylene polymerization units; more preferably, 90% to 100% by weight of ethylene polymerization units; more preferably, 100% by weight of ethylene polymerization units. In the polyolefin foam, preferably, based on the weight of all polymerization units in the polyolefin foam, the amount of the polymerization units of the primary monomer is 75% to 100% by weight; more preferably, 90% to 100% by weight. In the polyolefin foam, preferably, the amount of the comonomer polymeric units is 0% to 25% by weight, based on the weight of all polymeric units in the polyolefin foam; more preferably, 0% to 10% by weight. Preferably, based on the weight of the polyolefin foam, the polyolefin in the polyolefin foam contains 80% or more, or 90% or more, low-density polyethylene (LDPE).

[0051] Preferably, the main polyolefin in the polyolefin foam is crosslinked or has a melt temperature (Tmfoam) of 150°C or lower; more preferably, the crosslinked or has a Tmfoam of 120°C or lower. Preferably, the main polyolefin in the polyolefin foam is crosslinked or has a melt temperature (Tmfoam) of 60°C or higher; more preferably, the crosslinked or has a Tmfoam of 80°C or higher.

[0052] The polyolefin foam may optionally contain one or more nucleating agents. Suitable nucleating agents include, for example, talc, citric acid, and sodium bicarbonate. The amount of nucleating agent (if present) in the polyolefin foam is preferably 15% by weight or less, based on the weight of the polyolefin foam.

[0053] Polyolefin foams may optionally contain one or more blowing agents. Suitable blowing agents are, for example, glyceryl monostearate. The amount of blowing agent (if present) in the polyolefin foam is preferably 5% by weight or less, based on the weight of the polyolefin foam.

[0054] Polyolefin foams can be open-cell, closed-cell, or a combination thereof. Suitable polyolefin foams can be, for example, high-density or low-density foams. High-density foams typically have a volume-average pore size of 50 to 200 micrometers. High-density foams typically have a density greater than 240 kg / m³ (15 lb / ft³). Low-density foams typically have a volume-average pore size of 100 to 3,000 micrometers. Low-density foams typically have a density of 8 kg / m³ (0.5 lb / ft³) to 240 kg / m³ (15 lb / ft³).

[0055] The polyolefin in the polyolefin foam can be thermoplastic or cross-linked. Either type of foam is suitable for this invention. Particular interest in the practice of this invention lies with cross-linked foams, because cross-linked foams are generally not recyclable by melting and reforming, and therefore this invention is advantageous because it provides a method for manufacturing new useful articles from previously used cross-linked foams.

[0056] In practice, the polyolefin foam exists in the form of a plurality of fragments. Each fragment can be characterized by its maximum size ("DMAX"). The set of fragments can be characterized by D90, the size of which is set such that 90% or more of the fragments by weight of all fragments have a DMAX equal to or less than D90. Preferably, the D90 of the set of fragments of the polyolefin foam is 20 cm or less; more preferably, 12 cm or less; even more preferably, 7 mm or less. Preferably, 90% or more of the fragments by weight of all fragments are non-fibrous.

[0057] In some embodiments, the foam is manufactured, for example, by extrusion into a relatively large article, such as a thin sheet, plate, or slab; and then mechanically reduced to smaller fragments. It is understood that, apart from size reduction, these foam fragments will retain the characteristics of the original foam article, such as pore size, foam density, and porosity.

[0058] This invention relates to the use of mixtures of polyolefin foam fragments and aqueous components. The mixture can be manufactured by any method. Examples of suitable methods include, for example, blending (e.g., placing the aqueous component and polyolefin foam fragments together in a container and stirring the mixture); dip coating (e.g., placing the aqueous component in a first container, immersing the polyolefin foam fragments in the aqueous component until the polyolefin foam fragments are coated with the aqueous component, and then transferring the coated polyolefin foam fragments to another container); spraying (e.g., spraying the aqueous component onto the polyolefin foam fragments); other methods; and combinations thereof.

[0059] In a preferred embodiment, one or another of the following conditions ("I" or "II") exists: I) The dispersed polyolefin particles contain 50% by weight or more ethylene polymer units, based on the total weight of all polymer units in all polymers within the dispersed polyolefin particles. and The fragments of the polyolefin foam contain 50% by weight or more ethylene polymer units, based on the total weight of all polymer units in the fragments. or II) The dispersed polyolefin particles contain 50% by weight or more propylene polymeric units based on the total weight of all polymeric units in all polymers within the dispersed polyolefin particles. and The fragments of polyolefin foam contain 50% by weight or more of propylene polymer units, based on the total weight of all polymer units in the fragments. Condition I is preferred. When practicing Condition I, preferably, based on the total weight of all polymers in the dispersed polyolefin particles, the amount of ethylene polymer units is 60% by weight or more; more preferably, 70% by weight or more; even more preferably, 80% by weight or more. When practicing Condition I, preferably, based on the total weight of all polymer units in the polyolefin foam fragments, the amount of ethylene polymer units in the polyolefin foam is 60% by weight or more; more preferably, 70% by weight or more; even more preferably, 80% by weight or more.

[0060] When practicing condition II, preferably, based on the total weight of all polymers in the dispersed polyolefin particles, the amount of propylene polymer units in all polymers is 60% by weight or more; more preferably, 70% by weight or more; even more preferably, 80% by weight or more. When practicing condition II, preferably, based on the total weight of all polymer units in the polyolefin foam fragments, the amount of propylene polymer units in the polyolefin foam is 60% by weight or more; more preferably, 70% by weight or more; even more preferably, 80% by weight or more.

[0061] The mixture of the aqueous component and polyolefin foam fragments can be characterized by the weight ratio of the polyolefin in the aqueous component to the weight of the polyolefin foam. Preferably, this ratio is 0.2:1 or higher; more preferably, 0.5:1 or higher; more preferably, 0.75:1 or higher. Preferably, this ratio is 5:1 or lower; more preferably, 3:1 or lower.

[0062] The present invention relates to the removal of water from a mixture of an aqueous component and polyolefin foam particles. Preferably, water is removed by a process involving water evaporation. To accelerate water removal, the mixture may be subjected to one or more of the following: a temperature above 30°C; a flowing airflow; and a combination thereof.

[0063] When using temperatures above 30°C, 60°C or higher is preferred; more preferably 70°C or higher. When using temperatures above 30°C, 150°C or lower is preferred; more preferably 125°C or lower. Temperatures above 30°C can be achieved by any method. Some suitable methods include, for example, exposure to radiation (such as infrared radiation), exposure to heated gases (such as heated air), other heating methods, and combinations thereof.

[0064] When a flowing airflow is required, a suitable method is to place the mixture in an oven that mechanically forces air to move within the oven, such as, for example, a convection oven. When the mixture is placed in an oven that mechanically forces air to move within the oven, the mixture can be simultaneously exposed to both the flowing airflow and a temperature above 30°C. Alternatively, the mixture can be exposed to the flowing airflow in an environment other than an oven (with or without simultaneous exposure to a temperature above 30°C). Alternatively, a flowing airflow may not be used.

[0065] When the mixture is exposed to temperatures above 30°C, preferably, the mixture reaches a temperature equal to or greater than the Tflow of the first polyolefin. It is considered that when the mixture reaches the Tflow of the first polyolefin or a higher temperature, some or all of the particles containing the first polyolefin tend to fuse together and bind the fragments of the polyolefin foam into a single block.

[0066] It has been considered that exposure to temperatures above 30°C will facilitate the fusion of the first polyolefin particles and the removal of water from the mixture. These effects can be achieved in any sequential manner, simultaneously, or in any combination thereof. For example, the mixture may first be exposed to optimized dehydration conditions (e.g., relatively low temperatures and relatively high airflow rates), and then to optimized particle fusion conditions (e.g., relatively high temperatures). In another example, the mixture may first be exposed to optimized particle fusion conditions and then to optimized dehydration conditions. In yet another example, conditions that allow particle fusion and dehydration to occur simultaneously may be selected. It has been considered that when optimized or favorable conditions for one effect (e.g., dehydration) are applied, another process (e.g., particle fusion) will occur to some extent simultaneously.

[0067] When the mixture is exposed to temperatures above 30°C, and when the main polyolefin in the polyolefin foam is a thermoplastic polyolefin, the maximum temperature Tmax achievable by the mixture should satisfy Tmax < (T2 - 10°C), where T2 is the Tsoft of the main polyolefin in the polyolefin foam. It is anticipated that keeping Tmax below 10°C (which is below T2) will allow the fragments of the polyolefin foam to maintain their foamed structure without collapsing.

[0068] Alternatively, the mixture may be subjected to mechanical stress when the temperature is sufficient to soften some or all of the polyolefins from the particles of the aqueous component.

[0069] After removing water from the mixture, and if it has been heated back to an ambient temperature of approximately 25°C, the remaining components are considered the finished product herein. It is considered that some water may be retained in the finished product. Preferably, the amount of water in the finished product is 20% by weight or less; more preferably, 10% by weight or less; even more preferably, 5% by weight or less.

[0070] Fragments of polyolefin foam can be placed, for example, in a container used as a mold to determine the final shape of the finished product. These fragments can be placed in the container before or after contacting the polyolefin foam with the aqueous component.

[0071] The following are examples of the present invention. Unless otherwise stated, the operation was carried out at room temperature (approximately 23°C).

[0072] Use the following materials: • "Binder" = HYPOD™ 8501 acid-modified ethylene copolymer polyolefin dispersant, approximately 45% by weight solids, from Dow Chemical Company. • Recycled foam: Previously manufactured polyolefin foam has been reduced to fragments with a D90 of less than 5 mm. Example 1

[0073] 97 grams of binder were mixed with the recycled foam in a bath until a uniform coating of the foam particles was achieved. The binder-coated foam particles were placed in a heavy-duty aluminum tray measuring 21.6 cm × 11.7 cm × 7.0 cm (8.5 inch × 4.6 inch × 2.75 inch). Using another tray as a lid, the sample was placed in a convection oven set to 90°C for 50 min, with a 1.8 kg (4 pound) weight placed on top of the lid. The lid was then removed, and the sample was dried in the 90°C oven for 2 hours. Example 2

[0074] Except for perforating the lid, it is the same as in Example 1. Example 3

[0075] The binder was evenly sprayed onto 15 grams of recycled foam. The sprayed foam particles were placed in an oven at 90°C for 30 minutes. The coated foam was then weighed, and the result was 16.7 grams, indicating that 1.6 grams of polymer came from 15 grams of recycled foam particles coated with the binder. The coated foam particles were placed in a dish, and then the dish was covered with a lid. A 1.8 kg (4 lb) weight was placed on the lid. The dish was placed in an oven at 90°C for 10 minutes. The 1.8 kg (4 lb) weight was then placed on the lid again, and the dish was placed in an oven at 90°C for another 10 minutes. Example 4

[0076] 15 grams of foam were immersed in an adhesive bath and mixed until a uniform coating was obtained. The coated foam particles were placed in an oven at 90°C for 50 minutes. The coated foam particles were then weighed to 30 grams, indicating that the 15 grams of polymer originated from 15 grams of recycled foam coated with an adhesive. Next, the coated foam particles were placed in a covered dish with a 1.8 kg (4 lb) weight in the oven at 90°C for 5 minutes. The 1.8 kg (4 lb) weight was then placed on the lid, and the dish was placed in the oven at 90°C for another 10 minutes.

[0077] The result of Examples 1 through 4 is a solid block containing polyolefin foam that is robust when handled and appears suitable for any of a variety of applications, such as protective encapsulation (e.g., padding for electronic products during transport), building and construction applications (e.g., pipe insulation), recreational items (e.g., swimming floats and fitness mats), and automotive applications.

[0078] none

Claims

1. A method for recycling polyolefin foam, comprising a) providing a mixture comprising i) fragments of polyolefin foam, and ii) an aqueous composition comprising dispersed polyolefin particles having a volume average particle size of 0.05 micrometers to 10 micrometers, and b) removing water from the mixture.

2. The method of claim 1 further comprises the following step: c) causing or allowing some or all of the dispersed polyolefin particles to fuse together.

3. The method of claim 1, wherein the dispersed polyolefin particles comprise a first polyolefin, which, by weight of the first polyolefin, comprises the following polymeric units: i) 65% to 99% by weight of ethylene, or propylene, or mixtures thereof; ii) 1% to 25% by weight of one or more monomers selected from the group consisting of: one or more dienes, one or more ethylene esters, one or more compounds of the formula H2C═CHR, wherein R is a C2-C20 straight-chain, branched, or cyclic alkyl group, or a C6-C20 aryl group, or mixtures thereof; and iii) 0% to 10% by weight of one or more monomers different from i) and ii).

4. The method of claim 1, wherein the aqueous composition further comprises one or more olefin / (meth)acrylate copolymers.

5. The method of claim 1, wherein the dispersed polyolefin particles contain 50% by weight or more of ethylene polymeric units based on the total weight of all polymeric units in all polymers in the dispersed polyolefin particles, and wherein the fragments of the polyolefin foam contain 50% by weight or more of ethylene polymeric units based on the total weight of all polymeric units in the fragments of the polyolefin foam.

6. The method of claim 1, wherein the dispersed polyolefin particles contain 50% by weight or more propylene polymer units based on the total weight of all polymer units in all polymers in the dispersed polyolefin particles, and wherein the fragments of the polyolefin foam contain 50% by weight or more propylene polymer units based on the total weight of all polymer units in the fragments of the polyolefin foam.

7. The method of claim 1, wherein the fragments of the polyolefin foam comprise 80% by weight or more low-density polyethylene based on the total weight of the fragments.

8. A composition comprising i) fragments of a polyolefin foam and ii) an aqueous composition comprising dispersed polyolefin particles having a volume average particle size of 0.05 micrometers to 10 micrometers.

9. An article formed by a method comprising a self-component for dehydration, wherein the component is the component of claim 8.