WO2015061127A1

WO2015061127A1 - Viscoelastic foam system

Info

Publication number: WO2015061127A1
Application number: PCT/US2014/060896
Authority: WO
Inventors: Sergio Franyutti; Thomas Clark; James VANDERMYDE
Original assignee: Basf Se
Priority date: 2013-10-21
Filing date: 2014-10-16
Publication date: 2015-04-30
Also published as: TW201538649A

Abstract

A viscoelastic foam system comprises a viscoelastic foam and spheres dispersed in the viscoelastic foam. Each sphere comprises a gas-filled spherical particle and a polyurethane coating disposed about the gas-filled spherical particle. The polyurethane coating comprises the reaction product of a prepolymer and a polyol component. The prepolymer comprises the reaction product of an isocyanate component and an isocyanate-reactive component, and the prepolymer comprises from 2.5 to 3.6 % by weight of urethane groups based on 100 % by weight of the prepolymer. The polyurethane coating disposed about the gas-filled spherical particle has a shore OO hardness value of from about 20 to about 50 measured according to ASTM D2240 type OO hardness scale.

Description

VISCOELASTIC FOAM SYSTEM

FIELD OF THE DISCLOSURE

[0001] The present disclosure generally relates to a viscoelastic foam system. More specifically, the present disclosure relates to a viscoelastic foam system comprising a viscoelastic foam and spheres dispersed in the viscoelastic foam.

BACKGROUND

[0002] Viscoelastic foams may be used in various articles such as mattresses, pillows, cushions, stuffed animals, and the like. In some instances, the viscoelastic foam is a memory foam that exhibits unique compression and recovery properties. As a memory foam, the viscoelastic foam may, for example, conform to the shape of a body (e.g. a person's body) disposed on the viscoelastic foam in response to heat and/or pressure generated from the body, and then recover to its original shape after the body has been removed from the viscoelastic foam. While the body is disposed on the viscoelastic foam, however, the viscoelastic foam may retain heat that is generated by the body. The heat retained by the viscoelastic foam may, in some instances, cause the body to overheat and/or experience some discomfort.

SUMMARY OF THE DISCLOSURE AND ADVANTAGES

[0003] The present disclosure provides a viscoelastic foam system comprising a viscoelastic foam and spheres dispersed in the viscoelastic foam. Each sphere comprises a gas-filled spherical particle and a polyurethane coating disposed about the gas-filled spherical particle. The polyurethane coating comprises the reaction product of i) a prepolymer comprising the reaction product of an isocyanate component and an isocyanate-reactive component, the prepolymer comprising from 2.5 to 3.6 % by weight of urethane groups based on 100 % by weight of the prepolymer, and ii) a polyol component. The polyurethane coating has a shore 00 hardness value of from about 20 to about 50 measured according to ASTM D2240 type OO hardness scale.

[0004] The viscoelastic foam system may be used for a variety of applications, such as for bedding applications including mattresses, pillows, blankets, and/or the like. The viscoelastic foam system may also be used, for example, for cushions, furniture, toys (e.g. stuffed animals), medical equipment (e.g. medical table pads), etc. Without being bound to any theory, it is believed that the spheres having the polyurethane coating disposed about the gas-filled spherical particles act as a localized heat sink within the viscoelastic foam. As a localized heat sink, the spheres actively remove (e.g. absorb) heat from the viscoelastic foam. Since heat is being removed, the spheres impart a cooling effect on the viscoelastic foam. It is believed that the cooling effect of the spheres will improve the overall comfort level of the body (e.g., a person) disposed on the viscoelastic foam system. Additionally, the presence of the spheres inside the viscoelastic foam improves air flow through the matrix of the viscoelastic foam. It is believed that this improved air flow also contributes to the cooling effect imparted on the viscoelastic foam by the spheres.

DETAILED DESCRIPTION OF THE PRESENT DISCLOSURE

[0005] The viscoelastic foam system, as disclosed herein, generally comprises spheres dispersed in a viscoelastic foam. As previously mentioned, it is believed that the spheres impart a cooling effect on the viscoelastic foam. Accordingly, the term "sphere/s" may be referred to as "cooling sphere/s".

[0006] The spheres for the viscoelastic foam system generally comprise gas-filled spherical particles, where each gas-filled spherical particle has a polyurethane coating disposed about the gas-filled spherical particle. The gas-filled spherical particles may be selected from hollow spheres, each comprising a shell that encapsulates a gas. In one example, the gas-filled spherical particles each comprise a thermoplastic shell encapsulating a gas, such as an inert gas. Additionally, the gas-filled spherical particles have an effective particle size of from about 1 to about 100 μιη, and more typically, from about 30 to about 50 μιη. The gas-filled spherical particles also have a density of from about 0.01 to about 0.05 grams per cubic centimeter (g/cc), and more typically, from about 0.038 to about 0.046 g/cc. Suitable gas-filled spherical particles are commercially available by the tradename EXPANCEL® 551 DE40 d42 from AkzoNobel N.V. (Amsterdam, the Netherlands). The EXPANCEL® 551 DE40 d42 spherical particles are light weight, gas-filled, thermoplastic, hollow spherical particles that have a whitish color. In an example, the EXPANCEL® 551 De 40 d42 spherical particles have a density of about 0.03 to about 0.06 g/cc. In another example, the EXPANCEL® 551 De 40 d42 spherical particles have a density of about 0.038 to about 0.046 g/cc. In yet another example, the EXPANCEL® 551 De 40 d42 spherical particles have a density of about 0.045 g/cc. When the EXPANCEL® 551 DE40 d42 spherical particles are heated, the thermoplastic shell softens while the gas, which is encapsulated by the shell, increases in pressure. This increase in pressure of the encapsulated gas causes the spherical particles to expand. It is believed that the generally light weight, hollow, spherical particles permit better air flow between adjacent spherical particles when the spheres (which include the gas-filled spherical particles) are dispersed in the viscoelastic foam.

[0007] The polyurethane coating is disposed about the gas-filled spherical particles to form the spheres. When disposed about the gas-filled spherical particles, the polyurethane is partially or entirely coated on the gas-filled spherical particles. Typically, the polyurethane coating is disposed about the entire surface of each gas- filled spherical particle dispersed in the viscoelastic foam. It is to be understood, however, that the polyurethane coating may be disposed about at least a portion of the surface of the gas-filled spherical particles dispersed in the viscoelastic foam. In some instances, the polyurethane coating may be disposed about the entire surface of some of the gas-filled spherical particles dispersed in the viscoelastic foam, and may be disposed about a portion of the surface of other gas-filled spherical particles dispersed in the viscoelastic foam.

[0008] Furthermore, the polyurethane coating is typically disposed about all of the gas-filled spherical particles that are dispersed in the viscoelastic foam. It is to be understood, however, that not all of the gas-filled spherical particles are required to have the polyurethane coating disposed about the gas-filled spherical particles. In an example, about 100% of the gas-filled spherical particles dispersed in the viscoelastic foam has the polyurethane coating disposed about the gas-filled spherical particles. In another example, at least 95% of the gas-filled spherical particles dispersed in the viscoelastic foam has the polyurethane coating disposed about the gas-filled spherical particles.

[0009] The polyurethane coating disposed about the gas-filled spherical particles generally comprises the reaction product of a prepolymer and a polyol component.

[0010] The prepolymer is the reaction product of an isocyanate component and an isocyanate-reactive component, and may be referred to as an isocyanate-based prepolymer or an iso-prepolymer.

[0011] The isocyanate component typically comprises a plurality of isocyanate (NCO) functional groups. In one example, the isocyanate component comprises at least two (2) NCO functional groups, and for this reason, the isocyanate component is said to have a functionality of at least 2. In another example, the isocyanate component may have from 2 to 8 NCO functional groups. In yet another example, the isocyanate component may have from 2 to 6 NCO functional groups. In still another example, the isocyanate component may have from 2 to 4 functional groups. In yet a another example, the isocyanate component has 2 functional groups, and thus has a functionality of 2.

[0012] The isocyanate component may be selected from a number of conventional aliphatic, cycloaliphatic, and aromatic isocyanates. In some examples, the isocyanate component is selected from diphenylmethane diisocyanates (MDIs), polymeric diphenylmethane diisocyanates (PMDIs), and combinations thereof. Polymeric diphenylmethane diisocyanates are also known as polymethylene polyphenylene polyisocyanates. In yet other examples, the isocyanate component is an emulsified MDI (eMDI) or a hydrogenated MDI (HMDI). Further examples of the isocyanate component include toluene diisocyanates (TDIs), hexamethylene diisocyanates (HDIs), isophorone diisocyanates (IPDIs), and combinations thereof.

[0013] In one example, the isocyanate component is selected from an isomer of methylene diphenyl diisocyanate (MDI). More specifically, the isocyanate component is selected from 2,2' -methylene diphenyl diisocyanate (2,2' -MDI), 2,4 '-methylene diphencyl diisocyanate (2,4'-MDI), and 4,4 '-methylene diphenyl diisocyanate (4,4'- MDI). In an example, the isocyanate component is 4,4'-MDI. In other examples, the isocyanate component may be selected from combinations of two or more of the isomers of MDI. For instance, the isocyanate component may include combinations of 4,4'-MDI and 2,4'-MDI, where 4,4'-MDI constitutes from about 50% to about 98% of the isocyanate component.

[0014] The isocyanate-reactive component may, for example, comprise a polyol and/or a polyamine having a plurality of functional groups (e.g. OH or NH functional groups) that are reactive with the NCO functional groups of the isocyanate component. In an example, the isocyanate-reactive component is a polyol and/or a polyamine having a functionality of at least 2. In another example, the isocyanate-reactive component is a polyol and/or a polyamine having a functionality of from 2 to 8. In still another example, the isocyanate-reactive component is a polyol and/or a polyamine having a functionality of from 2 to 6. In yet another example, the isocyanate-reactive component is a polyol and/or a polyamine having a functionality of from 2 to 4.

[0015] The isocyanate-reactive component may comprise any type of polyol. As a polyol, the isocyanate-reactive component may comprise a polyester polyol, a polyether polyol, a polyether/ester polyol, or combinations thereof. Furthermore, the isocyanate-reactive component may be selected from aliphatic polyols, cycloaliphatic polyols, aromatic polyols, hetercyclic polyols, and combinations thereof. Some examples of suitable isocyanate-reactive components include, but are not limited to, glycol-initiated polyols, glycerine-initiated polyols, sucrose-initiated polyols, sucrose/glycerine-initiated polyols, trimethylolpropane-initiated polyols, and combinations thereof.

[0016] Suitable polyether polyols include products obtained by the polymerization of a cyclic oxide, such as ethylene oxide (EO), propylene oxide (PO), butylene oxide (BO), and tetrahydrofuran in the presence of a polyfunctional initiator. Suitable initiator compounds contain a plurality of active hydrogen atoms, and include, but are not limited to, water, butanediol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, ethanolamine, diethanolamine, triethanolamine, toluene diamine, diethyl toluene diamine, phenyl diamine, diphenylmethane diamine, ethylene diamine, cyclohexane diamine, cyclohexane diemthanol, resorcinol, bisphenol A, glycerol, trimethylolpropane, 1,2,6-hexanetriol, pentaerythritol, and combinations thereof.

[0017] Other suitable polyether polyols include polyether diols and triols, such as polyoxypropylene diols and triols and poly(oxyethylene-oxypropylene)diols and triols obtained by simultaneous or sequential addition of ethylene and propylene oxides to di- or trifunctional initiators. Copolymers having oxyethylene contents of from about 5 to about 95% by weight, and copolymers having oxypropylene contents of from about 5 to about 100% by weight, based on the total weight of the polyol component, may also be used. These copolymers may be block copolymers, random/block copolymers, or random copolymers. Yet other suitable polyether polyols include polytetramethylene glycols obtained by the polymerization of tetrahydrofuran.

[0018] In an example, the isocyanate-reactive component is a polyether polyol that is capped. The term "capped", as used herein, means that one or more terminals of the polyether polyol is occupied by an alkylene oxide group, for example. In an example, the polyether polyol is capped with ethylene oxide. In other examples, the polyether polyol is capped with ethylene oxide, propylene oxide, butylene oxide, or combinations thereof.

[0019] In one example, the isocyanate-reactive component is a polyether polyol having a M_w of from about 3,000 to about 6,000. In yet another example, the isocyanate-reactive component is a polyether polyol having a M_w of from about 4,000 to about 6,000. In still another example, the isocyanate-reactive component is a polyether polyol having a M_w of from about 4,800 to about 5,000.

[0020] Suitable polyester polyols include hydroxyl-terminated reaction products of polyhydric alcohols, polyester polyols obtained by the polymerization of lactones, e.g. caprolactone, in conjunction with a polyol, and polyester polyols obtained by the polymerization of hydroxy carboxylic acids, e.g. hydroxy caproic acid. Polyesteramide polyols, polythioether polyols, polyester polyols, polycarbonate polyols, polyacetal polyols, and polyolefin polyols may also be used.

[0021] In certain examples, the isocyanate-reactive component of the system comprises a natural oil polyol (NOP), which is also known as a biopolyol. In other words, the polyol is not a petroleum-based polyol, i.e., a polyol derived from petroleum products and/or petroleum by-products. In general, there are a few naturally occurring vegetable oils that contain unreacted OH functional groups, and castor oil is typically commercially available and is produced directly from a plant source that has sufficient OH functional group content to make castor oil suitable for direct use as a polyol in urethane chemistry. Most, if not all, other NOPs require chemical modification of the oils directly available from plants. The NOP is typically derived from any natural oil, such as from a vegetable or nut oil. Examples of suitable natural oils include castor oil, and NOPs derived from soybean oil, rapeseed oil, coconut oil, peanut oil, canola oil, etc. Employing such natural oils can be useful for reducing environmental footprints.

[0022] In some examples, the isocyanate-reactive component comprises a graft polyol. In one example, the graft polyol is a polymer polyol. In other examples, the graft polyol is selected from the group of polyhamstoff (PHD) polyols, polyisocyanate poly addition (PIP A) polyols, and combinations thereof. Graft polyols may also be referred to as graft dispersion polyols or graft polymer polyols. In one example, the isocyanate-reactive component comprises a styrene-acrylonitrile graft polyol.

[0023] In still another example, the isocyanate-reactive component may be a polyamine including one or more amine (NH) functional groups. In this case, the isocyanate-reactive component typically includes at least two amine groups. The polyamine may be selected from any type of polyamine. Some examples of suitable polyamines include ethylene diamine, toluene diamine, diaminodiphenylmethane, polymethylene polyphenylene polyamines, aminoalcohols, and combinations thereof. Examples of aminoalcohols include ethanolamine, diethanolamine, triethanolamine, and combinations thereof.

[0024] It is to be appreciated that the isocyanate-reactive component may include any combination of the aforementioned polyols and/or polyamines.

[0025] As previously mentioned, the prepolymer comprises the reaction product of the isocyanate component and the isocyanate-reactive component. To form the prepolymer, the isocyanate component reacts with enough of the isocyanate-reactive component so that the prepolymer has from 2.5 to 3.6 % by weight of urethane (i.e., N- C=0) groups based on 100 % by weight of the entire prepolymer. In another example, to form the prepolymer, the isocyanate components react with enough of the isocyanate-reactive component so that the prepolymer has from 3.2 to 3.6 % by weight of urethane groups based on 100 % by weight of the entire prepolymer. Accordingly, the prepolymer comprises residual isocyanate groups that are available for a subsequent reaction(s) between the prepolymer and the polyol component to form the polyurethane coating disposed about the gas-filled spherical particles.

[0026] Without being bound to any theory, it is believed that a polyurethane gel may be formed from a reaction between the polyol component and the prepolymer having from 2.5 to 3.6 % by weight of urethane groups based on 100 % by weight of the prepolymer. It is further believed that a polyurethane gel cannot be formed when the amount of urethane groups in the prepolymer is less than 2.5 % by weight based on 100 % by weight of the prepolymer or when the amount of urethane groups in the prepolymer is greater than 3.6 % by weight based on 100 % by weight of the prepolymer. For instance, when the amount of urethane groups is less than 2.5 % by weight, all of the urethane groups will be consumed during the subsequent reaction between the prepolymer and the polyol component. While a polyurethane will form, a majority of the polyurethane (e.g. greater than 3.6% by weight of the polyurethane) will not have characteristics of a polyurethane gel. Further, a soft polyurethane coating will form (i.e., a polyurethane coating having a shore 00 hardness value that is greater than 50) when the amount of urethane groups is greater than 3.6 % by weight rather than a polyurethane gel.

[0027] In an example, the prepolymer is formed in the presence of a catalyst to accelerate the reaction between the isocyanate component and the isocyanate -reactive component. The catalyst may be selected, for example, from an organic base (such as a tertiary amine) or an organometallic compound.

[0028] The prepolymer may also be formed in the presence of one or more other additives, such as cross-linking agents, chain extenders (e.g. low molecular weight polyfunctional aliphatic or aromatic alcohols or amines), colorants, and fillers (e.g. organic and inorganic fillers). The additive(s) may be combined with the isocyanate component and/or the isocyanate-reactive component prior to reacting the isocyanate component and the isocyanate-reactive component. Alternatively, the additive(s) may be introduced, as a standalone component, after the isocyanate component and the isocyanate-reactive component have been combined.

[0029] Examples of the chain extender generally have a backbone chain with from 2 to 8 carbon atoms. In another example, the chain extender has a backbone with from 2 to 6 carbon atoms. The chain extender also has a weight- average molecular weight (M_w) of, for example, less than 1,000. In another example, the chain extender has a M_w of from 25 to 250, and more typically, a M_w that is less than 100. [0030] The chain extender may have two isocyanate-reactive groups. In an example, the chain extender is a diol having hydroxyl groups as the isocyanate-reactive groups. The chain extender may be selected from 1 ,4-butanediol, 1,3-butanediol, 2,3- butanediol, 1,2-butanediol, 1,3-propylene glycol, 1,5-pentanediol, ethylene glycol, diethylene glycol, and polyethylene glycols having a M_w of up to 200. Suitable examples of commercially available chain extenders are NIAX® DP- 1022 from Crompton OSi Specialties (Greenwich, CT) and ELASTOCAST® C1006 from BASF Corporation (Florham Park, NJ).

[0031] Examples of the cross-linking agent are amine-based cross-linking agents selected, for example, from diethanolamine, triethanolamine, trimethylolpropane, ethylene diamine alkoxylation products thereof having a hydroxyl number greater than 250, and combinations thereof. It is to be appreciated that other cross-linking agents may also be used. For instance, a polyol having a hydroxyl number of greater than 250 and a functionality of greater than 2 may be used as the cross-linking agent. One example of a suitable cross-linking agent is PLURACOL® 355, which is commercially available from BASF Corporation. In an example, the cross-linking agent is present in an amount of from about 0.3 to 5 % by weight based on 100 % by weight of the prepolymer.

[0032] In an example, the filler is a mineral filler, a metallic stearate, or combinations thereof. Some specific examples of fillers include silicates, carbonates, talc, clay, aluminum trihydroxide, fly ash, barium sulfate, zeolites, fumed silica, molecular sieves, glass fibers, glass spheres, carbon black, nanoparticles, conductive particles, or combinations thereof. More specific examples of suitable fillers include metallic stearates, carbonates, silicates, and combinations thereof. [0033] A cell opener may also be added, which has at least one of a paraffinic, cyclic, and aromatic hydrocarbon chain. The cell opener is, for example, mineral oil. It is to be understood, however, that other cell openers may be used, such as silicone oils, corn oil, palm oil, linseed oil, soybean oil, and defoamers based on particulates, such as silica. The polyurethane formed with the cell opener is noticeably less tacky than a polyurethane formed without the cell opener. Additionally, the polyurethane formed with the cell opener does not have an oily residue. One example of a suitable cell opener is a mineral oil that is commercially available from Mallinckrodt Chemicals.

[0034] In an example, the prepolymer is commercially available. As one example, the prepolymer is ELASTOCAST® TIP02, which is an isocyanate-based prepolymer that is commercially available from BASF Corporation. ELASTOCAST® TIP02 is a prepolymer comprising a modified MDI component capped with a polyether. The ELASTOCAST® TIP02 is also a clear liquid having 2.5 to 3.6 % by weight of urethane groups based on 100 % by weight of the prepolymer, and has a viscosity of about 30,000 to 60,000 mPa-s at 25°C.

[0035] Examples of the polyurethane coating disposed about the gas-filled spherical particles will now be described. The polyurethane coating disposed about the gas- filled spherical particles is generally the reaction product of the prepolymer and the polyol component.

[0036] The polyol component may be selected from any of the polyols identified above for the isocyante-reactive component. In an example, the polyol component is the same as the isocyanate-reactive component. For instance, both the polyol component and the isocyanate-reactive component may be selected from a polyether polyol capped with ethylene oxide. For instance, both the polyol component and the isocyanate-reactive component may be selected from an ethylene oxide capped triol initiated polyol. In another example, the polyol component may be different from the isocyanate-reactive component.

[0037] The polyurethane formed by the reaction between the prepolymer (which has residual isocyanate groups as previously mentioned) and the polyol component is a polyurethane gel. Further, it is to be understood that the polyurethane gel is coated on the gas-filled spherical particles as the polyurethane gel is formed. In other words, the polyurethane is formed and is coated on the gas-filled spherical particles at substantially the same time.

[0038] An example of a method of forming the polyurethane on the gas-filled spherical particles generally includes providing a plurality of the gas-filled spherical particles, forming the prepolymer by reacting the isocyanate component and the isocyanate-reactive component, and combining the prepolymer, the polyol component, and the gas-filled spherical particles such that the prepolymer and the polyol component react to form the polyurethane on the gas-filled spherical particles. In some instances, a mineral oil and a catalyst are also combined with the prepolymer, the polyol component, and the gas-filled spherical particles. Details of the formation of the polyurethane on the gas-filled spherical particles are set forth in a specific example that will now be described.

[0039] In the specific example mentioned immediately above, the polyurethane is formed and coated on the gas-filled spherical particles utilizing a batch process. In the example described below, the prepolymer is ELASTOCAST® TIP02 which is commercially available as mentioned above. In another example, the prepolymer is formed. Details of the formation of the prepolymer is set forth below. In an example, about 10 to about 11 lbs of the prepolymer is preheated (e.g. to a temperature of from about 100°F to about 130°F, more typically, to about 120°F) in a drum, and about 30 to about 33 lbs of the polyol component is preheated (e.g. to a temperature of from about 100°F to about 130°F, more typically, to about 120°F) in another drum. In this example, about 80 to about 85 lbs of cornstarch is slowly added to a mixing vessel, such as a Hockmeier mixing vessel, containing gas-filled spherical particles. The gas- filled spherical particles and the cornstarch are mixed (e.g. for about 30 minutes) utilizing an agitator and a disperser, both operated at a frequency of about 10 to about 20 Hz, and more typically at a frequency of about 15 Hz. The prepolymer and the polyol component are combined together in another mixing vessel, and the combination is blended at a frequency of about 10 to 20 Hz. This blending is performed for, e.g. about 5 to 10 minutes. The blend of the prepolymer and the polyol component is added to the mixing vessel containing the gas-filled spherical particles. The gas-filled spherical particles and the blend of the prepolymer and the polyol component is mixed inside the mixing vessel (e.g. utilizing the agitator and the disperser operated at a frequency of about 10 to 20 Hz for about, e.g., 25 to 30 minutes).

[0040] The prepolymer and the polyol component react when mixing occurs inside the mixing vessel to form the polyurethane. Additionally, it is believed that mixing facilitates the reaction between the prepolymer and the polyol component, and drives this reaction to completion. The reaction between the prepolymer and the polyol component is completed when the polyurethane coating is disposed about enough of the surfaces of the gas-filled spherical particles so that no active sites are present on the surfaces of the gas-filled spherical particles for further reaction/bonding. It is further believed that the polyurethane coating that is disposed about the gas-filled spherical particles has a thickness of from 0.5 to 3 mm. [0041] In some instances, one or more additives may be added to the mixing vessel when forming the polyurethane. For example, and as mentioned above, additives such as a mineral oil (e.g. DRAEKOL® 7 available from Calumet Specialty Products Partners, LP (Indianapolis, IN)) and a catalyst (e.g. a triethylene amine catalyst) may be added to the mixing vessel. Other additives may also be added, such as a cross- linking agent, a chain extender, and a filler. Examples of these additives are set forth above.

[0042] In the example described above, the cornstarch is added to the gas-filled spherical particles prior to combining the prepolymer, the polyol component, and the gas-filled spherical particles. For instance, the gas-filled spherical particles are mixed with cornstarch inside the mixing vessel prior to adding the blend of the prepolymer and the polyol component (and additive(s)) to the mixing vessel. Alternatively, the gas-filled spherical particles may be added to the cornstarch prior to combining the prepolymer, the polyol component, and the gas-filled spherical particles. Accordingly, the cornstarch and the gas-filled spherical particles may be combined prior to combining the prepolymer, the polyol component, and the gas-filled spherical particles. It is believed that the cornstarch prevents agglomeration of the gas-filled spherical particles inside the mixing vessel so that the polyurethane coating is suitably disposed about each of the gas-filled spherical particles. Said differently, it is believed that the cornstarch prevents the gas-filled spherical particles from clumping (e.g. sticking to one another) inside the mixing vessel so that the polyurethane coating is suitably disposed on each of the gas-filled spherical particles. In another example, cornstarch is not added to the gas-filled spherical particles, and in this example, the polyurethane is formed in the absence of cornstarch. [0043] In another example, a colorant (e.g. a dye) may also be added to the mixing vessel (e.g. prior or subsequent to adding the blend of the prepolymer and the polyol component to the mixing vessel). Typically, the colorant imparts a desirable color to the spheres (i.e., the gas-filled spherical particles with the polyurethane coating). For instance, a blue dye may be added so that the spheres visually depict a blue color. It is believed that the blue color will provide a visual reference to the cooling effect of the spheres on the viscoelastic foam.

[0044] In another example, the prepolymer utilized for the batch process described above may be formed rather than purchased. In an example, the prepolymer is formed by reacting 4,4-MDI and a polyether triol in a heated reactor in the presence of a stabilizer (such as benzoyl chloride).

[0045] After the polyurethane coating is disposed about all of the gas-filled spherical particles, the spheres (i.e., the gas-filled particles with the polyurethane coating) are removed from the mixing vessel. It is to be understood that there may be some residual components (such as residual cornstarch and uncoated gas-filled spherical particles) after the polyurethane coating is formed. These residual components are not separated from the polyurethane coating, and are instead dispersed in the viscoelastic foam. It is believed that the residual components do not affect the cooling effect imparted on the viscoelastic foam.

[0046] As previously mentioned, the polyurethane coating disposed about the gas- filled spherical particles may be a polyurethane gel. In the form of a gel, the polyurethane coating is considered to be relatively flexible, and has a shore OO hardness value of from about 20 to about 50 measured according to ASTM D2240 type OO hardness scale. In another example, the polyurethane coating has a shore OO hardness value of from about 35 to about 50 measured according to ASTM D2240 type 00 hardness scale. The ASTM D2240 is a standard test method for rubber property - durometer hardness, and the test is based on the penetration of an indentor when forced into a material (e.g. the polyurethane) under specified conditions. The indentation hardness is inversely related to the penetration, and the indentation hardness is dependent on the elastic modulus and viscoelastic behavior of the material. The test method may be used for several types of rubber hardness, including hardness type 00.

[0047] A method of forming a viscoelastic foam system is disclosed herein. This method comprises forming the spheres and dispersing the spheres in the viscoelastic foam. The gas-filled spherical particles with the polyurethane coating (i.e., the spheres) are formed as previously described. The spheres are dispersed in the viscoelastic foam, such as a viscoelastic polyurethane foam, to form the viscoelastic foam system. Examples of dispersing the spheres in the viscoelastic foam are set forth below.

[0048] The viscoelastic polyurethane foam may, for instance, be a single layer flexible foam, such as a traditional single layer flexible foam, a high resilience single layer flexible foam, a closed cell single layer flexible foam, an open cell single layer flexible foam, a molded single layer flexible foam, a slabstock single layer flexible foam, and/or combinations thereof. Similarly, the single layer flexible foam may be further defined as a polyurethane single layer flexible foam, a polyurea single layer flexible foam, a polymer single layer flexible foam, a single layer flexible foam rubber, and the like. In an example, the single layer flexible foam is a polyurethane single layer flexible foam. Various non-limiting generic examples of single layer flexible foams include PLURACEL^® VE and PLURACEL^® HR, both of which are commercially available from BASF Corporation (Florham Park, NJ). [0049] As used herein, the term "flexible" foam typically excludes rigid foams. Furthermore, flexible foams useful for the viscoelastic foam of the present disclosure may have particular physical properties and/or distinguishing characteristics measured according to ASTM, ISO, and/or BIFMA standards (or any other standards recognized in the art). Non- limiting examples of various physical properties that may be measured and/or distinguishing include density, support factor (compression modulus), air flow, ball rebound, compression modulus, compression set, durability, dynamic fatigue, flex fatigue, hysteresis, indentation force deflection (IFD), recovery, resilience, static fatigue, surface firmness, tear strength, tensile strength, and/or total vertical motion (TVM).

[0050] The viscoelastic foam, as a viscoelastic polyurethane foam, generally comprises the reaction product of an isocyanate material and an isocyanate-reactive material. The isocyanate material for the viscoelastic foam may, for example, be selected from any of the isocyanate components mentioned above. In another example, the isocyanate material may be an isocyanate-terminated prepolymer, which is the reaction product of an isocyanate and a polyol and/or a polyamine. The isocyanate material may, in still another example, be any combination of an isocyanate and/or isocyanate-terminated prepolymer. Furthermore, the isocyanate material may have any amount ( ) of urethane groups, and may have any viscosity.

[0051] In an example, the isocyanate-reactive material may be selected from any of the isocyanate-reactive components identified above for forming the prepolymer.

[0052] In an example, the viscoelastic foam further includes one or more additives. Such additives include, but are not limited to, cross-linking agent, chain extenders, catalysts, fillers, and colorants. Specific examples of these additives are provided above. Additional additives that may be included in the viscoelastic foam include surfactants, flame retardants, plasticizers, stabilizers, air releasing agents, wetting agents, surface modifiers, waxes, foam stabilizing agents, moisture scavengers, desiccants, viscosity reducers, cell-size reducing compounds, cell openers, reinforcing agents, mold release agents, anti-oxidants, compatibility agents, ultraviolet light stabilizers, thixotropic agents, anti-aging agents, lubricants, coupling agents, solvents, rheology promoters, adhesion promoters, thickeners, smoke suppressants, anti-static agents, anti-microbial agents, and combinations thereof.

[0053] In an example, the viscoelastic foam may also include a monol to increase the tan delta peak of the viscoelastic foam. In an example, the monol also softens the viscoelastic foam and slows down recovery.

[0054] The viscoelastic foam may also include a cell opener having at least one of a paraffinic, cyclic, and aromatic hydrocarbon chain. Examples of the cell opener are set forth above. Viscoelastic foams formed with the cell opener are noticeably less tacky than those formed without the cell opener. Additionally, viscoelastic foams formed with the cell opener do not have an oily residue. Furthermore, foams containing less than 2.5 parts by weight of the cell opener based on 100 parts by weight of the viscoelastic foam have fewer tendencies to retain fingerprints after handling. However, modifying the other components of the viscoelastic foam may also affect fingerprinting. Further, the cell opener increases air flow through the foam and decreases recovery time of the viscoelastic foam.

[0055] Furthermore, the viscoelastic foam may comprise a blowing agent, such as a chemical blowing agent, a physical blowing agent, or combinations thereof. The chemical blowing agent is designed to react with the isocyanate component to form carbon dioxide. The physical blowing agent is designed not to react with the isocyanate component. Examples of physical blowing agents include a hydrofluorocarbon (HFC), such as HFC-134a, HFC-152a, HFC-245fa, HFC-365mfc, HFC-22, and combinations thereof.

[0056] As previously mentioned, the viscoelastic foam is the reaction product of the isocyanate material and the isocyanate-reactive material. In an example, the isocyanate material is at A side of the reaction and the isocyanate-reactive material is at the B side of the reaction. In an example, the A side of the reaction constitutes about 25 % by weight based on 100 % by weight of the viscoelastic foam while the B side of the reaction constitutes about 75 % by weight based on 100 % by weight of the viscoelastic foam. Furthermore, a viscoelastic foam system includes the viscoelastic foam and the spheres dispersed in the viscoelastic foam. As an example, the spheres are added at the B side of the reaction prior to reacting the isocyanate material with the isocyanate-reactive material. For instance, from about 4 to 10 % by weight of spheres based on 100 % by weight of the B side of the reaction are added to the B side of the reaction. The spheres may be added to the isocyanate-reactive material (e.g. in a first drum), while the isocyanate material is contained separately (e.g. in a second drum). The contents of the first and second drum are combined, and the isocyanate material reacts with the isocyanate-reactive material to form the viscoelastic foam.

[0057] It is to be understood that the spheres will disperse throughout the matrix of the viscoelastic foam as the viscoelastic foam is formed (i.e., during the reaction of the isocyanate material and the isocyanate-reactive material). The spheres may be randomly or uniformly dispersed in the viscoelastic foam. In one example, the spheres will randomly disperse throughout the matrix of the viscoelastic foam as the viscoelastic foam is formed. The term "randomly dispersed", as used herein, means that the spheres are free from any pattern of orientation, alignment, positioning, and/or distance between adjacent spheres in the viscoelastic foam. In an example, the spheres are present in the viscoelastic foam system in an amount of from 3 to 7.5 % by weight based on 100% by weight of the viscoelastic foam system.

[0058] It is further to be understood that the polyurethane coating disposed about the gas-filled spherical particles does not chemically bond to the viscoelastic foam when the spheres are incorporated into the viscoelastic foam. For instance, the polyurethane coating disposed about the gas-filled spherical particles does not form covalent bonds with the viscoelastic foam. It is believed that, at most, some hydrogen bonding may occur between the polyurethane coating disposed about the gas-filled spherical particles and the viscoelastic foam.

[0059] The examples of the formation of the viscoelastic foam system have been described above as adding the spheres at the B side of the reaction prior to actually reacting the isocyanate material with the isocyanate-reactive material (which comprises the spheres). It is also contemplated herein that the spheres may otherwise be added alone; e.g. the spheres may be contained in a third drum and then the contents from the first, second, and third drums may be added together to form the viscoelastic foam. It is further contemplated that the spheres may be added from multiple sources; e.g. some spheres may be added at the B side while other spheres may be added from a separate drum. Furthermore, spheres may be added as soon as the isocyanate material and the isocyanate-reactive material begin to react, as well as after the reaction between the isocyanate material and the isocyanate-reactive material has been initiated.

[0060] Additionally, the spheres may be formed and, immediately afterwards, are incorporated into a viscoelastic foam utilizing the example methods described above. Alternatively, the spheres may be formed and then stored, shipped, or otherwise incorporated into a viscoelastic foam at a later time, again utilizing the example methods described above. [0061] As used herein, the term "about" is understood by persons of ordinary skill in the art and varies to some extent depending upon the context in which the term is used. If there are uses of the term which are not clear to persons of ordinary skill in the art, given the context in which the term is used, "about" means up to plus or minus 10% of the particular term.

[0062] It is to be understood that one or more of the values described above may vary by ± 5%, ± 10%, ± 15%, ± 20%, ± 25%, ± 30%, etc. so long as the variance remains within the scope of the invention. It is also to be understood that the appended claims are not limited to express and particular compounds, compositions, or methods described in the detailed description, which may vary between particular embodiments which fall within the scope of the appended claims. With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, it is to be appreciated that different, special, and/or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members. Each member of a Markush group may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims.

[0063] It is also to be understood that any ranges and subranges relied upon in describing various embodiments of the present invention independently and collectively fall within the scope of the appended claims, and are understood to describe and contemplate all ranges including whole and/or fractional values therein, even if such values are not expressly written herein. One of skill in the art readily recognizes that the enumerated ranges and subranges sufficiently describe and enable various embodiments of the present invention, and such ranges and subranges may be further delineated into relevant halves, thirds, quarters, fifths, and so on. As just one example, a range "of from 0.1 to 0.9" may be further delineated into a lower third, i.e., from 0.1 to 0.3, a middle third, i.e., from 0.4 to 0.6, and an upper third, i.e., from 0.7 to 0.9, which individually and collectively are within the scope of the appended claims, and may be relied upon individually and/or collectively and provide adequate support for specific embodiments within the scope of the appended claims. In addition, with respect to the language which defines or modifies a range, such as "at least," "greater than," "less than," "no more than," and the like, it is to be understood that such language includes subranges and/or an upper or lower limit. As another example, a range of "at least 10" inherently includes a subrange of from at least 10 to 35, a subrange of from at least 10 to 25, a subrange of from 25 to 35, and so on, and each subrange may be relied upon individually and/or collectively and provides adequate support for specific embodiments within the scope of the appended claims. Finally, an individual number within a disclosed range may be relied upon and provides adequate support for specific embodiments within the scope of the appended claims. For example, a range "of from 2 to 8" includes various individual integers, such as 3, as well as individual numbers including a decimal point (or fraction), such as 4.1, which may be relied upon and provide adequate support for specific embodiments within the scope of the appended claims.

[0064] The subject matter of all combinations of independent and dependent claims, both singly and multiply dependent, is herein expressly contemplated but is not described in detail for the sake of brevity. The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings, and the invention may be practiced otherwise than as specifically described.

Claims

CLAIMS What is claimed is:

1. A viscoelastic foam system comprising: a viscoelastic foam; and spheres dispersed in the viscoelastic foam, each sphere comprising: a gas-filled spherical particle; and a polyurethane coating disposed about the gas-filled spherical particle, the polyurethane coating comprising the reaction product of: i) a prepolymer comprising the reaction product of an isocyanate component and an isocyanate-reactive component, the prepolymer comprising from 2.5 to 3.6 % by weight of urethane groups based on 100 % by weight of the prepolymer; and ii) a polyol component; wherein the polyurethane coated on the gas-filled spherical particle has a shore 00 hardness value of from about 20 to about 50 measured according to ASTM D2240 type OO hardness scale.

2. The viscoelastic foam system as set forth in claim 1, wherein the isocyanate- reactive component is a polyether polyol.

3. The viscoelastic foam system as set forth in claim 2, wherein the polyether polyol is capped with ethylene oxide.

4. The viscoelastic foam system as set forth in claim 2, wherein the polyether polyol has a weight average molecular weight ranging from 3,000 to 6,000.

5. The viscoelastic foam system as set forth in any one of the previous claims, wherein the isocyanate component has a functionality of at least 2.

6. The viscoelastic foam system as set forth in any one of the previous claims, wherein the isocyanate component is selected from the group consisting of 2,2'- methylene diphenyl diisocyanate, 2,4' -methylene diphencyl diisocyanate, 4,4'- methylene diphenyl diisocyanate, and combinations thereof.

7. The viscoelastic foam system as set forth in any one of the previous claims, wherein the polyol component is a polyether polyol.

8. The viscoelastic foam system as set forth in any one of the previous claims, wherein the isocyanate-reactive component is the same as the polyol component.

9. The viscoelastic foam system as set forth in any one of the previous claims, wherein the gas-filled spherical particle has an expandable thermoplastic shell encapsulating a gas.

10. The viscoelastic foam system as set forth in claim 9, wherein the gas-filled spherical particle has an effective particle size ranging from 30.0 μιη to 50.0 μιη.

11. A sphere for a viscoelastic foam, the sphere comprising: a gas-filled spherical particle; and a polyurethane coating disposed about the gas-filled spherical particle, the polyurethane coating comprising the reaction product of: i) a prepolymer comprising the reaction product of an isocyanate component and an isocyanate-reactive component, the prepolymer comprising from 2.5 to 3.6 % by weight of urethane groups based on 100 % by weight of the prepolymer; and ii) a polyol component; wherein the polyurethane coating disposed about the gas-filled spherical particle has a shore 00 hardness value of from 20 to about 50 measured according to ASTM D2240 type OO hardness scale.

12. The sphere as set forth in claim 11, wherein the isocyanate-reactive component is a polyether polyol capped with ethylene oxide.

13. The sphere as set forth in claim 11, wherein the isocyanate-reactive component is a polyether polyol having a weight average molecular weight ranging from 3,000 to 6,000.

14. The sphere as set forth in any one of claims 11 to 13, wherein the isocyanate component is selected from the group consisting of 2,2 '-methylene diphenyl diisocyanate, 2,4' -methylene diphencyl diisocyanate, 4,4'-methylene diphenyl diisocyanate, and combinations thereof.

15. The sphere as set forth in any one of claims 11 to 14, wherein the gas-filled spherical particle comprises an expandable thermoplastic shell encapsulating a gas.

16. The sphere as set forth in claim 15, wherein the gas-filled spherical particle has an effective particle size ranging from 30.0 μιη to 50.0 μιη.

17. A method of forming a viscoelastic foam system, the method comprising the steps of:

A. forming the spheres by: providing a plurality of gas-filled spherical particles; and coating the plurality of gas-filled spherical particles with a polyurethane; wherein the polyurethane has a shore OO hardness value of from about 20 to about 50 measured according to ASTM D2240 type OO hardness scale; and

B. dispersing the spheres in a viscoelastic foam to form the viscoelastic foam system.

18. The method as set forth in claim 17, wherein the coating step is further defined by: forming a prepolymer by reacting an isocyanate component and an isocyanate- reactive component, wherein the prepolymer comprises from 2.5 to 3.6 % by weight of urethane groups based on 100 % by weight of the prepolymer; and reacting the prepolymer and the polycol component to form the polyurethane as a coating on the plurality of gas-filled spherical particles.

19. The method as set forth in claim 18 further comprising combining the prepolymer, the polyol component, and the plurality of gas-filled spherical particles during the reacting step so that the prepolymer and the polycol component react to form the polyurethane.

20. The method as set forth in any one of claims 17 to 19, wherein the viscoelastic foam comprises the reaction product of an isocyanate material and an isocyanate -reactive material, and wherein the step of dispersing the spheres in the viscoelastic foam is further defined as: combining the spheres and the isocyanate-reactive material; and reacting the isocyanate material with the isocyanate-reactive material comprising the spheres; wherein the spheres disperse in the viscoelastic foam during the reacting step.