Flexible polyurethane foam having prolonged recovery time

Abstract

Recovery times and/or airflow of flexible polyurethane foam is increased by including certain tackifiers in the foam formulation. The tackifiers are formed into an emulsion that includes a polyether containing oxyethylene groups, a nonionic surfactant and certain fumed silica, carbon black or talc particles.

Claims

1. A formulated polyol composition comprising: i) at least one tackifier; ii) at least one polyether polyol having an oxyethylene content of at least 50% by weight; iii) at least one nonionic surfactant having a hydrophilic-lipophilic balance of 12 to 19; iv) at at least one hydrophobically-modified fumed silica, carbon black, talc, or a mixture of any two or more thereof; v) 0.25 to 5 weight percent water, based on the total weight of the formulated polyol composition; vi) at least one urethane catalyst; and vii) at least one foam-stabilizing surfactant, wherein the formulated polyol composition contains 5 to 25 weight percent of component i) and 0.1 to 2.5 weight percent of component iv), based on the total weight of the formulated polyol composition, and the weight ratio of component ii) to component i) is 0.5 to 10.

2. A method of making a flexible polyurethane foam, comprising I) forming a reaction mixture, at an isocyanate index of 60 to 125, the reaction mixture comprising: i) at least one organic polyisocyanate; ii) at least one tackifier; iii) at least one polyether polyol having an oxyethylene content of at least 50% by weight; iv) at least one nonionic surfactant having a hydrophilic-lipophilic balance of 12 to 19; v) at least one hydrophobically-modified fumed silica, carbon black, talc, or a mixture of any two or more thereof; vi) 0.25 to 5 weight percent water, based on the total weight of all components of the reaction mixture except the at least one organic polyisocyanate; vii) at least one urethane catalyst; and vii) viii) at least one foam-stabilizing surfactant, wherein the reaction mixture contains 5 to 25 weight percent of component ii) and 0.1 to 2.5 weight percent of component v) based on the total weight of all components except the at least one organic polyisocyanate(s), and the weight ratio of component iii) to component ii) is 0.5 to 10; and II) reacting the reaction mixture to form the flexible polyurethane foam.

3. The method of claim 2 wherein the at least one tackifier is one or more of a rosin, a hydrogenated and/or esterified rosin, a polyterpene, a C5 aliphatic resin, a C9 aromatic resin, a C5/C9 copolymer resin, a hydrogenated C5 or C9 resin, a polybutene, an epoxy resin, a styrene/butadiene copolymer, an ethylene-acrylic acid copolymer, an ethylene-propylene copolymer having a density of less than 0.900 g/cc, a silicone oil, xanthan gum, ethyl cellulose, hydroxylpropyl methyl cellulose, carboxylmethyl cellulose, cationic polyacrylamide, para-t-octyl phenol formaldehyde resin, a polyester having a molecular weight of 800 to 2000, a urethane acrylate oligomer, or a room temperature liquid ethylene-propylene-diene resin.

4. The method of claim 2 wherein the at least one nonionic surfactant is one or more of a block copolymer of ethylene oxide and a higher alkylene oxide, or an ethoxylated hydrocarbon in which the hydrocarbon portion includes a linear, branched, aliphatic, cycloaliphatic and/or aromatic group having at least 6 carbon atoms.

5. The method of claim 2 wherein component v) is at least one fumed silica which has been hydrophobically modified by reaction at its surface with one or more hydrocarbon, halogen-substituted hydrocarbon, siloxane and/or silane groups.

6. The method of claim 2 wherein component v) has a surface area of at least 90 m.sup.2/g as measured by nitrogen absorption methods.

7. A flexible polyurethane foam made by the process of claim 2.

8. The flexible polyurethane foam of claim 7 wherein the at least one tackifier occupies 2.5 to 40% of the surface area of internal surfaces of the polyurethane foam.

9. The flexible polyurethane foam of claim 7 wherein the at least one tackifier is present on internal surfaces of the polyurethane foam in the form of discontinuous regions having longest dimensions of 10 nm to 200 μm.

Description

EXAMPLES 1-4 AND COMPARATIVE SAMPLE A

(1) A. Preparation of Emulsions

(2) Emulsion Example E-1 through E-4 are prepared by mixing the ingredients indicated in Table 1 in a high speed laboratory mixer. All ingredients are initially at room temperature except the Tackifier, which is preheated to 50° C. prior to being combined with the other ingredients.

(3) TABLE-US-00001 TABLE 1 Parts by Weight Ingredient E-1 E-2 E-3 E-4 Polyol A 20 50 20 50 Tackifier 10 10 10 10 Nonionic Surfactant 1 1 1 1 Fumed Silica A 0.5 0.5 0 0 Fumed Silica B 0 0 0.5 0.5

(4) In each case, a stable emulsion of the tackifier in Polyol A is obtained. By contrast, when otherwise like emulsions are prepared, substituting Polyol B for Polyol A, a gelled material unsuitable for processing through a polyurethane foam equipment is obtained.

(5) Flexible polyurethane foam Examples 1-4 are made with Emulsions E-1 through E-4, respectively. The foam formulations are as indicated in Table 2 below. In each case the foams are made in each case by mixing all components except the Catalyst and TDI-80 in a high-speed mixer at room temperature for 15 seconds at 2400 rpm. The Catalyst is added and mixed in for 15 seconds at 2400 rpm. The TDI-80 is then mixed in for 3 seconds at 3000 rpm, and the reaction mixture is immediately poured into a 38 cm×38 cm×24 cm box lined with a plastic release film. The foam is permitted to rise and set in the box and is then cured overnight at room temperature. The external surfaces of the foam are removed to expose open cells on all external surfaces.

(6) Comparative Foam A is made in the same way from the ingredients indicated in Table 2. Comparative Foam A contains no tackifier.

(7) TABLE-US-00002 TABLE 2 Parts by Weight Ingredient Comp. A* 1 2 3 4 Polyol A 75 45 0 45 0 Polyol B 25 25 25 25 25 Emulsion E-1 0 47.25 0 0 0 Emulsion E-2 0 0 92.25 0 0 Emulsion E-3 0 0 0 47.25 0 Emulsion E-4 0 0 0 0 92.25 Water 3.8 3.8 3.8 3.8 3.8 Foam Surfactant 2 2 2 2 2 Catalyst 0.55 0.50 0.50 0.50 0.50 TDI-80 (100.5 43.38 43.45 43.45 43.45 43.45 index) Total Tackifier 0 15 15 15 15 Content Total Polyol A 75 75 75 75 75 Content *Not an example of this invention.

(8) In each of Examples 1-4, the Emulsion blends easily with the other components to form a macroscopically uniform mixture. The foams in each case rise and cure rapidly. These characteristics indicate that these examples are readily scaled to continuous, large-scale production.

(9) Foam Density, indentation force deflection (IFD), compression set, tensile strength, tear strength, elongation, airflow and resiliency are measured for each foam according to ASTM D3574. Recovery time is measured in each case in the manner described above. Results are as indicated in Table 3.

(10) TABLE-US-00003 TABLE 3 Result Property Comp. A* Ex. 1 Ex. 2 Ex. 3 Ex. 4 Density, 1.71 (27.4) 1.94 (31.1) 1.96 (31.4) 1.95 (31.2) 1.96 (31.4) pcf (kg/m.sup.3) Resilience, % 39  28 28 29 28 Recovery time, 0   2.8   4.6   2.9   2.8 sec. Airflow, scfm 4.2 (2.0) 6.4 (3.0) 4.6 (2.2)  5.4 (2.55) 4.5 (2.1) (L/s) Tensile Strength,  8.7 (60.0) 10.4 (71.7)  8.2 (56.5) 10.9 (75.2) 10.2 (70.3) psi (kPa) Tear Strength, 2.33 (0.41) 2.44 (0.43) 2.59 (0.45) 2.47 (0.43) 2.47 (0.43) pli (N/mm) Elongation to 163  257  100  262  233  break, % IFD, lb-force (N) 25% Compression  29 (129)  9 (40) 11 (49) 10 (44) 12 (53) 65% Compression  54 (289) 20 (89) 22 (98) 21 (93)  24 (107) 90% Compression 3  7  8  5  5 Set, % *Not an example of this invention.

(11) As can be seen from the data in Table 3, good foams are made with the invention. The foam properties obtained are representative of good quality cushioning foams. Comp. Sample A has poor viscoelastic properties. Resilience is almost 40% and recovery time is zero. Those attributes are indicative of a resilient foam that springs back immediately after a compressive force is removed. By contrast, each of Examples 1-4 has a resiliency of below 30 and recovery times that range from almost 3 seconds to almost 5 seconds.

(12) Scanning electron micrographs are obtained on samples taken from each of Examples 1 and 2. The micrographs appear as FIGS. 1 and 2, respectively.

(13) Turning to FIG. 1, strut 1 is single strut of a polyurethane-urea foam. Islands 2 are islands tackifier that together occupy a portion of the exterior surface of strut 1. Tackifier islands 2 range in size from a few micrometers to 20-30 micrometers and occupy 5 to 10% of the surface area of strut 1. Tackifier islands 2 are richer in carbon than strut 1, and relatively deficient in both carbon and nitrogen (which is not detectable at all in islands 2 and 2A), upon examination using energy-dispersive X-ray spectroscopy (EDS). These EDS results permit polyurethane or polyurethane-urea to be assigned as the material of construction of strut 1 and tackifier to be assigned as the component of islands 2. The relatively low level of oxygen in islands 2 is consistent with the low oxygen content of the tackifier relative to the raw materials that react to form the polyurethane. In addition, the lack of nitrogen in islands 2 confirms that urethane and urea linkages are absent, which eliminates islands 2 from being polyurethane.

(14) The reference numerals in FIG. 2 indicate the same features as the corresponding numerals in FIG. 1. In the embodiment depicted in FIG. 2, tackifer islands 2 have sizes of about 5 to 30 μm and occupy 15-40% of the surface area of strut 1. As is the case for FIG. 1, islands 2 are identified as tackifier due to the low level of oxygen and absence of nitrogen as determined by EDS.

EXAMPLES 5-10 AND COMPARATIVE SAMPLES B and C

(15) Emulsion Examples 5-10 and Comparative Samples B and C are made by combining 10 parts of a polyterpene resin (Piccolyte® A25 from Pinova Solutions, softening temperature 22-28° C., Brookfield viscosity 3500-5500 cps at 50° C.), 1 part of nonionic surfactant (when used) and 0.5 part of an inorganic particulate (when used) as indicated in Table 4 below. These components are heated to about 50° C. to soften the polyterpene resin, hand-mixed until visually homogeneous and reheated to 50° C. 30 parts of Polyol A are added, and the mixture in each case is transferred to a laboratory benchtop mixer and stirred at high speed to form an emulsion.

(16) The nonionic surfactant is an ethylene oxide/propylene oxide block copolymer with an HLB of approximately 18 as described before. As in indicated in Table 4, the nonionic surfactant is provided neat (as a room temperature solid) in some cases and as a liquid solution of 70% surfactant and 30% water in others. In the latter case, the amount of surfactant is about 0.7 parts and the amount of water is 0.3 parts.

(17) The inorganic particulate is Fumed Silica A as indicated above, Emperor™ 1600 carbon black from Cabot Corporation, or Talcron MP 10-52 talc from The Cary Company, as indicated in Table 4.

(18) The emulsions so produced are maintained at room temperature and observed periodically to evaluate their stability. The time until the emulsion has fully separated to form a two-phase system is indicated in Table 4 as a measure of emulsion stability (with greater times indicating better stability). After phase separation has taken place, re-emulsification is attempted by again stirring the mixture at high speed on the laboratory benchtop mixer. Results of the re-emulsification attempts are as indicated in Table 4.

(19) TABLE-US-00004 TABLE 4 Inorganic Particles/ Days to Phase Able to Be Re- Sample Nonionic Surfactant Separation Emulsified? B* Fumed silica/no surfactant <5 No C* No particles/neat surfactant <5 No 5 Fumed silica/neat surfactant 14 Yes 6 Fumed silica/aqueous >21 Yes surfactant solution 7 Carbon black/neat 10 Yes surfactant solution 8 Carbon black/aqueous 14 Yes surfactant solution 9 Talc/neat surfactant 14 Yes 10 Talc/aqueous surfactant >21 Yes solution *Not an example of the invention.

(20) Comparative Samples B and C demonstrate the need to have both the inorganic particles and nonionic surfactant present in order to obtain adequate emulsion stability. In each case the emulsion phase separates after a short period and cannot be re-emulsified.

(21) Each of Examples 5-10 demonstrates improved emulsion stability (and ability to re-emulsify) when both surfactant and inorganic particles are present. Emulsion stability is at least doubled in each case. The presence of water in Examples 6, 8 and 10 provides still further increases in emulsion stability, as seen by comparing those Examples with Examples 5, 7 and 9, respectively.