Method of making dispersions

Abstract

Dispersions of silicate particles are formed in a polyol phase. The polyol, an alkoxysilane, water and catalyst are combined and reacted under specific temperature conditions to form the silicate particles in-situ in a liquid polyol phase. The dispersions are characterized in having excellent stability.

Claims

1. A process for making a dispersion of silicate particles in a polyol phase comprising the steps of a) forming a mixture by combining i) 0.5 to 50 parts by weight of at least one alkoxysilane in which the alkoxy groups each independently contain 1 to 4 carbon atoms, ii) 100 parts by weight of one or more polyols each having a hydroxyl equivalent weight of 125 to 5000, the one or more polyols having an average at least 1.8 hydroxyl groups per molecule, iii) at least one mole of water per mole of the at least one alkoxysilane and iv) a catalyst for the reaction of the alkoxysilane and water and then; b) at a temperature of 10 to 70° C. and under agitation, reacting the at least one alkoxysilane and water in the presence of the one or more polyols to form a dispersion of silicate particles in a continuous phase of the one or more polyols; and then c) stripping the dispersion to remove residual water and other volatiles.

2. The process of claim 1 wherein the alkoxysilane is tetraethoxysilane.

3. The process of claim 1 wherein the catalyst is an aqueous ammonia solution.

4. The process of claim 1 wherein the mixture formed in step a) contains, in addition to components i), ii), iii) and iv), at most 2 parts by weight, per 100 parts by weight of component ii), of volatile organic compounds.

5. The process of claim 1 wherein the mixture formed in step a) contains, in addition to components i), ii), iii) and iv), at most 2 parts by weight, per 100 parts by weight of component ii), of isocyanate-reactive compounds.

6. The process of claim 1 wherein the mixture formed in step a) contains, in addition to components i), ii), iii) and iv), at most 2 parts by weight, per 100 parts by weight of component ii), of alcohols having a hydroxyl equivalent weight of less than 150.

7. The process of claim 1 wherein the temperature in step b) is 40 to 65° C.

8. The process of claim 1 wherein in step c), the dispersion is stripped until the water content is at most 0.1 by weight of the dispersion.

9. The process of claim 8 wherein in step c), the dispersion is stripped until the volatiles content include water and other volatiles is at most 0.1 by weight of the dispersion.

Description

COMPARATIVE SAMPLES A-C

(1) Comparative Samples A-C are made using the following starting materials: 12 parts TEOS, 8 parts ammonia water, 48 parts ethanol, 3 parts water and 28 parts of a polyether polyol (Polyol A) made by propoxylating and then ethoxylating glycerin to produce a 1550 hydroxyl equivalent weight, nominally trifunctional block copolymer containing 20% by weight polymerized ethylene oxide and mainly primary hydroxyl groups.

(2) Comparative Sample A is made by mixing the ingredients at room temperature and heating to 50° C. under agitation in a reaction vessel equipped with a condenser and mechanical stirrer. Volatiles are not stripped from the resulting dispersion because the ethanol is needed to provide enough of a liquid phase to keep the silicate particles suspended.

(3) Comparative Sample B is made in the same manner as Comparative Sample A, without stripping volatiles from the product, by adding the polyether polyol only after the remaining ingredients have been mixed and heated together to 50° C.

(4) Comparative Sample C is made in the same manner as Comparative Sample A, without stripping volatiles from the product, by adding the ammonia water only after the remaining ingredients have been mixed and heated together to 50° C.

(5) In each case, a dispersion of silicate particles forms. The dispersions are permitted to stand at room temperature in a closed container for several weeks. They are observed periodically to determine whether the particles remain suspended in the liquid phase. By this measure, Comparative Samples A and B are stable for about two weeks. Comparative Sample C is stable for less than a day.

COMPARATIVE SAMPLES D AND E

(6) Comparative Samples D and E are made using the following starting materials: 14 parts TEOS, 10 parts ammonia water, 56 parts ethanol, 3 parts water and 16 parts of Polyol A.

(7) Comparative Sample D is made in the same manner as Comparative Sample A, without stripping volatiles from the product. One-half of Polyol A charged to the reactor, followed by a pre-mix of the TEOS, water, the remaining amount of Polyol A and three-fourths of the ethanol. This mixture is heated to 50° C. and the ammonia water and remaining ethanol are added. Comparative Sample D is stable for about 2 weeks.

(8) Comparative Sample E is made in the same manner as Comparative Sample A, without stripping volatiles from the product, by adding the ammonia water only after the remaining ingredients had been mixed and heated together to 50° C. Comparative Sample E is stable for about 2 weeks.

(9) None of Comparative Samples A-E is suitable for making an isocyanate-based polymer due to the large concentration of ethanol, which reacts monofunctionally with polyisocyanates.

EXAMPLES 1-3 AND COMPARATIVE SAMPLE F

(10) Examples 1-3 are made using the following starting materials: 15 parts TEOS, 11 parts ammonia water, 4 parts water and 70 parts of Polyol A.

(11) Example 1 is made in the same manner as Comparative Sample A, by adding the ammonia water only after the remaining ingredients had been mixed and heated together to 50° C. Volatiles are stripped from the product after the reaction is complete. Example 1 is stable for about 6 weeks.

(12) Example 2 is made in the same manner as Comparative Sample A (with stripping volatiles from the product), by adding the TEOS only after the remaining ingredients had been mixed and heated together to 50° C. Example 2 is stable for at least 6 weeks.

(13) The product is centrifuged to isolate silicate particles for measurement of particle size by scanning electron microscopy (SEM) analysis. The recovered particles are dried and sputtered with chromium using a high-resolution sputter-coater to produce a 5 nm coating. Imaging is performed using a scanning electron microscope operating at an accelerating voltage of 20 kV using both a second electron detector and a backscattered electron detector. Particle sizes are 200 to 500 nm, as determined by visual inspection of the produced images.

(14) Example 3 is made in the same manner as Comparative Sample A (with stripping volatiles from the product), by adding the ammonia water only after the remaining ingredients had been mixed and heated together to 50° C. The reaction mixture is stirred mechanically for 10-15 seconds after the TEOS is added, and then allowed to react for one hour in an ultrasonic bath. Example 3 is stable for about 6 weeks. The product is centrifuged to isolate silicate particles for SEM analysis. The particle size by SEM is approximately 200-500 nm.

(15) Comparative Sample F is made in the same manner as Example 2, except Polyol A is replaced with a 2000 equivalent weight, nominally hexa-functional random copolymer of propylene oxide and ethylene oxide (Polyol B). Polyol B contains approximately 10% by weight polymerized ethylene oxide. Fewer than 20% of its hydroxyl groups are primary hydroxyls. Polyol B is immiscible with the water in the reaction mixture. A highly non-homogeneous product with very poor stability is obtained.

EXAMPLES 4 AND 5 AND COMPARATIVE SAMPLE G

(16) Example 4 is made in the same general manner as Example 1, from the following ingredients: 15 parts TEOS, 5 parts ammonia water, 4 parts of water and 76 parts of Polyol A. This product is stable for more than six months. Example 4 has a hydroxyl number of 34.3, contains 0.02% by weight water and has a viscosity of 469 cSt at 40° C. Total volatiles (including water) are less than 0.1% by weight.

(17) Example 5 is made in the same general manner as Example 2, using the same formulation as Example 4. This product is stable for more than six months. Example 5 has a hydroxyl number of 43.4, contains 0.035% by weight water and has a viscosity of 407 cSt at 40° C. Total volatiles (including water) are less than 0.1% by weight.

(18) Comparative Sample G is made in the same general manner as Example 4, except the reaction mixture is heated to 75° C. The reaction mixture gels during the reaction and cannot be taken for particle size measurement.

EXAMPLE 6

(19) Example 4 is duplicated, except the ammonia water is added gradually to prevent an exothermic temperature rise from occurring. The product, like Example 4, is stable for at least six months. It has a hydroxyl number of 35.5, contains 0.06% by weight water, has a viscosity of 466 cSt at 40° C. and total volatiles (including water) of below 0.1 weight percent.

(20) For comparison, Polyol A by itself has a hydroxyl number of 37.5, contains 0.04% by weight water and has a viscosity of 369 cSt at 40° C.

(21) A viscoelastic (VE) polyurethane foam is made from the Example 6 dispersion For comparison, a similar foam (Comparative VE Foam A) is made substituting Polyol A for the Example 6 dispersion and a second comparative (Comparative VE foam B) is made by dispersing previously-formed fumed silica particles in polyols before performing the foaming reaction. The formulations are as set forth in Table 1 following.

(22) TABLE-US-00001 TABLE 1 Parts By Weight Inventive Comparative Comparative Ingredient VE Foam VE Foam A VE Foam B Polyol 1.sup.1 45 45 45 Polyol 2.sup.2 22.5 22.5 22.5 Polyol A 2.5 32.5 32.5 Example 6 30 0 0 Fumed Silica 0 0 1.8 Particles.sup.3 Catalysts.sup.4 0.32 0.32 0.21 Silicone Surfactant 0.8 0.8 0.8 Polymeric MDI.sup.5 To 84 index To 84 index To 84 index Water 2.05 2.05 2.05 .sup.1A nominally trifunctional copolymer of propylene oxide and ethylene oxide having a hydroxyl equivalent weight of 335. This product contains 60% by weight oxyethylene units. .sup.2A nominally trifunctional poly(propylene oxide) having a hydroxyl equivalent weight of 234. .sup.3Hydrophilic fumed silica particles have a surface area of 200 m.sup.2/g, sold as Aerosil ® 200 by Evonik Industries. These particles are pre-blended into the mixture of Polyols 1, 2 and A. .sup.4A mixture of tin and amine catalysts. .sup.5Isocyanate equivalent weight 130, isocyanate functionality 2.1-2.25.

(23) Various foam properties are evaluated for both the inventive foam and Comparative VE Foam A. Results are as indicated in Table 2. Comparative VE Foam B collapses during foaming, despite attempts during the foam production to disperse the fumed silica particles uniformly into the polyols.

(24) TABLE-US-00002 TABLE 2 Inventive Comparative Comparative Property VE Foam VE Foam A VE Foam B Density, kg/m.sup.3 49.2 44.2 Collapses Compression Force Deflection, kPa 25% compression 2.2 1.4 50% compression 3.3 2.7 65% compression 5.6 4.7 SAG factor 2.5 2.5 Ratio, hardness/ 6.7 6.1 density Hysteresis, % 63 58 Airflow (crushed 2.82 0.94 foam, l/s) Tensile Strength, kPa 80 55 Elongation, % 157 128 Tear strength, N/m 192 160 Resilience, % 12 6 Cal 117 vertical Pass, 8 cm Fail burning results char length, 5 second after flame

(25) The dispersion of the invention is seen to promote load bearing, cell opening (higher airflows), improve physical properties (increased tensile, tear and elongation) and improve flame resistance on the Cal 117 test. The formulation containing the dispersion processes easily to make good quality viscoelastic foam.

(26) Similar results are obtained using a toluene diisocyanate-based formulation.

(27) A high resiliency foam is made using the Example 6 dispersion. For comparison, a similar foam is made substituting another polyol (Polyol 3) for the Example 6 dispersion. The formulations are as set forth in Table 3:

(28) TABLE-US-00003 TABLE 3 Parts By Weight Inventive Comparative Ingredient HR Foam HR Foam Polyol 3.sup.1 0 20 PIPA Polyol.sup.2 80 80 Example 6 20 0 Crosslinker.sup.3 1.2 1.2 Catalysts.sup.4 0.78 0.80 Silicone Surfactant 0.25 0.25 TDI.sup.5 To 105 index To 105 index Water 2.53 2.53 .sup.1A nominally trifunctional block polymer of propylene oxide and ethylene oxide having a hydroxyl equivalent weight of about 1550, containing mostly primary hydroxyl groups. .sup.2A dispersion of 20% by weight of polyisocyanate polyaddition (PIPA) particles in 80% of nominally trifunctional poly(propylene oxide) having poly(ethylene oxide) end-capping. .sup.3Ortegol 204, from Evonik Industries. .sup.4A mixture of tin and amine catalysts. .sup.580/20 mixture of 2,4- and 2,6-isomers, isocyanate functionality approximately 2.0.

(29) Various foam properties are evaluated for both the inventive and comparative HR foams. Results are as indicated in Table 4.

(30) TABLE-US-00004 TABLE 4 Inventive Comparative Property VE Foam VE Foam Density, kg/m.sup.3 38.9 34.5 Compression Force Deflection, kPa 25% compression 4.7 3.2 50% compression 7.4 5.2 65% compression 12.7 9.3 SAG factor 2.7 2.9 Ratio, hardness/ 19 15 density Hysteresis, % 67 71 Airflow (crushed 1.88 1.95 foam, l/s) Tensile Strength, kPa 132 90 Elongation, % 94 94 Resilience, % 48 55

(31) The dispersion of the invention significantly increases load-bearing and tensile strength while being easily processable. These benefits are seen despite a very low level of silicate particles in the foam, and even though the foam formulation already contains a significant quantity of other dispersed polymer particles.