Process making polymer polyol having monodisperse dispersed polymer particles

Abstract

Polymer polyols are made in a seeded process, in which styrene and acrylonitrile are polymerized in the presence of a base polyol, a seed dispersion and a solvent. The seed dispersion contains an unsaturated macromer. The process produces a polymer polyol in which the dispersed phase particles have a particle size of 1 to 3 μm and a particle size span of less than 1.25. The polymer polyols are very useful for making flexible polyurethane foam for cushioning applications, in which high airflows and good load bearing are needed.

Claims

1. A process for making a polymer polyol that contains styrene/acrylonitrile copolymer particles dispersed in a continuous phase that includes at least one polyol, comprising the steps of a) forming a seed dispersion containing 5 to 25 weight-% of an unsaturated macromer, 2.5-20 weight-% of styrene polymer or copolymer particles having a particle size of 50 to 500 nm, and 55-92.5 weight-% of a seed dispersion carrier polyol, the weight-percentages being based on the weight of the seed dispersion; b) forming a carrier mixture containing the seed dispersion, a base polyol and a solvent, and dispersing a monomer mixture that includes at least 25 weight-% styrene and greater than 20 weight-% acrylonitrile, based on the weight of the monomer mixture, into the carrier mixture, wherein i) the amount of seed dispersion is sufficient to provide 0.025 to 0.35 weight percent seed particles and 0.1 to 0.75 weight percent of unsaturated macromer based on the combined weight of the carrier mixture and monomer mixture; ii) the weight of the monomer mixture is at least 200 times the weight of the seed particles and when polymerized is sufficient to provide the polymer polyol with at least 30 weight-percent dispersed polymer particles and iii) the amount of the solvent is 6 to 20% of the combined weight of the carrier mixture and the monomer mixture c) polymerizing the dispersed monomer mixture to form polymer particles dispersed in the carrier mixture and then d) removing the solvent from the carrier mixture to form a polymer polyol product containing at least 30 weight-percent dispersed polymer particles, wherein the dispersed polymer particles have a particle size of 1 to 3 μm and a particle size span of less than 1.25.

2. The process of claim 1, wherein the solvent is one or more of an aromatic hydrocarbon, an aliphatic hydrocarbon or a monoalcohol.

3. The process of claim 2, wherein the solvent includes isopropanol.

4. The process of claim 2, wherein the amount of monomer mixture is 200 to 500 times the weight of the seed particles.

5. The process of claim 4, wherein the amount of seed dispersion is sufficient to provide 0.1 to 0.25 weight percent seed particles.

6. The process of claim 5, wherein the particle size of the seed particles is 75 to 150 nm.

7. The process of claim 5, wherein the seed dispersion is prepared by homopolymerizing or copolymerizing styrene in the presence of the seed dispersion carrier polyol, the macromer and 5 to 20 weight-% of a solvent.

8. The process of claim 5, wherein the polymer polyol product contains 35 to 55 weight percent dispersed polymer particles.

9. The process of claim 5, wherein the amount of solvent present in step b) is 6 to 16 weight-%, based on the combined weight of the carrier mixture and the monomer mixture.

10. The process of claim 5, wherein the base polyol is one or more polyether polyols having a hydroxyl equivalent weight of 400 to 2500.

11. The process of claim 2, wherein step c) is performed under sufficient pressure to prevent the solvent from volatilizing.

12. The process of claim 6 wherein the amount of seed dispersion is sufficient to provide 0.1 to 0.5 weight percent of unsaturated macromer based on the combined weight of the carrier mixture and monomer mixture.

Description

EXAMPLES

(1) Polyol A is a nominally trifunctional random copolymer of 90% propylene oxide and 10% ethylene oxide, having a molecular weight of 3000.

(2) Polyol B is a 1000 molecular weight, nominally trifunctional random copolymer of propylene oxide and ethylene oxide.

(3) Polyol C is a 1000 molecular weight, nominally trifunctional polymer of propylene oxide.

(4) Polyol D is a 3100 molecular weight, nominally trifunctional random copolymer of propylene oxide and ethylene oxide.

(5) The Macromer is a hexafunctional random copolymer of about 89% propylene oxide and 11% ethylene oxide reacted with about 0.55 moles of TMI per mole of copolymer. The Macromer molecules contain 1-2 polymerizable carbon-carbon double bond per molecule and 4-5 hydroxyl groups per molecule.

(6) A. Preparation of Seed Dispersion A

(7) Seed dispersion A is made in a continuous stirred tank reactor with a recirculation loop from the following starting materials:

(8) TABLE-US-00001 TABLE 1 Ingredient Parts by Weight Styrene 7.38 Acrylonitrile 2.80 Polyol A 66.25 Macromer 12.10 Free radical initiator 0.12 Isopropanol 11.35

(9) The polymerization is performed at a temperature of 115° C. under pressure sufficient to prevent the monomers and isopropanol from volatilizing, until about 70% of the monomers are converted to polymer. The resulting seed dispersion is then cooled to room temperature, maintaining sufficient pressure to prevent the isopropanol from volatilizing. The resulting seed dispersion contains about 11.35% isopropanol, 66.25% Polyol A, 7% of seed particles, 2.3% residual styrene and 0.9% residual acrylonitrile. The particle size is 100 nm.

(10) B. Preparation of Seed Dispersion B

(11) Seed dispersion B is made in a batch reactor from the following starting materials:

(12) TABLE-US-00002 TABLE 2 Ingredient Parts by Weight Styrene 7.45 Acrylonitrile 2.83 Polyol A 66.20 Macromer 12.10 Free radical initiator 0.12 Isopropanol 11.30

(13) 56.74 parts of the polyol are blended with the macromer and isopropanol, charged to a reactor under a nitrogen atmosphere, and heated to 90° C. with stirring. The remaining ingredients are mixed separately. The reactor set point is increased to 110° C. and the remaining ingredients are fed into the reactor over 5 minutes, then allowed to polymerize at 110° C. for 45 minutes, under pressure to keep the isopropanol from volatilizing. The resulting seed dispersion is then cooled to room temperature, maintaining sufficient pressure to prevent the isopropanol from volatilizing. Conversion to monomer is about 70%. Seed Dispersion B contains 66.2% Polyol A, 11.3% isopropanol, 6.2% seed particles, 2.9% residual styrene and 1.0% residual acrylonitrile. The particle size is 110 nm.

(14) C. Preparation of Polymer Polyols

Example 1

(15) 19.82 parts of Polyol A are mixed with 6.25 parts of isopropanol and 2.5 parts of Seed Dispersion A, charged to a batch reactor under nitrogen, and heated to 110° C. Separately, 26.5 parts of styrene, 34.34 parts of Polyol A, 10.05 parts of acrylonitrile, 0.24 parts of a free radical initiator and 0.3 parts of n-dodececyl mercaptan are mixed. This mixture is fed into the reactor over 180 minutes while maintaining a temperature of 110° C., a nitrogen atmosphere, stirring and sufficient pressure to keep the isopropanol from volatilizing. Polymerization is continued for 60 minutes after addition of the monomer stream is complete. The reactor is allowed to cool to 40° C., and isopropanol and other volatiles are removed under vacuum to yield a polymer polyol product having 39.4% solids. The particle size is 2.11 μm and the particle size span is 1.14. The viscosity per ASTM D4878 is 4830 mPa.Math.s at 25° C. and 100 sec.sup.−1. The overall recipe is as follows:

(16) TABLE-US-00003 TABLE 3 Weight-% From Seed From Remainder Ingredient Dispersion of Recipe Total Polyol A 1.656 54.16 55.816 Macromer 0.303 0 0.303 Seed Particles 0.175 0 0.175 Isopropanol 0.284 6.25 6.534 Styrene 0.057 26.5 26.557 Acrylonitrile 0.023 10.05 10.073 N-dodecylmercaptan Negligible 0.3 0.3 Free Radical Negligible 0.120 0.120 Initiator Ratio, Monomer 209 Mixture/Seed Particles

Example 2

(17) 19.93 parts of Polyol A are mixed with 6.25 parts of isopropanol and 2.5 parts of Seed Dispersion B, charged to a batch reactor under nitrogen, and heated to 110° C. Separately, 26.5 parts of styrene, 34.53 parts of Polyol A, 10.05 parts of acrylonitrile and 0.24 parts of a free radical initiator are mixed. This mixture is fed into the reactor over 180 minutes while maintaining a temperature of 110° C., a nitrogen atmosphere, stirring and sufficient pressure to keep the isopropanol from volatilizing. Polymerization is continued for 60 minutes at 115° C. after addition of the monomer stream is complete. The reactor is allowed to cool to 40° C., and isopropanol and other volatiles are removed under vacuum to yield a polymer polyol product having 39.1% solids. The particle size is 1.92 μm and the particle size span is 0.43. The viscosity is 5780 mPa.Math.s at 25° C. and 100 sec.sup.−1. The overall recipe is as follows:

(18) TABLE-US-00004 TABLE 4 Weight-% From Seed From Remainder Ingredient Dispersion of Recipe Total Polyol A 1.655 54.46 56.115 Macromer 0.303 0 0.303 Seed Particles 0.158 0 0.158 Isopropanol 0.283 6.25 6.533 Styrene 0.073 26.5 26.573 Acrylonitrile 0.024 10.05 10.074 Free Radical Negligible 0.120 0.120 Initiator Ratio, Monomer 232 Mixture/Seed Particles
D. Preparation of Flexible Polyurethane Foams

(19) Viscoelastic polyurethane foams are made by mixing ingredients as listed in Table 5.

(20) TABLE-US-00005 TABLE 5 Parts By Weight Ingredient Inventive Foam Comparative Foam C-A Polyol B 50 50 Polyol C 15 15 Polyol D 15 15 Example 2 Polymer Polyol 20 0 Comparative Polymer Polyol.sup.1 0 20 Water 2.1 2.1 Surfactant 0.8 0.8 Catalyst Blend 0.3 0.3 Polymeric MDI To 71.5 index To 71.5 index .sup.1A 40% solids copolymer polyol in Polyol A, having a broad polymodal particle size distribution with particles ranging from 300 to 3000 nm in size with a major peak centered at about 500-600 nm.

(21) In each case, all ingredients except the polymeric MDI are mixed together, followed by adding the polymeric MDI. The resulting reaction mixture is then poured into an open box and cured rise freely and cure to foam a viscoelastic foam. Foam properties are measured for each foam according to ASTM D3574, and are as indicated in Table 6.

(22) TABLE-US-00006 TABLE 6 Property Comparative Foam Inventive Foam Airflow, cubic ft/min (L/s) 1.65 (0.78) 5.45 (2.57) Density, lb/ft.sup.3 (kg/m.sup.3) 3.0 (48) 3.2 (51.2) Compression Strength, 90% 84.8 85.6 Resiliency, % 3 3.4 Tear Strength, lb/in (N/m) 0.77 (0.09) 0.95 (0.11) Tensile Strength, psi (kPa) 5.7 (39) 8.3 (57) Elongation at break, % 92 103 Hysteresis, % 82.2 84.6

(23) As can be seen from the data in Table 6, the foam made using a polymer polyol of the invention has significantly greater airflow than the comparative foam, which is made using a polymer polyol with a wide particle size distribution and a large proportion of submicron particles. The advantage in airflow is obtained without significant losses in other properties which are generally equivalent between the two foams. Tensile, tear and elongation are all somewhat improved in the foam made with the polymer polyol of the invention.