Polyisocyanate polyaddition polyol manufacturing process and product

Abstract

PIPA polyols are made in a two-step process. In the first step, a base polyether polyol and a polyisocyanate are reacted to form a mixture that contains unreacted base polyol, unreacted polyisocyanate and adducts of the base polyol and polyisocyanate. A low equivalent weight polyol is then added and reacted in a second step to form the dispersion. The process unexpectedly produces a stable dispersion of the fine PIPA particles in the base polyol, even when the base polyol contains mostly secondary hydroxyl groups. The process also permits the tuning of product viscosity by increasing or decreasing the extent of reaction in the first step.

Claims

1. A process for preparing a dispersion of polyisocyanate polyaddition particles in a base polyol, comprising a) combining (1) 1 to 50 parts by weight of a polyisocyanate having an isocyanate equivalent weight of up to 300 and (2) 100 parts by weight of one or more liquid base polyether polyols, the base polyether polyol(s) having an average hydroxyl equivalent weight of at least 200, a nominal hydroxyl functionality of at least 2.5, wherein at least 75% of the hydroxyl groups of the base polyol are secondary hydroxyl groups, and reacting the polyisocyanate with the polyether polyol while mixing to produce a mixture containing unreacted base polyol, unreacted polyisocyanate compound and one or more isocyanate group-containing adducts of the base polyol with the polyisocyanate; b) then dispersing (3) a low equivalent weight polyol having an equivalent weight of up to 80 and 2 to 6 hydroxyl groups per molecule and optionally additional polyisocyanate into the mixture formed in step a), wherein 1.05 to 1.75 equivalents of the low equivalent weight polyol are provided per equivalent of isocyanate groups provided by the mixture formed in step a) and said additional polyisocyanate if any, and reacting the low equivalent weight polyol with the isocyanate groups to form polyisocyanate polyaddition particles dispersed in the base polyether polyol.

2. The process of claim 1 wherein at least 85% of the hydroxyl groups of the base polyol are secondary hydroxyl groups.

3. The process of claim 1 wherein the base polyol is at least one polyol selected from i) a nominally trifunctional poly(propylene oxide) homopolymer having a hydroxyl equivalent weight of 900 to 1350, and ii) a nominally trifunctional random copolymer of 80 to 99.5% by weight propylene oxide and 0.5 to 20% by weight ethylene oxide, based on the combined weight of the propylene oxide and ethylene oxide, the random copolymer having a hydroxyl equivalent weight of 900 to 1350, wherein 92 to 100% of the hydroxyl groups of the base polyol are secondary hydroxyl groups.

4. The process of claim 1, wherein the low equivalent weight polyol is triethanolamine or a mixture containing at least 75% by weight of triethanolamine by weight of the mixture.

5. The process of claim 1, wherein the polyisocyanate includes toluene diisocyanate or diphenylmethanediisocyanate.

6. A process for preparing a dispersion of polyisocyanate polyaddition particles in a base polyol, comprising a) combining (1) 1 to 50 parts by weight of toluene diisocyanate and (2) 100 parts by weight of a liquid base polyether polyol, wherein the base polyol is at least one polyol selected from i) a nominally trifunctional polypropylene oxide) homopolymer having a hydroxyl equivalent weight of 900 to 1350, and ii) a nominally trifunctional random copolymer of 80 to 99.5% by weight propylene oxide and 0.5 to 20% by weight ethylene oxide, based on the combined weight of the propylene oxide and ethylene oxide, the random copolymer having a hydroxyl equivalent weight of 900 to 1350, wherein 85 to 100% of the hydroxyl groups of the base polyol are secondary hydroxyl groups, and reacting the toluene diisocyanate with the base polyether polyol while mixing to produce a mixture containing unreacted base polyol, unreacted toluene diisocyanate and one or more isocyanate group-containing adducts of the base polyol with the toluene diisocyanate; b) then dispersing (3) triethanolamine or a mixture of 75 to 99.9% by weight triethanolamine and 0.1 to 25% by weight, based on the weight of the mixture, of one or more other polyols having a hydroxyl equivalent weight of up to 80 and 2 to 6 hydroxyl groups per molecule and optionally additional toluene diisocyanate into the mixture formed in step a), wherein 1.05 to 1.75 equivalents of the triethanolamine or mixture are provided per equivalent of isocyanate groups provided by the mixture formed in step a) and said additional toluene diisocyanate if any, and reacting the triethanolamine or mixture with the isocyanate groups to form polyisocyanate polyaddition particles dispersed in the base polyether polyol.

7. The process of claim 6, wherein in step a), 1 to 30% of the hydroxyl groups of the base polyether polyol react with isocyanate groups.

8. The process of claim 6, wherein steps a) and b) each are performed in the absence of a tin catalyst.

9. The process of claim 6 wherein in step (a), the base polyol and polyisocyanate are reacted for 5 seconds to 5 minutes before performing step (b).

10. The process of claim 6 wherein steps (a) and (b) are performed in the absence of an ionic surfactant, a silicone surfactant or a nonionic surfactant compound having one or more hydrophilic, internal or terminal poly(ethylene oxide) chains.

11. The process of claim 6, wherein steps (a) and (b) are performed in the presence of up to 2 weight percent water, based on the combined weights of base polyol, polyisocyanate, low equivalent weight polyol and water.

12. The process of claim 6, wherein step (b) is performed in the presence of a preformed PIPA polyol.

13. The process of claim 6, wherein step (a) is performed by continuously bringing the base polyol and toluene diisocyanate together in a mixhead to form a mixture which is continuously introduced into a tubular reactor where the base polyol and toluene diisocyanate react as the mixture passes through an initial portion of the tubular reactor to form a base polyol mixture, and step (b) is performed by introducing the low equivalent weight polyol and optionally an additional toluene diisocyanate into a downstream section of the tubular reactor and mixing it with the base polyol mixture formed in step (a), and then completing the reaction of the low equivalent weight polyol.

14. The process of claim 6, wherein the dispersion has a solids content of 8 to 25% by weight.

15. The process of claim 6, wherein at least 90 volume-% of the particles have a particle size of 0.1 to 5 μm.

16. The process of claim 6, wherein the dispersion has a viscosity of 750 to 20,000 mPa.Math.s at 20° C. with a solid content of at least 10% weight percent.

17. A dispersion of polyisocyanate polyaddition particles in a base polyether polyol made in accordance with the process of claim 1.

18. A dispersion of polyisocyanate polyaddition particles in a base polyether polyol made in accordance with the process of claim 6.

Description

EXAMPLE 1 AND COMPARATIVE SAMPLES A, B AND C

(1) Polyol A is a 3500 molecular weight, nominally trifunctional copolymer of 92% propylene oxide and 8% ethylene oxide. It is made using a potassium hydroxide catalyst, the residues of which have been removed. It contains about 0.1% by weight water. Fewer than 2% of its hydroxyl groups are primary, the remainder being secondary hydroxyls.

(2) The Seed PIPA polyol is a 10% solids PIPA polyol made by conventional means using a base polyol having mainly primary hydroxyl groups and TEOA (see WO 2012/154831).

(3) 88 parts of Polyol A and 2 parts of a seed PIPA polyol are charged into a high speed laboratory mixer. With rapid stirring, 5.32 parts of a room temperature toluene diisocyanate (80% 2,4-isomer, “80/20 TDI”) are added. After the toluene diisocyanate addition is completed, the mixture is stirred for 60 seconds, followed by addition of 0.4 parts of tin octoate catalyst. After additional 60 seconds of stirring, 4.69 parts of room temperature 99% pure triethanolamine are added with continued mixing. Mixing is continued for 300 seconds, during which time polyisocyanate polyaddition particles form. The particles remain suspended in the base polyol for a period of more than 3 months at room temperature. Product viscosity is 2300 mPa.Math.s. Such a PIPA polyol is useful to produce good conventional polyurethane flexible foam.

(4) Comparative Sample A is made using the same reactants and same amounts as Example 1, but following a conventional PIPA polyol manufacturing process as described in the examples of WO 94/20558. Changes to the catalyst package are also made to accommodate the process changes. With Comparative Sample A, the triethanolamine, catalyst, seed PIPA polyol and base polyol are combined first, mixed until the triethanolamine is dispersed, and then the 80/20 TDI is added. Polyisocyanate polyaddition particles form, but flake out almost immediately, confirming that the conventional PIPA polyol process as described in WO 94/20558 cannot be used with low reactivity polyols containing secondary hydroxyls at this level of seed PIPA polyol. Increasing the amount of this seed PIPA polyol will introduce significant amounts of primary hydroxyl groups into the product, which is disadvantageous because it will increase the product reactivity and sensitivity to tin catalyst levels in a conventional slabstock foam process.

(5) Comparative Samples B and C are made in the same manner as Comparative Sample A, except the catalyst is 0.2 parts of a zinc carboxylate in the case of Comparative Sample B and 0.2 parts of a dialkyltin carboxylate in the case of Comparative Sample C. In both cases and as with Comparative Example A, the polyisocyanate polyaddition particles form and almost immediately flake out of the dispersion.

EXAMPLES 2 AND 3

(6) Polyol B is a nominally trifunctional copolymer of propylene oxide and ethylene oxide having a hydroxyl number of about 48. It is made using a zinc hexacyanocobaltate catalyst complex. It contains about 0.1% by weight water. No more than 15% of its hydroxyl groups are primary, with the remainder of the hydroxyl groups being secondary hydroxyls.

(7) To make Example 2, 87.68 parts of room temperature Polyol B are mixed for two minutes with 0.2 part of a zinc carboxylate catalyst, 2 parts of a seed PIPA polyol, 0.1 part of a triethylenediamine catalyst solution and 5.52 parts of 80/20 TDI on a laboratory high-speed mixer, at which time 4.5 parts of triethanolamine are added with continued mixing. Mixing is continued without applied heat for another 5 minutes, at which time a stable PIPA dispersion is obtained.

(8) Particle size is measured using a Beckman Coulter LS Particle Size Analyzer. Essentially all particles are between 0.1 and 1 μm in size. The viscosity of the dispersion is measured using a Bohlin rheometer with cone-and-plate geometry, operated in a rotational mode at 20° C. The viscosity is recorded at its equilibrium value. The viscosity is 9150 mPa.Math.s. OH number is 58.

(9) To make Example 3, a mixture of 87.58 parts of Polyol B, 2 parts of the seed PIPA polyol described in Example 1, 0.2 parts of the zinc carboxylate catalyst and 0.05 part of the triethylenediamine catalyst solution is heated to 50° C. and stirred for 60 seconds. To this heated mixture is added 5.52 parts of toluene diisocyanate (80% 2,4-isomer), followed by mixing for two minutes. Then 4.5 parts triethanolamine are added, and mixing is continued for another 5 minutes to produce a stable dispersion having very small dispersed PIPA particles (in between 0.1 and 0.5 μm). Final PIPA polyol viscosity at 20° C. is 5400 mPa.Math.s. OH number is 61.1.

(10) The lower viscosity of Example 3 compared to Example 2 is believed to be due to a smaller extent of reaction between the base polyol and the polyisocyanate in the first step, at least in part because of the reduction in the amount of catalyst.

(11) Example 3 has a narrower particle size distribution than Example 2. This may be attributable to the preheating of the base polyol in Example 3. This reduces the viscosity of TEOA, which may permit the triethanolamine to disperse better into the base polyol mixture. In any case, it is surprising to get such a narrow distribution of fine PIPA particles in the final PIPA polyol, using the process of reacting TEOA last.

EXAMPLES 4 AND 5

(12) To make Example 4, 87.76 parts of room temperature Polyol B are mixed with 0.2 parts of a zinc carboxylate catalyst, 2 parts of a seed PIPA polyol, and 6.52 parts of a polymeric MDI (32% isocyanate groups, functionality 2.3) on a laboratory high-speed mixer for two minutes, at which time 3.52 parts of triethanolamine are added with mixing. Mixing is continued without applied heat for another 5 minutes, at which time a stable PIPA dispersion is obtained.

(13) A bimodal particle size is seen, with a major fraction of particles having sizes from 0.05 to 1 μm and another almost equally large fraction having a size between 1 and 5 μm in size. Viscosity is 3400 mPa.Math.s.

(14) To make Example 5, a mixture of 87.68 parts of Polyol B, 2 parts seed PIPA polyol, 0.2 parts of the zinc carboxylate catalyst and 0.1 part of the triethylenediamine catalyst solution is prepared on a high speed mixture. To this mixture is added 6.52 parts of the polymeric MDI, followed by mixing for two minutes. Then 3.52 parts triethanolamine are added, and mixing is continued for another 5 minutes to produce a stable dispersion having very small dispersed PIPA particles.

(15) The resulting dispersion has a monomodal particle size distribution, with essentially all particles between 0.05 and 0.5 μm in size. Viscosity is 5650 mPa.Math.s.

EXAMPLES 6-8

(16) Each of Examples 6-8 are made by mixing 88 parts of Polyol A, 2 parts of the seed PIPA polyol, 0.2 parts of the zinc carboxylate catalyst, 0.02 parts of the dialkyltin carboxylate catalyst, 5.76 parts toluene diisocyanate (80% 2,4-isomer) and 4.69 parts of triethanolamine. All components are at room temperature when added. The order of mixing for these experiments is as follows:

(17) Example 6: Mix Polyol A, seed PIPA polyol and toluene diisocyanate on the high speed mixer for 30 seconds, add the catalysts, mix another 30 seconds (total pre-reaction time 60 seconds), then add the triethanolamine. Mix for an additional 5 minutes.

(18) Example 7: Mix Polyol A, seed PIPA polyol and toluene diisocyanate on the high speed mixer for 60 seconds, add the catalysts, mix another 60 seconds (total pre-reaction time 120 seconds), then add the triethanolamine. Mix for an additional 5 minutes.

(19) Example 8: Mix Polyol A, seed PIPA polyol and toluene diisocyanate on the high speed mixer for 90 seconds, add the catalysts, mix another 90 seconds (total pre-reaction time 180 seconds), then add the triethanolamine. Mix for an additional 5 minutes.

(20) Results are as summarized in Table 1 below.

(21) TABLE-US-00001 TABLE 1 Sample Example 6 Example 7 Example 8 Pre-reaction time, s 60 120 180 Viscosity, mPa .Math. s 3050 4400 4550 Hydroxyl number, 61.8 62.1 Not measured. mg KOH/g Particle size Bimodal, with Trimodal, with Polymodal, with larger volume largest volume large volume fraction between 1 fraction between 1 fractions between and 20 μm and 5 μm, a smaller 0.05 and 0.8 μm (centered at about volume fraction and another large 5 μm) and smaller between 0.05 and volume fraction volume fraction 0.5 μm and a still between 1 and 5 μm. between 0.05 and smaller volume 0.5 μm. fraction between 10 and 20 μm.

(22) The longer the pre-reaction time, the higher the final viscosity of the PIPA polyol. The low OH numbers confirm that there is no unreacted TEOA present in the final PIPA polyol. Stable particles have all small sizes. Hence good grafting of the PIPA polymer has been obtained by reacting TEOA last.

EXAMPLES 9-12

(23) Examples 9 and 10 are made by mixing 87.78 parts of Polyol B, 2 parts of the seed PIPA polyol, 0.2 parts of the zinc carboxylate catalyst, 0.025 parts of the dialkyltin carboxylate catalyst, 5.52 parts toluene diisocyanate (80% 2,4-isomer) and 4.5 parts of triethanolamine. The polyol is preheated to 40° C.; all other components are at room temperature when added.

(24) In Example 11, the amount of Polyol B is reduced to 86.78 parts and in Example 12 the amount of Polyol B is 87.28 parts.

(25) The order of mixing for these experiments is as follows:

(26) Example 9: Mix Polyol B, seed PIPA polyol and tin catalyst on the high speed mixer for 60 seconds, add the toluene diisocyanate, mix another 90 seconds, add the zinc catalyst, mix another 30 seconds, then add the triethanolamine over 30 seconds. Mix for an additional 90 seconds.

(27) Example 10: Mix Polyol B, seed PIPA polyol and catalysts on the high speed mixer for 60 seconds, add the toluene diisocyanate, mix another 120 seconds, then add the triethanolamine over 30 seconds. Mix for an additional 90 seconds.

(28) Example 11: Mix Polyol B, seed PIPA polyol and catalysts on the high speed mixer for 60 seconds, add the toluene diisocyanate, mix another 150 seconds, add the triethanolamine over 30 seconds. Then mix for an additional 90 seconds.

(29) Example 12: Mix Polyol B, seed PIPA polyol and catalysts on the high speed mixer for 60 seconds, add the toluene diisocyanate, mix another 180 seconds, add the triethanolamine over 30 seconds. Then mix for an additional 90 seconds.

(30) Particle size, and viscosity are measured for each of these products, and are as reported in Table 2.

(31) TABLE-US-00002 TABLE 2 Sample Example 9 Example 10 Example 11 Example 12 Viscosity, mPa .Math. s 3200 2500 3300 3800 Particle size Bimodal, Bimodal, Bimodal, Bimodal, with with larger with larger with a large the larger volume volume volume volume fraction fraction fraction fraction between 0.05 between 2 between 1 between and 0.6 μm, and and 20 μm and 6 μm 0.05 and 0.5 μm a smaller (centered at (centered at and volume fraction about 5 μm) 3 μm, a another at 0.8 to 3 μm. and smaller smaller large volume volume volume fraction fraction fraction between between 0.05 between 1 0.05 and 0.5 μm. and 0.5 μm. and 5 μm.

(32) Examples 9 to 12 show the flexibility and the robustness of the process of the invention. All of Examples 9 to 12 are good dispersions despite the differences in pre-reaction times used. Longer pre-reaction times correlate to higher final PIPA polyol viscosities.