Low-viscosity phosphate polyols

Abstract

A novel phosphate polyol formulation is described, comprising a polyester polyol, a flame retardant comprising a phosphate polyol, a blowing agent, a catalyst, a surfactant, and a fire-retardant aromatic isocyanate. A further embodiment includes a phosphorus compound, such as a phosphate, a phosphate ester, or an alkyl phosphate such as triethyl phosphate.

Claims

1. A phosphate polyol formulation comprising: a polyester polyol; a halogen-free phosphate polyol; a blowing agent; a catalyst; a surfactant; an aromatic isocyanate; and a fire-retardant non-isocyanate-reactive compound, wherein the fire-retardant non-isocyanate-reactive compound comprises a triethyl phosphate compound and wherein a weight ratio of the halogen-free phosphate polyol to the triethyl phosphate compound is approximately 90:10.

2. A phosphate polyol formulation comprising: a polyester polyol; a halogen-free phosphate polyol; a blowing agent; a catalyst; a surfactant; an aromatic isocyanate; and a fire-retardant non-isocyanate-reactive compound, wherein the fire-retardant non-isocyanate-reactive compound comprises a triethyl phosphate compound and wherein a weight ratio of the halogen-free phosphate polyol to the triethyl phosphate compound is approximately 80:20.

3. A phosphate polyol formulation comprising: a polyester polyol; a halogen-free phosphate polyol; a blowing agent; a catalyst; a surfactant; an aromatic isocyanate; and a halogen-free fire-retardant non-isocyanate-reactive compound, wherein the halogen-free fire-retardant non-isocyanate-reactive compound comprises a triethyl phosphate compound and wherein a weight ratio of the halogen-free phosphate polyol to the triethyl phosphate compound is approximately 70:30.

4. A phosphate polyol formulation comprising: a polyester polyol; a halogen-free phosphate polyol; a blowing agent; a catalyst; a surfactant; an aromatic isocyanate; and a halogen-free fire-retardant non-isocyanate-reactive compound, and wherein the phosphate polyol formulation comprises 7.5 parts by weight of the halogen-free phosphate polyol per hundred parts by weight of the polyester polyol.

5. A phosphate polyol formulation comprising: a polyester polyol; a halogen-free phosphate polyol; a blowing agent; a catalyst; a surfactant; an aromatic isocyanate; and a halogen-free fire-retardant non-isocyanate-reactive compound, and wherein the phosphate polyol formulation comprises 15.0 parts by weight of the halogen-free phosphate polyol per hundred parts by weight of the polyester polyol.

Description

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

(1) While the invention may be susceptible to embodiment in different forms, there will be described in detail specific embodiments with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein.

(2) The invention provides phosphate polyols with lower viscosity, high phosphorus content and hydroxyl numbers similar to those of commonly-used polyols. The invention minimizes the impact on foam formulation processing and foam physical properties, which simplifies incorporation into existing formulations. Use levels are comparable to those of existing fire retardants, as are mass and shape retention when exposed to flame.

(3) The formulated phosphate polyols of the preferred embodiment of the present invention provide acceptable weight loss and improved shape retention for polyurethane foams exposed to fire conditions, thus limiting fire spread. The phosphate polyol compositions also provide improved thermal stability to limit generation of volatile species that can provide additional fuel for a fire.

(4) The invention is useful for rigid polyurethane foam, with applicability to flexible foams and other synthetic and natural polymers.

(5) The invention provides low-viscosity phosphate polyol compositions which allow for the simultaneous optimization of rigid foam fire performance and char formation, while minimizing the impact on foam formulation processing. Use levels are comparable to those of existing halogenated fire retardants, as are char formation and mass and shape retention when exposed to flame.

(6) Phosphate polyol compositions were produced according to the following examples.

Example 1

(7) Charge 1480 g of phosphoric acid to a 20 L reactor, heat to 35-40 C with stirring, and heat for 1 hour. Charge 5200 g of propylene oxide and nitrogen sparge to remove unreacted propylene oxide.

(8) Final polyol product has OH #362, color Gardner 5.5, viscosity 820 cps and % phosphorus 6.7.

(9) Optionally, produce a formulation for even more improved fire retardant performance by blending phosphate polyol prepared via prior art methods as indicated above with an appropriate quantity of a non-isocyanate-reactive compound having a fire-retardant property, preferably a phosphate, more preferably a trialkyl phosphate, most preferably triethyl phosphate, to produce the inventive compositions (Table 3, below).

Example 2

(10) Polyurethane foams were prepared from the formulations in Table 1.

(11) TABLE-US-00001 TABLE 1 Rigid Foam Formulations to Evaluate Phosphate Polyols Product Chemical PPHP Polyol Stepanpol Modified aromatic polyester 100 PS-2352 Flame Fyrol PCF Tris (1-chloro-2-propyl) Various retardant phosphate (TCPP) Flame Inventive Phosphate polyol composition Various retardant phosphate polyol Blowing Water 0.50 agent Catalyst PEL-CAT Potassium octoate in diethylene 4.50 9540-A glycol Catalyst PEL-CAT Pentamethyldiethylene triamine 0.19 9749-A (PMDETA) Silicone PEL-SIL Silicone polyether surfactant 1.17 surfactant 9920 Blowing 2-Me i-Pentane 23.20 agent Butane Index Isocyanate Mondur Aromatic isocyanate 280 (MDI) 489 Stepanpol PS-2352 polyester polyol OH# 237 available from Stepan. Fyrol PCF available from ICL. PEL-CAT 9540-A, PEL-CAT 9749-A and PEL-SIL 9920 available from Ele' Corporation. Mondur 489 (30.8% NCO) available from Covestro.

(12) The foams for burn testing were prepared as follows. The polyol, flame retardant(s), water, catalysts and surfactant (B side) were premixed and allowed to incubate at 25 C for at least 24 hours prior to foam preparation. The isocyanate and pentane blowing agent (A side) were weighed into a capped jar and incubated for at least one hour prior to foam preparation. The B side mixture was weighed into a tared 32-ounce paperboard cup. The A side mixture was shaken vigorously for 25 seconds and rapidly weighed into the paperboard cup. The cup was mixed at 3000 rpm for six seconds and the foam was allowed to rise freely. The foam was cured at 25 C for a minimum of 24 hours before being cut into pieces for burn testing as specified in ASTM D-635.

(13) Burn testing was conducted according to a method based on ASTM D-635. The method was modified to use a propane flame (flame temperature in air 1967 C) instead of a natural gas flame (methane flame temperature in air 1950 C). Three to four foam samples were burned for 30 seconds and the weight loss values averaged. Results are shown in Table 2. All samples were self-extinguishing prior to removal of the flame after 30 seconds.

(14) TABLE-US-00002 TABLE 2 Phosphate Polyol Burn Test Exp. 1 Exp. 2 Flame retardant Control No FR Exp. 3 Exp. 4 TCPP (pphp) 7.5 0.0 0.0 0.0 Phosphate polyol 0.0 0.0 7.5 15.0 (pphp) % Mass Loss 16.5 54.2 34.5 30.0

(15) Experiment 1 is the TCPP control. Experiment 2 with no flame retardant shows considerably more mass loss as expected. Experiments 3 and 4 show that the phosphate polyol is not as effective as the halogenated control, but is appreciably more effective than no fire retardant (Experiment 2). The phosphate polyol is halogen-free and is incorporated into the polymer network, which helps to maintain physical properties.

(16) Performance of the phosphate polyol can be further improved by adding a non-isocyanate-reactive compound having a fire-retardant property, such as a phosphorus compound to the Table 1 formulation. The non-isocyanate-reactive compound can be a phosphate, a phosphate ester, or an alkyl phosphate, such as, for example, trialkyl phosphate. The results are shown in Table 3.

(17) TABLE-US-00003 TABLE 3 Phosphate Polyol/Triethyl Phosphate (TEP) Burn Test Exp. 1 Exp. Exp. Exp. Exp. Exp. Exp. Exp. Flame retardant Control 2 3 4 5 6 7 8 TCPP (pphp) 7.50 0.00 0.00 0.00 0.00 0.00 0.00 0.00 Phosphate polyol (pphp) 0.00 6.75 6.00 5.25 0.00 13.50 12.00 10.50 Triethyl phosphate 0.00 0.75 1.50 2.25 7.50 1.50 3.00 4.50 (pphp) Weight ratio phosphate 90:10 80:20 70:30 90:10 80:20 70:30 polyol:TEP Total FR (pphp) 7.50 7.50 7.50 7.50 7.50 15.00 15.00 15.00 % Mass Loss 14.5 33.7 27.8 18.6 11.5 26.1 19.9 10.4

(18) Addition of triethyl phosphate brings weight loss in line with that of the control. All samples were self-extinguishing prior to removal of the flame after 30 seconds.

(19) Thermogravimetric analysis (TGA) is a widely-accepted analytical technique that provides an indication of relative thermal stability for a series of materials. TGA was conducted to better understand thermal stability and char formation without direct flame contact.

(20) In this study, a known mass of foam was heated from 30 C-750 C at a steady rate of 20 C./min under nitrogen at 40 ml/min. (Thermal stability is expressed as percent retention of foam weight at a particular temperature relative to the foam's initial weight at 30 C. See, for example, U.S. Pat. No. 8,916,620, Process for polyurethane-modified polyisocyanurate foam with improved thermal stability, the disclosure of which is incorporated herein by reference.)

(21) TABLE-US-00004 TABLE 4 Phosphate Polyol/Triethyl Phosphate Thermogravimetric Analysis Exp. 1 Flame retardant Control Exp. 2 Exp. 3 Exp. 4 TCPP (pphp) 7.50 0.00 0.00 0.00 Phosphate polyol (pphp) 0.00 5.25 0.00 7.50 Triethyl phosphate (pphp) 0.00 2.25 7.50 0.00 Weight ratio phosphate polyol:TEP 70:30 Total FR (pphp) 7.50 7.50 7.50 7.50 % Mass retained 300 C 95.3 94.6 81.0 94.0 % Mass retained 400 C 66.7 65.6 58.9 63.7 % Mass retained 500 C 58.2 60.4 51.1 57.4 % Mass retained 600 C 47.3 53.5 35.0 52.2 % Mass retained 700 C 30.8 40.8 8.7 44.9 % Mass retained 745 C 23.5 34.9 0.0 41.4

(22) The TCPP control (Table 4, Experiment 1) displays good mass retention up to 500 C but accelerating mass loss above 500 C. The TCPP control (Tables 2 and 3, experiment 1) also displays low mass loss when exposed directly to a flame, thus demonstrating a good balance between flame resistance and thermal stability.

(23) An inventive phosphate polyol/triethyl phosphate composition (Table 4, Experiment 2) shows mass retention comparable to that of the control up to 500 C and superior mass retention above 500 C. This phosphate polyol/triethyl phosphate composition (Table 3 Experiment 4) shows mass loss close to that of the control when exposed to flame, also demonstrating a good balance between flame resistance and thermal stability.

(24) Triethyl phosphate alone (Table 4, Experiment 3) shows very poor mass retention, especially above 400 C, with complete mass loss by 745 C. However, triethyl phosphate (Table 3, Experiment 5) shows low weight loss when exposed directly to flame.

(25) Phosphate polyol alone (Table 4, Experiment 4) shows good mass retention at all temperatures, but high mass loss (Table 3, Experiments 3 and 4) when exposed directly to flame.

(26) When formulating a multi-component composition with a desired set of target properties, a common strategy is to utilize individual components with a range of properties, with the hope that the average performance for the composition is acceptable. Given the objective of developing a composition that provides good mass retention under both direct flame and thermal resistance conditions, the observation that triethyl phosphate demonstrates very poor mass retention in the TGA experiment would not motivate one skilled in the art to add increasing levels of triethyl phosphate to improve the overall performance of the phosphate polyol.

(27) Increasing triethyl phosphate levels to improve mass retention when exposed to fire would be expected to significantly degrade mass retention under thermal stability conditions. Unexpectedly, we find significant positive synergy between triethyl phosphate and the phosphate polyol in terms of thermal stability relative to the performance of the individual components. Given the numerous phosphorus-based fire retardants known, achieving the desired objectives is not a matter of routine optimization, but rather requires inventive insight to identify synergistic behavior.

(28) While preferred embodiments of the present invention are shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the appended claims.