Flame-retardant polyurethane foam

Abstract

The thermoset foam comprises 0.2 to 4.0 wt. % of at least one aliphatic brominated polyether polyol, 2.0 to 7.0 wt. % of at least one aromatic brominated polyester polyol, and 2.0 to 7.5 wt. % of at least one flame retardant comprising an organic phosphate, organic phosphonate, or organic phosphite, wherein the ratio of the amount of aliphatic bromine expressed as a percentage of total bromine to the amount of aromatic bromine expressed as a percentage of total bromine is 10:90 to 50:50.

Description

[Technical Field]

[0001] The present invention relates to a flame-retardant polyurethane foam that is particularly suitable for use as a thermal insulation material for buildings. [Background technology]

[0002] Polyisocyanurate (PIR) foam boardstock is widely used as insulation in roof and wall assemblies in commercial and residential buildings. As a plastic foam product, PIR foams must meet stringent fire resistance requirements in addition to their heat resistance. In particular, PIR foams capable of passing the ASTM E84 or UL 723 tunnel burn test and the Factory Mutual (FM) 4880 room corner burn test are particularly desirable in all shapes (core, facing, and slit). Passing these tests would allow the foam product to remain exposed in both wall and ceiling installations (no need for any other assembly coverage). To provide better fire resistance, flame-retardant (FR) additives are used. These FR additives can provide increased fire resistance through either a vapor-phase or condensed-phase mechanism.

[0003] Current compositions capable of passing the FM 4880 room corner test include aryl brominated phthalate diols, nonreactive aliphatic brominated small molecules (n-propyl bromide, nPBr), and phosphate tris(1-chloro-2-propyl)phosphate (TCPP). Brominated nonreactive small molecule flame retardants such as nPBr are undesirable due to their high vapor pressure and high tendency to migrate from products, which can lead to environmental and worker health issues and potentially reduced product fire resistance over time. Additionally, because nPBr has a low boiling point of 71°C, most of this material will be released from the foam before the foam plastic reaches its thermal decomposition temperature (>200°C for polyurethanes) during a fire scenario. This premature release of nPBr leads to the inefficient use of vapor-phase flame retardants, thus requiring higher concentrations of brominated species in products to meet fire resistance requirements as specified by the flammability test standard.

[0004] TCPP, one of the most commonly used chlorinated phosphate esters, provides both condensed-phase and vapor-phase fire resistance in polyurethane foams. However, this material is currently facing environmental scrutiny from several regulatory agencies. This scrutiny will likely result in future restrictions on TCPP's use in commercial materials. The flame retardant industry has developed several alternatives to TCPP for use in polyurethane foams, but these materials are generally much more expensive than TCPP. Triethyl phosphate (TEP) is one low-cost alternative. Nevertheless, TEP has a boiling point (209°C) significantly lower than its thermal decomposition temperature (>300°C). TEP is considered a vapor-phase flame retardant rather than remaining in the condensed phase because its lower boiling point results in premature evaporation in a fire. Summary of the Invention [Problem to be solved by the invention]

[0005] Therefore, there is a continuing need to find cost-effective solutions for providing polyurethane foams that meet customer or government specifications and comply with changing environmental protection standards. [Means for solving the problem]

[0006] Thermosetting foams are 0.2 to 4.0 wt. % of at least one aliphatic brominated polyether polyol; 2.0 to 7.0 wt. % of at least one aromatic brominated polyester polyol; 2.0 to 7.5 wt. % of at least one flame retardant comprising an organic phosphate, an organic phosphonate, or an organic phosphite; wherein the ratio of the amount of aliphatic bromine expressed as a percentage of total bromine to the amount of aromatic bromine expressed as a percentage of total bromine is from 10:90 to 50:50. DETAILED DESCRIPTION OF THE INVENTION

[0007] Thermosetting Foam A "thermoset polyurethane foam" is a foam that cannot reversibly progress from a solid to a flowable state upon a change in temperature without degradation of the foam's polymer network.

[0008] The thermosetting foam of the present invention comprises: 0.2 to 4.0 wt. % of at least one aliphatic brominated polyether polyol; 2.0 to 7.0 wt. % of at least one aromatic brominated polyester polyol; 2.0 to 7.5 wt. % of at least one flame retardant; Includes.

[0009] Preferably, the ratio of the amount of aliphatic bromine expressed as a percentage of total bromine to the amount of aromatic bromine expressed as a percentage of total bromine is between 10:90 and 50:50. This ratio of components has been found to significantly improve vapor-phase flame retardant efficiency. A surprising finding was the passing of full-room corner tests at approximately half the bromine content (1.6% Br) compared to current commercial technology (3.0% Br) without affecting thermal insulation and other physical properties. Furthermore, the aliphatic Br / aromatic Br ratio is significantly lower than current technology.

[0010] Representative aliphatic brominated polyols are IXOL® B-251 or IXOL® M-125 available from Solvay Specialty Chemicals, Houston, TX.

[0011] An exemplary aromatic brominated polyol is SAYTEX® RB-9170 manufactured by Albemarle, Charlotte, NC.

[0012] flame retardants The preferred flame retardants are phosphorus-based flame retardants.

[0013] Suitable flame retardants include organic phosphates, organic phosphonates, organic phosphites or oligomeric alkyl phosphates. A representative organic phosphate is triethyl phosphate.

[0014] In one embodiment, the flame retardant is a blend of triethyl phosphate and oligomeric alkyl phosphate, wherein the ratio of triethyl phosphate to oligomeric alkyl phosphate is from 90:10 to 50:50.

[0015] A representative alkyl phosphate is triethyl phosphate.

[0016] Representative alkyl phosphates are Fyrol® PNX manufactured by ICL Industrial Products, Tarrytown, NY, EXOLIT® OP 550 or OP 560 manufactured by Clariant, Muttenz, Switzerland, butyl diphenyl phosphate, dibutyl phenyl phosphate, and triphenyl phosphate.

[0017] Other components of the form In some embodiments, an organosilicone surfactant may also be present to help reduce blister size during a fire event.

[0018] Thermoset foams may contain other components such as one or more selected from interfacial agents, phosphorus-containing compounds, chlorine-containing compounds, additional brominated flame retardants, preservatives, antioxidants, catalysts, colorants, bittering agents, fillers, infrared attenuating agents (such as carbon black, graphite, and titanium dioxide), and residual blowing or foaming agents.

[0019] The foams may be prepared by any suitable method known in the art, an exemplary method being described in US Pat. No. 4,572,865.

[0020] composite structure Thermosetting foams as described above can be used to manufacture composite structures such as flat panels in which at least one face sheet is bonded to at least one outer surface of the foam. Preferably, there is at least one face sheet bonded to at least one outer surface of the foam. The face sheet material can be plastic sheet or board, resin-impregnated fibrous yarn (prepreg), wood, or metal. A typical metal sheet is 24- or 26-gauge galvanized steel. A preferred metal is aluminum. The face sheet is attached to the foam under pressure and usually with heat by an adhesive film or from the resin in the prepreg. Curing can be carried out in a press, oven, or autoclave. Such techniques are well understood by those skilled in the art.

[0021] Test Method ASTM E84-19b Standard Test Method for Surface Burning Characteristics of Building Materials UL723-11 Standard Test Method for Surface Burning Characteristics of Building Materials FM 4880:2017 Evaluation of the Fire Performance of Insulated Building Panel Assemblies and Interior Materials NFPA 286 (2019) Standard Method of Flammability Testing for Evaluating the Contribution of Wall and Ceiling Interiors to Interior Fire Growth UL 1715 (1997) Standard for Flammability Testing of Interior Materials

[0022] Other test methods are listed below.

[0023] [Table 1] [Example]

[0024] The following examples are given to illustrate the invention and should not be construed as limiting it in any way. Examples prepared in accordance with the invention are designated by a numerical value. Control or comparative examples are designated by a letter.

[0025] The materials used in the PIR formulations are listed in Table 1, and the formulations are listed in Table 2. All parts in Table 2 are in parts per hundred parts of polyol unless otherwise specified. Table 3 summarizes the percentages of specific components in the formulations. Flammability test results for comparative and inventive examples are in Table 4.

[0026] [Table 2]

[0027] [Table 3]

[0028] [Table 4]

[0029] [Table 5]

[0030] The data in Table 3 show that: Comparative Example B: Without nPBr, the foam board had a lower pentane % but did not pass E84 slit profile or UL 1715 and had a relatively high halogen content. Example 1: With the proper Br emission profile, the board was able to pass the E84 slit with much lower total halogen. Example 2: With the proper Br release profile, increasing the reactive aliphatic bromine % allowed the board to pass E84 slit and UL 1715 in wall and ceiling configurations. Example 3: The synergistic effect of the FR package and silicone surfactant allowed the product to pass UL 1715 full room corner with lower total halogens compared to the control (Comparative Example A). (Aspect) (Aspect 1) A thermosetting foam, 0.2 to 4.0 wt. % of at least one aliphatic brominated polyether polyol; 2.0 to 7.0 wt. % of at least one aromatic brominated polyester polyol; 2.0 to 7.5 wt. % of at least one flame retardant comprising an organic phosphate, an organic phosphonate, or an organic phosphite; wherein the ratio of the amount of aliphatic bromine expressed as a percentage of total bromine to the amount of aromatic bromine expressed as a percentage of total bromine is from 10:90 to 50:50. (Aspect 2) 2. The foam of embodiment 1, wherein the flame retardant further comprises an oligomeric alkyl phosphate. (Aspect 3) 3. The foam of claim 2, wherein the flame retardant is a blend of triethyl phosphate and oligomeric alkyl phosphate. (Aspect 4) 4. The foam of embodiment 3, wherein the ratio of triethyl phosphate to oligomeric alkyl phosphate is from 90:10 to 50:50. (Aspect 5) 10. A composite material comprising: the foam of claim 1; and at least one face sheet attached to at least one outer surface of the foam. (Aspect 6) 6. The composite of claim 5, wherein the face sheet comprises resin-impregnated fiber, plastic, wood, or metal. (Aspect 7) 7. The composite material of embodiment 6, wherein the metal is aluminum.

Claims

1. A thermoset polyurethane foam made from a formulation comprising at least one isocyanate, at least one bromine-free polyol, at least one aliphatic brominated polyether polyol, and at least one aromatic brominated polyester polyol; The formulation comprises: 0.2 to 4.0 wt. % of at least one aliphatic brominated polyether polyol; 2.0 to 7.0 wt. % of at least one aromatic brominated polyester polyol; 2.0 to 7.5 wt. % of at least one flame retardant comprising an organic phosphate, an organic phosphonate, or an organic phosphite; wherein the ratio of the amount of aliphatic bromine expressed as a percentage of total bromine to the amount of aromatic bromine expressed as a percentage of total bromine is from 10:90 to 50:50; The thermoset polyurethane foam, in its core, surface treatment, and slit configuration, passes an ASTM E84 or UL 723 tunnel burn test; The thermoset polyurethane foam has a total bromine content of greater than or equal to 1.58% and less than or equal to 2.39%, based on the total weight of the formulation.

2. 10. The foam of claim 1, wherein the organic phosphate comprises an oligomeric alkyl phosphate.

3. 3. The foam of claim 2, wherein the flame retardant is a blend of triethyl phosphate and an oligomeric alkyl phosphate.

4. 4. The foam of claim 3, wherein the ratio of triethyl phosphate to oligomeric alkyl phosphate is from 90:10 to 50:

50.

5. 10. A composite material comprising the foam of claim 1 and at least one face sheet attached to at least one outer surface of said foam.

6. 6. The composite material of claim 5, wherein the face sheet comprises resin-impregnated fabric, plastic, wood, or metal.

7. 7. The composite material of claim 6, wherein the metal is aluminum.

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