FLAME RETARDANT POLYISOCYANURATE FOAM

Abstract

An object of the present invention is to provide a polyisocyanurate foam having excellent flame retardancy and a heat insulator and building material comprising the same. A flame retardant polyisocyanurate foam produced by curing a mixture comprising a polyol (A), a surfactant (B), a catalyst (C), a blowing agent (D), a polyisocyanate (E) and a flame retardant (F), wherein the catalyst (C) comprises a trimerization catalyst; the water content in the blowing agent (D) is less than 0.2 parts by mass based on 100 parts by mass of the total of the polyol (A) and the polyisocyanate (E); the flame retardant (F) comprises a red phosphorus-based flame retardant and aluminum hydroxide, and the volume average diameter of the aluminum hydroxide is not less than 40 m when measured by laser diffractometry; the total content of the red phosporus-based flame retardant and the aluminum hydroxide is 6 to 36 parts by mass based on 100 parts by mass of the total of the polyol (A) and the polyisocyanate (E); and the equivalent ratio of an isocyanate group in the polyisocyanate (E) to the total active hydrogen groups contained in the polyol (A), the surfactant (B), the catalyst (C) and the blowing agent (D) (NCO/OH ratio) is more than 2.0.

Claims

1. A flame retardant polyisocyanurate foam, comprising a cured reaction product of a raw material mixture comprising a polyol (A), a surfactant (B), a catalyst (C), a blowing agent (D), a polyisocyanate (E) and a flame retardant (F), wherein: the catalyst (C) comprises a trimerization catalyst; the blowing agent (D) has a water content of less than 0.2 parts by mass based on 100 parts by mass of the total of the polyol (A) and the polyisocyanate (E); the flame retardant (F) comprises a red phosphorus-based flame retardant and aluminum hydroxide, and the volume average diameter of the aluminum hydroxide is not less than 40 m when measured by laser diffractometry; the total content of the red phosphorus-based flame retardant and the aluminum hydroxide is 6 to 36 parts by mass based on 100 parts by mass of the total of the polyol (A) and the polyisocyanate (E); and the equivalent ratio of an isocyanate group in the polyisocyanate (E) to the total active hydrogen groups contained in the polyol (A), the surfactant (B), the catalyst (C) and the blowing agent (D) is more than 2.0.

2. The flame retardant polyisocyanurate foam according to claim 1, wherein the mass ratio of the red phosphorus-based flame retardant to the aluminum hydroxide is 1:1 to 1:4.

3. The flame retardant polyisocyanurate foam according to claim 1, wherein the polyol (A) comprises a polyester polyol having a functionality of 2 to 3 and a Hydroxyl Number of 100 to 400 mg KOH/g.

4. The flame retardant polyisocyanurate foam according to claim 1, wherein the polyol (A) comprises a polyester polyol having an aromatic ring content of 8% to 30% by mass.

5. The flame retardant polyisocyanurate foam according to claim 1, wherein the polyisocyanate (E) comprises an aromatic polyisocyanate, a modified aromatic polyisocyanate, or a combination thereof.

6. The flame retardant polyisocyanurate foam according to claim 1, wherein the blowing agent (D) comprises a hydrofluoroolefin, a hydrochlorofluoroolefin, water, hydrocarbon, or a combination of any two or more thereof.

7. The flame retardant polyisocyanurate foam according to claim 1, wherein the blowing agent (D) comprises trans-1-chloro-3,3,3-trifluoropropene.

8. The flame retardant polyisocyanurate foam according to claim 1, wherein the foam has a core density of 30 to 80 kg/m.sup.3.

9. The flame retardant polyisocyanurate foam according to claim 1, wherein the total heat released from the foam is not more than 8 MJ/m.sup.2 when measured by the non-combustibility test based on ISO5660.

10. A heat insulator, comprising the flame retardant polyisocyanurate foam according to claim 1.

11. A building material, comprising the flame retardant polyisocyanurate foam according to claim 1.

Description

EXAMPLES

[0066] Hereinafter, the present invention will be specifically described in reference to examples, but the present invention is not limited to the examples below. It is noted that, in the examples, part(s) means part(s) by mass and % means % by mass, unless otherwise noted.

[0067] Unless otherwise noted, the following measurement methods are applied: [0068] The isocyanate group content according EN ISO 11909 (2007). [0069] Density according ISO 845 (2006) [0070] The viscosity according ASTM D4878-15. [0071] The Hydroxyl number according ASTM E222-17

<Production of a Polyisocyanurate Foam>

[0072] The raw materials which were used for producing the flame retardant polyisocyanurate foams of the examples and comparative examples are shown in Table 1 below. The volume average diameters of the raw materials were measured using Microtrac laser diffraction scattering type particle size analyzer MT3300EX-II manufactured by Nikkiso Co., Ltd. (Laser diffraction following ISO 13320 and Representation of results of particle size analysis following ISO 9276-1).

TABLE-US-00001 TABLE 1 Components Trade names/Compound names A Polyol 1 RLK-087 (polyester polyol, manufactured by Kawasaki Kasei Chemicals Ltd.) Functionality: 2 Hydroxyl Number: 200 mg KOH/g Viscosity: 900 mPa .Math. s (25 C.) Aromatic ring content: 8% Polyol 2 RFK-509 (polyester polyol, manufactured by Kawasaki Kasei Chemicals Ltd.) Functionality: 2 Hydroxyl Number: 200 mgKOH/g Viscosity: 16000 mPa .Math. s (25 C.) Aromatic ring content: 24% B Surfactant B8516 (manufactured by Evonik Japan Co., Ltd.) C Catalyst 1 Bis(2-dimethylaminoethyl) ether Catalyst 2 Triethylmethylammonium2-ethylhexane salt Catalyst 3 N,N-Dimethylcyclohexylamine Catalyst 4 Potassium Octanoate D Blowing agent 1 Water Blowing agent 2 Trans-1-chloro-3,3,3-trifluoropropene E Polyisocyanate Sumidur 44V20L (manufactured by Sumika Covestro Urethane Co., Ltd.) Isocyanate group content: 31.5% F Liquid flame retardant TMCPP (manufactured by Daihachi Chemical Industry Co., Ltd.) Aluminum hydroxide 1 C-301N (manufactured by Sumitomo Chemical Co, Ltd.) Volume average diameter: 1.7 m Aluminum hydroxide 2 C-305 (manufactured by Sumitomo Chemical Company, Ltd.) Volume average diameter: 7 m Aluminum hydroxide 3 B-316 (manufactured by TOMOE Engineering Co., Ltd.) Volume average diameter: 25 m Aluminum hydroxide 4 B-325 (manufactured by TOMOE Engineering Co., Ltd.) Volume average diameter: 34 m Aluminum hydroxide 5 C-31 (manufactured by Sumitomo Chemical Company, Ltd.) Volume average diameter: 55 m Aluminum hydroxide 6 SB93 (manufactured by Nippon Light Metal Company, Ltd.) Volume average diameter: 123 m Red phosphorus-based flame Nova Red 120UFA (manufactured by Rin Kagaku Kogyo Co., Ltd.) retardant Volume average diameter: 12.5 m

[0073] For each of examples and comparative examples, each component is provided based on the composition shown in Tables 2a-2c, and polyol-containing composition comprising a polyol, surfactant, catalyst and blowing agent is mixed and stirred with a polyisocyanate and flame retardant to obtain a raw material mixture. Subsequently, 200 to 250 g of each raw material mixture which has been adjusted to 201 C. was poured into a polyethylene cup at a temperature of 20 to 25 C. and mixing and stirring by hand mixing for 3 seconds at stirring speed of 5000 rpm. Each resultant stirred mixture was then transferred into a wooden box (200150150 mm), foamed and cured to obtain the polyisocyanurate foam of each examples and comparative examples. At this time, the reactivity (cream time and gel time) and the free density for each polyisocyanurate foam were measured respectively based on the procedure below.

<Measurement of the Reactivity and Free Density of Polyisocyanurate Foam>

Reactivity (Cream Time and Gel Time)

[0074] The reactivity (cream time (CT) and gel time (GT)) by hand mixing for a raw material mixture of a polyisocyanurate foam of each of the examples and comparative examples was measured as an evaluation of reactivity. Specifically, a time at which each raw material mixture of polyisocyanurate foam started to be mixed by hand mixing (Homogeneous mixing device used: T. K. Robomix F Model, manufactured by Primix Corporation; Stirring blade: diameter 50 mm, sawblade; Number of revolutionTime: 5,000 rpm3 seconds) was defined as 0 second, a time at which from the start of change in color to the start of foaming was defined as CT, and a time at which from the start of change in color to a time at which each resultant polyisocyanurate foam begins to be stringy when the polyisocyanurate foam is pricked with a disposable chopstick and the chopstick was pull out the foam was defined GT. The respective times were visually measured (average values by ten of trained panels). In the measurement of CT and GT, the amount of each raw material mixture of polyisocyanurate was 250 g, the temperature was 20 C., and the volume of polyethylene cup into which each raw material mixture of polyisocyanurate foam was placed was 500 mL. The respective results of CT and GT for each raw material mixture of polyisocyanurate foam are shown in Table 2.

Free Density

[0075] Two 505050 mm cubes were cut out using a caliper from the core portion of the resultant polyisocyanurate foam of each examples and comparative examples, the mass of each cube was measured, and the density of each polyisocyanurate foam was calculated based on the mass and volume, and the average value of two cubes was regarded as the free density in the present invention. The results are shown in Table 2.

<Production of a Polyisocyanurate Foam Moldings>

[0076] For each example and comparative example, a composition comprising a polyol, surfactant, catalyst and blowing agent was mixed and stirred with a polyisocyanate and flame retardant based on compositions shown in Table 2 to obtain a stirred mixture in the same manner as the above-mentioned production of the polyisocyanurate foam except that the temperature of the raw material mixture of polyisocyanurate was 20 C. Subsequently, each resultant stirred mixture was transferred into an aluminum panel mold (40030050 mm) which has been adjusted to 502 C., foamed and cured to produce polyisocyanurate foam moldings of each example and comparative example (demolding time: 6 minutes). The density, core density and flame retardancy (Total heat released) for each resultant polyisocyanurate foam molding were measured respectively based on the procedure below.

Density

[0077] The density for the resultant polyisocyanurate foam molding of each example and comparative example was measured based on the following calculating formula. The results are shown in Table 2.

Density=Mass of polyioscyanurate foam molding after mold removalMold volume[Math. formula 1]

Core Density

[0078] Two 505050 mm cubes were cut out using a caliper from the core portion of the resultant polyisocyanurate foam molding of each examples and comparative examples, the mass of each cube was measured, and the density of each polyisocyanurate foam molding was calculated based on the mass and volume, and the average value of two cubes was regarded as the core density in the present invention. The results are shown in Table 2.

Flame Retardancy (Total Heat Released)

[0079] The flame retardancy (Total heat released) for the resultant polyisocyanurate foam molding of each example and comparative example was measured based on ISO5660 using the following device and conditions. [0080] Device: CONE CALORIMETER C4, manufactured by Toyo Seiki Seisaku-sho, Ltd. [0081] Conditions: [0082] Heat Flux: 50 kW/m.sup.2 [0083] Sample position: 60 mm (the distance from the cone heater to a sample surface) [0084] Heating time: 20 minutes [0085] Sample size: 10010025 mm (cut out from a core) [0086] Panel aging period: 3 days (after molding) [0087] Sample aging period: 1 day (after cutting-out)

[0088] When the measured Total heat released was not more than 8 MJ/m.sup.2, it is evaluated as Significant flame retardancy is recognized (flame retardancy: ), and, when the Total heat released was more than 8 MJ/m.sup.2, it is evaluated as Significant flame retardancy is not recognized (flame retardancy: x). The results are shown in Tables 3a-3c.

TABLE-US-00002 TABLE 2-a Components of Foams C. E. 1-C. E. 7, Ex. 1-Ex. 2 Component Unit C .E. 1 C. E. 2 C. E. 3 C. E. 4 C. E. 5 C. E. 6 C. E. 7 Ex. 1 Ex. 2 A Polyol 1 Parts 19.0 19.0 19.0 19.0 19.0 19.0 19.0 19.0 19.0 Polyol 2 by 15.5 15.5 15.5 15.5 15.5 15.5 15.5 15.5 15.5 B Foam stabilizer Weight 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 C .sub.Catalyst 1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 .sub.Catalyst 2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 .sub.Catalyst 3 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 .sub.Catalyst 4 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 D Foaming agent 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Foaming agent 2 11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 E Polyisocyanate 65.5 65.5 65.5 65.5 65.5 65.5 65.5 65.5 65.5 F Liquid flame retardant 5.2 5.2 5.2 5.2 5.2 5.2 5.2 5.2 5.2 Aluminium hydroxide 1 13.8 Aluminium hydroxide 2 13.8 Aluminium hydroxide 3 13.8 Aluminium hydroxide 4 13.8 Aluminium hydroxide 5 13.8 13.8 Aluminium hydroxide 6 13.8 Red phosphorus-based 13.8 6.9 6.9 6.9 6.9 6.9 6.9 flame retardant Aluminium hydroxide m n.d 55 n.d 1.7 7 25 34 55 123 Volume average diameter Aluminium hydroxide n.d n.d n.d 2.0 2.0 2.0 2.0 2.0 2.0 Red phosphorus-based flame retardant Red phosphorus-based flame retardant + Parts by 0 13.8 13.8 20.7 20.7 20.7 20.7 20.7 20.7 Aluminium hydroxide weight Equivalent ratio (NCO/OH) 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8

TABLE-US-00003 TABLE 2-b Components of Foams C. E. 8-C. E. 9, Ex. 3-Ex. 11 Component Unit C. E. 8 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 C. E. 9 A Polyol 1 Parts 19.0 19.0 19.0 19.0 19.0 19.0 19.0 19.0 19.0 19.0 19.0 Polyol 2 per 15.5 15.5 15.5 15.5 15.5 15.5 15.5 15.5 15.5 15.5 15.5 B Foam stabilizer weight 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 C .sub.Catalyst 1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 .sub.Catalyst 2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 .sub.Catalyst 3 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 .sub.Catalyst 4 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 D Foaming agent 1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Foaming agent 2 11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 11.9 E Polyisocyanate 65.5 65.5 65.5 65.5 65.5 65.5 65.5 65.5 65.5 65.5 65.5 F Liquid flame retardant 5.2 5.2 5.2 5.2 5.2 5.2 5.2 5.2 5.2 5.2 5.2 Aluminium hydroxide 1 Aluminium hydroxide 2 Aluminium hydroxide 3 Aluminium hydroxide 4 Aluminium hydroxide 5 3.5 6.9 6.9 10.4 10.7 13.8 13.8 17.3 20.7 20.7 24.2 Aluminium hydroxide 6 Red phosphorus-based 1.7 3.5 6.9 5.2 5.4 3.5 10.4 8.6 6.9 10.4 12.1 flame retardant Aluminium hydroxide m 55 55 55 55 55 55 55 55 55 55 55 Volume average diameter Aluminium hydroxide 2.0 2.0 1.0 2.0 2.0 4.0 1.3 2.0 3.0 2.0 2.0 Red phosphorus-based flame retardant Red phosphorus-based flame retardant + Parts by 5.2 10.4 13.8 15.5 16.1 17.3 24.2 25.9 27.6 31.1 36.3 Aluminium hydroxide weight Equivalent ratio (NCO/OH) 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8

TABLE-US-00004 TABLE 2-c Components of Foams Ex. 12-Ex. 15, C.E. 10-C.E. 11 Component Unit Ex. 12 C. E. 10 Ex. 13 Ex. 1 Ex. 14 Ex. 15 C. E. 11 A Polyol 1 Parts 19.0 18.9 15.8 19.0 22.1 24.6 27.6 Polyol 2 per 15.5 15.5 13.0 15.5 18.1 20.1 22.6 B Foam stabilizer weight 1.4 1.4 1.2 1.4 1.6 1.8 2.0 C .sub.Catalyst 1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 .sub.Catalyst 2 0.2 0.2 0.1 0.2 0.2 0.2 0.2 .sub.Catalyst 3 0.1 0.1 0.1 0.1 0.1 0.1 0.1 .sub.Catalyst 4 1.0 1.0 0.9 1.0 1.2 1.2 1.2 D Foaming agent 1 0.1 0.2 0.0 0.0 0.0 0.0 0.0 Foaming agent 2 11.9 11.9 9.9 11.9 13.8 15.3 17.2 E Polyisocyanate 65.5 65.5 71.2 65.5 59.8 55.3 49.7 F Liquid flame retardant 5.2 5.2 4.3 5.2 6.0 6.7 7.5 Aluminium hydroxide 1 Aluminium hydroxide 2 Aluminium hydroxide 3 Aluminium hydroxide 4 Aluminium hydroxide 5 13.8 13.8 11.5 13.8 16.1 17.9 20.1 Aluminium hydroxide 6 Red phosphorus-based 6.9 6.9 5.6 6.9 8.0 8.9 10.1 flame retardant Aluminium hydroxide m 55 55 55 55 55 55 55 Volume average diameter Aluminium hydroxide 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Red phosphorus-based flame retardant Red phosphorus-based flame retardant + Parts by 20.7 20.7 17.1 20.7 24.1 26.8 30.2 Aluminium hydroxide weight Equivalent ratio (NCO/OH) 3.8 3.8 5.0 3.8 3.0 2.5 2.0

TABLE-US-00005 TABLE 3a Properties of Foams C.E.1-C.E. 7, Ex 1-Ex.2 Component Unit C. E. 1 C. E. 2 C. E. 3 C. E. 4 C. E. 5 C. E. 6 C. E. 7 Ex. 1 Ex.2 Reactivity Cream time sec. 6 8 8 7 7 7 7 7 7 Gel time sec. 41 47 42 48 51 50 52 49 50 Free density kg/m.sup.3 36.8 44.7 41.3 43.1 43.1 43.1 43.1 43.1 43.1 Density kg/m.sup.3 55 62 62 64 64 64 64 64 64 Core density kg/m.sup.3 49 55 55 57 57 57 57 57 58 Combustibility Gross calorific MJ/m.sup.2 24.7 15.5 8.9 23.7 15.5 10.3 8.4 5.8 3.4 value Judge

TABLE-US-00006 TABLE 3b Properties of Foams C. E. 8-C. E. 9, Ex. 3-Ex. 11 Component Unit C. E. 8 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 C. E. 9 Reactivity Cream time sec. 8 7 7 7 7 8 8 8 8 8 8 Gel time sec. 43.3 42 43 49 49 48 55 57 62 115 57 Free density kg/m.sup.3 44.3 39.2 39.5 40.8 40.8 43.8 42.4 45 48.6 45 48 Density kg/m.sup.3 kg/m.sup.3 57 62 58 58 63 66 69 66 70 65 Core density kg/m.sup.3 kg/m.sup.3 52 55 51 51 56 60 63 60 65 59 Combustibility Gross calorific MJ/m.sup.2 10.8 8.0 7.7 7.1 6.6 7.4 6.3 5.4 7.2 7.7 10.2 value Judge

TABLE-US-00007 TABLE 3-c Properties of Foams Ex. 12-Ex. 15, C. E. 10-C. E. 11 Component Unit Ex. 12 C. E. 10 Ex. 13 Ex. 1 Ex. 14 Ex. 15 C. E. 11 Reactivity Cream time sec. 7 7 7 7 7 7 7 Gel time sec. 40 33 52 49 46 45 46 Free density kg/m.sup.3 41.4 39.3 40 43.1 47.4 48.8 49.3 Density kg/m.sup.3 55 62 58 63 64 64 64 Core density kg/m.sup.3 49 55 52 57 57 57 58 Combustibility Gross calorific MJ/m.sup.2 7.2 9.3 5.7 5.8 6.9 7.9 13.8 value Judge

[0089] The results shown in Tables 3a-3c show that any Total heat released measured based on ISO5660 in Examples 1 to 15 (Ex. 1-Ex. 15) were not more than the criterion value (8 MJ/m.sup.2), so that the samples have significant flame retardancy.

[0090] On the other hand, the results shown in Tables 3a show that the Total heat released measured based on ISO5660 in Comparative example 1 (C.E. 1) in which neither red phosphorus-based flame retardant nor aluminum hydroxide were contained as a flame retardant was a result (24.7 MJ/m.sup.2) much greater than the criterion value (8 MJ/m.sup.2), so that significant flame retardancy was not recognized.

[0091] In Comparative Examples 2 and 3 in which only one of a red phosphorus-based flame retardant or aluminum hydroxide were contained as a flame retardant, any Total heat released were greater than the criterion value, so that significant flame retardancy was not recognized.

[0092] In Comparative Examples 4 to 7 in which a red phosphorus-based flame retardant and aluminum hydroxide were contained as a flame retardant, but the volume average diameter of the aluminum hydroxide was less than 40 m, any Total heat released were greater than the criterion value, so that significant flame retardancy was not recognized. It is noted that, in Examples 1 and 2, the foams were produced based on the same composition as Comparative Examples 4 to 7 except that aluminum hydroxide of which the volume average diameter was not less than 40 m was used, and that any Total heat released were not more than the criterion value, so that they are shown to have significant flame retardancy. Taking account that it was conventionally known that, when aluminum hydroxide was used as a flame retardant, as the particle diameter of aluminum hydroxide was smaller, the decomposition reaction of the aluminum hydroxide was accelerated more, so that higher flame retardant effect was exhibited, it is an unexpected result that, in Examples 1 and 2 in which aluminum hydroxide of which the particle diameter was larger was used, more significant flame retardancy was exhibited.

[0093] In Comparative Examples 8 and 9 in which the red phosphorus-based flame retardant and aluminum hydroxide were contained as a flame retardant, but the total content thereof was less than 6 parts by mass (5.2 parts by mass) in Comparative Example 8, and more than 36 parts by mass (36.3 parts by mass) in Comparative Example 9, based on 100 parts by mass of the total amount of the polyol and the polyisocyanate, any Total heat released were greater than the criterion value, so that significant flame retardancy was not recognized. It is considered that, in Comparative Example 8, sufficient flame retardancy could not be obtained because of a small absolute amount of red phosphorus-based flame retardant and aluminum hydroxide. Further, it is considered that, in Comparative Example 9, the viscosity of the polyol and isocyanate was increased as a result of the large content of the red phosphorus-based flame retardant and aluminum hydroxide, so that mixing and stirring of the raw material mixture was insufficient, whereby a trimerization reaction to form an isocyanurate structure exhibiting flame retardancy was prevented, so that sufficient flame retardancy could not be obtained.

[0094] In Comparative Example 10 in which water was contained as a blowing agent and the content of the water was not less than 0.2 parts by mass (0.2 parts by mass) based on 100 parts by mass of the total amount of the polyol and the polyisocyanate, the Total heat released was greater than the criterion value, so that significant flame retardancy was not recognized. On the other hand, in Example 12 in which the content of water as a blowing agent was 0.1 parts by mass, the Total heat released was not more than the criterion value, so that it was shown to have significant flame retardancy. It is considered that the reason is that urea in the flame retardant polyisocyanurate foam is increased by reaction of water with isocyanate, and, when the water content is large, lowers flame retardancy.

[0095] In Comparative Example 11 in which the equivalent ratio of the isocyanate group of polyisocyanate to the total active hydrogen groups contained in the polyol, the surfactant, the catalyst and the blowing agent (D) (NCO/OH ratio) is not more than 2.0, the Total heat released was greater than the criterion value, so that significant flame retardancy was not recognized. On the other hand, in Examples 1 to 15 in which the equivalent ratio is more than 2.0, the Total heat released was not more than the criterion value, so that they are shown to have significant flame retardancy. It is considered that the reason is that a trimerization reaction by trimerization catalyst proceeds sufficiently, whereby the isocyanurate structure which is advantageous to thermal resistance in the polyisocyanurate foam is increased to enhance flame retardancy.

Industrial Applicability

[0096] The flame retardant polyisocyanurate foam according to the present invention has excellent flame retardancy, so that it can be used as a building material and a heat insulator in various uses which require flame retardancy. In particular, the flame retardant polyisocyanurate foam according to the present invention can be used as a heat insulator and building material in communal buildings such as condominiums, houses, and various facilities such as schools and commercial buildings, as well as a heat insulator in plant piping systems which need flame retardancy, and automobiles and railway vehicles.