JP7554325B2 - Polyisocyanurate Foam - Google Patents

Description

The present invention relates to a polyisocyanurate foam.

Various polyisocyanurate foams (rigid polyurethane foams containing isocyanurate rings) have been proposed as materials for foam boards and the like (for example, Patent Document 1 and Patent Document 2).

JP2006-321882 Patent Publication 2007-099822

Here, as described in Patent Documents 1 and 2, known methods for improving the flame retardancy of rigid polyurethane foam include including an isocyanurate ring in the structure (a method for increasing the nurate ratio) and adding a flame retardant. However, the present inventors have found that simply increasing the nurate ratio or amount of flame retardant to improve flame retardancy may ensure flame retardancy, but it is not possible to achieve high insulation properties or suitable compressive strength, friability, or dimensional stability.

Therefore, the objective of the present invention is to provide a polyisocyanurate foam that has a good balance of high thermal insulation properties, suitable compressive strength, friability, and dimensional stability while maintaining flame retardancy.

After extensive investigation, the inventors focused on the nurate ratio and closed cell ratio, and discovered that by setting each of these within a specific numerical range, it is possible to provide a polyisocyanurate foam that has a good balance of high thermal insulation properties, suitable compressive strength, friability, and dimensional stability while ensuring flame retardancy, and thus completed the present invention.

Specifically, the present invention relates to a polyisocyanurate foam obtained by mixing and reacting a polyol, a polyisocyanate, a blowing agent, and a trimerization catalyst as essential components,
The nurate ratio is 30 to 40%.
The polyisocyanurate foam is characterized in that the closed cell ratio is 75% or more.
Here, the nurate ratio may be 32 to 40%.
The nurate ratio may be 34 to 40%.
The polyisocyanurate foam may further contain a flame retardant, and the polyisocyanurate foam may contain the flame retardant in an amount of 2 to 21 mass % based on the solid content mass of the polyisocyanurate foam.
The polyisocyanurate foam may contain the flame retardant in an amount of 9 to 21 mass % based on the solid content mass of the polyisocyanurate foam.
The polyisocyanurate foam may contain the flame retardant in an amount of 9 to 17 mass % based on the solid content mass of the polyisocyanurate foam.
The foaming agent may also be a physical foaming agent.
The polyol may have an average hydroxyl value of 400 to 600 mgKOH/g.

The present invention provides a polyisocyanurate foam that has a good balance of high thermal insulation properties, suitable compressive strength, friability, and dimensional stability while maintaining flame retardancy.

FIG. 1 is an infrared absorption spectrum chart of the foamed product of Example 3.

<Polyisocyanurate foam>
The components and properties of the polyisocyanurate foam will be described in detail below. In the present specification and claims, the numerical range "X to Y" means X or more and Y or less.

<Ingredients and amount>
The polyisocyanurate foam has an isocyanurate ring in its molecular structure. The nurate ratio is 30 to 40%, preferably 32 to 40%, and more preferably 34 to 40%. The nurate ratio is measured based on infrared absorption spectroscopy, and is a value calculated by dividing the absorption peak area based on the nurate ring by the sum of the absorption peak areas based on the nurate ring, the N-H of urethane/urea, the C=O of urea, and the C=O of urethane/nurate, to thereby determine the ratio of the nurate ring to the entire partial structure (see, for example, FIG. 1).
More specifically, it is calculated as follows.
Nurate ratio (%) = [a/(a+b+c+d)] x 100
a: position of absorption peak due to nurate ring: 1410 cm ^-1 , area position: area from 1347.03 to 1464.67 cm ^-1 b: position of absorption peak due to [N-H] of urethane-urea: 1510 cm ^-1 , area position: area from 1460.81 to 1562.06 cm ^-1 c: position of absorption peak due to [C=O] of urea: 1595 cm ^-1 , area position: area from 1566.88 to 1638.23 cm ^-1 d: position of absorption peak due to [C=O] of urethane-nurate: 1710 cm ^-1 , area position: area from 1636.3 to 1768.4 cm ^-1 Here, the nurate ratio of polyisocyanurate foam is a value measured, for example, on a portion cut out to a depth of 3 mm from the surface of the polyisocyanate foam. When the nurate ratio is within the above range and the closed cell ratio is within the range described below, the polyisocyanurate foam has high heat insulation and a good balance of suitable compressive strength, friability, and dimensional stability while ensuring flame retardancy. In order to obtain this nurate ratio, the isocyanate index is preferably 150 or more.

The polyisocyanurate foam may contain a flame retardant. Examples of the flame retardant include known flame retardants, such as red phosphorus; phosphorus-based compounds such as ammonium polyphosphate, melamine phosphate, and triphenylphosphine; melamine-based compounds such as melamine cyanurate and melamine, metal hydrates such as aluminum hydroxide and magnesium hydroxide; antimony compounds such as antimony trioxide and antimony pentoxide; and phosphoric acid ester compounds such as trimethyl phosphate, triethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, cresyl diphenol phosphate, cresyl di-2,6-xylenyl phosphate, tris(dichloropropyl)phosphate, tris(chloropropyl)phosphate, and tris(tribromoneopentyl)phosphate. Among these, phosphoric acid ester compounds are preferred, and particularly preferred are tris(chloropropyl)phosphate, triethyl phosphate, and tricresyl phosphate. Here, the flame retardant is preferably contained in an amount of 2 to 21 mass %, more preferably 9 to 21 mass %, and particularly preferably 9 to 17 mass %, based on the solid mass of the polyisocyanurate foam. When the amount of the flame retardant is within the above range, the polyisocyanurate foam has a good balance of higher insulation properties, more suitable compressive strength, friability, and dimensional stability while still ensuring flame retardancy.

<Structure>
The closed cell ratio of the polyisocyanurate foam is 75% or more, preferably 80% or more, and more preferably 82.5% or more. The upper limit is not particularly limited, but is, for example, 99%. As described above, when the closed cell ratio is within the range and the nurate ratio is within the range, the polyisocyanurate foam has high heat insulation and good compression strength, friability, and dimensional stability in a well-balanced manner while ensuring flame retardancy. Here, the closed cell ratio is a value measured based on ASTM D2856.

<Method for producing polyisocyanurate foam>
A suitable polyisocyanurate foam can be produced, for example, by mixing a polyol-side foaming raw material liquid (polyol, catalyst, optional foam stabilizer, optional foaming assistant, optional flame retardant), an isocyanate component containing polyisocyanate, and a physical foaming agent. Hereinafter, the production method will be described separately for raw materials and processes (note that the flame retardant will be omitted since it has been described above). In the following description, the "polyol-side foaming raw material liquid" refers to a liquid containing a polyol, a catalyst, optional foam stabilizer, optional foaming assistant, and optional flame retardant, and the "foaming raw material composition" refers to the above-mentioned "polyol-side foaming raw material liquid" and the above-mentioned "isocyanate component" combined. Furthermore, the "solid content mass of polyisocyanurate foam" referred to in the claims and this specification is the mass of the polyisocyanate foam in a state where the foaming agent inside is completely replaced with air, and specifically, it is approximately the same as the weight of the polyisocyanate foam in a state where it is made interconnected by crushing, crushing, etc. (to a state where the closed cell ratio is 0%) and left for 16 hours or more under conditions of 23 (±5) ° C. and relative humidity of 50 (+20-10) %. In this embodiment, the solid content mass of the polyisocyanurate foam is approximately the same as the weight of the foaming raw material composition (i.e., weight of all raw materials - weight of foaming agent), and it is understood to be completely the same when water as a foaming assistant is not used.

<Ingredients>
(Polyol)
The polyol is not particularly limited as long as it is a compound having a plurality of hydroxyl groups. For example, it is preferable to use both or either of bifunctional and trifunctional polyether polyols and aromatic polyester polyols having two or more hydroxyl groups at the end or side chain obtained by condensing a polybasic acid. The preferable embodiment will be described in detail below. Examples of polyols constituting both or either of bifunctional and trifunctional polyether polyols include bifunctional polyols (ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butanediol, pentanediol, neopentyl glycol, hexanediol, cyclohexanedimethanol, bisphenol A, bisphenol F, bisphenol S, etc., or compounds obtained by addition polymerization of alkylene oxides such as ethylene oxide or propylene oxide to these, polyethylene glycol, polypropylene glycol, etc.), and trifunctional polyols (trimethylolpropane, glycerin, etc., or compounds obtained by addition polymerization of alkylene oxides to these). These may be used alone or in combination of two or more. Examples of the polybasic acid constituting the aromatic polyester polyol include orthophthalic acid, isophthalic acid, terephthalic acid, hexahydrophthalic acid, tetrahydrophthalic acid, trimellitic acid, pyromellitic acid, etc. Here, polyester polyols obtained by condensing phthalic acid with one or more of bifunctional, trifunctional or polyfunctional alcohols or their alkylene oxide adducts are preferred, and polyester polyols obtained by condensing terephthalic acid with diethylene glycol are more preferred. The content of hydroxyl groups in the aromatic polyester polyol is 2 or more, preferably 2 to 3.

Here, the average hydroxyl value of the polyol is preferably 300 mgKOH/g or more, and although there is no particular upper limit, for example, 1200 mgKOH/g. More specifically, it is particularly preferable that the average hydroxyl value of the polyol is 400 to 600 mgKOH/g. When the average hydroxyl value of the polyol is within this range, the polyisocyanurate foam has higher insulation properties and more suitable compressive strength, friability, and dimensional stability while ensuring flame retardancy. Here, the average hydroxyl value is a value measured in accordance with JIS K1557-1 (Plastics - Test methods for polyurethane raw material polyols - Part 1: Method for determining hydroxyl value).

(Physical Blowing Agent)
The physical blowing agent is not particularly limited, but is preferably a hydrocarbon (preferably C4 to C6) or a hydrofluoroolefin, specifically, cyclopentane, HFO (1336mzz), or HFO (1233zd).

(Foaming assistant)
The foaming aid is not particularly limited, but is preferably water. Although the object can be achieved by using a physical foaming agent alone, a foam having a wide range of heat insulating properties, compressive strength, friability, and dimensional stability in a well-balanced manner can be obtained even if a predetermined amount of foaming aid is added while ensuring flame retardancy. Here, when water is used in combination as a foaming aid, the number of parts of the physical foaming agent (e.g., cyclopentane) added is preferably 3.0 to 15 parts by weight per 100 parts by weight of the foaming raw material composition. The number of parts of water added is preferably 0.05 parts by weight or less based on 100 parts by weight of the foaming raw material composition. When the proportion of water is 0.05 parts by weight or less, a foam having good adhesion to a surface material and high heat insulating properties can be obtained without being brittle.

(catalyst)
The catalyst essentially contains a trimerization catalyst. A mixed catalyst of a trimerization catalyst, a resinification catalyst, and a foaming catalyst is preferred, and a mixed catalyst of a metal salt catalyst and an amine catalyst is preferred. Examples of the trimerization catalyst include: 1) metal oxides such as lithium oxide, sodium oxide, and potassium oxide; 2) alkoxides such as sodium methoxy, sodium ethoxy, sodium propoxy, sodium butoxy, potassium methoxy, potassium ethoxy, potassium propoxy, and potassium butoxy; 3) organometallic salts such as potassium acetate, potassium octylate, potassium caprylate, and iron oxalate; 4) tertiary amines such as 2,4,6-tris(dimethylaminomethyl)phenol, N,N',N"-tris(dimethylaminopropyl)hexahydrotriazine, and triethylenediamine; and 5) ethyleneimine. and 6) acetylacetone chelates and quaternary ammonium salts of alkali metals, aluminum, and transition metals. These can be used alone or in combination of two or more, and it is more preferable to use organic metal salts and quaternary ammonium salts. A combination of potassium acetate and potassium octylate is preferable. There is no particular limitation on the resinification or foaming catalyst, and those used in the production of ordinary urethane foams can be used, for example, monoamines (N,N-dimethylcyclohexylamine, N,N-dicyclohexylmethylamine, triethylamine, N, N-dimethylbenzylamine, etc.), cyclic monoamines (pyridine, N-methylmorpholine, N-ethylmorpholine, etc.), diamines (N,N,N',N'-tetramethylethylenediamine, N,N,N',N'-tetramethyl-1,3-propanediamine, N,N,N',N'-tetramethyl-1,3-butanediamine, N,N,N',N'-tetramethylhexanediamine, methylene-bis(dimethylcyclohexylamine), N,N,N',N'-tetraethylethylenediamine, etc.), triamines (N,N,N',N',N"-pentamethyldiethylenetriamine, N,N,N',N',N"-pentamethyldipropylenetriamine, 2,4,6-tris(dimethylaminomethyl)-phenol, etc.), etherdiamines (bis(2-dimethylaminoethyl)ether, 2-(N ,N-dimethylamino)ethyl-3-(N,N-dimethylamino)propyl ether, 4,4'-oxydimethylene dimorpholine, etc.), cyclic polyamines (triethylenediamine, N,N'-dimethylpiperazine, N,N'-diethylpiperazine, N,N-dimethylaminoethylmorpholine, 1-isobutyl-2-methylimidazole, 1-butoxy-2-methylimidazole, etc.), alkanolamines (N,N,N'-trimethylaminoethylethanolamine, N,N,N'-trimethylaminopropylethanolamine, 2-(2-dimethylamino-ethoxy)ethanol, N,N -dimethylaminoethanol, N,N-trimethyl-1,3-diamino-2-propanol, N-methyl-N'-(2-hydroxyethyl)-piperazine, etc.). These catalysts may be used alone or in combination of two or more.

(Other added ingredients)
When producing a polyisocyanurate foam, various additives such as a foam stabilizer, a viscosity reducer, a surface material adhesion improver, and a bubble refiner may be further used. In this case, these additives may be added when the polyol-side foaming raw material liquid and the polyisocyanate component are mixed, or may be contained in the polyol-side foaming raw material liquid in advance. As the foam stabilizer, a conventionally known nonionic surfactant, silicone surfactant, etc. may be used.

(Polyisocyanate)
The polyisocyanate is preferably an aromatic polyisocyanate compound. For example, phenylene diisocyanate, tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, dimethyldiphenylmethane diisocyanate, triphenylmethane triisocyanate, naphthalene diisocyanate, polymethylene polyphenyl polyisocyanate, etc. may be mentioned. The aromatic polyisocyanate compound may be used alone or in a mixture of two or more kinds.

<Process>
The polyisocyanurate foam is obtained by mixing the polyol-side foaming raw material liquid, the polyisocyanate component, and a physical foaming agent, followed by foaming and curing. For example, a general-purpose high-pressure foaming machine or the like is used to impinge and mix the mixture to produce a mixed liquid, which is then poured into a mold or the like of a given size to be foamed and cured. A low-pressure injection machine is used for continuous molding, and the mixture is discharged onto a belt conveyor at room temperature and atmospheric pressure to produce a flat plate, slabstock, or the like. The basic manufacturing method is as shown in Patent Document 1 and Patent Document 2. However, the following are characteristics that should be noted.

(Isocyanate Index)
When the polyol-side foaming raw material liquid and the polyisocyanate component are mixed, the isocyanate index of the mixture (foaming raw material composition) is preferably 150 to 600, more preferably 350 to 600, and even more preferably 370 to 550. When the isocyanate index is within this range, a polyisocyanate foam having a good balance of higher heat insulation and more suitable compressive strength, friability, and dimensional stability while ensuring flame retardancy. Here, the isocyanate index refers to the ratio (NCO/OH molar ratio) of the number of moles of all active hydrogens in the reaction mixture liquid, which is the total raw material blend, to the number of moles of isocyanate groups in the polyisocyanate compound. In addition, OHV in the following examples and comparative examples refers to the hydroxyl value. Here, when multiple polyols are added, the weighted average obtained by multiplying each hydroxyl value by the number of parts added of each polyol and dividing by the total number of parts added of all polyols is taken as the average hydroxyl value (average OHV).

(Viscosity of Polyisocyanate Component)
The polyisocyanate component preferably has a viscosity of 150 to 750 mPa·s at 25° C. Here, the viscosity is measured in accordance with ASTM D4889.

<Production Example>
Example 1
As the polyester polyol, 100 parts by weight of polyester polyol (OHV 400 mg KOH/g, weight average molecular weight 510) obtained by dehydration condensation of orthophthalic acid and diethylene glycol (DEG); as the polyether polyol, 14.1 parts by weight of diethylene glycol (DEG) and 2.0 parts by weight of triethylene glycol (TEG) per 100 parts by weight of polyester polyol; further, a foam stabilizer, a catalyst and a flame retardant were added to obtain a polyol-side foaming raw material liquid. The average hydroxyl value (average OHV) of the polyol (total polyol) contained in the above polyol-side foaming raw material liquid was 490 mg KOH/g.
Here, as the foam stabilizer, 0.9 mass% of Niax Silicone L-6638 (manufactured by MOMENTIVE) and 0.6 mass% of methyl carbitol (manufactured by Sankyo Chemical Co., Ltd., product name: methyl diglycol) were added based on the total mass of the foaming raw material composition. As the catalyst, 0.6 mass% and 0.3 mass% of potassium octylate and potassium acetate were added as trimerization catalysts, respectively, based on the total mass of the foaming raw material composition, and 0.3 mass% of Lubeac DMP-30 (manufactured by Nacalai Tesque) were added. Furthermore, as the flame retardant, 16 mass% of tris(1-chloro-2-propyl)phosphate (TCPP) (product name: ProFlame-PC1389, manufactured by Pro Flame) was added based on the total mass of the foaming raw material composition.
After weighing this polyol-side foaming raw material liquid, it was stirred for 1 minute with a 3000 rpm propeller stirrer. Then, to the polyol-side foaming raw material liquid adjusted to 15 ° C, an isocyanate component (Crude MDI manufactured by Tosoh Corporation, product name: MR-200) also adjusted to 15 ° C was added so that the isocyanate index was 250, and cyclopentane (product name: Marukasol FH, manufactured by Maruzen Oil Co., Ltd.) was added as a physical foaming agent to the total mass of the foaming raw material composition so that it was 6.5 mass%. These mixtures were quickly stirred for 10 seconds with a 5000 rpm propeller stirrer to obtain a stirred product. Then, the stirred product was put into a mold formwork of 300 × 300 × 20 mm equipped with aluminum surface materials on the top and bottom, and a laminate board equipped with aluminum surface materials on the top and bottom was prepared. Furthermore, the mixture was put into a box with an open top of 300×300×300 mm to prepare a foam without a facing material (hereinafter, referred to as a free foam product). The density of the foam prepared in this case was 30.7 kg/ ^m3 .

Example 2
A laminate board with aluminum surface material on the upper and lower surfaces was prepared in the same manner as in Example 1, except that 100 parts by weight of polyester polyol (OHV 323 mg KOH / g, weight average molecular weight 490) obtained by dehydration condensation of orthophthalic acid and diethylene glycol (DEG) was added as polyester polyol, 17.1 parts by weight of diethylene glycol (DEG) and 2.0 parts by weight of triethylene glycol (TEG) were added to 100 parts by weight of polyester polyol as polyether polyol, the average hydroxyl value (average OHV) of the polyol was 435 mg KOH / g, and an isocyanate component was added so that the isocyanate index was 370. In addition, the density of the free foamed product was 31.6 kg / m ³ .

Example 3
A laminate board with aluminum facings on both the top and bottom surfaces was produced in the same manner as in Example 1, except that 19.3 parts by weight of diethylene glycol (DEG) was added to 100 parts by weight of polyester polyol, the average OHV of the polyol was 518 mgKOH/g, and an isocyanate component was added so that the isocyanate index was 450. The density of the free foamed product was 34.2 kg/ ^m3 . Figure 1 is a light absorption spectrum chart of the foamed product of Example 3 (the nurate ratio was calculated from the chart).

Example 4
A laminate board with aluminum facings on the top and bottom surfaces was produced in the same manner as in Example 1, except that 20.9 parts by weight of diethylene glycol (DEG) was added per 100 parts by weight of polyester polyol, the average OHV of the polyol was 526 mg KOH/g, and an isocyanate component was added so that the isocyanate index was 500. The density of the free foamed product was 27.7 kg/ ^m3 .

Example 5
A laminate board with aluminum surface materials on the top and bottom surfaces was produced in the same manner as in Example 1, except that 24.9 parts by weight of diethylene glycol (DEG) was added per 100 parts by weight of polyester polyol, the average OHV of the polyol was 534 mgKOH/g, the amount of flame retardant added was 10% by mass, and an isocyanate component was added so that the isocyanate index was 600. The density of the free foamed product was 33.4 kg/ ^m3 .

Example 6
A laminate board with aluminum surface materials on the top and bottom surfaces was produced in the same manner as in Example 1, except that 17.2 parts by weight of diethylene glycol (DEG) was added per 100 parts by weight of polyester polyol, the average OHV of the polyol was 507 mgKOH/g, the amount of flame retardant added was 3 mass%, and an isocyanate component was added so that the isocyanate index was 450. The density of the free foamed product was 35.1 kg/ ^m3 .

(Example 7)
A laminate board with aluminum facings on the top and bottom surfaces was produced in the same manner as in Example 1, except that 20.7 parts by weight of diethylene glycol (DEG) was added per 100 parts by weight of polyester polyol, the average OHV of the polyol was 525 mgKOH/g, the amount of flame retardant added was 9 mass%, and an isocyanate component was added so that the isocyanate index was 550. The density of the free foamed product was 30.5 kg/ ^m3 .

(Example 8)
A laminate board with aluminum surface materials on the top and bottom surfaces was produced in the same manner as in Example 1, except that 18.3 parts by weight of diethylene glycol (DEG) was added per 100 parts by weight of polyester polyol, the average OHV of the polyol was 513 mgKOH/g, the amount of flame retardant added was 10% by mass, and an isocyanate component was added so that the isocyanate index was 450. The density of the free foamed product was 35.6 kg/ ^m3 .

Example 9
A laminate board with aluminum facings on the top and bottom surfaces was produced in the same manner as in Example 1, except that 20.2 parts by weight of diethylene glycol (DEG) was added per 100 parts by weight of polyester polyol, the average OHV of the polyol was 522 mgKOH/g, the amount of flame retardant added was 20% by mass, and an isocyanate component was added so that the isocyanate index was 450. The density of the free foamed product was 33.2 kg/ ^m3 .

Example 10
A laminate board with aluminum surface materials on the upper and lower surfaces was prepared in the same manner as in Example 1, except that 18.3 parts by weight of diethylene glycol (DEG) was added to 100 parts by weight of polyester polyol, the average OHV of the polyol was 513 mg KOH/g, the amount of flame retardant added was 10 mass%, Honeywell's hydrofluoroolefin product name: Soltis 1233zd (HFO) was used as a physical foaming agent, and an isocyanate component was added so that the isocyanate index was 450. The density of the free foamed product was 36.8 kg/ ^m3 .

(Example 11)
A laminate board with aluminum facings on the top and bottom surfaces was produced in the same manner as in Example 1, except that 18.05 parts by weight of diethylene glycol (DEG) was added per 100 parts by weight of polyester polyol, the average OHV of the polyol was 438 mgKOH/g, the amount of the physical foaming agent was changed, a specified amount of water was added as a foaming assistant, and an isocyanate component was added so that the isocyanate index was 450. The density of the free foamed product was 33.6 g/ ^m3 .

Example 12
A laminate board with aluminum surface materials on the upper and lower surfaces was prepared in the same manner as in Example 1, except that 100 parts by weight of polyester polyol (OHV 250 mg KOH / g, weight average molecular weight 830) obtained by dehydration condensation of terephthalic acid and diethylene glycol (DEG) was added as polyester polyol, 26.9 parts by weight of diethylene glycol (DEG) and 2.0 parts by weight of triethylene glycol (TEG) were added to 100 parts by weight of polyester polyol as polyether polyol, the average hydroxyl value (average OHV) of the polyol was 426 mg KOH / g, and an isocyanate component was added so that the isocyanate index was 370. In addition, the density of the free foamed product was 33.2 kg / m ³ .

(Comparative Example 1)
A laminate board with aluminum surface materials on the top and bottom surfaces was produced in the same manner as in Example 1, except that 109.4 parts by weight of diethylene glycol (DEG) was added per 100 parts by weight of polyester polyol, the average OHV of the polyol was 743 mgKOH/g, the amount of the physical foaming agent was changed, a specified amount of water was added as a foaming assistant, and an isocyanate component was added so that the isocyanate index was 450. The density of the free foamed product was 36.1 kg/ ^m3 .

(Comparative Example 2)
A laminate board with aluminum facings on the top and bottom surfaces was produced in the same manner as in Example 1, except that 13.0 parts by weight of diethylene glycol (DEG) was added per 100 parts by weight of polyester polyol, the average OHV of the polyol was 483 mgKOH/g, and an isocyanate component was added so that the isocyanate index was 200. The density of the free foamed product was 36.8 kg/ ^m3 .

(Comparative Example 3)
A laminate board with aluminum facings on the top and bottom surfaces was produced in the same manner as in Example 1, except that 27.2 parts by weight of diethylene glycol (DEG) was added per 100 parts by weight of polyester polyol, a polyol with an average OHV of 551 mgKOH/g was used, and an isocyanate component was added so that the isocyanate index was 650. The density of the free foamed product was 31.2 kg/ ^m3 .

Evaluation
(Oxygen Index)
Samples were taken from the free foamed product, and the oxygen index was measured based on JIS K7201-2. Specifically, the test was performed in a transparent column where a mixture of oxygen and nitrogen gas flows upward in a laminar flow, and a flame was placed in contact with the top of the test piece for up to 30 seconds to confirm whether the test piece was burning or not. The combustion behavior was judged based on the combustion time after ignition and the combustion length. In this case, the shape of the test piece was type II, so the combustion time was 180 seconds, and the combustion length was 50 mm below the top of the test piece. The presence/absence of combustion behavior was measured in increments of 0.1% oxygen concentration, and the minimum oxygen concentration (= oxygen index) that maintained combustion was determined by the up-and-down method.

(Thermal Conductivity)
A sample was taken from the laminate board, and the thermal conductivity was measured in accordance with JIS A9521.

(Compressive strength)
A sample was taken from the free foamed product, and the compressive strength was measured in accordance with JIS A 9521. Specifically, a sample cut to 100 × 100 × 20 mm was placed between the center of two pressure plates of a testing machine, and the test piece was compressed at a speed of 2 mm/min. The maximum force at which the compressive deformation rate reached 10% was taken as the compressive strength.

(Flyability)
The friability was measured based on ASTM-C-421-61 by taking samples from the free foamed product. Specifically, the weight of 12 samples cut to 25 x 25 x 25 mm was measured, and they were placed in a measuring device together with 24 pieces of wood (19 ± 0.8 mm), and after 600 revolutions, the shaved powder was removed and the weight after the test was measured. The weight reduction from the original weight was calculated as a percentage, and this was taken as the friability (= weight reduction rate).

(Dimensional stability)
A sample of 100 x 100 x 20 mm was taken from the free foam product and cut out, the dimensions of which were measured, and after leaving it to stand in a room at 23±3° C. for 24 hours, the dimensions were measured again, and the rate of change in dimensions was calculated.

Evaluation Criteria
The evaluation criteria for each item are shown below. The order of evaluation is AA>A>B>C>D. Here, evaluation D is not practical and is unsuitable for use as a product.

(Oxygen Index)
29% or more AA
27% or more but less than 29% A
24% or more but less than 27% B
22% or more but less than 24% C
Less than 22% D

(Thermal Conductivity)
Less than 21mW/m・K A
21mW/m・K or more and less than 22mW/m・K B
22mW/m・K or more and less than 23mW/m・K C
23mW/m・K or more D

(Compressive strength)
15N/ ^cm2 or more A
8N/cm2 or ^more and less than 15N/ ^cm2 C

(Flyability)
65% or less A
Over 65% C

(Dimensional stability)
Less than 3.0% A
3.0% or more C

Table 1 (Table 1A and Table 1B) shows the compounding composition, nurate ratio, closed cell ratio, and the above-mentioned evaluation items (oxygen index, thermal conductivity, compressive strength, friability, dimensional stability) of each Example and Comparative Example. Here, the overall evaluation is 4 points for AA, 3 points for A, 2 points for B, and 1 point for C, and is the total score of oxygen index x 3 + thermal conductivity x 3 + compressive strength + friability + dimensional stability. If even one item is rated D, it is deemed to be a defective product.

Claims (3)

The oxygen index (JIS K7201-2) is 24% or more, the thermal conductivity (JIS A9521) is less than 23 mW/m K, the compressive strength (JIS A9521) is 15 N/cm2 or more, and the friability (ASTM-C-421-61) is 65% or less;
A polyisocyanurate foam satisfying at least one of the following (A) to (F):
(A) The closed cell rate is 75% or more and 87.3% or less.
(B) A bifunctional or trifunctional polyether polyol and an aromatic polyester polyol are used in combination as raw materials.
(C) The isocyanate index of the raw material is 500 to 600.
(D) The raw material contains hydrofluoroolefin
(E) The raw material does not contain water
(F) The raw material does not contain layered silicate treated with a quaternary ammonium salt. 2. The polyisocyanurate foam of claim 1, having a dimensional stability of 3.2% or less.
<Measurement of dimensional stability>
A sample was taken from the free foam product and cut to 100 x 100 x 20 mm, the dimensions of which were measured, and after leaving it to stand in a room at 23±3° C. for 24 hours, the dimensions were measured again and the rate of change in dimensions was calculated. A foam board comprising the polyisocyanurate foam according to claim 1 or 2.

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