JPH07109324A - Production of rigid polyurethane foam - Google Patents

Abstract

PURPOSE:To obtain a rigid polyurethane foam excellent in dimensional stability and useful as a heat insulating material, etc., for refrigerators by reacting a specific polyether polyol with a polyisocyanate in the presence of a foaming agent. CONSTITUTION:This rigid polyurethane foam is obtained by reacting (A) a polyether polyol obtained by reacting (i) a polyol having 2-8 hydroxyl groups in the molecule with (ii) a monoepoxy-monohalogen organic compound such as an epihalohydrin in a ratio of the component (ii) of 0.02-0.5mol based on 1 equivalent hydroxyl group of the component (i) in the presence of an alkali metal compound with (B) a polyisocyanate such as 1,4-phenylenediisocyanate in the presence of (C) a foaming agent such as a hydrogen atom-containing halogenated hydrocarbon and/or water.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing rigid polyurethane foam. More specifically, it relates to a method for producing a rigid polyurethane foam having excellent dimensional stability.

[0002]

2. Description of the Related Art Rigid polyurethane foams, which use trichloromonofluoromethane (CFC-11) as a foaming agent, have excellent dimensional stability and heat insulating properties, and are widely used as heat insulating materials for refrigerators, freezers, constructions, etc. It is used. However, in recent years, to protect the earth's ozone layer,
Regulations on halogenated hydrocarbon blowing agents that do not contain hydrogen atoms have started. CFC-11 is included in this regulation target, and the foaming agent for rigid urethane foam is shifting to hydrogen atom-containing halogen hydrocarbons or water having a small ozone depletion potential. However, since these newly used foaming agents have hydrogen atoms in the molecule, they have a higher solubility and swelling in the generated urethane resin component than the current CFC-11. Therefore, the obtained foam has a problem that the strength is lowered and the dimensional stability is particularly poor and the foam tends to shrink.

On the other hand, a method of using an alkylene oxide adduct of an aromatic ring-containing aliphatic diamine as a polyol which is difficult to shrink when foamed with a hydrogen atom-containing halogen hydrocarbon type foaming agent (Japanese Patent Laid-Open No. 4-148827, etc.). Proposed, but not sufficiently effective. That is, such an alkylene oxide adduct has a reduced viscosity with an increase in the number of moles of alkylene oxide added, and the workability during the production of polyurethane foam is easy, but if alkylene oxide is added excessively, it becomes a urethane foam. In this case, the dimensional stability is not improved. Conversely, if the number of moles of alkylene oxide added is reduced,
Because it becomes a solid or very viscous liquid even at room temperature,
It becomes practically difficult to use as a polyol component. In particular, this tendency becomes more remarkable as the number of used parts of water as the foaming agent increases. As described above, when a hydrogen atom-containing halogenated hydrocarbon or water is used as a foaming agent, no polyol has been found that can obtain the same dimensional stability as when using conventional CFC-11.

[0004]

The object of the present invention is to produce a rigid polyurethane foam using a hydrogen atom-containing halogenated hydrocarbon or water as a foaming agent, and to obtain dimensional stability when using conventional CFC-11. It is to provide a method for producing a rigid polyurethane foam having the same properties.

[0005]

Means for Solving the Invention As a result of repeated studies on a method for producing a rigid polyurethane foam having low viscosity, good workability and excellent dimensional stability, as a raw material for the rigid polyurethane foam, the present inventors have found that The present invention was found to solve the above problems by using a polyol having the structure of, and has reached the present invention.

That is, the present invention is a method for producing a rigid polyurethane foam by reacting a polyol (I) with a polyisocyanate (II) in the presence of a foaming agent (III). The method for producing a rigid polyurethane foam is characterized in that the polyether polyol (A) obtained by reacting the hydroxyl group-containing polyol (a) with the monoepoxy monohalogen organic compound (b) is used.

The polyether polyol (A) used as an essential component of the polyol (I) of the present invention comprises a polyol (a) having 2 to 8 hydroxyl groups in the molecule and a monoepoxy monohalogenated organic compound (b). Is a reaction product of. That is, the epoxy group of the monoepoxy monohalogenated organic compound (b) is added to the hydroxyl group of the polyol (a) to generate an ether group and a new hydroxyl group, and (a)
And the halogen group of (b) also undergoes a condensation reaction to form an ether group. As a result, the polyether polyol (A) having a structure in which (a) is linked with (b) is finally obtained. For example, the terminal structure of (A) when epihalohydrin is used as (b) can be represented by the following formula (1). [Wherein R is the residue of the polyol (a) and N is 1 of (a)]
Indicates the number of hydroxyl groups per molecule. ]

The polyol (a) having 2 to 8 hydroxyl groups in the molecule constituting (A) includes polyhydric alcohols, bisphenols, oligomers having two or more hydroxyl groups; and polyhydric alcohols and bisphenols. Kind,
Examples thereof include compounds obtained by adding an alkylene oxide to an active hydrogen compound such as an aliphatic amine and an aromatic amine.

Specific examples of the polyhydric alcohol include aliphatic and alicyclic dihydric alcohols (ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol). , Cyclohexylene glycol, etc.), trivalent alcohols (glycerin, trimethylolpropane, etc.), and tetravalent or higher alcohols (pentaerythritol, methylglycoside, diglycerin, sorbitol, glucose, sucrose, etc.).
Preferred of these are diethylene glycol,
Glycerin, pentaerythritol, sorbitol and sucrose.

Specific examples of the above bisphenols include:
Examples include bisphenol A, bisphenol F, bisphenol S, 4,4'-dihydroxybiphenyl, and 2,2'-bis (4-hydroxyphenyl) hexafluoropropane. Of these, preferred are bisphenol A and bisphenol F.

As the polyol (a) of the present invention, in addition to the above-mentioned ones, oligomers having two or more hydroxyl groups can be used. Examples of the oligomers include polyester polyol, polycarbonate polyol, polycaprolactone polyol and the like. To be Examples of the polyester polyols include condensed polyester polyols made from polycarboxylic acids and polyols.
Examples of the polycarboxylic acid include adipic acid, phthalic anhydride, terephthalic acid, trimellitic acid, and pyromellitic acid. Of these, preferred are phthalic anhydride and terephthalic acid. Examples of the polyol include those having 2 to 8 hydroxyl groups in one molecule exemplified in the section of the polyhydric alcohol. Of these, the preferred ones are 1,4-butanediol, ethylene glycol and diethylene glycol. Specific examples of the polyester polyol include poly (1,4-butanediol terephthalate) and poly (diethylene glycol).
Examples thereof include terephthalate. Of these, particularly preferred is poly (ethylene glycol) terephthalate.

Specific examples of the aliphatic amine include monoethanolamine, diethanolamine, triethanolamine, ethylenediamine, and diethylenetriamine. Of these, preferred are triethanolamine and ethylenediamine.

Specific examples of the aromatic amine include 2,
4- and 2,6-diaminotoluene (TDA), crude TDA, 1,2-, 1,3- and 1,4-phenylenediamine, diethyltolylenediamine, 1,2-, 1,
3- and 1,4-xylylenediamine, 2,4'- and 4,4'-diaminodiphenylmethane (MDA),
Crude MDA, naphthylene-1,5-diamine, and 3,
3'-dichloro-4,4'-diaminodiphenylmethane etc. are mentioned. Preferred of these is TD
A, xylylenediamine and MDA.

As the alkylene oxide added to these active hydrogen compounds, ethylene oxide (hereinafter referred to as E
O), propylene oxide (hereinafter abbreviated as PO), butylene oxide, and combinations thereof (block and / or random addition). Of these, PO, EO and combinations thereof are preferable. The addition mole number of alkylene oxide is usually 1 to 5
It is 0 mol, preferably 2 to 40 mol.

The monoepoxy monohalogen organic compound (b) in the production of (A) is an organic compound having one epoxy group and one halogen atom in the molecule. Examples of the (b) include those in which one hydrogen atom in an aliphatic or alicyclic organic compound containing an epoxy group is substituted with a halogen atom, and specifically, epichlorohydrin, epi Examples include epihalohydrin such as bromohydrin, 3,4-epoxychlorobutane, 2,3-epoxychlorobutane, 5-chloromethyl-1,2-oxocyclohexene, and the like. Of these, preferred is epihalohydrin, and particularly preferred is epichlorohydrin.

The method for producing (A) in the present invention is exemplified. First, the alkali metal compound (c) is added to the polyol (a), and the temperature is raised with stirring. Then, a monoepoxy monohalogen organic compound (b) is added and reacted. The salt produced from this reaction product is removed to obtain a polyether polyol (A).

As the above-mentioned alkali metal compound (c),
For example, caustic (sodium hydroxide, potassium hydroxide, etc.), metal alcoholates of lower alcohols (sodium methylate, sodium ethylate, potassium tertiary butoxide, etc.), alkali metals (metal sodium, metal potassium, etc.) and alkali metal hydrides. (Sodium hydride, potassium hydride and the like). Of these, preferred is caustic, and particularly preferred are sodium hydroxide and potassium hydroxide.

The amount of (b) used is usually 1% of the hydroxyl group of (a).
The amount is such that the number of moles of (b) per equivalent is 0.02 to 0.5, preferably 0.05 to 0.30. When the molar ratio of (b) exceeds 0.5, the obtained polyether polyol (A) has gelation or extremely high viscosity, which makes it difficult to handle when it is used as a resin raw material. On the other hand, when the molar ratio of (b) is less than 0.02, the average number of hydroxyl groups in one molecule of the obtained polyether polyol (A) [gel permeation chromatography (GP
Number average molecular weight (Mn) and hydroxyl value (OHV) according to C)
Then, the value calculated by OHV × Mn ÷ 56,100]
Is less than 10, and the dimensional stability is not improved when a rigid urethane foam is used. Further, when the average number of hydroxyl groups exceeds 50, the viscosity sharply rises and becomes a very viscous liquid at room temperature, which makes it difficult to dissolve in a hydrogen atom-containing halogenated hydrocarbon-based blowing agent, and practically a polyol. It becomes difficult to use as an ingredient.

The amount of (c) used is usually (c) / (b) =
It is used in a molar ratio of 1 to 10, preferably (c) / (b) = 1 to 4. When the molar ratio of (c) / (b) is less than 1,
If the reaction between (a) and (b) does not proceed sufficiently and exceeds 10, the excess amount of alkali used in the reaction increases, and the excess is not only wasteful, but also the labor for removing excess alkali after the reaction is required. It becomes complicated.

The viscosity of the polyether polyol (A) in the present invention (value measured with a B type viscometer) is usually 2
It is 5 to 10,000 poise at 5 ° C. (A), (b)
When (c) and (c) are reacted in the above-mentioned use ratio, 2
It is possible to obtain (A) of 5 to 10,000 poise at 5 ° C. The lower the viscosity of (A) in use, the better,
When the viscosity at 25 ° C. exceeds 10,000 poise, handling becomes very difficult.

The reaction temperature in the production of (A) is usually 4
The temperature is 0 to 150 ° C, preferably 60 to 120 ° C. 40
When the temperature is lower than 0 ° C, the viscosity of the reaction system is high and it is difficult to form a homogeneous mixture system, and the reaction takes a long time. Further, if it exceeds 150 ° C., the ether bond of the polyether polyol (A) formed is easily decomposed, which is not suitable.

In the production of (A), the reaction can be promoted by further using a catalyst. Examples of catalysts that can be used for this purpose include quaternary ammonium compounds, quaternary phosphonium compounds, and metal-based catalysts. Of these, quaternary ammonium compounds are preferable, and specifically, benzyltrimethylammonium chloride, tri-n-octylmethylammonium chloride, tetrabutylammonium bromide, tetra-
Examples thereof include n-butylammonium sulfate and tetraethylammonium hydroxide.

In the production of (A), a solvent can be used if necessary. Suitable solvents are those having no active hydrogen or halogen atom such as ethers, aliphatic hydrocarbons and aromatic hydrocarbons.

In the present invention, a polyol obtained by further adding an alkylene oxide to (A) can also be used. Further, when a polyol to which alkylene oxide is added is used as the polyol component (I), the viscosity is lowered and the compatibility with the hydrogen atom-containing halogenated hydrocarbon blowing agent is improved. The alkylene oxide added to (A) may be the same type as the alkylene oxide added to (a) above, preferably PO, EO and a combination thereof. In this case, the number of moles of alkylene oxide added is usually 1 to 50 moles, preferably 2 to 4 moles.
It is 0 mol. If the number of added moles exceeds 50 moles, the compatibility with the hydrogen atom-containing halogenated hydrocarbon-based foaming agent becomes too good, and the dimensional stability becomes insufficient. The molecular weight of the polyether polyol (A) calculated from the hydroxyl value of the alkylene oxide adduct is usually 200 to 5000.

As the polyol component in the present invention,
Known polyols used for ordinary rigid polyurethane foams together with (A) [for example, active hydrogen compounds or alkylene oxide adducts thereof described in the above item (a), polybutadiene polyols, acrylic polyols, ethylenically unsaturated monosulfates. Polymer polyol modified with a monomer] can be used together. The amount of (A) in the polyol (I) is usually 5 to 100% by weight, preferably 10 to 100% by weight. If the amount of (A) is less than 5% by weight, the cross-linking density of the rigid urethane foam will not be high and the dimensional stability will be insufficient.

As the polyisocyanate (II) used in the present invention, those conventionally used for rigid polyurethane foams can be used. Such polyisocyanates include aromatic polyisocyanates, aliphatic polyisocyanates, alicyclic polyisocyanates,
And modified products thereof (for example, carbodiimide modification,
Allophanate modification, urea modification, buret modification,
Isocyanurate modified, oxazolidone modified, etc.), isocyanate group-terminated prepolymer, and the like.

Specific examples of aromatic polyisocyanates include 1,3- and 1,4-phenylene diisocyanate, 2,4- and / or 2,6-tolylene diisocyanate (TDI), crude TDI, diphenylmethane-2. , 4'- and / or 4,4'-diisocyanate (MDI), polymethylene polyphenylisocyanate
(Crude MDI), naphthylene-1,5-diisocyanate, triphenylmethane-4,4 ′, 4 ″ -triisocyanate and the like. Specific examples of the aliphatic isocyanate include isophorone diisocyanate, 1,
6-hexamethylene diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, 1,4-cyclohexyl diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate and the like can be mentioned. Specific examples of the alicyclic polyisocyanate include xylylene diisocyanate and tetramethyl xylylene diisocyanate. Specific examples of the modified polyisocyanate include carbodiimide-modified MDI and sucrose-modified T.
DI, castor oil modified MDI and the like can be mentioned. Of these, preferred are MDI, crude MDI, sucrose modified TDI and carbodiimide modified MDI.

Polyol (I) and polyisocyanate (I
The ratio of I) can be variously changed, but the equivalent ratio of the hydroxyl group of the polyol (I) and the isocyanate group of the polyisocyanate (II) is usually 1.0: (0.5 to
1.5), preferably 1.0: (0.9 to 1.2).

As the foaming agent (III) in the present invention,
A hydrogen atom-containing halogenated hydrocarbon-based blowing agent and / or water can be used. Generally, when a hydrogen atom-containing halogenated hydrocarbon-based foaming agent having a small ozone depletion coefficient is used, the resulting rigid polyurethane foam has poor dimensional stability and tends to shrink, but the polyether polyol (A) of the present invention is used. By using it, a rigid polyurethane foam having excellent dimensional stability can be produced even when a hydrogen atom-containing halogenated hydrocarbon-based blowing agent is used. As the hydrogen atom-containing halogenated hydrocarbon-based blowing agent, an HCFC type one (for example, H
CFC-123, HCFC-141b, HCFC-2
2, HCFC-142b); HFC type (eg, HFC-134a, HFC-152a, HFC-35
6) etc. are mentioned. Of these, the preferred one is
HCFC-141b, HFC-134a, HFC-35
6 and mixtures of two or more thereof. If necessary, these hydrogen atom-containing halogenated hydrocarbon-based foaming agents may be used in combination with water or low boiling point hydrocarbons. Further, water can be used alone without using the halogenated hydrocarbon-based blowing agent or the low boiling point hydrocarbons. The low boiling point hydrocarbons are usually hydrocarbons having a boiling point of 0 to 50 ° C.,
Specific examples thereof include propane, butane, pentane and mixtures thereof.

The amount of the hydrogen atom-containing halogenated hydrocarbon-based foaming agent used in the method of the present invention is such that the polyol component 10 is used.
0 to 50 parts by weight, preferably 0 to 4 parts by weight
5 parts by weight. The amount of water used is usually 0.1 to 10 parts by weight, preferably 0.5 to 100 parts by weight per 100 parts by weight of the polyol.
8 parts by weight. The amount of low boiling point hydrocarbons used is usually 0 to 40 parts by weight, preferably 0 to 30 parts by weight.

In the present invention, a catalyst usually used for polyurethane reaction, for example, an amine catalyst (triethylenediamine, N-ethylmorpholine, diethylethanolamine, 1,8-diazabicyclo (5.4.0) undecene-7, etc.) , Metal catalysts (stannous octylate, dibutyltin dilaurate, lead octylate, etc.) can be used. The amount of the catalyst is usually 0.001 to 5% by weight based on the weight of the reaction mixture.

Further, if necessary, a foam stabilizer and a coloring agent (dye,
Known additives such as pigments), plasticizers, fillers, flame retardants, antioxidants and antioxidants can also be used.

An example of the method for producing the rigid polyurethane foam is as follows. First, a predetermined amount of a polyol component, a foaming agent, a foam stabilizer, a catalyst, other additives and the like are mixed. Using a polyurethane foamer, the mixture and the polyisocyanate component are continuously and rapidly mixed at a constant ratio. The obtained mixed liquid is poured into a mold. After curing, the mold is removed to obtain a rigid polyurethane foam.

The rigid polyurethane foam obtained by the method of the present invention has good heat insulating properties and particularly excellent dimensional stability, so that it can be widely used as a heat insulating material for refrigerators, freezers, buildings and the like.

[0035]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto. "Parts" in the examples indicate parts by weight.

[Production Example of Polyol] Production Example 1 500 parts (5.43 mol) of glycerin and 217 parts (5.43 mol) of sodium hydroxide, and 1.9 parts (0.01 mol) of benzyltrimethylammonium chloride as a catalyst. Was charged into a reaction vessel, and the temperature was raised to 80 ° C. with stirring. Next, 419 parts (4.53 mol) of epichlorohydrin was added, and the mixture was reacted at 80 ° C. for about 2 hours. This reaction product was diluted with 600 parts of toluene, sodium chloride and sodium hydroxide were filtered off, and the volatile matter was removed under reduced pressure for purification. Thus, about 700 parts of a viscous brown transparent liquid polyether polyol (A-1) was obtained. The (A
-1) has substantially no epoxy group, has a hydroxyl value of 790 mgKOH / g, a viscosity of 500 poise (25 ° C),
Number average molecular weight by GPC is 850, average number of hydroxyl groups is 1
It was 2.0.

Production Example 2 260 parts of sorbitol were reacted with 740 parts of propylene oxide in the presence of a potassium hydroxide catalyst to give a number average molecular weight of 700 by GPC and a hydroxyl value of 480 mgKOH /
A polyol (B-1) having an average hydroxyl group number of 6 and a viscosity of 220 poise (25 ° C.) was obtained. 500 parts (0.71 mol) of the (B-1), 28.4 parts of sodium hydroxide (0.
71 mol) and 1.9 parts (0.01 mol) of benzyltrimethylammonium chloride as a catalyst were charged into a reaction vessel, and the temperature was raised to 80 ° C. with stirring. Next, 44.4 parts (0.48 mol) of epichlorohydrin was added, and the mixture was heated to about 2 at 80 ° C.
Reacted for hours. This reaction product was diluted with 500 parts of toluene, sodium chloride and sodium hydroxide were filtered off,
Purified by removing volatiles under reduced pressure. Thus, about 420 parts of a viscous brown transparent liquid polyether polyether (A-2) was obtained. The (A-2) has substantially no epoxy group and has a hydroxyl value of 400 mgKO.
H / g, viscosity 1,400 poise (25 ° C.), number average molecular weight by GPC was 2,300, and average number of hydroxyl groups was 16.4.

Production Example 3 360 parts of sucrose were reacted with 640 parts of propylene oxide in the presence of a trimethylamine catalyst to give a number average molecular weight of 950 by GPC and a hydroxyl value of 468 mgKOH / g.
A polyol (B-2) having an average number of functional groups of 8 and a viscosity of 310 poise (25 ° C.) was obtained. The (B-2) 500 parts (0.5
3 mol), 20 parts of sodium hydroxide (0.50 mol),
Tetrabutylammonium bromide 2.2 as a catalyst
Charge 5 parts (0.007 mol) into the reaction vessel and stir 8
The temperature was raised to 0 ° C. Then, 38.9 parts (0.42 mol) of epichlorohydrin was added, and the mixture was reacted at 80 ° C. for about 2 hours. The reaction product was diluted with 500 parts of toluene, sodium chloride and sodium hydroxide were filtered off, and the volatile matter was removed under reduced pressure for purification. Thus, about 425 parts of a viscous brown transparent liquid polyether polyol (A-3) was obtained. The (A-3) has substantially no epoxy group, a hydroxyl value of 407 mgKOH / g and a viscosity of 9
It was 200 poise (25 ° C.), the number average molecular weight by GPC was 4,820, and the average number of hydroxyl groups was 35.0.

Production Example 4 206 parts of ethylenediamine and 254 of ethylene oxide
Parts, and then 540 parts of propylene oxide were reacted in the presence of a potassium hydroxide catalyst to give a number average molecular weight of 300 by GPC, a hydroxyl value of 765 mgKOH / g and a viscosity of 53.
A polyol having an average number of hydroxyl groups of 4 and 0 poise (25 ° C.) was obtained. 500 parts (1.71 mol) of this polyol and 95.8 (1.71 mol) potassium hydroxide were charged into a reaction vessel, and the temperature was raised to 80 ° C. with stirring. Then, 118.6 parts (1.28 mol) of epichlorohydrin was added, and the mixture was added to about 2 at 80 ° C.
Reacted for hours. This reaction product was diluted with 500 parts of toluene, potassium chloride and potassium hydroxide produced as by-products were filtered off, and the volatile matter was removed under reduced pressure for purification. Thus, about 500 parts of a viscous, slightly yellow transparent liquid polyether polyol (A-4) was obtained. The (A-4) has substantially no epoxy group and a hydroxyl value of 518 mg.
KOH / g, viscosity 5,230 poise (25 ° C), GPC
The number average molecular weight is 1,340 and the average number of hydroxyl groups is 12.
It was 4.

Production Example 5 500 parts (3.68 mol) of pentaerythritol, 206 parts (3.68 mol) of potassium hydroxide and 1.5 parts (0.01 mol) of tetraethylammonium hydroxide as a catalyst were charged in a reaction vessel. The temperature was raised to 80 ° C. with stirring. Then epichlorohydrin 272.3 parts (2.94 mol)
Was added and reacted at 80 ° C. for about 2 hours. This reactant 95
After 662 parts of propylene oxide was reacted with 0 parts, the mixture was diluted with 1,000 parts of toluene, potassium chloride and potassium hydroxide were filtered off, and the volatile components were removed under reduced pressure for purification. Thus, about 1,200 parts of a viscous brown transparent liquid polyether polyol (A-5) was obtained. The (A-5) has substantially no epoxy group, has a hydroxyl value of 440 mgKOH / g and a viscosity of 3,820 poise (2
5 ° C.), the number average molecular weight by GPC was 1,800, and the average number of hydroxyl groups was 14.1.

Example 1 10 parts of (A-1) obtained in Production Example 1 and 90 parts of a polyol (B-3) having a molecular weight of 561 obtained by adding 425 parts of PO to 136 parts of pentaerythritol were added to "Silicone SH-1.
93 "(Tore Silicone Co., foam stabilizer) 1.5 parts,
2.0 parts of "U-Cat1000" (manufactured by San-Apro Co., amine catalyst) and 36 parts of HCFC-141b were pre-blended, and 152 parts of "Millionate MR-200" (manufactured by Nippon Polyurethane Co., Ltd., crude MDI) were added thereto to homogenize. Disperser (special machine stirrer) After stirring at 3000 rpm for 10 seconds, open mold [23 × 23 × 10 (height) c
m]. After completely curing, the mold was removed to obtain a rigid polyurethane foam.

Examples 2 to 8 According to the method of Example 1, rigid polyurethane foams were produced according to the blending amounts shown in Table 1.

[0043]

[Table 1]

Comparative Examples 1 to 5 Comparative Examples 1 and 2 were prepared using the polyol (B-1) prepared in Production Example 2 and were compared with those prepared using the polyol (B-2) prepared in Production Example 3. Example 2 is given. Example 1
Comparative Example 4 was one in which the polyol (B-3) used in combination with the above was used alone. A polyol (B-4) having a molecular weight of 561 obtained by addition-polymerizing 425 parts of PO to 136 parts of m-xylylenediamine was used as a polyol (B-4), and was used alone as Comparative Example 5. In the same manner as in Example 1, Table 2
A rigid polyurethane foam was prepared according to the compounding amount of.

[0045]

[Table 2]

(Evaluation Method of Dimensional Change) One day after demolding, 1
A 0 cm square test sample was cut out, and the dimension [L1 (cm)] of each of length, width and height was measured. After leaving this sample in a constant temperature bath at 23 ° C for 60 days, the sample was re-sized [L2 (c
m)] was measured and the rate of dimensional change in each of length, width and height was calculated by the following calculation formula. Dimensional change rate (%) = (L1−L2) × 100 / L1 The maximum value among the dimensional change rates in the vertical, horizontal and height directions was defined as the maximum dimensional change rate. The maximum dimensional change rate of the rigid urethane foams obtained in Examples 1 to 8 is shown in Table 3, and the maximum dimensional change rate of the hard urethane foams obtained in Comparative Examples 1 to 5 is shown in Table 4.

[0047]

[Table 3] Example No | 1 2 3 4 5 6 7 8 −−−−−−−−−−−−−−−−−−−−−−−−−−−− Maximum dimensional change rate (% ) ｜ 7 4 3 5 3 4 6 7

[0048]

[Table 4] Comparative example No | 1 2 3 4 5 −−−−−−−−−−−−−−−−−−−−−−−−−− Maximum dimensional change rate (%) | 10 15 14 15 12

As is clear from Tables 3 and 4, the maximum dimensional change rates of Examples 1 to 8 are clearly smaller than the maximum dimensional change rates of Comparative Examples 1 to 5 of 10 to 15%. It shows that the stability is good.

[0050]

EFFECTS OF THE INVENTION By using the method for producing a rigid polyurethane foam of the present invention, a rigid polyurethane foam having excellent dimensional stability can be obtained even if a halogenated hydrocarbon containing water and / or hydrogen atoms is used as a blowing agent. You can The polyurethane foam obtained by the method of the present invention is extremely useful as a heat insulating material for refrigerators, freezers, buildings, and the like.

Claims (5)

[Claims] 1. A method for producing a rigid polyurethane foam by reacting a polyol (I) with a polyisocyanate (II) in the presence of a foaming agent (III), wherein 2 to 8 polyol (I) are present in the molecule. A method for producing a rigid polyurethane foam, which comprises using the polyether polyol (A) obtained by reacting the hydroxyl group-containing polyol (a) with the monoepoxy monohalogen organic compound (b). 2. The polyether polyol (A) comprises a polyol (a) having 2 to 8 hydroxyl groups in the molecule and a monoepoxy monohalogenated organic compound (b) (a).
2. The process according to claim 1, wherein the polyether polyol is obtained by reacting in the presence of the alkali metal compound (c) in a proportion of 0.02 to 0.5 mol per 1 equivalent of the hydroxyl group of. 3. The method according to claim 1, wherein a hydrogen atom-containing halogenated hydrocarbon and / or water is used as the foaming agent (III). 4. The method according to claim 1, wherein the average number of hydroxyl groups in one molecule of the polyether polyol (A) is 10 to 50. 5. The production method according to claim 1, wherein the monoepoxy monohalogen organic compound (b) is epihalohydrin.