JP3031700B2 - Polyol composition and use thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel polyoxyalkylene polyol (hereinafter, referred to as polyol) composition and use thereof.

More specifically, the present invention relates to a polyol composition having good workability during polyurethane resin production and polyurethane foaming, a polyurethane resin having excellent physical properties, a polyurethane foam, and a method for producing the same.

The polyol composition (A) obtained according to the present invention includes hydrochlorofluorocarbons (hereinafter abbreviated as HCFC).
2,2-dichloro-1,1,1-trifluoroethane (HC
FC-123), 1,1-dichloro-1-fluoroethane (HCFC
-141b), 1-chloro-1,1-difluoroethane (HCFC
-142b), 1-chloro-1,1-difluoromethane (HCFC
-22) and hydrofluorocarbons (hereinafter abbreviated as HFC), 1,1,1,2-tetrafluoroethane (HFC-134
a) and 1,1-difluoroethane (HFC-152a) can be used not only as a raw material for polyurethane that is resistant to dissolution, but also as a polyol with appropriate viscosity, Excellent dispersibility, equivalent to the conventional method using trichlorofluoromethane (CFC-11) or dichlorodifluoromethane (CFC-12), which are chlorofluorocarbons (hereinafter abbreviated as CFC) when urethane foaming. Properties and foam properties
It is extremely useful as an electric refrigerator, a freezer, a heat insulating panel, a composite with other materials, a heat insulating material for ships or vehicles, or a heat insulating structural material.

[Conventional technology]

Currently, when producing polyurethane foam, chlorofluorocarbons such as CFC-11 and CFC-
Although 12 are used, they are taken up as environmental destructive substances that decompose the ozone layer and increase the greenhouse effect, and their production and use are regulated. At the same time
HCFC-123 and HCFC as substitutes for CFC-11 and CFC-12
-141b, HCFC-142b, HCFC-22, HFC-134a and HFC-152a
However, these foaming agents have a higher dissolving power for polyurethane resin than CFC-11 and CFC-12, and significantly reduce the properties of polyurethane foam, such as a decrease in closed cell ratio and deterioration of foam strength. I found that there was a tendency. In particular, the heat insulating effect, which is a characteristic of the rigid polyurethane foam, is significantly reduced because the foaming agent dissolves the closed cell walls in the foam during foaming.

Therefore, the necessity of a new polyurethane resin or polyurethane foam has emerged. Among the polyols as raw materials for conventional polyurethane resins, 2- (p-
There is no example in which an alkylene oxide is added to (aminophenyl) -2- (p-hydroxyphenyl) propane for use.

In general, the viscosity of a polyol decreases with an increase in the amount of alkylene oxide added, and the operation of producing a polyurethane resin is easy.However, excessive addition of an alkylene oxide causes the polyurethane resin to dissolve in HCFC and HFC. There was a tendency to be virtually unusable.
Conversely, when the added amount of the alkylene oxide is reduced, the polyol becomes solid or excessively viscous, so that the handling becomes extremely difficult.

When trying to maintain the dissolution resistance of the polyurethane resin to HCFC and HFC as described above, the workability when urethane foaming becomes extremely poor, the workability during foaming has a good viscosity, and the HFCF and No polyol having excellent dispersibility in HFC has been found.

[Problems to be solved by the invention]

The object of the present invention is particularly good workability in the production of rigid polyurethane foam, even when using HCFC or HFC having strong resin dissolving power as a foaming agent, the foam properties are equivalent to those using conventional CFC. An object of the present invention is to provide a rigid polyurethane foam having excellent dissolution resistance to HCFCF and HFC.

[Means for solving the problem]

The present inventors have conducted intensive studies to achieve the above object, and have reached the present invention.

 That is, the present invention is as follows (1) to (4).

(1) A polyol component (a) obtained by adding 1.0 to 4.5 mol of an alkylene oxide per equivalent of active hydrogen of 2- (p-aminophenyl) -2- (p-hydroxyphenyl) propane, and an aliphatic polyhydroxyl. A polyol composition comprising a polyol component (b) obtained by adding 0.5 to 6.5 mol of an alkylene oxide per equivalent of active hydrogen of a compound, or 0.5 to 3.0 mol of an alkylene oxide per equivalent of active hydrogen of an alkanolamine. Object (A).

(2) A polyurethane resin obtained by mixing and reacting a polyol in which all or a part of the polyol composition (A) according to 1 is mixed with an organic polyisocyanate.

(3) In a rigid polyurethane foam obtained by mixing and reacting an organic isocyanate, a polyol, a foaming agent, a catalyst, a foam stabilizer and other auxiliaries, the polyol composition (A) according to item 1 is used as the polyol in total. Use a polyol that is or is part of, and as the blowing agent,
A rigid polyurethane foam using a foaming agent containing at least one member selected from the group consisting of hydrochlorofluorocarbons and hydrofluorocarbons and, if necessary, a foaming aid.

(4) The method for producing a rigid polyurethane foam described in item 3.

The polyol component (a) used in the present invention is 2- (p
-Aminophenyl) -2- (p-hydroxyphenyl)
It is a polyol to which 1.0 to 4.5 mol of an alkylene oxide is added per equivalent of active hydrogen of propane (hereinafter simply referred to as AHP).

The AHP is obtained, for example, by reacting p-isopropenylphenol and aniline in the presence of a mineral acid catalyst.

Examples of the alkylene oxide used in the present invention include ethylene oxide, propylene oxide, and butylene oxide, and these can be used alone or in combination of two or more.

AHP, which is an initiator of the polyol component (a) of the present invention, in which alkylene oxide is added in an amount of less than 1.0 mol per equivalent of active hydrogen, that is, one in which a large amount of active hydrogen remains, is a foam property when a polyurethane foam is formed. Is not preferred. Further, when the alkylene oxide is added in an amount exceeding 4.5 mol, the viscosity is lowered and the mixing and dispersibility in HCFC and / or HFC is improved, but the physical properties of the foam are inferior.

Examples of the aliphatic polyhydroxy compound which is one initiator of the polyol component (b) used in the present invention include glycols having 2 to 8 functional groups, polyhydric alcohols, polysaccharides and the like. More than one species can be used in combination. Specifically, glycols include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, butanediol, neopentyl glycol, and cyclohexanetetramethanol, and polyhydric alcohols include glycerin, trimethylolethane, and trimethylolpropane. And pentaerythritol, and the polysaccharides include methyl glycoside, sorbitol, mannitol, dulcitol, and sucrose.

The alkanolamine which is another initiator of the polyol component (b) used in the present invention is represented by the following general formula (I) NR ₁ R ₁ R ₂ (I) (wherein R ₁ and R ₂ are respectively A single atom or group selected from the group consisting of a hydrogen atom, a hydroxyethyl group and a hydroxyisopropyl group, wherein R ₁ and R ₂ may be the same or different, provided that R ₁ and R ₂ are both hydrogen atoms The case is excluded.) For example, monoethanolamine,
Examples include diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine and the like.

The polyol component (b) used in the present invention contains 0.5 to 6.5 mol of alkylene oxide per equivalent of active hydrogen of the aliphatic polyhydroxy compound, or 0.5 to 6.5 mol of alkylene oxide per equivalent of active hydrogen of the alkanolamine. 3.0 mol was added. If the alkylene oxide is less than 0.5 mol per equivalent of the active hydrogen of the aliphatic polyhydroxy compound or alkanolamine, the aliphatic polyhydroxy compound or the alkanolamine retains the cross-linking property of the polyalkylene oxide or alkanolamine. Gets worse. More than 6.5 moles per equivalent of active hydrogen of aliphatic polyhydroxy compound or per equivalent of active hydrogen of alkanolamine
When the alkylene oxide is added in excess of 3.0 moles, the polymerization mixing ratio (a) / polyol component (a) /
Even if (b) exceeds 4.0 (described later), the physical properties of the polyurethane foam will deteriorate.

The polymerization mixture ratio (a) / (b) of the polyol components (a) and (b) in the present invention is preferably from 0.1 to 4.0. Weight ratio
If it exceeds 4.0, it is viscous and tends to have poor mixing and dispersibility with HCFC or HFC, and there is a problem in operation when foaming urethane, which is not preferable. On the other hand, those having a molecular weight of less than 0.1 are not preferred because the physical properties of the foam, particularly the resistance to dissolution in HCFC and HFC, are poor.

In the present invention, a catalyst used for adding an alkylene oxide to an amino group and active hydrogen of AHP, an aliphatic polyhydroxy compound and an alkanolamine is an amine compound represented by the following general formula (II) or (III): It is.

NR ₃ R ₃ R ₄ (II) R ₃ R ₄ N (CH ₂ ) _n NR ₃ R ₄ (III) (wherein R ₃ and R ₄ are each a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, And represents one atom or group selected from the group consisting of a hydroxyethyl group and a hydroxyisopropyl group, provided that R ₃ and R ₄ in formula (II) are not hydrogen atoms.

N is an integer of 1 to 6. Examples of the amine compound include dibutylamine, ethylenediamine, tetramethylenediamine, monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, triethylamine, tri-n-propylamine, di-n-propylamine, and n-amine.
Examples thereof include propylamine, n-amylamine, N, N-dimethylethanolamine, isobutylamine, isoamylamine, and methyldiethylamine.

Further, as the metal hydroxide, lithium hydroxide, sodium hydroxide, potassium hydroxide, magnesium hydroxide,
Examples thereof include calcium hydroxide and barium hydroxide. Each of the above catalysts can be used alone or in combination of two or more.

These catalysts are used in an amount of 0.1 to 2.0 parts by weight per 100 parts by weight of the above-mentioned initiator, that is, AHP, aliphatic polyhydroxy compound or alkanolamine.

As a method for producing the polyol of the present invention, AHP as an initiator, an aliphatic polyhydroxy compound, and an alkanolamine are each used alone or in an autoclave.
The seed mixture is charged, the catalyst is further charged, and then the alkylene oxide is gradually added and reacted. Reaction temperature is 90 ~
130 ° C is preferred. When the temperature is lower than 90 ° C., the reaction does not easily proceed, and when it exceeds 130 ° C., a side reaction tends to occur easily. In addition, the polyol obtained by separately charging the above-mentioned initiator is later blended in a predetermined amount.

Other polyols that can be used in combination with the polyol of the present invention include, for example, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolpropane, 1,3,6-hexanetriol, pentaerythritol, sorbitol, Sucrose, bisphenol A,
Polyhydric alcohols such as novolak, hydroxylated 1,2-polybutadiene and hydroxylated 1,4-polybutadiene, and / or hydroxyl number 20 obtained by addition-polymerizing alkylene oxide to these polyhydroxy compounds.
It is a polyether polyol of 0 to 800 mgKOH / g. In addition to the above, a hydroxyl group-containing higher fatty acid ester such as a polyester polyol obtained by reacting a higher resin acid ester polyol and a polycarboxylic acid with a low molecular weight polyol and a polyester polyol obtained by polymerizing caprolactone, a castor oil, and a dehydrated castor oil. Etc. can also be used.

The amount of other polyols that can be used in combination is 0 to 40% by weight of the total polyol.

In the present invention, as the polyurethane resin and the hard polyisocyanate, conventionally known ones are not particularly limited, and aromatic, aliphatic, alicyclic polyisocyanates and modified products thereof, for example, phenyl diisocyanate, diphenylmethane diisocyanate, Crude diphenylmethane diisocyanate, tolylene diisocyanate, crude tolylene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate,
Hydrogenated diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, triphenylmethylene triisocyanate, tolylene triisocyanate, polymethylene polyphenyl polyisocyanate, modified (carbodiimide, etc.) diphenylmethane diisocyanate and the like, and mixtures thereof An excess amount of these organic polyisocyanates and a polyol (for example, a low molecular weight polyol and / or a polymer polyol are reacted with NCO / active hydrogen (equivalent ratio) of 2 to 20 to obtain a prepolymer (NCO containing These organic polyisocyanates are used singly or in combination of two or more.The amount used is such that the equivalent ratio of the NCO group to the hydroxyl group in the stock resin solution is 0.8. To be 5.0.

If the equivalent ratio exceeds 5.0, unreacted organic polyisocyanate remains. On the other hand, when the equivalent ratio is less than 0.8, a large amount of unreacted polyol remains, so that the above range is preferable.

The blowing agent used in the present invention is HCFC and / or HFC.

As HCFC, HCFC-123, HCFC-141b, HCFC-142b, H
Examples of CFC-22 and HFC include HFC-134a and HFC-152a. These may be used alone or in combination of two or more.

If necessary, water and / or a low-boiling compound or a foaming aid containing the compound may be used in combination.

The amount of water used is usually 0.5 to 5.
0 parts by weight. The low-boiling compounds include methylene chloride, low-boiling hydrocarbons (boiling point: 10 to 50 ° C.), and mixtures thereof. Conventional chlorofluorocarbons can also be used in combination.

Examples of the foaming catalyst that can be used for obtaining the rigid polyurethane foam in the present invention include amine urethanization catalysts (triethylamine, tripropylamine, triisopropanolamine, tributylamine, trioctylamine, hexadecyldimethylamine, N- Methyl morpholine, N-ethyl morpholine, N-octadecyl morpholine, monoethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N, N-dimethylethanolamine, diethylenetriamine, N, N, N ', N'-tetramethyl Ethylenediamine, N, N, N ', N'-tetramethylpropylenediamine,
N, N, N ', N'-tetramethylbutanediamine, N, N, N',
N'-tetramethyl-1,3-butanediamine, N, N, N ',
N'-tetramethylhexamethylenediamine, bis [2
-(N, N-dimethylamino) ethyl] ether, N, N-dimethylbenzylamine, N, N-dimethylcyclohexylamine, N, N, N ', N ", N" -pentamethyldiethylenetriamine, triethylenediamine, triethylenediamine Formate and other salts of ethylenediamine, oxyalkylene adducts of amine groups of primary and secondary amines, azacyclic compounds such as N, N-dialkylpiperazines, various N, N ', N "-trialkyl Aminoalkylhexahydrotriazines (β-aminocarbonyl catalyst of JP-B-52-0443517, JP-B-53
-014279 β-aminonitrile catalyst, etc.), organometallic urethanization catalysts (tin acetate, tin octylate, tin oleate,
Tin laurate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin dichloride, lead octanoate,
Lead naphthenate, nickel naphthenate, cobalt naphthenate, etc.). These catalysts are used alone or as a mixture, and the amount used is 0.001 to 100 parts by weight of the polyol.
10.0 parts by weight.

The foam stabilizer in the present invention is a conventionally known organosilicon surfactant, for example, Nippon Unicar L-520,
L-540, L-5340, L-5410, L-5420, L-5710,
L-5720, etc. and SH-19 manufactured by Toray Silicone Co., Ltd.
0, SH-192, SH-193, SH-194, SH-195, etc.
Shin-Etsu Silicone F-305, F-306, F-317, F
-341, F-345, etc.
−4200, and so on. The amount of these foam stabilizers used is based on 100 parts by weight of the total of the polyol and the organic polyisocyanate.
0.1 to 20 parts by weight.

As a flame retardant, for example, tris (2-chloroethyl)
Phosphate, tris (dichloropropyl) phosphate, tris (dibromopropyl) phosphate, CR-505 and CR-507 manufactured by Daihachi Chemical Co., Fyro manufactured by Akzo Japan
l-6 or the like can be used.

In addition, stabilizers such as plasticizers, fillers, antioxidants, and ultraviolet absorbers, and colorants commonly used in urethane chemistry can be added as necessary.

In the case of producing the polyurethane resin of the present invention, usually, a predetermined amount of a polyol as a main raw material and an organic polyisocyanate are rapidly mixed, poured into a mold, and cured at room temperature.

In the case of producing a rigid polyurethane foam, a predetermined amount of the HCFC and / or HFC or the like as a polyol, a catalyst, a foam stabilizer, a flame retardant, other auxiliaries, and a foaming agent is mixed to obtain a resin stock solution.

As the polyol, those containing the above-mentioned polyol component (A) are used.

Using a polyurethane foaming machine, the resin stock solution and the organic polyisocyanate are continuously and rapidly mixed at a constant ratio.

The obtained rigid polyurethane foam stock solution is injected into a void or a mold. At this time, the flow rate ratio between the organic polyisocyanate and the resin stock solution is adjusted so that the equivalent ratio NCO / active hydrogen of the organic polyisocyanate and the polyol becomes 0.8 to 5.0.

After injection, the rigid polyurethane foam stock solution foams and hardens within a few minutes.

If necessary, the batch method may be used instead of the continuous method.

The rigid polyurethane foam obtained in the present invention can be used as an electric refrigerator, a heat insulating panel, a composite with other materials, a heat insulating material or a structural material for ships or vehicles, and the like.

〔Example〕

 Hereinafter, the present invention will be described with reference to examples.

(1) Polyol composition (Table 1, Table 2) The method for measuring the hydroxyl value (OH value) and the viscosity is based on JIS K155.
Followed 7

Example 1 AHP (908 g) was charged into an autoclave (2), and the autoclave was replaced with nitrogen and heated to 120 ° C. 4.8 g of triethylamine was added and mixed, and 696 g of propylene oxide was gradually charged. After reacting for 3 hours, propylene oxide in the system was removed, and a polyol component (a-1) 15 having an OH value of 420 mgKOH / g was removed.
80 g were obtained.

460 g of glycerin was charged into 2 autoclaves, and after purging with nitrogen, 3.4 g of dimethylethanolamine was added and mixed. Further, 696 g of propylene oxide was removed at 120 ° C., and the mixture was reacted for 3 hours. Unreacted propylene oxide was removed from the reaction product to obtain a polyol component (b-1) having an OH value of 727 mgKOH / g.

The propylene oxide addition number per active hydrogen of the polyol components (a-1) and (b-1) was 1.0 mol and 0.8 mol.

The polyol components (a-1) and (b-1) were mixed at a polymerization mixing ratio (a-1) / (b-1) = 4.0, and the OH value was 482 mm KO.
H / g, viscosity 15200cp / 25 ° C polyol composition (A-1)
I got

Examples 2 to 7 and Comparative Examples 1 to 2 Hereinafter, various polyol components (a-2 to a-4, b-2 to b-6) shown in Table 1 were prepared in the same manner as in Example 1, and Are mixed to obtain various polyol compositions A-2.
OH number and viscosity of these polyol compositions were measured.

 The measurement results are shown in Tables 1 and 2.

(2) Polyurethane resin (Table-3) Next, according to the formulation shown in Table-3, the polyol composition, MDI-CR (crude diphenylmethane diisocyanate,
Mitsui Toatsu Chemicals Co., Ltd.) and Kaolyzer No.1 (Amine Catalyst, Kao Co., Ltd.)) are mixed rapidly, poured into a mold, left for one day and night, and then the resin is removed from the mold and foamed. The absorption for the agent was measured.

 Table 3 shows the measurement results.

(3) Rigid polyurethane foam (1) (Table 4) In addition, the workability (miscibility of the stock solution) and the closed cell ratio of the foam during the preparation of the rigid polyurethane foam were measured by the method shown in the following production of the rigid polyurethane foam. .

 Table 4 shows the measurement results.

1.0 g of water was added to 100 g of each of the polyol compositions obtained in Examples 1 to 7 (Tables 1 and 2), and a silicone foam stabilizer L-
1.5 g of 5420 (manufactured by Nippon Yunika Co., Ltd.), 3.0 g of amine-based catalyst kaolinizer No. 1, and each of the blowing agents 3 shown in Table-4
After preparing a resin premix consisting of 1.3 g in advance, an organic polyisocyanate (Mitsui Toatsu Chemical Co., Ltd.
(MDI-CR) 112.9 g was mixed and reacted to produce a rigid polyurethane foam.

Table 4 shows the mixing dispersibility (workability) of the foaming agent and the polyol composition when preparing the resin premix. Further, the closed cell ratio of the manufactured rigid polyurethane foam was measured. The results are shown in Table-4. The same operation as in the example was performed in the comparative example.

(4) Rigid polyurethane foam (2) (Table-5) Here, a rigid polyurethane foam was produced according to the following method, and the physical properties thereof were confirmed. A resin premix was prepared from the polyol composition having the composition shown in Table 2 and the formulation shown in Table 5, and a predetermined amount of the organic polyisocyanate was rapidly mixed at 5000 rpm for 8 seconds.
Each of the vertical wooden boxes of 0 × 200 mm and 380 × 380 × 35 (thickness) mm was injected and foamed. After standing at room temperature for one day and night, a foam of 80 × 80 × 30 mm is cut out of the rigid polyurethane foam obtained from the former, and the density, compressive strength, dimensional stability at low temperature and the rigid polyurethane foam obtained from the latter are cut out according to JIS A9514. A 200 × 200 × 25 mm foam was cut out from this, and the thermal conductivity of the foam was measured in accordance with JIS A1412. The measurement results were as shown in Table-5.

 The same operation as in the example was performed for the comparative example.

[Effect of the Invention] The polyol composition (A) of the present invention has an appropriate viscosity, and has good mixing dispersibility with an organic polyisocyanate and workability. Also, the obtained polyurethane resin has high solubility resistance to HCFC or HFC with extremely low pollution, and rigid polyurethane foam using these foaming agents has the same foam physical properties as those using conventional high pollution CFC. Have.

Therefore, such polyol compositions, polyurethane resins and rigid polyurethane foams are extremely useful in the urethane industry.

Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08G 101: 00) (72) Inventor Toshio Nozawa 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Prefecture (56) References Japanese Patent Application Laid-Open No. 50-22095 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C08G 18/50 C08L 71/02

Claims (11)

(57) [Claims] (1) 2- (p-aminophenyl) -2- (p-
Per equivalent of active hydrogen of hydroxyphenyl) propane,
0.5 to 6.5 moles of alkylene oxide per equivalent of active hydrogen of polyol component (a) and aliphatic polyhydroxy compound obtained by adding 1.0 to 4.5 mol of alkylene oxide, or alkylene per equivalent of active hydrogen of alkanolamine A polyol composition (A) comprising a polyol component (b) obtained by adding 0.5 to 3.0 mol of an oxide. 2. The polyol composition (A) according to claim 1, wherein the weight mixing ratio (a) / (b) of the polyol component (a) and the polyol component (b) is 0.1 to 4.0. . 3. An alkanolamine represented by the following general formula (I):
The polyol composition (A) according to claim 1, wherein NR ₁ R ₁ R ₂ (I) (wherein, R ₁ and R ₂ each represent one atom or group selected from the group consisting of a hydrogen atom, a hydroxyethyl group, and a hydroxyisopropyl group. R ₁ and R ₂ may be the same or different, provided that R ₁ and R ₂ are both hydrogen atoms. 4. The polyol composition (A) according to claim 1.
Is obtained by mixing and reacting all or a part of a polyol with an organic polyisocyanate. 5. The polyurethane resin according to claim 4, wherein the equivalent ratio of the isocyanate group of the organic polyisocyanate to the hydroxyl group of the polyol is 0.8 to 5.0. 6. The polyurethane resin according to claim 4, wherein a part or all of the organic polyisocyanate is a prepolymer having an isocyanate group at a terminal. 7. A rigid polyurethane foam obtained by mixing and reacting an organic polyisocyanate, a polyol, a foaming agent, a catalyst, a foam stabilizer and other auxiliaries, wherein the polyol composition (A) according to claim 1 comprises: All or a part of the polyol is used, and as the foaming agent, hydrochlorofluorocarbons, a foaming agent containing at least one selected from the group consisting of hydrofluorocarbons and, if necessary, a foaming aid are used. Rigid polyurethane foam characterized by the above. 8. The method according to claim 8, wherein the hydrochlorofluorocarbon is 2,2.
2-dichloro-1,1,1-trifluoroethane, 1,1-dichloro-1-fluoroethane, 1-chloro-1,1-difluoroethane or 1-chloro-1,1-difluoromethane; hydrofluorocarbon 8. The rigid polyurethane foam according to claim 7, wherein the class is 1,1,1,2-tetrafluoroethane or 1,1-difluoroethane. 9. The rigid polyurethane foam according to claim 7, wherein the foaming aid is water and / or a low-boiling compound. 10. The rigid polyurethane foam according to claim 7, wherein a part or all of the organic polyisocyanate is a prepolymer having a terminal isocyanate group. 11. The rigid polyurethane foam according to claim 7, wherein the equivalent ratio of the isocyanate group of the organic polyisocyanate to the hydroxyl group of the polyol is 0.8 to 5.0.