JP3239322B2 - Manufacturing method of rigid polyurethane foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for producing rigid polyurethane foams having fine open cells, using only water as a blowing agent, and the non-burnt, non-burnt, fine open cells thus obtained. It relates to a rigid polyurethane foam.

[0002]

2. Description of the Related Art Rigid polyurethane foam is a good heat insulating material and is excellent in moldability and workability. It is used in a wide range of fields, from heat insulation to storage tanks, refrigerated ships, and piping. Its thermal conductivity has been improved year by year, and it is now 0.015 at the product level.
It has reached W / mK, and is said to have the highest heat insulating performance as a heat insulating material used near room temperature. However, in view of recent energy saving problems, demands for further lowering the thermal conductivity of heat insulating materials are increasing. In order to produce such a rigid polyurethane foam, an A component mainly composed of a polyol, a catalyst, a foam stabilizer and a foaming agent is mixed and reacted with a B component mainly composed of an organic isocyanate, and a foaming process and a curing process are performed. The one-shot method of forming a foam by advancing in parallel is generally used.

[0003] As a foaming agent used for producing such a rigid polyurethane foam, there is mainly trichlorofluoromethane (R-11). However, R-
Conventional fluorocarbons represented by No. 11 were found to be chemically stable and thus diffused into the stratosphere to destroy the ozone layer. As a result, the problem that ultraviolet rays emitted from the sun reach the surface of the earth without being absorbed by the ozone layer and cause skin cancer has recently been taken up as a serious environmental problem. For this reason, the use of chlorofluorocarbon has been restricted since 1989, and R-11 for urethane foam has also been restricted.

Since the thermal conductivity of the polyurethane foam insulation cannot be smaller than the thermal conductivity of the foaming gas used, the required low thermal conductivity is realized by using an alternative to R-11. It is almost impossible to do. Therefore, in recent years, as shown in JP-A-64-4112, a vacuum heat insulating material in which a core material is covered with a metal-plastic laminated film or the like and the inside of which is reduced in pressure and sealed is attracting attention again. The core material used for the vacuum heat insulating material includes an inorganic material such as pearlite and an organic material such as rigid polyurethane foam. Inorganic materials have poor workability compared to rigid polyurethane foam,
There are drawbacks such as high density and high cost. On the other hand, in the case of rigid polyurethane foam, if the continuous foam is foamed using CFC as the blowing agent as in the past, all used CFCs will be released into the atmosphere, and a large-scale device must be installed to collect this. Is required. Therefore, if only water that reacts with an organic isocyanate to generate carbon dioxide is used as a chemical foaming agent, the internal temperature of the foam becomes 200 because there is no chlorofluorocarbon which also took away the heat of reaction by the heat of vaporization during foaming. It rises to near ° C.
Further, in the case of a communicating foam, air easily penetrates into the inside of the high-temperature foam and an oxidation reaction easily occurs. Therefore, a normal rigid polyurethane foam is carbonized in several minutes. By the way, the thermal conductivity of the above-mentioned vacuum heat insulator greatly depends on the cell diameter of the rigid polyurethane foam used as the core material. The average cell diameter of the conventional communication foam is 3
Since the thickness is in the range of 0.00 to 1000 μm, the contribution of gas heat conduction cannot be reduced sufficiently unless the pressure is reduced to 0.001 mmHg, and excellent heat insulating performance cannot be obtained. However, from the viewpoint of production efficiency, evacuating the interior of the communicating foam having an average cell diameter of about 300 to 1000 μm to 0.001 mmHg requires an extremely long evacuation time, and has a serious problem in mass productivity. Further, in a high vacuum region of 0.001 mmHg, the material is easily affected by outgassing from the material. That is, in order to achieve the required low thermal conductivity over a long period of time, a technique for reducing the cell diameter is required.

In view of the above-mentioned drawbacks of the prior art, the present inventors have conducted intensive studies on a method for producing a rigid polyurethane foam having fine open cells, and as a result, have found that a polymethylene polyphenyl isocyanate prepolymer is used. The NCO / OH equivalent ratio with the polyol is 1.3 to 3.0.
By using only water as the foaming agent at a ratio of foaming, it was found that a non-burnable rigid polyurethane foam having fine open cells could be obtained, and further studies were made based on these findings to complete the present invention. Reached.

[0006]

According to the present invention, a polyol, a polymethylene polyphenylisocyanate prepolymer, and a catalyst, a foam stabilizer, and a cell communication system are prepared at an NCO / OH equivalent ratio of 1.3 to 3.0. The present invention relates to a method for producing a rigid polyurethane foam characterized by foaming using only water as a foaming agent in the presence of an agent, and a polyurethane foam obtained in this manner.

The polyol used in the present invention has a functional group number of 2 to 8 and a hydroxyl value of 300 to 600 mg KOH /
g of the polyether polyol and the number of functional groups is 2 to 4
A polyester polyol having a hydroxyl value of 250 to 500 mgKOH / g can be used. Further, a phenolic resin having a reactive methylol group can be used. Among these polyols, particularly preferred polyols include trimethylolpropane, sorbitol, o-, m-tolylenediamine and the like. 600mg
KOH / g polyether polyol.

The polymethylene polyphenyl isocyanate prepolymer used in the present invention has a general formula

Embedded image Is obtained by reacting a polymethylene polyphenylisocyanate (hereinafter sometimes referred to as pMDI) represented by the formula (1) with a hydroxyl group-containing compound.
40-200. Examples of the hydroxyl group-containing compound used for producing the polymethylene polyphenylisocyanate prepolymer include monoalcohols and phenols having 1 functional group and a molecular weight of 32 to 300, and polyols having 2 to 3 functional groups and a molecular weight of 62 to 600. Examples thereof include monoalcohols such as methanol, ethanol, n-butanol, ethylene glycol monomethyl ether and diethylene glycol monomethyl ether; phenols such as phenol, o-, m- and p-cresol; Diols such as ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, and 1,6-hexane glycol, for example, triols such as glycerin and trimethylolpropane, methyl glucoside, sucrose, and sorbie Lumpur, other polyhydric alcohols such as dulcitol, 2-3
Examples include functional polyether polyols and polyester polyols. Examples of the above-mentioned 2- or trifunctional polyether polyol include ethylene glycol, propylene glycol, diols such as bisphenol A, glycerin, triols such as trimethylolpropane, methyl glucoside, sucrose, sorbitol,
Polyether polyols obtained by polymerizing an alkylene oxide, for example, ethylene oxide, propylene oxide, butylene oxide, alone or in combination of two or more thereof with a polyhydric alcohol such as dulcitol as an initiator. Examples of the polyester polyols include those obtained by condensation of polyols such as ethylene glycol, diethylene glycol, 1,4-butanediol, and trimethylolpropane with dicarboxylic acids such as adipic acid, succinic acid, maleic anhydride, and phthalic acid. And so on. Particularly preferred hydroxyl group-containing compounds for producing the prepolymer of the present invention include ethylene glycol monomethyl ether or polyether polyol obtained using trimethylolpropane, sucrose or bisphenol A as an initiator.
Further, two or more of the above polymethylene polyphenyl isocyanate prepolymers may be used. Further, it may be used in combination with tolylene diisocyanate or tolylene diisocyanate prepolymer.

In the present invention, the polymethylene polyphenyl isocyanate prepolymer is prepared by adding NCO /
It is used in such a range that the OH equivalent ratio is 1.3 to 3.0, preferably 1.5 to 2.5.

The catalyst used in the present invention includes, for example, 2,4,6-tris (dimethylaminomethyl) phenol, triethylamine, N, N ', N "-tris (dimethylaminopropyl) hexahydrotriazine, triethylenediamine , Diazabicycloundecene, tetramethylhexanediamine, and the like, and alkali metal salts of carboxylic acids such as potassium acetate, potassium benzoate, potassium 2-ethylhexanoate, and potassium naphthenate, for example, potassium hydroxide, hydroxide sodium,
Conventionally known isocyanuration catalysts such as strong basic metal salts such as calcium hydroxide, for example, alcoholates such as potassium phenolate and sodium methoxide, and phenolates can be used. Further, two or more kinds of the above catalysts may be used. Furthermore, you may use together with the catalyst normally used at the time of manufacturing a rigid polyurethane foam. Specific examples of such catalysts include, for example, tertiary amines such as dimethylethanolamine, triethylenediamine, tetramethylethylenediamine, tetramethylpropanediamine, tetramethylhexamethylenediamine, dimethylcyclohexylamine, such as stannasoctoate, dibutyl Conventionally known compounds such as organometallic compounds such as tindilaurate and lead octylate, and carboxylic acid salts of tertiary amines can be used, and a mixture thereof may be used. The amount of the catalyst is 0.
It is about 01 to 20% by weight.

Examples of the foam stabilizer used in the present invention include silicone surfactants such as organopolysiloxane, organopolysiloxane-polyoxyalkylene copolymer, and polyalkenylsiloxane having a polyoxyalkylene side chain, and fluorine-based surfactants. Surfactants, cationic, anionic and nonionic surfactants can also be used. Foam stabilizers are usually 0.2 to
About 10% by weight is used.

[0012] The bubble communicating agent used in the present invention may be a powdery agent such as calcium stearate, magnesium stearate, strontium stearate, zinc stearate, calcium myristate and the like as disclosed in JP-A-61-153480. Examples thereof include divalent metal salts of saturated monocarboxylic acids, and thermoplastic resin powders such as polyethylene powders described in JP-A-61-153478.
The bubble communicating agent is usually used in an amount of about 0.1 to 20% by weight based on the polyol.

In the present invention, substantially only water is used as the blowing agent. The amount of water is appropriately used depending on the required density.
It is used in an amount of about% by weight.

As a specific means for producing a rigid polyurethane foam from the above-mentioned raw materials, for example, a fine continuous mixer is prepared by mixing the raw materials using an apparatus capable of uniformly mixing the raw materials such as a small laboratory mixer or a foaming machine. A non-burnt rigid polyurethane foam having bubbles is easily obtained. The rigid polyurethane foam thus obtained is covered with a container made of a metal-plastic laminated film, and the inside thereof is decompressed to a reduced pressure and sealed as a vacuum insulation panel for an electric refrigerator, a building, a low-temperature warehouse, a storage tank,
It is advantageously used for heat insulation of refrigerated ship piping and the like.

[0015]

According to the present invention, the use of polymethylene polyphenylisocyanate prepolymer so that the NCO / OH equivalent ratio is 1.3 to 3.0 has recently been taken up as a serious environmental problem. A non-burnable rigid polyurethane foam having fine open cells can be produced without using any fluorocarbons. Further, the rigid polyurethane foam obtained by the present invention has an extremely fine cell structure as compared with the conventional rigid polyurethane foam, and also exhibits a cell communication ratio of 100%. For this reason, the foam is covered with a container made of a metal-plastic laminated film, and the inside of the vacuum insulation panel is closed under reduced pressure by using 0.1 to 0.0.
It is possible to obtain a heat insulator having excellent heat insulation performance even under a pressure of about 1 mmHg which is industrially easy to handle.

[0016]

The present invention will now be described more specifically with reference to examples and comparative examples. The raw materials used in Examples and Comparative Examples are as follows. Polyether polyol: hydroxyl value 450 mgKOH / g
Trimethylolpropane-based polyether polyol Polyester polyol: hydroxyl value 315 mg KOH / g
Polyester polyol obtained by the condensation reaction of phthalic acid with diethylene glycol Catalyst: Potassium acetate Foam stabilizer: Silicon foam stabilizer: Shin-Etsu Chemical Co., Ltd. F-
373 Blowing agent A: R-11 Blowing agent B: Water Bubble communication agent: Calcium stearate Organic polyisocyanate A: Polymethylene polyphenyl isocyanate Organic polyisocyanate B: Polymethylene polyphenyl isocyanate and propylene oxide adduct of bisphenol A Prepolymer (amine equivalent 150) Organic polyisocyanate C: Prepolymer of tolylene diisocyanate and glycerin-sucrose-propylene oxide adduct (amine equivalent 150) Organic polyisocyanate D: Prepolymer of polymethylene polyphenyl isocyanate and diethylene glycol monomethyl ether Polymer (amine equivalent 170) According to the foaming formulation shown in [Table 1], these raw materials were heated to 30 ± 1 ° C., and were reacted by high-speed mixing and stirring for 5 seconds. The foamed rigid polyurethane foam was cut the following day according to a conventional method, the burnt state (scorch) of the foam was observed, and the cell diameter was determined from an electron micrograph of the foam.

In Comparative Example 1, foaming was carried out using R-11 as a foaming agent and using polymethylene polyphenyl isocyanate such that the NCO / OH equivalent ratio became 1.1. The cell diameter is as small as 300 μm, and no scorch is seen. However, as can be seen from Comparative Example 2, the blowing agent was simply changed to R
Simply replacing water with -11 alone increases the cell diameter and also causes scorch. When the foam is isocyanurated by increasing the NCO / OH equivalent ratio as in Comparative Example 3, the heat resistance is improved and no scorch is seen, but the cell diameter does not decrease. Further, as can be seen from Comparative Example 4, even when the organic polyisocyanate was replaced with polymethylene polyphenyl isocyanate prepolymer, if the NCO / OH equivalent ratio was small, the cell diameter was small but scorch did not subside.

However, as shown in Examples 1, 2, 4, and 5, when the polymethylene polyphenyl isocyanate prepolymer is used so that the NCO / OH equivalent ratio becomes 1.3 to 3.0, the cell diameter also increases. A small foam with no scorch was obtained. Furthermore, as in Example 3, a foam having almost the same physical properties could be obtained even when a mixture of polymethylene polyphenyl isocyanate prepolymer and tolylene diisocyanate prepolymer was used as the organic polyisocyanate. However, even with the same organic polyisocyanate as in Examples 1 and 2, when the NCO / OH equivalent ratio increases to 3.5 as in Comparative Example 5, the reaction rate becomes extremely unstable, and foam breakage proceeds and disappears. It foams and does not become a rigid polyurethane foam having fine open cells.

[Table 1]

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ identification code FI C08L 75:04 C08L 75:04 (58) Field surveyed (Int.Cl. ⁷ , DB name) C08G 18/00-18/87 C08J 9/00-9/14

Claims (7)

(57) [Claims] 1. A foaming agent comprising a polyol and a polymethylene polyphenylisocyanate prepolymer in the presence of a catalyst, a foam stabilizer and a cell communicating agent at an NCO / OH equivalent ratio of 1.3 to 3.0. A method for producing a rigid polyurethane foam, characterized by foaming using substantially only water. 2. The polyol according to claim 1, wherein the polyol has 2 to 8 functional groups and a hydroxyl value of 3
2. The method according to claim 1, wherein the polyether polyol is from 00 to 600 mgKOH / g. 3. The polyol according to claim 1, wherein the polyol has 2 to 4 functional groups and a hydroxyl value of 2.
The method according to claim 1, wherein the polyester polyol is 50 to 500 mgKOH / g. 4. The method according to claim 1, wherein the polymethylene polyphenyl isocyanate prepolymer is a prepolymer having an amine equivalent of 140 to 200. 5. The blowing agent is added in an amount of about 1 to about the amount of the polyol used.
The method according to claim 1, wherein 20% by weight is used. 6. A polymethylene polyphenyl isocyanate prepolymer and a polyol having an NCO / OH equivalent ratio of 1.
2. The method according to claim 1, wherein the reaction is carried out at a rate of 5 to 2.5 to foam. 7. A foaming agent comprising a polyol, a polymethylene polyphenylisocyanate prepolymer, and an NCO / OH equivalent ratio of 1.3 to 3.0 in the presence of a catalyst, a foam stabilizer and a cell communication agent. A rigid polyurethane foam obtained by foaming using substantially only water.