JPH0751612B2 - Method for manufacturing rigid polyurethane foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyol, a polyisocyanate, a catalyst,
The present invention relates to a method for producing a rigid polyurethane foam by reacting in the presence of a foaming agent, a foam stabilizer and, if necessary, other auxiliary agents. More specifically, it relates to a method for producing a rigid polyurethane foam in which the amount of a halogenated hydrocarbon as a blowing agent is reduced by using a large amount of water as a blowing agent.

[Prior Art] Rigid polyurethane foam is usually foamed by instantaneously stirring and mixing a polyol and a polyisocyanate containing a foaming agent (a CFC compound which is a halogenated hydrocarbon and water), a catalyst, a silicon foam stabilizer, and other auxiliary agents. Is manufactured. Since the rigid polyurethane foam is lightweight and has excellent heat insulating properties, it is widely used as a heat insulating material for construction materials, boards, electric refrigerators, freezers, plants and the like that require heat insulation and cold insulation.

Rigid polyurethane foam is a urethane resin having independent cell structures, that is, closed cells, and the CFC compound and water used as a foaming agent contain CFCs having a small thermal conductivity and isocyanate in each closed cell. It exists as carbon dioxide, which has a relatively high thermal conductivity due to the reaction of water with water. Therefore, for the reason of improving the heat insulation property, a formulation using a small amount of water as a foaming agent and using a large amount of a freon compound, for example, 0 to 1.5 parts by weight of water and 35 to 60 parts by weight of a freon compound per 100 parts by weight of a polyol. Was commonly used. In addition, triethylenediamine, tetramethylhexamethylenediamine, dimethylcyclohexylamine and the like have been widely used as catalysts, and industrially useful rigid polyurethane foams have been produced.

As described above, in the conventional rigid polyurethane foam, the thermal conductivity is lowered and the heat insulating performance is improved by increasing the amount of the CFC compound used.

However, it has been pointed out that CFC compounds may lead to the depletion of the ozone layer of the earth, and worldwide CFC regulations have begun toward the abolition of CFC compounds within this century. Further, although the alternative CFC compound has a low ozone depletion coefficient, it is costly to use it in a large amount as before. That is,
Even in the field of rigid polyurethane foam, there is an urgent need to establish technology to comply with CFC regulations.

Therefore, a study is being made to reduce the amount of CFC used and instead use a large amount of water as a foaming agent. However, some technical problems arise. That is, when a large amount of water is used as a foaming agent, as described above, the amount of carbon dioxide gas instead of the amount of freon gas fills the cell, so that the freon gas concentration in the cell decreases and the thermal conductivity of the foam deteriorates. Further, the increase in the number of water parts to be blended brings about an increase in highly crystalline urea bond produced by the reaction of isocyanate with water, in addition to the usual urethane bond production reaction by the reaction of polyol and isocyanate. As a result, the brittleness of the foam, so-called flyability, deteriorates.
This deterioration of flyability tends to be particularly large when diphenylmethane-4,4'-diisocyanate and / or its polymerized isocyanate is used as the isocyanate, and also when toluene diisocyanate and / or its prepolymer is used as a mixture. . Deterioration of flyability causes many problems such as reduction in strength of the foam and adhesion between the foam and the surface material, which is a major technical problem.

Regarding the thermal conductivity, it is inevitable to some extent because the original purpose is to reduce the amount of freon. However, the deterioration of flyability is a serious problem related to the core of the product.

[Problems to be Solved by the Invention] In view of the above circumstances, the present invention solves the problem of deterioration of flyability caused by increasing the amount of water used as a foaming agent while maintaining a high thermal conductivity of a product. The present invention provides a method for producing a rigid polyurethane foam in which the amount of freon of a blowing agent is reduced.

[Means for Solving the Problems] The inventors of the present invention have focused their attention on foaming agents and catalysts in order to reduce the amount of freon in rigid polyurethane foam formulations, and have earnestly studied to develop a rigid polyurethane foam having excellent physical properties. Layered.

As a result, by using an imidazole compound as a catalyst, it was found to be extremely useful for improving thermal conductivity and flyability, which becomes a problem when the amount of water blowing agent is increased, and the present invention was completed. It was

Imidazole compounds have been known as catalysts for producing polyurethanes, but in the conventional formulation in which the amount of water blowing agent is minimized and the amount of freon compounds is large, other commonly used catalysts, such as triethylenediamine and tetramethylhexadiene, are used. The catalytic activity was lower than that of methylenediamine, dimethylcyclohexylamine, etc., and no significant feature was observed, so that it was not put into practical use. However, according to the fact that we have studied, in the formulation in which the amount of freon was reduced and the amount of the water blowing agent was increased, the greatest problem was that the flyability was generated together with the deterioration of the thermal conductivity. Have been found to exhibit an extremely excellent improving effect. The improvement of this problem cannot be achieved by the catalysts other than the imidazole compound.

That is, the present invention is a method of producing a rigid polyurethane foam by reacting a polyol and a polyisocyanate in the presence of a catalyst, a foaming agent, a foam-forming agent, and other auxiliary agents, if necessary, as a foaming agent, 100 parts by weight of the polyol. 2.0 parts by weight or more of water and 35 parts by weight or less of a halogenated hydrocarbon, and at least one selected from imidazole compounds represented by the following general formula (I) as a catalyst. (In the formula, R ₁ represents an alkyl group having 1 to 4 carbon atoms, a benzyl group, a dimethylaminopropyl group or a hydroxyalkyl group having 1 to 3 carbon atoms, and R ₂ is hydrogen, an alkyl group having 1 to 4 carbon atoms. Or an allyl group or a benzyl group, R ₃
And R ₄ represents hydrogen, a methyl group or a hydroxymethyl group. ) With a foam density of 10-60 kg / m
^A method for producing a rigid polyurethane foam, which is ³ , is provided.

[Operation] Next, the present invention will be described in detail.

As the blowing agent halogenated hydrocarbon used in the present invention, known halogenated methane and halogenated ethane can be used. Of these, trichloromonofluoromethane (R-1
1) and freon compounds such as dichlorotrifluoroethane (R-123) and dichloromonofluoroethane (R-141b) are preferable. The amount of fluorocarbon used is 35 parts by weight or less, preferably 0 to 30 parts by weight, based on 100 parts by weight of the polyol. The amount of water used is 2.0 parts by weight or more, preferably 3.0 to 10.0 parts by weight, based on 100 parts by weight of the polyol. Particularly, when the amount is 3.0 parts by weight or more, the amount of CFC reduction is large and the prescription improving effect is large. On the other hand, if the content is more than 10.0 parts by weight, the flyability and the thermal conductivity are remarkably deteriorated, which is disadvantageous in the physical properties of the product. The proportions of water and chlorofluorocarbon used are not unconditionally determined, but are determined according to the desired density.

In the present invention, as the catalyst, an imidazole compound represented by the general formula (I) is used.

Among these imidazole compounds, 1-methylimidazole, 1,2-dimethylimidazole, 1- (3-dimethylaminopropyl) imidazole, 1-isobutyl-
2-Methylimidazole and 1-n-butyl-2-methylimidazole are particularly preferably used.

The amount of the amine catalyst used in the present invention is usually 0.02 to 10 parts by weight when the polyol is 100 parts by weight. In addition, a known tertiary amine catalyst and an organic carboxylic acid salt or an organic tin compound thereof which are usually used as a cocatalyst can be appropriately used as a co-catalyst as long as the catalytic function of the present invention is not lost.

The polyisocyanate used in the present invention may be any known organic polyisocyanate, for example, toluene diisocyanate, diphenylmethane-4,4'-diisocyanate, polymerized isocyanate thereof, toluene diisocyanate prepolymer, diphenylmethane-4,4-diisocyanate preisocyanate. Examples thereof include polymers and / or polyisocyanates mixed therewith, preferably diphenylmethane-4,4′-diisocyanate and its polymerized isocyanate (crude MDI), or crude MDI and toluene diisocyanate and / or its prepolymer (TDI prepolymer). Is a mixed polyisocyanate of. Particularly in the mixed polyisocyanate of crude MDI and TDI prepolymer, a mixed polyisocyanate containing 70% by weight or less of TDI prepolymer, particularly preferably 5 to 60% by weight, is preferably used because it has excellent thermal conductivity.

The polyol used in the present invention may be a known polyether polyol and / or polyester polyol, and as the polyether polyol, a usual polyhydric alcohol such as glycol, glycerin, bisphenol, pentaerythritol, trimethylolpropane,
Obtained by adding ethylene oxide or propylene oxide to sucrose or the like, or a fatty acid amine compound such as ammonia or ethyleneamine, an aromatic amine compound such as toluenediamine, diphenylmethane-4,4′-diamine and / or a mixture thereof. It is a polyether polyol. Polyester polyols include those produced from dibasic acids and polyhydric alcohols and those produced from polyethylene terephthalate waste. Among these, for example, the average hydroxyl value is 200 ~ 6
Especially preferred is a polyol of 00, and further a polyol containing 10 to 60 parts by weight of an aromatic polyether polyol derived from toluenediamine.

As the foam stabilizer, for example, a known silicone foam stabilizer used for rigid urethane foam can be used, and the amount thereof is not particularly specified, but is usually 1.0 to 2.5 parts by weight with respect to 100 parts by weight of the polyol. is there.

In the present invention, other auxiliaries can be added as required, and examples include conventionally known flame retardants, colorants, extenders, antioxidants, and UV inhibitors.

In the method of the present invention, the rigid polyurethane foam produced by the polyol and polyisocyanate,
It has a foam density of 10 to 60 kg / m ³ .

[Effect of the Invention] According to the present invention, a problem arises in a rigid polyurethane foam system that maintains a high level of heat insulating properties of a foam, reduces the amount of freon as a foaming agent, and uses a large amount of water. It has become possible to improve the flyability. With the new formulation, it has been possible to manufacture a rigid polyurethane foam in which the amount of freon, which has been considered difficult, is reduced. That is, it can be said that the method for producing a rigid polyurethane foam of the present invention is a new formulation capable of coping with environmental problems due to the fluorocarbon compound because the amount of the fluorocarbon blowing agent used is small.

[Examples] Hereinafter, examples and comparative examples will be described, but the present invention is not limited to these examples.

Examples 1 to 13 and Comparative Examples 1 to 7 The mixing ratios (formulations) of the raw materials were set as follows, and water as a foaming agent and trichlorofluoromethane (R-11) and a catalyst were changed to a predetermined ratio. A foaming test was conducted under foaming conditions. The flyability and physical properties of the produced foam were measured by the following methods. The results are shown in Table-1,
-2.

a. Formulation (parts by weight) Polyol 1) 100 Foam stabilizer 2) 1.5 Water 3.0 to 7.0 R-11 3) 5 to 40 Catalyst 4) Change Isocyanate 5) (NCO / OH = 1.10) 1) Sucrose / Aromatic amine-based polyol, OH value = 423 mgKOH / g (Mitsui Toatsu Chemicals, Inc., SU-464 / NT-40
0) 2) Silicone surfactant (Nippon Unicar Co., Ltd., L
-5340) 3) Trichlorofluoromethane (manufactured by Mitsui Fluorochemical Co., Ltd.) 4) Explanation of catalysts used and catalyst abbreviations in the table NMIZ; 1-methylimidazole DMIZ; 1,2-dimethylimidazole DMAPIZ; 1- (3 -Dimethylaminopropyl) imidazole IBIZ; 1-isobutyl 2-methylimidazole TEDA-L33; Triethylenediamine 33% dipropylene glycol solution (TEDA-L33 manufactured by Tosoh Corporation) TMHMDA; Tetramethylhexamethylenediamine (Tosoh Corporation) ), TOYOCAT-MR) DMCHA; dimethylcyclohexylamine 5) Crude MDI NCO concentration = 31.0% (Nippon Polyurethane Industry Co., Ltd., MR-200) and sucrose-based TDI prepolymer NCO concentration = 31.0% b. Foaming conditions Raw material liquid temperature 20 ± 1 ℃ Stirring speed 6000 rpm (5 seconds) Mold Aluminum box (Dimension; 25 × 25 × 25c
m) Foam mold temperature 40 ° C c. Measurement items Measure the following items.

・ Reactivity Cream time; Foam rise time (seconds) Gel time; Resin (stringing) time (seconds) Tack free time; Time when foam surface is no longer sticky (seconds) Rise time; Foam rise stop time (seconds) -Evaluation of flyability 10 minutes after the foam was formed, the foam surface was pressed with a finger and the brittleness of the foam was evaluated according to the following four grades.

Very brittle ... × Brittle ... △ Slightly brittle ... ○ No brittleness ◎ ・ Foam density, thermal conductivity The density was measured using a test piece with the center of the foam cut to a size of 20 × 20 × 2.5 cm. The test piece as it is ANACON m
The thermal conductivity was measured with odel 88.

As is clear from Table-1 and Table-2, the amount of CFCs is reduced and the amount of water is increased as a blowing agent, and NMIZ and DMI are used as catalysts.
In Examples 1 to 13 using Z, DMAPIZ, and IBIZ, rigid polyurethane foams having good thermal conductivity and flyability were produced. On the other hand, in Comparative Examples 1 to 7, since the flyability is deteriorated, the amount of water cannot be increased, and the reduction of the amount of freon cannot be achieved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C08G 101: 00) C08L 75:04 (56) References JP-A-60-84319 (JP, A) JP-A 63-90529 (JP, A) JP-A 54-128000 (JP, A) JP-A 48-84900 (JP, A) JP-A 59-213717 (JP, A) JP-A 1-256511 (JP, A) JP-B-44-20759 (JP, B1) US Patent 3152094 (US, A)

Claims (5)

[Claims] 1. A method for producing a rigid polyurethane foam by mixing and foaming a polyol and a polyisocyanate in the presence of a foaming agent, a catalyst and other auxiliaries, and as a foaming agent, based on 100 parts by weight of the polyol. Water 2.0
1 part or more selected from the imidazole compound represented by the following general formula (I) as a catalyst. (In the formula, R ¹ is an alkyl group having 1 to 4 carbon atoms, a benzyl group,
A dimethylaminopropyl group or a hydroxyalkyl group having 1 to 3 carbon atoms, R ² represents hydrogen, an alkyl group having 1 to 4 carbon atoms, an allyl group or a benzyl group, and R ³ and R ⁴
Represents hydrogen, a methyl group or a hydroxymethyl group. ) Is used and the average hydroxyl value of the polyol is 200 to 600 mgKOH /
A method for producing a spray-type polyurethane foam having a foam density of 10 to 60 kg / m ³ , characterized by being g. 2. The production method according to claim 1, wherein the blowing agent is 3.0 parts by weight or more of water and 30 parts by weight or less of halogenated hydrocarbon with respect to 100 parts by weight of the polyol. 3. The catalyst is at least 1-methylimidazole, 1,2-dimethylimidazole, 1- (3-dimethylaminopropyl) imidazole, 1-n-butyl-2.
-Methylimidazole or 1-isobutyl-2-methylimidazole, 1 or more types selected, The manufacturing method of Claim (1) characterized by the above-mentioned. 4. The polyisocyanate is a mixed polyisocyanate comprising diphenylmethane-4,4′-diisocyanate and / or its polymerized isocyanate and toluene diisocyanate and / or its prepolymer. Manufacturing method. 5. The method according to claim 4, wherein the concentration of the toluene diisocyanate prepolymer in the mixed polyisocyanate is in the range of 70% by weight or less.