JP2001329036A - Production method for rigid polyurethane foam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem such that compared to using a chlorofluorocarbon as a blowing agent, a rigid polyurethane foam produced by using carbon dioxide or a hydrocarbon as a blowing agent is liable to shrink at normal temperature when the foam has a low-density. SOLUTION: The foam properties, e.g. dimensional stability, at normal temperature can be improved by increasing the amount of an isocyanate compound required according to hydroxyl value to larger than usually required in a specified range and by using a specific polyol and a specific catalyst, each in a specified range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a rigid polyurethane foam using carbon dioxide gas or hydrocarbon as a blowing agent and using no chlorofluorocarbon blowing agent which is harmful to the global environment.

[0002]

2. Description of the Related Art A rigid polyurethane foam obtained by mixing a polyisocyanate, a polyol, a catalyst, a foam stabilizer, other auxiliaries, and a foaming agent can be used as a structural material having a self-adhesive force, and has a high moldability. Widely used as an excellent heat insulating material. However, chlorofluorocarbons such as trichlorofluoromethane (CFC-11), which has been used in large quantities as a foaming agent for rigid polyurethane foams, have already been discontinued due to the destruction of the ozone layer, and are currently mainly used. 1,
1-dichloro-1-fluoroethane (HCFC-141
Hydrochlorofluorocarbons such as b) are similarly regulated. Hydrofluorocarbons expected as next-generation foaming agents are greenhouse gases and have a much higher global warming potential than carbon dioxide, so their use in the future is likely to be limited. Although it is certain that carbon dioxide and hydrocarbons can be used in the future in terms of environmental characteristics, they are both chlorofluorocarbon and hydrochlorofluorocarbon,
It has various disadvantages.

[0003]

Rigid polyurethane foams foamed with carbon dioxide gas and hydrocarbons resulting from the reaction of water and polyisocyanate have a lower density at room temperature than foams foamed with chlorofluorocarbons. Is known to have poor dimensional stability. If such a foam is left at room temperature, it gradually shrinks over a long period of time, and may eventually result in abnormal appearance of the product. It is known that the cause is correlated with the fact that carbon dioxide gas in the foam of the foam easily permeates through the polyurethane resin membrane and is easily released to the outside. Therefore, only carbon dioxide is used as a foaming agent.
% Water foaming is particularly remarkable. In particular, among the hydrocarbon blowing agents, pentanes, in particular, are poorly soluble in polyol and are easily separated, and are more frequently mixed in the premix than chlorofluorocarbons such as CFC-11 or hydrochlorofluorocarbons such as HCFC-141b. Can not. Therefore, in order to lower the density, it is necessary to use a relatively large amount of water in combination, and a similar symptom occurs because the concentration of carbon dioxide in the bubbles of the foam increases. One of the solutions to this problem is the simultaneous formation of air bubbles, which has the greatest drawback of deteriorating the strength of the foam, and its application to fields where strength is not required is limited. The present invention
An object of the present invention is to provide a solution to the problem of dimensional change at room temperature.

[0004]

In the rigid polyurethane foam, the required weight of isocyanate in a chemical equivalent to the polyol is derived from the following formula.

[0005]

(Required number of parts by weight of isocyanate with respect to 100 parts by weight of polyol) = {(isocyanate index) / 100} × {(chemical formula of NCO) × 100 / NCO%} /｝ (chemical formula of KOH) × 100 / OHV｝ = {(isocyanate index) / 100} × 7.49 × (OHV / NCO%) where isocyanate index is a coefficient (100 fraction. Synonym: 100
Sometimes displayed as a constant divided by. OHV: hydroxyl value of polyol (mg KOH / g) NCO%: weight% of NCO groups in isocyanate

In general, rigid polyurethane foams generally have an isocyanate index in the range of 105 to 120. When the isocyanate index is 105 or less, there is a possibility that the composition may be shifted to the one containing more polyol when the foaming conditions fluctuate even slightly, which is not preferable in foam performance. Further, when the isocyanate index is generally 120 or more,
Unreacted isocyanate increases, and the polymerization does not proceed sufficiently, so that flyability (fragility) is generated and adhesive properties are degraded, which causes problems in foam performance. Also,
In the case of a rigid polyurethane foam using a large amount of water as a foaming agent, the hydroxyl value of water is extremely high at 6,230 mgKOH / g, so that the required number of parts by weight of the isocyanate is too large, the mixing is uneven, and the stirring becomes difficult. Handling problems arise, such as restrictions on the function of the foaming machine. For the above reasons, it is not common for ordinary rigid polyurethane foams to use an isocyanate index of 120 or more as in the present invention.

Further, in order to obtain a polyisocyanurate foam mainly for the purpose of improving the combustion resistance, a catalyst having an isocyanate index of at least 150, generally at least 200 and having a trimerizing function is required. It is common practice to incorporate an isocyanurate ring into the foam by blending it as the main catalyst. The polyisocyanurate foam has an advantage that the flame resistance is improved by the property of the isocyanurate ring formed by trimerizing the polyisocyanate. In general, in a polyisocyanurate foam, the higher the conversion of the trimerization of polyisocyanate, the higher the flame resistance, and thus the isocyanate index is set to 200 or more. When the isocyanate index is 150 or less, the ratio of urethane bonds forming a normal urethane foam or urea bonds generated by reaction with water increases, so that the combustion resistance is significantly deteriorated. In addition, a general tertiary amine compound catalyst used for generating a normal urethane bond or a urea bond generally has a function of trimerization that is not large, and is therefore intended to obtain a polyisocyanurate foam. For this purpose, a catalyst having a trimerization function must be used as a main catalyst. When the ratio of the catalyst having the trimerization function is small, the conversion of the trimerization is too low, and the combustion resistance is also significantly deteriorated. Therefore, when a polyisocyanurate foam is usually obtained, as in the present invention, setting the isocyanate index to 150 or less and lowering the ratio of the catalyst having the function of trimerization requires reducing the conversion of trimerization. This is an unusual method because it tends to lower

[0008] The inventors of the present invention provide carbon dioxide or
Any one of hydrocarbons including pentanes,
Or, in a low-density foam foamed with a combination of two or more, isocyanate index is 120 ~
The rigid polyurethane foam foamed in the range of preferably 150 to 125 to 140 is an isocyanate index of 105 to 105 used in a normal rigid polyurethane foam.
From the foam No. 120, it was found that the dimensional stability under an atmosphere of 50 ° C. and 95% relative humidity, which is considered to be a criterion for dimensional change characteristics at normal temperature, is remarkably improved.

Generally, an isocyanate index of 12
When it is 0 or more, the occurrence of flyability is liable to occur, and the inconvenience such as a large deviation of the mixing of the premix solution of isocyanate and polyol occurs. In the present invention, it is necessary to take measures because the isocyanate index is set to 120 to 150. . The rigid polyurethane foam of the present invention was able to solve these disadvantages by limiting the following raw materials among compositions comprising a polyisocyanate, a polyol, a foaming agent, and an auxiliary.

Among the raw materials used in the present invention, for the polyisocyanate, it is desirable to use polymeric MDI.
DI) or diphenylmethane diisocyanate (M
There is no problem even if a polyisocyanate substituted for a prepolymer such as DI) is used.

The polyol has a hydroxyl value of 150 to 600.
mgKOH / g, desirably 250-500 mgKOH
/ G range, flyability and the like are eliminated, and (1) a polyether polyol having a hydroxyl value in the range of 150 to 600 mgKOH / g obtained by addition-polymerizing an alkylene oxide to the soucrose; (2) polyether polyol having a hydroxyl value in the range of 150 to 600 mgKOH / g obtained by addition-polymerizing an alkylene oxide to toluenediamine; (3) any one of monoethanolamine, diethanolamine, and triethanolamine Or a polyether polyol having a hydroxyl value in the range of 150 to 600 mgKOH / g, obtained by addition-polymerizing an alkylene oxide to a combination of a plurality of the compounds. (1) to (3)
In the formulation of the rigid polyurethane foam, any one of the polyols, or a combination thereof,
The present inventors have found that dimensional stability at room temperature is significantly improved by using the polyol in an amount of 40 to 100 parts by weight based on 100 parts by weight of the polyol.

The blowing agent generally contains a chlorofluorocarbon blowing agent. However, when a chlorofluorocarbon blowing agent is used, shrinkage at room temperature hardly occurs. Therefore, the blowing agent used in the present invention may be carbon dioxide or pentane. The most effective effect is obtained when any one or a combination of a plurality of hydrocarbons containing is used.

As a catalyst for urethane, a catalyst having a trimerization function is not so good in foam fluidity and the like.
(A) potassium octylate, potassium acetate, quaternary ammonium formate, quaternary
Quaternary ammonium octylate, tris (3-dimethylaminopropyl) hexahydro-s-triazine, and any one of tris2,4,6- (dimethylaminomethyl) phenol, or a combination thereof,
For 100 parts by weight of the polyol in the polyurethane formulation,
It is used only with a slight addition in the range of 0 to 0.5 part by weight, but it does not matter if it is not used at all. (B) tetramethylhexamethylenediamine, pentamethyldiethylenetriamine, trimethylaminoethylpiperazine, dimethylcyclohexylamine, tetramethylethylenediamine, triethylenediamine, and bis (2-dimethylamino) Either one or a combination of a plurality of ethyl) ethers is used as a main catalyst in a range of 0.5 part by weight or more with respect to 100 parts by weight of a polyol in the formulation of a rigid polyurethane foam, so that foam fluidity can be improved. The inventors of the present invention have found that the foam performance of the present invention is good. As other auxiliaries, ordinary commercially available ordinary foam stabilizers, flame retardants and the like can be used.

Since dimensional stability at room temperature requires time until a tendency appears, an accelerated test is required. Regarding the dimensional stability acceleration test at room temperature, there is no method specified in Japanese Industrial Standards and others, and each company conducts it. Our company uses the evaluation of dimensional stability under an atmosphere of 50 ° C and 95% relative humidity as an accelerated test. Rigid polyurethane foam, which tends to undergo dimensional change at room temperature, shows a clear shrinkage after about 100 days when a foam with a pack ratio of 100% is allowed to stand at room temperature, but when the same foam is allowed to stand at 50 ° C. and 95% relative humidity atmosphere. Show a similar tendency to shrink after about 2 weeks. Similar shrinkage may occur even under dry conditions at 100 ° C, but in many cases the tendency is different.
The dimensional stability of each formulation at normal temperature is determined by measuring the dimensional change rate in a 0 ° C. 95% relative humidity atmosphere.

As mentioned above, the inventors of the present invention have determined that the isocyanate index is not typical for ordinary rigid polyurethane foams, from 120 to 150, preferably from 12 to 150.
The catalyst is used in the range of 5 to 140, and the trimerization catalyst (a) is used in a small amount of 0 to 0.5 part by weight based on 100 parts by weight of the polyol, and the foam catalyst (b) is usually used as a main catalyst. In a method that is not common for polyisocyanurate foams, in which 0.5 parts by weight or more is used,
By using 40 to 100 parts by weight of the polyols (1) to (3) out of 100 parts by weight of the polyol, 50
It can provide a significant improvement in dimensional stability in an atmosphere at a relative humidity of 95 ° C. and a polyol value of 150 to 600, preferably 250 to 500 mg KOH.
By setting the ratio to / g, it was possible to solve the problem of flyability caused by a relatively high isocyanate index and the problem that the compounding ratio is largely biased.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION These polyols, catalysts and auxiliaries can be mixed to form a premix liquid by a known method such as an electric mixer or a static mixer. The obtained premix liquid can be mixed with the polyisocyanate using an existing foaming machine or mixer, whereby a rigid polyurethane foam can be produced. The present invention is not limited to the type of foaming machine or mixer for rigid polyurethane foams, and commercially available well-known ones can be used.

[0017]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Example 1 Table 1 shows Formulation 1 of Comparative Example and Formulations 2 to 4 of Examples. Toho Chemical Co. polyol, water, Kao tertiary amine catalyst Kaorizer No. 1 (TMHDA), Nippon Unicar silicone foam stabilizer L-5420, and Akzo Kashima flame retardant Filol PCF were charged into paper cups having an internal volume of 500 cm ³ , respectively, and mixed so as to be sufficiently uniform. And The stock solution temperature of the premix solution was adjusted to 20 ° C., and the stock solution temperature was previously adjusted to 20 ° C. in the Cosmonate M-200 manufactured by Mitsui Chemicals.
And 7.0,0 with an electric mixer manufactured by Tokushu Kika Kogyo.
The mixture was stirred for 4 seconds at a rotation speed of 00 rpm. 2.5cm thick with a polyethylene release sheet attached in advance,
This mixture was immediately charged into a 50 cm square aluminum vertical panel and foamed. After measuring the cream time and the gel time, the rigid polyurethane foam obtained after 5 minutes was taken out, the density was calculated from the foam weight and the panel volume, and the density was defined as the density when the pack ratio was 100%. The next day, three samples of 35 cm in length and 7 cm in width were cut out from the panel form, and the thickness at the start was measured with a dial caliper gauge LO-1 manufactured by Ozaki Seisakusho.
It was left in an atmosphere of 0%, 100 ° C, and 50 ° C and a relative humidity of 95%, the maximum dimensional change after 2 weeks was measured, and the maximum dimensional change was calculated. The closed cell rate was measured using an air comparison specific gravity meter manufactured by Toshiba Beckman.

[0019]

[Table 1]

The formulation 1 of the comparative example and the formulations 2 to 4 of the examples shown in Table 1 had the same type of polyol and the same number of parts by weight. Are the same. The same type of isocyanate was used, and the isocyanate index was 105 in Formula 1 of Comparative Example and 125 to 150 in Formulas 2 to 4 of Examples. For each of these formulas, cream time, gel time,
The density, dimensional change, and flyability were measured.

Comparing these performances, with respect to the dimensional change rate in a 50 ° C., 95% relative humidity atmosphere, which is considered to have a correlation with the dimensional stability at room temperature, the formulation of the comparative example having an isocyanate index of 105 was obtained. -14.2% for 1
In contrast, Formulation 2 of Example having an isocyanate index of 125 was -8.6% and the rate of change was slightly poor, but improved, and the isocyanate index was 1
-2.5% for formulation 3 of the 40 example and -0.8% for formulation 4 of the example with an isocyanate index of 150
It can be seen that the higher the isocyanate index, the better the wet heat dimensional stability. From this,
It is believed that the lower limit of the isocyanate index is 120, preferably 125. However, as the isocyanate index increases, the degree of flyability also worsens, with the occurrence at 150 and the slight increase at 140, the upper limit of the isocyanate index is 15
It is considered that it is 0, preferably about 140.

Example 2 The formulations 5 to 6 of the comparative example and the formulations 7 to 8 of the example shown in Table 2 were prepared by using two toluenediamine-based polyols manufactured by Toho Chemical Industry having different hydroxyl values.
Using a gKOH / g Tohopolyol AR-2589, a formulation with an isocyanate index of 115 was used as the formulation 5 of the comparative example, and a hydroxyl value of 300 mgKOH / g.
Was used as the formulation 6 of the comparative example using the Toho polyol AR-750 of No. 1 with an isocyanate index of 115. Using these polyols, the formulations having an isocyanate index of 130 were formulated as Formulations 7 to
And 8. The method for preparing the stock solution, the method for producing the rigid polyurethane foam, and the method for measuring the performance of the rigid polyurethane foam are the same as those in Example 1.

[0023]

[Table 2]

Tohopolyol AR- having a high hydroxyl value
Comparing Formulation 5 of Comparative Example with low isocyanate index and Formulation 7 of Example with high isocyanate index at 2589, Formulation 7 shows that
The dimensional change rate under the relative humidity atmosphere is higher than that of the prescription 5, but at the same time, the degree of flyability is poor, and the mixing ratio of the isocyanate and the premix is 100/56.
0 to 100 / 49.9. On the other hand, Toho polyol AR-75 having a low hydroxyl value is used.
In the case of 0, Formulation 8 of Example having a high isocyanate index also has a higher dimensional change rate in a 50 ° C. and 95% relative humidity atmosphere than Formulation 6, but the deterioration of flyability due to a low hydroxyl value is not significant. It was not observed, and the compounding ratio was 100 / 56.9, which was the same level as Formulation 5 of the comparative example. Therefore, it is considered that the lower the hydroxyl value of the polyol, the better the flyability and the mixing ratio, and it is considered that there is an upper limit. However, if the hydroxyl value is too low, the strength and dimensional change rate of the rigid polyurethane foam deteriorate, so it is considered that there is a lower limit.
50 to 600 mgKOH / g, desirably 250 to 50 mgKOH / g
It is considered to be in the range of 0 mg KOH / g.

[0025]

Industrial Applicability According to the present invention, in a method for producing a rigid polyurethane foam using a carbon dioxide gas or a hydrocarbon as a foaming agent without using a chlorofluorocarbon-based foaming agent which is a substance that destroys the environment, the appearance of the foam becomes serious. The dimensional stability at room temperature is greatly improved, and a practical and low-density rigid polyurethane foam can be obtained without performing simultaneous formation of cells that deteriorate the strength. In addition, the rigid polyurethane foam of the composition of the present invention can provide excellent foam performance by selecting and using an appropriate polyol, thereby improving the flyability and, as a result, increasing the adhesive strength. INDUSTRIAL APPLICABILITY The present invention is extremely effective when a CFC-based blowing agent that is currently frequently used can no longer be used.

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Claims (5)

[Claims] 1. A foaming agent containing no fluorocarbon-based foaming agent, one of carbon dioxide, or a hydrocarbon containing pentanes, or a combination thereof. A method for producing a rigid polyurethane foam, wherein an isocyanate index, which is a coefficient for multiplying a required weight, is set to 120 to 150. 2. Polyols having a hydroxyl value in the range of 150 to 600 mgKOH / g obtained by addition-polymerizing an alkylene oxide to sucrose, and (2) adding an alkylene oxide to toluenediamine are used as polyols. The hydroxyl value obtained by polymerization is 150 to 600 mgKOH /
g of polyether polyol, (3) monoethanolamine, diethanolamine, or triethanolamine in any one or a combination thereof, and the hydroxyl value obtained by addition polymerization of alkylene oxide is 150 to 600 mgKOH. /
In the formulation of the rigid polyurethane foam, any one of the polyols of (1) to (3), which are limited as the polyether polyol in the range of g, or a combination of a plurality of the polyols, is added to 4% of 100 parts by weight of the polyol.
Characterized in that it is used in a range of 0 to 100 parts by weight,
A method for producing the rigid polyurethane foam according to claim 1. 3. The catalyst comprises (a) potassium octylate, potassium acetate, quaternary ammonium formate, quaternary ammonium octylate, tris (3-dimethylaminopropyl) hexahydro-s-triazine, and tris Any one or a combination of a plurality of 2,4,6- (dimethylaminomethyl) phenols is added to the polyol 1 in the formulation of the rigid polyurethane foam.
For 0 parts by weight, use in the range of 0 to 0.5 parts by weight,
And (b) one or more of tetramethylhexamethylenediamine, pentamethyldiethylenetriamine, trimethylaminoethylpiperazine, dimethylcyclohexylamine, tetramethylethylenediamine, triethylenediamine, and bis (2-dimethylaminoethyl) ether The method for producing a rigid polyurethane foam according to claim 1 or 2, wherein the composition is used in an amount of 0.5 part by weight or more based on 100 parts by weight of a polyol in the formulation of the rigid polyurethane foam. 4. The method for producing a rigid polyurethane foam according to claim 1, wherein the molded article of the rigid polyurethane foam has a density of 0.020 to 0.200 g / cm ³ . 5. The method for producing a rigid polyurethane foam according to claim 1, which is used as a heat insulating material or a filler that requires structural strength.