JPH0710955A - Production of rigid polyurethane foam - Google Patents

Abstract

PURPOSE:To obtain a rigid polyurethane foam excellent in thermal insulating properties, mechanical characteristics, and dimensional stability by using a foamable compsn. mainly comprising specific polyols, a polyisocyanate, and a specified amt. of water and utilizing CO2 generated as the blowing agent. CONSTITUTION:This rigid polyurethane foam is obtd. by using a foamable compsn. mainly comprising 100 pts.wt. polyol consisting of 20-40 pts.wt. toluenediamine-based polyether polyol having an OH value of 360-440, 40-60 pts.wt. sorbitol-based polyether polyol having an OH value of 200-260, and 10-30 pts.wt. arom. polyester polyol having an OH value of 160-240 (e.g. a polycondensate of terephthalic acid with ethylene glycol), a polyisocyanate (e. g. polymeric MDI), and 4-8 pts.wt. water.

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 rigid polyurethane foam (hereinafter referred to as rigid foam) using a carbon dioxide gas produced by the reaction of isocyanate and water as a foaming agent, and particularly to various methods. The present invention relates to a heat insulating material, a method for producing a rigid foam suitable for a building material, which has a high degree of heat insulating property, mechanical properties and dimensional stability.

[0002]

2. Description of the Related Art Rigid foam has many features such as heat insulating property, moldability, light weight and high strength.
Widely used as a building material. This rigid foam is made into a foam by volatilizing the low boiling point solvent by utilizing the heat of reaction and incorporating it into the polymer, but as this low boiling point solvent, it is inert and extremely stable as compared with conventional ones. Chlorofluorocarbon (hereinafter referred to as CFC), which has a very low thermal conductivity in a gas state, is often used. In the current rigid foam manufacturing technology, this CFC is used as a main foaming agent, and a small amount of other foaming agent components are used in combination therewith.

However, CFCs are required to be used in a reduced amount because they destroy the ozone layer in the atmosphere, and in the near future, they cannot be used at all. Hydrochlorofluorocarbons (hereinafter referred to as HCFCs) and hydrofluorocarbons (hereinafter referred to as HFCs) are being developed as foaming agents to replace CFCs. However, HCFCs do not destroy ozone at all and the conventional CFs are not used.
It has an ozone layer depleting capacity of about 5 to 10% compared to C, and since HFC does not contain a chlorine atom in its molecule, it is said that it does not destroy the ozone layer. , It is considered that when it exists in the atmosphere, it becomes a major factor of global warming. Under such circumstances, HCFCs and HFCs that are being developed as alternative blowing agents for CFCs are not necessarily radical alternative blowing agents, and it is speculated that they will be subject to some use restrictions in the near future.

Therefore, the use of carbon dioxide gas as a foaming agent that does not have the above problems is being studied. Although the method of utilizing this carbon dioxide has been conventionally studied, it is difficult to produce a rigid foam having poor foaming stability and a high closed cell rate, and the surface brittleness of the rigid foam is high with various surface materials. Poor adhesion or cure, and because the generated carbon dioxide gas diffuses at a high rate, the carbon dioxide gas taken into the polyurethane easily volatilizes into the air from the cell walls, and the dimensional stability of rigid foam is stable. In addition to being inferior in properties, it also has low heat insulation performance and practical rigid foams have not been obtained.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
By providing a combination of the type and amount of the raw material polyol without using any harmful foaming agent such as FC or HFC at all, a method for producing a rigid foam is provided, in which the above drawbacks of the carbon dioxide gas foaming method are greatly improved. To do.

[0006]

The first aspect of the present invention is to produce a rigid polyurethane foam using a foaming composition containing polyisocyanate, a polyol and water as main components, and the total amount of the polyol is 100 parts by weight. In the case of (A) 20 to 40 parts by weight of a toluenediamine-based polyether polyol having a hydroxyl value of 360 to 440, and (B) 40 to 60 parts by weight of a sorbitol-based polyether polyol having a hydroxyl value of 200 to 260. , (C) 10 to 30 parts by weight of an aromatic polyester polyol having a hydroxyl value of 160 to 240,
In addition, 4 to 8 parts by weight of water is used with respect to 100 parts by weight of the polyol.

As the above-mentioned "polyisocyanate", all polyisocyanates conventionally used for producing rigid foams can be used. Particularly preferred is a polymeric isocyanate containing diphenylmethane diisocyanate as a main component. Further, as the catalyst, the foam stabilizer, and other auxiliaries, those conventionally used for producing rigid or flexible foams can be used as they are.

As the above-mentioned "toluenediamine-based polyether polyol" (hereinafter referred to as polyol A), a polyol obtained by using toluenediamine as a main reaction initiator and adding an alkylene oxide is preferable.
The hydroxyl value adjusted to 360 to 440 can be used. 2,4 as toluenediamine
The isomers, 2,6 isomers or mixtures or crudes thereof can be used. As the alkylene oxide, ethylene oxide, propylene oxide, butylene oxide and the like can be used alone or in combination, but it is common to use propylene oxide, which is preferable in terms of raw material price and physical properties of the rigid foam.

The hydroxyl number of polyol A is 360 to
When the hydroxyl value is in the range of 440, the dimensional stability of the rigid foam is lowered when the hydroxyl value is less than 360, and the surface brittleness of the rigid foam becomes high when it exceeds 440, which is not preferable. The total amount of polyol A used is 1
When the amount is 00 parts by weight, it is in the range of 20 to 40 parts by weight. When the amount of the polyol A is less than 20 parts by weight, the compatibility and fluidity of the "foamable composition" are low, the polymerization reaction may be stopped in the middle, and the dimensional stability of the rigid foam obtained by a slight change in the foaming conditions. As a result, a good rigid foam cannot be obtained. On the other hand, if the amount exceeds 40 parts by weight, the surface of the rigid foam becomes brittle, resulting in poor adhesion to the surface material.

As the "sorbitol-based polyether polyol" (hereinafter, referred to as polyol B), sorbitol is used as a reaction initiator, and a polyol having a hydroxyl value of 200 to 260 adjusted by adding an alkylene oxide is used. You can Glycerin, water, ethylene glycol or the like can be used in combination as a reaction initiator for producing the polyol B. In that case,
The average number of functional groups of the reaction initiator is preferably 5 or more. For example, when glycerin is used in combination with sorbitol (since sorbitol is 6-functional and glycerin is 3-functional), in order to make the average number of functional groups 5 or more, the molar ratio of sorbitol is 2/3 or more, and glycerin is molar ratio. 1/3
Must be less than. The reason why the preferable average number of functional groups is 5 or more is that when it is less than 5, the dimensional stability of the obtained rigid foam is lowered, and this dimensional stability is particularly remarkable at low temperatures.

Polyol B has a hydroxyl value of 200-
When the hydroxyl value is in the range of 260, the dimensional stability of the rigid foam is lowered when the hydroxyl value is less than 200, and when the hydroxyl value is more than 260, the dimensional stability of the rigid foam is improved, but the surface brittleness becomes high and a practical one is obtained. I can't. Further, as in the second aspect of the present invention, as the polyol B, those having a high hydroxyl value and those having a low hydroxyl value can be combined, and 40 to 60 parts by weight of those having a hydroxyl value in the range of 200 to 260 can be used. . Polyol B
The amount used is in the range of 40 to 60 parts by weight when the total amount of polyol is 100 parts by weight. Polyol B is 4
If it is less than 0 parts by weight, the strength of the obtained rigid foam is low and the dimensional stability is also lowered. On the other hand, when the amount exceeds 60 parts by weight, the surface of the rigid foam becomes brittle and the adhesion to the surface material becomes poor.

The above "aromatic polyester polyol"
As (hereinafter, referred to as polyol C), polyol C having a hydroxyl group at the molecular end and polyethylene terephthalate produced by polycondensation reaction of terephthalic acid with various glycols such as ethylene glycol, diethylene glycol and butylene glycol are decomposed with various glycols. The polyol C and the like obtained in this way can be used. Most of the hydroxyl groups contained in these polyols C are primary and secondary are almost nonexistent. Further, the compatibility-improving type polyol C to which a nonylphenol-based surfactant or the like is added can also be used.

The hydroxyl number of Polyol C is 160-
When the hydroxyl value is less than 160, the viscosity becomes too high to be practically used, and when it exceeds 240, the viscosity becomes low and the handling becomes easy, but the compatibility with the polyol A and the polyol B is high. There is a problem that it becomes low and difficult to use. The amount of the polyol C used is in the range of 10 to 30 parts by weight when the total amount of the polyol is 100 parts by weight. When the amount of the polyol C is less than 10 parts by weight, it is difficult to obtain a rigid foam having fine cells. On the other hand, when the amount of the polyol C exceeds 30 parts by weight, the strength of the rigid foam is lowered and the dimensional stability is lowered.

The blowing agent used in the present invention is carbon dioxide gas produced by the reaction of polyisocyanate and water during the production of polyurethane, and CFC, HCFC and HFC are not used at all. The "water" used is preferably distilled water or ion-exchanged water. Tap water and groundwater should not be used as they are, as they have a negative effect on the stability of amine catalysts. The amount of water used is preferably 4 to 8 parts by weight, more preferably 5 to 7 parts by weight, based on 100 parts by weight of the polyol. When the amount of water used is less than 4 parts by weight, the amount of carbon dioxide gas generated is small, and it becomes impossible to obtain a target low-density rigid foam, and when the amount of water exceeds 8 parts by weight, the density becomes too low, Rigid foam having practical mechanical strength cannot be obtained.

The raw materials for producing the rigid foam of the present invention include polyisocyanate, polyol, water, a catalyst,
Use foam stabilizers and other auxiliaries. Further, in order to reduce the viscosity of the raw material composition and facilitate stirring and mixing, various liquid flame retardants, diluents, plasticizers and the like can be used, and the amount used significantly impairs the performance of the obtained rigid foam. Unless otherwise specified, there is no particular limitation. Liquid flame retardants include halogenated phosphates such as tris (2-chloroethyl) phosphate and tris (chloropropyl) phosphate, alkylene carbonates such as propylene carbonate as a diluent, dialkyl such as dioctyl phthalate as a plasticizer Phthalates can be used.
The use of the liquid flame retardant contributes not only to the effect of imparting flame retardancy to the rigid foam but also to the reduction of the viscosity of the rigid foam. However, if the amount used is too large (for example, 30 parts by weight or more with respect to 100 parts by weight of polyol), the high-temperature dimensional stability of the obtained rigid foam is significantly deteriorated, which is not preferable.

The isocyanate index (hereinafter referred to as "index") of the foamable composition of the present invention is preferably in the range of 100 to 150, and particularly preferably in the range of 105 to 130, as in the conventional formulation of rigid foam. Index is 10
When it is less than 0, the dimensional stability of the obtained rigid foam may be lowered, and when it exceeds 150, the surface brittleness of the rigid foam becomes high, which is not preferable.

[0017]

In the method for producing a rigid foam using carbon dioxide as a blowing agent, when polyisocyanate and a polyol react to form polyurethane, carbon dioxide and polyurea are produced by the reaction between polyisocyanate and water. Utilizing the reaction, the carbon dioxide gas generated is taken into the polyurethane to form a foam. In the present invention, it was possible to produce a rigid foam which can be practically used as a blowing agent by using carbon dioxide gas by limiting the type of the polyol, the combination thereof, and the amount ratio thereof, but the theoretical basis thereof should be sufficiently clarified. Is not done.
At the present time, it is necessary to control in a well-balanced manner the reaction that produces polyurethane by the reaction of polyisocyanate and polyol (polymerization reaction) and the reaction that produces carbon dioxide and polyurea by the reaction of polyisocyanate and water (foaming reaction). Is considered to be important, and it is considered that the above-mentioned limitation of the type of the polyol, the combination thereof, and the amount ratio are suitable for this balance.

The action of each polyol is presumed as follows. (a) Polyol A improves the compatibility of the entire reaction system, and since the basicity of the entire reaction system is increased by the amino group of toluenediamine, it is possible to increase the reactivity of the polyisocyanate with the polyol / water. Therefore, the degree of completion of the polymerization reaction can be increased. (b) Polyol B has an average of five or more functional initiators for producing Polyol B, and therefore increases the crosslink density of the produced polyurethane and contributes to the improvement of mechanical strength and dimensional stability. (c) Since the polyol C contains a primary hydroxyl group, it reacts quickly with the polyisocyanate and rapidly gels to take in carbon dioxide gas as a foaming agent and contribute to the formation of fine bubbles. By combining the actions of the polyols described in detail above, it is possible to obtain a rigid foam in which fine air bubbles are uniformly dispersed and have excellent heat insulating properties, high mechanical strength, low surface brittleness, and excellent dimensional stability. It is speculated that

[0019]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. (1) Raw materials used (a) Polymeric MDI "Millionate MR" manufactured by Nippon Polyurethane Industry Co., Ltd.
-100 "was used. Free isocyanate content is 3
It is 1.5%. However, in Example 17, "Millionate MR-200" and "Millionate MR-300" were used. (b) Polyols A, B, and C Polyols shown in Table 1 were used. However, in Table 1, polyols B ₁ , B ₂ and B ₃ represent polyols B having different hydroxyl values and viscosities. (c) Water Ion-exchanged water (d) Silicone foam stabilizer "SH-" manufactured by Toray Dow Corning Silicone Co., Ltd.
193 "was used. (e) Polymerization catalyst Tetramethylhexamethylenediamine (f) Liquid flame retardant tris (chloropropyl) phosphate (abbreviated as TCPP) (g) Plasticizer dioctylphthalate (h) Diluent propylene carbonate

[0020]

[Table 1]

(2) Composition of Foaming Compositions of Examples and Comparative Examples The compositions of the foaming compositions of Examples 1 to 9 are shown in Table 2 and Example 1
The compositions of the foamable compositions of 0 to 16 are shown in Table 3. Table 4 shows the compositions of the foamable compositions of Comparative Examples 1 to 8. The proportions of the respective components of the foamable composition in each table are all expressed in parts by weight, and the components other than the polyol are expressed in parts by weight relative to 100 parts by weight of the polyol.

[0022]

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

Incidentally, * in Table 4 indicates that it is out of the scope of the claims. (3) Manufacture of Rigid Foam Specimen In any of Examples 1 to 16 and Comparative Examples 1 to 8 described below, the rigid foam specimen has an inner dimension of 50 × 300 × 1.
Install a 000mm aluminum mold horizontally,
A foamable composition having a predetermined composition was poured into this by a hand mixing method and molded. A wax-based mold release agent was applied to the inner surface of the mold each time it was used. The temperature of the foamable composition to be injected was set to 21 to 25 ° C, and the mold temperature was set to 40 to 50 ° C.

(4) Performance Test of Specimen A performance test was conducted on the test body obtained in (3) above by the following method. (a) Density, compressive strength and thermal conductivity are JIS A 9514
It was measured according to. (b) High temperature dimensional stability is 70 ℃, low temperature dimensional stability is -3
50x100x10 in a constant temperature bath set to 0 ℃
Two 0 mm test pieces were allowed to stand for 24 hours for heat treatment and then taken out, and the dimensional change rates in the thickness direction and the plane direction were measured. Dimensional change rate = (Dimension before heat treatment-Dimension after heat treatment) / Dimension before heat treatment In each table, ◯: Dimensional change rate is less than 1% and good x: Dimensional change rate is 1% or more and is indicated as poor. (c) Surface brittleness was evaluated by finger touch. In each table, ◯: good with no brittleness Δ: slightly brittle x: highly brittle and impractical

(5) Experimental example in which the amount of polyol A was varied Examples 1 to 3 and Comparative examples 1 and 2 Example 1: The compounding amounts of polyols A, B and C were all set to intermediate values of the limited values. Example 2: The compounding amount of polyol A was set as the upper limit amount. Example 3: The blending amount of polyol A was set as the lower limit amount. Comparative Example 1: The blending amount of Polyol A was set to an amount exceeding the upper limit value. Comparative Example 2: The blending amount of the polyol A was set to be less than the lower limit value. As a result, in Examples 1 to 3, all of the obtained rigid foam sheets were good in density, compressive strength, thermal conductivity, dimensional stability at high and low temperatures, and surface brittleness. On the other hand, in Comparative Example 1, there was no problem in dimensional stability and the like, but there was a problem in surface brittleness, and in Comparative Example 2, since the rigid foam obtained partially contracted, another performance test was conducted. There wasn't.

(6) Experimental example in which the amount of polyol B was varied Examples 4 and 5 and Comparative examples 3 and 4 Example 4: The compounding amount of polyol B ₁ was set as the upper limit amount. Example 5: The blending amount of polyol B ₁ was set as the lower limit amount. Comparative Example 3: The blending amount of the polyol B ₁ was set to an amount exceeding the upper limit value. Comparative Example 4: The blending amount of the polyol B ₁ was set to be less than the lower limit value. As a result, in Examples 4 to 5, all performances were good as in Example 1, but Comparative Example 3 was inferior in dimensional stability and Comparative Example 4 was inferior in surface brittleness.

(7) Experimental example in which the amount of polyol C was varied Examples 6 and 7 and Comparative examples 5 and 6 Example 6: The compounding amount of polyol C was set as the upper limit amount. Example 7: The blending amount of polyol C was set as the lower limit amount. Comparative Example 5: The blending amount of Polyol C was set to an amount exceeding the upper limit value. Comparative Example 6: Polyol C was not used. As a result, in Examples 6 to 7, all performances were good as in Example 1, but Comparative Example 5 was inferior in dimensional stability and Comparative Example 6 was inferior in surface brittleness.

(8) Test Example Using Polyol B as a Mixture of Two Types Examples 8 and 9 Example 8: The polyol B ₁ in Example 1 was changed to a mixture of polyols B ₂ and B ₃ . Example 9: TCPP was not used in Example 8. As a result, all performances were good as in Example 1 except that the density in Example 9 was slightly lowered.

(9) Test Examples in which Other than the Main Components of Example 1 are Changed Examples 10 to 12 Example 10: TCPP was not used in the examples. Example 11: Dioctyl phthalate was added in Example 1. Example 12: Propylene carbonate was added in Example 1. As a result, all performances were good as in Example 1 except that the density in Example 10 was slightly lowered.

(10) Test example in which water was varied Example 13 to 16 and Comparative Examples 7 and 8 4 parts by weight (Example 13) and 5 parts by weight (Example 13) of water (6 parts by weight) in Example 1 were used. 14), 7 parts by weight (Example 1)
5), 8 parts by weight (Example 16), 3.5 parts by weight (Comparative Example 7) and 8.5 parts by weight (Comparative Example 8), except that the amounts were varied, and a rigid foam was molded in the same manner as in Example 1. , Performance tests were conducted. As a result, good results were obtained when the amount of water used was 4 to 8 parts per 100 parts of the polyol. In Comparative Example 7, performances such as compressive strength were excellent, but the density was too high, and the material cost was high, so that a practical rigid foam could not be obtained. On the other hand, in Comparative Example 8, the density was greatly reduced, and other properties such as compression strength and dimensional stability were inferior, so that it could not be used as a practical rigid foam.

The results of the performance tests of the above Examples and Comparative Examples are summarized in Tables 5-7.

[0034]

[Table 5]

[0035]

[Table 6]

[0036]

[Table 7]

Example 17 Millionate MR-manufactured by the same Nippon Polyurethane Industry Co., Ltd. in place of the polymeric MDI in Example 8.
A rigid foam was molded as in Example 8 except that 200 and 300 were used. As a result, a rigid foam having almost the same performance as that of Example 8 was obtained. Incidentally, MR-200
And 300 have more polynuclear bodies having 3 or more functional groups than MR-100, and are said to have a low content of binuclear bodies having 2 functional groups.

Example 18 Using the foamable composition of Example 8, a high pressure injector (EMB
Inner dimension 50 using the product name "PU-80" manufactured by the company
A rigid foam was obtained by pouring and foaming into a mold of x900x1800 mm. The results of the performance test are as follows. Further, as a result of molding a sandwich panel using a 0.35 mm-thick color steel plate as a face material, a molded product having good adhesiveness could be obtained. Density (kg / m ³ ) 40.2 Compressive strength (kg / cm ² ) 1.5 Thermal conductivity (kcal / m-h- ° C) 0.0187 High temperature dimensional stability (thickness direction) ○ (right-angle direction) ○ Low temperature dimensional stability (thickness direction) ○ (right angle direction) ○ Surface brittleness ○

Example 19 Using the foamable composition of Example 8, a low pressure injection machine (air mixing type) was used to inject and foam into the same mold as in Example 18, to obtain a rigid foam. The results of the performance test are as follows. Further, as a result of molding the sandwich panel in the same manner as in Example 18, a molded product having good adhesiveness could be obtained. Density (kg / m ³ ) 39.6 Compressive strength (kg / cm ² ) 1.4 Thermal conductivity (kcal / m-h- ° C) 0.0194 High temperature dimensional stability (thickness direction) ○ (right-angle direction) ○ Low temperature dimensional stability (thickness direction) ○ (right angle direction) ○ Surface brittleness ○

According to the results of the above Examples and Comparative Examples,
It can be seen that the use of polyisocyanate and a specific type and amount ratio of polyol and a specific amount of water to generate carbon dioxide gas results in a rigid foam with excellent performance. It is also understood that the presence or absence of components such as a flame retardant, a plasticizer, a diluent and the molding method of the rigid foam do not significantly affect the performance of the obtained rigid foam. The present invention is not limited to the specific examples described above, and various modifications may be made within the scope of the present invention depending on the purpose and application.

[0041]

According to the method for producing a rigid polyurethane foam of the present invention, a method of using carbon dioxide gas as a blowing agent, which has hitherto been considered difficult by using a polyol of a specific type and a specific ratio and water in a specific amount. Thereby, a practical rigid foam having excellent performance can be obtained. The effects of the present invention and the properties of the rigid foam obtained thereby are summarized below. (a) It is a technology that does not cause environmental damage by using no blowing agent that causes ozone layer depletion and global warming, such as CFC, HCFC and HFC. (b) It has excellent mechanical properties, dimensional stability, and heat insulating properties, and can be used as various heat insulating materials and building materials, etc., similar to conventional rigid foams. (c) Since the surface brittleness is low and the adhesiveness with various surface materials is excellent, it is easy to form a composite with the surface material and can be widely used for various sandwich panels, electric refrigerators and the like. (d) Since molding can be performed under conditions that are not so different from conventional molding conditions, conventional molding equipment (foaming machine, molding die, heating jig, etc.) can be used as is. (e) In the present invention, since the same kind of raw material as the conventional raw material system is used, the raw material cost is low and the practicality is high. (f) The usable foam density range is wide and can be selected according to the intended use. It is also possible to mold large products.

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Claims (3)

[Claims] 1. When a rigid polyurethane foam is produced by using a foamable composition containing polyisocyanate, a polyol and water as a main component, when the total amount of the polyol is 100 parts by weight, the (A) hydroxyl value is 20 to 40 parts by weight of toluenediamine-based polyether polyol of 360 to 440, 40 to 60 parts by weight of (B) sorbitol-based polyether polyol of hydroxyl value of 200 to 260, and (C) hydroxyl value of 160 to 240. 10 to 30 parts by weight of the aromatic polyester polyol which is
A method for producing a rigid polyurethane foam, characterized in that 4 to 8 parts by weight of water is used with respect to 100 parts by weight of the polyol. 2. When the total amount of the sorbitol-based polyether polyol is 100% by weight, 30 to 10% by weight having a hydroxyl value of 320 to 380 and 70 to 90% by weight having a hydroxyl value of 160 to 240. The method for producing a rigid polyurethane foam according to claim 1, characterized in that a resin having a hydroxyl value of 200 to 260 is used. 3. The foamable composition according to claim 1, wherein one or more kinds selected from halogenated phosphoric acid ester, dialkyl phthalate and alkylene carbonate is used as a viscosity reducing agent. Of the rigid polyurethane foam of.