KR100276668B1 - Process for producing rigid polyurethane foams - Google Patents

Abstract

The present invention provides a method for producing a rigid polyurethane foam by reacting a polyisocyanate with a polyol in the presence of a catalyst and a blowing agent, which method comprises: (1) the blowing agent is substantially free of water and has a boiling point of 20 ° C. or less; It is a mixture of a low boiling point foaming agent and a liquid blowing agent at room temperature, and (2) provides a method for producing a rigid polyurethane foam having excellent thermal insulation characteristics, characterized in that carried out in the presence of a primary amine or a secondary amine.

The present invention does not have a problem of deterioration of thermal insulation properties due to the generation of carbon dioxide gas, and it is possible to obtain a rigid polyurethane foam having excellent thermal insulation properties without having a problem of lowering the foaming rate and lowering the dimensional stability of the urethane foam due to temperature change. do.

Description

Process for producing rigid polyurethane foams

The present invention relates to a method for producing a polyurethane foam, and more particularly to a method for efficiently producing a rigid polyurethane foam using a blowing agent without substantially using water.

Rigid urethane foams, used in a variety of applications, including refrigeration units, have been prepared by reacting polyisocyanates with active hydrogen-containing materials in the presence of blowing agents. The blowing agent is typically an organic compound which becomes a gas at the boiling point of the blowing agent to make a foam having a closed cell structure. Particularly, the halocarbon blowing agent used in the manufacture of rigid polyisocyanate-based foams is characterized by the thermal insulation properties of the foam as well as the foam. It also gives the same physical properties. The most commonly used halocarbons include CFC-11, CFC-12 and CFC-113, which are also used as refrigerants.

Some of these halocarbons, represented by chlorofluorocarbons (CFCs), have recently been exposed to environmental problems. Instead, a method of producing polyurethane foam using water has been proposed.

Water reacts with isocyanates to generate carbon dioxide, which causes the reaction mixture to expand and have a cell structure. Water may be useful in the manufacture of flexible polyurethane foams, but in the case of rigid polyurethane foams the physical properties and cell structure of the resulting foam are poor in quality and expensive isocyanates are large. There is a problem that is consumed, not practical.

In the method of preparing a rigid polyurethane foam using a water and a blowing agent, as shown in the following formula 1, the carbon dioxide gas and blowing agent generated by the reaction of water with polymethyl polyphenyl diisocyanate ("MDI") By utilizing the property that phosphorus cyclopentane is vaporized, a rigid urethane foam having a closed cell is produced. Urethane foam prepared in this way is used in refrigerators or other products requiring heat insulation because of the excellent thermal insulation properties, the general thermal conductivity is 0.0160-0.0170 kcal / mhr.

(1) basic reaction of urethane

R-OH + R'- NCO → R'-NHCOOR

Polyol MDI Urethane

(2) reaction of water with MDI

HOH + R'- NCO → R'-NH2 + CO2

R'-NH2 + R ''-NCO → R ''-NHCONH-R '(urea)

R ''-NHCONH-R '+ R' ''-NCO → R '' '-NHCON (CONH-R') R '' (Buret)

As described above, rigid urethane foams prepared using a certain amount of water and a blowing agent have limitations in improving thermal insulation. The reason is that the carbon dioxide gas generated by the reaction of water and MDI has worse thermal insulation properties than the blowing agent. Therefore, when using a rigid urethane foam prepared using water and a physical blowing agent as a heat insulating material, there is a limit in reducing the power requirements of the refrigerator or other products requiring heat insulation.

In order to solve this drawback and improve the insulation performance of the insulation, a method of improving the insulation properties by removing carbon dioxide gas (which is generated by the reaction of water and MDI) that is poorer than the foaming agent or making the foam of the rigid foam very small is proposed. have. However, when water that generates carbon dioxide is not used, the foaming rate is lowered and the cost is increased, and the urea and burette produced by the reaction between water and MDI are eliminated. . In addition, if the bubble of the foam is reduced while using water, the heat insulating properties can be improved to some extent, but it is difficult to significantly improve the heat insulating properties.

Therefore, there has been a demand for an effective method for producing rigid polyurethane foam having excellent thermal insulation properties.

The present invention provides a method for producing a new rigid polyurethane foam that can prevent the degradation of the thermal insulation properties by carbon dioxide gas generated by the reaction of water and MDI.

The present invention also provides a method for producing a new rigid polyurethane foam that does not have a problem of lowering the foaming rate and the dimensional stability of the urethane foam with temperature changes that may occur due to the use of no water.

The method of the present invention is a method for producing a rigid polyurethane foam by reacting a polyisocyanate with a polyol in the presence of a catalyst and a blowing agent, which comprises: (1) a low boiling point blowing agent having substantially no water and having a boiling point of 20 ° C. or less; It is a mixture of a blowing agent that is liquid at room temperature, and (2) provides a method for producing a rigid polyurethane foam having excellent thermal insulation characteristics, characterized in that carried out in the presence of a primary amine or a secondary amine.

Hereinafter, the above objects, other objects and features of the present invention will be described in detail.

In the process of the present invention, the polyol is reacted with polyisocyanate in the presence of a blowing agent, which is substantially free of water (water content is 0.5% by weight or less of the total amount of the urethane raw material). When the water content exceeds 0.5% by weight relative to the total weight of the urethane composition, water and polyisocyanate react to generate carbon dioxide (CO ₂ ), which greatly affects the thermal insulation index of the urethane foam, so that the water content is 0.5% by weight. It is preferable that it is the following. Polyisocyanates that can be used to prepare rigid polyurethane foams include aromatic, aliphatic and cycloaliphatic polyisocyanates and mixtures thereof. Representative examples include m- or p-phenylene diisocyanate, toluene-2,4-diisocyanate, toluene-2,6-diisocyanate, hexamethylene-1,6-diisocyanate, tetramethylene-1,4-diisocyanate , Cyclohexane-1,4-diisocyanate hexahydrotoluene diisocyanate, naphthylene-1,5-diisocyanate, 1-methylphenyl-2,4-phenyl diisocyanate, diphenylmethane-4,4'-diisocyanate di Phenylmethane-2,4'-diisocyanate, 4,4'-biphenylene diisocyanate 3,3'-dimethoxy-4,4'-biphenylene diisocyanate and 3,3'-dimethyldiphenylpropane- Diisocyanates such as 4,4'-biphenylene diisocyanate; Triisocyanatues such as toluene-2,4,6-triisocyanate; Polyisocyanates such as 4,4'-dimethyldiphenylmethane-2,2'5,5'-tetraisocyanate, and various various polymethylenepolyphenylpolyisocyanates. Also crude polyisocyanates such as crude diphenylmethane diisocyanate obtained by phosgenation reaction of crude diphenylmethanediamine or toluene diisocyanate obtained by phosgenation reaction of toluene diamine mixture can also be used to prepare polyurethanes.

Particularly preferably used for preparing rigid polyurethane foams are polymethylene polyphenylpolyisocyanates.

Polyols that may be used in the present invention are, for example, polyether polyols such as sucrose-initiated polyols, sorbitol-initiated polyols, sucrose-glycerin initiated polyols, glycerin-initiated polyols, toluene diamine-initiated polyols, and the like. ; Polyester polyols, polyhydroxy-terminated acetal resins, hydroxy-terminated amines and polyamines. As the polyether polyol, one having an OH number (hydroxyl number) in the range of 200-750 may be used. Meanwhile, as polyester polyols, polyhydroxy-terminated acetal resins, hydroxy-terminated amines and polyamines, those described in US Pat. No. 4,394,491 can be used, and the OH value is about 50 to about 800, preferably Is in the range of about 50 to about 500.

The use ratio of polyisocyanate and polyol is based on 100 polyols and the amount of polyisocyanate is in the range of 100 to 200 depending on the OH value of the polyol.

A foaming agent is used to give a cell structure to polyurethane. In the present invention, the blowing agent is substantially free of water. Instead, if the foaming agent does not contain water, there may be a problem that the thermal insulation properties of the foam are deteriorated depending on the type of foaming agent. In order to solve this problem, a mixture of a low boiling point blowing agent and a blowing agent which is liquid at room temperature (about 20 ° C.) is used. Low boiling foaming agents include halogenated hydrocarbons or hydrocarbon blowing agents having a boiling point of about 20 ° C. or less, and low boiling halogenated hydrocarbons include methylene chloride, trichlorofluoromethane, dichlorodifluoromethane, trichloroethane and ethane-derived chlorofluoro Carbon is included. Specifically, the low boiling point blowing agent is one or a mixture of two or more selected from the group consisting of HCFC-22 (hydrochlorofluorocarbon-22), HFC-245fa (hydrofluorocarbon-245fa), HFC-134a, HFC-236ea, HCFC-142b and isobutane. This includes. On the other hand, isobutane is a low boiling point hydrocarbon blowing agent. The blowing agent liquid at room temperature is selected from CFC-11 (chlorofluorocarbon-11), HCFC-141b (hydrochlorofluorocarbon-141b, HFC-356 (hydrofluorocarbon-356), HFC-365, cyclopentane, isopentane or normal-pentane Or a mixture of two or more kinds The mixing ratio of the low boiling point blowing agent and the blowing agent liquid at ordinary temperature is in the range of 1 to 99:99 to 1 weight ratio, in particular 30 to 70:70 to 30. By mixing the liquid blowing agent in the above weight ratio, the azotropy (boiling point of the azeotropic mixture) of the mixed blowing agent is maintained at 15 to 30 ° C., preferably 20 to 25 ° C., which maintains a gaseous state and is easy to handle at room temperature, After urethane foam hardening, foam shrinkage can be prevented in the foam cell structure and heat insulation effect can be enhanced.

One or two or more catalysts may advantageously be used in the reaction of the polyol and polyisocyanate. Urethane catalysts can be suitably used, for example tertiary amine compounds and organometallic, in particular organotin compounds are advantageously used.

Primary amines used in the present invention include two or more amino groups in a molecule, and include, for example, propylenediamine, triethylenediamine, amineethylpiperazine, methylenetriamine, methylphenyldiamine, and the like. As having two or more amino groups and one hydroxy group in the molecule, for example, methylphenylhydroxydiamine, toluenehydroxydiamine or hydroxyethylpiperazine, etc. may be representatively exemplified, but not limited thereto. These primary or secondary amines are used in an amount of 0.5 to 10 parts by weight based on 100 parts by weight of polyisocyanate, and 0.5 to 5 parts by weight of the primary amine, and 1 to 10 parts by weight when using the secondary amine It is used in an amount, because the use of less than 0.5 parts by weight of the primary amine, or less than 1 part by weight of the secondary amine, the relatively small amount of urea and burette generated in the reaction with the isocyanate promotes foam shrinkage, thereby promoting high temperature. The result of high humidity and low temperature dimensional change is bad, and when using more than 5 parts by weight of primary amine or more than 10 parts by weight of secondary amine, the reaction with isocyanate with excess amine is relatively more active than with polyol This is because the reaction temperature rises rapidly in the early stages, and the reaction rate is increased, and foams become entangled with each other, making foaming impossible.

When preparing rigid polyurethane foams it is generally advantageous to add small amounts of surfactants to stabilize the reaction mixture until the foamed reaction mixture becomes rigid. As such surfactants, liquid or solid organosilicon compounds may be advantageously used, and polyethylene glycol ethers of long chain alcohols, long chain alkyl acid sulfate esters, alkylsulfonic acid esters, alkanolamine salts of alkylarylsulfonic acids or tertiary amines may also be used. Can be. Such surfactants are used in amounts sufficient to stabilize the foamable reaction mixture and form large, homogeneous cells. Typically it can be used in an amount of about 0.2 to about 5.0 parts by weight based on 100 parts by weight of the polyol component.

The above-described components can be used to prepare a rigid polyurethane foam having excellent thermal insulation. That is, the polyol is reacted with the polyisocyanate in the presence of blowing agents, catalysts, surfactants and additives. This reaction can proceed according to conventional methods, for example by a so-called "one-step" process in which all the components are reacted at once or the so-called "quasi-prepolymer method". ) ". According to the one-step process, foaming takes place in the reactor, where each component is injected into the mixing head, where it is mixed with polyisocyanate to form a polyurethane-foaming mixture. This mixture can be poured into a suitable container or shaped as required. In another, quasi-prepolymer process, some of the polyol components are reacted with the polyisocyanate component in the presence of a catalyst such that about 10-30% of free isocyanate groups are present in the reaction product. The remaining amount of polyol can then be added and all components reacted in the presence of other suitable components such as catalysts and blowing agents.

In general, the above-mentioned raw material may be injected into a mold having a temperature of 35-50 ° C., cured for about 4-6 minutes, and then demolded to prepare a urethane foam.

Rigid polyurethane foam with excellent thermal insulation properties produced by the method of the present invention can be usefully applied as a heat insulating material in refrigerators and freezers.

Hereinafter, the method of the present invention will be described in more detail with reference to various examples, but the present invention is not limited to these examples.

Example 1-2 and Comparative Example 1-6

The rigid polyurethane foam of Comparative Example 1-6 and Example 1-2 was obtained using the composition shown in Table 1 and Table 2. Foam was prepared using a high pressure mixable Krasmafisa high pressure foamer. All components were adjusted to 20 ° C. before mixing. Various physical properties of the obtained foam were measured, and the results are shown in Table 1. The amounts used of all the components in Table 1 and Table 2 are based on 100 parts by weight of isocyanate (MDI).

Comparative Example 1 Comparative Example 2 Comparative Example 3 Example 1 Example 2 Polyol A ¹ 100 100 B ² 100 100 100 catalyst PMDETA ³ 0.5 0.3 0.3 0.3 0.3 DMCHA ⁴ 0.6 0.8 1.5 1.0 1.3 PC-41 ⁵ 0.5 0.7 0.8 0.8 0.8 Amine MDA ⁶ - - - 3 - HEP ⁷ - - - - 5 Surfactants ⁸ 2.0 2.0 2.0 2.0 2.0 Cyclopentane 14.5 15.5 22 18 18 water 2.2 1.0 - - Low Boiling Agent ⁹ - - - 4-8 4-8 MDI / Polyol Ratio 100/123 100/115 100/105 100/100 100/100 Injection rate 100 110 118 105 105 K-factor ¹⁰ 0.0160 0.0155 0.0152 0.0146 0.146 Low Temperature Change Rate (%) ¹¹ 1.3 1, .3 Shrink 1.2 1.2 High Temperature and Humidity Change Rate (%) ¹² 6.8 6.5 10.4 7.7 7.7 DESCRIPTION OF SYMBOLS 1: polyether polyol 2: polyether polyol 3: pentamethyldiethylenetriamine 4: dimethylcyclohexylamine 5: tertiary amine catalyst from Air Porducts 6: primary amine (methylphenyldiamine) 7: secondary amine (hydroxy Ethyl piperazine) 8: Silicone oil 9: HFC-134a10: kcal / m ° Chr: Index indicating insulation performance 11: -30 ° C x 24 hours 12: 70 ° C x 95% RH x 24 hours

Comparative Example 4 Comparative Example 5 Comparative Example 6 Polyol A - - - B 100 100 100 catalyst PMDETA 0.3 0.3 0.3 DMCHA 1.0 0.5 0.5 PC-41 0.8 0.8 0.8 Amine MDA 0.2 7.0 - HEP - - - Surfactants 2.0 2.0 2.0 Cyclopentane 18 18 - water - - - Low Boiling Agent 4-8 4-8 29 MDI / Polyol Ratio 100/100 100/100 100/98 Injection rate 110 Can't fire 106 K-factor 0.0151 Can't fire 0.0154 Low Temperature Change Rate (%) 2.3 Can't fire 1.03 High Temperature & Humidity Change Rate (%) 10.9 Can't fire 12.3

In Comparative Example 1, water was used in an amount of 2.2 parts by weight based on 14.6 parts by weight of cyclopentane as a conventional method. In Comparative Example 2, the amount of water used was 1 part by weight in order to reduce the amount of carbon dioxide generated by the reaction between water and MDI, which causes deterioration of thermal insulation properties. In Comparative Example 3, water was not used at all, but a low boiling point foaming agent was not used. Did. On the other hand, Example 1-2 used a low boiling point blowing agent in an amount of 4-8 parts by weight without using water according to the method of the present invention.

Looking at the physical properties of the foam obtained in each example, it can be seen that the foam of Comparative Examples 1 and 2 has a limit in improving the thermal insulation (K-factor). The reason for this is that, as described above, the carbon dioxide gas has a poor thermal insulation property than the cyclopentane (cyclopentane 0.0113, carbon dioxide gas 0.0137).

On the other hand, in Comparative Example 3, which contains no water at all and does not contain a low boiling point blowing agent and an amine, the flow rate of the reaction mixture is decreased at the time of foaming, thereby increasing the injection amount by 18% or more, and finally forming the reaction between water and MDI. The lack of biurets resulted in very poor dimensional stability as the foam strength weakened. In addition, even if carbon dioxide whose K-factor is worse than cyclopentane is completely removed, the K-factor increases as the cyclopentane in the bubble is condensed under the low temperature of the foam.Theoretical value (theoretical K-factor value: 0.0138 or less) It can be seen that the characteristics are not improved.

On the other hand, in Examples 1 and 2 using a low boiling point blowing agent and a primary or secondary amine without containing water, the urea produced together with the production of urea during the reaction was converted into a burette by the amine, resulting in poor dimensional stability of the foam. It can be seen that the problem is completely solved. In addition, when water is not used, the problem that the thermal insulation property is not improved by the theoretical value due to the condensation of cyclopentane has been solved by using a low boiling point blowing agent. The K-factor could be improved to 0.0140 by the method of the present invention.

On the other hand, when a small amount of the primary amine was added in an amount of about 0.2 parts by weight, sufficient urea or burette was not produced, resulting in poor high temperature, high humidity, or low temperature dimensional change (Comparative Example 4). On the contrary, when the excess was used, the foams were entangled with each other during mixing of the foam mixture and foaming was impossible (Comparative Example 5). In addition, when only the low boiling point blowing agent was used alone without using the primary amine or the secondary amine, the foaming reaction did not normally occur, and thus a particularly bad result was obtained at high temperature and high humidity.

As described above, according to the method of the present invention, it is possible to impart excellent thermal insulation properties to the rigid polyurethane foam and at the same time not to cause other physical properties such as dimensional stability. A refrigerator manufactured by using the rigid polyurethane foam obtained by the method of the present invention as a heat insulator can obtain an effect of improving the refrigerator power consumption by 10% or more.

Claims (8)

In the process of producing a rigid polyurethane foam by reacting a polyisocyanate with a polyol in the presence of a catalyst and a blowing agent, the method (1) the blowing agent is substantially free of water, (2) the blowing agent is a mixture of a low boiling point blowing agent having a boiling point of about 20 ° C. or less and a blowing agent which is liquid at room temperature; (3) The reaction between the polyisocyanate and the polyol is carried out in the presence of a primary amine having two or more amino groups in the molecule or a secondary amine having two or more amino groups and one hydroxy group in the molecule. Method for producing polyurethane foam. The method of claim 1, wherein the low boiling point blowing agent is selected from the group consisting of HCFC-22 (hydrochlorofluorocarbon-22), HFC-245fa (hydrofluorocarbon-245fa), HFC-134a, HFC-236ea, HCFC-142b and isobutane; A mixture of two or more kinds. According to claim 1, wherein the blowing agent is liquid at room temperature CFC-11 (chlorofluorocarbon-11), HCFC-141b (hydrochlorofluorocarbon-141b, HFC-356 (hydrofluorocarbon-356), HFC-365, cyclopentane, isopentane or normal -One or two or more mixtures selected from pentane. The method according to claim 1, wherein the mixing ratio of the low boiling point blowing agent and the blowing agent which is liquid at ordinary temperature is 1 to 99:99 to 1 weight ratio. The method according to claim 2 or 3, wherein the mixing ratio of the low boiling point blowing agent and the blowing agent which is liquid at room temperature is 20 to 80:80 to 20 weight ratio. According to claim 1, wherein the primary amine is one or a mixture of two or more selected from propylenediamine, triethylenediamine, amineethylpiperazine, methylenetriamine or methylphenyldiamine, 0.5 parts by weight based on 100 parts by weight of polyisocyanate To 5 parts by weight. According to claim 1, wherein the secondary amine is one or a mixture of two or more selected from methylphenylhydroxydiamine, toluenehydroxydiamine or hydroxyethylpiperazine, 1 part by weight to 10 parts by weight based on 100 parts by weight of polyisocyanate Used in negative amounts. The method of claim 1, wherein the blowing agent is characterized in that the water content is 0.5% by weight or less of the total amount of the urethane raw material.