KR20020030999A - A method for preparation of rigid polyurethane foam - Google Patents

Abstract

PURPOSE: Provided is a preparation method of hard polyurethane foam which has small independent foams in isotropic state, making high heat insulation property. The hard polyurethane foam is used in the freezer and the refrigeration, saving 5-10% of the electricity. CONSTITUTION: The method comprises: reacting polyisocyanate with polyether polyols containing aromatic polyols in the presence of a catalyst, a surfactant, water and 0.1-3.0wt.%(based on 100wt.% of the above polyols) of hydrofluorocarbon blowing agent(nucleating agent) with the boiling point not more than 60deg.C as the mixtures of liquid perfluorinated hexane with other perfluorinated alkanes. The above polyaromatic polyols with the hydroxyl group of 200-650 OH value are toluenediamine, methylenediphenyldiamine or bisphenol-A or the mixtures of these amines and polyaromatic ester polyols.

Description

A method for preparation of rigid polyurethane foam

The present invention is to prepare a rigid polyurethane foam by reacting a polyol with a polyisocyanate in the presence of a hydrofluorocarbon blowing agent or a cyclopentane blowing agent, a foaming agent, a catalyst and water, wherein a closed independent bubble of the foam is isotropic by adding a nucleating agent. The present invention relates to a method for producing a rigid polyurethane foam in which an isotropic cell is made and the size of the independent bubble is reduced to improve the performance of the solid material constituting the foam bubble and to provide excellent thermal insulation effect.

Conventionally, when producing rigid polyurethane foams, chlorofluorocarbon (CFC) -based trichlorofluoromethane, dichlorofluoromethane, etc. have been used as foaming agents, but they have a high environmental pollution that decomposes the earth's ozone layer or increases the greenhouse effect. Since they have been treated as substances and have been recently banned from manufacture and use, they must be replaced by substitutes. Therefore, hydrochlorofluorocarbons (hereinafter referred to as "HCFC") with little destruction of the ozone layer are used as blowing agents. In particular, in the case of a rigid polyurethane foam prepared using HCFC as a blowing agent, although the closed independent bubble size is 200 ~ 300㎛, the gas insulation index of the blowing agent itself is low to 0.0094㎉ / mh ℃ excellent thermal insulation effect (insulation index; 0.0144 Pa / mh ° C.) can be provided, and therefore, it is frequently used in places requiring heat insulation.

However, HCFC also has a small amount but has an ozone depletion effect, and its use is gradually decreasing.

On the other hand, the use of a blowing agent that does not affect the ozone layer has been recently proposed because of the above problems of HCFCs, and hydrocarbon blowing agents such as cyclopentane have been used as an example.

However, when the cyclopentane is used as a foaming agent in the production of the rigid polyurethane foam, the closed independent bubble size of the conventional rigid polyurethane foam produced is as large as 200 ~ 300㎛, gas insulation index is 0.0121㎉ / mh ℃ Since it is higher than CFC or HCFC, the thermal insulation effect of the rigid polyurethane foam is not excellent (insulation index; 0.0165㎉ / mh ° C.). Therefore, when the rigid polyurethane foam prepared by using the cyclopentane as a blowing agent is applied to a place requiring heat insulation, the thickness of the rigid polyurethane foam is large because the heat insulation must be maintained by increasing the heat insulation thickness.

Accordingly, the present inventors have been studied to solve the above problems, and as a result, to produce a rigid polyurethane foam by reacting the polyol and polyisocyanate in the presence of a hydrofluorocarbon blowing agent or cyclopentane blowing agent, foam stabilizer, catalyst and water. Therefore, if a nucleating agent is added, a very large number of fine nuclei are generated during the initial reaction in the production of the rigid polyurethane foam, so that almost the initial state can be maintained until the reaction is completed, so that the closed closed bubble size can be kept small. As a result, the present invention has been found to be able to provide a rigid polyurethane foam having excellent thermal insulation effect by improving the thermal insulation index of the foam to improve the thermal insulation performance of the solids constituting the foam bubbles, thereby significantly reducing the thermal conductivity index of the foam.

Accordingly, an object of the present invention is to provide a method for producing a rigid polyurethane foam having excellent thermal insulation effect.

In order to achieve the above object, the method for producing a rigid polyurethane foam according to the present invention, the polyol and polyisocyanate in the presence of a hydrofluorocarbon blowing agent or cyclopentane blowing agent, foam stabilizer, catalyst and water to react the rigid polyurethane foam In the preparation, it is characterized by using a nucleating agent (nucleating agent).

Hereinafter, the present invention will be described in more detail.

The present invention relates to a method of using a nucleating agent to prepare a rigid polyurethane foam by reacting a polyol and a polyisocyanate in the presence of a hydrofluorocarbon blowing agent or a cyclopentane blowing agent, a foaming agent, a catalyst, and water. In addition, since the closed independent bubble size of the foam can be made small, the thermal conductivity index of the urethane foam can be significantly lowered due to the radiation effect between the independent bubbles, thereby providing a rigid polyurethane foam having excellent thermal insulation effect.

In general, the performance of the heat insulating material follows the following formula (1).

Equation (1); λ _total = λ _gas + λ _solid + λ _radiation

In other words, λ _gas is the gas insulation index of the blowing agent present in the closed independent bubble of the rigid polyurethane foam, and occupies about 74% of the total insulation index (λ _total ) 100%, depending on the composition of the gas Receive. Therefore, the higher the gas content with a lower insulation index, the greater the insulation effect. [lambda] _solid is a heat insulation index of the urethane resin polymer component constituting the rigid polyurethane foam, and generally occupies about 10% of the total heat insulation index ( _total of λ _total ), and is affected by the density of the polyurethane foam. However, there is no big difference in the conventional rigid polyurethane foam, and generally excellent thermal insulation effect when the density is 30 ~ 40kg / ㎥. λ _radiation is a thermal insulation index caused by radiation between closed independent bubbles of a rigid polyurethane foam, which typically accounts for about 16% of the total insulation index (100% of _total λ), and is related to the closed independent bubble size of the rigid polyurethane foam. This is proportional to the closed bubble size.

Therefore, in order to significantly improve the performance as a heat insulating material of a rigid polyurethane foam prepared using a blowing agent such as HCFC or cyclopentane, the portion occupied by λ _radiation in Equation (1) must be remarkably improved. In order to reduce the size of closed independent bubbles, the insulation effect due to the contribution of λ _radiation can be improved by about 10 to 20%.

Thus, the present invention uses a nucleating agent in the manufacture of rigid polyurethane foam in order to improve the thermal insulation effect of the rigid polyurethane foam by reducing the closed closed cell size.

In general, in the manufacture of polyurethane foam, the nucleus is produced by gas diffusion due to instability of carbon dioxide and blowing agent generated by the reaction of water and isocyanate by the temperature rise derived from the heat of reaction of polyol and isocyanate and the heat of reaction of water and isocyanate. As the viscosity of the reactant increases, the internal pressure of the nucleus expands and grows.

However, when the nucleating agent is added, the polyol having a polarity and the nucleating agent having a nonpolarity do not mix well with each other to form a large number of nuclei during the initial urethane reaction. By reducing the surface tension of the independent bubbles to suppress the aggregation during growth, small independent bubbles remain in the final polyurethane foam. Therefore, when using a conventional polyether polyol of the prior art and adding a nucleating agent to produce a polyurethane foam, the size of the independent bubble becomes an average of 100 ~ 130㎛.

On the other hand, phase separation occurs due to the large specific gravity of the nucleating agent in the reaction product during the production of polyurethane foams. When using polyether polyols containing polyaromatic polyols as polyols, such phase separation can be maintained for a long time. The size of the independent bubble can be made smaller than in the case of use (independent bubble size; average 80 ~ 98㎛). In particular, when the polyaromatic polyol is used in an excessive amount (50 to 70 parts by weight based on 100 parts by weight of polyol), the size of the independent bubble can be further reduced, which is effective.

Although the kind of nucleating agent used by this invention is not specifically limited, For example, a boiling point is 60 degrees C or less, and is a liquid perfluoroalkanes, specifically, a perfluorinated nucleic acid or this and other perfluoroalkanes. The mixture is preferable, and when the amount is less than 0.1 part by weight, the effect is insignificant. When the amount is used in excess of 3.0 parts by weight, an excessive amount of nucleating agent is obtained, showing almost the same effect as that of adding 3.0 parts by weight in terms of thermal insulation effect. Since it tends to reduce the density of the foam by acting as some blowing agent, 0.1 to 3.0 parts by weight, preferably 0.5 to 1.0 part by weight, based on 100 parts by weight of polyol is used.

Meanwhile, in the method of the present invention, the nucleating agent is mixed with the blowing agent, the catalyst, the foaming agent, the water, and the polyol at once, or the additives except the nucleating agent are first mixed with the polyol to prepare the emulsion, and then the emulsion and the nucleating agent are mixed. Can be. The isocyanate and the nucleating agent may also be mixed and then reacted with a polyol emulsion containing various additives.

In the method of the present invention, other foam stabilizers, catalysts, polyols, polyisocyanates, etc., except for the nucleating agent, may be arbitrarily selected from those commonly used in the art, and in particular, when a polyaromatic polyol is used as the polyol, a hydroxyl group ( Toluenediamine polyol, methylenediphenylamine polyol, or bisphenol-A polyol having an OH value) in the range of 200 to 650, or a mixture of these and polyaromatic ester polyol may be used.

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated in detail, this invention is not limited only to these examples.

In order to obtain the results shown in Table 1, the foam specimens for measuring various physical properties of the rigid polyurethane foam were manufactured using a vertical mold (1,100 × 300 × 50 mm) and a high pressure foaming machine. On the other hand, the amount of all the components used was based on 100 parts by weight of polyol, the temperature of all the components before the foaming was adjusted to 20 ℃.

<Production method>

All the additives except the nucleating agent were first mixed with a polyol to prepare an emulsion, and then the emulsion and the nucleating agent were mixed to prepare a polyol emulsion, which was reacted with an isocyanate to obtain a polyurethane foam.

From Table 1, it can be seen that when adding 3 parts by weight of the nucleating agent to the conventional method for producing a polyurethane foam (Comparative Example 1) (Example 1), the size of the independent bubble is significantly reduced, and the thermal insulation index is also significantly lowered. have. However, it can be seen that it is not as effective as Examples 2 to 4 using an excessive amount of polyaromatic polyol.

Examples 2 to 4 used excessive amounts of polyaromatic polyols and 0.1 to 1.0 parts by weight of nucleating agent to significantly reduce the size of closed closed cells, and the thermal insulation index was also lowered to 0.0145 ~ 0.0149㎉ / m.hr. ° C. . However, in the case of Example 2 in which the nucleating agent was added in an amount of 0.1 parts by weight, the effect was insufficient compared with Comparative Example 2 in which the nucleating agent was not added.

Therefore, in order to provide a rigid polyurethane foam having excellent thermal insulation effect, it can be seen that the use of a nucleating agent in an amount of 0.5 to 1.0 parts by weight while using polyaromatic polyol in an excessive amount is advantageous in terms of thermal insulation effect compared to economics.

As described above, since the rigid polyurethane foam according to the present invention is manufactured using a nucleating agent, it is possible to improve the contribution of λ _radiation by reducing the size of the independent bubble, thereby significantly lowering the insulation index. Therefore, when the rigid polyurethane foam prepared by the present invention has excellent heat insulating effect as a heat insulating material of a product having a freezer and a refrigerator function, the amount of electric power consumption can be reduced by 5 to 10%.

Claims (4)

In preparing a rigid polyurethane foam by reacting a polyol with a polyisocyanate in the presence of a hydrofluorocarbon blowing agent or a cyclopentane blowing agent, a foaming agent, a catalyst and water, a nucleating agent is 0.1 to 3.0 parts by weight of the total polyol. A method for producing a rigid polyurethane foam, characterized in that used in parts by weight. The method according to claim 1, wherein the nucleating agent has a boiling point of 60 ° C. or less and is a liquid perfluorinated hexane or a mixture of it and other perfluoroalkanes. The method according to claim 1, wherein the polyol is a polyether polyol containing polyaromatic polyol. The polyaromatic polyol of claim 3, wherein the polyaromatic polyol is a toluenediamine-based polyol, a methylenedipetyldiamine-based polyol or a bisphenol-A-based polyol having a hydroxyl group in the range of 200 to 650, or a mixture thereof with a polyaromatic ester polyol. Manufacturing method.