JPH05186629A - Urethane foam - Google Patents

Abstract

PURPOSE:To produce an urethane foam of reduced thermal conductivity, suitably protecting global environments, by adding a specific amount of a foaming agent of fluorocarbon to the major components of a polyisocyanate and a polyol, and foaming the mixture. CONSTITUTION:Isocyanate and polyol as the major components are combined with a foaming agent of hydrochlorofluorocarbon and further less than 5.5wt.%, based on the polyol, of a fluorocarbon, when needed, stabilizers, water, or the like are added, then the mixture is foamed to give the objective urethane foam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a urethane foam used as a heat insulating material such as a heat insulating wall of a refrigerator.

[0002]

2. Description of the Related Art For example, a urethane foam used for a heat insulating wall of a refrigerator includes a first component made of isocyanate,
Produced by injecting a urethane undiluted solution obtained by stirring and mixing a second component obtained by adding a foaming agent, a stabilizer, a catalyst, etc. to a polyol into the outer shell, and foaming the urethane undiluted solution in the outer shell. Has been done. In this case, conventionally, as a foaming agent, Freon 11 (hereinafter referred to as “CFC-11”) is used.
CFCs such as) were used.

In recent years, however, it has been pointed out that the release of CFCs into the atmosphere adversely affects the ozone layer in the stratosphere, and from the viewpoint of protecting the global environment, it can also be used as a foaming agent for the above-mentioned urethane foam. It has been desired to switch from the conventional CFC to another.

[0004]

Therefore, in recent years, hydrochlorofluorocarbons have been used as alternatives to CFCs.
For example, it is considered to use HCFC-123 or HCFC-141b as a foaming agent. This compound has extremely low ozone depletion property and has a boiling point close to that of CFC-11.

However, the above HCFC-123 and H
CFC-141b has the above-mentioned CF having a thermal conductivity as a gas.
Since it is higher than that of C-11, deterioration of the thermal conductivity (heat insulating property) of the formed urethane foam by 3 to 10% is observed. Therefore, for example, when it is used as a heat insulating wall of a refrigerator, the thickness of the heat insulating wall must be increased as compared with the conventional urethane foam using CFC, and the thinning of the heat insulating wall which has been attempted in recent years is required. Would be in contradiction.

The present invention has been made in view of the above circumstances, and an object thereof is to protect the global environment by using hydrochlorofluorocarbon as a foaming agent, and to improve the heat insulating property. The purpose is to provide urethane foam that can

[0007]

In the urethane foam of the present invention, hydrochlorofluorocarbon is used as a foaming agent, and about 5.5% by weight or less of fluorocarbon is added to the urethane undiluted solution. It is characterized by

[0008]

[Function] For example, HCFC-123 and HCFC-141b
Even if it is released into the atmosphere, since it is decomposed into a non-toxic substance before reaching the ozone layer, it does not adversely affect the ozone layer and also has a boiling point. It is close to freon.
Therefore, from the viewpoint of protecting the global environment, it is suitable for use as a foaming agent in place of CFC.

However, since this hydrochlorofluorocarbon has a higher thermal conductivity as a gas than chlorofluorocarbon, a urethane foam using this as a foaming agent has a drawback of high thermal conductivity.

The inventors of the present invention have conducted various experiments on how to reduce the thermal conductivity of a urethane foam using hydrochlorofluorocarbon as a foaming agent.
As a result of repeated research, in the urethane stock solution, for example, C5 F12
By adding fluorocarbons such as (perfluoropentane) and C6 F14 (perfluorohexane), the thermal conductivity of the urethane foam to be formed can be reduced to the same level as that of the conventional one using freon as the foaming agent. The inventors have found that the above can be achieved and completed the present invention.

That is, according to the research by the present inventor, by adding fluorocarbon, it is possible to promote the miniaturization of the bubbles generated in the urethane foam and increase the number of the bubbles, thereby blocking the radiant heat. It is considered that the degree of heat treatment was increased and the thermal conductivity of the urethane foam was suppressed to a low level.

In this case, an appropriate amount of fluorocarbon added is about 5.5% by weight or less based on the weight of the polyol, and if it is added in excess of this amount, the thermal conductivity is increased. It is considered that when the amount of fluorocarbon added is increased, the miniaturization of the bubbles is further promoted, but the thermal conductivity of the fluorocarbon itself is high, and thus the heat insulating property of the urethane foam as a whole is deteriorated.

As equipment for producing the urethane foam of the present invention, it is possible to use conventional equipment as it is, and also when adding fluorocarbon to the urethane stock solution, a special auxiliary agent or No additives are needed.

[0014]

EXAMPLE An example in which the present invention is applied to a urethane foam used as a heat insulating material for a heat insulating wall of a refrigerator will be described below. Example 1 and Example 2 are urethane foams as described in the claims, which are prepared by foaming and polymerizing a urethane stock solution containing isocyanate and a polyol as main components and a foaming agent added. Has been formed.

Then, as shown in detail in Table 1 to be described later, the urethane stock solution does not contain CFC at all,
A proper amount of hydrochlorofluorocarbon is contained as a foaming agent, and it is about 5.5 with respect to the weight of the polyol.
% Or less by weight In this case, 1% by weight of fluorocarbon (perfluoropentane C5 F12) is added. As the hydrochlorofluorocarbon, HCFC-123 is used in Example 1, and HFC is used in Example 2.
CFC-141b is used.

The urethane foams of Examples 1 and 2 were manufactured as follows. That is, the urethane stock solution is, in detail, a first
It is composed of a component and a second component in which various additives are added to and mixed with the polyol, and the first component and the second component are housed in separate work tanks. In this case, the second component is formed by adding a predetermined amount of the foaming agent, a stabilizer called silicone oil, a catalyst such as water and amines, and the fluorocarbon to the polyol. It should be noted that it is desirable that the second component be kept in a stirring state in the work tank at all times.

Then, the first and second components are taken in from the two work tanks at a predetermined ratio by an injection device, and they are stirred and mixed, and a predetermined amount of the urethane undiluted solution is supplied to a heat insulating box of a refrigerator. It is injected into the outer shell that becomes the outer shell of. As a result, various polymerization reactions centered on the urethane bond between isocyanate and polyol proceed in the outer shell, and the heat generated at this time causes the foaming agent to evaporate and become bubbles, thus leaving a large number of bubbles. The urethane foam is formed in a state of being filled in the outer shell.

Table 1 below shows the component composition of the urethane stock solutions in Examples 1 and 2 described above. In addition, Table 1 also shows the component composition of the urethane stock solutions of the conventional example and the reference example. Of these, the conventional example is CFC 11
Conventionally, (CFC-11) is used as a foaming agent, and in the reference example, hydrochlorofluorocarbon (HCF) is used as a foaming agent as an alternative to CFCs.
It has been considered in recent years to use C-123) alone. These conventional examples and reference examples can also be manufactured by the same method as the above method. In Table 1, the unit is% by weight (hereinafter, "P
bW (Parts by Weight) ”) is used.

[0019]

[Table 1]

According to the experiments and research conducted by the present inventor, it was confirmed that the urethane foams of Examples 1 and 2 have extremely excellent properties. Hereinafter, this excellence will be described with reference to the drawings.

That is, the conventional example using chlorofluorocarbon as the foaming agent is unsuitable for use because it has an adverse effect on the ozone layer when the fluorocarbon gas is released into the atmosphere. On the other hand, hydrochlorofluorocarbons such as HCFC-123 and HCFC-141b in Examples 1 and 2 and Reference Example are substances that are not toxic before reaching the ozone layer even if they are released into the atmosphere. Since it is decomposed into chlorofluorocarbons, it does not adversely affect the ozone layer and has a boiling point close to that of chlorofluorocarbon, so it is suitable for use as a substitute for conventional fluorocarbons.

The following Table 2 shows those fluorocarbons (CFC-1).
1) and HCFC-123, HCFC-141b, O
DP (ozone depletion potential) and GWP (global warming potential)
Is shown together with the boiling point and the thermal conductivity in gas. In addition, the boiling point and the thermal conductivity of fluorocarbon are also shown. From the viewpoint of protecting the global environment, it is necessary to set the ODP value to 1.0 or less.

[0023]

[Table 2]

However, as shown in Table 2, since these hydrochlorofluorocarbons have a slightly higher thermal conductivity as a gas than fluorocarbons, the urethane foam of the reference example using this alone as a foaming agent has It had the drawback of high thermal conductivity. By the way, in the urethane foam of the reference example, the thermal conductivity (heat insulating property) was deteriorated by 3 to 10% as compared with that of the conventional example.

Therefore, the inventors of the present invention have conducted various experiments and studies on how to reduce the thermal conductivity of a urethane foam using hydrochlorofluorocarbon as a foaming agent, and as a result, in the urethane undiluted solution. To C5 F
By adding fluorocarbon such as 12 (perfluoropentane) and C6 F14 (perfluorohexane),
It has been found that the thermal conductivity of the urethane foam formed can be reduced to the same level as that of the conventional example using freon as the foaming agent.

Here, the thermal conductivity of urethane foam is
It also depends on the diameter of the bubbles (in other words, the number of bubbles).
This is because, for example, the bubbles become smaller (the number of bubbles increases).
It is considered that this is because the degree of blocking the radiant heat increases in accordance with. In this case, the thermal conductivity λ of urethane foam suitable for use as a heat insulation wall of a refrigerator is about 0.0.
The temperature is 125 Kcal / mh ° C or less, and in the recent high-grade type (thin heat insulating wall thin type) refrigerator,
A material having a thermal conductivity λ of about 0.0120 Kcal / mh ° C. is used.

According to experiments and studies conducted by the present inventor, as shown in FIG. 3, the average foam diameter (cell diameter) of the conventional urethane foam is about 0.30 mm, and the thermal conductivity λ of the urethane foam is Is 0.0125 Kcal / mh ° C. or less, whereas urethane foam using hydrochlorofluorocarbon as a foaming agent has a cell diameter of about 0.20 mm or less, which is equivalent to the conventional example. It has been found that the thermal conductivity of urethane foam can be obtained to some extent.

As shown in FIGS. 1 and 2, even in the case of the urethane foam using hydrochlorofluorocarbon as the foaming agent, in Example 1 and Example 2 in which 1PbW of fluorocarbon was added to the urethane undiluted solution, The thermal conductivity of urethane foam λ
Was able to be kept small.

Specifically, in the urethane foam of Example 1, as shown in FIG. 1, by adding 1 PbW of fluorocarbon, the cell diameter can be made about 0.10 mm, and therefore the thermal conductivity λ About 0.0120 Kcal / m
could be h ° C. Further, in the urethane foam of Example 2, as shown in FIG. 2, the cell diameter is about 0.16 mm.
Therefore, the thermal conductivity λ is about 0.012.
It was possible to achieve 3 Kcal / mh ° C.

Next, the amount of fluorocarbon added was adjusted to about 5.5.
Verify the suitability of setting PbW or less. As described above, it was confirmed that the cell diameter can be reduced and the thermal conductivity λ of the urethane foam can be suppressed to a small level by adding fluorocarbon to the urethane undiluted solution, but what is the addition amount? The present inventors conducted further experiments as to whether is appropriate.

In this experiment, among the components of the urethane stock solution shown in Table 1 above, for the examples 1 and 2,
Urethane foams with various amounts of fluorocarbon added were formed, and the cell diameter and thermal conductivity λ of the urethane foams were determined. The experimental results are shown in FIGS. 1 and 2.

That is, FIG. 1 shows that HCFC-1 is used as a foaming agent.
Of the components of the urethane stock solution of Example 1 using No. 23,
The amount of fluorocarbon added (PbW) is 0, 0.5, 1,
FIG. 9 is a plot of cell diameter (upper row) and thermal conductivity λ (lower row) for nine types of urethane foams formed by changing the number to 2, 3, 4, 5, 6, 15. In addition, FIG. 2 shows the cell diameters and the cell diameters of the nine types of urethane foams formed by changing the addition amount of fluorocarbon in the same manner as the components of the urethane stock solution of Example 2 using HCFC-141b as the foaming agent. The thermal conductivity λ is plotted.

As described above, in a urethane foam used as a heat insulating wall of a refrigerator, it is necessary to set the thermal conductivity λ to 0.0125 Kcal / mh ° C. or less. To satisfy this, From these FIG. 1 and FIG.
The amount of fluorocarbon added needs to be about 5.5 PbW or less.

Thus, the peak on the lower limit side of the thermal conductivity λ is
The amount of fluorocarbon added appears in the range of 1 to 3 PbW, and as the amount exceeds, the cell diameter decreases, but conversely the thermal conductivity λ increases. this is,
When the amount of the fluorocarbon added is increased, the miniaturization of the bubbles is further promoted, but the thermal conductivity of the fluorocarbon itself is high (see Table 2), so that the thermal conductivity of the urethane foam as a whole is deteriorated. Conceivable.

Therefore, it can be said that an appropriate amount of the fluorocarbon added is about 5.5% by weight or less based on the weight of the polyol.

As described above, the urethane foams of Examples 1 and 2 in which hydrochlorofluorocarbon was used as the foaming agent and about 5.5% by weight or less of the fluorocarbon was added to the undiluted urethane solution based on the weight of the polyol. Is extremely useful in protecting the global environment as an alternative to the conventional urethane foam that uses CFCs.

According to the urethane foams of Examples 1 and 2, it was possible to sufficiently improve the thermal conductivity, which was a drawback of the urethane foams using hydrochlorofluorocarbon. As a result, even when used as a heat insulating wall of a refrigerator, it is possible to avoid increasing the thickness of the heat insulating wall, and it is possible to sufficiently cope with the thinning of the heat insulating wall which has been attempted in recent years. is there.

Further, although detailed description is omitted, as equipment for manufacturing urethane foam, equipment used in the case of using a conventional CFC can be used as it is, so that switching can be easily performed. It is also possible to obtain the advantage that no special auxiliary agent or additive is required when adding fluorocarbon to the urethane stock solution.

[0039]

As is apparent from the above description, according to the urethane foam of the present invention, hydrochlorofluorocarbon is used as the foaming agent, and the urethane stock solution contains
Since fluorocarbon is added in an amount of about 5.5% by weight or less based on the weight of the polyol, it is possible to protect the global environment and it is possible to improve the heat insulating property. Play.

[Brief description of drawings]

FIG. 1 is a diagram showing the cell diameter and the thermal conductivity of the urethane foam of Example 1 with respect to the amount of fluorocarbon added.

FIG. 2 is a graph showing the cell diameter and the thermal conductivity of the urethane foam of Example 2 with respect to the amount of fluorocarbon added.

FIG. 3 is a diagram showing a relationship between cell diameter and thermal conductivity.

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Claims (1)

[Claims] 1. A foamed urethane stock solution containing isocyanate and a polyol as main components and a foaming agent added, wherein hydrochlorofluorocarbon is used as the foaming agent, and the polyol is added to the urethane stock solution. A urethane foam comprising fluorocarbon in an amount of about 5.5% by weight or less based on the weight.