JPS6353208B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to a foamed heat insulating material made by mixing and foaming an isocyanate stock solution and a polyol stock solution, and particularly to a foamed insulation material with improved blowing agents and crosslinking agents. [Technical background of the invention and its problems] This type of foamed heat insulating material is used, for example, as a heat insulating wall of a refrigerator. In order to achieve this goal, improvements in insulation properties are eagerly awaited. By the way, conventionally, when manufacturing this type of foam insulation material, trichlorofluoromethane (hereinafter referred to as R-11) is used as a foaming agent, and other foam stabilizers and the like are also used to suppress the coarsening of bubbles. It was common to add Therefore, since it is effective to make the bubbles finer in order to improve the heat insulation properties, it is conceivable to increase the amount of the foam stabilizer added. However, since foam stabilizers have poor compatibility with polyols, there is a limit to increasing the amount added, and simply increasing the amount added will cause the strength of the foam insulation material to decrease as the cells become finer. In particular, shrinkage becomes large at low temperatures, causing problems such as cracks. On the other hand, in order to reduce manufacturing costs, it is effective to keep the foam insulation material to a low density and reduce the amount of raw solution used, so increasing the amount of foaming agent added to increase the foam rate may be considered. . However, if this is done, the bubbles become larger in diameter, which in turn causes a problem of deterioration of the heat insulation properties. Therefore, the reality has been that it has been extremely difficult to comprehensively achieve improvements in heat insulation, ensuring low-temperature strength, and reducing manufacturing costs.
It has also been considered to use R-12 in addition to R-11 as a foaming agent, but R-12 has an extremely low boiling point of approximately -30°C, so manual foaming is not possible, and it is difficult to foam under pressure. The disadvantage is that the stock solution and foaming agent must be mixed in the process, and that the mixing and injection equipment becomes quite large-scale, increasing manufacturing costs. [Object of the Invention] Therefore, an object of the present invention is to provide a foamed heat insulating material that can improve heat insulating properties, ensure low-temperature strength, and reduce manufacturing costs. [Summary of the Invention] The present invention contains trichlorofluoromethane (R-11) and dichlorotetrafluoroethane (hereinafter referred to as R-114) as blowing agents, and hydroxypropylated ethylenediamine or hydroxypropylated diethylenetriamine as a crosslinking agent. Or, it is characterized by containing both of these and a polyhydric alcohol. In the present invention, R-11 and R-
The reason for including 114 is as follows. R-11
The boiling points of R-114 and R-114 are 23.77°C and 3.55°C, respectively. Therefore, when an isocyanate stock solution and a polyol stock solution are mixed and stirred together with a blowing agent, R-114 having a low boiling point is immediately vaporized to quickly generate numerous fine bubbles, resulting in instantaneous creaming.
After this, when the temperature of the mixed liquid rises due to the reaction heat associated with the formation of urethane bonds, R-11 with a high boiling point begins to vaporize, resulting in the generation and growth of new bubbles.
The density of the mixed liquid progresses. This achieves finer cells and lower density of the foamed heat insulating material.
In addition, after foaming, the foamed insulation material contains R-114 gas, which has a high vapor pressure even at low temperatures, in its bubbles, so its vapor pressure can resist the shrinkage force of the foamed insulation material at low temperatures. can improve low-temperature strength. On the other hand, R-11 as a blowing agent
If only R-11 is used, creaming will not occur immediately after mixing because of the relatively high boiling point of R-11, and R-11 will be vaporized only after the temperature of the mixture increases due to the heat of reaction. Therefore, it takes time to cream the liquid mixture, and as a result, the bubbles become coarser than in the present invention, where creaming is instantaneous. In addition, at low temperatures, the vapor pressure of R-11 gas in the bubbles is relatively low, so this vapor pressure cannot be used to sufficiently resist the shrinkage force of the foam insulation, resulting in a decline in low-temperature strength. . Furthermore, if only R-114 is used as a foaming agent, the vaporization of R-114 not only contributes to creaming, but also causes problems such as excessive foaming pressure. Due to the poor compatibility with the polyol, R-114 separates from the polyol stock solution, resulting in the problem of difficulty in uniformly dispersing it. In addition, since R-114, which has a much higher boiling point than R-12, is used in addition to R-11, there is no need to mix the blowing agent under high pressure, and the mixing and injection of the stock solution The equipment is simplified. On the other hand, in the present invention, the reason why hydroxypropylated ethylenediamine, hydroxypropylated ethylenetriamine, or both of these and a polyhydric alcohol are contained in the crosslinking agent is as follows. In the first place, the purpose of adding a crosslinking agent is to generate crosslinks in the urethane foam, and the formation of these crosslinks improves the resin strength. Therefore, hydroxypropylated ethylenediamine or hydroxypropylated ethylenetriamine not only acts as a crosslinking agent, but since they are amine compounds, they exhibit autocatalytic properties in the initial polymerization reaction between the isocyanate stock solution and the polyol stock solution. ,
It increases its reactivity. Therefore, if one or both of the above-mentioned amines are contained as a crosslinking agent, many crosslinks will be formed immediately after the two stock solutions are mixed, and the resin strength will be increased at an early stage. It is possible to prevent the countless bubbles generated in the process from breaking the resin film and interconnecting each other, and it is possible to further ensure the miniaturization of the bubbles. In addition, as mentioned above, even if the resin film becomes thinner due to the miniaturization or lower density of the cells in the foam insulation material, the strength of the resin film itself increases due to its high reactivity, so the foam insulation material as a whole can be improved. Sufficient strength can be ensured, and furthermore, since the resin strength increases quickly, the time required for demolding the foamed heat insulating material can be shortened and productivity can be improved. By the way, if the above-mentioned hydroxypropylated ethylenediamine, hydroxypropylated ethylenetriamine, or both are added as a crosslinking agent to the stock solution in an amount that provides the necessary resin strength, the urethane foam can be stored in a refrigerator, for example. It is difficult to fill a relatively complex outer shell such as an insulated box. The reason for this is that the high reactivity resulting from the autocatalytic properties of both of the amines causes crosslinking to occur early, and the viscosity of the mixed stock solution increases rapidly, making it difficult to penetrate into narrow spaces. Regarding this point, if a polyhydric alcohol is included as a crosslinking agent in addition to the above-mentioned amines, the polyhydric alcohol contributes to the formation of crosslinks but does not have autocatalytic properties, so it may be prevented from excessive reactivity. This prevents the viscosity from increasing too early, and even when the mixed stock solution is filled into a complex-shaped shell, it can penetrate into every corner of the interior. Therefore, it is necessary to contain hydroxypropylated ethylenediamine, hydroxypropylated ethylenetriamine, or both of these as a crosslinking agent, and a polyhydric alcohol, thereby achieving sufficient resin strength without deteriorating the filling properties of the urethane foam. can be obtained. [Embodiment of the Invention] Next, an embodiment in which the present invention is applied to a heat insulating wall of a refrigerator will be described in comparison with a conventional example. First, the compositions of the isocyanate stock solution, polyol stock solution, blowing agent, crosslinking agent, and other auxiliary agents in the conventional example and the present example are as shown in Table 1.

[Table] Next, the stock solution, blowing agent, crosslinking agent, and auxiliary agent in the above table will be described in more detail. (1) Isocyanate stock solution A mixture of crude MDI (methylene diphenyl diisocyanate) and a prepolymer prepared by reacting crude TDI (tolylene diisocyanate) and a polyol component in advance is used. (2) Polyol stock solution Sugar-based, glycerin-based, and amine-based polyols are considered. In this example, a mixture of a sugar-based polyol and an amine-based polyol is used. (3) Blowing agent In the present invention, both R-11 and R-114 are contained as blowing agents. As mentioned above, since R-114 has a relatively low boiling point of 3.55°C, it instantly creams immediately after the two stock solutions are mixed, thereby making it possible to achieve finer bubbles.
In addition, the R-114 gas trapped in the bubbles of the foam insulation material after foaming has a relatively high vapor pressure even at low temperatures, so this vapor pressure resists the shrinkage tendency of the foam insulation material at low temperatures. can do. In particular, in this example, water was added as a CO ₂ generation source. (4) Crosslinking agent Hydroxypropylated diethylenetriamine (abbreviated as TA in Table 1) and glycerin are used as the polyhydric alcohol. As mentioned above, since the amine compound has autocatalytic properties, it increases the reactivity between the isocyanate stock solution and the polyol stock solution. As a result, the resin strength can be increased even at the time of creaming immediately after mixing, which prevents the resin film from being broken and the bubbles from becoming continuous, thereby further contributing to the miniaturization of the bubbles. Also,
Even after foaming is completed, the strength of the foamed heat insulating material can be established early to withstand internal foaming pressure, so productivity can be increased by shortening demolding time and manufacturing costs can be reduced. Furthermore, since the resin strength after foaming can be increased, the density of the foamed heat insulating material can be reduced, thereby reducing the amount of raw solution used and further contributing to lower manufacturing costs. On the other hand, as mentioned above, glycerin does not have autocatalytic properties, so it is possible to prevent the viscosity of the mixed stock solution from increasing early while ensuring sufficient resin strength. Foam can be filled. Further, it is desirable to add at least 1 part by weight of each of hydroxypropylated ethylene triamine and glycerin to 100 parts by weight of the polyol stock solution. (5) Foam stabilizer silicone compound, cationic surfactant,
Anionic surfactants or nonionic surfactants are suitable. These may be added to the isocyanate stock solution side, the polyol stock solution side, or both. In this example, a silicone compound was used. (6) Catalyst Examples include various amines, potassium oleate,
Metal salts such as stannous chloride and stannic chloride can be considered. The type and amount added are isocyanate stock solution,
Adjustment should be made to obtain an appropriate reaction rate depending on the type of polyol stock solution and crosslinking agent.
In this example, a combination was used in which the so-called gel time was 25 to 40 seconds. Now, the physical properties of the foamed heat insulating materials obtained in each of the above-mentioned Examples are shown in Table 2 together with those of the conventional examples.

〔Effect of the invention〕

In summary, the present invention uses R-11 as a blowing agent.
(trichlorotetrafluoromethane) and R-114
By containing (dichlorotetrafluoroethane), creaming after mixing of the stock solution is quickly carried out and bubbles are made finer. In addition, hydroxypropylated ethylenediamine, hydroxypropylated diethylenetriamine, or both of these and polyhydric By incorporating alcohol to increase reactivity, it is characterized in that it is possible to effectively miniaturize bubbles and improve resin strength while suppressing an excessive increase in viscosity of the mixed stock solution. This improves insulation properties by making the cells finer, improves resin strength, secures low-temperature strength due to the vapor pressure of R-114 in the cells, and shortens demolding time and lowers density due to improved resin strength. It is possible to reduce costs, and even when filling the mixed stock solution into the outer shell, it is possible to fill every corner of the inside, and the mixing and injection equipment for the stock solution and foaming agent is simplified. It has the effect of being able to

Claims (1)

[Claims] 1. An isocyanate stock solution containing an isocyanate component and a polyol stock solution containing a polyol component are mixed and foamed together with a blowing agent and a crosslinking agent, and contain trichlorofluoromethane and dichlorotetrafluoroethane as the blowing agent, and are crosslinked. A foamed heat insulating material containing hydroxypropylated ethylenediamine, hydroxypropylated diethylenetriamine, or both of these and a polyhydric alcohol as an agent.