JPH08183828A - Production of polyurethane foam - Google Patents

Abstract

PURPOSE: To produce a polyurethane foam having uniformity in cell diameter distribution. CONSTITUTION: The process comprises mixing at least two ingredients consisting of a polyisocyanate and a polyol and applying ultrasonic to the polyol before the mixing or to the polyisocyanate/polyol mixture.

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 a polyurethane foam, and more particularly to a method for producing a polyurethane foam having a uniform cell diameter distribution.

[0002]

2. Description of the Related Art Currently, polyurethane foam is a heat insulating material,
Widely used as a cushioning material. The properties of this polyurethane foam are highly dependent on its cell size. For example, it is known that the thermal conductivity of polyurethane foam is smaller as the cell diameter is smaller.

Conventionally, such a polyurethane is produced by mixing a liquid containing a polyisocyanate component, a liquid containing a polyol as a main component, a foaming agent, a catalyst and a foam stabilizer, and mixing them. . So-called CFCs and water were used as the foaming agent, and the cell size was adjusted depending on the amounts used. However, at present, the use of CFCs has been severely restricted from the viewpoint of ozone depletion. As a result, various methods have been proposed for controlling the cell size when producing polyurethane using only water as a blowing agent.

For example, in JP-A-57-125225,
Production of a polyurethane foam characterized by adding a silicone compound, an anionic surfactant, a cationic surfactant, a nonionic surfactant, etc. as a foam stabilizer to both the polyol component and the polyisocyanate component. A method is disclosed. In this method, the foaming reaction and the polymerization reaction proceed simultaneously by mixing the polyol component and the polyisocyanate component. In the process of this reaction,
The reaction of water with polyisocyanate generates carbon dioxide, forming a foam. At this time, the foam stabilizer controls the size of cells in the foam by the strength of its surface tension.

[0005]

However, polyols, particularly polyether polyols, used in the production of polyurethane have a high electron-donating property of the ether bond in the main chain, and therefore, the hydrogen bond with the water molecule used as the foaming agent is high. Form. As a result, water is unevenly distributed in the polyol. The uneven distribution of water, which is the foaming agent, in the polyol causes variations in the diameter and size of the cells formed during the foaming process, which contributes to the deterioration of the physical properties of the resulting polyurethane foam. The control of the cell diameter using the foam stabilizer is a passive control of the cell diameter that traps carbon dioxide released from the non-uniformly dispersed water, and the water distribution cannot be made uniform, It is not a fundamental solution. Further, the polyol component to which the foam stabilizer is added has a considerably high viscosity because it is a multi-component mixed system, and therefore it is difficult to uniformly disperse water as a foaming agent.

Further, in recent years, in the case of polyurethane foam used, for example, in vehicle seats, the density of the foam has been reduced from the viewpoint of weight reduction. In such a low-density foam, it is particularly necessary to make the cell size distribution uniform,
Foams having satisfactory physical properties have not been obtained by conventional methods.

The present invention breaks the hydrogen bond between the ether bond and the water molecule in the polyol main chain by applying a physical force to uniformly disperse the water in the polyol component. It is an object of the present invention to provide a method for producing a polyurethane foam having a uniform distribution.

[0008]

The present invention provides a method for producing a polyurethane foam in which at least two components of a polyisocyanate component and a polyol component are mixed, in the polyol component before mixing with the polyisocyanate component, or in the polyisocyanate component. An ultrasonic wave is applied to the mixture of the polyol components.

[0009]

[Function] Before the reaction between the polyol and the polyisocyanate,
By applying ultrasonic waves to the water in the polyol component, the hydrogen bond between the ether bond in the main chain of the polyol and the water can be broken, and the water can be uniformly dispersed in the polyol component. As a result, a polyurethane foam having a uniform cell size distribution can be obtained.

[0010]

[Supplementary Explanation of Means for Solving the Problems] In the present invention, the polyisocyanate is an aromatic type, alicyclic type, or a fatty acid having two or more isocyanate groups, which is conventionally used in the production of polyurethane foam. Group-based polyisocyanates, or mixtures or modified products thereof can be used. Examples thereof include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HMDI) and the like.

In the present invention, the polyol is a polyhydric alcohol having two or more hydroxyl groups, which is conventionally used in the production of polyurethane foam,
Glycol, polyester polyol, polyether polyol, etc., or a mixture thereof can be used. In addition, ethylene glycol, diethanolamine,
Triethanolamine and the like may be used with the polyether polyol.

In addition to these components, other components usually used in the production of polyurethane foam, such as catalysts, foam stabilizers and other additives may be used. As the catalyst, for example, a metal compound catalyst such as an organic tin compound that promotes a reaction between an active hydrogen-containing group and an isocyanate group, or a tertiary amine catalyst such as triethylenediamine can be used. As the foam stabilizer, for example, a silicone-based foam stabilizer and a fluorine-containing compound-based foam stabilizer can be used. Other additives include, for example, fillers, stabilizers,
Colorants, flame retardants and the like can be used. These additives are used in addition to the polyol component.

As described above, water is used as the foaming agent in the method of the present invention. Since this water is unevenly distributed, it is uniformly distributed in the polyol by applying a physical force by ultrasonic waves. As a means for applying ultrasonic waves, an ultrasonic vibrator, an ultrasonic cleaner, etc. can be used. The energy of this ultrasonic wave has a frequency of preferably 20 kHz or more, more preferably 50 kHz or more in order to uniformly disperse water molecules.
It has an output of 50 to 100W.

It is preferable to apply the ultrasonic wave to the polyol component immediately before mixing the polyol component and the polyisocyanate component. This is because, if left for a while after the application of ultrasonic waves, the uniformly dispersed water molecules are unevenly distributed in the polyol again due to hydrogen bonding. Further, since the polyol and the polyisocyanate immediately start the polymerization reaction after mixing, if ultrasonic waves are applied at a stage where foaming has progressed to some extent, the formed cells will be destroyed. Therefore, when ultrasonic waves are applied after mixing, it is preferable to carry out immediately after mixing.

[0015]

[Examples] 75 parts by weight of polyol A (a polyether polyol having an average molecular weight of 6000 and 3 average functional groups), 25 parts by weight of polyol B (a polymer polyol having an average molecular weight of 5000 and 3 average functional groups), 3.4 parts by weight of water, and foam stabilizer Agent (SZ1306) 1.
0 parts by weight, catalyst A (TABCO 33LV) 0.3 parts by weight, catalyst B
(Polycat 77) 0.25 parts by weight, catalyst C (Toyocat
ET) 0.05 part by weight was mixed to prepare a polyol mixture. Add 45g of this mixture to a beaker,
Put it in the tank of the ultrasonic cleaner whose temperature is adjusted to 25 ℃
Ultrasonic energy of 80 W was applied for 60 seconds. This mixture was mixed with 32.7 g of MDI (NCO% = 23.8%) and subjected to a foaming / polymerization reaction to obtain a polyurethane foam having a diameter of 120 mm and a height of 220 mm. For comparison, a polyurethane foam was produced in the same manner except that the above ultrasonic wave was not applied.

With respect to each of these foams, a test piece of the foam cut out from an arbitrary portion thereof was photographed with a scanning electron microscope (SEM). From the obtained photographs, the distribution of cell diameters was quantified with image analysis software. The results are shown in Table 1 below.

[0017]

[Table 1]

From this table, it is understood that by applying ultrasonic waves to the polyol mixture, a polyurethane foam having a small average cell diameter and a more uniform distribution can be obtained.

Furthermore, for these foams, 80 ° C
Heat-resisting compression set, ie, residual strain after 50% compression was measured. It was 7.1 when ultrasonic waves were applied, compared with 8.4 when ultrasonic waves were not applied, improving compression set (sag characteristic) by almost 15%. This is because the distribution of the cell diameter becomes uniform by the application of ultrasonic waves, the skeleton of the foam formed by the cells becomes more uniform, the dispersion characteristics of deformation stress are improved, and the load is shared by the entire foam, which results in stress concentration. It is considered that the local deformation decreased and the permanent set decreased.

[0020]

As described above, according to the present invention, it is possible to obtain a polyurethane foam having a uniform cell diameter distribution and uniform physical properties.

Claims (1)

[Claims] 1. A method for producing a polyurethane foam in which at least two components of a polyisocyanate component and a polyol component are mixed, ultrasonic waves are added to the polyol component before mixing with the polyisocyanate component or to the mixture of the polyisocyanate component and the polyol component. Applying a voltage.