JPS62164709A - Production of polyurethane foam - Google Patents

Abstract

PURPOSE:To obtain a low-density polyurethane foam without causing scorching, by foaming a specified urethane foaming stock solution in an atmosphere of a reduced pressure. CONSTITUTION:A urethane foaming stock solution is obtained by mixing a polyol (e.g., polyether polyol) with an organic isocyanate (e.g., tolylene diisocyanate) and, optionally, an amine catalyst (e.g., triethylenediamine), a silicone oil, a tin catalyst (e.g., dibutyltin dilaurate), and a blowing agent (e.g., water). This solution is foamed. When it starts rising, the pressure is reduced so that the degree of vacuum may be at least 50mmHg, preferably, 100-500mmHg below atmospheric pressure, and the foaming is continued.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing polyurethane foam, and in particular to a method for obtaining low density polyurethane foam.

[Conventional technology]

Polyurethane foams are used in a wide variety of applications and are manufactured in a variety of products ranging from low-density products to high-density quantities depending on their intended use.

When manufacturing polyurethane foam, the conventional method for adjusting the density of the product is to increase or decrease the amount of blowing agents (mainly water) and blowing aids (low-boiling solvents such as trichloromonofluoromethane and methylene chloride). It is being done. Therefore, when producing high-density polyurethane foam, a large amount of water is used to perform foaming so as to increase the foaming ratio.

[Problem that the invention seeks to solve]

By the way, the foaming effect in the production of polyurethane foam is due to carbon dioxide gas generated by the reaction between organic incyanate and water, so in conventional production methods, the formulation of raw materials must be changed depending on the density of the desired product. In particular, in order to produce a low-density urethane foam, it is necessary to add a large amount of water as a blowing agent, which causes the following problems.

The first problem is that since a large amount of water and incyanate are reacted, the internal temperature of the foam becomes significantly high due to the heat of reaction, which tends to cause so-called scorch (discoloration due to burning). Therefore, scorch inhibitors must be added.

Further, the upper limit of the addition ratio of water is 6 to 7 parts by weight per 100 parts by weight of polyol, but in such a low density foam, the above-mentioned problems are noticeable and there is a risk of fire.

Second, gas loss increases due to increased usage of organic isocyanates, trichloromonofluoromethane, etc.
This results in a decrease in yield.

In view of the above circumstances, it is an object of the present invention to produce polyurethane foams of various densities, particularly low-density products, from a foaming solution having the same formulation.

[Means for solving problems]

In the present invention, instead of changing the formulation of the foaming stock solution, the density of the product is changed by changing the pressure of the foaming atmosphere.
I decided to m.

That is, the method for producing polyurethane foam according to the present invention uses polyol, organic incyanate, amine catalyst, silicone oil, tin catalyst, water as a blowing agent, physical property improvers such as pigments and fillers, and other materials commonly used in the production of urethane foam. A method for producing polyurethane foam by mixing raw materials selected from the ingredients used to prepare a urethane foam stock solution and foaming the urethane foam stock solution, which is characterized by foaming under a reduced pressure atmosphere. .

As each raw material component of the foaming stock solution in the present invention, those conventionally used can be used as they are.8 For example, as the polyol, polyether polyol or polyester polyol can be used. Further, as the organic isocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, polymeric MDI, naphthalene diisocyanate, etc. can be used.

In the present invention, the form of obtaining a predetermined reduced pressure atmosphere is as follows:
For example, the foaming container itself may be configured as a decompression chamber and suction may be performed using a pump, or the foaming container may be housed in a separately prepared decompression chamber to cause foaming.
Batch-type processes are easier to apply, but continuous processes can also be applied if a large-scale vacuum chamber is used.

The reduced pressure atmosphere in the present invention naturally varies depending on the formulation, the density of the target product, etc. Usually, the amount of reduced pressure from normal pressure is preferably approximately 50 wet taHg or more, and optimally the reduced pressure from normal pressure is approximately 50 taHg or more. The amount of pressure reduction is in the range of 100 to 500 mmHH.

In the present invention, the pressure may be reduced immediately after the foaming stock solution is injected, but preferably after the foaming reaction has started and the foaming stock solution has started to rise.

[Effect]

The foaming reaction itself in the present invention is exactly the same as the foaming reaction in conventional polyurethane foam production, and bubbles are formed by the action of carbon dioxide gas produced by the reaction of organic incyanate and water.

However, in the present invention, since the foaming effect of carbon dioxide gas is performed under reduced pressure, the effect is enhanced. That is, the formation of bubbles depends on the escape power of the carbon dioxide gas generated in the foaming stock solution, and this escape force is determined by the relative magnitude of the vapor pressure of the generated carbon dioxide gas with respect to the atmospheric pressure. Therefore, even if the total amount of carbon dioxide gas produced is the same and its partial pressure is the same, the lower the atmospheric pressure, the greater its escaping force. Moreover, since the generated carbon dioxide gas is easily vaporized, the ratio of effective effect on foaming is improved even if the amount of generated carbon dioxide remains the same.

In this way, even when a foaming stock solution with the same formulation is used, the foaming ratio is increased by improving the vaporization efficiency of the generated carbon dioxide gas and reinforcing its foaming action, and a low-density polyurethane foam can be obtained.

[Example] Polyether polyol 100.00 parts by weight (
Molecular weight 3000.3 functional, OH value 56) Triethylenediamine 0.08/1 normal ethylmorpholine Q, 5 tt silicone oil
1,4/1 dibutyltin dilaurate Q, 35 tt trichloromonofluoromethane
5. OttH204,0/1 tolylene diisocyanate) 53. Ott A polyurethane foam stock solution having the above-mentioned formulation was prepared, and polyurethane foam was produced in a batch manner as described below.

First, the foaming stock solution prepared above is poured into the foaming container 10 housed in the vacuum tank 11 shown in the attached drawing, and the lid of the vacuum tank is closed and sealed.Next, the foaming stock solution starts to rise. Then, the valve 12 was opened, and the pressure reduction tank 11 was communicated with the vacuum pump 13 to reduce the pressure in the pressure reduction tank by a predetermined amount. After completing foaming under this reduced pressure,
The air pipe 14 was opened to return the inside of the vacuum tank to normal pressure, and the polyurethane foam was taken out from the foaming container 10. In addition,
Whether or not foaming was being carried out under a predetermined reduced pressure was constantly monitored using a gauge 15 attached to the two reduced pressure tanks 11.

Reduce the pressure inside the tank 11 to 100 mmHg and 200 r.
arsHg.

300mmHg, 400mmHg, 500■■H
Polyurethane foam was produced using the method described above, and the properties of the products obtained in each case were investigated. Also,
As a comparative example, the same foaming stock solution was used under normal pressure, that is, the amount of pressure reduction was 0
(2) Foaming was carried out in the same manner using Hg, and the properties of the obtained product were investigated. These results are shown in Table 1 below.

As shown in the results in Table 1 above, it was possible to obtain various polyurethane foams with different densities using the same foaming stock solution. Furthermore, no scorch phenomenon was observed even at a low density of 0.0098 g/c+s''.

Furthermore, the skin layer on the surface of the Example amount was considerably thinner than that of the Comparative Example amount. This is because the pressure is reduced, so the oxygen partial pressure present in the atmosphere is low.

Therefore, it is presumed that the deterioration of surface properties caused by contact with oxygen during the foaming process was suppressed.

〔Effect of the invention〕

As detailed above, according to the present invention, various polyurethane foams with different densities can be produced from a foaming stock solution having the same formulation, and in particular, low-density polyurethane foams can be produced without causing the scorch phenomenon as in the past. It is a product that can be manufactured and has remarkable effects from WJ.

[Brief explanation of drawings]

The attached drawings are explanatory views of the foaming device used in the examples of the present invention. 10... Foaming container, 11... Decompression tank, 12...
・Vacuum valve, 13... Vacuum pump, 14... Air pipe, 15... Pressure gauge

Claims (1)

[Claims] By mixing raw materials selected from polyols, organic isocyanates, amine catalysts, silicone oils, tin catalysts, water as blowing agents, physical property improvers such as pigments and fillers, and other compounding components commonly used in the production of urethane foam. A method for producing polyurethane foam by preparing a urethane foaming stock solution and foaming the urethane foaming stock solution, the method comprising foaming under a reduced pressure atmosphere.