JPS6116282B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a rigid urethane foam that exhibits low foaming properties during foam formation and has excellent mechanical strength and heat insulation properties.

Rigid urethane foam has excellent heat insulating properties, mechanical strength, and strength, and is easy to process, so it has recently been used for a wide range of applications such as insulation materials, building materials, and furniture materials. In particular, the method of filling the space within a wall surface with foam by injecting an undiluted solution into the space within a panel or wall surface and causing foaming is widely practiced as an effective method that takes advantage of the self-adhesive properties of urethane.

However, when a hard urethane stock solution is injected and foamed in a certain space, the foaming pressure during foam generation is extremely high, so it is necessary to provide sufficient reinforcement to withstand the foaming pressure during injection. In order to overcome this drawback, the so-called "frosting method" was developed for the purpose of performing foaming in two stages to reduce the foaming pressure after discharging the stock solution. However, since this method also uses a polyol component mixed with a liquid secondary blowing agent at room temperature, it is unavoidable that after the urethane stock solution is discharged, it expands an additional 4 to 10 times, creating a considerable foaming pressure. Ta.

The present invention provides a method for producing rigid urethane foam by minimizing the foaming pressure after discharging the stock solution, and in which a polyisocyanate component, a polyether polyol component containing a reaction catalyst, a foam stabilizer, and other additives are mixed. A gaseous low-boiling point compound is injected in liquid form as a blowing agent at room temperature and pressure into the piping system, and both components are placed at the gun outlet with a tube that can maintain a pressure of 6 kg/cm ² or more at a liquid temperature of 25°C. After mixing in the attached mixing gun, the foam is discharged from the tip of the tube with a foam density of 0.04 g/cm ³ or less.
It is characterized in that it is foamed and cured at a foaming ratio of 0.03 g/cm ² or less to obtain a low-density foam with a final foam density of 0.03 g/cm 2 or less.

That is, in the present invention, a polyisocyanate component as a stock solution for urethane foam production, a polyol component made by mixing a polyol with a reaction catalyst, a foam stabilizer, and other additives, and a polyol component that is a gas at room temperature and pressure. A blowing agent consisting of a boiling point compound is used, and this blowing agent is pressurized into the piping system of both components, and the stock solution is discharged in the form of a foam.

As polyisocyanate, tolylene 2,4
-Diisocyanate, tolylene 2.6-diisocyanate and mixtures thereof, diphenylmethane-
4,4'-diisocyanate, 3-methyldiphenylmethane 4,4-diisocyanate, 3-methyldiphenylmethane 4,4-diisocyanate, and crude products thereof, all of which are normally used in the production of rigid urethane foams. Crude diphenylmethane-4,4'-diisocyanate is particularly preferred.

The amount of polyisocyanate used is such that the equivalent ratio of isocyanate groups to hydroxyl groups (NCO/OH) is 1.0 to 1.2.
Use at a ratio of

As the polyol, polyether polyol is preferred. Specifically, sucrose, sorbitol,
There are polyether polyols using glycerin, trimethylolepropane, pentaerythritol, hexanetriol, ethylenediamine, triethanolamine, etc. as initiators.

The reaction catalyst, foam stabilizer, flame retardant, additives, etc. are the same as those used in the production of general urethane foam. The blowing agent used in the present invention is a low-boiling compound that is a gas at room temperature and pressure, such as dichlorodifluoromethane, monochlorodifluoromethane,
In addition to dichlorotetrafluoroethane, the boiling point is 5℃
The following can be used:

The above-mentioned polyisocyanate component and polyol component are each housed in a pressure-resistant container, and a foaming agent is press-fitted into the piping system that sends each component to the nozzle of a foaming machine to uniformly mix each component system and foam. Adjust the supply amount of agent and fill the stock solution into the mold with foam density.
Dispense in the form of foam of 0.04g/ ^cm3 or less. After dispensing the stock solution, when both components of the stock solution are discharged and cured, gas expansion due to exothermic reaction and some water contained in the polyol component reacts with the polyisocyanate to generate carbon dioxide gas, which becomes a blowing agent. Start secondary foaming.

Generally, polyols contain about 0.05% water, so within the range of this amount of components,
Next foaming is performed, and after discharge, secondary foaming is performed at a foaming ratio of 2 times or less to complete foaming and curing.

Therefore, if the polyol contains excess water, it should be dehydrated to reduce the water content.
Adjust to 0.05% or less. Although it is desirable to cure the raw solution as it is without secondary foaming after discharging it in the form of foam, in order to eliminate secondary foaming, it is necessary to completely dehydrate the water contained in the polyol.

However, if the foaming ratio of the secondary foaming after discharging the stock solution is 2 times or less, it will not substantially give excessive resistance to the mold surface, but rather the foam will be filled to the corners of the mold due to the expansion of the stock solution, creating a uniform foam. It is advantageous in that it can be formed.

As described above, the present invention suppresses the foam density of the stock solution discharged in the form of foam to 0.04 g/cm ³ or less and the foaming ratio after discharge to 2 times or less, so the foaming pressure during foam generation is extremely low, and the foam does not flow into the panel. Injection foaming and injection foaming into walls do not require strong reinforcing materials, and a uniform foam can be formed over the entire mold surface, simplifying the equipment required for construction and greatly improving work efficiency. You can improve your skills. Further, according to the present invention, a rigid polyurethane foam having a final foam density of 0.03 g/cm ³ or less and excellent heat insulation properties and mechanical strength can be obtained.

Examples of the present invention will be described below.

Example 1 Part A Crude diphenylmethane 4,4-diisocyanate 112 parts Part B Glycerin-based polyol 100 (molecular weight 400) Silicone foam stabilizer (SH-193) 1 Amine catalyst (KL-NOI) 1 Flame retardant (TCEP) 10 Above Add dichlorodifluoromethane (R-12) (bp-29.8) to the piping system for prescription liquids A and B.
℃) was injected at a rate of 1.3% for each liquid volume.

After that, pour both liquids into the outlet of the gun with an inner diameter of 2m/
The mixture was mixed in a mixing gun equipped with a 1 m long tube and discharged in the form of foam from the tip of the tube. The density of the discharged foam was approximately 0.037 g/cm ³ . After that, it is foamed to approximately 1.6 times the density.
A foam of 0.024 g/cm ³ was obtained.

Claims (1)

[Claims] 1. A gaseous low-boiling compound is pressurized in liquid form as a blowing agent at room temperature and pressure into the piping system of the polyisocyanate component and the polyether polyol component, which is a mixture of the reaction catalyst, foam stabilizer, and other additives. After mixing both components in a mixing gun equipped with a tube at the gun outlet that can maintain a pressure of 6 kg/cm ² or more at a liquid temperature of 25°C, a foam with a foam density of 0.04 g/cm ³ or less emerges from the tip of the tube. 1. A method for producing a rigid urethane foam, the method comprising: discharging the foam at a foaming rate of 2 times or less, and curing the foam at a foaming ratio of 2 times or less to obtain a low-density foam having a final foam density of 0.03 g/cm ² or less.