JPS6340651B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a rigid urethane foam that requires low foaming pressure 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 heat insulating 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 work. In order to overcome this drawback, the so-called "frosting method" was developed with the aim of performing foaming in two stages and reducing 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 into the piping system at room temperature and pressure, and after mixing both components, it is discharged in the form of foam with a foam density of 0.08 g/cm ³ or less, and after discharge. , is characterized by completing foaming at a foaming ratio of 2 times 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 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 a polyisocyanate, tolylene 2.4-
Diisocyanate, tolylene 2.6-diisocyanate and mixtures thereof, diphenylmethane-
All those commonly used in the production of rigid urethane foams, such as 4.4'-diisocyanate, 3-methyldiphenylmethane 4.4-diisocyanate, and crude products thereof, can be used, but 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, trimethylolpropane, 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, monochlorodifluoroethane,
In addition to dichlorotetrafluoroethane, the boiling point is 5℃
The following can be used:

The above 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 amount of agent supplied and put the stock solution into the mold until the foam density is 0.08.
Discharge in the form of foam of less than g/cm ³ . After discharging the stock solution, when both components of the stock solution react and harden, some water contained in the polyol component reacts with the polyisocyanate to generate carbon dioxide gas, which becomes a foaming agent and starts secondary foaming.

Generally, polyols contain about 0.05% water, so within this range of water content,
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, the foaming ratio of the secondary foaming after discharging the stock solution was 2.
If it is less than 2 times, it is advantageous in that it does not substantially give excessive resistance to the mold surface, but rather allows the expansion of the stock solution to fill the foam to the corners of the mold and form a uniform foam.

As described above, the present invention suppresses the foam density of the stock solution discharged in the form of foam to 0.08 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 0.04 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 (molecular weight 400)
100 Silicone foam stabilizer (SH-193) 1 Amine catalyst (KL-NOI) 1 Flame retardant (TCEP) 10 Add dichlorodifluoromethane (R-12) to the piping system for liquid A and liquid B in the above formulation. ) (bp−29.8
℃) was injected at a rate of 13% for each liquid volume.

Thereafter, both liquids were discharged in the form of foam from the mixing head. The density of the discharged foam is approximately 0.07
g/ ^cm3 . Thereafter, the foam was expanded approximately twice as much to obtain a foam with a density of 0.038 g/cm ³ .

Example 2 Dichlorodifluoromethane was mixed into liquid A and liquid B with the same formulation as in Example 1 under the same conditions as in Example 1, and a foaming machine with a discharge rate of 5 kg/min was used to form a foam with a width of 300 m/m. , thickness 75m/m, height 2400m/m
200 mm from the bottom of the vertical mold
The stock solution was injected through an injection hole opened at a height of m/m. The stock solution is in the form of foam with a foam density of approximately 0.07 g/cm ³ and is filled to a height of 130 m/m from the bottom of the mold.
Thereafter, the foam was further expanded to completely fill the upper space.

The overall density of the filled foam was 0.037 g/cm ³ and the density of the core foam was 0.034 g/cm ³ .

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. A method for producing a rigid polyurethane foam, which is characterized in that after mixing both components, the foam is discharged in the form of a foam having a foam density of 0.08 g/cm ³ or less, and after discharge, foaming and curing is completed at a foaming ratio of 2 times or less.