JPS581691B2 - Method for manufacturing rigid polyurethane foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing rigid polyurethane foams suitable as thermal insulation materials.

Various plastic foams made of closed cells, including rigid urethane foam, are used as heat and cold insulation materials.

In particular, rigid urethane foams are often used as insulation materials for refrigerators due to their dimensional stability and shape retention.

By the way, this type of plastic foam is manufactured by a cross method in which a so-called foaming stock solution containing a foaming agent is discharged from a nozzle, or dichlorocyfluoromethane is added and discharged.

On the other hand, in response to the demand for energy conservation, we are improving the insulation performance of plastic foam, which is often used as an insulation material.
Reduction of raw materials is attracting attention.

The raw material savings for this insulation material are due to the low specific gravity of the foam (
(increase in bubble rate).

However, lowering the specific gravity generally leads to a decrease in heat insulation properties and a decrease in dimensional stability at low temperatures.

It is also known that the thermal insulation properties (thermal conductivity) of plastic foams reach a minimum at a certain bulk density, and the thermal conductivity of rigid urethane foams reaches a minimum at a bulk density of 35 kg/m3. It has also been confirmed that at densities below 35 kg/m3, the increase in radiant heat transfer influences the increase in thermal conductivity of the foam.

In order to resolve the conflicting demands of improving low-temperature dimensional stability and reducing the amount of radiant heat transfer, the present inventors conducted various studies and found that powdered or fibrous potassium titanate was converted into a hard urethane-based foaming stock solution. It has been found that when the compound is added and foamed, a rigid polyurethane foam having low thermal conductivity and good low-temperature dimensional stability can be easily obtained.

Based on the above findings, the present invention aims to provide a method for producing a rigid polyurethane foam suitable as a heat insulating material for refrigerators.

That is, the present invention uses a foaming stock solution generally used for producing rigid polyurethane foam, for example, a hydroxyl value of 200 to 8.
A foaming stock solution prepared by adding 5 to 120 parts by weight of polyisocyanate to 100 parts by weight of polyol No. It is characterized by adding potassium titanate to it and using it as a foaming stock solution.

In the present invention, potassium titanate, which is a component of the foaming stock solution, is generally selected from a powder form with an average particle diameter of about 3 μm or less, or a fibrous material with an average diameter of about 3 μm or more and a length of about 0.3 mm or less.

However, the composition ratio of the potassium titanate component in the lever is 1 to 100 parts by weight of the foaming stock solution excluding the potassium titanate component.
It is preferable to select about 30 parts by weight.

Next, examples of the present invention will be described.

Example 1 Polyoxypropylene polyol with a hydroxyl value of 450, crude tolylene diisocyanate, silicone foam stabilizer TFA
4200 (trade name, Toshiba Silicone Co., Ltd.), triethylenediamine as a catalyst, trichlorofluoromethane (blowing agent), water, fibrous potassium titanate Typeel (trade name, Otsuka Chemical Co., Ltd.), and silicon oxide powder in Table 1. A foamable stock solution was prepared by blending the ingredients at the composition ratio (parts by weight) shown below.

A rigid polyurethane foam was obtained by foaming each of the above-mentioned foamable stock solutions.

Table 1 also shows the results of measuring the bulk density kg/m3 and thermal conductivity λ·Kcal/m, h, and °C of the foam thus obtained.

Example 2 Polyoxypropylene polyol 10 with a hydroxyl value of 450
0 parts by weight crude tolylene diisocyanate 116 parts by weight,
Foaming is performed by a free foaming method using a foaming stock solution consisting of 1.5 parts by weight of a silicone foam stabilizer, 2.0 parts by weight of triethylenediamine, trichlorofluoromethane, 1.0 parts by weight of water, and 15 parts by weight of fibrous potassium titanate. During the treatment, trichlorofluoromethane was appropriately changed to obtain rigid urethane foams with different bulk densities.

The thermal conductivity of each of the foams thus obtained was measured, and the relationship between bulk density and thermal conductivity was determined, and the results were as shown by curve A in FIG.

For comparison, the bulk density kg/m3 and thermal conductivity λKcal/m,
When the relationship between h and °C was determined, it was as shown by curve a in Fig. 1.

In addition, the composition ratio of fibrous potassium titanate was changed in the foamable stock solution according to the above example, and the foaming conditions were kept constant to obtain a rigid polyurethane foam having a bulk density of 25 kg/m3.

The relationship between the content (composition ratio) of potassium titanate and the thermal conductivity λ·Kcal/m, h, and °C for the foam thus obtained was determined as shown in FIG. 2.

On the other hand, in the above process, rigid polyurethane foams having different bulk densities were obtained using foaming stock solutions with varying composition ratios of fibrous potassium titanate.

The relationship between the dimensional accuracy (dimensional change rate %) and bulk density kg/m@3 at -30 DEG C. for each of the foams thus obtained was determined as shown in FIG. 3.

In Fig. 3, curve B is for the case where the composition ratio of potassium titanate is 2 parts by weight, curve C is for the case when the composition ratio of potassium titanate is 4 parts by weight, and curve D is for the case when the composition ratio of potassium titanate is 5 parts by weight. Curve b shows the case where potassium titanate is not included (comparative example).

As is clear from the above specific examples, according to the method of the present invention, a rigid polyurethane foam having excellent properties such as low thermal conductivity and low-temperature dimensional stability can be easily obtained.

[Brief explanation of drawings]

FIG. 1 is a curve diagram showing the relationship between bulk density and thermal conductivity for rigid polyurethane foams produced by the method of the present invention and a method other than the present invention, and FIG. 2 is a curve diagram showing the composition of potassium titanate in the method of the present invention. A curve diagram showing the relationship between the ratio and the thermal conductivity of the obtained foam, and FIG. 3 is a curve diagram showing a comparison of the relationship between the bulk density and the dimensional stability of the rigid polyurethane foam produced by the method of the present invention. It is.

Claims (1)

[Claims] 1. A rigid polyurethane foam, which is mainly composed of a polyol and polyisocyanate having a hydroxyl value of 200 to 800, and is characterized by adding potassium titanate to a foamable stock solution containing a catalyst, a blowing agent, and a foam stabilizer, and foaming the mixture. manufacturing method.