Method for producing polyurethane foam for thermal insulating material

Abstract

To provide a method for producing a polyurethane foam for thermal insulating material having superior thermal insulation and strength in an industrially advantageous manner.SOLUTION: A method for producing a polyurethane foam for thermal insulating material includes a step of generating the polyurethane foam by mixing a first liquid containing a polyol compound, cyclopentane, and an aerogel, and a second liquid containing a polyisocyanate compound. The viscosity of the first liquid falls within a range from 1 time to 2.5 times relative to the viscosity of the second liquid.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for producing polyurethane foam for heat insulation materials.

Background Art

[0002] It has been considered to use an aerogel-containing polyurethane foam in which an aerogel is dispersed in a polyurethane foam as a heat insulation material for a refrigerator (Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The polyurethane foam used as a heat insulation material is desired to have further improved heat insulation performance. In addition, for a heat insulation material used in a refrigerator, it is desired to have high strength so as not to be damaged even when receiving impacts due to opening and closing of the door, etc. over a long period of time.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a method capable of industrially advantageously producing a polyurethane foam for a heat insulation material excellent in heat insulation performance and strength.

Means for Solving the Problems

[0006] In order to solve the above problems, the present inventors have found that when producing a polyurethane foam by mixing a first liquid containing a polyol compound and a second liquid containing a polyisocyanate compound, it is effective to add cyclopentane and an aerogel to the first liquid and adjust the viscosity of the first liquid within a predetermined range, and thus the present invention has been completed. Therefore, the present invention provides the following.

[0007] (1) A method for manufacturing a polyurethane foam for heat insulation, comprising a step of mixing a first liquid containing a polyol compound, cyclopentane, and an aerogel, and a second liquid containing a polyisocyanate compound to produce a polyurethane foam, wherein the viscosity of the first liquid is in the range of 1 time or more and 2.5 times or less with respect to the viscosity of the second liquid.

[0008] According to the method for manufacturing a polyurethane foam for heat insulation of (1), since the viscosity of the first liquid is within the above range and the first liquid and the second liquid are easily mixed, the generation and foaming of polyurethane proceed in a state of a mixed liquid with a uniform composition. For this reason, the foaming of polyurethane is hardly inhibited, the cell collapse is suppressed, and the generation of coarse cells is suppressed. Therefore, the polyurethane foam for heat insulation obtained by the manufacturing method of (1) has a small average cell diameter, and the heat insulation property and strength are improved.

[0009] (2) The method for manufacturing a polyurethane foam for heat insulation according to (1), wherein the viscosity of the second liquid is lower than the viscosity of the first liquid.

[0010] According to the method for manufacturing a polyurethane foam for heat insulation of (2), since the viscosity of the second liquid is lower than the viscosity of the first liquid, the first liquid and the second liquid are more easily mixed, and the generation and foaming of polyurethane can proceed in a state of a mixed liquid with a more uniform composition.

[0011] (3) The method for manufacturing a polyurethane foam for heat insulation according to (1) or (2), wherein the viscosity of the second liquid is in the range of 200 Pa·s or more and 400 Pa·s or less.

[0012] According to the method for manufacturing a polyurethane foam for heat insulation of (3), since the viscosity of the second liquid is within the above range, the first liquid and the second liquid are further easily mixed, and the generation and foaming of polyurethane can proceed in a state of a mixed liquid with a further uniform composition.

Effect of the Invention

[0013] According to the present invention, it becomes possible to provide a method for industrially advantageously producing a polyurethane foam for a heat insulating material that is excellent in heat insulation and strength.

Embodiment for Carrying Out the Invention

[0014] Hereinafter, a method for producing a polyurethane foam for a heat insulating material according to an embodiment of the present invention will be described.

[0015] The method for producing a polyurethane foam for a heat insulating material according to this embodiment includes a step of mixing a first liquid containing a polyol compound and a second liquid containing a polyisocyanate compound to generate a polyurethane foam. In the mixed liquid obtained by mixing the first liquid and the second liquid, the polyol compound and the polyisocyanate compound are reacted to generate a urethane containing an aerogel, and the generated urethane is foamed to obtain a polyurethane foam.

[0016] The first liquid contains a foaming agent and an aerogel. The first liquid may further contain a catalyst.

[0017] As the polyol compound, an amine-based polyol and a polyester-based polyol can be used. As the amine-based polyol, triethanolamine, ethylenediamine, aromatic diamine, and diethylenetriamine can be used. The polyester-based polyol is produced by dehydrative condensation of several kinds of carboxylic acids and polyhydric alcohols. As the carboxylic acid, adipic acid, phthalic acid, etc. can be used. As the polyhydric alcohol, ethylene glycol, 1,4-butanediol, 1,6-hexanediol, etc. can be used. The polyol compound may be used alone or in combination of two or more.

[0018] As the isocyanate compound, toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and xylene diisocyanate can be used. These isocyanate compounds may be used alone or in combination of two or more.

[0019] As the foaming agent, cyclopentane, trichlorofluoromethane, 1,1-dichloro-1-fluoromethane, 1,1,1,3,3-pentafluoropropane, 1,1,1,3,3-pentafluorobutane, and carbon dioxide can be used. These foaming agents may be used alone or in combination of two or more.

[0020] As the aerogel, silica aerogel can be used. The average particle size of the aerogel may be, for example, in the range of 10 μm or more and 300 μm or less.

[0021] The catalyst is used to adjust the reaction rate between the polyol compound and the isocyanate compound. As the catalyst, aliphatic amines can be used. Examples of aliphatic amines include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethylenediamine, triethanolamine, N,N-diisopropylethylamine, tetramethylethylenediamine, hexamethylenediamine, spermidine, spermine, amantadine, tetramethylhexanediamine, and pentamethyldiethylenetriamine. The catalyst may be used alone or in combination of two or more.

[0022] As the polyol compound, a polyol mixture in which a polyol compound and a catalyst are previously mixed may be used.

[0023] The blending ratios of the polyol mixture, isocyanate compound, foaming agent, and aerogel may be, for example, with the blending amount of the polyol mixture being 100 parts by mass, the blending amount of the isocyanate compound being in the range of 120 parts by mass or more and 130 parts by mass or less, the blending amount of the foaming agent being in the range of 10 parts by mass or more and 30 parts by mass or less, and the blending amount of the aerogel being in the range of 0.2 parts by mass or more and 0.5 parts by mass or less.

[0024] The viscosity of the first liquid used in this embodiment is in the range of 1 to 2.5 times that of the second liquid. Generally, when an aerogel is added to the first liquid containing a polyol compound, the viscosity of the first liquid increases. If the viscosity of the first liquid increases excessively, it becomes difficult to obtain a homogeneous mixture when the first liquid and the second liquid are mixed. When the formation and foaming of polyurethane proceed in a state where the composition of the mixed liquid of the first liquid and the second liquid is inhomogeneous, the foaming of polyurethane is inhibited, the cells are broken, large cells are likely to occur, the average cell diameter of the obtained polyurethane foam increases, and there is a risk of deterioration of heat insulation and strength. Therefore, in this embodiment, the viscosity of the first liquid is set in the range of 1 to 2.5 times that of the second liquid. Since the viscosity of the first liquid is within the above range, the first liquid and the second liquid are easily mixed, and the formation and foaming of polyurethane proceed in a state of a homogeneous mixed liquid, so the foaming of polyurethane is hardly inhibited, the breaking of cells is suppressed, and the generation of large cells is suppressed. Therefore, the polyurethane foam obtained by the manufacturing method of this embodiment has a small average cell diameter and improved heat insulation and strength. The viscosity of the first liquid may be in the range of 400 Pa·s or more and 750 Pa·s or less. The viscosity of the first liquid can be adjusted, for example, by the blending amount of the foaming agent. The viscosity is a value measured using a B-type rotational viscometer at a liquid temperature of 20°C.

[0025] The viscosity of the second liquid may be lower than that of the first liquid. The viscosity of the second liquid may be in the range of 200 Pa·s or more and 400 Pa·s or less. When the viscosity of the second liquid is within the above range, the first liquid and the second liquid are easily mixed, and the formation and foaming of polyurethane can proceed in a state of a more homogeneous mixed liquid.

[0026] There are no particular restrictions on the method of mixing the first liquid and the second liquid, and various methods used in conventional polyurethane foam manufacturing methods can be utilized. The formation and foaming of polyurethane proceed with the mixed liquid of the first liquid and the second liquid. The conditions for the formation and foaming of polyurethane are not particularly restricted, and various methods used in conventional polyurethane foam manufacturing methods can be utilized. The formation and foaming of polyurethane may be carried out, for example, under pressure or without pressure. The liquid temperature of the mixed liquid may be, for example, within the range of 18°C or higher and 25°C or lower. When the mixed liquid is put into a molding jig to carry out the formation and foaming of polyurethane, the temperature of the molding jig may be within the range of 30°C or higher and 60°C or lower.

[0027] The polyurethane foam for heat insulation obtained by the manufacturing method of this embodiment is excellent in heat insulation and strength, and thus is useful as a heat insulation material for refrigerators.

[0028] As described above, the embodiments of the present invention have been described in detail, but the present invention is not limited to the above embodiments.

Examples

[0029] [Example 1] 100 parts by mass of a polyol mixture containing a catalyst (manufactured by Sumika Covestro Polyurethane Co., Ltd.), 16 parts by mass of a blowing agent (cyclopentane), and 0.25 parts by mass of silica aerogel (average particle diameter: 128 μm) were mixed to prepare a first liquid. As a result of measuring the viscosity of the first liquid (liquid temperature: 20°C) using a B-type rotational viscometer (manufactured by Toki Sangyo Co., Ltd., TVC-10 type viscometer, using rotor NO. 24), it was 698 Pa·s.

[0030] Liquid diphenylmethane diisocyanate was prepared as the second liquid. As a result of measuring the viscosity of the second liquid (liquid temperature: 20°C) using a B-type rotational viscometer (manufactured by Toki Sangyo Co., Ltd., TVC-10 type viscometer, using rotor NO. 24), it was 322 Pa·s.

[0031] 114.25 parts by mass of the first liquid (liquid temperature: 20°C) and 124 parts by mass of the second liquid (liquid temperature: 20°C) were mixed and stirred under the conditions of a stirring speed of 4000 rpm for 4 seconds. The obtained mixed liquid was poured into a jig and reacted and foamed under the conditions of a jig temperature of 40°C and a curing time of 10 minutes to produce a polyurethane foam.

[0032] [Examples 2 - 3, Comparative Example 1] The first liquid was prepared in the same manner as in Example 1, except that the blending amount of cyclopentane was changed to the amount described in Table 1 below. The viscosity of the obtained first liquid is shown in Table 1 below. A polyurethane foam was produced in the same manner as in Example 1, except that the obtained first liquid was used.

[0033]

Table 1

[0034] (Density) The obtained heat insulation material was cut into a square shape in plan view to obtain a test piece. The size of the obtained test piece was measured with calipers to calculate the volume of the test piece, and the weight of the test piece was measured with an analytical balance. The density was obtained by dividing the weight of the test piece by the volume.

[0035] (Average cell diameter) The polyurethane foam was cut in a direction perpendicular to the foaming direction, and the cut surface of the obtained polyurethane foam was observed using a microscope. Cells (bubbles) with a major axis of 10 μm or more were extracted. The major axis of the extracted cells was measured, and the average was taken as the average cell diameter. The measurement of the major axis was performed on 30 or more cells.

[0036] (Thermal conductivity) Using a thermal conductivity measuring device (manufactured by Eihong Seiki Co., Ltd., FOX200), the thermal conductivity in the thickness direction of the polyurethane foam was measured.

[0037] (Compressive strength at 10% deformation) Using a tensile testing machine (manufactured by A&D), the compressive strength in the thickness direction of the polyurethane foam was measured. The test condition was set as a compressive strength of 5 mm / min, and the value at 10% deformation was calculated by the following formula. Compressive strength at 10% deformation (kgf / cm 2 ) = Load at 10% deformation (Kg) / Compressive surface area of the test piece before compression (cm 2 )

[0038]

Table 2

[0039] From the results of Table 1 and Table 2, it can be seen that the polyurethane foams of Examples 1 to 3 produced using the first liquid with a viscosity within the scope of the present invention have a higher density, a lower average cell diameter, a lower thermal conductivity, a higher heat insulation property, and a higher compressive strength compared with the polyurethane foam of Comparative Example 1 in which the viscosity of the first liquid exceeds the scope of the present invention. In Examples 1 to 3, since the first liquid and the second liquid were easily mixed and the formation and foaming of polyurethane proceeded in a state of a homogeneous mixed liquid, the foaming of polyurethane was hardly inhibited, the cell collapse was suppressed, and the generation of coarse cells was suppressed. For this reason, it is considered that the polyurethane foams of Examples 1 to 3 have a small average cell diameter and improved heat insulation property and strength. On the contrary, in Comparative Example 1, since the first liquid and the second liquid were difficult to mix and the formation and foaming of polyurethane proceeded in a state of a non-uniform mixed liquid, the foaming of polyurethane was inhibited and the cells became small, and the resulting polyurethane foam had a higher resin ratio and a higher density. The cell portion of the polyurethane foam has a higher thermal conductivity and a higher compression resistance than the resin portion. For this reason, it is considered that the polyurethane foam of Comparative Example 1 has a reduced heat insulation property and strength.

Claims

1. A first liquid containing a polyol compound, cyclopentane, and an aerogel, and a second liquid containing a polyisocyanate compound are mixed to produce a polyurethane foam, wherein the viscosity of the first liquid is in the range of 1 to 2.5 times that of the second liquid. A method for producing a polyurethane foam for a heat insulating material.

2. The method for producing a polyurethane foam for a heat insulating material according to claim 1, wherein the viscosity of the second liquid is lower than that of the first liquid.

3. The method for producing a polyurethane foam for a heat insulating material according to claim 1 or 2, wherein the viscosity of the second liquid is in the range of 200 Pa·s or more and 400 Pa·s or less.

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