JPH0418431A - Polyurethane resin foam and production thereof - Google Patents

Abstract

PURPOSE:To obtain the title foam reduced in change with the lapse of time in heat conductivity and capable of being used as good heat insulating material by adding an unreactive and nonvolatile liquid to an urethane resin raw material liquid in which a specific foaming agent is used, blending these components and crosslinking the blend while foaming. CONSTITUTION:An unreactive and nonvolatile liquid (e.g. fluid paraffin or oils and fats) is added and blended with an urethane resin raw material liquid containing one ore more kind of foaming agents selected from water, dichlorotrifluoroethane and dichloromonofluoroethane, preferable at an amount of 0.1-10wt.% and the blend is crosslinked while foaming to provide the aimed foam having the above-mentioned nonvolatile liquid film in the cell wall of the foam.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a polyurethane resin foam and a method for producing the same.

(Prior art) Polyurethane resin foams are classified into soft foams and hard foams depending on the degree of crosslinking. Soft foams are used for automobile parts, packaging containers, etc., and hard foams are used for insulation materials, sound absorbing materials, etc. is widely used.

Such polyurethane resin foams are usually produced using polyol and isonoanate as main raw materials. That is, a raw material having a plurality of alcohol groups (-OH) (usually referred to as a polyol) and a plurality of isocyanate groups (
-Neo), the alcohol group and the isocyanate group undergo a chemical reaction to form a urethane bond (-N)ICOO-). As a result, the mixed liquid gradually hardens to form a urethane resin. In the second case, if a substance such as chlorofluorocarbon, such as trichloromonofluoromethane, which can be vaporized by the reaction heat is present in the reaction solution, it will be evaporated by the heat during the reaction to form bubbles. After forming bubbles, the reaction progresses further and the cell walls harden, forming a solidified urethane resin. In this way, a urethane resin foam is formed.

As a general production procedure, first, a blowing agent, catalyst, foam stabilizer, etc. are added to a polyol stock solution and mixed thoroughly. Immediately before foaming, quickly mix the above liquid mixture and isocyanate,
Pour into the desired mold. After foaming and curing, the reaction is completed by applying a slight temperature to obtain a polyurethane resin foam.

When a polyurethane resin foam is used, for example, as a heat insulating material, a foaming agent such as fluorocarbon, which has a low thermal conductivity, is used to improve the heat insulating properties. The foaming agent is a liquid at room temperature, but when the temperature of the liquid rises due to the reaction heat generated during the reaction between the polyol and the isocyanate, the foaming agent vaporizes and exhibits a foaming effect. These blowing agents include Freon 11, which has a boiling point of 23.8°C and is non-reactive.
(), dichloromonofluoromethane), etc. are often used.

Incidentally, it has recently been found that when Freon-11 is released into the atmosphere, it is a relatively stable substance and therefore diffuses into the stratosphere without being decomposed. As a result, it has become clear that Freon-11 decomposes in the stratosphere due to strong ultraviolet rays from space, causing the destruction of the ozone layer. It is said that if the ozone layer is destroyed, a large amount of harmful ultraviolet rays will reach the ground, causing various adverse effects such as destruction of biological systems and harm to the human body. For this reason, the use of Freon-11 is being restricted, and there is a trend toward prohibiting its use in the future.

Under these circumstances, carbon dioxide is being considered as one of the alternatives to Freon-11. That is, a small amount of water is added and mixed in advance into the polyol stock solution, and when mixed with isocyanate, the water and isocyanate react to generate carbon dioxide, which is used as a blowing agent. .

(Problem to be solved by the invention) However, carbon dioxide itself has a thermal conductivity that is approximately twice as high as that of Freon 11, and it also has the property of easily permeating urethane resin walls. There is a problem in that the polyurethane resin foam evaporates from the bubbles over time, changing the thermal conductivity of the polyurethane resin foam. This means that, for example, when used as a heat insulating material, the heat insulating effect deteriorates over time. In particular, carbon dioxide escapes from the bubbles, resulting in a thermal conductivity of approximately 1.7 relative to carbon dioxide.
If more air enters than the material, its performance as a heat insulator will be greatly reduced.

The present invention was made in order to address the above-mentioned problems, and it is a polyurethane that suppresses changes in thermal conductivity over time and makes it possible to stably maintain its effectiveness as a heat insulator, for example. The object of the present invention is to provide a resin foam and a method for manufacturing the same.

[Constitution of the Invention (Means for Solving the Problem) That is, the polyurethane resin foam of the present invention is a polyurethane resin foam using at least one selected from water, dichlorotrifluoroethane, and dichloromonofluoroethane as a blowing agent. The resin foam is characterized in that a non-reactive non-volatile liquid film is present within the cell walls of the foam.

Furthermore, the method for producing a polyurethane resin foam of the present invention includes:
A non-reactive non-volatile liquid is added to and mixed with a urethane resin raw material liquid containing at least one blowing agent selected from water, dichlorotrifluoroethane, and dichloromonofluoroethane, and the mixture is foamed while cross-linking. It is characterized by allowing

The urethane resin raw material liquid used in the present invention can be any of various known raw material liquids capable of forming urethane bonds, such as polyols such as polyethers, polyesters, and glycols, and isyanate.

Further, the urethane resin raw material liquid contains at least a blowing agent, such as water used as carbon dioxide,
Furthermore, additives such as a foaming aid, a foam stabilizer, a reaction catalyst, an antistatic agent, and a coloring agent are added as necessary.

In the present invention, a non-reactive and non-volatile liquid is added to and mixed with the urethane resin raw material liquid, and the mixed liquid is foamed and crosslinked to obtain a polyurethane resin foam. For example, when polyol and isyanate are used as urethane resin raw materials, a non-reactive non-volatile liquid is added to and mixed with the stock solution of either of these.

When polyol and isyanate are mixed vigorously, a chemical reaction begins, forming urethane bonds and forming a resin. At this time, if water is present in the reaction solution, water and isocyanate react to generate carbon dioxide. This carbon dioxide acts as a blowing agent and forms bubbles. As the reaction progresses gradually, the apparent volume of the reaction solution gradually increases and expands.

As a result, as shown in FIG. 1, a foam having a volume ratio of 90% or more is obtained. The cells 101 of the foam are mostly closed cells, and are composed of an extremely thin film 102 with a wall thickness of about 1 μm or less as observed with an electron microscope.

When a non-reactive and non-volatile liquid is added and mixed into the reaction liquid, this liquid will cause the foam wall material 1 to form as bubbles are generated.
It will be included in 02. As the reaction progresses, the reactive liquid (polyol and isyanate) in the cell wall 102
is cured and turned into a resin. However, the non-reactive liquid contained in the cell wall 102 is included in the resin as it is without reacting. Further, a part of the liquid gradually bleeds out from the cell wall resin to the wall surface, forming a liquid film 103, similar to the bleedout of liquid components from the resin.

The non-reactive non-volatile liquid forms a liquid film inside the cell wall or on the surface of the cell wall during foaming and curing or after foaming, thereby reducing the gas permeability of the cell wall.

The non-reactive non-volatile liquid used in the present invention is a liquid that does not show reactivity with the urethane resin raw material at least at the temperature during foaming and is non-volatile at least at the temperature during foaming, such as liquid paraffin. , polysiloxane,
Examples include fats and oils and mineral oil. These may be used alone or as a mixture of two or more.

These non-reactive non-volatile liquids are preferably added in an amount of 0.1% to 10% by weight based on the polyurethane resin foam. In other words, if it is less than 0.1% by weight, the change in thermal conductivity over time (deterioration) is almost the same as that without additives, so if it is less than 0.1% by weight, sufficient gas permeation prevention effect cannot be obtained. . Also, 1
If it exceeds 0% by weight, the polyurethane resin foam becomes sticky and soft, making it impossible to obtain a practical foam.

(Function) In the polyurethane resin foam of the present invention, by adding and mixing a non-reactive non-volatile liquid into the urethane resin raw material liquid in advance, the inside of the cell walls and the surface of the cell walls can be cured while the foam is curing or after foaming. A liquid film is formed on the surface.

The formed non-reactive non-volatile liquid film reduces the gas permeability of the cell wall, and prevents the gas inside the cell from permeating and volatilizing over time. This suppresses changes in thermal conductivity of the polyurethane resin foam over time.

Also, in the unlikely event that microcracks occur on the cell wall for some reason during the foam curing process,
The presence of the non-reactive non-volatile liquid can prevent gas from escaping from the crack groove.

(Example) Examples of the present invention will be described below.

Example] FIG. 2 shows an example of the manufacturing process of the polyurethane resin foam of the present invention. The manufacturing process of the polyurethane resin foam of this example will be explained below with reference to the same figure.

To 100 parts by weight of polyol MN-400 (trade name, manufactured by Mitsui Toatsu Chemical Co., Ltd.), 3 parts by weight of water, 2 parts by weight of silicone foam stabilizer, and 3 parts by weight of amine catalyst were added. -201) and stirred thoroughly. To this, add 5 parts by weight of liquid paraffin as a non-reactive non-volatile liquid (Fig. 202), and stir to mix thoroughly.
3) A premixing stock solution before foaming was prepared.

Next, 150 parts by weight of isocyanate was added to 100 parts by weight of the above premix stock solution, mixed and stirred (Fig. 204), and quickly poured into a mold (Fig. 205).
. Foaming and curing were completed within a few minutes, so this was
After-cure at 0°C for 10 minutes (Figure-206)
Thereafter, the mold was removed and a polyurethane resin foam was obtained.

Example 2 In the same manner as in Example 1 above, polyol, water, a silicone foam stabilizer, and an amine catalyst were blended in equal amounts, and after stirring well, alkylbenzene Atmos T-60 (product name) was added as a non-reactive nonvolatile liquid. 10 parts by weight of 10% by weight (trade name, manufactured by Kyodo Sekiyu ■) were added thereto, and the mixture was sufficiently stirred to prepare a premixing stock solution. Thereafter, a polyurethane resin foam was obtained under the same conditions as in Example 1.

Example 3 To 100 parts by weight of polyol NM-470 (trade name, manufactured by Mitsui Toatsu Chemical ■), 4 parts by weight of water, 15 parts by weight of a silicone foam stabilizer, and 3 parts by weight of an amine catalyst were added, After sufficient stirring, 18 parts by weight of oleic acid glycerin ester was added as a nonvolatile liquid, and the mixture was further stirred to prepare a premixing stock solution.

Next, 140 parts by weight of isocyanate was added to 100 parts by weight of this premixing stock solution, and after vigorous stirring and mixing, the mixture was quickly poured into a mold, foamed, and cured to obtain a polyurethane resin foam.

Comparative Example 1 A polyurethane resin foam was produced under the same conditions as in Example 1, except that liquid paraffin as a non-reactive non-volatile liquid was not added to the raw material liquid.

Comparative Example 2 In the same manner as in Example 1 above, polyol, water, silicone foam stabilizer and amine catalyst were blended in the same amount, and after stirring and mixing thoroughly, 0.05 parts by weight of liquid paraffin was added,
The mixture was further stirred and mixed.

To 100 parts by weight of the prepared liquid, 150 parts by weight of isocyanate was added, mixed with vigorous stirring, and quickly poured into a mold.

Thereafter, foaming and curing were performed in the same manner as in Example 1 to obtain a polyurethane resin foam.

Comparative Example 3 In the same manner as in Example 1, the same amounts of polyol, water, silicone foam stabilizer, and amine catalyst were blended and thoroughly stirred, and then 30 parts by weight of liquid paraffin was added and mixed with stirring.

For 100 parts by weight of this mixture, 130 parts by weight of isocyanate
After adding parts by weight and stirring vigorously, the mixture was quickly poured into a mold to produce a foam. However, this foam had no surface stickiness and could not be used practically.

This is thought to be due to the large amount of liquid paraffin added (30 parts by weight), which causes severe bleed-out to the cell wall surface, and the presence of too much liquid paraffin, which partially inhibits the reaction between polyol and isocyanate. .

The thermal conductivity of the polyurethane resin foams of each Example and Comparative Example obtained as described above was measured.

Table 1 shows the initial value of the thermal conductivity of each polyurethane resin foam and the thermal conductivity after three months.

Table 1 As is clear from the results in Table 1, the polyurethane resin foams mixed with the non-reactive non-volatile liquid according to each example showed smaller changes in thermal conductivity than those according to the comparative examples. I understand.

This is because the non-reactive non-volatile liquid mixed in after foaming bleeds out onto the surface of the cell walls, forming a thin liquid film, which prevents the gas inside the cells from permeating. In addition, even for microcracks that occur due to some reason, the presence of non-volatile liquid in the cracks will help prevent microcracks from occurring.
It is also surmised that this is due to less gas being released.

[Effects of the Invention] As explained above, according to the present invention, the presence of the non-reactive non-volatile liquid film suppresses the permeation of gas inside the bubbles, resulting in a polyurethane resin foam with little change in thermal conductivity over time. can get. As a result, when a polyurethane resin foam is used as a heat insulating material, for example, the deterioration of the heat insulating properties is reduced, making it possible to provide a good heat insulating material.

[Brief explanation of the drawing]

FIG. 1 is an enlarged schematic diagram showing the state of cells in the polyurethane resin foam of the present invention, and FIG. 2 is a diagram showing the manufacturing process of the polyurethane resin foam of one embodiment of the present invention. 101...bubble, 102...bubble wall,
103...Liquid film. Applicant: Toshiba Corporation Toshiba Audio/Video Engineering Corporation

Claims (2)

[Claims] (1) A polyurethane resin foam using at least one selected from water, dichlorotrifluoroethane, and dichloromonofluoroethane as a blowing agent, wherein a non-reactive nonvolatile liquid is contained within the cell walls of the foam. A polyurethane resin foam characterized by the presence of a membrane. (2) A non-reactive non-volatile liquid is added to and mixed with a urethane resin raw material liquid containing at least one blowing agent selected from water, dichlorotrifluoroethane and dichloromonofluoroethane, and the mixed liquid is foamed. A method for producing a polyurethane resin foam, characterized by crosslinking the foam.