JPH07102106A - Heat insulating foamed article - Google Patents

Abstract

PURPOSE:To obtain a heat-insulating rigid polyurethane foam having high heat- insulating function using a new hydrocarbon composition as a blowing agent. CONSTITUTION:Neohexane is used as a blowing agent. A polyol component is composed of a polyol, a foam stabilizer, a catalyst and the blowing agent which are mixed in the ratios of 100, 3, 3 and 40 in terms of weight parts (pts. wt.) respectively. The obtained polyol premix component is compound with 165 pts.wt. of isocyanate component. This is mixed and stirred with a high- pressure foaming apparatus, then filled into the space formed by an outer case 1 and an inner case and foamed to obtain a heat-insulating polyurethane foam 2. The obtained polyurethane foam has a lower heat conductivity than a pentane-foamed polyurethane and accordingly a heat insulating function of the polyurethane foam of the present invention is more improved than that of the pentane-foamed polyurethane while compressibility and dimensional stabilities remain on the same levels as the latter polyurethane.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foamed heat insulator, and more particularly to a foamed heat insulator applied to a refrigerator, a freezer and the like.

[0002]

2. Description of the Related Art In recent years, the problem of CFC pollution such as ozone layer depletion and global warming has become a social problem, and reduction of specific CFCs (trichloromonofluoromethane, etc.), which is a foaming agent for foam insulation materials such as rigid urethane foam, has been abolished. Is a big issue.

Therefore, 1,1-dichloro-1-fluoroethane (HCFC-141b), 1,1-dichloro-2,2,2 is used as a foaming agent with a substance having a small ozone depletion coefficient.
2-Trifluoroethane (HCFC-123) or the like is used to form a polyurethane foam.

However, HCFC-141b and HCFC1
No. 23 does not have an ozone depletion potential of 0 because it has a chloro group in its molecular structure. For this reason, it is a transitional CFC substitute and needs to be replaced with a long-term usable substance.

May 1993 Polyurethane International Forum 93. On page 197 of the presentation paper, Gerhard Heilich and Yoshinori Kihara reported a research report on "pentane foamed rigid urethane foam", in which pentane does not contain halogen elements and therefore does not destroy the ozone layer. It is disclosed that the compound has both superiority in physical properties and properties to the environment, and its flammability can be solved by safety measures in manufacturing technology and by increasing the amount of flame retardant in the foam.

[0006]

However, there has been a problem that the thermal conductivity of pentane itself is higher than that of the conventional freon-based foaming agent, and the heat insulating performance of pentane foamed polyurethane foam is poor.

When a hydrocarbon other than pentane is used as a foaming agent, one having a lower molecular weight than pentane has a low boiling point and has a high thermal conductivity, which makes it difficult to use. However, there is a problem in that the rate is low but the boiling point is high, so that the polyurethane is not easily vaporized by the heat of reaction and does not serve as a foaming agent.

Therefore, a first object of the present invention is to obtain a rigid polyurethane foam heat insulating material having excellent heat insulating properties by utilizing a novel hydrocarbon as a foaming agent.

A second object of the present invention is to prepare an excellent foaming agent which is made by mixing two kinds of compounds to make up for the drawbacks of a foaming agent composed of a kind of hydrocarbon, and which is a rigid polyurethane foam exhibiting excellent heat insulating properties. Is to get.

A third object is to prepare a similarly excellent foaming agent by mixing three kinds of compounds to obtain a rigid polyurethane foam having a good heat insulating property.

[0011]

In order to achieve the above-mentioned first object, the present invention comprises a foaming agent containing a quaternary carbon-containing hydrocarbon having 6 or 7 carbon atoms as a main component in bubbles. To form a heat-insulating foam containing the rigid polyurethane foam.

As the hydrocarbon, a hydrocarbon having a tertiary butyl structure and having at least one of 6 and 7 carbon atoms is preferable. Among them, neohexane is most preferable in the case of a single composition, and as a mixed foaming agent, A hydrocarbon mixture containing neohexane or 3,3-dimethyl-1-butene as a main component is preferable.

Further, in order to achieve the second object, the present invention provides a foaming agent containing an azeotropic mixture of a saturated hydrocarbon having 6 carbon atoms and an ether compound having the same molecular weight as the saturated hydrocarbon. It is used to form a heat-insulating foam made of rigid polyurethane foam which is contained in cells.

In order to achieve the third object, the present invention provides a saturated hydrocarbon having 7 carbon atoms, an ether compound having a molecular weight similar to that of the saturated hydrocarbon, for example, 1-
A blowing agent containing a ternary azeotropic mixture containing an unsaturated hydrocarbon having 5 to 8 carbon atoms, such as pentene, 2-pentene, isoprene, 1,4-pentadiene, 1,3-pentadiene, and cyclooctatetraene. It is used to form a heat-insulating foam made of rigid polyurethane foam which is contained in cells.

The ether compounds used for the second and third purposes include ethyl isopropyl ether, tertiary butyl methyl ether, ethyl propyl ether,
It is preferably one selected from allyl ethyl ether and dimethoxymethane.

[0016]

[Function] The carbon number having quaternary carbon of the present invention is 6 or 7
Since the quaternary carbon skeleton structure lowers the boiling point of the compound in the foaming agent of the first structure containing hydrocarbon as a main component, the boiling point is very low even with the same molecular weight, the thermal conductivity is low, and the boiling point is It can be used as a foaming agent at 50 ° C or lower.

In particular, the tertiary butyl structure has a bulky branched shape, so that the intermolecular force is reduced and the effect of lowering the boiling point is great.

As a result, it is possible to form a rigid polyurethane foam having an improved heat insulating property over pentane foaming.

Further, the foaming agent of the present invention, which uses a mixture of a saturated hydrocarbon having 6 carbon atoms and an ether compound having the same molecular weight as that of the saturated hydrocarbon, forms an azeotropic compound to form an azeotropic mixture. Has a boiling point much lower than that of a single type or an ordinary mixed type, and is therefore suitable as a blowing agent for rigid polyurethane.

The hydrocarbon as the first component to be used is required to have a low thermal conductivity and to easily show azeotropy. To meet this requirement, if the number of carbon atoms in the hydrocarbon is 6, both of them are required. The characteristics of can be satisfied.

The ether compound of the second component is azeotropic with the hydrocarbon easily and has a molecular weight almost equal to that of the hydrocarbon so that the thermal conductivity of the azeotropic mixture does not increase. is necessary. The ether compound is a polar compound having a molecular weight similar to that of the hydrocarbon and a boiling point of about 60 ° C., and has an action of lowering the azeotropic point.

The mixture of these two components forms an azeotropic mixture and has an azeotropic point of 50 ° C. or lower, which is suitable for the present invention, and is easily vaporized by reaction heat during foam molding of urethane to be a suitable foaming agent. It is possible to form a rigid polyurethane foam exhibiting excellent heat insulating properties.

Further, the foaming agent of the third constitution using the ternary mixture of the saturated hydrocarbon having 7 carbon atoms, the ether compound and the unsaturated hydrocarbon having 5-8 carbon atoms of the present invention is
A ternary azeotrope is formed to satisfy the properties required as a foaming agent, and a good polyurethane foam heat insulating foam is obtained.

C7 hydrocarbons have lower thermal conductivity than C6 hydrocarbons, but have very high boiling points. By adding an unsaturated hydrocarbon having 5 to 8 carbon atoms and a low boiling point thereto, it becomes possible to exhibit physical properties equivalent to those of the saturated hydrocarbon having 6 carbon atoms shown in the second structure.

Therefore, by adding an ether compound to a mixture of a hydrocarbon having 6 carbon atoms and the above unsaturated hydrocarbon to form a ternary eutectic compound, a low thermal conductivity and an azeotropic property are obtained. By forming a mixture, an appropriate boiling point can be obtained, and as in the second constitution, good heat insulation of rigid polyurethane foam can be obtained as an excellent foaming agent.

As the unsaturated hydrocarbon having 5 to 8 carbon atoms,
1-Pentene, 2-pentene, isoprene, 1,4-pentadiene, 1,3-pentadiene and cyclooctatetraene are preferred.

Since the azeotropic mixture used in the second and third constitutions has the same composition in the liquid state and the gas state, it has the effect of lowering the boiling point, and is also used by changing it from the liquid state to the gas state by the heat of reaction. It has suitable properties for the present invention.

[0028]

[Examples] Polyurethane foam forms a heat-insulating foam by polymerizing by the reaction of a polyol and an isocyanate, and the foaming agent volatilizes due to the heat of reaction to form a structure in which the polyurethane structure is filled with bubbles. Is.
In particular, the heat insulating property is greatly affected by the thermal conductivity of the gas existing in the polyurethane bubbles such as the foaming agent, and the gas having lower thermal conductivity has the higher heat insulating property.

Normally, a foam stabilizer is added to adjust the foaming state, and a catalyst is added to control the reactivity of polyurethane. However, the same addition is required for the heat insulator of the present invention. You may go according to.

The structure having a hydrocarbon quaternary carbon as the main component of the blowing agent used in the first constitution of the present invention is specifically the structure shown in (Chemical formula 1) or (Chemical formula 2). , And C6 to C7 hydrocarbons having these structures. This structure of (Chemical formula 1) is a tertiary butyl structure and is a preferable structure suitable for the present invention. Hereinafter, the present invention will be described using the tertiary butyl structure shown in Chemical formula 1.

[0031]

[Chemical 1]

[0032]

[Chemical 2]

Among the foaming agents having a tertiary butyl structure and a hydrocarbon having 6 to 7 carbon atoms as a main component of the present invention, as a foaming agent to be used alone, neohexane (also known as 2,2-dimethylbutane) is used. Is most suitable, the molecular weight is 86.2, the boiling point is 49
Since it is ℃, it has suitable physical properties.

As the mixed foaming agent, a hydrocarbon mixture containing neohexane or 3,3-dimethyl-1-butene (molecular weight 84.2, boiling point 41.2) as a main component has a boiling point of 5
The temperature can be kept below 0 ° C and the thermal conductivity is 0.013 of pentane.
It is lower than 5kcal / (mh ℃). Therefore, by using the mixture as a foaming agent, an excellent foaming agent having various properties can be formed.

As the saturated hydrocarbon having 6 carbon atoms in the second constitution of the present invention, cyclohexane (molecular weight 84.2, boiling point 80.7 ° C.), normal hexane (molecular weight 86.2,
Boiling point 69.7 ° C), isohexane (molecular weight 86.2, boiling point 63.3 ° C) and neohexane are available, and these molecular weights, boiling points and thermal conductivity (all are 0.0114 kcal / (mh
The following azeotropic mixture with an ether compound is suitable for the present invention from the characteristics of (° C.) or lower).

As the ether compound, ethyl isopropyl ether (molecular weight 88.1, boiling point 54 ° C.), tertiary butyl methyl ether (molecular weight 88.2, boiling point 55.2), ethyl propyl ether (molecular weight 88.
1, boiling point 63.6 ° C), allyl ethyl ether (molecular weight 86.1, boiling point 65 ° C), dimethoxymethane (molecular weight 7)
6, the boiling point is 44 ° C.) and the like, and these are compounds having the same molecular weight as the above hydrocarbons, a low boiling point, and a high polarity. The azeotropic point is 50 ° C due to the azeotropic composition of these two components.
Below, the thermal conductivity shows a low value.

The blowing agent shown in the third constitution of the present invention is obtained by adding an unsaturated hydrocarbon having 5 to 8 carbon atoms to a hydrocarbon having a high boiling point and having 7 carbon atoms, and mixing with the ether compound shown in the second constitution. A foaming agent is obtained by boiling.

As the unsaturated hydrocarbon having 5 to 8 carbon atoms,
1-pentene (molecular weight 70.1, boiling point 29.9 ° C), 2-pentene (molecular weight 70.1, boiling point 37 ° C), isoprene (molecular weight 68.1, boiling point 34.1 ° C), 1,4-pentadiene ( Molecular weight 68.1, boiling point 26 ° C), 1,3-pentadiene (molecular weight 68.1, boiling point 42 ° C), cyclooctatetraene (molecular weight 104.2, boiling point 45.5 ° C) lowers the boiling point of hydrocarbons. It is desirable because 1,4-Pentadiene has a particularly low boiling point and is suitable as a component of a foaming agent.
On the other hand, cyclooctatetraene is preferable because it has a large molecular weight and reduces the thermal conductivity of the foaming agent.

In the method of using a hydrocarbon compound as a foaming agent as in the present invention, it is necessary to change the raw material recipe different from the raw material recipe at the time of freon foaming. In particular, since the density, bubble shape, and dimensional stability change, it is necessary to improve the formulation (composition) of the raw material and the molecular structure of the raw material. Specific examples of the mixing method and foaming method are as follows. For example,

The polyol used in the present invention includes, in addition to conventionally used polyether-based polyols and polyester-based polyols, many hydroxyl groups synthesized from polyhydric alcohols for the purpose of obtaining hardness and controlling reactivity. The polyols contained therein are suitable. Also suitable are catalyst-containing polyols containing tertiary amine, phosphorus, and halogen together with hydroxyl groups in the polyol molecule, flame-retardant polyols, or aromatic polyols.

The isocyanate used in the present invention is diphenylmethane diisocyanate (MDI) type, tolylene diisocyanate (TDI) type, xylylene diisocyanate (XDI), metaxylylene diisocyanate (MXDI), hexamethylene diisocyanate (HM).
DI), lysine diisocyanate (LDI), isophorone diisocyanate (IPDI), trimethylhexamethylene diisocyanate (TMDI), dimer acid diisocyanate (DDI), etc. are suitable, and polyisocyanate imparting flame retardancy thereto is most suitable. There is.

As the catalyst used in the present invention, it is necessary to select a most effective catalyst such as a gelling catalyst, a foaming catalyst and a delayed catalyst depending on the reactivity of the urethane raw material. Commonly used catalysts are tertiary amines and organometallic compounds, and amine-based catalysts include monoamines, diamines, triamines, cyclic amines, alcohol amines and ether amines. Of the organometallic compounds, organotin compounds are most often used. In the present invention, since the foaming agent to be used has a large latent heat of vaporization, a highly active catalyst is desirable for promoting foaming, but it is necessary to use different catalysts or to mix various catalysts depending on the case. Further, water also reacts with isocyanate to form a urea bond, which greatly contributes to the physical properties of urethane, and therefore may be added to improve the crosslink density.

The foam stabilizer used in the present invention is generally an alkylsilane-polyoxyalkylene copolymer. Silicon type foam stabilizers have different effects, but show excellent addition effects. In addition, the compatibility of raw materials is increased,
Any substance can be used as long as it becomes a bubble nucleus and lowers the surface tension to stabilize the bubble during foaming.

The blowing agent used in the present invention is a hydrocarbon compound, and the flammability of urethane foam is a problem.
It is desirable to use flame retardants. The flame retardant used in the present invention includes alkyl phosphates, dimethyl methylphosphonate, polymeric phosphites, bromine / phosphorus compounds, organic bromine compounds, ammonium polyphosphates,
Diethylbishydroxyethylaminoethyl phosphate, neopentyl bromide polyether, neopentyl bromide adibate, dibromopropanol, dibromo neopentyl glycol, 2,3-dibromo 2-butyne 1,
4-diol, brominated polyether, etc.

By adding additives such as a hydrolysis inhibitor and an antioxidant, a long-term physical property stabilizing effect can be obtained. On the contrary, when an unsaturated hydrocarbon is used, it is possible to impart long-term stability and flame retardancy by simultaneously adding halogen and adding halogen.

Since the physical properties of polyurethane produced by such in-situ foaming vary considerably depending on the formulation, stirring and heating conditions, it is necessary to study the optimum conditions in detail. In particular,
In the formation of a foam using the foaming agent of the present invention, the foaming agent must be vaporized together with the polyurethane reaction during in-situ foaming, and therefore a sufficiently optimized heating condition is required.

The box body for the refrigerator used in the present invention is shown in FIG.
It is configured by combining a metallic outer box and a hard resin inner box as shown in FIG. The hard resin inner box is a thermoplastic resin because of its moldability, and it is desirable that the foamed polyurethane heat insulating body of the present invention does not attack the resin. For example, ABS resin having a high nitrile content is suitable.

(Example 1) Raw materials were formulated as shown in Table 1. Polyol A is an aromatic amine-based polyether polyol having a hydroxyl value of 500 mgKOH / g and a foam stabilizer A.
Is F373 manufactured by Shin-Etsu Chemical Co., Ltd., and catalyst A is Kaolizer No. manufactured by Kao Corporation. 1. Foaming agent A was neohexane and 40 parts was added. Each of these raw materials is mixed at the blending number shown in the table to form a polyol component. On the other hand, the isocyanate component has an amine equivalent of 170.

The polyol premix component thus prepared and the isocyanate component are mixed in a predetermined mixing number, mixed and stirred by a high-pressure foaming machine, and a space constituted by an outer box and an inner box as shown in FIG. Part filled and foamed,
A polyurethane foam insulation foam was obtained.

The thermal conductivity, compressive strength and dimensional stability of the obtained heat insulating foam were measured. For comparison, the formulation using cyclopentane as a foaming agent is shown in Comparative Example 1 in (Table 1).

[0051]

[Table 1]

The polyurethane foam obtained was compared with Comparative Example 1
Compared with the pentane foamed polyurethane of No. 3, the thermal conductivity of pentane foam was 0.0178 kcal / (mh ° C.), but that of neohexane foamed was 0.0163 kcal / (mh ° C.). Neohexane had a lower thermal conductivity and improved heat insulation. The compressibility and dimensional stability were similar to those of pentane foam.

(Example 2) As a foaming agent B consisting of a binary azeotrope, a raw material formulation was prepared when 40 parts of a mixture of azeotropic point of cyclohexane and ethyl isopropyl ether (about 65: 35% by weight) was added (Table 1). ).

A polyol premix was prepared in the same manner as in Example 1 according to the raw material formulation shown in Table 1 and mixed and stirred. At the same heating temperature of 40 to 50 ° C. as in the prior art, foam molding was performed in a box to perform heat insulation. A foam was obtained.

The thermal conductivity of a foam foamed with the foaming agent B is
It was 0.0169 kcal / (mh ° C), which was lower than that of pentane foaming, and showed good heat insulation. This is because the thermal conductivity of the azeotrope used is lower than that of cyclopentane.
The compression strength and dimensional stability of this raw material formulation were similar to those of cyclopentane.

Similarly, an azeotropic mixture of each of isohexane, 2,3-dimethylbutane and normal hexane and ethyl isopropyl ether was used as a foaming agent to obtain a foam having good heat insulating properties.

When foaming was performed using an azeotropic mixture of neohexane and ethyl isopropyl ether, a foam having the same heat insulating property as in Example 1 was obtained under heating conditions of about 40 ° C. and heating conditions of about 10 ° C. Could be reduced.

As a comparison, when an attempt was made to form a foam using a foaming agent in which heptane having 7 carbon atoms was mixed with ethyl isopropyl ether, foaming did not occur at the conventional temperature, but when foaming at a considerably high temperature, the inside of the foam cracked. Was observed.

Alternatively, pentane was mixed with the above ether to obtain a polyurethane foam as a foaming agent.
The bubbles became larger and the thermal conductivity was considerably higher than that of pentane foam.

As described above, the azeotropic compound of the saturated hydrocarbon having 6 carbon atoms of the present invention and the polar compound such as ether having the same molecular weight showed excellent foaming property and heat insulating property.

Example 3 As the ternary mixed foaming agent C, three liquids of 2,2,3-trimethylbutane, 2,2-dimethoxypropane and 1,4-pentadiene were used as an azeotropic composition (about 55:40). :
5% by weight) and a formulation shown in (Table 1) was used to form a polyurethane foam by the same mixing and foaming method as in Example 1. The foaming agent C was mixed in 40 parts.

The foaming was in a good foaming state at a heating temperature as usual, and the foaming efficiency was better than that of Example 2.
Further, the dimensional stability of the foam was similar to that of pentane foam.

The thermal conductivity is smaller than that of pentane foam and is less than 0.
It is 0168 kcal / (mh ° C.), and the heat insulating property is good.
This seems to be due largely to the effect of the thermal conductivity of 2,2,3-trimethylbutane.

Cyclooctatetraene was mixed in place of 1,4-pentadiene to give 2,2,3-trimethylbutane and 2,2,3-trimethylbutane.
When foamed with a ternary mixture of 2-dimethoxypropane and cyclooctatetraene (about 60: 35: 5% by weight), a similarly good foam is formed in the conventional manner, Due to its low thermal conductivity, the thermal conductivity of foam is 0.0166kcal / (mh ℃)
Became even lower.

In this way, by using the foaming agent which is a azeotropic mixture by combining the compounds which do not satisfy the requirements as the urethane foaming agent alone, a heat insulating foam exhibiting the conventional effect or more is obtained. I was able to.

[0066]

As described above, the present invention is a heat-insulating foam obtained by foaming and molding a rigid polyurethane using a foaming agent containing a quaternary carbon having 6 to 7 carbon atoms as a main component. Generally, a compound having a high molecular weight and a low thermal conductivity, but having a high boiling point, which cannot be used as a urethane foaming agent, can be used as a foaming agent by changing the molecular structure of a compound having quaternary carbon. .

The heat-insulating foam of the present invention is used as a foaming agent using a mixture of a saturated hydrocarbon having 6 carbon atoms and a polar compound having a molecular weight similar to that of the hydrocarbon, to form a rigid polyurethane by foam molding. There is an effect that a hydrocarbon having 6 carbon atoms having a low rate but an excessively high boiling point can be used as a foaming agent by lowering the boiling point by utilizing the azeotropic property of both.

Further, there is also an effect that the heating temperature when used as a foaming agent is lowered by azeotropy, and charring, cracks and the like due to reaction of polyurethane can be reduced.

Further, the heat insulating foam of the present invention was prepared by adding 7 carbon atoms.
Of a saturated polyurethane, an ether compound having a molecular weight similar to that of the saturated hydrocarbon, and an unsaturated hydrocarbon having a carbon number of 5 to 8 as a foaming agent to foam and mold a rigid polyurethane. By doing so, it became possible to use as a foaming agent by azeotropically distilling a hydrocarbon having 7 carbon atoms having good thermal conductivity characteristics, which was difficult to use even in a binary azeotropic mixture.

Further, by utilizing the foaming agent of the present invention, it is possible to reduce environmental problems such as ozone layer depletion and global warming, and at the same time, it has the effect of retaining heat insulation as a heat insulating material for refrigerators and the like. Is of great industrial value.

[Brief description of drawings]

FIG. 1 is a view showing an example of a heat-insulating box body filled with a rigid polyurethane foam foamed using the foaming agent of the present invention.

FIG. 2 is a view showing a part of a cross section of a heat insulating box for a refrigerator filled with the rigid polyurethane foam of the present invention.

[Explanation of symbols]

 1 Outer box 2 Rigid polyurethane foam 3 Inner box

Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number in the agency FI Technical display location C08G 101: 00) C08L 75:04 (72) Inventor Fumakuta Inagaki 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Within the corporation

Claims (9)

[Claims] 1. A foaming agent containing, as a main component, a hydrocarbon having quaternary carbon and having at least one of 6 and 7 carbon atoms,
A heat insulating foam comprising a rigid polyurethane foam contained in cells. 2. The heat insulating foam according to claim 1, wherein the main component of the foaming agent is a hydrocarbon having a tertiary butyl structure and having at least one of 6 and 7 carbon atoms. 3. The main component of the foaming agent is neohexane,
The heat insulating foam according to claim 1. 4. The adiabatic foam according to claim 1, wherein the foaming agent is a hydrocarbon mixture containing at least one of neohexane and 3,3-dimethyl-1-butene as a main component. body. 5. A rigid polyurethane foam comprising a foaming agent containing in the cells an azeotropic mixture of a saturated hydrocarbon having 6 carbon atoms and an ether compound having the same molecular weight as the saturated hydrocarbon. A heat insulating foam characterized by the above. 6. A ternary azeotropic mixture comprising a saturated hydrocarbon having 7 carbon atoms, an ether compound having a molecular weight similar to that of the saturated hydrocarbon, and an unsaturated hydrocarbon having 5 to 8 carbon atoms. A heat insulating foam comprising a rigid polyurethane foam containing a foaming agent in cells. 7. The unsaturated hydrocarbon is at least one selected from 1-pentene, 2-pentene, isoprene, 1,4-pentadiene, 1,3-pentadiene and cyclooctatetraene. Insulation foam. 8. The heat insulation according to claim 5, wherein the ether compound is at least one selected from ethyl isopropyl ether, tertiary butyl methyl ether, ethyl propyl ether, allyl ethyl ether, and dimethoxymethane. Foam. 9. A box for a refrigerator having an injection port formed by combining a metal outer box and a hard resin inner box, wherein the rigid polyurethane foam is filled.
The heat insulating foam according to any one of claims.