JP2000281744A - Rigid polyurethane foam and heat-insulation treatment process for article using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rigid polyurethane foam which has an excellent applicability and shows an excellent flame retardance after expansion curing, and a heat-insulation treatment process for an articles using the foam, which meets the requirements for flame retardance and is unaffected by the ambient temperature. SOLUTION: This rigid polyurethane foam comprises a polyol component mainly comprising a resol resin and/or benzyl ether type phenol resin and an aromatic polyol, and a polyisocyanate as essential components, is obtained by allowing these two essential components to react in the presence of a curing catalyst, a foam stabilizer and a foaming agent. Here, the proportion of the resol resin and/or benzyl ether type phenol resin blended in the polyol component is from 10 to 50 wt.%, and the proportion of the aromatic polyol blended in the polyol component is from 20 to 90 wt.%. The curing catalyst contains a tertiary amine catalyst and an acid block type temperature-sensitive catalyst comprising a carboxylic acid salt of a tertiary amine.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a rigid polyurethane foam and a method for maintaining and cooling a product using the same. More specifically, the present invention relates to a rigid polyurethane foam having excellent workability and excellent flame retardancy, and a method for maintaining and cooling an article which meets the requirements of flame retardancy and is not affected by environmental temperature.

[0002]

2. Description of the Related Art Rigid polyurethane foam is known as a heat insulating material. The rigid polyurethane foam can be obtained by reacting a composition containing a polyol and a polyisocyanate as main components in the presence of a catalyst, a foam stabilizer, and if necessary, other compounding agents.

[0003] Rigid polyurethane foams are used to keep articles warm and cool over a wide temperature range. In particular,
Rigid polyurethane foams have excellent heat insulating properties at cryogenic temperatures, and are therefore used for various types of refrigeration at cryogenic temperatures.

[0004] On the other hand, rigid polyurethane foams generally have a flammable property, and therefore are required to be flame-retardant when used in a heat-retaining structure such as a plant facility.

[0005] In response to this demand, various techniques for imparting flame retardancy to rigid polyurethane foams have been proposed.
It has also been proposed to use, for example, a polyisocyanurate foam, a phenol foam or the like as a flame-retardant plastic foam that can be injected and foamed.

As one of such techniques, there is a method of using a liquid phenol resin as a part of a raw material to improve flammability by phenol-modifying the obtained rigid polyurethane foam.

For example, Japanese Patent Publication No. Sho 63-32086 discloses that a benzyl ether type phenol resin which is considered to function as a polyol, and an aromatic polyisocyanate and an aliphatic polyisocyanate are selected.
A technique for obtaining a flame-retardant rigid polyurethane foam is disclosed.

In Japanese Patent Publication No. 2-38088,
Using aromatic polyisocyanate and aliphatic polyisocyanate as polyisocyanate, using benzylic ether type phenol resin as polyol,
Techniques for obtaining flame-retardant rigid polyisocyanurate foams are disclosed.

These techniques are intended to obtain a flame-retardant polyurethane foam by using a benzyl ether type phenol resin as a flame-retardant polyol and selecting an aromatic polyisocyanate as a polyisocyanate. It is.

[0010]

However, foaming these flame-retardant plastic foams at a construction site has the following problems. That is, polyisocyanurate foams and phenol foams generally have a problem that the fluidity of the foam is small in the process of foaming, and the filling property in a narrow space or a space having a complicated shape is low. At low temperatures, it does not react and cure normally, and as a result, the foam shrinks or the required adhesive strength cannot be obtained, which is unsuitable as a plastic foam liquid composition used for heat insulation and cold work. Was.

[0011] Among the flame-retardant rigid polyurethane foams, the phenol-modified rigid polyurethane foam using a liquid phenol resin as a part of the above-mentioned raw materials has particularly high flame retardancy, but benzyl ether used as a polyol. At room temperature or about 20 ° C. or higher, the type phenol resin has a high foaming rate when reacted with a polyisocyanate component, and cannot sufficiently fill a rigid polyurethane foam in a required space,
There is also a problem that the speed of the foaming speed is affected by the temperature of the foaming environment.

This is a serious problem particularly in the case of in-situ foaming where it is difficult to control severe foaming conditions and the environmental temperature during foaming varies. In addition, at a low temperature such as about 10 ° C. or less, if the reactivity is suppressed to the extent that injection foaming can be performed, the reaction and curing do not proceed normally. As a result, poor filling or shrinkage of the foam may occur. There is also a problem that a high adhesive strength cannot be obtained. If a large amount of catalyst is added to solve this problem, there are problems that the foaming speed becomes too high, the fluidity of the foam in the foaming process decreases, and the workability deteriorates.

The present invention has been made in view of the above problems, and meets the demands for rigid polyurethane foams having excellent workability and excellent flame retardancy after foaming and curing, and flame retardancy using these. It is an object of the present invention to provide a method for keeping and cooling an article which is not affected by environmental temperature.

[0014]

Under these circumstances, the present inventors have conducted intensive studies in order to achieve the above object, and as a result, have found that the reaction rate of a benzyl ether type phenol resin is reduced.
Relaxing by using in combination with other aromatic polyether polyols or aromatic polyester polyols,
In addition, while suppressing the initial reactivity so that injection foaming work is possible, considering the work under low temperature, by selecting a catalyst that promotes the curing reaction in the latter stage of the reaction, etc. It has been found that a rigid polyurethane foam having excellent workability and excellent flame retardancy after foaming and hardening, and a method for maintaining and cooling the articles which meet the requirements of flame retardancy and are not affected by environmental temperature can be obtained. Thus, the present invention has been completed.

That is, the invention of claim 1 comprises, as essential components, a resol resin and / or a benzyl ether type phenol resin, a polyol component containing an aromatic polyol as a main component, and a polyisocyanate, both of which are curing catalysts,
A rigid polyurethane foam obtained by reacting in the presence of a foam stabilizer and a foaming agent, wherein the resole resin and / or
Or the compounding ratio of the benzyl ether type phenol resin,
In the polyol component, the mixing ratio of 10 to 50% by weight and the aromatic polyol is 20 to 9% in the polyol component.
0% by weight, and wherein the curing catalyst comprises a tertiary amine catalyst and an acid block type temperature-sensitive catalyst comprising a tertiary amine carboxylate. Things.

The invention according to claim 2 is characterized in that the polyol component further comprises an aliphatic polyol,
It is intended to provide a rigid polyurethane foam containing 30% by weight or less.

The invention according to claim 3 is characterized in that a heat insulating material is coated around the article, and the hard polyurethane foam is formed on the joint of the heat insulating material by foaming and curing to seal the joint. An object of the present invention is to provide a method for maintaining and cooling an article.

According to a fourth aspect of the present invention, there is provided a method for maintaining and cooling an article, wherein the heat insulating material is the rigid polyurethane foam.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the rigid polyurethane foam of the present invention and a method for maintaining and cooling a product using the rigid polyurethane foam will be described in detail.

The rigid polyurethane foam of the present invention comprises a resole resin and / or a benzyl ether type phenol resin, a polyol component having an aromatic polyol as a main component and a polyisocyanate as essential components, both of which are a curing catalyst and a foam stabilizer. And a rigid polyurethane foam obtained by reacting in the presence of a blowing agent, wherein the polyol component contains a specific amount of a resole resin and / or a benzyl ether type phenol resin and a specific amount of an aromatic polyol. And the curing catalyst contains a tertiary amine catalyst and a specific acid block type temperature-sensitive catalyst.

The polyol component used in the present invention contains 10 to 50% by weight of a resole resin and / or a benzyl ether type phenol resin, 20 to 90% by weight of an aromatic polyol, and And 30% by weight or less of an aromatic polyol.

The resole resin and / or benzyl ether type phenol resin used in the present invention plays an important role in imparting flame retardancy to the obtained rigid polyurethane foam.

The compounding amount is usually 1 part in the polyol component.
0 to 50% by weight, preferably 20 to 30% by weight.
If the compounding amount is less than 10% by weight, the effect of obtaining flame retardancy becomes small, and satisfactory flame retardancy cannot be obtained in the obtained polyurethane foam. On the other hand, when the amount exceeds 50% by weight, the reaction speed becomes remarkable, the control of the reaction speed at low temperature becomes difficult, and the flowability of the foam in the foaming process is reduced, resulting in poor workability. Become.

The resole resin used in the present invention includes a condensation polymer obtained from a monovalent phenol such as phenol, cresol and xylenol and an aldehyde such as formaldehyde and paraformaldehyde, or ethylene oxide and propylene oxide. And the like to which an alkylene oxide has been added.

The benzyl ether type phenol resin used in the present invention includes those represented by the following formula.

[0026]

Embedded image

In the formula, R represents a hydrogen atom or a phenolic substituent meta-position to a phenolic hydroxyl group;
n is an integer such that m / n is 1 or more, X represents a hydrogen atom or a terminal group of a methylol group, and the molar ratio between the methylol terminal group and the hydrogen atom is 1 or more.

The aromatic polyol used in the present invention itself has a function of contributing to flame retardancy and a function of alleviating a curing reaction of a resole resin and / or a benzyl ether type phenol resin.

The blending amount of the aromatic polyol is usually 20 to 90% by weight, preferably 50 to 75% by weight, based on the polyol component. When the amount is less than 20% by weight, the effect of reducing the reactivity is weak, and the reaction of the resole resin and / or the benzyl ether type phenol resin is delayed, so that the effect of making the reaction rate appropriate as a whole cannot be obtained. .
On the other hand, if it exceeds 90% by weight, the flame retardancy is reduced as a whole.

The aromatic polyol used in the present invention includes, for example, aromatic polyester polyols obtained by esterification of aromatic carboxylic acids such as phthalic acid and polyhydric alcohols, aromatic amines, polyhydric phenols and the like. And aromatic polyether polyols obtained by adding an alkylene oxide to an active hydroxyl group-containing aromatic compound.

In the present invention, the aliphatic polyol is not an essential component, but is preferably further added to ease the reactivity of the resole resin and / or the benzyl ether type phenol resin. In addition, it is preferable that the compounding quantity is 30 weight% or less in a polyol component. If the amount exceeds 30% by weight, the flame retardancy may decrease.

As the polyisocyanate component used in the present invention, a known polyfunctional polyisocyanate, for example, an aromatic, aliphatic, or alicyclic polyisocyanate, or a mixture thereof or a modified form thereof can be used. And the like.

Of these, aromatic polyisocyanates such as 2,4 tolylene diisocyanate, 2,6 tolylene diisocyanate, 4,4 ′ diphenylmethane diisocyanate (MDI), and polymethylene polyphenyl isocyanate (crude MDI) are preferred. Methylene polyphenyl isocyanate is more preferred.

The rigid polyurethane foam of the present invention is obtained by reacting the polyol component and the polyisocyanate in the presence of a curing catalyst, a foam stabilizer, a foaming agent, and other compounding agents used in the production of ordinary polyurethane foam. Manufactured.

The curing catalyst used in the present invention includes a tertiary amine catalyst for accelerating the reaction between the aromatic polyol and the polyisocyanate and an acid block type thermosensitive catalyst comprising a tertiary amine carboxylate. It is a thing.

The tertiary amine catalyst used in the present invention is not particularly limited, and includes, for example, a tertiary amine catalyst usually used for producing a rigid polyurethane foam. Specifically, triethylamine, N,
N'-dimethylcyclohexylamine, N, N, N ',
N'-tetramethyl 1,3-propanediamine, N,
N, N ', N'-tetramethylhexanediamine, N,
N, N ', N', N "-pentamethyldiethylenetriamine, triethylenediamine, etc. The amount of the tertiary amine catalyst is 0.1 to 0.5% by weight based on the polyol component. is there.

The acid-blocking type temperature-sensitive catalyst used in the present invention comprises a carboxylic acid salt of a tertiary amine, and is further added to a usual tertiary amine catalyst acting on the reaction between polyisocyanate and polyol. It functions as a catalyst when the foaming reaction has progressed to some extent due to the heat of reaction between the aromatic polyol and the polyisocyanate.

Examples of the acid block type temperature-sensitive catalyst used in the present invention include carboxylic acid salts of triethylenediamine, carboxylic acid salts of bis (2-dimethylamino-ethyl) ether, and diazabicyclo-7-undecenecarboxylic acid. Examples include carboxylic acid salts of tertiary amines such as acids. Among them, diazabicyclo-7-undecenecarboxylate is preferred. The compounding amount of the acid block type temperature-sensitive catalyst is 0.1 to 0.3% by weight based on the polyol component.

In addition, a metal catalyst such as dibutyltin dilaurate or stannas octoate may be used in combination.

At the time of the curing reaction, the resol resin and / or the benzyl ether type phenol resin have a particularly low reaction rate at a low temperature of about 10 ° C. or less, causing problems such as shrinkage of the foam and poor adhesion. However, increasing the amount of catalyst added to alleviate the problem,
The reaction rate is so fast that the required foam fluidity cannot be obtained. Therefore, in the present invention, the polyisocyanate component and the polyol component are reacted by the action of a normal tertiary amine catalyst, and the acid block type temperature-sensitive catalyst is caused to function by the heat of the reaction. Promotes the reaction with some resole resins and / or benzyl ether phenolic resins.

By doing so, the reaction tends to be rapid,
Relieves the reaction of difficult-to-handle resole resins and / or benzyl ether-type phenolic resins, making them suitable for injection work as a whole, and ensuring good fluidity and curability during foaming even at low temperatures can do.

In addition, the combination of a resole resin and / or a benzyl ether type phenol resin with an aromatic polyol as a polyol and the use of an acid block type temperature-sensitive catalyst in the first step are as follows. The reactivity between the benzyl ether type phenolic resin and the polyisocyanate is relaxed to cause the polyisocyanate to react with the polyol component. In the next step, the action of the acid block type thermosensitive catalyst mainly causes the resole resin and / or the benzyl ether type to react. This is for obtaining the effect of accelerating the curing reaction between the phenol resin and the polyisocyanate.

For example, when only a resole resin and / or a benzyl ether type phenol resin is used as the polyol, the problem relating to the speed of the reaction cannot be overcome. That is, if a large amount of catalyst is added in an attempt to overcome the low reaction rate at low temperatures, the problem that the reaction becomes too fast and the workability deteriorates cannot be overcome.

When only an aromatic polyol is used as the polyol component, the required flame retardancy cannot be obtained. Aromatic polyols contribute to flame retardancy,
It does not reach the flame retardancy of resole resin and / or benzyl ether type phenol resin.

That is, as the polyol, a resole resin and / or a benzyl ether type phenol resin and an aromatic polyol are used in combination, and the compounding amount is a combination of the above-mentioned parts by weight. It is important to use an acid block type temperature-sensitive catalyst.

Examples of the foam stabilizer include organic silicon-based surfactants known for producing rigid polyurethane foams, for example,
SH193 manufactured by Toray Silicone Co., Ltd. can be mentioned. The amount of the foam stabilizer is 1 to 1 with respect to the polyol component.
3% by weight.

As the foaming agent, 1,1-dichloro-1-
Examples thereof include fluoroethane and 1,1-dichloro-2-trifluoroethane. The compounding amount of the foaming agent is 10 to 30% by weight based on the polyol component.

Examples of the flame retardant include halogen-containing phosphoric ester compounds such as tris (2-chloroethyl) phosphate and tris (2-chloropropyl) phosphate. The compounding amount of the flame retardant is 5 to 15% by weight based on the polyol component.

[0049] The rigid polyurethane foams of the present invention are prepared by conventional means. That is, a polyol composition in which an additive other than isocyanate is mixed with the polyol component is prepared, and isocyanate is added thereto, and the mixture is well stirred and mixed to foam and harden. Specifically, it is manufactured by thoroughly mixing and foaming a liquid polyol composition in which a polyol component is blended with additives such as a curing catalyst, a foam stabilizer, a flame retardant, and a foaming agent, and a polyisocyanate. The mixing ratio of the polyisocyanate is such that the equivalent ratio (NCO / OH) of the isocyanate group to the hydroxyl group of the polyol is 1.05 to 1.20.
Is in the range of

The method for keeping and maintaining the temperature of the article according to the present invention is a method of covering the periphery of the article with a heat insulating material and forming the rigid polyurethane foam on the joint of the heat insulating material by foaming and curing to seal the joint. is there. Further, as the heat insulating material used here, those made of the above-mentioned rigid polyurethane foam are preferable. The article is not particularly limited, and includes, for example, an outdoor low-temperature pipe section. In the method for keeping warm and cool the article of the present invention, the above-mentioned raw material forming the rigid polyurethane foam is used for the construction, so that it is not affected by the environmental temperature and ensures good fluidity and curability at the time of foaming. it can.

[0051]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. Examples 1 to 5, Comparative Examples 1 to 6 Table 1 (Examples 1 to 5) and Table 2 in polyethylene containers
First, a polyol composition (stock solution) other than polyisocyanate (crude MDI) was prepared with the composition shown in (Comparative Examples 1 to 6). The preparation was carried out by conventional means, and the components were thoroughly mixed. A mixture of the polyol composition at room temperature and a separately prepared polyisocyanate (crude MDI) in a mixing amount shown in Tables 1 and 2 and high-speed stirring for about 30 seconds, and then a mixed liquid Was injected into a suitable mold and foamed to obtain a rigid polyurethane foam. Table 1 shows the performance of the obtained rigid polyurethane foam.
And Table 2.

In Tables 1 and 2, a resole type liquid phenol resin having a hydroxyl value of 650 mgKOH / g (manufactured by Showa Polymer Co., Ltd.) was used, and a benzyl ether type phenol resin having a hydroxyl value of 490 mgKOH / g (Showa Polymer) (Manufactured by Kobunshi Co., Ltd.) and the aliphatic polyol has an average number of functional groups of 4 and a hydroxyl value of 400 mgKOH /
g (manufactured by Sumitomo Bayer Urethane Co., Ltd.), an aromatic polyester polyol having an average functionality of 3, and a hydroxyl value of 450 mg KOH / g (manufactured by Toho Rika Kogyo Co., Ltd.) was used. The one having 4 functional groups and a hydroxyl value of 450 mgKOH / g (manufactured by Sumitomo Bayer Urethane Co., Ltd.) was used.

[0053]

[Table 1]

[0054]

[Table 2]

In Tables 1 and 2, components other than the polyol are as follows. Catalyst A: N, N, N ', N'-tetramethylhexanediamine ("TOYOCAT MR" manufactured by Tosoh Corporation) Catalyst B: N, N'-dimethylcyclohexylamine ("TOYOCAT DMCH" manufactured by Tosoh Corporation) Catalyst C: diazabicyclo -7-undecenecarboxylate (“SA-102” manufactured by San Apro Co., Ltd.) Catalyst D; dibutyltin dilaurate (“T-12” manufactured by Sankyo Air Products) Flame retardant: tris (2-chloropropyl) phosphate (“Fana Roll PCF (manufactured by Stoffer Japan) Foam stabilizer; ("SH-193" manufactured by Toray Silicone Co., Ltd.) Foaming agent; 1,1-dichloro-1-fluoroethane "HCFC
141b "Central Glass) Crude MDI; NCO Index 115

In Tables 1 and 2, the shrinkage of the foam is measured by measuring the dimensions of the foam immediately after foaming and after 24 hours, and the amount of change is shown in%.

The filling property of the foam is 150 mm width × 3 thickness.
It shows the ratio of the filled height of the foam to the total height of the mold when a certain amount of the liquid composition is injected into a vertical mold of 0 mm × 1000 mm height and foamed in the height direction.

The adhesive strength is a value obtained by measuring the adhesive strength of the obtained polyurethane foam to a rigid polyurethane foam having a density of 40 kg / m ³ .

The after-flame time was determined by elongating the obtained rigid polyurethane foam, vertically supporting it, heating the lower portion with a burner flame for 10 seconds, and moving the lower portion away from the burner flame until the flame disappeared. It is a measure of time.

The weight retention is the ratio of the weight of the burning residue of the rigid polyurethane foam after the burning test to the weight of the rigid polyurethane foam before the burning test.

As is clear from Table 2, in Comparative Example 1, since only the aliphatic polyol was used as the polyol, the flame retardancy was low.

In Comparative Example 2, the flame retardancy was also low because the amount of the aliphatic polyol was too large. The aliphatic polyol has a function of suppressing the reactivity of the phenolic resin, but has a low flame retardancy, and therefore has a weight retention of 5 to several tens%, which makes it extremely easy to burn.

In Comparative Example 3, since the acid block type temperature-sensitive catalyst was not used, the phenol resin was not sufficiently foamed, and the filling property was insufficient.

In Comparative Example 4, since the acid block type temperature-sensitive catalyst was not used, foaming of the phenol resin was not sufficiently performed, the filling property was insufficient, and the adhesive strength was low. Also, the shrinkage of the foam is large.

In Comparative Example 5, since the acid block type temperature-sensitive catalyst was not used, the foaming state of the phenol resin was incomplete and foaming occurred, but the shrinkage of the foam was large.

In Comparative Example 6, since the acid block type temperature-sensitive catalyst was not used, the phenolic resin was incompletely foamed and foamed, but had low adhesive strength and unsatisfactory filling properties and shrinkage. It has become something.

The flame-retardant rigid polyurethane foam shown in this example has a required workability and performance even at a low temperature, and is suitable for use at a construction site.

Embodiment 6 Embodiment 6 is an example in which the method for keeping warm and cool according to the present invention is applied to a cool structure for low-temperature piping. FIG. 1 is an explanatory view schematically showing a cold insulation structure of a pipe obtained by the heat insulation / cooling construction method of the present invention. As shown in FIG. 1, in this cold insulation structure, a two-piece pipe cover 10
2 and 103, and a foamable stock solution for forming a rigid polyurethane foam is injected into the joint portion 104. The heat insulating materials 102 and 103 are, for example, pipe covers made of flame-retardant plastic foam such as polyisocyanurate foam or phenol foam. The pipe covers 102 and 103 are formed in advance at a factory, and are brought to a construction site to perform cold insulation work. The pipe cover 102 and the pipe cover 103 were made of the rigid polyurethane foam of the present invention. In this cold insulation work, the pipe cover 102 and the pipe cover 1
After attaching No. 03, the joint portion 104 was filled with the rigid polyurethane foam obtained in Example 1 by a conventional method. This construction was performed outdoors, and the temperature at this time was 5 ° C.

As a result, a joint material having good fluidity at the time of foaming and sufficient curability after construction could be obtained without being affected by the environmental temperature.

[0070]

As described above, according to the present invention,
To provide a hard polyurethane foam having excellent workability and excellent flame retardancy after foaming and hardening, and a method for maintaining and cooling the articles which meet the requirements of flame retardancy and are not affected by environmental temperature. it can.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a cold insulation structure of a pipe obtained by a heat insulation / cooling construction method according to an embodiment of the present invention.

[Explanation of symbols]

 101 Pipe (Pipe) 102 Heat Insulation Material (Pipe Cover) 103 Heat Insulation Material (Pipe Cover) 104 Joint

Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court II (Reference) (C08G 18/54 101: 00) B29K 105: 04 C08L 75:04 (72) Inventor Yasunori Hattori Tsurumi-ku, Yokohama-shi, Kanagawa 1-70 Ogurocho F-term in Nichias Corporation Tsurumi Research Laboratories (reference) DG18 HA01 HA07 HC12 HC22 HC46 HC52 HC67 HC71 KB02 KB05 NA02 NA08 QC01 RA15

Claims (4)

[Claims] 1. A resole resin and / or a benzyl ether type phenol resin, a polyol component containing an aromatic polyol as a main component, and a polyisocyanate as essential components, both of which are in the presence of a curing catalyst, a foam stabilizer and a foaming agent. A rigid polyurethane foam obtained by reacting with the above, wherein the mixing ratio of the resole resin and / or benzyl ether type phenol resin is 10 to 10 in the polyol component.
50% by weight and the blending ratio of the aromatic polyol are
20 to 90% by weight of the polyol component, and the curing catalyst contains a tertiary amine catalyst and an acid block type temperature-sensitive catalyst composed of a tertiary amine carboxylate. Rigid polyurethane foam. 2. The rigid polyurethane foam according to claim 1, wherein the polyol component further contains an aliphatic polyol in an amount of 30% by weight or less in the polyol component. 3. A heat insulating material is coated around the article, and the joint is sealed by forming the rigid polyurethane foam according to claim 1 on the joint of the heat insulating material by foaming and curing. Method to keep warm and cool cold goods. 4. The method according to claim 4, wherein the heat insulating material is the rigid polyurethane foam according to claim 1 or 2.