JPH03258822A - Preparation of rigid polyurethane foam - Google Patents

Abstract

PURPOSE:To prepare the subject foam having a fine cell structure and having excellent heat-insulating characteristics, low having dimensional stability and compression strength by reacting a specific urethane prepolymer with a polyol in the presence of a substitute of trichloromonofluoromethane, a catalyst and a foam stabilizer. CONSTITUTION:A prepolymer formed from a polymethylenepolyphenylisocyanate and a polyol (e.g. methanol, ethylene glycol monomethyl ether) is reacted with a polyol (e.g. polyetherpolyol having a hydroxyl group value of 300-700mgKOH/ g) in the presence of a substitute of trichloromonofluoride (preferably 1,1- dichloro-2-2,2-trifluoroethane, 1,1-dichloro-1-fluoroethane), a catalyst and a foam stabilizer to provide the objective foam.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a method for manufacturing rigid polyurethane foam.

More specifically, as a blowing agent, a substitute for trichloromonofluoromethane (hereinafter referred to as R-11), preferably 1
．． 1-dichloro-2,2,2-trifluoroethane (hereinafter referred to as HCFC-123) or/and 1.1-
Dichloro-1-fluoroethane (hereinafter referred to as HCFC-14
This invention relates to a method for producing a rigid polyurethane foam having a fine cell structure, excellent heat insulation properties, and excellent low-temperature dimensional stability and compressive strength.

Conventional Technologies and Issues Rigid polyurethane foam is a good heat insulating material and has excellent moldability and processability, so it is used for insulation in electric refrigerators, buildings, and low-temperature warehouses.

It is used in a wide range of fields, including insulation for storage tanks, refrigerated ships, piping, etc. To produce such rigid polyurethane foam, a polyol, a catalyst.

Foam stabilizer 1 A one-shot method in which component A, which has a foaming agent as its main component, and component B, which has incyanate as its main component, are mixed and reacted, and the foaming process and curing process proceed in parallel to form a foam. is commonly used.

The blowing agent used in the production of such polyurethane foam is mainly R-11, and since water reacts with incyanate to generate carbon dioxide, it is used in combination with R-11 as a chemical blowing agent. Often. However, since CFC gas conventionally used as a blowing agent is chemically stable, it diffuses into the stratosphere and destroys the ozone layer existing in the stratosphere. As a result, ultraviolet rays emitted from the sun are not absorbed by the ozone layer and reach the earth's surface, increasing the incidence of skin cancer, which has become a serious environmental problem in recent years.

For this reason, regulations on the use of fluorocarbon gas have been implemented since 1989, and R-11 for polyurethane has also been subject to regulations.

Therefore, various studies have been conducted on foaming agents that can replace fluorocarbon gas, such as HCFC-123,
141b and the like have been proposed as substitutes for R-11. However, these HCFC-1 as blowing agents
Compared to the foam using R-11, the foam using 23,141b has (1) poorer physical properties such as low-temperature dimensional stability and FE shrinkage strength at the same density, and (2) poorer thermal insulation properties. O~l 5 X l O-'kc
There are problems such as (3) slow initial reactivity.

On the other hand, in recent years, when rigid polyurethane foam is used in electric refrigerators, etc., in addition to increasing the internal volume by making the insulation layer thinner, rigid polyurethane foam has a high degree of insulation performance, in other words, to reduce power consumption. There has been a strong demand for lower conductivity. The thermal conductivity of conventional rigid polyurethane foam is 23℃
Usually 140-160 x 10-'kcal/
It is about mh℃, l 30 X l O-'kcal
It is extremely difficult to lower the temperature below /mh℃, especially for HCF
This is extremely difficult when using C-123, 141b.

Means for Solving the Problems In view of the above-mentioned problems, the present inventors conducted intensive studies and found that HCFC-123 or/and H
When producing rigid polyurethane foam using CFC-14lb, by combining a specific polyol and incyanate, it has a fine cell structure with excellent heat insulation properties, and has excellent low-temperature dimensional stability and compressive strength. We have discovered a method for manufacturing rigid polyurethane foam with excellent 7 ohm physical properties, and as a result of further study, we have completed the present invention.

That is, the present invention provides a method for producing a rigid polyurethane foam, characterized in that a prepolymer of polymethylene polyphenylisocyanate and a monool is reacted in the presence of a polyol and a substitute for trichloromonofluoromethane, a catalyst, and a foam stabilizer. Regarding.

The organic polyisocyanate used in the present invention includes:
Polymethylene polyphenylisocyanate (hereinafter referred to as c-
MDI) and monool alone.

Alternatively, a prepolymer obtained by reacting two or more types is used, and if necessary, tolylene diisocyanate (
A prepolymer of TDI (hereinafter referred to as TDI) and a polyol can also be used in combination.

Examples of monools used in the present invention include alcohols such as methanol, ethanol, propatool, n-butanol, pentanol, hexanol, heptatool, octatool, and phenyl alcohol, ethylene glycol monomethyl ether, diethylene glycol monobutyl ether, and triethylene glycol. Monomethyl ether.

Ethylene glycol monoethyl ether, diethylene glycol monoethyl ether, ethylene glycol tesyl ether, ethylene glycol monoallyl ether, ethylene glycol monobenzyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-β-chloroethyl ether, ethylene glycol mono n-hexyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monoethyl ether, diethylene glycol tethyl ether,
Diethylene glycol monobutyl ether, diethylene glycol mono-β-chloroethyl ether, diethylene glycol monochlorohydrin, diethylene glycol 7-n-hexyl ether, diethylene glycol monoisobutyl ether, triethylene glycol decyl ether, triethylene glycol mono-n-butyl ether, triethylene glycol monochlorohydrin Glycol monoalkyl ethers such as dorine, or monools obtained by adding alkylene oxides such as ethylene oxide, propylene oxide, butylene oxide to the above monools can be used. The above prepolymer has an amine equivalent of 140 to 300, and it is particularly desirable to use one with an amine equivalent of 150 or more.

The polyol used in the present invention is a polyol having a functional group number of 2 to 8, which is used in the production of ordinary rigid polyurethane foam.
．． Polyether polyol with hydroxyl value 300-1000m100O/g, number of functional groups 2-4, hydroxyl value 200-5
A polyester polyol of 00 mg KOH/g and a phenol resin having a reactive methylol group are used. Particularly preferred among these polyols are orthotolylene diamine and metatolylene diamine.

4. Polymerization of alkylene oxides, such as ethylene oxide, propylene oxide, butylene oxide, etc. alone or in combination, using aromatic diamines such as 4'-diaminodiphenylmethane as an initiator, resulting in a hydroxyl value of 300 to 700 mgKOH/g. Polyether polyol, hydroxyl value 300-700 mg KOH/g obtained by polymerizing alkylene oxide, such as ethylene oxide, propylene oxide, butylene oxide, alone or in combination, using methyl glucoside as an initiator.
Of polyether polyols, trimethylolpropane as an initiator alkylene oxide, for example! The hydroxyl value obtained by polymerizing tyrene oxide, propylene oxide, butylene oxide, etc. alone or in combination of two or more of them is 450.
It is a polyether polyol of ~1000 mg KOH/g and a phenol resin compound having a methylol group, and other known polyols can also be used in combination.

The blowing agent in the present invention is one used as a substitute for R-11, such as HCFC-123゜HCFC-1
4lb, dodecafluoropentane, etc., especially H
CFC-123 and HCFC-141b are preferred. The amount used is that the density of the polyurethane foam is 15 kg/
The amount is not less than m' and is adjusted depending on the purpose of use, and is usually 5 to 150 parts by weight based on 100 parts by weight of the polyol. In the present invention, water and other known blowing agents that function as both a blowing agent and a crosslinking agent can also be used together.

Typical examples of catalysts used in the present invention are:
For example, tertiary amines such as dimethylethanolamine, triethylenediamine, tetramethylethylenediamine, tetramethylpropanediamine, tetramethylhexamethylenediamine, dimethylcyclohexylamine,
Examples include organometallic compounds such as stannath octoate, dibutyltin dilaurate, and lead octylate. Also, propanediamine if necessary.

Primary amines such as hexamethylene diamine can also be used in combination. The catalyst is usually 0.1 parts by weight per 100 parts by weight of polyol.
-10 parts by weight are used.

Further, as the foam stabilizer, various dimethylsiloxane/polyalkylene oxide block copolymers (silicon-based foam stabilizers) can be used. Foam stabilizer is usually polyol 10
About 0.2 to 10 parts by weight is used relative to 0 parts by weight.

As a specific means for manufacturing rigid polyurethane foam from the above-mentioned raw materials, any device that can mix the raw materials uniformly may be used, but for example, it is possible to use a small experimental mixer, a foaming machine, etc. to uniformly mix the raw materials. Rigid polyurethane foam can be easily obtained by mixing.

Effects of the Invention The rigid polyurethane foam obtained by the present invention has an extremely low thermal conductivity, for example, 120 to 130 X at 23°C.
I O-'kcal/mh'o. Conventional R-
The thermal conductivity of the rigid polyurethane foam obtained using R-11 is on the order of 135-160 XlO-'kcal/mh°C.
Rigid polyurethane foam using 3,141b etc. is even worse, with 140 to 165 X I O-' kc
Since it is about al/mh'c, it is nearly 20% smaller. This means that, for example, when conventional rigid polyurethane foam is used as a heat insulator, what would require a thickness of 1OCm can be reduced to a heat insulating thickness of 8 cm, making it extremely economical, such as electric refrigerators.

When manufacturing showcases, prefabricated refrigerators, freezers, etc., it is possible to improve internal volume efficiency and reduce cooling energy by reducing the thickness of insulation walls. Furthermore, compared to a prepolymer with c-MDI polyol, since it is a prepolymer using a monool, the viscosity is significantly lower for the same amine equivalent, and it has excellent processability such as foam fluidity. Surprisingly, it has been revealed that it has excellent low-temperature dimensional stability at low density.

Hereinafter, the present invention will be explained in more detail with reference to comparative examples and examples.

The raw materials used in the examples are as follows.

Polyol A: Tolylene diamine/ethylene diamine polyether polyol with a hydroxyl value of 500 mg KOH/g Polyol B: Methyl glucoside polyether polyol with a hydroxyl value of 550 mg KOH/g Polyol C
: Trimethylolpropane-based polyether polyol with a hydroxyl value of 880 mg KOH/g Foam stabilizer A: Silicone-based foam stabilizer; F manufactured by Shin-Etsu Chemical Co., Ltd.
-373 Catalyst A: Tetramethylhexamethylenediamine Blowing Agent A
IR-11 Blowing agent B: HCFC-123 Blowing agent C: HCFC-14lb Blowing agent D Water polyisocyanate A: c-MDI (amine equivalent 136
) Polyisocyanate B: A mixture of equal amounts of a prepolymer of c-MDI and polyol (amine equivalent weight 163) and a prepolymer of TDI and polyol (amine equivalent weight 145) Polyisocyanate C: A mixture of c-MDI and diethylene glycol 7-methyl ether Prepolymer (amine equivalent weight 150) and prepolymer of TDI and polyol (
Polyisocyanate D: A prepolymer of c-MDI and diethylene glycol 7-methyl ether (amine equivalent weight 200) and a prepolymer of TDI and polyol (amine equivalent weight 145).
Tables 1 and 2 In accordance with the foaming recipe shown in the table, these raw materials were brought to a temperature of 20 μC and then reacted by high-speed mixing and stirring for 5 seconds. The expanded rigid polyurethane foam was cut and sampled the next day according to conventional methods, and various physical properties were measured.
The results are shown in Tables 1 and 2. The thermal conductivity is a value measured using an ANACON model 88 measuring device at an average temperature of 23°C, the compressive strength is when compressed by 10% in the direction perpendicular to the foaming direction, and the low-temperature dimensional stability is -30%. The dimensional change rate in the direction perpendicular to the foaming direction was measured after cooling at ℃ for 24 hours.

Comparative Examples 1 and 12 used R-11 as a foaming agent, and had a microcell structure and excellent heat insulation properties, so-called microcell formulations, and exhibited very low thermal conductivity. There is. However, as is clear from Comparative Examples 2 and 13, in these formulations, when the blowing agent is increased and the density is reduced to a certain extent, the compressive strength, especially the low temperature dimensional stability, deteriorates significantly and the thermal conductivity also slightly deteriorates. When water is added as a blowing agent to these formulations as shown in Comparative Examples 3 and 14, the compressive strength and low-temperature dimensional stability are improved at a lower density, but the thermal conductivity is now extremely deteriorated. . This also applies when using HCFC-123 (Comparative Examples 4 and 15 and Comparative Example 5.16).
The same can be said when using (Comparative Example 6.17 and Comparative Example 7.18). And Comparative Examples 8, 19, Comparative Example 9,
20 or Comparative Example 10.21, the polyisocyanate was replaced with an equal mixture of c-MDI and a prepolymer of c-MDI and a polyol and a prepolymer of TDI and a polyol, and an amine-based or/ and thermal conductivity by mixing trimethylolpropane polyether polyol with methyl glucoside polyether polyol.

Compressive strength and low-temperature dimensional stability were determined by microcell formulation (
It shows an excellent value comparable to Comparative Example 1.12).

In addition, when a substitute for R-11 is used, the polyisocyanate is a mixture of equal amounts of a prepolymer of c-MDI and n-heptatool (amine equivalent weight 150) and a prepolymer of TDI and polyol (amine equivalent weight 145). (Example 5.10), it can be seen that although the compressive strength decreases, the density can be reduced while maintaining low-temperature dimensional stability and thermal conductivity. Furthermore, when the polyisocyanate is made into a mixture of equal amounts of a prepolymer of c-MDI and diethylene glycol 7-methyl ether (amine equivalent weight 150) and a prepolymer of TDI and polyol (amine equivalent weight 145) (Examples 1 to 3.6 to 8), a rigid polyurethane foam almost similar to the microcell formulation (Comparative Example 1 12) can be foamed.

In the same formulation, when the amine equivalent of the prepolymer of c-MDI and diethylene glycol 7-methyl ether was increased (Examples 4 and 9), the compressive strength was increased.

Thermal conductivity can be lowered to some extent, although low-temperature dimensional stability is slightly deteriorated. However, R-11 as a blowing agent
When the above-mentioned polyisocyanate is used, the obtained foam is brittle and the adhesive strength is weak, so that it cannot be put to practical use (Comparative Example 11).

(Margin below)

Claims (1)

[Claims] A method for producing a rigid polyurethane foam, characterized in that a prepolymer of polymethylene polyphenylisocyanate and a monool is reacted in the presence of a polyol and a substitute for trichloromonofluoromethane, a catalyst, and a foam stabilizer.