JPH08231667A - Preparation of hard foam - Google Patents

Abstract

PURPOSE: To provide a process for preparing homogeneous hard foam using cyclopentane as a foaming agent by first converting a mixture comprising a polyol, a foaming agent, and a catalyst into a stable emulsion dispersion system. CONSTITUTION: A process for preparing a hard foam by reacting a starting material comprising at least two components, i.e., a first component comprising a polyol, cyclopentane, water, and a catalyst and a second component comprising a polyisocyanate, wherein the first component is converted into a stable emulsion dispersion system before being reacted with the second component. The emulsion dispersion system is pref. such that cyclopentane constitutes a dispersoid with other components, such as polyol and water, constituting a dispersion medium. The particle diameter is pref. less than 2μm. The amount of water used is pref. 0.6 to 1.5% by weight based on the whole active hydrogen compd. (except for water). The polyol pref. has an arom. ring.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing rigid foam. Further, the present invention provides a heat insulating material for an electric refrigerator using cyclopentane as a foaming agent.

[0002]

2. Description of the Related Art Recently, HCFC-141b (1,2) has been used as a foaming agent to prevent the destruction of the ozone layer by specific CFCs.
1-dichloro-1-fluoroethane) and water (foaming by CO ₂ gas by-produced in the reaction with isocyanate) have been used. However, in the latter case, since the thermal conductivity of this CO ₂ gas deteriorates, its use is limited and it is not suitable for a heat insulating material for an electric refrigerator.

Since HCFC-141b has a large ozone depletion potential (ODP) of 0.11, and the ODP has a large time dependency, movements to limit its use are occurring in Europe and the United States.

[0004]

Cyclopentane is already used as a blowing agent mainly in Europe. The reason is that ODP = 0. However, this cyclopentane itself is an oil that is one of the components contained in gasoline, and since polyols for rigid foams are generally highly hydrophilic, in order to produce a uniform foam,
It is necessary to improve the mixing property of the cyclopentane and the rigid foam polyol. At the same time, since the thermal conductivity of cyclopentane itself is higher than that of HCFC-141b, it is necessary to make the bubbles in the foam smaller to reduce the effect of radiative heat transfer and lower the thermal conductivity.

[0005]

Means for Solving the Problems As a result of repeated studies by the present inventors in order to solve the above-mentioned problems, when cyclopentane is used as a foaming agent, the hydrophobic property of itself is In consideration of the balance of hydrophobicity / hydrophilicity with the polyol, it has been found that it is necessary to make the cells in the foam uniform and fine in order to improve the heat insulating property.

It has been found that in order to make the cells in the foam uniform and fine, the mixture components of the polyol, blowing agent and catalyst form a stable emulsion dispersion. The present invention is the following invention.

(1) Polyol, cyclopentane, water,
And a method of producing a rigid foam by reacting a raw material comprising at least two components of a first component containing a catalyst and a second component containing (2) a polyisocyanate, wherein the first component is previously stabilized. After forming an emulsion dispersion system, it is reacted with the second component,
Method for manufacturing rigid foam.

The rigid foam of the present invention includes rigid polyurethane foam, urethane-modified rigid polyisocyanurate foam, urethane-modified rigid polyurea foam,
Other rigid foams may be mentioned. Hereinafter, the rigid polyurethane foam will be described for convenience, but the present invention is not limited thereto.

(Emulsion dispersion type) rigid polyurethane foam is usually (1) polyol, cyclopentane,
It is produced by reacting a raw material composed of at least two components of water and a first component containing a catalyst and (2) a second component containing a polyisocyanate. In the present invention, water and cyclopentane are foaming agents. The present invention is the first
It is characterized in that the component is made into a stable emulsion dispersion system in advance and then reacted with the second component.

A stable emulsion dispersion can be obtained by vigorous stirring, for example, stirring at a relatively high rotation speed of a stirrer, or addition of an additive such as a surfactant. . Here, "stable emulsion dispersion system" means that it does not easily separate,
It is necessary to maintain the emulsion dispersion system without separation even if left at room temperature for 24 hours.

Here, the emulsion dispersion system preferably uses cyclopentane as a dispersoid and other components such as polyol and water as a dispersion medium.

In the fields of conventional foaming agents CFC-11 (trichlorofluoromethane) and HCFC-141b, active hydrogen compound components are generally homogeneously dissolved.
However, in the field of using cyclopentane as a foaming agent, it has been necessary to pay attention to how to efficiently mix hydrophobic cyclopentane with hydrophilic polyol as described above. The present inventors have found that if this cyclopentane is an emulsion dispersion system in which particles are dispersed in a polyol, its heat insulating property is improved as compared with the case of a homogeneous dissolution system, that is, cyclopentane particles dispersed in an emulsion dispersion system is a polyol. It was found that fine bubbles are likely to be formed during the mixing reaction of the isocyanate with isocyanate.

The particle size of the dispersoid is preferably less than 2 μm. Particularly, it is preferably 1.5 μm or less, and about 1 μm or less. The particle size can be measured with an optical microscope or the like.

The amount of water used is 0.6 to 1.5% by weight, especially 0.8 to 1.5% by weight, based on all active hydrogen compounds (excluding water).
It is preferably 1.2% by weight. The amount of cyclopentane used is preferably 15 to 25% by weight, particularly 17 to 22% by weight, based on all active hydrogen compounds (excluding water).

The particle size is considered to be affected by the amounts of cyclopentane and water used. For example, when the amount of cyclopentane used is small, that is, 8% by weight based on the total polyol.
Below, it becomes a homogeneous dissolution system, and as the amount of cyclopentane used increases, that is, from 13% by weight to 15% by weight, and the particle size becomes from about 4 μm to 2 μm, and when it is 15% by weight or more, it becomes fine. , That is, less than 2 μm.

(Polyol) In the present invention, a polyether polyol and / or a polyester polyol is used as the polyol.

As the polyether polyol, those obtained by reacting a cyclic ether with an initiator such as a polyhydric alcohol, a saccharide, an alkanolamine, a polyamine or a phenol are preferable. Preferred cyclic ethers are alkylene oxides such as propylene oxide, butylene oxide and ethylene oxide. A combination of propylene oxide and ethylene oxide is particularly preferable. In order to make the end of the polyether polyol a primary hydroxyl group, it is preferable to react propylene oxide and then react with ethylene oxide to contain an oxyethylene group at the end.

Examples of the polyhydric alcohol as an initiator include ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, glycerin, trimethylolpropane and pentaerythritol. As sugars, sucrose, dextrose,
There is sorbitol etc. Examples of the alkanolamine include diethanolamine and triethanolamine. Examples of polyamines include ethylenediamine and tolylenediamine. Examples of phenols include bisphenol A.

As the polyether, a polyether polyol having an aromatic ring is particularly preferable. Polyether polyols having an aromatic ring are obtained by using a compound having an aromatic ring as an initiator.

Examples of polyester polyols include polyhydric alcohol-polyhydric carboxylic acid condensation type polyols and cyclic ester ring-opening polymer type polyols. As the polyhydric alcohol, those mentioned above can be used. Examples of polycarboxylic acids include adipic acid and phthalic acid. Examples of cyclic esters include lactones. It is particularly preferable to use a polyester polyol having an aromatic ring. This can be obtained, for example, by using a polycarboxylic acid having an aromatic ring. Polyvalent carboxylic acids having an aromatic ring include phthalic acid.

The hydroxyl value of the polyol is preferably 250 to 800, and particularly preferably 350 to 600. You may mix and use a polyol.

In addition to the above-mentioned polyols, small amounts of active hydrogen compounds such as alkanolamines, polyamines and compounds having phenolic hydroxyl groups (eg phenol resin initial condensation products) can be used.

It is believed that a suitable reaction rate is required to generate fine cells in the polyurethane foam.
For that purpose, it is preferable to increase the initial reactivity of the polyol, and for that purpose, it is preferable that the hydroxyl group of the polyol is a primary hydroxyl group. It is also preferable to increase the compatibility between the polyol and the polyisocyanate as a measure for improving the reactivity between the polyisocyanate and the polyol. For that purpose, it is preferable to use a polyol having an aromatic ring as the polyol.

In the present invention, it is particularly preferable to use a polyether polyol having an aromatic ring as a polyol and a polyester polyol having an aromatic ring in combination. in this case,
The weight ratio of both is preferably 95/5 to 80/20.

Most preferably in the present invention, the polyol is 50 to 85% by weight of a polyether polyol having an aromatic ring initiated by an aromatic amine such as tolylenediamine, and a polyol having an aromatic ring initiated by bisphenol A. 1 to 20% by weight of an ether polyol, 5 to 15% by weight of a polyester polyol having an aromatic ring, and 0 to 15% by weight of another polyol are polyol mixtures.

(Polyisocyanate) Polyisocyanate is an aromatic type having two or more isocyanate groups,
There are alicyclic or aliphatic polyisocyanates, mixtures of two or more kinds thereof, and modified polyisocyanates obtained by modifying them.

Specifically, for example, polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, polymethylene polyphenyl isocyanate, xylylene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, and their prepolymer type modified forms and nurate modified forms. , Urea metamorphosed. Of these, tolylene diisocyanate,
Those having an aromatic ring, such as diphenylmethane diisocyanate and polymethylene polyphenyl isocyanate, are preferable in terms of good compatibility with the polyol.

When reacting a polyol with a polyisocyanate, it is usually necessary to use a catalyst. As the catalyst, a metal compound catalyst such as an organotin compound that promotes the reaction between an active hydrogen-containing functional group and an isocyanate group or a tertiary amine catalyst such as triethylenediamine is used.
Further, a multimerization catalyst for reacting isocyanate groups with each other such as carboxylic acid metal salt is used according to the purpose.

Further, a foam stabilizer for forming good bubbles is often used. Examples of the foam stabilizer include a silicone type foam stabilizer and a fluorine-containing compound type foam stabilizer. Other optional additives include fillers, stabilizers, colorants, flame retardants and the like.

[0030]

EXAMPLES Examples (Examples 1 to 3) and Comparative Examples (Examples 4 to 4)
The present invention will be specifically described with reference to 7), but the present invention is not limited thereto. In the following, "part" means "part by weight". The polyols used are shown in Table 1. PO is propylene oxide and EO is ethylene oxide.

Example 1 A polyol mixture weighed at a composition ratio shown in Table 2 in a 3 liter vacuum emulsification stirrer in an explosion-proof facility (Table 2 shows the hydroxyl value of the polyol mixture,
The same applies hereinafter) 100 parts of silicone-based foam stabilizer 2.0
Parts, catalyst 3.0 parts, water 1.0 part and cyclopentane 1
About 1 liter of 9 parts was added, and the mixture was stirred for about 30 minutes to emulsify. It was confirmed by an optical microscope that the emulsion obtained was one in which cyclopentane was dispersed in a particle size of about 1 μm using a polyol as a dispersion medium.

Subsequently, a predetermined amount of the above emulsion was weighed using an air-driven stirrer in an explosion-proof facility, and this was mixed with a polyisocyanate compound (C / MD manufactured by Nippon Polyurethane).
I) was adjusted to a liquid temperature of 20 ° C., mixed at 3000 rpm with an isocyanate index = 115, and 400 mm × 4
It was injected and foamed in a mold of 00 mm × 50 mm (t).
The mold temperature is 40 ° C. Thermal conductivity of the obtained rigid polyurethane foam (unit: kcal / m · hr ·
° C). Table 2 shows the results.

(Example 2) From the beginning, 100 parts of a polyol mixture, which was weighed at a composition ratio shown in Table 2 by using an air-driven stirrer in an explosion-proof facility, was further added with a silicone type foam stabilizer 2.0.
Parts, catalyst 3.0 parts, water 0.9 parts and cyclopentane 2
A predetermined amount of 0 parts was added, taken, and mixed and stirred for 1 minute at 3000 rpm to emulsify. It was confirmed by an optical microscope that the obtained emulsion was prepared by dispersing cyclopentane in a particle size of about 1 μm using a polyol as a dispersion medium. Then, using the same air-driven stirrer, a rigid polyurethane foam was obtained by molding into a mold in the same manner as in Example 1. The thermal conductivity was measured, and the results are shown in Table 2.

(Example 3) In the same manner as in Example 1, 100 parts of the polyol mixture, which was weighed at the composition ratio shown in Table 2 by using a vacuum emulsifying stirrer in an explosion-proof facility, was further added with a silicone foam stabilizer 2.
A predetermined amount of a mixture of 0 parts, 3.0 parts of catalyst, 0.9 parts of water and 20 parts of cyclopentane was weighed and mixed and stirred for about 30 minutes to emulsify. It was confirmed by an optical microscope that the emulsion obtained was one in which cyclopentane was dispersed in a particle size of about 1 μm using a polyol as a dispersion medium. Subsequently, a rigid polyurethane foam was obtained by molding into a mold in the same manner as in Example 1 using an air-driven stirrer. The thermal conductivity was measured, and the results are shown in Table 2.

Example 4 From the beginning, 100 parts of a polyol mixture, which was weighed at the composition ratio shown in Table 2 by using an air-driven stirrer in an explosion-proof facility, was further added with a silicone type foam stabilizer 2.0.
Parts, catalyst 3.0 parts, water 1.0 part and cyclopentane 1
A predetermined amount of 9 parts added was weighed and 1000 r for 1 minute.
The mixture was mixed and stirred at pm to emulsify. It was confirmed by an optical microscope that the emulsion obtained was one in which cyclopentane was dispersed in a particle size of about 10 μm using a polyol as a dispersion medium.

When a part of the obtained emulsion was left overnight at room temperature, cyclopentane floated on the surface, and separation of cyclopentane was observed.

The remaining emulsion was molded into a mold in the same manner as in Example 1 using the same air-driven stirrer to obtain a rigid polyurethane foam. Measure its thermal conductivity,
The results are shown in Table 2.

(Example 5) From the beginning, 100 parts of a polyol mixture, which was weighed at a composition ratio shown in Table 2 using an air-driven stirrer in an explosion-proof facility, was further added with a silicone foam stabilizer 2.0.
Parts, catalyst 2.5 parts, water 1.3 parts and cyclopentane 1
Weigh a predetermined amount of 3 parts and add 3000 parts for 1 minute.
The mixture was mixed and stirred at pm to emulsify. It was confirmed by an optical microscope that the emulsion obtained was one in which cyclopentane was dispersed in a particle size of about 2 μm using a polyol as a dispersion medium. Then, using the same air-driven stirrer, a rigid polyurethane foam was obtained by molding into a mold in the same manner as in Example 1. The thermal conductivity was measured, and the results are shown in Table 2.

(Example 6) As in Example 5, 100 parts of a polyol mixture, which was weighed at the composition ratio shown in Table 2 by using an air-driven stirrer, was further added with 2.0 parts of a silicone type foam stabilizer and 2.5 parts of a catalyst. Parts, 1.7 parts of water and 8 parts of cyclopentane were weighed in a predetermined amount and mixed and stirred for 1 minute at 3000 rpm to emulsify. It was confirmed by an optical microscope that the emulsion obtained was one in which cyclopentane was dispersed in a particle size of about 4 μm using a polyol as a dispersion medium. Example 1
Molded in the same manner as above to obtain a rigid polyurethane foam. The thermal conductivity was measured, and the results are shown in Table 2.

(Example 7) In the same manner as in Example 5, 100 parts of the polyol mixture, which was weighed at the composition ratio shown in Table 2 using an air-driven stirrer, was further added with 2.0 parts of a silicone type foam stabilizer and 3.2 parts of a catalyst. Parts, 1.0 part of water and 19 parts of cyclopentane were added, and a predetermined amount was weighed and mixed and stirred for 1 minute at 3000 rpm. This was a homogeneous dissolution system. Molded in the same manner as in Example 1 to obtain a rigid polyurethane foam. The thermal conductivity was measured, and the results are shown in Table 2.

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

Industrial Applicability According to the present invention, a rigid foam can be produced by a hydrocarbon-based foaming agent having no danger of depleting the ozone layer.

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08L 75:04

Claims (6)

[Claims] 1. A polyol, cyclopentane, water,
And a method of producing a rigid foam by reacting a raw material comprising at least two components of a first component containing a catalyst and a second component containing (2) a polyisocyanate, wherein the first component is previously stabilized. After forming an emulsion dispersion system, it is reacted with the second component,
Method for manufacturing rigid foam. 2. The method according to claim 1, wherein the emulsion dispersion system is an emulsion dispersion system using cyclopentane as a dispersoid and a polyol as a dispersion medium. 3. The particle size of the dispersoid of the emulsion dispersion system is 2 μm.
The manufacturing method according to claim 1 or 2, which is less than m. 4. The method according to any one of claims 1 to 3, wherein the amount of cyclopentane used is 15 to 25% by weight based on all active hydrogen compounds (excluding water). 5. The method according to claim 1, wherein the amount of water used is 0.6 to 1.5% by weight based on all active hydrogen compounds (excluding water). 6. The method according to claim 1, wherein at least a part of the polyol is a polyester polyol having an aromatic ring.