JPH06199983A - Production of rigid polyurethane foam - Google Patents

Abstract

PURPOSE:To obtain the subject foam, having a low thermal conductivity, excellent in low-temperature dimensional stability and strength and useful as a heat insulating material, etc., by reacting a specific polyol with a specified foaming agent, a specific organic polyisocyanate, a specified catalyst and a specific foam stabilizer, etc. CONSTITUTION:The objective foam is obtained by reacting (A) an organic polyisocyanate such as diphenylmethane diisocyanate with (B) a polyol partially prepared by reacting an alkylene glycol having >=2 hydroxyl groups and 800-2000 hydroxyl value such as monoethylene glycol with an organic polyisocyanate containing >=2 isocyanate groups such as 2,4-tolylene diisocyanate in an amount of 1/2 equiv. and/or below based on the alkylene glycol used in an amount of 1-70 pts.wt. based on 100 pts.wt. polyol, (C) a foaming agent such as 1,1- dichloro-l-fluoroethane in an amount of preferably 10-70 pts.wt. [based on 100 pts.wt. component (B)], (D) a catalyst, (E) a foam stabilizer and (F) other assistants.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a polyurethane foam. More specifically, the present invention relates to a method for producing a polyurethane foam which has good strength while reducing or substituting the use of specific freon and chlorofluorocarbons as a foaming agent and having low thermal conductivity.

[0002]

2. Description of the Related Art Polyurethane foams, especially rigid urethane foams, are widely used as heat insulating materials for refrigerators, frozen warehouses, constructions, etc. because of their excellent heat insulating properties and dimensional stability at low temperature. As is well known, it is widely practiced to react a polyisocyanate compound and an active hydrogen compound having two or more active hydrogen groups in the presence of a blowing agent to produce a polyurethane foam. Due to the heat generated during the polymerization reaction, the foaming agent is vaporized to obtain a low density foam having fine cells. In these reactions, usually, two liquids of a polyisocyanate compound and an active hydrogen compound in which necessary additives such as a foaming agent, a foam stabilizer and a catalyst are dissolved in advance are collision-mixed through a foaming machine into a mold. It is done by injection. The properties of the obtained polyurethane foam are determined by appropriately selecting the polyisocyanate raw material and the active hydrogen compound raw material.
Conventionally, polyhydroxy compounds and polyamine compounds have been known as active hydrogen compounds for rigid polyurethane foams. As an example of the polyhydroxy compound, a polyether polyol obtained by adding propylene oxide to a sucrose / glycerin / tolylenediamine mixture is known. These conventionally known polyether polyols have a moderate solubility with trichlorofluoromethane (hereinafter abbreviated as R-11), and by using R-11 as a foaming agent, heat conduction having an extremely fine cell structure can be obtained. It is possible to produce rigid polyurethane foams with low rates.
That is, R-11 has been conventionally suitably used as the foaming agent because of its excellent foaming characteristics. Further, by using chlorofluorocarbons represented by R-11, it is possible to reduce the viscosity of the resin raw material, and there is an advantage that not only the workability but also the compatibility with the isocyanate is improved.

[0003]

However, in recent years, it has been reported that chlorofluorocarbons are so stable that they reach the stratosphere without being decomposed on the ground surface and destroy the ozone layer which blocks harmful ultraviolet rays. It was Therefore, in order to protect the earth's ozone layer, restrictions on the use of chlorofluorocarbons have been considered and are about to be implemented. This regulation target also includes R-11 which has been used as a foaming agent for rigid urethane foam until now.
It has already been decided that these specified CFCs will be abolished at the end of 1995. Therefore, as a foaming agent replacing R-11, monochlorodifluoromethane (hereinafter abbreviated as R-22), 1-chloro-1,1-difluoroethane (hereinafter R
-142b), 2,2-dichloro-1,1,1-trifluoroethane (hereinafter abbreviated as R-123), 1,1-dichloro-1-fluoroethane (hereinafter abbreviated as R-141b)
Such as chlorofluorocarbons having a low ozone depletion potential (hereinafter abbreviated as ODP), and HCFCs having a zero ODP such as 1,1,1,2-tetrafluoroethane (hereinafter abbreviated as R-134a) (hereinafter alternative CFCs). There is an urgent need for development. It is well known that the development of urethane foam using these foaming agents has become an urgent task accordingly.

However, when the above alternative CFCs are used as the foaming agent, 1) the initial reactivity is delayed and 2) the foaming efficiency is lowered as compared with the foam foamed using the conventional R-11. ) The physical properties of foam such as low-temperature dimensional stability and compressive strength are deteriorated. 4) High thermal conductivity (K factor) 5) Various problems such as decrease in resin premix viscosity occur, and conventional rigid urethane foam raw materials cannot provide good foams suitable for practical use.
The present invention has been made for the purpose of improving the above-mentioned problems, and an object thereof is to provide a method for producing a polyurethane foam having good strength and low thermal conductivity even when a CFC substitute is used. Especially.

[0005]

Means for Solving the Problems As a result of intensive studies for achieving the above object, the present inventors have found that if a specific urethane group-containing polyol is used as a polyol raw material, R
It was found that it is possible to produce a good polyurethane foam that solves all of the problems 1) to 5) described above even when an alternative CFC substitute for -11 is used as a blowing agent, and the present invention provides It was completed. That is, the present invention provides a rigid polyurethane foam produced from an organic polyisocyanate, a polyol, a foaming agent, a catalyst, a foam stabilizer and other auxiliaries, wherein a part of the polyol has a hydroxyl value of 80 or more and at least two hydroxyl groups.
It is obtained by reacting an alkylene glycol of 0 to 2000 with an organic polyisocyanate containing at least two isocyanate groups of ½ equivalent and less than that of alkylene glycol, and the amount thereof is used. It is 1 to 70 parts by weight per 100 parts by weight of a polyol, and relates to a rigid polyurethane foam characterized by using hydrochlorofluorocarbon as a foaming agent.

The present invention will be described in detail below. As the organic polyisocyanate raw material used in the present invention, all known materials can be used, but the most common ones are toluene diisocyanate (hereinafter abbreviated as TDI) and / or diphenylmethane diisocyanate (hereinafter abbreviated as MDI). Is. TDI is a mixture of isomers, namely 2,4-body 100
% Product, 2,4-body / 2,6-body = 80/20 and / or 65/35 (each weight ratio), etc., and contains a polyfunctional tar known as Mitsui TDI-TRC. So-called crude TDI can also be used. As MDI, in addition to a pure product containing 4,4'-form as a main component, a trade name Mitsui Cosmonate M- containing a polynuclear body having three or more nuclides
So-called polymeric MDIs such as 200 are particularly preferably used. Further, a prepolymer having an isocyanate group obtained from these organic polyisocyanate and a polyol described below at the molecular end can also be used as a part or all of the organic polyisocyanate.

The urethane group-containing polyol used in the present invention is an alkylene glycol having at least two or more hydroxyl groups and a hydroxyl value of 800 to 2000, and an isocyanate equivalent to 1/2 equivalent or less with respect to the alkylene glycol. It is obtained by reacting an organic polyisocyanate containing at least two groups.

The organic polyisocyanate used when synthesizing the urethane group-containing polyol is TDI.
(2,4-tolylene diisocyanate and / or 2,
6-Tolylene diisocyanate) is preferably used. Also, 4,4'-diphenylmethane diisocyanate alone or a mixture with the above isocyanate in any ratio can be used. The polyol used when synthesizing the urethane group-containing polyol has a hydroxyl value of 800 to 200 having at least two hydroxyl groups.
Low molecular weight alkylene glycols of 0 can be used. Specifically, it is one kind or a mixture of two or more kinds selected from monoethylene glycol, monopropylene glycol, diethylene glycol, dipropylene glycol, glycerin and diglycerin.

The low molecular weight alkylene glycol component is appropriately determined in view of compatibility with CFCs and the number of functional groups. For example, when the solubility in polyol such as R-123 or 141b is better than that in R-11, monoethylene glycol and / or diethylene glycol having strong hydrophilicity are preferably selected. Also R-123
Alternatively, when R-141b is used as a foaming agent, R-1
Compared with 1, the low temperature dimensional stability is significantly reduced. In this case, the improvement effect is recognized by using glycerin having a high number of functional groups. The low molecular weight alkylene glycol is preferably used after dehydration drying, but a trace amount of water present in the system may be intentionally reacted. In this case, it has a part of urea bond. Further, the reaction may be carried out under the condition that allophanate and buret reaction occur with respect to the urethane and urea bonds contained in the polyol.

Although these urethane group-containing polyols are unstable in a certain composition, an organosilicon-based or other surfactant having a terminal hydroxyl group and / or a terminal alkyl group is added during the reaction for the purpose of stabilization. As a result, a stable urethane group-containing polyol can be obtained.
The viscosity of these urethane group-containing polyols is appropriately determined by setting the hydroxyl value. Especially R-123, R-1
In the alternative CFC 41b, which is more compatible with the polyether polyol as compared with the conventional R-11, the decrease in the viscosity when the resin premix is used is obvious. Therefore, there may be a case where a good foam cannot be formed due to a splash-like state when foaming. In this case, it is possible to suppress the decrease in resin viscosity by increasing the conversion rate. Further, by using the urethane group-containing polyol described above, the effect of improving so-called meandering (engaging of the foam tip) is also recognized.

As the polyol used in the present invention in combination with the above-mentioned urethane group-containing polyol, all known polyols can be used. However, a hydroxyl value of sucrose / glycerin / tolylenediamine mixture added with propylene oxide is 4
A 50 mg KOH / g polyol is preferred. Other than that, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol,
Dipropylene glycol, tripropylene glycol,
Addition polymerization of alkylene oxide to trimethylolpropane, pentaerythritol, sorbitol, polyhydric alcohols such as sucrose, aromatic amines such as tolylenediamine, and aliphatic amines such as ethylenediamine and triethanolamine, either alone or as a mixture. There are polyether polyols having a hydroxyl value of 350-800 mgKOH / g and the like.

As the catalyst used in the present invention, all known catalysts can be used, and examples thereof include triethylamine, tripropylamine, N-methylmorpholine, N-ethylmorpholine, triethylenediamine and tetramethylhexamethylenediamine. An amine-based urethane-forming catalyst can be used. These catalysts can be used alone or as a mixture, and the amount thereof is appropriately 0.0001 to 20.0 parts with respect to 100 parts of the compound having active hydrogen. As the foam stabilizer, a conventionally known organosilicon-based surfactant is used. For example, L-54 manufactured by Nippon Unicar Co., Ltd.
20, L-5421, SH-193 manufactured by Toray Dow Corning Silicone, F-32 manufactured by Shin-Etsu Chemical Co., Ltd.
7, F-345, F-305, etc. are suitable. The amount of these foam stabilizers used is 0.1 to 10 parts per 100 parts of the total of the compound having active hydrogen and the organic polyisocyanate. Other flame retardants, plasticizers, stabilizers, colorants and the like can be added as required.

To carry out the present invention, a predetermined amount of a polyol, a catalyst, a foaming agent, and a foam stabilizer is mixed to prepare a resin liquid. A polyurethane foam stock solution obtained by rapidly mixing a resin solution and an organic polyisocyanate at a constant ratio is poured into a cavity or a mold. At this time, the liquid ratio of the organic polyisocyanate and the resin liquid is adjusted so that the equivalent ratio (NCO / OH) of the organic polyisocyanate and the active hydrogen of the resin liquid is 0.7: 1 to 5: 1. .

[0014]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples unless it exceeds the gist. . The raw materials used in the examples and comparative examples are described below. Isocyanate-1. : Mitsui Toatsu Chemical Co., Ltd. Cosmonate T-80 2,4-tolylene diisocyanate 80% by weight and 2,6
20% by weight mixture of tolylene diisocyanate. NCO%: 48.3 Isocyanate-2. : Mitsui Toatsu Chemicals, Cosmonate M-200, crude diphenylmethane diisocyanate, NCO%: 31.3

Propylene glycol: manufactured by Mitsui Toatsu Chemicals, Inc., hydroxyl value: 1476 mg KOH / g. Ethylene glycol: manufactured by Mitsui Toatsu Chemicals, Inc., hydroxyl value: 1808 mg KOH / g. Polyol-A: A polyether polyol obtained by adding propylene oxide to a mixture of sucrose / glycerin / tolylenediamine. Hydroxyl value: 450 mgKOH /
g. Polyol-B: 100 parts by weight of diethylene glycol dehydrated and dried with Molecular Sieve 400A for 1 day and 70.0 parts by weight of isocyanate-1 at 80 ° C.
The mixture was added with stirring, taking care not to exceed the limit. After all the additions were completed, the reaction was carried out at 80 ° C. under a nitrogen atmosphere for 1.5 hours. After cooling, it was discharged and designated as polyol-B.
Hydroxyl value: 350 mg KOH / g Polyol-C: Monoethylene glycol 100 dehydrated and dried with Molecular Sieve 400A for one day.
80 parts by weight of isocyanate-1,67.0 parts by weight
The mixture was added with stirring, taking care not to exceed the temperature of ° C. After all the additions were completed, the reaction was carried out at 80 ° C. under a nitrogen atmosphere for 1.5 hours. After cooling, it was discharged and designated as Polyol-C. Hydroxyl value: 820mgKOH / g

Foam stabilizer: L-5 manufactured by Nippon Unicar Co., Ltd.
420 Catalyst: Activator Chemical Co., Ltd. Min
ico TMHD foaming agent (CFC) R-11: trichlorofluoromethane R-123: 2,2-dichloro-1, 1, 1
-Trifluoroethane R-141b: 1,1-dichloro-1-fluoroethane Examples and comparative examples are shown in Table 1 and Table 2 together.

[0017]

[Table 1]

[0018]

[Table 2]

Examples 1 to 12 and Comparative Examples 1 to 6 A predetermined amount of a resin solution (20 ° C.) having the composition shown in Table 1 was prepared, and a predetermined amount of organic polyisocyanate (20 ° C.) was added thereto, followed by high speed for 4 seconds. After mixing, the mixture was immediately poured into the open mold of an aluminum vertical panel (360 × 380 × 35 mm) which had been preheated to 45 ° C. and foamed. After injection, the mold was removed 10 minutes to obtain a rigid urethane foam. After foaming, the thermal conductivity of the foam left to stand in a thermostatic chamber at 23 ° C. and a humidity of 65% for 24 hours was measured. Thermal conductivity is EKO Auto λ (made by Hidekosha)
Was measured. Sample size (200 x 200 x 20.

From the contrast between the examples and comparative examples shown in Table 1, the rigid polyurethane foams of the examples using the specific urethane group-containing polyol raw material according to the present invention have lower thermal conductivity than those of the comparative examples. It can be seen that the low temperature dimensional stability is excellent.

[0021]

As described above, according to the present invention, by using a specific urethane group-containing polyol raw material, the thermal conductivity is low even when R-11 as a foaming agent is replaced with a CFC substitute, and the low temperature A polyurethane foam having good dimensional stability is provided. Therefore, the present invention is suitable for strengthening the regulations for the use of CFCs due to the destruction of the ozone layer, and its industrial utility value is great.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical indication location C08L 75:04 (72) Inventor Shumi Hayashi 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. In-house (72) Inventor Yuji Uchida 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd.

Claims (4)

[Claims] 1. An organic polyisocyanate, a polyol,
In a rigid polyurethane foam produced from a foaming agent, a catalyst, a foam stabilizer and other auxiliaries, an alkylene glycol having a hydroxyl value of 800 to 2000, in which one part of the polyol has at least two or more hydroxyl groups, is used. It is obtained by reacting an organic polyisocyanate containing at least two or more isocyanate groups of ½ equivalent and / or less, and the amount thereof is 1 to 70 per 100 parts by weight of polyol.
A rigid polyurethane foam, characterized by using hydrochlorofluorocarbon as a blowing agent, in parts by weight. 2. An alkylene glycol having at least two or more hydroxyl groups and a hydroxyl value of 800 to 2000 is selected from one or more kinds selected from monoethylene glycol, monopropylene glycol, diethylene glycol, dipropylene glycol, glycerin and diglycerin. The rigid polyurethane foam according to claim 1, which is a mixture. 3. The hard according to claim 1, wherein the organic polyisocyanate having at least two isocyanate groups is 2,4-tolylene diisocyanate and / or 2,6-tolylene diisocyanate. Polyurethane foam. 4. A hydrofluorocarbon as a foaming agent is 1,1-dichloro-1-fluoroethane, 2,2-
The rigid polyurethane foam according to claim 1, which is dichloro-1,1,1-trifluoroethane, and is used in an amount of 10 to 70 parts by weight based on 100 parts by weight of the polyol.