JPH0521130B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a cured product in water. [B] Industrial fields of use Used in construction, marine, river, salvage, etc. [B] Prior Art It is known that organic polyisocyanate compounds react with water to release carbon dioxide gas and form urea bonds. A method of making a terminal isocyanate prepolymer from an organic polyisocyanate and a polyhydroxyl compound and curing it by reacting with water or water vapor can be used, for example, with moisture-curable urethane paints,
It is known as a moisture-curable urethane adhesive. Furthermore, a method of preparing a hydrophilic terminal isocyanate prepolymer from an organic polyisocyanate and a hydrophilic polyhydroxyl compound, and foaming and curing this by contacting it with excess water is also known, for example, as a urethane grouting agent. [C] Problems to be Solved by the Present Invention In all of these known methods, prepolymers having a relatively low residual isocyanate concentration are usually used. The residual isocyanate concentration here refers to the weight percent of isocyanate groups in the total weight, calculated according to the purity test of JIS K 1556 "Tolylene diisocyanate test method". For example, the residual isocyanate concentration of moisture-curable urethane paints is about 10% or less, and in the case of grouting agents, it is about 5% or less. These moisture-curable urethane prepolymers have the problem of slow reaction rates. The reason for this is that the amount of residual isocyanate in the prepolymer is small. Furthermore, moisture-curable urethane prepolymers have the problem of forming a film on their surfaces upon contact with water or steam. As a result, the penetration of water that should react with isocyanate is inhibited, and the diffusion of water is restricted. It is also possible to accelerate the reaction using a catalyst, for example a tertiary amine, but in this case as well, reduction in water diffusion due to film formation is unavoidable. Usually, when used as a urethane-based grouting agent, a hydrophilic polyhydroxyl compound and a terminal isocyanate prepolymer are used because rapid curing is required, but the resulting polyurethane exhibits hydrophilic properties and therefore does not allow water to diffuse. This is relatively easy, which is unfavorable in terms of water-stopping performance. In addition, since the obtained polyurethane hardens while containing excess water, shrinkage occurs when the surrounding water is removed and the polyurethane dries, which poses a problem in terms of long-term water-stopping performance. On the other hand, organic polyisocyanates, such as polymethylene polyphenyl polyisocyanate, are hydrophobic and do not react rapidly with water. For example, even if you mix it with a large excess of water and stir it vigorously, if you leave it still, it will immediately separate into two layers.
Almost no carbon dioxide gas is generated for at least several minutes or several tens of minutes. Of course, in this case as well, the reaction will occur gradually over several hours and will eventually foam and harden, but the film formed at that time will be extremely brittle. On the other hand, it is known that the presence of a hydrophilic solvent facilitates this reaction. For example, dimethyl formamide is added to 100 parts of polymethylene polyphenyl polyisocyanate.
If you add 20 parts or more and leave it in the air or drop it into water, it will gradually react and form a tough film on the surface. However, in this case as well, the reaction is extremely slow, and even if the surface layer is hardened, the internal hardening tends to be delayed. Although the reaction is accelerated when a catalyst such as a tertiary amine is used, it is inevitable that the internal reaction will be delayed due to hardening of the surface layer. [d] Purpose of the present invention The present invention has been made to improve the problems of the conventional art. An object of the present invention is to provide a method for producing a foamed cured product having the following properties. [E] Means for Solving the Problems The present invention uses a large amount of organic polyisocyanate and/or a prepolymer of an organic polyisocyanate and a polyhydroxyl compound with a residual isocyanate concentration of 10% or more in the presence of 2-pyrrolidone. This was achieved by discovering the fact that it reacts extremely smoothly with water and foams and hardens. By using 2-pyrrolidone as a hydrophilic solvent, not only can the above problems be overcome, but also 2-pyrrolidone itself has a strong catalytic effect on the reaction between organic isocyanate and a large amount of water. It also became clear that All hitherto known catalysts for the reaction of isocyanates with water have been amine-based, especially tertiary amine-based or organometallic compounds. However, the 2-pyrrolidone used in the present invention is
〓-It is an intramolecular dehydrate of an amino acid, and in common sense, it cannot be considered to have a catalytic effect. However, when experiments were actually conducted using 2-pyrrolidone, the following effects were obtained. That is, 2 to 2-pyrrolidone is added to 100 parts by weight of polymethylene polyphenyl polyisocyanate.
When 5 parts by weight was added, the reaction with water in water was significantly accelerated. It has been found that this mixture foams immediately upon contact with water in water and solidifies within a few minutes. When the amount of 2-pyrrolidone was around 5 parts by weight, the foamed solid material still showed brittleness for about a few hours, but after that it became a tough foamed product. When the amount of 2-pyrrolidone was 5 to 80 parts by weight, sufficient toughness was exhibited immediately after foaming and solidification. If the amount of 2-pyrrolidone exceeds 80 parts by weight, foaming will occur, but the strength will be insufficient and it will not be practical. What should be noted here is that this system does not use any conventionally known urethanization catalysts. Such an effect cannot be seen with other hydrophilic solvents such as dimethylformamide, N-methylpyrrolidone, which has structural similarity to 2-pyrrolidone, and ⓓ-caprolactam. In the present invention, the residual isocyanate concentration of the organic polyisocyanate is 10% or more. If the concentration is lower than 10%, the curing time will be slow and the expansion ratio will also be low, which is not preferable for the purposes of the present invention. [F] Example (Example 1) Crude MDI (residual isocyanate concentration 30%,
(manufactured by Mitsui Toatsu) 100 parts by weight Silicone surfactant (dimethylpolysiloxane, manufactured by Toray Dow Corning) 1 part by weight 2-pyrrolidone 10 parts by weight These were mixed to prepare a stock solution. This stock solution was poured into 10 times the volume of water at room temperature to foam and harden. The test results are shown in Table 1. In this test, the following items are measured and evaluated. (1) Cream time is the time from when the stock solution is put into water until the stock solution foams and begins to swell. (2) Cream time is the time from when the stock solution is put into water until the stock solution completes foaming and swelling. Rise time (3) Expansion ratio of the obtained foam (4) Comprehensive evaluation of the foam state by strength test and visual observation according to the compressive strength test of JIS K 7220 "Compression test method for rigid foam plastics" (Example 2) ) Crude MDI (residual isocyanate concentration 30%,
(manufactured by Mitsui Toatsu) 100 parts by weight Silicone surfactant (dimethylpolysiloxane, manufactured by Toray Dow Corning) 1 part by weight 2-pyrrolidone 20 parts by weight These were mixed and operated in the same manner as in Example 1 to obtain a foam. Ta. Table 1 shows the results of the cream time, rise time, foaming ratio, and foaming state of the foam. (Example 3) Crude MDI (residual isocyanate concentration 30%,
(manufactured by Mitsui Toatsu) 100 parts by weight Polyalkylene glycol (MW3000, manufactured by Sanyo Kasei) 6 parts by weight These were heated to 80 degrees Celsius in a reaction vessel, reacted for 3 hours, cooled to room temperature, and converted into terminal isocyanate prepolymer (residual isocyanate). concentration of 28%). The above terminal isocyanate prepolymer (residual isocyanate concentration 28%) 100 parts by weight Silicone surfactant (dimethylpolysiloxane, manufactured by Toray Dow Corning) 1 part by weight 2-pyrrolidone 20 parts by weight These were mixed and the same procedure as in Example 1 was carried out. A foam was obtained by operation. Table 1 shows the results of the cream time, rise time, foaming ratio, and foaming state of the foam. (Example 4) Crude MDI (residual isocyanate concentration 30%,
Made by Mitsui Toatsu)
100 parts by weight of polyalkylene glycol (MW3000, manufactured by Sanyo Chemical Co., Ltd.) 140 parts by weight These were loaded and operated in the same manner as in Example 3 to convert the terminal isocyanate prepolymer (residual isocyanate concentration
10%). The above terminal isocyanate prepolymer (residual isocyanate concentration 10%) 100 parts by weight Silicone surfactant (dimethylpolysiloxane, manufactured by Toray Dow Corning) 1 part by weight 2-pyrrolidone 20 parts by weight These were mixed and the same procedure as in Example 1 was carried out. A foam was obtained by operation. Table 1 shows the results of the cream time, rise time, foaming ratio, and foaming state of the foam. (Comparative example 1) Crude MDI (residual isocyanate concentration 30%,
(manufactured by Mitsui Toatsu) 100 parts by weight Silicone surfactant (dimethylpolysiloxane, manufactured by Toray Dow Corning) 1 part by weight 2-pyrrolidone 1 part by weight These were mixed and operated in the same manner as in Example 1 to obtain a foam. Ta. Table 2 shows the results of cream time, rise time, foaming ratio, and foaming state of the foam. (Comparative example 2) Crude MDI (residual isocyanate concentration 30%,
(manufactured by Mitsui Toatsu) 100 parts by weight Silicone surfactant (dimethylpolysiloxane, manufactured by Torre Dow Corning) 1 part by weight 2-pyrrolidone 100 parts by weight These were mixed and operated in the same manner as in Example 1 to obtain a foam. Ta. Table 2 shows the results of cream time, rise time, foaming ratio, and foaming state of the foam.

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[Table] [G] Effects of the present invention Since the present invention is as described above, the following effects can be expected. (1) Since the reaction rate in water can be freely adjusted by changing the amount of 2-pyrrolidone added, it can be used under optimal conditions depending on the application. (2) The resulting foamed cured product does not contain excess water and cures while forming closed cells, so it has sufficient strength for practical use. (3) According to the manufacturing method described in the claims, a material without brittleness can be obtained, and a cured foamed product can be obtained that has approximately the same toughness as ordinary rigid polyurethane foam.

Claims (1)

[Claims] 1. In a method for producing a foamed cured product, based on 100 parts by weight of a terminal isocyanate prepolymer obtained from an organic polyisocyanate and/or an organic polyisocyanate and a polyhydroxyl compound, the residual isocyanate concentration is 10% or more. A method for producing a cured foam product, which comprises mixing 2 to 80 parts by weight of 2-pyrrolidone and injecting the mixture into water.