JPH044200B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a construction method that uses a composition that foams and hardens upon contact with a liquid such as water or steam to impart buoyancy to an underwater structure and float it to the surface.

[B] Industrial application fields Construction, marine, river, salvage, etc. [B] Conventional technology 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 it by contacting it with excess water is also known, for example, as a urethane-based grafting agent.

[C] Problems to be Solved by the Invention In all of these known methods, prepolymers having a relatively low residual isocyanate concentration are usually used.

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.

In sea operations where there are extreme changes in weather conditions,
Slow reaction times mean that you can't predict what situations you'll encounter while working, which means you'll always be performing dangerous tasks.

The reason for the slow reaction rate 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 promote the reaction using a catalyst such as a tertiary amine, but in this case as well, reduction in water diffusion due to film formation is unavoidable.

On the other hand, when used as a urethane-based grout agent, rapid curing is required, so it is best to use a hydrophilic polyhydroxyl compound and a prepolymer to make the polyurethane hydrophilic and promote water diffusion. It's normal.

However, in this case, the foamed product is not only interconnected and does not have sufficient strength, but also contains water in the bubbles, making it impossible to obtain buoyancy.

It is also 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.

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.

The brittleness of the coating means that the foam is susceptible to destruction, resulting in connections between the internal air bubbles and loss of the buoyancy that was so hard to gain.

[d] Purpose of the present invention The present invention improves these conventional problems, and
To provide a method for levitating an underwater structure, which can easily and reliably levitate an underwater structure by using a material that reacts extremely smoothly with a large amount of water and has closed cells with sufficient strength. With the goal.

[E] Means for solving the problem (1) Description of the stock solution used for injection The stock solution used in the method of the present invention is a mixture of organic polyisocyanate, or organic polyisocyanate and polyhydroxyl compound in the presence of 2-pyrrolidone. The invention was based on the discovery that the prepolymer reacts extremely smoothly with a large amount of 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 water. found.

All hitherto known catalysts for the reaction of isocyanates with water have been amine-based, especially tertiary amine-based or organometallic compounds.

However, 2-pyrrolidone used in the present invention is an intramolecular dehydrate of ω-amino acid, and cannot be considered to have a catalytic effect in common sense.

However, when an experiment was actually conducted using 2-pyrrolidone, the following results were obtained.

That is, when 2 to 5 parts by weight of 2-pyrrolidone was added to 100 parts by weight of polymethylene polyphenyl polyisocyanate, the reaction with water was significantly accelerated.

It was found that this mixture foamed immediately on contact with water and solidified within a few minutes.

When the amount of 2-pyrrolidone was less than 5 parts by weight, the foamed solid remained brittle for several hours, but after that it became a strong foam.

When the amount of 2-pyrrolidone was 5 parts by weight or more, sufficient toughness was exhibited immediately after foaming and solidification.

What should be noted at this time is that this system does not use any conventionally known catalysts.

Such an effect may be caused by other hydrophilic solvents such as dimethylformamide, 2-pyrrolidone,
N-methylpyrrolidone is also promising.

However, this cannot be expected with ε-caprolactam, which has a structural similarity to the above.

[F] Example When the source solution with the composition shown in the upper row was injected into water, it had the characteristics shown in the lower row.

(1) Crude MDI 100 copies 1 part silicone surfactant 2-pyrrolidone 10 parts Reaction speed: cream 15 seconds Curing 1 minute Foaming ratio: 20x Properties: Not brittle, strong enough.

(2) Crude MDI 100 copies 1 part silicone surfactant 2-pyrrolidone 20 parts Reaction speed: cream 5 seconds Curing 30 seconds Foaming ratio: 40x Properties: Not brittle, strong enough.

(3) Crude MDI 100 copies 1 part silicone surfactant 2-pyrrolidone 1 part Reaction speed: cream several tens of minutes Hardening several tens of minutes Foaming ratio 1 to 2 times Properties: Fragile and easily disintegrates.

(4) Crude MDI 100 copies 1 part silicone surfactant 2-pyrrolidone 100 parts Reaction speed: cream 2 seconds Curing 10 seconds Foaming ratio: 100x Properties: Insufficient strength.

(5) 100 parts of terminal isocyanate prepolymer 1 part silicone surfactant 2-pyrrolidone 20 parts Reaction speed: cream 15 seconds Curing 50 seconds Foaming ratio: 30x Properties: Very strong and not brittle.

[Floating method] A source liquid with the following composition is transported to the sea by ship, and pumped into a structure on the seabed, such as a sunken ship or an oil pipe that is no longer needed.

Crude MDI 100 parts by weight SH-193 (surfactant) 1 part by weight 2-pyrrolidone 20 parts by weight Source liquid pumped from a ship at sea foams in water within a short time and gives buoyancy to the structure. .

Not only does it foam within a short time, but the foam itself has toughness, so the bubbles do not collapse.

In addition, in order to prevent the structure from suddenly floating up and turning over, it is recommended to attach weights to the structure using wires or the like.

[G] Effects Since the levitation method of the present invention is as explained above, the following effects can be expected.

(1) Because the reaction speed is fast, even if the work is at sea where the weather changes drastically, the work can be completed safely within a short time when the weather can be predicted.

(2) Since the cells of the foam that are foamed in a short period of time have toughness, they will not collapse for a long time.

Therefore, reliable buoyancy can be obtained, and the levitation can be carried out as planned with adjusted speed and time.

Claims (1)

[Claims] 1. A stock solution consisting of an organic polyisocyanate and/or a terminal isocyanate prepolymer obtained from an organic polyisocyanate and a polyhydroxyl compound, and 2-pyrrolidone is injected into a structure in water, and foamed and cured in water. A method for levitating an underwater structure, which is carried out by applying buoyancy to the underwater structure.