JPH0367090B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing lightweight asphalt foam.

Joint materials used in houses, vehicles, civil engineering work, etc. are required to have the basic properties of water repellency and slow restoring power.As one of these joint materials, we are considering the water repellency of asphalt and the restoring power of foam. The material used has been known for a long time (hereinafter referred to as asphalt foam). but,
Conventional asphalt foams were manufactured by impregnating open-celled urethane foam with molten asphalt or asphalt emulsion, which caused the problem of so-called uneven impregnation, making it impossible to obtain uniform quality. In addition, since the asphalt attached to the cell walls of the foam due to impregnation is relatively easy to detach, repeated compression causes the impregnated asphalt to be gradually lost and the quality to deteriorate.

Therefore, the applicant has proposed a method for manufacturing asphalt foam that does not cause uneven quality or deterioration of quality, as shown on the left. That is, this production method involves adding a urethane prepolymer obtained by reacting a polyether polyol with an ethylene oxide content of 15% or more with an organic isocyanate to an aqueous emulsion of asphalt, water, silicone oil, etc. as necessary. It is foamed by adding and mixing foam stabilizers, fillers, and other additives. Since the asphalt foam produced in this manner has asphalt itself constituting the foam base, the quality does not deteriorate due to separation of the asphalt from the base. Also,
Because the asphalt emulsion is uniformly separated by the foaming action and mechanical stirring, there is no unevenness in quality. In this way, the problems of quality unevenness and quality deterioration in conventional asphalt foams have been solved by the asphalt foam manufacturing method previously proposed by the applicant.

Incidentally, asphalt foam is heavy because it contains asphalt, which has a high specific gravity. Therefore, transportation costs are high, and large-sized ones used for civil engineering work have problems with workability during construction.

The present invention was made as a result of intensive research aimed at reducing the weight of asphalt foam, and the applicant discovered a method for manufacturing lightweight asphalt foam by improving the method for manufacturing asphalt foam previously proposed. be.

That is, the present invention uses a urethane prepolymer obtained by reacting an asphalt aqueous emulsion with a polyether polyol having an ethylene oxide content of 15% or more and an organic isocyanate, polystyrene resin pellets containing a blowing agent, and, if necessary, a polystyrene resin pellet containing a blowing agent. This is a method for producing lightweight asphalt foam, which is characterized by adding and mixing water, a foam stabilizer, a filler, and other additives and foaming the foam.

As mentioned above, the present invention differs from the asphalt foam production method previously proposed by the applicant in that it uses polystyrene resin pellets containing a blowing agent, and as will be described later, this requirement makes it possible to produce asphalt foam. This achieved weight reduction. As the polystyrene resin pellets containing a blowing agent, commercially available granular resins containing a blowing agent such as propane, butane or petroleum ether can be used. A preferred example is "foamed styrene beads" from Dow Chemical Japan.
Examples include those available under the trade name.

The aqueous emulsion of asphalt used in the present invention can be obtained by known emulsion techniques, such as mechanically stirring and dispersing asphalt in water using a cationic or anionic surfactant. In this case, the asphalt may be natural asphalt, straight asphalt obtained as a residue from distillation of asphalt-based crude oil, or blown asphalt obtained by oxidative polymerization by introducing heated air into this asphalt. Further, the ratio of asphalt to water is preferably 0.3 to 2.0 parts by weight per 1 part by weight of asphalt. If the amount of water is less than 0.3 parts by weight, it is difficult to obtain a uniform emulsion, and if it exceeds 2.0 parts by weight, the amount of asphalt is so small that an asphalt foam with desired properties cannot be obtained.

The urethane prepolymer used in the present invention not only serves as a blowing agent, but also remains in the asphalt foam and functions as a connecting material or filler. The reason why a reaction product of a polyether polyol having an ethylene oxide content of 15% or more and an organic isocyanate is used as the urethane prepolymer is as follows.
That is, since the asphalt component is added as an aqueous emulsion as described above, the urethane prepolymer in this case is required to have good affinity with water, and the above-mentioned urethane prepolymer satisfies this requirement. This urethane prepolymer can be added in a wide range of 5 to 250 parts by weight per 100 parts by weight of the asphalt emulsion. In other words, when the amount of urethane prepolymer added is reduced, a so-called asphalt foam of asphalt richness is obtained. On the other hand, if the amount of urethane prepolymer added is increased, an asphalt foam with a rich foam structure can be obtained. In any case, an asphalt foam that fully functions as a joint material can be obtained. In particular, by using Asphalt Rich's asphalt foam in a molded form, it is possible to achieve further improvements in workability and joint effectiveness. Of course, other asphalt foams can be used not only in the casting type but also in the mold type.

In the present invention, when the above-mentioned aqueous asphalt emulsion, urethane prepolymer, and polystyrene resin pellets containing the above-mentioned blowing agent are mixed and stirred, the urethane prepolymer causes a polymerization reaction to grow polyurethane linkages, and at the same time, The free isocyanate groups react as described below to generate carbon dioxide gas, resulting in a foaming effect.

-N=C=O+H ₂ O→NH ₂ +CO ₂ On the other hand, the polystyrene resin pellet containing the foaming agent foams to form expanded polystyrene due to the reaction heat of the polymerization reaction and foaming reaction of the urethane prepolymer. In this way, an asphalt foam with foamed polystyrene pieces embedded inside is obtained. Note that if the polystyrene resin pellets are incompletely foamed due to insufficient reaction heat, they may be forcibly heated using an oven or the like. Also,
When the water contained in the aqueous asphalt emulsion is insufficient for the foaming effect of the urethane prepolymer, a necessary amount of water may be appropriately added and mixed. Furthermore, by adding silicone oil as a foam stabilizer, more uniform bubbles can be formed. It goes without saying that additives such as fillers such as aluminum hydroxide, clay, and calcium carbonate, pigments, rust preventives, and slight inhibitors can also be added as desired.

According to the manufacturing method of the present invention, as is well known, an asphalt foam in which styrene foam pieces with extremely low specific gravity are embedded is obtained, and the weight of the asphalt foam as a whole can be reduced by the contribution of the styrene foam pieces. I can do it. Furthermore, since styrofoam has relatively high hardness, according to the present invention, it is possible to simultaneously improve the hardness of the asphalt foam, and to obtain an asphalt foam that is particularly suitable as a joint material for concrete and a base material for construction. I can do it.

Since the present invention utilizes the asphalt foam manufacturing method previously proposed by the applicant, it goes without saying that uniform quality due to uniform dispersion of asphalt particles and excellent durability without quality deterioration can be achieved. stomach.

Examples of the present invention will be described below.

Example 1 50% aqueous emulsion of blown asphalt
Ethylene oxide content 60 per 100 parts by weight
Polystyrene resin pellets containing 60 parts by weight of urethane prepolymer with 9.5% free isocyanate obtained by heating and mixing % polyether polyol (molecular weight 3000, 3 tube capacity) and tolylene diisocyanate (manufactured by Dow Chemical Japan) and a blowing agent. When 25 parts by weight of "expanded styrene beads" were mixed and stirred to foam, an asphalt foam with a density of 0.29 was obtained.

Comparative Example When foaming was carried out in Example 1 except that the polystyrene resin pellets were removed, an asphalt foam having a density of 0.4 was obtained.

As mentioned above, in the example, 27% compared to the comparative example
We were able to achieve a significant weight reduction.

As detailed above, according to the present invention, remarkable effects such as being able to produce an asphalt foam with uniform quality and reduced weight can be obtained.

Claims (1)

[Claims] 1. For an aqueous emulsion of asphalt,
A lightweight asphalt characterized by foaming a urethane prepolymer obtained by reacting a polyether polyol with an ethylene oxide content of 15% or more with an organic isocyanate and polystyrene resin pellets containing a foaming agent. Method of manufacturing foam. 2. The method for producing lightweight asphalt foam according to claim 1, characterized in that forced heating is performed to promote foaming of the polystyrene resin pellets containing the foaming agent. 3. The method for producing lightweight asphalt foam according to claim 1 or 2, characterized in that water is added in an amount necessary for the foaming action of the urethane prepolymer. 4. A method for producing lightweight asphalt foam according to claim 1, 2, or 3, characterized in that necessary additives such as fillers, foam stabilizers, and pigments are added and mixed together. .