JPH0826300B2 - Sealant contamination prevention method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvement of tackiness of a surface such as a joint during curing of a sealing material.

Specifically, in the present invention, a solution of the polyisocyanate polyurethane prepolymer is applied to the surface of the uncured sealing material after application to accelerate the curing of the sealing material surface portion and improve the surface tackiness. By doing so, it is possible to prevent dust and the like from adhering to the surface of the sealing material, and to prevent contamination of the sealing material. In general, one-component and two-component modified silicone and polyurethane sealing materials, when cured, remain tacky on their surfaces for days or months (hereinafter referred to as "after-tack"). Modified silicone is defined in JIS A5758.

For this reason, for example, when a sealing material is applied to joints of a building, there is a problem that dust and dirt adhere to the joint surface and contaminate the joint surface during aftertack, and improvement is strongly desired.

Various attempts have been made to improve after-tack. For example, by increasing the amount of inorganic flies in the sealing base material, or by increasing the amount of thixotropic agent colloidal silica or polyurea powder, or by using functional groups such as isocyanate groups and silicate groups in the resin component. A certain degree of improvement can be made by means of increasing the crosslinking density. However, with these means, the viscosity of the liquid is high and the workability is poor, and the hardness of the sealing material after curing is high, which causes a decrease in elongation at break and an increase in modulus, which is an important performance of the sealing material. It is not practical because it has drawbacks such as poor followability.

In the method of the present invention, a polyurethane prepolymer containing two or more isocyanate groups at the molecular end of a sealing material such as polyurethane or modified silicone filled in voids such as joints is preferably on the surface of the sealing material before complete curing, preferably immediately after filling. The inert organic solvent solution of is applied by spraying or brush. By this method, it is possible to accelerate the curing of the surface of the sealing material and remove the surface tackiness, so that it is possible to prevent the sealing material from being contaminated.

The polyurethane sealing material used, for example, an excess amount of polyisocyanate such as TD1, MD1 and the like, an isocyanate group-terminated polyurethane prepolymer obtained by the reaction of polyols such as polyether polyol, and the like, and containing flies, There is a one-component polyurethane sealing material that cures due to moisture in the air during use.

In addition, a two-component polyurethane sealing material in which a main agent containing an isocyanate group-terminated urethane prepolymer as a main component as described above and a curing agent containing a polyol and a fly, etc., are mixed and reacted and cured at the time of use Used. In addition, one-part type and two-part type are also commercially available as modified silicone-based sealing materials having an alkoxysilane group at the molecular end.

The contamination prevention method of the present invention can be applied to general sealing materials, but is particularly effective for one-component or two-component modified silicone sealing materials and one-component or two-component polyurethane sealing materials.

The polyurethane prepolymer having an isocyanate group at the molecular end used in the present invention will be described.

Examples of the raw material isocyanate include toluene diisocyanate, diphenylmethane diisocyanate, aromatic isocyanate such as polyphenylmethane polyisocyanate and hexamethylene diisocyanate, isophorone diisocyanate, xylene diisocyanate, and aliphatic isocyanate such as nuclear hydrogenated xylene diisocyanate. When the latter isocyanate is used as a raw material, the resulting coating film has good weather resistance, discoloration resistance, non-staining property around the joint, and the like, and is particularly preferable.

As the polyol component to be combined with the polyisocyanate, polyols used for general polyurethane resins such as polyoxypropylene polyol, polyester polyol, polyacrylic polyol, and monomolecular polyol such as ethylene glycol can be used.

As the solvent, an inert solvent containing no active hydrogen compound such as ethyl acetate, methyl ethyl ketone, toluene, xylene, hexane or dimethyl ether is used.

In the present invention, additives such as a plasticizer, a filler, a pigment matting agent, a thickener, a stabilizer, and a catalyst can be blended, if necessary.

Although the role of the action of the polyisocyanate urethane prepolymer used in the present invention is unclear, for example, in the case of a one-component polyurethane sealant, when it is applied to the surface of an uncured sealant, a part of the prepolymer is a surface layer of the sealant. As it penetrates into the surface, the isocyanate groups react relatively quickly with the water in the air to form a highly cross-linked resin of polyurethane and polyurea on the surface, which solidifies and solidifies to accelerate the curing of the sealing material surface and prevent after-tack. To do. On the other hand, polyisocyanate prepolymer, which forms a film with a relatively high molecular weight and elasticity, has a good affinity for the surface of the sealing material, and by forming a uniform and flexible film on the surface, prevention of long-term contamination and improvement of weather resistance Considered to be effective.

When the polyurethane prepolymer is composed only of low molecular weight, the coating film is hard and has no elasticity, so that it cannot follow the expansion and contraction of the sealing material and cracks are generated, which is not preferable.

When this isocyanate prepolymer is coated on the surface of the sealing material, it does not penetrate deep into the inside of the sealing material, so the modulus and elasticity of the sealing material are not deteriorated. Does not adversely affect the physical properties.

As a construction example of the present invention, a joint part is filled with the one-component or two-component type sealing material, and before or after removing the masking tape around the joint after the spatula-holding finish, a solution of the polyisocyanate urethane prepolymer. With a brush, an air spray, an airless spray, an aerosol spray, or the like to coat the joint surface evenly and thinly.

By carrying out this pollution prevention method, the surface of the sealing material is hardened faster and the after-tack period can be greatly shortened compared to the case without treatment, so a sealing material with non-contamination and improved weather resistance can be obtained. Was obtained.

Next, the present invention will be described with reference to examples, but the present invention is not limited thereto.

[Synthesis Example-1] In a 1 L four-necked flask substituted with nitrogen gas, polyethertriol having a molecular weight of 400 in which propylene oxide was added to glycerin 33.6 (g), isophorone diisocyanate 55.9 (g), dibutyltin dilaurate 0.45
(G) and 810.0 (g) of dehydrated ethyl acetate were charged and reacted at 75 ° C. for 3 hours to obtain a urethane prepolymer solution [A] having an isocyanate concentration of 1.12 (%).

[Synthesis Example-2] Molecular weight obtained by adding ε-caprolactone to trimethylolpropane in a 1 L 4-neck flask substituted with nitrogen gas.
500 polycaprolactone triol 34.8 (g), hydrogenated MD1 54.7 (g), stannous octylate 0.45 (g), dehydrated ethyl acetate 810.0 (g) were charged and reacted at 75 ° C for 3 hours to obtain isocyanate concentration. A urethane prepolymer solution [B] of 0.93 (%) was obtained.

[Synthesis Example-3] In a 1 L 4-necked flask substituted with nitrogen gas, a molecular weight of 500 obtained by adding ε-caprolactone to ethylene glycol was added.
Polycaprolactone diol 17.6 (g), trimethylolpropane 9.4 (g), isophorone diisocyanate 6
2.5 (g), dibutyltin dilaurate 0.45 (g) and dehydrated ethyl acetate 810.0 (g) were charged and reacted at 75 ° C. for 3 hours to obtain a urethane prepolymer solution [C] having an isocyanate concentration of 1.25 (%). .

[Example-1] A commercially available one-component type polyurethane sealing material and a one-component type low modulus modified silicone sealing material were filled in the joints, and immediately the prepolymer solution [A] synthesized previously was prepared.
[B] was uniformly sprayed with a commercially available atomizer. These samples were evaluated for tack-free at 20 ° C. and 60% RH (drying time to the touch), after-tack after 3 days (adhesiveness after curing), and contamination status when exposed outdoors for 3 months. The results are shown in Table-1.

[Comparative Example-1] Filling the joint with the sealing material used in Example-1,
It was allowed to cure. These samples were evaluated by conducting the same tests as in Example-1. The results are shown in Table-1.

[Example-2] A commercially available two-component low-modulus polyurethane sealing material and a two-component modified silicone sealing material were filled in the joints, and immediately the prepolymer solution [A] synthesized previously was used.
[C] was uniformly sprayed with a commercially available atomizer. These samples were evaluated by conducting the same tests as in Example-1. The results are shown in Table-2.

[Comparative Example-2] The joint was filled with the sealing material used in Example-2,
It was allowed to cure. These samples were evaluated by conducting the same tests as in Example-1. The results are shown in Table-2.

As is clear from the above results, the spraying of the urethane prepolymer solution shows a very excellent effect in shortening tack-free and improving after-tack. Therefore, when a sealing material is used in exposed areas such as tile joints and siding joints, this method is extremely effective for preventing contamination.

[Note: In Tables 1 and 2, the one-component polyurethane sealing material is Auton 101A manufactured by Auto Chemical Co., Ltd .; the one-component modified silicone sealing material is Posseal LM manufactured by Cemedine Industry Co., Ltd. Yes; the two-component polyurethane sealing material is Millionate NS manufactured by Hodogaya Kenzai Co., Ltd.
The two-component silicone sealing material is Hamatite Super II manufactured by Yokohama Rubber Co., Ltd. ]

Claims (3)

[Claims] 1. A method for preventing contamination of a sealing material, which comprises applying a solution of a polyisocyanate urethane prepolymer to the surface of the uncured sealing material. 2. The method for preventing contamination of a sealing material according to claim 1, wherein the sealing material is a polyurethane type or a modified silicone type. 3. The prepolymer is a solution of a polyurethane prepolymer containing two or more aliphatic, araliphatic, or alicyclic molecular terminal isocyanate groups in an organic solvent. The method for preventing contamination of the sealing material according to claim 1.