JPS62146954A - Thixotropic polyurethane composition - Google Patents

Abstract

PURPOSE:To provide the titled compsn. having excellent resistance to heat, weather and cold and adhesion to substrates such as primed metal, plastics, wood, etc., consisting of a polyurethane resin, colloidal silica and a branched polyoxyalkylene silicone polymer. CONSTITUTION:100pts.wt. polyurethane prepolymer (A) having terminal isocyanate groups (one-pack type) or two-pack polyurethane resin (A) consisting of said one-pack component and OH group-terminated polyol having an average MW of 1,000-5,000 as other component is blended with 0.1-50pts.wt. colloidal silica (B) (e.g., aerosil), 0.1-20pts.wt. branched polyoxyalkylenesilicone polymer (C) of the formula (wherein n, a, b, c are each an integer and 4>=n>=1; R is CH3, C2H5, COCH3, etc.) and optionally, a plasticizer, a solvent, an inorg. filler, a curing accelerator, a tackifier, a curing catalyst, etc. (D).

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a thixotropic polyurethane composition, and more particularly, the present invention relates to a thixotropic polyurethane composition, which has excellent heat resistance, weather resistance, and cold resistance, and easily and strongly adheres to primer-treated substrates. The present invention relates to a thixotropic polyurethane composition.

[Prior art]

Polyurethane has excellent properties such as rubber elasticity, weather resistance, and abrasion resistance, and is therefore widely used in elastomers, coating materials for paper and cloth, paints, sealants, adhesives, and the like.

Depending on the application, it is often desirable for polyurethane to have thixotropy. For example, when polyurethane is applied to vertical surfaces as a paint or sealant, it can be applied with a brush or spatula. Because of the long processing time, the finish becomes beautiful.

Furthermore, when applied as an adhesive or coating material onto porous paper or cloth, there is less oozing and the application process becomes easier.

Incidentally, as one of the methods of imparting thixotropy to polyurethane, a method of adding an anti-sagging agent such as colloidal silica or bentonite has been proposed.

However, as the amount of anti-sagging agents such as colloidal silica is increased, the thixotropy is improved and the sagging phenomenon can be suppressed, but the apparent viscosity of polyurethane increases significantly,
There was a drawback that workability such as mixing and construction deteriorated.

Furthermore, in terms of physical properties after curing, hardness and modulus increase, and extensibility and adhesiveness decrease, making it impossible to satisfy the various properties required for sealants, adhesives, coating materials, etc. .

Therefore, various methods of imparting thixotropy without impairing other properties have been proposed as described below.

(a) A method of blending an anti-sag agent such as a sulfoxide with polyurethane (Japanese Patent Publication No. 27418/1983).

(b) A method of blending colloidal silica and polyoxyalkylene silicone polymer (pendant type) with polyurethane (JP-A-59-120650).

(c) A method of blending colloidal silica and a urea derivative with polyurethane (Japanese Patent Application Laid-open No. 120750/1983).

However, even with these methods, sufficient thixotropy is still not imparted, and there are still drawbacks such as changes in thixotropy during storage, apparent viscosity becoming extremely high, and deterioration of workability during mixing and construction. Not resolved.

[Object of the Invention] The present invention has been made in order to eliminate the above-mentioned conventional drawbacks, and it is an object of the present invention to provide a method for imparting thixotropy without impairing other properties.

[Structure of the invention]

The thixotropic polyurethane composition of the present invention that achieves the above object comprises 100 parts by weight of a polyurethane resin, 0.1 to 50 parts by weight of colloidal silica, and 0.1 to 20 parts by weight of a branched polyoxyalkylene silicone polymer. It is characterized by consisting of.

The polyurethane resin (polyurethane prepolymer) used in the present invention is a polyurethane prepolymer with terminal isocyanate groups in the case of a corrugated type (for example, cured by moisture in the atmosphere after application). As the polymer, for example, a polyether polyol such as polyoxypropylene diol or triol, or a polyether polyol having a hydroxyl group at the end and having an average molecular weight of 1
It is manufactured by reacting a polyol of about 000 to 10,000 with polyisocyanates.

Examples of polyisocyanates include tolylene diisocyanate and 4,4'-diphenylmethane diisocyanate.

When the polyurethane is two-component, one component is usually a prepolymer with terminal isocyanate groups similar to the above-mentioned one-component polyurethane, and the other component is a polyol with terminal hydroxyl groups having an average molecular weight of about 1,000 to 5,000. It's normal.

Polyols include polyoxypropylene diol,
Polyoxypropylene triol and the like are used.

In such two-component polyurethanes, the prepolymer component having terminal isocyanate groups and the polyol component are mixed immediately before use.

These polyurethane resins are usually in liquid or solution form, and examples of solvents include esters such as ethyl acetate, ketones such as methyl ethyl ketone, and aromatic hydrocarbons such as toluene.

The colloidal silica used in the present invention is finely powdered silica obtained by a firing method, and is not particularly limited, and commercially available products can be used as appropriate, such as Aerosil (Nippon Aerosil Co., Ltd.) etc.

Furthermore, a commercially available branched polyoxyalkylene silicone polymer used in the present invention can be used, and has a composition represented by the following general formula.

In the formula, n, a, b, and C are integers, provided that 4≧n
≧1, and R represents -CH3, C4H11, C0CHs, etc.

A preferred example is Silicon L-520 (Nippon Unicar Co., Ltd.).

In addition to the above-mentioned components, the polyurethane composition of the present invention also contains plasticizers such as dioctyl phthalate and dibutyl phthalate, solvents such as xylene and toluene, inorganic fillers such as calcium carbonate and talc, hardening accelerators, and adhesives. A property imparting agent, a curing catalyst, a coloring agent, etc. can be appropriately blended.

In the present invention, the colloidal silica is usually blended in an amount of 0.1 to 50 parts by weight, preferably 1 to 15 parts by weight, per 100 parts by weight of the polyurethane resin.

The branched polyoxyalkylene silicone polymer is generally 0.1 to 20 parts by weight, preferably 0.1 to 20 parts by weight.
It is blended in an amount of 3 to 10 parts by weight.

If the amount of colloidal silica is less than 0.1 part by weight, thixotropy and prevention of sagging will be insufficient, and if it exceeds 50 parts by weight, storage stability and workability will deteriorate, which is not preferred.

Furthermore, if the amount of branched silicone polymer added is less than 0.1 part by weight, the desired thixotropy will not be obtained and the anti-sag effect will be insufficient, and if it exceeds 20 parts by weight, storage stability will be affected. Sexuality becomes worse.

The thixotropic polyurethane resin composition of the present invention can be manufactured by adding and mixing a branched polyoxyalkylene silicone polymer after uniformly dispersing colloidal silica in a urethane prepolymer, and manufacturing the urethane prepolymer. When doing this, colloidal silica is dispersed in polyol in advance, polyisocyanate is added and reacted in a conventional manner, and a branched polyoxyalkylene silicone polymer is added and mixed to the resulting prepolymer, or a two-component urethane is used. In some cases, there is a method of adding a branched polyoxyalkylene silicone polymer as a third component when attempting to obtain a cured product by mixing a prepolymer already containing colloidal silica and a curing agent. The present invention can adopt any of these methods; in short, the colloidal silica and the polyoxyalkylene silicone polymer can be added before the urethane prepolymer reacts with the active hydrogen compound and hardens. .

〔Effect of the invention〕

As described above, according to the present invention, by dispersing colloidal silica and branched polyoxyalkylene silicone polymer in a polyurethane resin, hydrogen bonding between silanol groups of colloidal silica is further promoted and continuous A structure is formed.

This structure is easily destroyed by a weak external force, causing a temporary decrease in viscosity, but when the external force is removed, a continuous structure is restored.

Therefore, the composition of the present invention has excellent heat resistance, weather resistance, and cold resistance, and strongly adheres to base materials such as primer-treated metal, concrete, mortar, wood, and plastic. Can be used as an adhesive.

Examples of the present invention will be described below.

〔Example〕

Example 1 Production of urethane prepolymer A urethane prepolymer was produced using the raw materials shown in Table 1 below.

That is, polyoxypropylene triol is added to the reaction tank,
Polyoxypropylene glycol and dioctyl phthalate (DOP) as a plasticizer were added, the pressure was reduced to 100°C, water was removed, and the mixture was cooled to 80°C under nitrogen gas.

Then, 4,4'-diphenylmethane diisocyanate (MDI) was added under stirring until the isocyanate residues were 2.
The reaction was carried out until it reached 54%, and a urethane prepolymer was obtained.

Example 2 Production of thixotropic polyurethane composition The urethane prepolymer obtained in Example 1 and other raw materials as shown in Table 2 below were charged into a container equipped with a mixer for high viscosity, and the mixture was heated at room temperature. The mixture was stirred and kneaded under reduced pressure to produce a polyurethane composition of the present invention.

Notes: 1) Colloidal silica, manufactured by Nippon Aerosil Co., Ltd. 2), 3) Branched polyoxyalkylene silicone polymer, manufactured by Nippon Unicar Co., Ltd. The obtained polyurethane composition was evaluated for thixotropy.

The evaluation is 0 to 1 according to the slump test according to JTS A37581979 architectural sealant slump test method.
Up to 1 mm was considered thixotropic, and 1 mm or more was considered non-thixotropic.

The results are shown in Tables 3 and 4 below.

Note: 1), 2), and 3) are from Table 3, which is the same as Table 2. Polyurethane compositions (Example 1 and 2)
It is clear that the composition is superior in terms of thixotropy compared to the composition containing no polyoxyalkylene silicone polymer (Comparative Example 1).

Notes = 1) and 2) are from Table 4, which is the same as Table 2. Compositions containing colloidal silica and branched polyoxyalkylene silicone polymer have thixotropy, but without colloidal silica, It is clear that the composition containing only the branched polyoxyalkylene silicone polymer does not have thixotropy.

Claims (1)

[Claims] 100 parts by weight of polyurethane resin and 0 parts of colloidal silica
．． A thixotropic polyurethane composition comprising 1 to 50 parts by weight of a branched polyoxyalkylene silicone polymer and 0.1 to 20 parts by weight.