FIELD OF THE INVENTION

The present invention relates in general to composites, and more specifically, to polyisocyanurate composites made with a thermally decomposable acid which acts as a catalyst inhibitor to increase pot life.

BACKGROUND OF THE INVENTION

The use of fiber reinforced composite materials containing a thermosetting polymer matrix and reinforcing fibers has been growing in the aerospace, automotive, and construction industries, where light weight, excellent mechanical properties, and corrosion resistance are desired. Typical thermosetting polymers are unsaturated polyester, epoxy, and polyurethane. Although composite materials deliver highly differentiated performance, they struggle to achieve long term UV and weathering resistance. They all contain aromatic monomer units that absorb UV light, causing degradation of the polymer matrix. EP 2 777 915 discloses a two-component aliphatic polyurethane system which exhibits good weathering properties in addition to excellent mechanical properties. A thermosetting resin system with long pot life, high thermal stability, and excellent UV and weathering resistance is still lacking.

Polyisocyanurates are known in the art for having good thermal stability and chemical resistance. In particular, polyisocyanurates based on aliphatic isocyanates have very good weathering resistance. However, aliphatic polyisocyanurates have only found practical use as crosslinking agents for polyurethane systems in paint and adhesive applications. U.S. Pat. No. 7,202,302 describes a thermosetting composite system based on polyisocyanurates including a polyol component, an optional chain extender, and an isocyanate. These polyisocyanurate systems have extended initiation times of less than 30 minutes at room temperature and can be snap cured by heat.

U.S. Pat. Pub. 2019/255788 provides a thermoset technology based on aliphatic polyisocyanurates, which are unaffected by UV radiation and have excellent weathering resistance. The liquid resin has improved pot life at room temperature and shows rapid curing at elevated temperatures. These composites are said to be particularly suitable for outdoor applications. This technology has been applied to established composite manufacturing processes such as pultrusion. However, there are still some technical challenges to be addressed, for example, short pot life of <four hours at ambient temperature. It highly desired to improve the formulation pot life while maintaining the resin reactivity.

In WO 2019/197638, a new amine adduct catalyst was developed to address the pot life limitation while still maintaining high reactivity, however, this approach has limited effectiveness with certain polyisocyanates.

Therefore, a need continues to exist in the art for a way to extend the pot life of a polyisocyanurate formulation at room temperature while maintaining curing efficiency.

SUMMARY OF THE INVENTION

Accordingly, the present invention reduces or eliminates problems inherent in the art by providing a new approach to address the pot life limitation of liquid formulations used for preparing polyisocyanurate composites. The present invention extends the pot life of such formulations at room temperature while maintaining the same curing efficiency by introducing a small amount of a thermally decomposable acid. The acid is an organic acid or an acid precursor that is soluble in polyisocyanates and acts as an inhibitor for trimerization catalysts at room temperature. The addition of small amounts of the acid can significantly extend the formulation pot life without affecting resin reactivity. Polyisocyanurates produced in the inventive processes may be used as the matrix material for pultrusion processes to produce a wide variety of products, including but not limited to, wind turbine blades, yacht shells, window frames, door frames, ladder frames, telegraph pole cross arms, tent poles, solar cell frames, solar cell backsheets, radomes, highway guard rails, floor boards, pipes, telegraph poles, auto trunks, luggage holders, engine covers, golf clubs, tennis poles, badminton poles, bicycle frames, surfboards, and snowboards.

These and other advantages and benefits of the present invention will be apparent from the Detailed Description of the Invention herein below.

