Crystallization-free glass frit compositions and frits made therefrom for microreactor devices

Abstract

The invention is directed to a glass composition that can be used to make glass frits suitable for use in the manufacturing of microreactors. The glass compositions, after final sintering to produce a finished microreactor, have a surface crystalline layer of 30 μm or less, or are completely amorphous throughout. Generally, the borosilicate glasses of the invention have a composition of B2O3=12-22 mol %; SiO2=68-80 mol % and additional components selected from the group consisting of either (a) Al2O3=3-8 mol % and Li2O=1-8 mol %, or (b) K2O=0-2 mol % and Na2O=0-2 mol %, except that both K2O and Na2O cannot both equal zero at the same time. One borosilicate glass has a composition, in mole percent (mol %) of B2O3=18-22 mol %, SiO2=75-80 mol %, K2O=0-2 mol %, and Na2O=0-2 mol %, except that both K2O and Na2O cannot both equal zero at the same time.

Description

CLAIM OF PRIORITY [0001] This application claims the benefit of priority under 35 U.S.C. § 119 of European Patent Application Serial No. 05292534.4 filed on Nov. 30, 2005. FIELD OF THE INVENTION [0002] The invention is directed to crystallization-free glass frits that are suitable for the manufacturing of glass microreactor using micro-molding technology and to the glass compositions used to make such frits; and in particular to glass frits that exhibit resistance to thermal shock and have excellent chemical durability. BACKGROUND OF THE INVENTION [0003] As a result of economic forces, environmental considerations, waste disposal regulations and other factors, activities in the fields of thermal and chemical process engineering have gravitated toward the use of microreactors for research and development, including modeling studies and chemical reactions. In addition, microreactors are finding application in pharmaceutical and biological research, development and analysis. A microrea...

AI Technical Summary

Benefits of technology

[0062] The glass compositions according to the invention impart an advantage over previously known borosilicate glass frits by providing new families of borosilicate frits that have similar properties of thermal expansion, chemical stability and viscosity as Pyrex® 7740 or 7761 frit glasses, and additionally have a very strong crystallization resistance not found in glass frits made from 7740 glass. The new frits according to the invention did not crystallize during the two-firing steps as used in conducting the experiments reported herein in spite of the presence of impurities that may be present in the paste. The glass frit compositions according to the invention can form hermetic sintered channels on glass substrates in accordance with the process described in U.S. Pat. No. 5,853,446 (3). The microreactor channels formed in the frits are vitreous, translucent, chemically durable and resistant to thermal shock. The frits can also be matched to different substrate materials, for example a 1737 or Eagle2000 substrate, over a large temperature range (300° C.), and the sign and magnitude of mismatch can be tailored by the thermal cycle.

Problems solved by technology

While the simple design illustrated in FIG. 1 is satisfactory for some reactions, for others a more complex design is required.

As a result the design of the reactor can become quite complicated; which in turn means that the construction of the reactor itself becomes complicated and expensive if etching techniques are used to construct parts of the microreactor.

In addition, while materials such as metals, silicon and certain polymers can be used to fabricate microreactors, these materials are not well suited for chemical reactions at high temperature and / or that use corrosive reactants.

As mentioned in U.S. 2004 / 0152580 A1, the problem with PYREX® glass frits is that they undergo devitrification (that is, crystals of different materials are formed) during sintering at temperatures in the range of 700-800° C. However, there is a lowering of mechanical strength due to both the formation of crystals with a high coefficient of thermal expansion and the volume change that is associated with the phase transformation of cristobalite crystals at approximately 200° C. This can lead to frit cracking on cooling after sintering.

The addition of alumina causes the sintering ability of the frit to decrease and reduces the fluidity of the frit.

Images