Low Boron Borosilicate Glass for Chemical Tempering
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Solution Overview
Problem
Borosilicate glasses used in pharmaceutical applications lack sufficient susceptibility to chemical tempering while maintaining good hydrolytic and chemical resistance, and they often have issues with alkali release, which affects the stability and efficacy of pharmaceutical compositions.
Innovation Solution
A borosilicate glass composition with a low boron content, optimized cooling rates during production, and specific ratios of SiO2, Al2O3, Na2O, and B2O3 to achieve high diffusivity, compressive stress, and penetration depth, allowing for effective chemical tempering and reduced alkali release.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If borosilicate glass is used for pharmaceutical packaging, then good hydrolytic resistance and chemical stability are achieved, but susceptibility to chemical tempering is insufficient
Solution Approach 1:
The patent modifies the glass composition parameters by reducing B2O3 content to 3-10 mol% (lower than conventional borosilicate glasses) and optimizing Na2O content to 6-13 mol%, along with specific Al2O3 content of 3-8 mol%. These parameter changes create a glass composition that maintains hydrolytic resistance while improving susceptibility to chemical tempering, allowing effective ion exchange treatment.
Solution Approach 2:
The patent creates a composite glass system that combines low boron content borosilicate composition with optimized alkali and alumina content. This composite approach allows the glass to exhibit both the desired chemical resistance of borosilicate glasses and the improved tempering susceptibility typically associated with other glass types.
2Reliability
If conventional borosilicate glass composition is used, then chemical resistance is maintained, but alkali release exceeds acceptable thresholds
Solution Approach 1:
The patent optimizes the Na2O content to a specific range of 6-13 mol% and controls the B2O3/Na2O ratio to be less than 1.20. This parameter optimization reduces alkali release to below 0.10 mg Na2Oeq/g glass after 24 hours at 37°C, while maintaining chemical resistance through the optimized glass composition structure.
Solution Approach 2:
The patent creates different compositional zones within the glass structure by optimizing the distribution of Na2O, B2O3, and Al2O3. The specific ratio control creates a glass network where alkali ions are more tightly bound in the matrix, reducing their release into pharmaceutical contents while maintaining the overall chemical resistance of the glass.
3Reliability
If B2O3 content is increased to improve chemical resistance, then hydrolytic stability is enhanced, but diffusivity for chemical tempering decreases
Solution Approach 1:
The patent identifies and implements the critical B2O3/Na2O ratio parameter, controlling it to be less than 1.20. By reducing B2O3 content to 3-10 mol% and optimizing Na2O to 6-13 mol%, the patent achieves a balance where the glass maintains hydrolytic stability (HGA1 class) while achieving sufficient diffusivity (D ≥ 6 μm²/h) for effective chemical tempering.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The borosilicate glass exhibits improved chemical tempering properties, enhanced hydrolytic resistance, and reduced alkali release, leading to increased strength and stability suitable for pharmaceutical primary packaging.
Implementation Method 1
The ion exchange process works in such a way that, at the glass surface, smaller alkali metal ions, such as for instance sodium and/or lithium ions, are exchanged for larger alkali metal ions, such as potassium ions
Implementation Method 2
Diffusivity D can be calculated from DoL and chemical tempering time t according to the following formula: DoL = 1.4 * sqrt( 4 * D * t)
Data Source
AI summary
The invention relates to a chemically temperable borosilicate glass article having a low boron content and a corresponding Na2O content. The articles have good diffusivities and hydrolytical resistance values. When chemically tempered, the borosilicate glass article exhibits a compressive stress CS > 400 MPa and a penetration depth DoL > 20 µm. The invention also relates to pharmaceutical primary packaging comprising the borosilicate glass article. The borosilicate glass articles and the borosilicate glasses can be tempered much better than comparable borosilicate glasses of the state of the art.