Pre-filled Syringe Gasket Mold Surface Roughness Control
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Solution Overview
Problem
Conventional gaskets laminated with fluororesin films for pre-filled syringes exhibit poor air-tightness and liquid-tightness, particularly when used with glass or resin syringes, and existing solutions like increasing annular rib diameter or using skived PTFE films do not effectively address these issues, leading to leakage and sealing problems.
Innovation Solution
A method for producing a gasket with an inactive film using a mold with a mirror-finished surface having an arithmetic mean roughness of less than 0.02 µm, which ensures excellent sealing performance by preventing the transfer of fine irregular marks from the mold to the gasket, even when using PTFE films with higher surface roughness than 0.05 µm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a fluororesin film is laminated on the gasket to ensure drug stability, then chemical compatibility is improved, but air-tightness and liquid-tightness deteriorate
Solution Approach 1:
The invention changes the surface roughness parameter of the mold from conventional values to less than 0.02 µm (mirror finish), which fundamentally alters how the fluororesin film surface is formed. This parameter change enables the laminated gasket to achieve both drug stability and excellent air-tightness/liquid-tightness by preventing liquid penetration while maintaining chemical compatibility.
2Reliability
If the annular rib diameter is increased to improve sealing width, then sealing performance is improved, but setting difficulty and crease formation increase
Solution Approach 1:
Instead of changing the geometric parameter of the annular rib diameter, the invention changes the surface roughness parameter of the mold to less than 0.02 µm. This alternative parameter change achieves improved sealing performance without the negative effects of increased setting difficulty and crease formation.
3Reliability
If the annular rib diameter is increased to increase compressibility, then sealing performance is improved, but sliding resistance increases
Solution Approach 1:
The invention changes the mold surface roughness parameter to less than 0.02 µm, which improves sealing performance through enhanced film formation rather than increasing compressibility. This approach achieves better sealing without increasing sliding resistance.
4Ease of manufacture
If a conventional mold is used for laminated gasket production, then manufacturing is simpler, but surface quality and sealing performance deteriorate
Solution Approach 1:
The invention specifies a mold surface roughness parameter of less than 0.02 µm (mirror finish), which is a significant refinement from conventional molds. This parameter change produces gaskets with superior surface quality and sealing performance, preventing liquid leakage while maintaining ease of manufacture through the defined molding process.
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 method results in gaskets with enhanced air-tightness and liquid-tightness, preventing leakage and ensuring the stability and quality of drugs in pre-filled syringes, as demonstrated by the absence of leakage in tests under pressure and steam sterilization.
Implementation Method 1
at least a surface of the mold which forms a seal sliding surface of an annular protrusion of the gasket is mirror finished to have an arithmetic mean roughness Ra of less than 0.02 µm
Implementation Method 2
formed by vacuum press molding into a molded sheet for a laminated gasket
Implementation Method 3
molding at 155°C to 200°C using a mold, which is preheated before the gasket is molded
Data Source
Figure 1(A)~1(C)
AI summary
The present invention aims to provide a gasket for a pre-filled syringe which has excellent air-tightness and liquid-tightness and a mold for forming the gasket. The present invention relate to a mold for a gasket laminated with an inactive film for a pre-filled syringe, wherein at least a surface of the mold which forms a seal sliding surface of an annular protrusion of the gasket is mirror finished to have an arithmetic mean roughness Ra of less than 0.03 µm.