Leak-Free Stopper Having Low Breakloose and Sustaining Forces

Abstract

A thermoplastic elastomer stopper that meets the desired material properties of a stopper for a syringe assembly is disclosed. The compression set of the thermoplastic elastomer stopper of the present disclosure is ≤50% when measured at 25% compression for 22 hrs at 70 degree C. The hardness of the thermoplastic elastomer stopper of the present disclosure is 40-70 Shore A. The viscosity of a thermoplastic elastomer stopper of the present disclosure is ≥70 Pa·s at 1,000 s−1 shear rate, ≥12.0 Pa·s at 10,000 s−1 shear rate, and ≥3.0 Pa·s at 50,000 s−1 shear rate when measured using a capillary rheometer at 205 degree C. (Die: Roundhole 20 mm length/1 mm diameter/180 degree inlet, Piston: d=15 mm, and melting time=7 min). The present non-lubricated stopper exhibits the required functional performance of a lubricated stopper.

What is claimed is: 
     
         1 . A syringe assembly, comprising:
 a syringe barrel having a proximal end, a distal end, and a sidewall extending therebetween and defining a chamber having an interior, the syringe barrel formed of a first material;   a stopper slidably disposed within the interior of the chamber of the syringe barrel, the stopper sized relative to the interior of the chamber of the syringe barrel to provide sealing engagement with the sidewall of the syringe barrel, the stopper formed of a second material different than the first material, wherein the second material does not contain more than 4% of the first material; and   a plunger rod having a first end engageable with a portion of the stopper.   
     
     
         2 . The syringe assembly of  claim 1 , wherein the second material does not contain more than 1.5% of the first material. 
     
     
         3 . The syringe assembly of  claim 1 , wherein the second material does not contain more than 1% of the first material. 
     
     
         4 . The syringe assembly of  claim 1 , wherein the second material comprises a thermoplastic elastomer having a viscosity at 205 degrees C. is ≥70 Pa·s at 1,000 s −1  shear rate, ≥12.0 Pa·s at 10,000 s −1  shear rate, and ≥3.0 Pa·s at 50,000 s −1  shear rate. 
     
     
         5 . The syringe assembly of  claim 4 , wherein the thermoplastic elastomer comprises at least an olefin block copolymer. 
     
     
         6 . The syringe assembly of  claim 1 , wherein the stopper comprises a non-lubricated thermoplastic elastomer and wherein the thermoplastic elastomer comprises a composition having a hard polymer phase having a high melt temperature >170 degrees C. and an elastomeric phase. 
     
     
         7 . A stopper for a syringe assembly, the stopper comprising:
 a lower portion;   a roof portion, the roof portion having a first thickness; and   a shear element disposed adjacent the roof portion, the shear element having a second thickness, wherein the second thickness of the shear element is less than 52% and greater than 36% of the first thickness of the roof portion.   
     
     
         8 . The stopper of  claim 7 , wherein the second thickness of the shear element is approximately 44% of the first thickness of the roof portion. 
     
     
         9 . The stopper of  claim 7 , further comprising a catch can element having a receiving volume. 
     
     
         10 . The stopper of  claim 7 , wherein the stopper is formed from a thermoplastic elastomer having a viscosity at 205 degrees C. which is ≥70 Pa·s at 1,000 s −1  shear rate, ≥12.0 Pa·s at 10,000 s −1  shear rate, and ≥3.0 Pa·s at 50,000 s −1  shear rate. 
     
     
         11 . The stopper of  claim 10 , wherein the thermoplastic elastomer comprises at least an olefin block copolymer. 
     
     
         12 . The stopper of  claim 7 , wherein the shear element is configured to enable molding of the stopper in an open gate system. 
     
     
         13 . The stopper of  claim 12 , wherein the shear element has a thickness of 0.012 to 0.023 inches. 
     
     
         14 . A stopper for a syringe assembly, the stopper comprising:
 a lower portion;   a roof portion, the roof portion having a first thickness;   a shear element disposed adjacent the roof portion, the shear element having a second thickness, wherein the second thickness of the shear element is less than 52% and greater than 36% of the first thickness of the roof portion; and   a catch can element having a receiving volume.   
     
     
         15 . The stopper of  claim 14 , wherein the stopper is formed from a thermoplastic elastomer having a viscosity at 205 degrees C. which is ≥70 Pa·s at 1,000 s −1  shear rate, ≥12.0 Pa·s at 10,000 s −1  shear rate, and ≥3.0 Pa·s at 50,000 s −1  shear rate. 
     
     
         16 . The stopper of  claim 15 , wherein the thermoplastic elastomer comprises at least an olefin block copolymer. 
     
     
         17 . The stopper of  claim 14 , wherein the catch can element has a receiving volume that is at least equal to a volume of residual material remaining from a previous shot during a gate molding operation.