Heat-seal failure prevention method and article
View Patent ↗A co-injected molded multi-layer article has inner and outer layers, an interior layer contained within the inner and outer layers and a surface portion to which a closure or other component may be heat-sealed. The article is molded by co-injecting the inner, outer and interior layer materials into a mold cavity of a mold. The interior layer material is caused to flow along a steam line offset from the zero velocity gradient of the combined material flow and biased toward a material flow for forming an outer wall of the multi-layer article. The resultant molded multi-layer article contains an interior layer located in a heat sealable region that avoids a breach or failure during a heat seal operation to seal an opening of the molded article.
1. A method of molding a multi-layer article from a first polymeric material and a second polymeric material, the method comprising:
injecting the first polymeric material into a mold cavity configured to form a resulting multi-layer article having an open end opposed to a closed end and a flange disposed at the open end with the flange including a heat sealable zone of the resulting multi-layer article;
injecting the second polymeric material into the mold cavity to form an inner layer and an outer layer of the resulting multi-layer article; and
positioning the first polymeric material in the heat sealable zone of the resulting multi-layer article to maintain integrity of a resulting interior layer of the resulting multi-layer article during a heat sealing operation by co-injecting the first polymeric material along a flow streamline offset from a zero velocity gradient of a combined flow of the first and second polymeric materials.
2. A method as defined in claim 1 , wherein the first polymeric material and the second polymeric material are different materials.
3. A method as defined in claim 1 , wherein the first polymeric material forms an interior barrier layer or an interior scavenger layer in the resulting multi-layer article.
4. A method as defined in claim 1 , wherein the first polymeric material is co-injected along a flow streamline biased toward a resulting outer wall surface of the resulting multi-layer article.
5. A method as defined in claim 1 , wherein the first polymeric material is co-injected along a flow streamline biased toward a resulting inner wall surface of the resulting multi-layer article.
6. A method as defined in claim 1 , further comprising heat-sealing a component to a surface portion of the heat sealable zone.
7. The method of claim 4 , further comprising maintaining co-injection of the first polymeric material along a flow streamline offset from the zero velocity gradient of the combined flow and biased toward the resulting outer wall surface of the resulting multi-layer article throughout co-injection of the first polymeric material into the mold cavity.
8. The method of claim 7 , wherein first polymeric material is co-injected along a flow streamline having a velocity greater than an average velocity of the combined flow throughout co-injection of the first polymeric material into the mold cavity.
9. The method of claim 5 , further comprising maintaining co-injection of the first polymeric material along a flow streamline offset from the zero velocity gradient of the combined flow and biased toward the resulting inner wall surface of the resulting multi-layer article throughout co-injection of the first polymeric material into the mold cavity.
10. The method of claim 9 , wherein first polymeric material is co-injected along a flow streamline having a velocity greater than an average velocity of the combined flow throughout co-injection of the first polymeric material into the mold cavity.
11. The method of claim 1 , wherein the inner layer or the outer layer of the resulting multi-layer article has a sealing surface, and wherein the method further comprises co-injecting the first polymeric material along a flow streamline offset from a zero velocity gradient of a combined flow of the first and second polymeric materials and biased away from the layer of the resulting multi-layer article having the sealing surface.
12. The method of claim 11 , further comprising maintaining co-injection of the first polymeric material along a flow streamline offset from the zero velocity gradient and biased away from the layer of the resulting multi-layer article having the sealing surface throughout co-injection of the first polymeric material into the mold cavity.
13. The method of claim 11 , wherein first polymeric material is co-injected along a flow streamline having a velocity greater than an average velocity of the combined flow throughout co-injection of the first polymeric material into the mold cavity.
14. The method of claim 1 , wherein the heat sealable zone of the resulting article includes a sealable surface substantially parallel to an orientation of a layer of first polymeric material in the heat sealable zone of the resulting article.