Method of manufacturing headerless produce bags with increased adhesion
During the manufacturing process the exterior surface of one or both of the sheets of plastic film which form the bags is treated with low temperature corona discharge plasma to raise the level of surface charge magnitude to at least 43 Dyne to increase the adhesion force between the bags. A recess is formed in each of the bags to further increase the adhesion. The increased adhesion causes the mouth of one bag to automatically open as the adjacent bag is removed from the rack. The recess is formed at the same time openings are created in the bags to accept the support rods of a dispensing rack. The bags can have simple edge sides or side gussets and may be provided in a package including a pouch which receives and supports the lower portions of the bags.
1. A method useful for manufacturing a headerless plastic bag from sheets of thin plastic film, comprising:
providing a first continuous web sheet aligned in facing relation to a second continuos web sheet at a forming station comprising a first platen to form aligned first and second sheets;
applying and then removing pressure and heat at a section of the aligned first and second sheets using the platen to form heat sealed sides and a mouth of a headerless plastic bag;
advancing the headerless plastic bag formed in the section of the aligned first and second sheets from the forming station to a plasma treatment station configured to directly apply low temperature corona discharge plasma treatment to only the first sheet;
treating the first sheet at the plasma treatment station under zero added pressure with low temperature corona discharge plasma to increase the surface charge magnitude of the first sheet to a surface energy of at least 43 Dyne wherein the surface energy is sufficient to cause the headerless plastic bag to adhere to an adjacent second plastic bag with a force sufficient to automatically open the mouth of the headerless plastic bag upon removal of the second bag from therefrom;
advancing the treated headerless plastic bag formed in the section of the aligned first and second sheets to a cutting station;
cutting the first and second aligned sheets to separate the headerless plastic bag from the first sheet and the second sheet;
advancing the cut headerless plastic bag to a stacking station comprising a second platen;
stacking the cut headerless plastic bag at the stacking station onto a second plastic bag; and
forming concurrently both a first pair of mated recesses in the first sheet and the second sheet of a first plastic bag, the first pair of recesses configured to cause the first sheet to releasably mechanically adhere to the second sheet, and a second pair of mated recesses in the second plastic bag, using the second platen, a recess of the first pair of mated recesses mated with a recess of the second pair of mated recesses, wherein the adherence between the second plastic bag and the cut headerless plastic bag caused by the plasma treatment, combined with the adherence between the first sheet and the second sheet of the cut headerless plastic bag caused by the mated first pair of recesses, and the adherence between the cut headerless plastic bag and the second plastic bag caused by the first pair of recesses in the first plastic bag mated with the second pair of recesses in the second plastic bag, together cause the cut headerless plastic bag to automatically open upon separation of the second plastic bag from the cut headerless plastic bag.
2. The method of claim 1 , comprising treating the second plastic bag with low temperature corona discharge plasma to increase the surface charge magnitude thereof.
3. The method of claim 2 , wherein the surface charge magnitude of the second plastic bag is at least 43 Dyne.
4. The method of claim 1 , determining a number of recesses to be created in the plastic bag based upon the size of the plastic bag.
5. The method of claim 4 , wherein the step of determining the number of recesses comprises the step of increasing the number of recesses to be created as the size of the bag increases.
6. The method of claim 1 , further comprising forming an opening in the headerless bag, the opening configured to receive a support rod, concurrently with the forming the first pair of recesses.
7. The method of claim 1 , wherein the first pair of recesses and the second pair of recesses are substantially round.
8. The method of claim 1 , wherein the cut headerless plastic bag adheres to the second bag with sufficient force to automatically open the mouth of the second bag as the cut headerless plastic bag is moved away from the second bag.
9. A method useful for manufacturing a headerless plastic bag from sheets of thin plastic film, comprising:
providing a first continuous web sheet aligned in facing relation to a second continuos web sheet at a forming station comprising a first platen to form aligned first and second sheets;
applying and then removing pressure and heat at a section of the aligned first and second sheets using the platen to form heat sealed sides and a mouth of a headerless plastic bag
advancing the headerless plastic bag formed in the section of the aligned first and second sheets from the forming station to a plasma treatment station configured to directly apply low temperature corona discharge plasma treatment to only the first sheet;
treating the first sheet at the plasma treatment station with low temperature corona discharge plasma to increase the surface charge magnitude of the first sheet to a surface energy of at least 43 Dyne wherein the surface energy is sufficient to cause the headerless plastic bag to adhere to an adjacent second plastic bag with a force sufficient to automatically open the mouth of the headerless plastic bag upon removal of the second bag from therefrom;
advancing the treated headerless plastic bag formed in the section of the aligned first and second sheets to a cutting station;
cutting the first and second aligned sheets to separate the headerless plastic bag from the first sheet and the second sheet;
advancing the cut headerless plastic bag to a stacking station comprising a second platen;
stacking the cut headerless plastic bag at the stacking station onto a second plastic bag; and
forming concurrently both a first pair of mated recesses in the first sheet and the second sheet of the first bag, the first pair of recesses configured to cause the first sheet to releasably mechanically adhere to the second sheet, and a second pair of mated recesses in the second plastic bag, using the second platen, a recess of the first pair of mated recesses mated with a recess of the second pair of mated recesses, wherein the adherence between the second plastic bag and the cut headerless plastic bag caused by the plasma treatment, combined with the adherence between the first sheet and the second sheet of the cut headerless plastic bag caused by the mated first pair of recesses, and the adherence between the cut headerless plastic bag and the second plastic bag caused by the first pair of recesses in a first plastic bag mated with the second pair of recesses in the second plastic bag, together cause the cut headerless plastic bag to automatically open upon separation of the second plastic bag from the cut headerless plastic bag.
10. The method of claim 9 , comprising determining a number of recesses to be created based upon the size of the bags.
11. The method of claim 10 , the determining the number of recesses further comprising increasing the number of recesses as the size of the bags increases.
12. The method of claim 9 , comprising forming an opening in each of the bags.
13. The method of claim 12 , the concurrently forming the first pair of recesses and the second pair of recesses and the forming an opening occurring at the same time.
14. The method of claim 9 , wherein the recesses created in each of the bags is substantially round in shape.