Snap zipper and bag with the same

Abstract: A snap zipper (11), in which at least a portion to be fused is mainly composed of polybutylene terephthalate (PBT) resin or polyester type elastomer, having a bending modulus of elasticity of 10,000 kg/cm 2 or below.

Description: This invention relates to a snap zipper and a bag with snap zipper, which can be utilized in the fields of foods, medical products and grocery. Bags with zipper are used in many fields such as those of foods, medical products and grocery. In the bag with snap zipper, a strip-like snap zipper comprising a male and a female member is provided on the bag in a sealing portion thereof. Heretofore, various methods of producing bags with snap zipper have been proposed. Among the proposed methods, there are (1) one, in which a cylindrical film with a male and a female portion of a snap zipper is extrusion formed as a one-piece molding by using extrusion dies, and (2) one, in which a tape with a snap zipper is produced and is thermally fused to a base film for forming a bag body. In the former method (1), the bag with snap zipper, which is produced as a one-piece molding from the outset, takes space due to the shape of the snap zipper. Its storage and handling therefore, are rather inconvenient. In addition, restrictions are imposed on the structure of the base film. Accordingly, the latter method (2) which is free from the above drawbacks is recently becoming a general method. EP-A-0371402 discloses a fastener, and a bag to which the fastener is welded, in which at least the portion of the fastener to be welded to the bag body is mainly made of ethylene vinyl acetate copolymer resin containing 1 to 9% vinyl acetate and having a melt index of 0.5 to 6.0 g/10 minutes. The snap zipper is usually made of low density polyethylene (LDPE) or polypropylene (PP). In many cases, a sealant layer (which forms the innermost layer of the bag body, and to which the snap zipper is fused), is applied to a base film of the same material. For example, with a base film sealant layer LDPE, the snap zipper is made of the same LDPE. With a sealant layer of the same material as the snap zipper, the snap zipper can be sealed to the sealant layer without any trouble. Meanwhile, polyester resins are excellent in their heat resistance and order retention property, and thus they are used suitably as the material of the sealant layer of the bag body. However, with a sealant layer of a polyester type resin which is a different material from LDPE or PP of the snap zipper, sufficient adhesion for fusing the snap zipper can not be obtained. Therefore, it has been difficult to use polyester type resin for the sealant layer. According to a first aspect of the present invention, there is provided a snap zipper in which at least its portion for fusion is mainly composed of polybutylene terephthalate (PBT) or polyester type elastomer, having a bending modulus of elasticity of 10,000 kg,cm 2 or below. In the snap zipper according to the invention, only the portion for fusion need be mainly composed of the PBT resin or polyester type elastomer. Of course, the entire snap zipper including the portion for fusion may be mainly composed of the PBT resin or polyester type elastomer. If the bending modulus of elasticity of the resin of the portion for fusion is above 10,000 kg/cm 2 , adequate flexibility necessary for the snap zipper can not be obtained. Generally, the lower the bending modulus of elasticity of the resin, the lower is the melting points of the PBT resin and polyester type elastomer, and correspondingly the temperature of fusion to the sealant layer is the lower. The snap zipper may, if necessary, contain suitable additives (such as coloring agent, stabilizing agent, anti-oxidization agent, slip agent, anti-static agent, anti-blocking agent, etc.). Slip agent are added usually. According to a second aspect of the invention, there is provided a bag with snap zipper, in which the snap zipper according to the first embodiment of the invention noted above is fused via the portion for fusion to a bag body. The snap zipper of the invention permits use of the polyester type resin for the bag body sealant layer, to which the snap zipper is fused. In this case, the snap zipper can be fused to the sealant layer without trouble. Besides, a sufficient strength of fusion between the bag body and the snap zipper is obtainable. For the snap zipper according to the invention, it is particularly suitable to use the polyester type resin as the material of the sealant layer. Examples of the polyester type resin are polyester (PET), polybutylene terephthalate (PET) resin, polyester type elastomer, polycarbonate, etc. It is possible to use a blend resin composed of polyester and polyolefin type resins. Such polyester type resins are excellent in heat resistance, odor retention and low drug absorption property, with the possibility of using this type of resins as the material of the sealant layer the following effects are obtainable. Regarding the prior art snap zipper, aluminum has been used as the material of the bag body in order to provide the odor retention and low drug absorption property. However, it is possible to permit cost reduction of the bag body by using polyester type resins in lieu of aluminum. Further, the bag may be made transparent by dispensing with aluminum layer. By so doing, it is possible to obtain a bag, through which the content can be seen while it provides the odor retention and low drug absorption properties. The bag which can be produced by using such polyester type resin, is suitable for fields, in which heat resistance such as boil and retort is required. As the material for the sealant layer may be used any resin other than the polyester type resins as well so long as it can be fused to the snap zipper. Examples of such resin are LDPE, L-LDPE, PP, ethylene-vinyl acetate copolymer (EVA), ethylene-methacrylic acid copolymer (EMAA), ionomer (IO), etc. As the outer layer material, nylon, PET, PP, cellophane, paper, etc. may be used as desired depending on desired characteristics. The snap zipper according to the invention may be fabricated by any method. Usually, it is produced using extrusion dies having sectional profiles corresponding to its shape for molding it and then cooling the resultant molding in water. Further, the shape of the snap zipper according to the invention is not limited to what comprises a male and a female member capable of chucking together, and any well-known shape may be adopted so long as it is capable of sealing and unsealing. The snap zipper may be fused to the bag body with well-known means such as heat, high frequency waves, ultrasonic waves, etc. In the accompanying drawings: Fig. 1 is a sectional view showing a male and a female member of an embodiment of the zipper according to the invention in a unchucked state; Fig. 2 is a sectional view showing the same embodiment of the zipper in the chucked state; Fig. 3 is a front view showing an embodiment of the bag with snap zipper according to the invention; and Fig. 4 is a sectional view showing the same embodiment of the bag with the snap zipper according to the invention. Example 1 A strip-like male and a strip-like female member 12 and 13 of the snap zipper 11 in these examples, as shown in Figs. 1 and 2, were produced by extrusion molding using PBT as material resin with an extruder, followed by water cooling. These members were taken up on into rolls. The bending modulus of elasticity of the PBT resin was 3,500 kg/cm 2 . Of these snap zippers 11, the flexibility and engagement performance were evaluated. Further, the thermal fusion temperature was measured. The results are shown in Table 1. The engagement performance was evaluated as such: It was A (Excellent), i.e., satisfactory, if the male and female members 12 and 13 could be readily engaged. It was B (Good), i.e., common, if the two members could be engaged. It was F (Fail), i.e., defective, if the two members could be difficulty engaged or could not be engaged. The flexibility was evaluated with respect to the state of take-up of the male and female members 12 and 13. The evaluation standards were as follows. The flexibility was A (Excellent), i.e., satisfactory, if the rolls of the taken-up male and female members 12 and 13 were satisfactory in appearance. It was B (Good), i.e., common, if the rolls were rather satisfactory in appearance. It was F (Fail), i.e., defective, if the rolls were unsatisfactory in appearance. The thermal fusion performance was evaluated as follows. It was A, i.e., satisfactory, if a strength of 300 g or above with a width of 15 mm was measured by using the thermal gradient tester noted above. It was F, i.e., defective, if the strength in the same measurement was below 300 g. Then, as shown in Figs. 3 and 4, the stem portions 14 and 17 of the male and female members 12 and 13 were thermally fused to base films 23 (70 µm thick) of the bag body 22, and then three sides of the films were heat sealed, thus obtaining the bag 24 with snap zipper in these examples. The base film 23 had a five-layer structure having four inner layers, i.e., a polyester type resin layer (15 µm), a PET layer (26 µm). a polyester type resin layer (12 µm) and an adhesive layer (5 µm) and an outer layer, i.e., a PET layer (12 µm). The innermost polyester type resin layer was the sealant layer of the bag body 22, to which the male or female member 12 or 13 was fused. EXAMPLES 2 TO 3 Like the Example 1, the individual examples of PBT snap zipper 11 were produced. Then bags with snap zipper 24 according to the individual examples were produced by using the respective zippers. Incidentally, the bending modulus of elasticity of the PBT resin are shown in Table 1. Of these snap zippers 11, the flexibility and engagement performance were evaluated as Examples 1. Further, the thermal fusion temperature was measured. The results are shown in Table 1. COMPARATIVE EXAMPLES 1 TO 5 Individual comparative examples of snap zipper were produced. Then bags with snap zipper according to the individual comparative examples were produced by using the respective zippers. Incidentally, the kinds and the bending modulus of elasticity of the used resin are shown in Table 1. Of these snap zippers, the flexibility and engagement performance were evaluated as Example 1. Further, the thermal fusion temperature was measured. The results are shown in Table 1. RESIN BENDING MODULUS OF ELASTICITY FLEXIBILITY THERMAL FUSION TEMPERATURE ENGAGEMENT PERFORMANCE EXAMPLES 1 PBT 3500 kg/cm 2 A 182°C A 2 PBT 7000 kg/cm 2 A 190°C A 3 PBT 10000kg/cm 2 B 198°C B COM. EXAM. 1 PBT 15000kg/cm 2 F 210°C F 2 PBT 25000kg/cm 2 F 227°C F 3 PBT 45000kg/cm 2 F 235°C F 4 LDPE - - DEFECTI VE THERMAL FUSION PERFORMANCE A 5 PP - - DEFECTIVE THERMAL FUSION PERFORMANCE A Since the snap zippers 11 in Examples 1 to 3 are made of PBT resin having the bending modulus of elasticity of more than 10000 kg/cm 2 , they are satisfactorily flexible, excellent in the performance of sealing and unsealing of the male and female members 12 and 13 (engagement performance) and satisfactory in appearance. Also, with the snap zippers of these examples satisfactory fusion can be ensured even if the sealant layer of the base film 23 of the bag body 24 is of a different material (polyester type resin) from that of the snap zipper 11, that is, the adhesion between the snap zipper 11 and sealant layer is satisfactory. Further, since the temperature of fusion to the sealant layer is comparatively low, the fusion can be readily attained. Thus, it is possible to increase the productivity. In addition, it is possible to obtain bag 24 with snap zipper 11 which has satisfactory appearance. With zippers in Comparative Examples 1 to 3, which are made of PBT resin, the flexibility and the engagement performance is not satisfactory and the fusion temperature is rather high since the bending modulus of elasticity is over 10000 kg/cm 2 . With zippers in Comparative Examples 4 to 5, which are made of LDPE or PP resin, the fusion performance is defective although the engagement performance is satisfactory. Examples 4 to 8 Like the Example 1, the individual examples of snap zipper 11 made of polyester type elastomer were produced. Then bags with snap zipper according to the individual Examples were produced by using the respective zippers. In Example 4 as polyester type elastomer was used "PELPRENE" (a trade name by Toyo Boseki Co., Ltd.), and in Examples 5 to 8 as polyester type elastomer was used "HYTREL" (a trade name by DUPONT-TORAY CO., Ltd.). The bending modulus of elasticity and the melting point of the polyester type elastomer are shown in Table 2. Of these snap zippers 11, the flexibility and engagement performance were evaluated as Example 1. Further, the thermal fusion temperature was measured. The results are shown in Table 2. COMPARATIVE EXAMPLES 6 - 8 Like the Example 1, the individual examples of snap zipper were produced. Then bags with snap zipper according to the individual comparative examples were produced by using the respective zippers. Incidentally, the bending modulus of elasticity and the melting point of the resin are shown in Table 2. Of these snap zippers, the flexibility and engagement performance were evaluated as example 1. Further, the thermal fusion temperature was measured. The results are shown in Table 2. RESIN BENDING MODULUS OF ELASTICITY MELTING POINT FLEXIBILITY THERMAL FUSION TEMPERATURE ENGAGEMENT PERFORMANCE EXAMPLES 4 PELPRENE P-150MS 1200 kg/cm 2 170°C B 146°C A 5 HYTREL 4767 1100 kg/cm 2 199°C B 154°C A 6 HYTREL 6347 3960 kg/cm 2 215°C A 200°C A 7 HYTREL 7247 6050 kg/cm 2 219°C A 196°C A 8 HYTREL 2571 9500 kg/cm 2 225°C B 163°C B COMPARATIVE EXAMPLES 6 HYTREL 2751 12800kg/cm 2 227°C F 202°C F 7 LDPE - - - DEFECTIVE THERMAL FUSION PERFORMANCE A 8 PP - - - DEFECTIVE THERMAL FUSION PERFORMANCE A With the snap zippers 11 in Examples 4 to 8, which are made of polyester type elastomers with a bending modulus of elasticity of 10,000 kg/cm 2 or below, it is possible to obtain the same effects as in Examples 1 to 3 using PBT resin. The same effects can also be obtained with the bags 24 with snap zipper 11. With the zipper in Comparative Example 6, which is made of polyester type elastomer, the bending modulus of elasticity is above 10,000 kg/cm 2 . The flexibility and engagement performance are defective. Besides, the thermal fusion temperature is comparatively high. With the zippers in Comparative Examples 7 and 8, which are made of LDPE or PP resin, the thermal fusion performance is defective although the engagement performance is satisfactory. As has been shown in the above examples, with the snap zipper and the bag with snap zipper according to the invention it is possible to obtain fusion of the snap zipper to the polyester type resin sealant of the bag body without any trouble and also obtain sufficient mechanical strength of fusion.

Claims: A snap zipper, in which at least a portion to be fused is mainly composed of polybutylene terephthalate (PBT) resin or polyester type elastomer, having a bending modulus of elasticity of 10,000 kg/cm 2 or below. A bag, to which a snap zipper according to claim 1, has been fused.

Inventors: TAKUBO TOYOKAZU, TANAKA KEN-ICHI, TAKUBO, TOYOKAZU, TANAKA, KEN-ICHI
Applicants: IDEMITSU PETROCHEMICAL CO, IDEMITSU PETROCHEMICAL CO. LTD.
Application year: 1993
Main classification: B65D33
IPC codes: B65D33, A44B19