A screw cap spout for soft packaging and a packaging bag containing the same

Abstract

The application discloses a screw cap nozzle for soft package, one end of the screw cap nozzle is provided with a base welded with a bag opening of a package bag, and a multilayer co-extrusion blown film or a composite film is welded on the heat sealing surface on the two sides of the base welded with the bag opening, the film can cover the pointed end on the base of the screw cap nozzle, thus the problem that the pointed end on the base of the unimproved screw cap nozzle is difficult to perfectly fit and causes poor heat sealing when directly welded with the inner layer of the package bag can be avoided. After the screw cap nozzle is welded with the package bag, the prepared package bag still has good sealing effect after pressure test and drop test.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of plastic packaging processing, and particularly relates to a screw cap nozzle for soft packaging and a packaging bag containing the same. BACKGROUND

[0002] When liquid is filled in a daily chemical product of soft packaging, a screw cap nozzle is usually arranged on the bag body, a base at the bottom of the screw cap nozzle is welded to the bag mouth, an opening is arranged at the top, and the contents are poured out through the opening during pouring, and in addition, a cap is usually arranged at the top for repeated use, which is a very convenient and common type of soft packaging.

[0003] The base material of the screw cap is usually HDPE (high-density polyethylene), which is welded to the inner PE (polyethylene) heat sealing layer of the bag body through a heat sealing mold, wherein the heat sealing mold is in contact with the outer side of the bag body and transmits the temperature from the outer side of the bag body to the inner side of the bag body and the heat sealing surface of the screw cap base, so that the heat sealing surface of the screw cap base and the inner side of the bag body are slightly fused and bonded together, thereby attaching the screw cap nozzle to the bag body.

[0004] Under ideal conditions, in order to meet the heat sealing temperature requirements for welding the bag body and the screw cap nozzle, the heating temperature of the heat sealing mold of the bag body material to the outer side of the bag should reach the temperature at which the HDPE screw cap base in contact with the inner PE layer of the bag body can be melted, so that the heat resistance of the inner layer material and the outer layer material of the general bag body composite material is quite different. For example, PET (polyethylene terephthalate) is selected as the outer layer, and PE is selected as the inner layer heat sealing material, wherein the melting temperature of LDPE (low-density polyethylene) and LLDPE (linear low-density polyethylene) as the inner layer material is between 100℃ and 120℃, and the temperature at which the material such as PET or PA (polyamide) of the outer layer does not deform and break after printing graphics is greater than 150℃, and the heat resistance temperature is greater than 150℃. The heat sealing temperature is set at about 130℃, which is the melting temperature of the HDPE material of the bag nozzle base. At this time, the bag body will not be burnt and deformed due to the high heat resistance of the PET on the surface, and the heat sealing temperature can also reach the melting temperature of the HDPE material of the base, so that successful heat sealing can be achieved.

[0005] In fact, the temperature and pressure of heat sealing of the soft single-layer composite material and the hard screw cap base need to be well controlled, so that the inner layer heat sealing PE layer cannot be pressed too thin under high temperature. In the production process, due to the difference in the fitting accuracy of the heat sealing mold and the screw cap nozzle base, temperature fluctuation and working cylinder gas source pressure fluctuation, the inner layer PE material may be pressed too thin in the molten state, so that the bag body heat sealing area may be pressed too thin or the inner layer PE layer material may be pressed through, and the bag may be broken during falling.

[0006] In another single material packaging, if the outer side of the bag body uses high temperature resistant extruded PE, co-extruded blown film PE, BOPE (biaxially oriented polyethylene) or MDOPE (monoaxially oriented polyethylene) with a sealing temperature of 130 DEG C, and the inner side uses PE material with a low sealing temperature of 105 DEG C, and the rotating cap nozzle still uses a base with a melting temperature of about 130 DEG C, when the heat sealing temperature is set at 130 DEG C, the PE layer of the surface layer is not temperature resistant, and the printed pattern will be blurred and burnt in the presence of printed content. Since the overall material has poor heat resistance, the bag in a molten state is more likely to cause melt stretching deformation or thinning under the base during processing and movement, and is more likely to cause the bag to break after falling after being filled with contents. In addition, in the case of a small temperature difference, the actual heat sealing temperature must be reduced, the heating time must be extended, and the heat sealing pressure must be reduced to achieve heat sealing, and the processing efficiency is very low.

[0007] In addition, in order to ensure certain structural rigidity and injection convenience, HDPE is usually directly injection molded into the rotating cap nozzle, and the two heat sealing surfaces on the base of the rotating cap nozzle are welded to the bag body, and the junction of the two heat sealing surfaces forms a sharp end. Since the position of the sharp end usually has a certain chamfer due to the design requirements of the mold, the thickness is much greater than the actual thickness of the packaging bag, which causes the inner heat sealing layer of the packaging bag to be difficult to form a good fit with the sharp end of the base of the rotating cap nozzle during heat sealing, and further causes poor heat sealing. At this time, the heat sealing pressure can be increased to make the inner heat sealing layer of the packaging bag form a good fit with the sharp end, but this will cause new problems, i.e., the welded surface area of the base is prone to cause the film to be pressed too thin, resulting in a decrease in heat sealing strength. If the bag body is pressed too thin during heat sealing, the bag body is prone to breakage during transportation, resulting in leakage of the contents and a decrease in product quality. SUMMARY

[0008] In order to overcome the shortcomings and deficiencies of the prior art, the present application provides a rotating cap nozzle for soft packaging, which is welded with a layer of film on the heat sealing surface of the base of the rotating cap nozzle, so that perfect heat sealing can be achieved when the rotating cap nozzle is welded to the packaging bag, and the packaging bag will not break during falling.

[0009] The object of the present application is achieved by the following technical solutions:

[0010] In a first aspect, the present application provides a rotating cap nozzle for soft packaging, one end of the rotating cap nozzle is provided with a base welded to the bag opening of the packaging bag, and a multi-layer co-extruded blown film or composite film is welded on the heat sealing surface on both sides of the base welded to the bag opening.

[0011] Preferably, the multi-layer co-extruded blown film or composite film comprises at least a front layer, a core layer and a back layer, the core layer is located between the front layer and the back layer, and the front layer is welded to the heat sealing surface of the base.

[0012] Preferably, the heat sealing temperature of the front layer and the back layer is lower than that of the core layer.

[0013] Preferably, the front layer and the back layer are made of PE, and the core layer is made of PE or PA.

[0014] Preferably, the front layer and the back layer are made of PP, and the core layer is made of PA.

[0015] Preferably, the cap nozzle is integrally injection molded by HDPE or PP.

[0016] In the second aspect, the application further provides a packaging bag comprising a cap and a bag body with a bag opening, and further comprising the cap nozzle as described in the first aspect, the cap nozzle being welded to the inner side of the bag opening through the multi-layer co-extrusion blown film or the composite film on the base; and the cap is threadedly connected to the cap nozzle.

[0017] Preferably, the temperature at which the back layer of the multi-layer co-extrusion blown film or the composite film achieves the best heat sealing effect with the inner side material of the bag body is lower than the temperature at which the outermost material of the bag body is deformed by printing pattern scorching under normal heat sealing conditions.

[0018] The application has the following advantages and effects over the prior art:

[0019] The application first welds a multi-layer co-extrusion blown film or a composite film on the heat sealing surface of both sides of the cap nozzle base, the films welded on both sides can cover the sharp end on the cap nozzle base, and the multi-layer co-extrusion blown film or the composite film can form a smooth, regular and sharp-free extension surface after being welded and attached. The cap nozzle and the packaging bag are welded through the welded extension surface, so that the problem of poor heat sealing caused by the difficulty in perfect attachment of the sharp end on the cap nozzle base and the inner layer of the packaging bag during direct contact and welding can be avoided.

[0020] Secondly, the multi-layer co-extrusion blown film or the composite film with a relatively low heat sealing temperature is used, and the heat sealing temperature used when the cap nozzle and the bag body of the packaging bag are welded only needs to meet the heat sealing of the film and the packaging bag. In this way, when the heat sealing temperature of the outer material of the packaging bag and the heat sealing temperature of the cap nozzle base are relatively close, since the heat sealing temperature of the multi-layer co-extrusion blown film or the composite film pre-welded on the cap nozzle base is relatively low, the heat sealing temperature only needs to meet the heat sealing temperature requirement of the multi-layer co-extrusion blown film or the composite film when the cap nozzle and the packaging bag are welded. In this way, the problems of scorching, wrinkling and deformation of the outer layer of the packaging bag caused by the excessively high heat sealing temperature can be solved.

[0021] The rotating cap nozzle in the application is suitable for packaging bags with different composite film structures of outer layer and inner layer materials, such as a packaging bag composed of PET as the outer layer and PE as the inner layer, a packaging bag composed of PET as the outer layer, BOPA as the intermediate layer and PE as the innermost layer, a packaging bag composed of BOPA as the outer layer and PE as the inner layer, a packaging bag composed of BOPP as the outer layer and CPP as the inner layer, and the like, and is also suitable for a full-PE material packaging bag composed of BOPE as the outer layer and PE as the inner layer, and has the effect of strengthening the welding quality of single-material packaging bags or traditional multi-layer different-material composite film structure packaging bags. The additional film layer of the application has little cost increase, and the welding process is simple and convenient. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The rotating cap nozzle in the comparative example.

[0023] Figure 2 The rotating cap nozzle in Example 1.

[0024] Figure 3 The packaging bag and rotating cap nozzle assembly schematic diagram in Example 2. DETAILED DESCRIPTION

[0025] The technical solutions in the examples will be described clearly and completely below. Obviously, the examples described below are only some of the examples of the application, not all the examples. Based on the examples in the application, all other examples obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0026] It should be understood that when used in the specification and the appended claims, the terms "comprise" and "include" indicate the presence of described features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0027] It should also be understood that the terms used in the specification of the embodiments of the application herein are only for the purpose of describing specific examples and do not intend to limit the embodiments of the application. As used in the specification and the appended claims of the embodiments of the application, the singular forms "a", "an" and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0028] Comparative Example 1

[0029] The comparative example provides a packaging bag, the bag body composite film is BOPE25 / PE140, BOPE25 / PE140 indicates that the BOPE of 25um is compounded with the PE of 140um as the inner layer, wherein the heat sealing temperature of the BOPE layer is 135 DEG C, the heat sealing initiation temperature of the inner layer PE layer is 95 DEG C, and the maximum heat sealing strength temperature of the composite film is 120 DEG C.

[0030] The heat sealing temperature is the temperature set by the heat sealing mold when the material is heat sealed without surface scorching and causing the deformation of the pattern of the printing layer. The heat sealing initiation temperature is the temperature at which the mutual adhesion force appears after the material is heat sealed. The maximum heat sealing strength temperature is the temperature at which the maximum heat sealing strength appears after the material is heat sealed.

[0031] In the comparative example, the heat sealing region of the bag opening of the packaging bag is directly heat sealed with the heat sealing surface on the cap base in the preset position by using a heat sealing mold. The cap is directly used in the comparative example after being integrally injection molded from HDPE. As shown in FIG. 1, the cap base integrally injection molded from HDPE has two heat sealing surfaces 1, each of which is provided with a plurality of heat sealing channels. The end points of the edges of the two heat sealing surfaces form a sharp end. Figure 1

[0032] The heat sealing temperature of the heat sealing mold is set to 132 DEG C, the heat sealing pressure is 0.2 MPa, and the heat sealing time is 1.2 s. Wrinkles appear on the welded surface of the packaging bag after welding.

[0033] Twenty-four packaging bags with the cap integrally injection molded from HDPE are taken, the same amount of water is poured into each of the packaging bags, and the cap is sealed. The pressure test is performed under a pressure testing machine. The pressure resistance pressure is set to 3000 N, and the time is maintained for 3 minutes. Six packaging bags are broken and leaked at the welded junction between the cap base and the bag opening after the pressure resistance test.

[0034] Twenty-four packaging bags with the cap integrally injection molded from HDPE are taken, 1.5 kg of water is poured into each of the packaging bags, and each of the packaging bags is dropped once with the front face downward, once with the back face downward, and three times with the bottom downward at a height of 1.2 m. The test result shows that five packaging bags are torn at the welded position between the bag opening and the cap.

[0035] The thickness of the inner layer PE layer near the welded position of the packaging bag is measured by using an electron microscope. The inner layer PE layer with the thickness of 140 um is compressed to 85-100 um during the heat sealing process.

[0036] Comparative Example 2

[0037] ​The difference between the present comparative example and the packaging bag of Comparative Example 1 is that the present comparative example reduces the heat sealing pressure and then directly contacts the newly packaged bag and the cap nozzle for heat sealing. The cap nozzle is integrally injection molded from HDPE and directly used in the present comparative example. The heat sealing temperature of the heat sealing mold is set to 132°C, the heat sealing pressure is 0.1 MPa, and the heat sealing time is 1.2 s. After welding, the welded surface of the packaging bag is flat and has no obvious wrinkles.

[0038] Take 24 packaging bags with continuously welded and attached cap nozzles, fill them with the same amount of water, and seal the cap. Perform pressure resistance testing under a pressure testing machine. Set the pressure resistance pressure to 3000N and maintain for 3 minutes. Among them, 5 packaging bags have the bag film separated from the cap nozzle base at the welded junction between the cap nozzle base and the bag opening after pressure resistance testing. The film has poor bonding force at the tip of the cap nozzle base, resulting in leakage.

[0039] Take another 24 packaging bags with continuously welded and attached cap nozzles. Fill each packaging bag with 1.5 kg of water, and make each packaging bag experience 1 drop with the front facing down, 1 drop with the back facing down, and 3 drops with the bottom facing down at a height of 1.2 m. The test results show that 5 packaging bags have slight separation between the inner PE film and the cap nozzle base, resulting in leakage near the bag opening and the tip of the cap nozzle base.

[0040] By using an electron microscope to measure the thickness of the cross-section of the inner PE layer near the welded position of the damaged packaging bag, it is found that the original 140 um thick inner PE layer is compressed to 110-120 um during heat sealing.

[0041] Comparative Example 3

[0042] The packaging bag body composite film of the present comparative example is BOPET12 / BOPA15 / PE140, which means that 12 um of BOPET is compounded with 15 um of intermediate layer BOPA, and then compounded with the innermost layer of 140 um of PE. The heat sealing temperature of BOPET compounded BOPA layer is more than 150°C, the heat sealing initiation temperature of the inner PE layer is 95°C, and the maximum heat sealing strength temperature of the bag body composite film is 120°C.

[0043] The present comparative example directly positions the pre-set heat sealing area of the bag opening of the packaging bag and the heat sealing surface on the cap nozzle base according to the pre-set position, and then uses a heat sealing mold for heat sealing. The cap nozzle is integrally injection molded from HDPE and directly used in the present comparative example. The heat sealing temperature of the heat sealing mold is set to 140°C, the heat sealing pressure is 0.2 MPa, and the heat sealing time is 1.2 s. The welded surface of the packaging bag after welding is flat and has no obvious wrinkles.

[0044] Take 24 continuously welded and fitted with upper rotary cap nozzle packaging bags, fill the same amount of water and seal the rotary cap, and perform pressure test under the pressure test machine. Set the pressure resistance pressure to 3000N, and maintain for 3 minutes. All 24 packaging bags can pass the pressure test, and the packaging bags do not appear to be broken and leaked.

[0045] Take another 24 continuously welded and fitted with upper rotary cap nozzle packaging bags, fill each packaging bag with 1.5 kg of water, and make each packaging bag experience 1 drop with the front down, 1 drop with the back down, and 3 drops with the bottom down at a height of 1.2 m. The test results show that all 24 packaging bags are not broken and leaked.

[0046] Test the packaging bags in a low temperature environment. Take 24 continuously welded and fitted with upper rotary cap nozzle packaging bags, fill each packaging bag with 1.5 kg of water, and place each 6 bags in a box after sealing the box and placing it in a 2°C environment for 24 hours. Immediately after taking out, drop the box from a height of 1.2 m, with the bottom of the box down 3 times, the left side of the box down 1 time, and the right side of the box down 1 time. Check the breakage of each packaging bag, and find that 3 packaging bags have broken corners and 2 packaging bags have broken at the welding site of the bag opening and the rotary cap nozzle.

[0047] Measure the thickness of the inner layer PE layer near the welding position of the damaged packaging bag by using an electron microscope to measure the cross section of the inner layer PE layer. The 140 um thick inner layer PE layer is compressed to 110-120 um during the heat sealing process.

[0048] Example 1

[0049] This example provides a rotary cap nozzle for soft packaging, which is integrally injection molded from HDPE with a melting temperature of 130°C, and a melting temperature of the heat sealing surface of the base of the rotary cap nozzle is welded to a multi-layer co-extruded blown film.

[0050] The steps of welding the multilayer co-extrusion blown film on the heat sealing surface of the base of the screw cap nozzle are as follows: a PE blown film with a three-layer co-extrusion blown film structure is prepared, the PE blown film has the same width as the heat sealing surface of the base of the screw cap nozzle, and the thickness is 140 μm. The PE blown film has a structure of front layer-core layer-back layer, wherein the heat sealing temperature of the front layer and the back layer is 110-120°C. The core layer is a PE material with a melting temperature 5-10°C higher than that of the front layer and the back layer. The front layer of the PE blown film is welded and attached to the heat sealing surface of the base of the screw cap nozzle on a heat sealing mold. The surface of the heat sealing mold in contact with the PE blown film is coated with a Teflon coating. The temperature of the heat sealing mold is set to 132°C, the heat sealing pressure is 0.1 MPa, the heat sealing time is 1.2 s, and the two heat sealing surfaces of the base of the screw cap nozzle are welded with the PE blown film. Since the heat sealing temperature of the front layer and the back layer of the PE blown film is 110-120°C, the temperature provided by the heat sealing mold is sufficient to heat seal and attach the front layer of the PE blown film to the heat sealing surface of the base of the screw cap nozzle. Although the back layer of the PE blown film is in a molten and highly viscous state during the welding process, the surface of the back layer in contact with the heat sealing mold is coated with Teflon, and the non-stick property of Teflon can ensure the integrity of the back layer of the PE blown film. The core layer of the PE blown film has a higher heat sealing temperature than the front layer, so the core layer of the PE blown film is not affected by the heat sealing temperature during welding, and thus remains intact without breaking. After the welding of the PE blown film and the base of the screw cap nozzle is completed, if the welding with the bag body is not performed immediately, the PE blown film on the base of the screw cap nozzle can be shaped by a shaping mold after slight cooling, so that the PE blown film on the base of the screw cap nozzle remains flat.

[0051] In addition, a sharp end will be formed on the heat sealing surface of the base of the screw cap nozzle after injection molding. In this embodiment, the PE blown film is attached to the two heat sealing surfaces of the base of the screw cap nozzle, the PE blown film is combined with the sharp end on the base of the screw cap nozzle, and an extension surface is formed after the welding and attachment. After shaping and die cutting of the extension surface, the sharp end of the base of the screw cap nozzle is covered by the PE blown film and forms a regular welded extension surface without a sharp end. If the screw cap needs to be welded with the bag opening of the packaging bag later, only the inner layer of the packaging bag needs to be welded with the welded extension surface. Figure 2

[0052] The thickness of the PE blown film is measured by using an electron microscope. The original total thickness of the PE blown film is 140 μm, and the PE blown film is compressed to about 100-115 μm during the heat sealing process.

[0053] Example 2

[0054] In this embodiment, the screw cap prepared in Example 1 is used to weld with the bag opening of the packaging bag. The packaging bag is BOPE25 / PE140.

[0055] As shown in Figure 3 ​The pre-set heat sealing area of the bag opening of the packaging bag 3 and the heat sealing surface on the cap base are positioned at the pre-set position, and then heat sealing is performed using a heat sealing mold. The heat sealing mold is set to a heat sealing temperature of 120°C, a heat sealing pressure of 0.2 MPa, and a heat sealing time of 1.2 s. During heat sealing, the PE layer on the inner side of the bag body is heat sealed with the back layer of the PE blown film on both sides of the cap base, and the cap base tip position is heat sealed with the PE blown film. The welded surface of the bag is flat and has no obvious wrinkles.

[0056] Twenty-four packaging bags with the cap base continuously welded and attached are filled with the same amount of water and sealed. The pressure test is performed on a pressure testing machine. The pressure test pressure is set to 3000 N, and the time is maintained for 3 minutes. The 24 packaging bags can pass the pressure test, and the packaging bags do not leak.

[0057] Twenty-four packaging bags with the cap base continuously welded and attached are taken again. Each packaging bag is filled with 1.5 kg of water. Each packaging bag is dropped once with the front face down, once with the back face down, and three times with the bottom face down at a height of 1.2 m. The test results show that the 24 packaging bags do not break and leak. The cap base tip position of each packaging bag is checked in turn, and it is found that the welding state of the PE blown film and the base is good, and there is no separation phenomenon.

[0058] The thickness of the PE layer on the inner side of the bag body and the PE blown film is measured by using an electron microscope. The total thickness of the PE layer on the inner side of the bag body and the PE blown film is 185-210 um on average.

[0059] In this embodiment, the cap base with the PE blown film is welded with the packaging bag. The PE blown film welding extension surface on the cap base base is heat sealed and welded with the inner layer of the packaging bag. The PE blown film extends to the tip of the base to form a preliminary attachment and provides more material to fill the tip of the base and the inner layer of the packaging bag, so that the welding effect is optimized. At the same time, the back layer of the PE blown film is heat sealed with the packaging bag after the heat sealing surface on the cap base is increased with the PE blown film. At this time, since the heat sealing temperature of the back layer of the PE blown film is only 110°C-120°C, the heat sealing mold only needs to be set to a heat sealing temperature of 120°C to achieve perfect heat sealing of the cap and the packaging bag. Since the heat sealing temperature of the outer layer BOPE layer of the packaging bag is 135°C, the heat sealing mold contacts the outer layer of the packaging bag to transfer the temperature to the inner layer and the PE blown film to achieve heat sealing and welding. Therefore, the heat sealing temperature is much lower than the heat sealing temperature of the outer layer BOPE layer of the packaging bag. In this way, in the case of printing patterns on the outer layer, the heat sealing temperature does not need to be increased to 130°C, which is the heat sealing temperature of the cap base without the PE blown film, so that the heat sealing temperature does not need to be too high to cause the printed patterns on the outer layer to be blurred and burnt.

[0060] Example 3

[0061] The bag body composite film of the packaging bag of the present example is BOPE25 / PE110. The packaging bag of the present example differs from that of Example 2 in that the thickness of the inner PE layer of the packaging bag of the present example is thinner than that of Example 2. The heat sealing temperature of the BOPE layer is 135℃, the heat sealing starting temperature of the inner PE layer is 95℃, and the temperature at which the composite film reaches the maximum heat sealing strength is 120℃. The spin cap nozzle prepared in Example 1 and the packaging bag of the present example are welded.

[0062] The pre-set heat sealing area of the bag opening of the packaging bag is positioned at the pre-set position with the heat sealing surface on the base of the spin cap nozzle, and then heat sealing is performed using a heat sealing mold. The heat sealing temperature of the heat sealing mold is set to 120℃, the heat sealing pressure is 0.2MPa, and the heat sealing time is 1.2s. During heat sealing, the PE layer on the inside of the bag body is heat sealed with the back layer of the PE blown film on both sides of the base of the spin cap nozzle, and a conformal heat sealing is formed at the position of the tip of the base of the spin cap nozzle with the PE blown film. The welded surface of the bag after welding is flat and has no obvious wrinkles.

[0063] Twenty-four packaging bags with spin cap nozzles continuously welded and attached are taken, filled with the same amount of water, and sealed with spin caps. Pressure testing is performed under a pressure testing machine. The pressure resistance pressure is set to 3000N, and the time is maintained for 3 minutes. The twenty-four packaging bags all pass the pressure resistance test, and no leakage occurs in the packaging bags.

[0064] Another twenty-four packaging bags with spin cap nozzles continuously welded and attached are taken. Each packaging bag is filled with 1kg of water, and each packaging bag experiences falling once with the front face downward, once with the back face downward, and three times with the bottom downward at a height of 1.2m. The test results show that the twenty-four packaging bags all have no rupture and leakage. The tip position of the base of the spin cap nozzle of each packaging bag is checked in turn, and it is found that the welding state of the PE blown film and the base is good and has no separation phenomenon.

[0065] The thickness of the cross section of the inner PE layer of the bag body and the PE blown film is measured by using an electron microscope. The total thickness of the inner PE layer of the bag body and the PE blown film is averagely 160-190um.

[0066] It can be known from the comparison between the present example and Example 2 that the spin cap nozzle with the PE blown film can be heat sealed with the packaging bag with a thinner bag body, and the packaging bag will not be pressed thin and broken.

[0067] Example 4

[0068] The present example provides a spin cap nozzle which is integrally injection molded from HDPE with a melting temperature of 130℃. Five layers of co-extruded blown film are welded on the heat sealing surface of the base of the spin cap nozzle. The specific welding process is as follows:

[0069] Prepare a five-layer co-extrusion blown film, the blown film is the same width as the heat-seal surface of the cap base, the blown film is PE / adhesive layer / PA / adhesive layer / PE structure, the front and back surfaces of the blown film are PE materials with a heat-seal temperature of 110-120°C, the core layer is PA material with a higher melting temperature than the front and back surface PE materials, the thickness is 10 μm, and the melting temperature is 220-240°C. The other layers of PE materials and adhesive materials required for co-extrusion are 130 μm in total, and the total thickness of the entire blown film is 140 μm. It should be noted that when the multi-layer co-extrusion blown film or the composite film has a structure of three or more layers, the front layer is one of the outermost layers of the film, the back layer is the other outermost layer of the film, and the core layer refers to a certain layer in the middle, and the other layers are regarded as other layers.

[0070] Weld and attach the front surface of the blown film to the heat-seal surface of the cap base on the heat-seal mold, the surface of the heat-seal mold in contact with the blown film is coated with a Teflon coating, the temperature of the heat-seal mold is set to 140°C, the heat-seal pressure is 0.2 MPa, and the heat-seal time is 1.0 s, and the two heat-seal surfaces of the cap base are welded to the blown film. Since the heat-seal temperature of the front and back layers of the blown film is 110-120°C, the temperature provided by the heat-seal mold is sufficient to heat-seal and attach the front layer of the blown film to the heat-seal surface of the cap base; although the back layer of the blown film is in a molten and highly viscous state during welding, the surface of the blown film in contact with the heat-seal mold is coated with Teflon, and the non-stick properties of Teflon can ensure the integrity of the back surface of the blown film. The core layer of the blown film has a much higher heat resistance than 140°C, so the core layer of the blown film is not affected by the heat-seal temperature during welding, and thus remains intact without breaking. After the blown film and the cap base are welded, if the welding with the bag body is not performed immediately, the blown film on the cap base can be shaped by a shaping mold after slight cooling, so that the blown film on the cap base remains flat.

[0071] In this embodiment, the blown film is attached to both heat-seal surfaces of the cap base, the blown film is combined with the tip of the cap base, and an extension surface is formed after welding and attaching. After shaping and die cutting the extension surface, the tip of the cap base is covered by the blown film and forms a regular welded extension surface without a tip. If the cap is to be welded to the bag opening later, only the inner layer of the bag needs to be welded to the welded extension surface.

[0072] The thickness of the cross-section of the blown film at the welding position is measured by using an electron microscope. The total thickness of the blown film is originally 140 μm, and the blown film is compressed to about 105-120 μm during heat-sealing.

[0073] Example 5

[0074] In this embodiment, a packaging bag is provided, and the difference between this embodiment and Comparative Example 3 is that the cap prepared in Example 4 is used to weld the packaging bag.

[0075] The pre-set heat sealing area of the bag opening of the packaging bag and the heat sealing surface on the base of the screw cap nozzle are positioned at the pre-set position, and then heat sealing is performed using a heat sealing mold. The heat sealing temperature of the heat sealing mold is set to 120°C, the heat sealing pressure is 0.2 MPa, the heat sealing time is 1.2 s, the PE layer on the inner side of the bag body is heat sealed with the back layer of the blown film on both sides of the base of the screw cap nozzle, and the blown film is heat sealed at the tip position of the base of the screw cap nozzle. The welded surface of the bag is flat and has no obvious wrinkles.

[0076] Twenty-four packaging bags with continuously welded and fitted screw cap nozzles are filled with the same amount of water and sealed, and then subjected to pressure test under a pressure testing machine. The pressure test pressure is set to 3000N, and the time is maintained for 3 minutes. The 24 packaging bags all pass the pressure test, and no leakage occurs in the packaging bags.

[0077] Another 24 packaging bags with continuously welded and fitted screw cap nozzles are taken, each of which is filled with 1.5 kg of water, and each of which is subjected to a drop of 1 time with the front face downward, a drop of 1 time with the back face downward, and a drop of 3 times with the bottom downward at a height of 1.2 m. The test results show that the 24 packaging bags all have no rupture and leakage. The tip position of the base of the screw cap nozzle of each packaging bag is checked in turn, and it is found that the welding state of the blown film and the base is good and has no separation phenomenon.

[0078] The thickness of the PE layer in the bag body and the cross section of the blown film is measured by using an electron microscope, and the total thickness of the PE layer in the bag body and the blown film is averagely 215-230 um.

[0079] The packaging bags are tested in a low temperature environment. Twenty-four packaging bags with continuously welded and fitted screw cap nozzles are taken, each of which is filled with 1.5 kg of water, and each of which is subjected to a drop of 3 times with the bottom of the box downward, a drop of 1 time with the left side of the box downward, and a drop of 1 time with the right side of the box downward at a height of 1.2 m after being packed in a box every 6 bags and being placed in a 2°C environment for 24 hours. The rupture of each packaging bag is checked, and it is found that only the bottom corners of 2 packaging bags are ruptured, and the welded parts of all the packaging bags and the screw cap nozzles have no rupture.

[0080] It can be known by comparing Comparative Example 1 and Comparative Example 3, and Example 5 and Comparative Example 3 that although the packaging bags with different material combinations can improve the temperature resistance of the bag body so as to facilitate the heat sealing of the packaging bags and the screw cap nozzles, the heat sealing strength of the bag body and the screw cap nozzle is still insufficient in a low temperature environment, and the heat sealing effect of the bag body and the screw cap nozzle can be improved by adding a layer of blown film, so that the packaging bags can still maintain good heat sealing strength after being subjected to a low temperature.

[0081] It should be noted that in addition to using a co-extrusion blown film process to form the front layer-core layer-back layer structure as described above, a structure meeting the above requirements can also be formed by a multi-layer composite process, such as PE / BOPA / PE, PE / PP / PE, etc. In addition, in the packaging field, due to the higher heat sealing strength of PE film compared to PP, PET, etc., it is a general and low-cost preferred material, but the material of the composite film or multi-layer co-extrusion blown film can be replaced according to production needs to have a certain melting temperature difference with the material of the screw cap nozzle base, such as a screw cap nozzle base made of PP polypropylene injection molding, the corresponding composite film or multi-layer co-extrusion blown film can be two layers of PP material with other material layers in between, such as a material structure of two layers of PP material with a PA (polyamide) layer in between (PP / PA / PP).

[0082] The above embodiments are preferred embodiments of the present application, but the embodiments of the present application are not limited by the above embodiments, and any changes, modifications, substitutions, combinations, simplifications made without departing from the spirit and principles of the present application are equivalent replacement methods and are included in the protection scope of the present application.

Claims

1. A screw cap for a soft package, one end of the screw cap being provided with a base to be welded to a bag opening of the package, characterized in that, A multi-layer co-extrusion blown film or composite film is welded on the heat sealing surface of the base on both sides of the bag opening; the multi-layer co-extrusion blown film or composite film comprises at least a front layer, a core layer and a back layer, the core layer is between the front layer and the back layer, the heat sealing temperature of the front layer and the back layer is lower than that of the core layer, and the front layer is welded with the heat sealing surface of the base through a heat sealing mold, and the surface of the heat sealing mold in contact with the back layer is coated with a Teflon coating.

2. A flip cap closure for a soft pack according to claim 1, characterised in that, The front layer and the back layer are PE materials, and the core layer is PE or PA material.

3. A flip cap closure for a soft pack according to claim 1, wherein, The front layer and the back layer are PP materials, and the core layer is PA material.

4. The screw cap nozzle for flexible packaging according to claim 1, characterized in that, The screw cap nozzle is integrally injection molded by HDPE or PP.

5. A package comprising a spin cap and a bag body having a bag mouth, characterized in that The screw cap nozzle is welded with the inside of the bag opening through the multi-layer co-extrusion blown film or composite film on the base; the screw cap is threadedly connected with the screw cap nozzle.

6. The package of claim 5, wherein, The temperature at which the back layer of the multi-layer co-extrusion blown film or composite film and the material inside the bag body achieve the best heat sealing effect is lower than the temperature at which the outermost material of the bag body occurs printing pattern scorching deformation under normal heat sealing conditions.

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