A method for preventing the pulling-off of a rubber cap

Abstract

The application discloses a kind of for adhesive cap anti-pulling-off bonding method, belong to packaging anti-fake technical field.This method is processed in the lower edge of heat shrinkable adhesive cap linearly graded step intermittent anti-pulling-off line, and the position of bottle cap neck is pasted in the inner wall of adhesive cap double-temperature zone activation layered composite double-sided adhesive film, so that the lower edge of adhesive film overlaps and covers the upper end area of anti-pulling-off line, and the shrinkage of adhesive cap and the activation of double-temperature zone heat-sensitive adhesive are completed synchronously by hot air, to realize the irreversible bonding of adhesive cap and bottle cap neck.The composite adhesive film is composed of acrylic pressure-sensitive adhesive layer and two-component modified EVA irreversible heat-sensitive adhesive layer, and forms a mechanical stop structure after heat shrinking.The application solves the problems of traditional adhesive cap, such as easy to be pulled out without damage, low process fault tolerance, inconvenient opening, etc.Forced disassembly will cause the adhesive cap to tear and the cohesive failure of adhesive layer, and cannot be recycled and reused, with the characteristics of irreversible anti-fake, high process fault tolerance, convenient opening and strong environmental adaptability.

Description

Technical Field

[0001] This invention relates to the field of packaging anti-counterfeiting technology, and in particular to an adhesive method for preventing the caps from being pulled off. Background Technology

[0002] In the packaging of high-end bottled goods such as alcoholic beverages and health products, heat-shrinkable caps are the mainstream anti-counterfeiting sealing components. Traditional caps rely solely on the heat-shrinking clamping force for fixation, lacking structural adhesive protection. Criminals can easily remove them without damage by softening with hot air or using pry tools, thus using genuine caps on counterfeit products, seriously infringing on the rights and interests of brands and consumers.

[0003] Existing technologies suffer from the following drawbacks: insufficient or excessively strong single-layer adhesive bonding strength, making it difficult to simultaneously address both anti-counterfeiting and tamper-evident aspects; poor fit between the anti-pull-out line and the adhesive layer, making it easily blocked or a potential entry point for counterfeiting; limited activation temperature of the thermosensitive adhesive, resulting in low process tolerance and easy adhesion failure; and a lack of structural anti-pry design, leaving the possibility of non-destructive disassembly. Therefore, there is an urgent need for an irreversible, non-destructive transfer-proof, easy-to-open, and highly process-tolerant cap-resistant adhesive bonding technology.

[0004] Based on the above pain points, there is an urgent need to develop an adhesive method for preventing cap pull-out that combines strong anti-transfer performance, convenient normal opening, and process tolerance, which can significantly improve the anti-pull-out and anti-transfer effects, while being compatible with existing heat shrink production lines without adding extra production difficulty. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the existing technology and provide an adhesive method for preventing the cap from being pulled off, so as to achieve irreversible bonding between the cap and the bottle cap, eliminate non-destructive counterfeiting, and at the same time ensure convenient opening and compatibility with existing production lines.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: an adhesive method for preventing the cap from being pulled off, comprising the following steps: Step 1: Obtain a heat-shrinkable cap with a circumferential anti-pull-out line formed on its lower edge; Step 2: Adhere a composite double-sided adhesive film to the inner wall of the cap at the position corresponding to the neck of the bottle cap; the adhesive film includes a pressure-sensitive adhesive layer and a dual-temperature zone activated irreversible heat-sensitive adhesive layer from top to bottom; Step 3: Place the cap with the adhesive film onto the neck of the bottle cap and perform heat shrink treatment; the temperature of the heat shrink treatment simultaneously activates the low-temperature zone and the high-temperature zone of the heat-sensitive adhesive layer, causing the cap to shrink and adhere to the neck of the bottle cap, and form an irreversible bond after cooling.

[0007] Furthermore, the anti-pull-out line is a stepped discontinuous anti-pull-out line, which is composed of breakpoints with gradually changing depth. The breakpoint depth of the stepped discontinuous anti-pull-out line gradually changes linearly along the circumference. The breakpoint depth near the glue-free opening area is 0.3-0.5mm, and the breakpoint depth far from the glue-free opening area is 0.1-0.2mm.

[0008] Furthermore, the dual-temperature zone activated irreversible heat-sensitive adhesive layer is achieved by multi-layer co-extrusion, phase separation, and blending of EVA with different molecular weights; the lower edge of the adhesive film extends downward and overlaps to cover the upper area of ​​the anti-pull-out line, and the adhesive film covers a portion of the area circumferentially along the inner wall of the cap, reserving a no-adhesive opening area. The dual-temperature zone activated irreversible heat-sensitive adhesive layer includes: a low-temperature activation layer activated at 50-55℃ for pre-positioning during the heat shrinking process; and a high-temperature activation layer activated at 60-65℃ for providing final irreversible strong adhesion.

[0009] Furthermore, the adhesive film can cover the anti-pull-out wire area, the upper part of the anti-pull-out wire area, and the lower part of the anti-pull-out wire area.

[0010] Furthermore, the lower edge of the adhesive film overlaps and covers 1 / 4 to 1 / 3 of the upper region of the anti-pull-out line; the adhesive film covers 80%-95% of the circumference along the inner wall of the cap.

[0011] Furthermore, the pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive with an initial tack of ≥15N / 25mm; the dual-temperature zone thermosensitive adhesive layer has an adhesion strength of ≥30N / 25mm after activation, and an adhesion strength retention rate of ≥85% in an environment of -10℃ to 50℃.

[0012] Furthermore, the surface of the thermosensitive adhesive layer of the composite film has a micron-level random coded microstructure, which is formed by molding or laser etching. After heat shrinking, the microstructure is transferred to the surface of the bottle cap neck to form a unique anti-counterfeiting mark.

[0013] Furthermore, the device includes a bottle cap and a heat-shrinkable cap, the cap being fixed to the neck of the bottle cap by an irreversible adhesive method; the lower edge of the cap has a stepped, discontinuous anti-pull line, the inner wall of which is bonded to the neck of the bottle cap by a composite adhesive film activated by a dual temperature zone, the lower edge of the adhesive film overlapping and covering the upper area of ​​the anti-pull line, and the circumferential coverage of the adhesive film leaving a gap to form an adhesive-free opening area; forcibly pulling off the cap will cause the cap to tear along the anti-pull line and / or the adhesive film to undergo cohesive damage.

[0014] The beneficial effects of this invention are: This invention offers irreversible anti-counterfeiting features: dual-temperature thermosensitive adhesive, overlapping coverage, and gradient breakpoints ensure that forced removal will inevitably damage the device, leaving no non-destructive path. It boasts high process tolerance, dual-temperature activation, compatibility with existing heat shrink tubing, and requires no equipment modification. It is user-friendly with a glue-free handle and gradient anti-pull-out lines, requiring only 6-10N of opening force, allowing for easy opening by hand. It exhibits strong environmental adaptability, maintaining ≥85% strength retention at temperatures ranging from -10℃ to 50℃. Furthermore, it is cost-effective, with material cost increases of ≤5%, making it suitable for mass production. The combination of features such as stepped anti-pull-out lines, dual-temperature adhesive film, and overlapping coverage creates a synergistic effect of "1+1>2," rather than a simple additive effect. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the method flow of the present invention; Figure 2 Schematic diagram of a double-sided adhesive film covering a wire-resistant anti-pull-out structure; Figure 3 This is a schematic diagram of a double-sided adhesive film-covered anti-pull-out wire structure. Detailed Implementation

[0016] The modified EVA irreversible thermosensitive adhesive described in this invention is model EVA-T80.

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0018] Example 1; like Figure 1 As shown, an adhesive method for preventing cap detachment is used for sealing 500ml liquor bottle caps. The steps are as follows: Step 1: Cap Pre-treatment: Select 0.045mm thick PVC heat-shrink caps and use laser die-cutting technology to process a stepped, discontinuous anti-pull-out line along the circumference of the lower edge of the cap. The overall height of the anti-pull-out line is 6mm. The break point length is 1.5mm, and the spacing between adjacent break points is 0.8mm. The break point depth gradually changes linearly along the circumference: at the position corresponding to the preset 10% circumference un-adhesive opening area, the break point depth is 0.4mm (deepest); as it moves away from the opening area, the depth gradually decreases, reaching a minimum of 0.2mm at the closed end. During processing, ensure that the anti-pull-out line avoids the anti-counterfeiting mark in the center of the cap; Step Two: Composite Film Preparation and Bonding: A three-layer co-extrusion composite process is used. The acrylic pressure-sensitive adhesive has a coating thickness of 0.015mm and an initial tack of ≥16N / 25mm. The heat-sensitive adhesive layer is a dual-temperature zone modified EVA irreversible heat-sensitive adhesive (purchased from Dongguan Xinli Adhesive Co., Ltd., model EVA-T80) with a coating thickness of 0.05mm. This adhesive layer has a phase separation structure, forming two activation temperature zones: a low-temperature activation layer (52±2℃) and a high-temperature activation layer (62±2℃). The total film thickness is 0.08mm. Bonding: The composite film is cut into strips with a height of 7mm and a circumference of 90% of the bottle cap neck circumference. These strips are then bonded to the inner wall of the cap at the position corresponding to the bottle cap neck. When applying the adhesive film, ensure that: the lower edge of the film extends downwards, overlapping and covering the upper part of the anti-pull-out line area by about 2mm (about 1 / 3 of the height); the film covers 90% of the circumference in the circumference, and precisely leaves 10% of the circumferential area un-adhesive, as the "adhesive-free opening area", which is aligned with the starting end of the depth gradient of the anti-pull-out line; Step 3: Heat Shrink Curing and Performance Testing: Heat Shrink: The prepared cap is fitted onto the bottle cap and sent into a hot air shrink tunnel. The hot air temperature is set to 65℃, and the dwell time in the tunnel is 4 seconds. During this process, the cap shrinks due to heat, and the dual-temperature zone thermosensitive adhesive of the composite film is activated: first, the 52℃ low-temperature zone provides initial positioning to prevent the cap from shifting; then, the 62℃ high-temperature zone fully melts and flows, wetting the micro-textures on the bottle cap surface, and the inverted tooth-shaped protrusions are embedded accordingly. Subsequently, it cools and cures, forming a strong "anchoring" effect and chemical adhesion.

[0019] Pull-out force test: Vertical pull-out was performed using an electronic tensile testing machine, and the maximum force was measured to be 42N. Observation of the failure interface showed that the cap was irregularly torn along the anti-pull-out line, and large-area cohesive failure occurred inside the film. Residual glue was found on both the cap and the inner wall of the cap, proving that the failure was irreversible. Opening force test: Hold the non-adhesive opening area with your finger and tear along the anti-pull line. The opening force was measured to be 8N. It opens smoothly and requires no tools.

[0020] Environmental adaptability test: The packaged samples were placed in a -10℃ refrigerator and a 50℃ oven for 48 hours respectively. After being taken out and restored to room temperature, a pull-out test was performed. The adhesive strength retention rates were 87% and 89% respectively, both higher than 85%.

[0021] Anti-transfer test: When the adhesive layer was locally heated to 80°C with a heat gun, it softened, but when forcibly pulled off, the cap still tore from the weak anti-pull line, and the adhesive layer was cohesively destroyed and could not be transferred completely.

[0022] The common methods currently include: Comparative Example 1: Figure 2As shown, traditional single-layer hot melt adhesive film bonding: using the same PVC heat-shrinkable cap as in Example 1, but without processing the anti-pull-out line, and using commercially available single-layer EVA hot melt adhesive film (thickness 0.5mm, activation temperature 65℃), without a layered structure. The adhesive film is completely pasted onto the inner wall of the cap corresponding to the neck position of the bottle cap. After capping, it is heat-shrinked with 65℃ hot air for 4 seconds. The test results are as follows: Pull-out force at room temperature: 25N. After pull-out, the cap remains intact, the film is completely separated from the cap, and it can be peeled off completely; Anti-pull-out performance: Poor. After locally heating the neck of the cap to 70℃ with a heat gun, the adhesive layer softens, and the cap can be easily and without damage; Normal opening force: Due to the lack of anti-pull-out lines and adhesive-free areas, it requires a blade to cut open, making it inconvenient to open; Cap integrity: Can be completely recycled, making it easy to use for counterfeiting.

[0023] Comparative Example 2: Figure 3 As shown, a single-temperature zone thermosensitive adhesive film + conventional anti-pull-out line is used: the same PVC heat-shrinkable cap as in Example 1 is used, with conventional anti-pull-out lines of uniform depth (uniform breakpoint depth of 0.3mm, overall height of 6mm) processed on the lower edge. The same composite adhesive film as in Example 1 is used, but the thermosensitive adhesive layer is a single-temperature zone (activation temperature 62℃), without a dual-temperature layer design. The lower edge of the adhesive film is aligned with the upper end of the anti-pull-out line without overlapping. After the cap is applied, it is heat-shrinked with 62℃ hot air for 4 seconds. The test results were as follows: Pull-out force at room temperature: 35N. However, during the pull-out process, the adhesive interface between the film and the cap was damaged first. Although the cap tore along the anti-pull line, some areas could still be peeled off, failing to guarantee "irreversible" damage; process tolerance: poor. When the heat shrinking temperature fluctuated to 58℃, the adhesive layer was insufficiently activated, and the pull-out force dropped to 20N; when the temperature fluctuated to 68℃, the adhesive layer over-melted, resulting in glue overflow and affecting the appearance; anti-pry performance: because the film did not cover the anti-pull line, a pry tool could be inserted through the gap in the anti-pull line, expanding the tearing range and ultimately separating the cap from the film completely.

[0024] The specific comparison is shown in the table below:

[0025] Example 2; An adhesive bonding method for preventing the caps from being pulled off, suitable for sealing anti-counterfeiting caps on cork stoppers of high-end wine bottles, includes the following steps: Step 1: Cap pretreatment. Select 0.05mm thick POF heat shrink caps. Anti-pull-out wire processing: Use a cold-knife semi-break process to process a stepped, discontinuous anti-pull-out wire. Break length 1.0mm, spacing 0.5mm. Break depth near the opening area 0.3mm, away from the opening area 0.1mm, overall height 5mm; Step 2: Composite film preparation and bonding: The composite film uses a flexible PET substrate, with an initial tack of 15N / 25mm for the acrylic pressure-sensitive adhesive; the dual-temperature zone modified EVA thermosensitive adhesive has a low-temperature activation temperature of 55℃ and a high-temperature activation temperature of 63℃. Adhesive film: The structure is the same as in Example 1, but the thickness is adjusted to 0.045 mm (0.01 mm for PET substrate, 0.01 mm for pressure-sensitive adhesive, and 0.025 mm for thermosensitive adhesive). The height of the raised dots on the thermosensitive adhesive surface is 0.1 mm. The low-temperature activation temperature is 55°C, and the high-temperature activation temperature is 63°C. Application: The adhesive film is 6mm high, with the lower edge overlapping the top of the anti-pull-out line by 1.5mm (approximately 1 / 4 of the height). It covers 95% of the circumference, leaving a 5% unadhesive opening area.

[0026] Step 3: Heat shrink curing and performance testing; Heat shrink: hot air temperature 60℃, time 3 seconds.

[0027] Performance testing: Pull-out force: 36N, failure mode is cap tearing and cohesive failure of the adhesive layer; opening force: 7N, damp heat aging test (40℃, 90%RH, 48h): adhesive strength retention rate 86%; due to the softer POF material, after heat shrinking, it fits the wine bottle cork cap very well and does not affect the air permeability of the cork.

[0028] Example 3; An adhesive bonding method for preventing cap detachment, suitable for sealing anti-counterfeiting caps on large-capacity health product bottles, comprises the following steps: Step 1: Cap Pre-treatment: Select 0.06mm thick PET heat-shrink caps to meet higher strength and sealing requirements; Anti-pull-out processing: Use laser die-cutting with a break length of 2.0mm and a spacing of 1.0mm. The break depth is 0.5mm near the opening area and 0.2mm away from the opening area, with an overall height of 7mm; Step 2: Adhesive Film: The structure is the same as in Example 1, but the thickness is increased to 0.1mm (PET substrate 0.02mm, pressure-sensitive adhesive 0.02mm, thermosensitive adhesive 0.06mm). The height of the raised dots on the thermosensitive adhesive surface is 0.2mm. Low-temperature activation temperature is 54℃, and high-temperature activation temperature is 65℃. Application: The adhesive film height is 8mm, with the lower edge overlapping and covering the upper end of the anti-pull-out line by 2.5mm (approximately 1 / 3 of the height), covering 90% of the circumference, leaving a 10% unadhesive opening area. In the unadhesive opening area, an additional small semi-circular protrusion is die-cut as a more noticeable easy-to-fold handle. Step 3: Heat shrink curing and performance testing: Heat shrink: hot air temperature 70℃, time 5 seconds.

[0029] Performance Testing: Pull-out force: 46N. Complete destruction. Opening force: 9N. Thanks to the handle design, opening is equally convenient. High and low temperature cycle test: -10℃ 2h → 25℃ 2h → 50℃ 2h, 5 cycles: no significant decrease in adhesive strength, meeting the stringent environmental requirements for health products during transportation and storage.

[0030] Sealing performance test: The positive pressure test showed that the sealing performance between the cap and the bottle mouth was improved by about 15% compared with traditional rubber caps, thanks to the filling and strong adhesion of the adhesive film.

[0031] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A bonding method for preventing the pull-out of rubber caps, characterized in that, Includes the following steps: Step 1: Form a circumferential anti-pull-out line at the lower edge of a heat-shrinkable cap; Step 2: Adhere a composite double-sided adhesive film to the inner wall of the cap at the position corresponding to the neck of the bottle cap; the adhesive film includes a pressure-sensitive adhesive layer and a dual-temperature zone activated irreversible heat-sensitive adhesive layer from top to bottom; Step 3: Place the cap with the adhesive film onto the neck of the bottle cap and perform heat shrink treatment to shrink the cap and adhere it to the neck of the bottle cap. After cooling, an irreversible bond is formed. The bonding of the pressure-sensitive adhesive layer and the cap is completed simultaneously during the cap forming stage.

2. The bonding method for preventing the cap from pulling off according to claim 1, characterized in that, The anti-pull-out line is a stepped discontinuous anti-pull-out line, which is composed of breakpoints with gradually changing depth. The breakpoint depth of the stepped discontinuous anti-pull-out line gradually changes linearly along the circumference. The breakpoint depth near the glue-free opening area is 0.3-0.5mm, and the breakpoint depth far from the glue-free opening area is 0.1-0.2mm.

3. The bonding method for preventing the cap from pulling off according to claim 1, characterized in that, The lower edge of the adhesive film extends downward and overlaps the upper area of ​​the anti-pull-out line, and the adhesive film covers a portion of the area circumferentially along the inner wall of the cap, leaving a no-adhesive opening area. The dual-temperature zone activated irreversible heat-sensitive adhesive layer includes: a low-temperature activation layer activated at 50-55℃ for pre-positioning during the heat shrinking process; and a high-temperature activation layer activated at 60-65℃ for providing final irreversible strong adhesion.

4. The bonding method for preventing the cap from pulling off according to claim 1, characterized in that, The adhesive film can cover the anti-pull-out wire area, the upper part of the anti-pull-out wire area, and the lower part of the anti-pull-out wire area.

5. The bonding method for preventing the cap from pulling off according to claim 4, characterized in that, The lower edge of the adhesive film overlaps and covers 1 / 4 to 1 / 3 of the upper region of the anti-pull-out line; the adhesive film covers 80%-95% of the circumference along the inner wall of the cap.

6. The bonding method for preventing the cap from pulling off according to claim 1, characterized in that, The pressure-sensitive adhesive layer is an acrylic pressure-sensitive adhesive with an initial tack of ≥15N / 25mm; the dual-temperature zone thermosensitive adhesive layer has an activation bond strength of ≥30N / 25mm and a bond strength retention rate of ≥85% in an environment of -10℃ to 50℃.

7. The bonding method for preventing the cap from pulling off according to claim 1, characterized in that, The glue-free opening area is equipped with an easy-break handle structure, and its normal opening force is 6-10N.

8. The bonding method for preventing the cap from pulling off according to claim 1, characterized in that, The surface of the thermosensitive adhesive layer of the composite film has a micron-level randomly encoded microstructure. After heat shrinking, the microstructure is transferred to the surface of the bottle cap neck to form a unique anti-counterfeiting mark.

9. A type of anti-counterfeiting plastic cap, characterized in that, The device includes a bottle cap and a heat-shrinkable cap, the cap being fixed to the neck of the bottle cap by an irreversible adhesive method; the lower edge of the cap has a stepped, discontinuous anti-pull line, the inner wall of which is bonded to the neck of the bottle cap by a composite adhesive film activated by dual temperature zones, the lower edge of the adhesive film overlapping and covering the upper area of ​​the anti-pull line, and the circumferential coverage of the adhesive film leaving a gap to form an adhesive-free opening area; forcibly pulling off the cap will cause the cap to tear along the anti-pull line and / or the adhesive film to undergo cohesive damage.

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