In-mold label film capable of preventing label connection and easily exhausting as well as preparation method and application of in-mold label film

Abstract

The invention relates to an anti-label-connection easy-exhaust in-mold label film as well as a preparation method and application thereof, and belongs to the technical field of in-mold labels. The in-mold label film capable of preventing label connection and exhausting air easily comprises a surface layer, a supporting layer, an attaching layer and a coarsening bonding layer which are arranged in sequence, the laminating layer is prepared from one of an ethylene-alpha-olefin copolymer, a propylene-alpha-olefin copolymer and a maleic anhydride grafted propylene-alpha-olefin copolymer; and the coarsening bonding layer and the bonding layer have the same raw material composition. After the in-mold label film capable of preventing label connection and easily exhausting is prepared into in-mold labels by adopting a specific method, the in-mold labels can be prevented from being connected due to overlarge contact area between the in-mold labels (namely label connection prevention); and meanwhile, the probability that bubbles appear between the in-mold label and the plastic part after the in-mold label is used for in-mold labeling is reduced (namely, exhaust is easy).

Description

Technical Field

[0001] The invention relates to the technical field of in-mold labels, and in particular to an anti-linked label and easy-to-exhaust in-mold label film, and a preparation method and application thereof. Background Art

[0002] The in-mold labeling process generally refers to the process of using the pressure during molding and the residual temperature of the plastic parts to fuse the in-mold label placed in the mold with the plastic parts during molding, forming a process in which the in-mold label and the plastic parts are integrally molded.

[0003] At present, the preparation process of in-mold labels is as follows: printing is performed on an in-mold label film, and then it is die-cut into several in-mold labels, and several in-mold labels are stacked. When performing in-mold labeling, a single in-mold label is taken out from the stacked in-mold labels, and it is placed and fixed inside the mold cavity of the mold. When the plastic part is formed in the mold, the in-mold label will be fused with the plastic part, thus completing the in-mold labeling process.

[0004] However, due to some defects of the existing in-mold label film, the in-mold labels made of the existing in-mold label film may have some problems during the in-mold labeling process.

[0005] Since the materials used in the laminating layer of the existing in-mold label film have strong low-temperature adhesion, after the existing in-mold label film is made into an in-mold label, two adjacent in-mold labels in a stack of in-mold labels are prone to adhesion, resulting in the phenomenon of continuous labels when a single in-mold label is taken out from the stack of in-mold labels, that is, 2 or 3 in-mold labels are taken out at a time. In addition, since the laminating layer surface of the existing in-mold label film is smooth, after the in-mold label is made and used for in-mold labeling, there is a problem that it is difficult to vent the laminating layer of the in-mold label and the plastic part after laminating, resulting in abnormal bubbles (i.e., there are many bubbles) between the laminating layer of the in-mold label and the plastic part, affecting the yield rate of in-mold labeling. Summary of the invention

[0006] Based on this, the purpose of the present invention is to provide an anti-connected and easy-to-degassing in-mold label film and its preparation method and application. The anti-connected and easy-to-degassing in-mold label film prepared by the present invention using a specific method can prevent the in-mold labels from connecting due to excessive contact area between the in-mold labels (i.e., anti-connected labels), and at the same time reduce the probability of bubbles appearing between the in-mold label and the plastic part after the in-mold label is used for in-mold labeling (i.e., easy to degass).

[0007] To achieve the above object, the present invention adopts the following technical solutions: The first object of the present invention is to provide a preparation method of an anti - sticking and easy - exhaust in - mold label film. The anti - sticking and easy - exhaust in - mold label film comprises a surface layer, a support layer, an adhesion layer and a roughened adhesion layer arranged in sequence; the adhesion layer is composed of one of ethylene - α - olefin copolymer, propylene - α - olefin copolymer, and maleic anhydride - grafted propylene - α - olefin copolymer; the roughened adhesion layer has the same raw material composition as the adhesion layer; the preparation method of the anti - sticking and easy - exhaust in - mold label film comprises the following steps: Grind the raw materials of the roughened adhesion layer into a powder form to obtain the roughened adhesion layer powder. Through the high - voltage tip - discharge process, the surface of the roughened adhesion layer powder is given an electrostatic charge of - / + (25 - 30) KV for standby (this step can be completed before the roughening treatment process, and there is no sequence limitation). Respectively feed the raw materials of the surface layer, the support layer, and the adhesion layer into the extruders corresponding to each layer, and form a cast sheet through the extrusion - casting process. The cast sheet is formed into a thick sheet through the longitudinal stretching process. The thick sheet undergoes a roughening treatment process: making the roughened adhesion layer powder adsorb and weld on the surface of the adhesion layer of the thick sheet to form a roughened treatment thick sheet. The roughened treatment thick sheet undergoes a transverse stretching process, a traction - thickness measurement - corona - winding process to obtain a film semi - finished product. The film semi - finished product undergoes an aging - slitting process to obtain a film finished product, that is, the anti - sticking and easy - exhaust in - mold label film.

[0008] In the preparation method of the anti - sticking and easy - exhaust in - mold label film of the present invention, after the raw materials of the surface layer, the support layer, and the adhesion layer are melted by the extruder respectively, they are co - extruded and rapidly cooled into a cast sheet with a three - layer laminated structure (i.e., surface layer - support layer - adhesion layer) integrated in the extrusion - casting process. After the cast sheet undergoes the longitudinal stretching process, a thick sheet with a longitudinally stretched three - layer laminated structure is obtained. In the present invention, the raw materials of the roughened adhesion layer are ground into a powder form of the roughened adhesion layer powder in advance. Through the high - voltage tip - discharge process, the surface of the roughened adhesion layer powder is given an electrostatic charge of - / + (25 - 30) KV. In the roughening treatment process, by using the electrostatic charge on the surface of the roughened adhesion layer powder, the roughened adhesion layer powder is adsorbed onto the surface of the adhesion layer of the thick sheet and welded together to form a roughened treatment thick sheet together with the thick sheet; wherein, the roughened adhesion layer powder on the roughened treatment thick sheet is closely packed together. Then, after the roughened treatment thick sheet first undergoes the transverse stretching process, the gaps between the roughened adhesion layer powders change from close packing to a well - arranged state, and at the same time, the roughened adhesion layer powder is further welded to the adhesion layer, so that the protruding height of the roughened adhesion layer powder on the surface of the adhesion layer is further reduced. Then, it undergoes a traction - thickness measurement - corona - winding process to obtain a film semi - finished product. The film semi - finished product undergoes an aging - slitting process to obtain a film finished product, that is, the anti - sticking and easy - exhaust in - mold label film.

[0009] The bonding layer of the present invention is composed of one of ethylene-α-olefin copolymer, propylene-α-olefin copolymer, and maleic anhydride grafted propylene-α-olefin copolymer; the raw materials of the roughened bonding layer are the same as those of the bonding layer. This design is beneficial for the roughened bonding layer powder to be welded to the bonding layer and not easily fall off. In addition, in the present invention, through the roughening treatment process, the roughened bonding layer powder is adsorbed and tightly packed on the surface of the bonding layer. After the transverse stretching process, the gaps between the roughened bonding layer powders change from tight packing to a well-arranged pattern, and finally a roughened bonding layer with uneven surface texture is formed on the surface of the bonding layer. When the label film in the anti-sticking and easy-exhaust in-mold label is printed on the surface of the surface layer and several in-mold labels are obtained through die-cutting and stacking processes, due to the formation of a roughened bonding layer with uneven surface texture on the surface of the bonding layer, the contact area between the in-mold labels will not be too large, avoiding the occurrence of the phenomenon of in-mold label sticking together due to too large contact area between the in-mold labels. When taking out a single in-mold label from a stack of in-mold labels during in-mold labeling, the single in-mold label can be taken out smoothly without the phenomenon of label sticking, that is, 2 or 3 in-mold labels will not be taken out, avoiding putting 2 or 3 in-mold labels into the mold and affecting in-mold labeling. In addition, during in-mold labeling of the in-mold label, due to the formation of a roughened bonding layer with uneven surface texture on the surface of the bonding layer, that is, the surface topography of the in-mold label is rough, open gas paths are formed between the uneven surface textures to facilitate gas discharge. When the in-mold label is attached to the plastic part, the open gas paths can exhaust gas in time without generating the phenomenon of gas accumulation to form bubbles (no abnormal bubble phenomenon), greatly reducing the probability of bubbles appearing between the in-mold label and the plastic part.

[0010] In the preparation method of the anti-sticking and easy-exhaust in-mold label film of the present invention, the surface of the roughened bonding layer powder is obtained with static electricity of - / + (25 - 30) KV through the high-voltage tip discharge process. In the roughening treatment process, by using the static electricity on the surface of the roughened bonding layer powder, the roughened bonding layer powder can be adsorbed and tightly packed on the surface of the thick bonding layer, so that after the subsequent transverse stretching process, the gaps between the roughened bonding layer powders change from tight packing to a well-arranged pattern to form uneven surface texture. If the static electricity value obtained on the surface of the roughened bonding layer powder is lower than 25 KV, the static adsorption force between the roughened bonding layer powder and the thick bonding layer of the sheet is too low, resulting in the roughened bonding layer powder not being fully adsorbed and tightly packed on the surface of the thick bonding layer of the sheet, resulting in a decrease in the roughness of the prepared anti-sticking and easy-exhaust in-mold label film and a deviation in the exhaust effect. Using the in-mold label made for in-mold labeling will reduce the in-mold labeling yield; if the static electricity value obtained on the surface of the roughened bonding layer powder exceeds 30 KV, there will be a risk of static electricity injury during the film preparation process, causing a safety hazard.

[0011] As a preferred solution, the roughening treatment process includes the following steps: on the surface of the bonding layer of the thick sheet, through the high-voltage tip discharge process, the surface of the bonding layer of the thick sheet obtains static electricity of + / -(25 - 30) KV; using the mechanism of attraction between positive and negative charges, a layer of roughening bonding layer powder is adsorbed on the surface of the bonding layer of the thick sheet, and using the residual heat of the thick sheet after the longitudinal stretching process, the roughening bonding layer powder is welded together with the bonding layer of the thick sheet to form the roughened thick sheet. In the present invention, before the roughening treatment process, the surface of the roughening bonding layer powder obtains static electricity of - / +(25 - 30) KV through the high-voltage tip discharge process, and in the roughening treatment process, the surface of the bonding layer of the thick sheet obtains static electricity of + / -(25 - 30) KV through the high-voltage tip discharge process. When the above-mentioned thick sheet passes through the above-mentioned roughening bonding layer powder, using the mechanism of attraction between positive and negative charges, the surface of the bonding layer of the thick sheet adsorbs and tightly accumulates to form a layer of roughening bonding layer powder by neutralizing charges. At the same time, due to the relatively high residual heat on the surface of the bonding layer of the thick sheet after the longitudinal stretching process (it is well-known to those skilled in the art that the surface of the bonding layer of the thick sheet obtained after the longitudinal stretching process will have relatively high residual heat, and the residual heat is generally 105 - 110 °C, while the melting points of the ethylene-α-olefin copolymer, propylene-α-olefin copolymer, and maleic anhydride-grafted propylene-α-olefin copolymer used for the roughening bonding layer are 70 - 100 °C), using the residual heat on the surface of the bonding layer of the thick sheet, the roughening bonding layer powder is welded together with the bonding layer of the thick sheet, so that the roughening bonding layer powder is difficult to fall off and prevent failure, and a roughening bonding layer is formed on the surface of the bonding layer of the thick sheet, which is manifested as uneven surface texture, and together with the thick sheet, it forms a roughened thick sheet.

[0012] As a preferred solution, in the transverse stretching process, the transverse stretching ratio is 4 - 10, preferably 8 - 10. The roughening bonding layer powder on the roughened thick sheet obtained after the roughening treatment process is tightly packed together. By controlling the transverse stretching by 4 - 10 times (preferably 8 - 10 times) in the transverse stretching process, the gap between the roughening bonding layer powders can be changed from tight packing to a well-arranged state, which is beneficial to gas discharge during in-mold labeling.

[0013] As a preferred solution, after the longitudinal stretching process, the temperature of the surface of the bonding layer of the thick sheet is 105 - 110 °C. In the present invention, by controlling the longitudinal stretching process, the temperature of the surface of the bonding layer of the thick sheet reaches 105 - 110 °C, so that in the roughening treatment process, after the roughening bonding layer powder is adsorbed on the surface of the bonding layer of the thick sheet, the roughening bonding layer powder (with a melting point of 70 - 100 °C) can be welded together with the bonding layer of the thick sheet through the residual heat on the surface of the bonding layer of the thick sheet.

[0014] As a preferred embodiment, the method for preparing the roughened adhesive layer powder is as follows: The raw materials of the roughened adhesive layer (in the form of resin particles with an average particle size of 4 - 5 mm) are cooled with liquid nitrogen and then placed in a grinder for grinding. Then, they are sieved by a sieve shaker into powder with an average particle size of 40 - 60 µm, thus obtaining the roughened adhesive layer powder. By making the raw materials of the roughened adhesive layer into roughened adhesive layer powder with an average particle size of 40 - 60 µm, it is convenient for the roughened adhesive layer powder to be effectively adsorbed on the surface of the bonding layer under the action of electrostatic adsorption force during the roughening process. Additionally, after the thick sheet undergoes the transverse stretching process in the roughening process, the protruding height of the roughened adhesive layer on the surface of the bonding layer will decrease from 40 - 60 µm to 4 - 6 µm. Preferably, the average particle size of the roughened adhesive layer powder is 50 µm.

[0015] As a preferred embodiment, after obtaining the roughened adhesive layer powder, the roughened adhesive layer powder is placed in a powder tank, and then a high-voltage tip discharge process is performed on the roughened adhesive layer powder in the powder tank to make the surface of the roughened adhesive layer powder in the powder tank obtain an electrostatic charge of - / + (25 - 30) KV.

[0016] As a preferred embodiment, in the roughening process, after the surface of the bonding layer of the thick sheet obtains an electrostatic charge of + / -(25 - 30) KV, the thick sheet is passed through the powder tank, and the distance between the bonding layer of the thick sheet and the roughened adhesive layer powder in the powder tank is 10 - 20 mm. In this way, by controlling the distance between the bonding layer of the thick sheet and the roughened adhesive layer powder in the powder tank to be 10 - 20 mm, a layer of roughened adhesive layer powder can be quickly and effectively adsorbed on the surface of the bonding layer of the thick sheet, and the roughened adhesive layer powder is tightly packed on the surface of the bonding layer.

[0017] As a preferred embodiment, the content of α-olefin in the ethylene-α-olefin copolymer is 10 - 30 wt%, and the α-olefin in the ethylene-α-olefin copolymer is at least one of butene, hexene, and octene.

[0018] As a preferred embodiment, the melting point of the ethylene-α-olefin copolymer is 70 - 100 °C, and the melt index is 1 - 8 g / 10 min (190 °C, 2.16 kg).

[0019] As a preferred embodiment, the content of α-olefin in the propylene-α-olefin copolymer is 4 - 15 wt%, and the α-olefin in the propylene-α-olefin copolymer is at least one of ethylene, butene, and hexene.

[0020] As a preferred embodiment, the melting point of the propylene-α-olefin copolymer is 70 - 100 °C, and the melt index is 1 - 8 g / 10 min (230 °C, 2.16 kg).

[0021] As a preferred solution, the maleic anhydride grafting rate in the maleic anhydride grafted propylene-α-olefin copolymer is 0.8-1.3 wt%, the content of α-olefin in the maleic anhydride grafted propylene-α-olefin copolymer is 4-15 wt%, and the α-olefin in the maleic anhydride grafted propylene-α-olefin copolymer is at least one of ethylene, butene, and hexene.

[0022] As a preferred solution, the melting point of the maleic anhydride grafted propylene-α-olefin copolymer is 70-100 °C, and the melt index is 1-8 g / 10 min (230 °C, 2.16 kg).

[0023] As a preferred solution, the surface layer comprises homopolypropylene and 0.3-1.5 wt% of an anti-blocking agent. The surface layer is used for surface printing, and ink can be printed on the surface of the surface layer to form a printed layer. Additionally, by adding an anti-blocking agent to the surface layer, the anti-blocking effect of the surface layer can be improved to prevent film blocking.

[0024] As a preferred solution, the anti-blocking agent is at least one of silica and polymethyl methacrylate, and the average particle size of the anti-blocking agent is 4-5 µm.

[0025] As a preferred solution, the support layer comprises homopolypropylene, 0-30 wt% of calcium carbonate, 5-30 wt% of titanium dioxide, and 0.4-1.5 wt% of an antistatic agent.

[0026] As a preferred solution, in the support layer, the calcium carbonate is heavy calcium carbonate, and (after grinding) the average particle size of the calcium carbonate is 1-2 µm.

[0027] As a preferred solution, in the support layer, the titanium dioxide is rutile titanium dioxide synthesized by the chloride process, and the average particle size of the titanium dioxide is 0.2-0.4 µm.

[0028] As a preferred solution, in the support layer, the antistatic agent is at least one of glycerol monostearate, ethoxylated alkanolamine, N,N-dihydroxyethyl lauramide, ethoxylated alcohol, alkyl sulfonate, alkyl phosphate, tetraalkyl quaternary ammonium salt, trialkyl benzyl quaternary ammonium salt, and alkyl betaine.

[0029] As a preferred solution, the melt index of the homopolypropylene in the surface layer and the support layer is 2.8-3.2 g / 10 min (230 °C, 2.16 kg), the isotacticity is 95-97%, and the melting point is 160-168 °C.

[0030] Another object of the present invention is to provide an anti-blocking and easy-to-exhaust in-mold label film prepared by the preparation method described in any one of the above.

[0031] Another object of the present invention is to provide an application of an anti - label - sticking and easy - exhaust in - mold label film in in - mold labeling: after making the anti - label - sticking and easy - exhaust in - mold label film into an in - mold label, the in - mold label and a plastic part are integrated through in - mold labeling to form a plastic part with an in - mold label.

[0032] Specifically, the application of the anti - label - sticking and easy - exhaust in - mold label film of the present invention in in - mold labeling: after the anti - label - sticking and easy - exhaust in - mold label film undergoes processes such as surface printing (printing methods such as flexographic printing, offset printing, and rotary printing), die - cutting, stacking, etc., a number of stacked in - mold labels (for example: 500 labels per stack) are obtained (each in - mold label includes a printing layer, a surface layer, a support layer, an adhesion layer, and a roughened adhesion layer arranged in sequence); a manipulator is used to grab a single in - mold label and place it into a mold to form a mold with an in - mold label; through a blow - molding process, an injection - blow - molding process, or a thermoforming process (also known as a thermoforming process), plastic resin (raw material) is formed into a plastic preform or a thermoformed sheet and placed in the above - mentioned mold with an in - mold label for in - mold labeling, so that the roughened adhesion layer of the in - mold label is welded together with the plastic preform or the thermoformed sheet, and finally, after cooling, the in - mold label and the plastic part are integrated to form a plastic part with an in - mold label.

[0033] As a preferred embodiment of the present invention, when the adhesion layer is composed of an ethylene - α - olefin copolymer, the plastic part is preferably a polyethylene plastic part; when the adhesion layer is composed of a propylene - α - olefin copolymer, the plastic part is preferably a polypropylene plastic part; when the adhesion layer is composed of a maleic anhydride - grafted propylene - α - olefin copolymer, the plastic part is preferably a polyester plastic part (for example: polyethylene terephthalate plastic part, polycarbonate plastic part) or a polyamide plastic part.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) One of the innovative points of the present invention is that, based on the fact that the thermal composite material used in the bonding layer of the existing in-mold label film has strong low-temperature adhesiveness, and the in-mold labels produced are prone to the phenomenon of label connection. In addition, although the off-line embossing process in the prior art can emboss the surface of the bonding layer of the existing in-mold label film to reduce the occurrence of label connection, this operation will cause excessive losses of corresponding labor, energy, and materials, and requires the addition of embossing equipment, resulting in increased costs. The preparation method of the anti-label-connection and easy-exhaust in-mold label film of the present invention, through a specific roughening treatment process, enables the roughened adhesive layer powder to adsorb and closely accumulate on the surface of the bonding layer. After the transverse stretching process, the gaps between the roughened adhesive layer powders change from close packing to a well-arranged state, so that a roughened adhesive layer with an uneven surface texture is formed on the surface of the bonding layer of the prepared anti-label-connection and easy-exhaust in-mold label film. After the anti-label-connection and easy-exhaust in-mold label film is made into an in-mold label, the effective contact area between the in-mold labels can be greatly reduced, thereby avoiding label connection of the in-mold labels, saving labor, energy, and materials in the off-line embossing process, and eliminating the need to add embossing equipment, thus saving costs.

[0035] (2) Another innovative point of the present invention is that a roughened adhesive layer with an uneven surface texture is formed on the surface of the bonding layer of the anti-label-connection and easy-exhaust in-mold label film of the present invention, and open air channels are formed between the uneven surface textures for gas discharge. When the in-mold label is attached to the plastic part, the open air channels can exhaust gas in a timely manner without generating the phenomenon of gas accumulation to form bubbles (no abnormal bubble phenomenon), greatly reducing the probability of bubbles appearing between the in-mold label and the plastic part, thereby improving the yield of in-mold labeling.

[0036] (3) The third innovative point of the present invention is that based on the fact that the traditional off-line embossing process will cause sharp embossing peaks to be formed on the surface of the bonding layer, and the in-mold label film usually needs to be printed with ink during the process of being made into an in-mold label, and the printed ink often has a post-curing process, making the printed layer relatively soft. During the stacking or winding process of the in-mold labels, the sharp embossing peaks on the surface of the bonding layer will adhere to the printed layer, resulting in the transfer of the embossing peaks to the surface of the printed layer, affecting the printing appearance. In the preparation method of the anti-label-connection and easy-exhaust in-mold label film of the present invention, after the thick sheet after roughening treatment is transversely stretched, the roughened adhesive layer powder is affected by the transverse stretching temperature (usually 155 - 175 °C), and the protruding height will be further reduced, and it will change from an amorphous morphology to an elliptical spherical morphology. This elliptical spherical morphology does not have sharpness. When the anti-label-connection and easy-exhaust in-mold label film is printed into an in-mold label, during the stacking or winding process, the morphology will not be transferred to the printed layer, avoiding affecting the printing appearance.

[0037] (4)The fourth innovation point of the present invention is that after the anti - label - connecting and easy - exhaust in - mold label film based on the present invention is made into an in - mold label, the roughened adhesive layer can effectively reduce the contact area with the printing layer. Based on the material used for the roughened adhesive layer and the laminating layer having low - temperature bonding performance, the contact area is avoided from being too large during the die - cutting and stacking processes, significantly reducing the friction coefficient, thereby reducing the generation of static electricity (if the contact area is too large, additional static electricity will be generated, increasing the risk of label connection between stacked in - mold labels).

[0038] For better understanding and implementation, the present invention will be described in detail below with reference to the accompanying drawings. Brief Description of the Drawings

[0039] Figure 1 is a schematic structural diagram of an anti - label - connecting and easy - exhaust in - mold label film of the present invention; Figure 2 is a schematic structural diagram of the laminating layer and the roughened adhesive layer of an anti - label - connecting and easy - exhaust in - mold label of the present invention; Figure 3 is a schematic structural diagram of an in - mold label made from the anti - label - connecting and easy - exhaust in - mold label film of the present invention; Figure 4 is a process flow chart of the production of an anti - label - connecting and easy - exhaust in - mold label film of the present invention; Figure 5 is a process flow chart of the application of an anti - label - connecting and easy - exhaust in - mold label film of the present invention; In the figures: 1, surface layer; 2, support layer; 3, laminating layer; 4, roughened adhesive layer; 5, printing layer; A, raw material; B, cast sheet; C, thick sheet; D, thick sheet after roughening treatment; E, film semi - finished product; F, film finished product; G, extrusion - casting process; H, longitudinal stretching process; I, roughening treatment process; J, transverse stretching process; K, traction - thickness measurement - corona - winding process; L, aging - slitting process; M, in - mold label semi - finished product; N, in - mold label; O, plastic part with in - mold label; P, printing process; Q, die - cutting process; R, negative - pressure label feeding process; S, in - mold labeling process. Detailed Embodiments

[0040] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0041] The present invention provides an anti - label - connecting and easy - exhaust in - mold label film. Please refer to Figure 1 , which has a four - layer structure, including a surface layer 1, a support layer 2, a laminating layer 3, and a roughened adhesive layer 4 arranged in sequence.

[0042] Among them, the raw material formulas of each layer are as follows: Surface layer 1: homopolypropylene and anti - blocking agent; Support layer 2: homopolypropylene, calcium carbonate, titanium dioxide and antistatic agent; Laminating layer 3: one of ethylene-α-olefin copolymer, propylene-α-olefin copolymer, maleic anhydride grafted propylene-α-olefin copolymer; Roughened adhesive layer 4: The resin raw materials used are the same as those of the laminating layer.

[0043] In the anti-sticking and easy-exhaust in-mold label film of the present invention, please refer to Figure 2 , a roughened adhesive layer 4 with uneven surface texture is formed on the surface of the laminating layer 3, and open gas channels are formed between the uneven positions for gas discharge.

[0044] The present invention also provides a preparation method of an anti-sticking and easy-exhaust in-mold label film, please refer to Figure 4 , including the following steps: The raw materials A of the surface layer 1, support layer 2, and laminating layer 3 after screening are premixed according to the designed formula respectively, stirred evenly, and after weighing and calculating the input ratio, they are sent into the extruders corresponding to each layer, and after the extrusion-casting process G, a cast sheet B is formed; The cast sheet B is longitudinally stretched in the longitudinal stretching process H to form a thick sheet C, and after the longitudinal stretching process H, the surface temperature of the laminating layer 3 of the thick sheet C reaches 105-110 °C; The thick sheet C undergoes a roughening treatment process I: on the surface of the laminating layer 3 of the thick sheet C, through the high-voltage tip discharge process, the surface of the laminating layer 3 of the thick sheet C obtains static electricity of + / -(25-30) KV, and then the above-mentioned thick sheet C passes through a powder tank filled with roughened adhesive layer powder (the powder tank has previously obtained static electricity of - / +(25-30) KV on the surface of the roughened adhesive layer powder through the high-voltage tip discharge process, and the roughened adhesive layer powder is obtained by cooling the raw materials of the roughened adhesive layer (resin particles with an average particle size of 5 mm) with liquid nitrogen and then placing them in a grinding machine for grinding and sieving into powder with an average particle size of 50 µm), where the distance between the laminating layer of the thick sheet C and the roughened adhesive layer powder in the powder tank is 10-20 mm. Through the mechanism of attraction between positive and negative charges, the surface of the laminating layer 3 of the thick sheet C adsorbs and tightly accumulates to form a layer of roughened adhesive layer powder. At the same time, because the surface temperature of the laminating layer 3 of the thick sheet C after the longitudinal stretching process H reaches 105-110 °C, the remaining temperature on the surface of the laminating layer 3 of the thick sheet C is used to fuse with the roughened adhesive layer powder together, so that the roughened adhesive layer powder is difficult to fall off and prevent failure, and a roughened treated thick sheet D is obtained; The roughened treated thick sheet D first undergoes a transverse stretching process J. After the roughened treated thick sheet D undergoes the transverse stretching process J (the transverse stretching ratio is controlled at 8-10), the gaps between the roughened adhesive layer powders change from tight packing to a well-arranged state. In addition, due to the temperature of the transverse stretching process J, it will further fuse with the laminating layer 3 together. At the same time, the protrusion height of the roughened adhesive layer powder on the surface of the laminating layer 3 drops from 50 µm to 5 µm (refer to Figure 2), finally, a roughened adhesive layer 4 with uneven surface texture is formed on the surface of the bonding layer 3; then, through the processes of traction-thickness measurement-corona-reeling K, a film semi-finished product E is obtained. The film semi-finished product E finally undergoes the processes of aging-slitting L to obtain a film finished product F, which is the anti-sticking label and easy-exhaust in-mold label film.

[0045] The equipment used in the high-voltage tip discharge process is: an inductive discharge rod (working voltage: 0-50 KV), model: SC-1, manufacturer: Jiangxi Senmu Electronics Co., Ltd. In the preparation method of the anti-sticking label and easy-exhaust in-mold label film of the present invention, the high-voltage tip discharge voltage is: 25-30 KV. If it is lower than 25 KV, the electrostatic adsorption force is too low, resulting in the inability of the roughened adhesive layer powder to be fully adsorbed and closely packed on the surface of the bonding layer of the thick sheet, leading to a decrease in the roughness and exhaust effect of the prepared anti-sticking label and easy-exhaust in-mold label film, and a decrease in the in-mold labeling yield; through the tests of the inventor, when the discharge voltage is set at 25-30 KV, the roughened adhesive layer powder can be effectively adsorbed and closely packed on the surface of the bonding layer of the thick sheet. If it exceeds 30 KV, there will be a risk of electrostatic injury, causing a safety hazard.

[0046] The production equipment is a flat film process step-by-step biaxially stretched polypropylene production line provided by BRUECKNER Company of Germany, and a powder tank is added between the longitudinal stretching process and the transverse stretching process. The temperatures of the extruder, runner, pipeline, filter, and die head used in the above production line are controlled at 230-260 °C, the quenching temperature is controlled at 25-40 °C. The longitudinal stretching process consists of a preheating process, a stretching process, and a shaping process. The surfaces of the rollers in contact with the bonding layer in the above processes are pre-coated with a Teflon coating to avoid damage to the bonding layer caused by the processing temperature being higher than the melting point of the material used for the bonding layer; the transverse stretching process consists of a preheating process, a stretching process, a shaping process, and a cooling process; the process temperatures of the longitudinal stretching process and the transverse stretching process are controlled at 60-180 °C, the longitudinal stretching ratio is controlled at 4.0-10.0 times (preferably 4-6 times), and the transverse stretching ratio is controlled at 4.0-10.0 times (preferably 8-10 times).

[0047] The present invention also provides an application of the anti-sticking label and easy-exhaust in-mold label film in in-mold labeling. Please refer to Figure 5 ., the film finished product F first undergoes a printing process P, and the printing process P includes but is not limited to common processes such as rotary printing, offset printing, flexographic printing, etc., to obtain an in-mold label semi-finished product M. Then, it undergoes a die-cutting process Q to be cut into several in-mold labels N. The several in-mold labels N are stacked and placed on a label rack (for the structure of each in-mold label N, please refer to Figure 3 , which includes a printing layer 5, a surface layer 1, a support layer 2, a bonding layer 3, and a roughened adhesive layer 4 arranged in sequence). The single in-mold label N is sent through a negative pressure label feeding process R and an in-mold labeling process S, and finally a plastic part O with an in-mold label is obtained.

[0048] Example 1 This example provides an anti - linked label and easy - exhaust in - mold label film. Please refer to Figure 1 , which has a four - layer structure, including a surface layer 1, a support layer 2, an adhesion layer 3, and a roughened adhesive layer 4 arranged in sequence.

[0049] Among them, the raw material formulas of each layer are as follows: Surface layer 1: 99.5wt% homopolypropylene (isotacticity is 96%, density is 0.905g / cm 3 , melting point is 163℃, melt index is 3g / 10min, melt index test conditions: melting temperature is 230℃, load weight is 2.16kg) and 0.5wt% silica (average particle size is 5µm); Support layer 2: 70wt% homopolypropylene (isotacticity is 96%, density is 0.905g / cm 3 , melting point is 163℃, melt index is 3g / 10min, melt index test conditions: melting temperature is 230℃, load weight is 2.16kg), 15wt% titanium dioxide (chlorination process, rutile type, average particle size is 0.3µm), 14.5wt% calcium carbonate (heavy calcium carbonate, average particle size is 1.2µm), and 0.5wt% glycerol monostearate; Adhesion layer 3: 100wt% ethylene - octene copolymer (octene content is 18wt%, density is 0.905g / cm 3 , melting point is 97℃, melt index is 7.5g / 10min, melt index test conditions: melting temperature is 190℃, load weight is 2.16kg); Roughened adhesive layer 4: has the same raw material formula as the adhesion layer 3.

[0050] This example also provides a preparation method for the anti - linked label and easy - exhaust in - mold label film, including the following steps: (1) Grind the raw materials of the roughened adhesive layer 4 into a powder form. That is, after cooling the raw materials of the roughened adhesive layer 4 with liquid nitrogen for 30 minutes, use a grinder to grind them into a powder. After passing through a sieve shaker, obtain ethylene - octene copolymer powder with an average particle size of 50µm; Place the ethylene - octene copolymer powder in a powder tank, and then through a high - voltage tip - discharge process, make the surface of the ethylene - octene copolymer powder in the powder tank obtain an electrostatic charge of - 28KV, and set aside; (2) Please refer to Figure 4, the respective layer materials A of the selected surface layer 1, support layer 2, and bonding layer 3 are premixed according to the design formula, stirred evenly, and after calculating the input ratio by weighing, they are fed into each extruder and form a cast sheet B after the extrusion-casting process G; the cast sheet B forms a thick sheet C after the longitudinal stretching process H, and the surface temperature of the bonding layer 3 of the thick sheet C reaches 120-135°C; the thick sheet C undergoes a roughening treatment process: on the surface of the bonding layer 3 of the thick sheet C, through the high-voltage tip discharge process, the bonding layer surface of the thick sheet C obtains a static electricity of +28 KV. Then the above thick sheet passes through a powder tank, where the distance between the bonding layer of the thick sheet and the roughening adhesive layer powder in the powder tank is 10-20 mm. Through the mechanism of attracting positive and negative charges, the thick sheet adsorbs and tightly accumulates to form a layer of ethylene-octene copolymer powder. At the same time, because the surface temperature of the bonding layer of the thick sheet reaches 105-110°C after the longitudinal stretching process H, the bonding layer 3 of the thick sheet and the ethylene-octene copolymer powder are welded together by the residual heat of the thick sheet, so that the ethylene-octene copolymer is difficult to fall off and prevent failure, and a roughened thick sheet D is obtained; then after the roughened thick sheet D undergoes the transverse stretching process J, the gap between the roughening adhesive layer powders changes from tight packing to a well-arranged pattern. In addition, the ethylene-octene copolymer powder will be further welded to the bonding layer 3 of the thick sheet due to the temperature of the transverse stretching process J, and at the same time, the surface protrusion height drops from 50 µm to 5 µm, and finally a roughening adhesive layer 4 with an uneven surface texture is formed on the surface of the bonding layer 3; then through the traction-thickness measurement-corona-winding process K, a film semi-finished product E is obtained; the film semi-finished product E finally undergoes the aging-slitting process L to obtain a film finished product F.

[0051] Among them, the main production equipment is a flat film method biaxially oriented polypropylene production line provided by BRUECKNER of Germany, and a powder tank is added between the transverse stretching process and the longitudinal stretching process. The screw of the main extruder (for the support layer 2) is a single-screw extruder with a diameter of 150 mm and a length-diameter ratio of 33:1. The two auxiliary extruders (for the surface layer 1 and the bonding layer 3 respectively) are single-screw extruders with a screw diameter of 120 mm and a length-diameter ratio of 30:1. The temperature of the extruder is 250 °C for all sections except the feeding section which is 80 °C, and the temperature of the filter, the runner and the die head is 250 °C, and the quenching (casting film) temperature is 30 °C. In the longitudinal stretching process H, the corresponding temperatures of the preheating zone, the stretching zone and the shaping zone passed by the surface layer 1 are 138 °C, 130 °C and 138 °C respectively, and the corresponding temperatures of the preheating zone, the stretching zone and the shaping zone passed by the bonding layer 3 are 110 °C, 105 °C and 110 °C respectively. And the surfaces of the rollers passed by the bonding layer 3 are all treated with a Teflon coating to avoid scalding and damage to the surface of the bonding layer 3 due to the processing temperature being higher than the melting point of the material used for the bonding layer. The longitudinal stretching ratio is 5.0. In the transverse stretching process J, the corresponding temperatures of the preheating zone, the stretching zone and the shaping zone passed are 170 °C, the stretching zone is 157 °C, and the shaping zone is 175 °C. The transverse stretching ratio is 8.5, and the production speed is 300 m / min. The corona strength on the surface of the surface layer 1 is 30 W·min / m 2 .

[0052] In this embodiment, the total thickness of the anti-sticking and easy-exhausting in-mold label film is 105 μm, the thickness of the surface layer 1 is 1 μm, the thickness of the support layer 2 is 89 μm, the thickness of the bonding layer 3 is 10 μm, and the thickness of the roughened adhesive layer 4 is 5 μm.

[0053] This embodiment also provides an application process of the anti-sticking and easy-exhausting in-mold label film. Please refer to Figure 5 , the film finished product F (i.e., the anti-sticking and easy-exhausting in-mold label film) first goes through the printing process P, and the printing process P includes but is not limited to common processes such as flexographic printing, offset printing, rotary printing, etc., to obtain the in-mold label semi-finished product M. Then, it goes through the die-cutting process Q to be cut into several in-mold labels N. Stack several in-mold labels N (500 pieces per stack) and place them on the label rack (for the structure of each in-mold label N, please refer to Figure 3, including a printing layer 5, a surface layer 1, a support layer 2, an adhesion layer 3, and a roughened adhesion layer 4 arranged in sequence. Using a manipulator, a single in-mold label N is grabbed through a negative-pressure label feeding process R and placed into a mold to form a mold with an in-mold label; then, an in-mold labeling process S is carried out through a blow molding process: high-density polyethylene is melted by an extruder and extruded through an annular mold to form a plastic blank, and then the above plastic blank is placed into the above mold with an in-mold label. The plastic blank is inflated through the blow molding process, and the remaining temperature of the plastic blank fuses the roughened adhesion layers of the in-mold label together. Finally, after cooling, the in-mold label film and the plastic part are integrated into one body to form a high-density polyethylene plastic part O with an in-mold label.

[0054] Comparative Example 1 This comparative example provides an in-mold label film. Please refer to Figure 1 , including a surface layer 1, a support layer 2, and an adhesion layer 3 arranged in sequence, without a roughened adhesion layer 4. Among them, the raw material formulations of the surface layer 1, the support layer 2, and the adhesion layer 3 are the same as those in Example 1.

[0055] The preparation method of the in-mold label film in this comparative example is basically the same as the preparation method of the anti-sticking and easy-exhaust in-mold label film in Example 1, except that: the preparation method of the in-mold label film in this comparative example does not include step (1) of Example 1, and does not include the roughening treatment process I and the roughened thick sheet D in step (2) of Example 1; that is, for the preparation method of the in-mold label film in this comparative example, after obtaining the thick sheet C, the transverse stretching process J and other subsequent processes are directly carried out.

[0056] The total thickness of the in-mold label film in this comparative example is 100 μm, the thickness of the surface layer 1 is 1 μm, the thickness of the support layer 2 is 89 μm, and the thickness of the adhesion layer 3 is 10 μm.

[0057] The application process of the in-mold label film in this comparative example is the same as the application process of the anti-sticking and easy-exhaust in-mold label film in Example 1.

[0058] Comparative Example 2 This comparative example provides an in-mold label film. Please refer to Figure 1 , including a surface layer 1, a support layer 2, and an adhesion layer 3 arranged in sequence, without a roughened adhesion layer 4. Among them, the raw material formulations of the surface layer 1, the support layer 2, and the adhesion layer 3 are the same as those in Example 1.

[0059] The preparation method of the in-mold label film in this comparative example is basically the same as that of the anti-sticking and easy-exhaust in-mold label film in Example 1, except that: the preparation method of the in-mold label film in this comparative example does not contain step (1) of Example 1, and does not contain the roughening treatment process I and the thickened roughened sheet D in step (2) of Example 1; that is, in the preparation method of the in-mold label film in this comparative example, after obtaining the thickened sheet C, the transverse stretching process J and other subsequent processes are directly carried out; in addition, during the preparation process, in order to increase the roughening of the bonding layer, an off-line die pressing method is used to die press the bonding layer, and a commonly used diamond die pressing pattern on the market is specifically selected, and its die pressing process: die pressing speed: 60 m / min, die pressing temperature: 100 °C, die pressing pressure: 2 MPa.

[0060] The total thickness of the in-mold label film in this comparative example is 100 μm, the thickness of the surface layer 1 is 1 μm, the thickness of the support layer 2 is 89 μm, and the thickness of the bonding layer 3 is 10 μm.

[0061] The application process of the in-mold label film in this comparative example is the same as that of the anti-sticking and easy-exhaust in-mold label film in Example 1.

[0062] Comparative Example 3 This comparative example provides an in-mold label film. Please refer to Figure 1 , which is a four-layer structure, including a surface layer 1, a support layer 2, a bonding layer 3, and a roughened bonding layer 4 arranged in sequence. Among them, the raw material formula of each layer is the same as that of Example 1.

[0063] The preparation method of the in-mold label film in this comparative example is basically the same as that of the anti-sticking and easy-exhaust in-mold label film in Example 1, except that: in step (1), the ethylene-octene copolymer powder in the powder tank is given a static electricity of -15 KV on its surface; in step (2), the bonding layer surface of the thickened sheet C is given a static electricity of +15 KV.

[0064] The total thickness and the thickness of each layer of the in-mold label film in this comparative example are the same as those of Example 1.

[0065] The application process of the in-mold label film in this comparative example is the same as that of the anti-sticking and easy-exhaust in-mold label film in Example 1.

[0066] Example 2 This example provides an anti-sticking and easy-exhaust in-mold label film. Please refer to Figure 1 , including a surface layer 1, a support layer 2, a bonding layer 3, and a roughened bonding layer 4 arranged in sequence.

[0067] Among them, the raw material formula of each layer is as follows: Surface layer 1: The same as the surface layer 1 of Example 1; Support layer 2: The same as the support layer 2 of Example 1; Adhesive layer 3: 100 wt% propylene-ethylene copolymer (ethylene content is 9 wt%, density is 0.879 g / cm 3 , melting point is 77 °C, melt index is 8 g / 10 min, melt index test conditions: melting temperature is 230 °C, load weight is 2.16 kg); Roughened adhesive layer 4: Has the same raw material formulation as adhesive layer 3.

[0068] This embodiment also provides a method for preparing an anti-sticking and easy-to-exhaust in-mold label film, which is basically the same as that of Example 1, except that: the raw materials of adhesive layer 3 and roughened adhesive layer 4 are different.

[0069] The total thickness and the thickness of each layer of the anti-sticking and easy-to-exhaust in-mold label film in this embodiment are the same as those of Example 1.

[0070] The application process of the anti-sticking and easy-to-exhaust in-mold label film in this embodiment is basically the same as that of Example 1, except that: the plastic part is a copolymerized polypropylene plastic part, that is, high-density polyethylene is replaced by copolymerized polypropylene.

[0071] Example 3 This embodiment provides an anti-sticking and easy-to-exhaust in-mold label film. Please refer to Figure 1 , which includes a surface layer 1, a support layer 2, an adhesive layer 3, and a roughened adhesive layer 4 arranged in sequence.

[0072] Among them, the raw material formulations of each layer are as follows: Surface layer 1: The same as surface layer 1 in Example 1; Support layer 2: The same as support layer 2 in Example 1; Adhesive layer 3: 100 wt% maleic anhydride grafted propylene-ethylene copolymer (ethylene content is 9 wt%, maleic anhydride grafting rate is 1.0 wt%, density is 0.879 g / cm 3 , melting point is 77 °C, melt index is 8 g / 10 min, melt index test conditions: melting temperature is 230 °C, load weight is 2.16 kg); Roughened adhesive layer 4: Has the same raw material formulation as adhesive layer 3.

[0073] This embodiment also provides a method for preparing an anti-sticking and easy-to-exhaust in-mold label film, which is basically the same as that of Example 1, except that: the raw materials of adhesive layer 3 and roughened adhesive layer 4 are different; and in the traction-thickness measurement-corona-winding process K, the surface of the roughened adhesive layer 4 is also subjected to corona treatment, and the corona intensity is 40 W·min / m 2 , to improve the adhesion fastness of the roughened adhesive layer 4 during subsequent application.

[0074] The total thickness and the thickness of each layer of the anti-sticking and easy-to-exhaust in-mold label film in this embodiment are the same as those of Example 1.

[0075] The application process of the anti - connected label and easy - exhaust in - mold label film in this embodiment is basically the same as that in Embodiment 1, except that: the in - mold labeling process S is carried out through an injection - blow molding process: polyethylene terephthalate is injection - molded to form a plastic blank, then the above - mentioned plastic blank is put into the mold with the in - mold label, then the above - mentioned plastic blank is heated, and gas is introduced to make the plastic blank expand. At the same time, the plastic blank will be welded together with the roughened adhesive layer of the in - mold label. Finally, after cooling, the in - mold label film and the plastic part are integrated into one, forming a polyethylene terephthalate plastic part O with an in - mold label.

[0076] Performance evaluation The following performance evaluations are carried out on the in - mold label films, in - mold labels, and plastic parts with in - mold labels of Examples 1 - 3 and Comparative Examples 1 - 2 respectively: Roughness: The surface roughness of the roughened adhesive layer 4 or the bonding layer 3 of the in - mold label film (i.e., the other surface of the in - mold label film opposite to the surface of the surface layer 1) is measured according to the national standard GB / T 14234 - 1993. The measuring instrument is a surface roughness meter (manufactured by Mitutoyo Corporation, Japan, model: SJ - 210).

[0077] Normal - temperature adhesion: Two in - mold label films are stacked together, pressed with a 10 - kg weight, then placed in an oven at 60 °C for 30 min to simulate the summer container transportation conditions. Finally, the bonding force between the two in - mold label films is measured by a film adhesion tester (manufactured by Dynisco Corporation, USA, model: D9047).

[0078] Coefficient of friction: The coefficient of friction of the roughened adhesive layer 4 or the bonding layer 3 of the in - mold label film (i.e., the other surface of the in - mold label film opposite to the surface of the surface layer 1) is measured according to the national standard GB / T 10006 - 2021. The measuring instrument is a coefficient - of - friction measuring instrument (manufactured by Testing Machine, USA, model: 32 - 07 - 00 - 0003).

[0079] Surface resistance: The surface resistance of the roughened adhesive layer 4 or the bonding layer 3 of the in - mold label film (i.e., the other surface of the in - mold label film opposite to the surface of the surface layer 1) is measured according to the national standard GB / T 31838.3 - 2019. The measuring instrument is a surface resistance meter (manufactured by SIMCO Corporation, Japan, model: ST - 4).

[0080] Connected - sheet phenomenon: A stack of 500 in - mold labels is tied with a rubber band, pressed with a 10 - kg weight, placed in an oven at 60 °C for 30 min, the rubber band is untied, and the in - mold labels are taken out by a manipulator to observe the connected - sheet situation.

[0081] Heat seal strength: This test simulates the adhesion strength between the in-mold label and the plastic part after in-mold labeling. First, high-density polyethylene films, copolymer polypropylene films, and polyethylene terephthalate films with a thickness of 100 µm are obtained through a casting process. Then, using a heat sealer, the in-mold label is heat-sealed with the high-density polyethylene film, copolymer polypropylene film, or polyethylene terephthalate film at 135 °C, 0.18 MPa, for 1 second (the in-mold labels in Example 1 and Comparative Examples 1-3 correspond to the high-density polyethylene film, the in-mold label in Example 2 corresponds to the copolymer polypropylene film, and the in-mold label in Example 3 corresponds to the polyethylene terephthalate film). After that, the samples are left standing in the test environment for 3 minutes, and then the samples are cut into strips with a width of 15 mm and a length of 15 cm. Finally, the heat-sealed interface is peeled off, and according to the national standard GB / T 10006-2021, the heat seal strength is measured using a universal tensile machine.

[0082] Appearance of the printed layer surface: Observe whether the texture of the roughened adhesive layer in the stacked in-mold labels affects the appearance of the printed layer, that is, whether the appearance of the printed layer surface is abnormal.

[0083] Yield of in-mold labeling: Count the proportion of in-mold labels without air bubble abnormalities between the in-mold labels and the plastic parts among 100 plastic parts with in-mold labels.

[0084] Table 1 Composition of each layer and performance test results of the in-mold label films in Example 1 and Comparative Examples 1-3

[0085] Table 2 Composition of each layer and performance test results of the in-mold label films in Examples 2-3

[0086] In the preparation method of the anti-sticking and easy-exhausting in-mold label film in Examples 1-3 of the present invention, by adopting a specific roughening treatment process, a roughened adhesive layer with an uneven surface texture is formed on the surface of the bonding layer of the finally prepared anti-sticking and easy-exhausting in-mold label film. After the anti-sticking and easy-exhausting in-mold label film is made into an in-mold label, the effective contact area between the in-mold labels can be greatly reduced, thereby avoiding label sticking; and during the stacking process of the in-mold labels, the texture morphology of the roughened adhesive layer will not be transferred to the printed layer, avoiding affecting the appearance of the printed layer surface; in addition, when the in-mold label is attached to the plastic part, air can be exhausted in time without gas accumulation to form bubbles, greatly reducing the probability of bubbles appearing between the in-mold label and the plastic part, thereby improving the yield of in-mold labeling.

[0087] The in-mold label film of Comparative Example 1 does not contain a roughened adhesive layer. The in-mold label film of Comparative Example 1 has a high room-temperature adhesion, and the in-mold labels produced are prone to label sticking. Moreover, due to the smooth surface of the bonding layer, when the in-mold label is used for in-mold labeling, the in-mold labeling yield is relatively low, and air bubble abnormalities are likely to occur.

[0088] The in-mold label film of Comparative Example 2 does not contain a roughened adhesive layer. In the preparation process, a molding method is used to roughen the bonding layer, so that sharp embossing peaks are formed on the surface of the bonding layer. After the in-mold label film of Comparative Example 1 is made into an in-mold label, the sharp embossing peaks will be transferred to the surface of the printing layer during the stacking process, affecting the surface appearance of the printing layer. In addition, after the in-mold label is used for in-mold labeling, there will be certain air bubble abnormalities, and the in-mold labeling yield is relatively low.

[0089] For the in-mold label film of Comparative Example 3, the static electricity value obtained by roughening the surface of the adhesive layer powder and the surface of the bonding layer of the thick sheet during the preparation process is lower than 25 KV, resulting in insufficient adsorption and even spreading of the ethylene-octene copolymer powder on the surface of the bonding layer of the thick sheet, leading to a decrease in the roughness and exhaust effect of the prepared anti-label-sticking and easy-exhaust in-mold label film. When the in-mold label made is used for in-mold labeling, the in-mold labeling yield will decrease.

[0090] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and the present invention also intends to include these modifications and improvements.

Claims

1. A method for preparing an anti - label - sticking and easy - exhaust in - mold label film, characterized in that: The anti - label - sticking and easy - exhaust in - mold label film includes a surface layer, a support layer, an adhesion layer, and a roughened adhesion layer arranged in sequence; the adhesion layer is composed of one of ethylene - α - olefin copolymer, propylene - α - olefin copolymer, and maleic anhydride - grafted propylene - α - olefin copolymer; the raw material components of the roughened adhesion layer are the same as those of the adhesion layer; The method for preparing the anti - label - sticking and easy - exhaust in - mold label film includes the following steps: Grind the raw materials of the roughened adhesion layer into a powder form, that is, obtain the roughened adhesion layer powder. Through the high - voltage tip - discharge process, make the surface of the roughened adhesion layer powder obtain an electrostatic charge of - / + (25 - 30) KV for standby; Send the raw materials of the surface layer, support layer, and adhesion layer into the extruders corresponding to each layer respectively, and form a cast sheet through the extrusion - casting process; The cast sheet undergoes a longitudinal stretching process to form a thick sheet; The thick sheet undergoes a roughening treatment process: make the roughened adhesion layer powder adsorb and weld on the surface of the adhesion layer of the thick sheet to form a roughened treatment thick sheet; The roughened treatment thick sheet undergoes a transverse stretching process and a traction - thickness measurement - corona - winding process to obtain a film semi - finished product; The film semi - finished product undergoes an aging - slitting process to obtain a film finished product, that is, the anti - label - sticking and easy - exhaust in - mold label film.

2. The preparation method of the anti-connected label and easy-to-exhaust in-mold label film according to claim 1, characterized in that: The roughening treatment process includes the following steps: Through the high - voltage tip - discharge process on the surface of the adhesion layer of the thick sheet, make the surface of the adhesion layer of the thick sheet obtain an electrostatic charge of + / - (25 - 30) KV; utilize the mechanism of attraction between positive and negative charges to make a layer of roughened adhesion layer powder adsorb on the surface of the adhesion layer of the thick sheet, and utilize the residual temperature of the thick sheet after the longitudinal stretching process to make the roughened adhesion layer powder weld with the adhesion layer of the thick sheet together to form the roughened treatment thick sheet.

3. The preparation method of the anti-connected label and easy-to-exhaust in-mold label film according to claim 1, characterized in that: In the transverse stretching process, the transverse stretching ratio is 8 - 10.

4. The preparation method of the anti-connected label and easy-to-exhaust in-mold label film according to claim 1, characterized in that: After the longitudinal stretching process, the temperature on the surface of the adhesion layer of the thick sheet is 105 - 110 °C.

5. The preparation method of the anti-connected label and easy-exhaust in-mold label film according to claim 1, characterized in that: The preparation method of the roughened adhesion layer powder is: Cool the raw materials of the roughened adhesion layer with liquid nitrogen and then place them in a grinding machine for grinding, and then screen them through a sieve shaker into a powder with an average particle size of 40 - 60 µm, that is, obtain the roughened adhesion layer powder.

6. According to the method for preparing the anti - label - sticking and easy - exhaust in - mold label film according to claim 1, characterized in that: After obtaining the roughened adhesion layer powder, place the roughened adhesion layer powder in a powder tank, and then perform the high - voltage tip - discharge process on the roughened adhesion layer powder in the powder tank; In the roughening treatment process, make the thick sheet pass through the powder tank, and the distance between the adhesion layer of the thick sheet and the roughened adhesion layer powder in the powder tank is 10 - 20 mm.

7. According to the method for preparing the anti - label - sticking and easy - exhaust in - mold label film according to claim 1, characterized in that: The content of α - olefin in the ethylene - α - olefin copolymer is 10 - 30 wt%, and the α - olefin in the ethylene - α - olefin copolymer is at least one of butene, hexene, and octene; The content of α - olefin in the propylene - α - olefin copolymer is 4 - 15 wt%, and the α - olefin in the propylene - α - olefin copolymer is at least one of ethylene, butene, and hexene; The maleic anhydride grafting rate in the maleic anhydride grafted propylene-α-olefin copolymer is 0.8-1.3 wt%, the content of α-olefin in the maleic anhydride grafted propylene-α-olefin copolymer is 4-15 wt%, and the α-olefin in the maleic anhydride grafted propylene-α-olefin copolymer is at least one of ethylene, butene, and hexene.

8. The method for preparing the anti-sticking and easy-to-exhaust in-mold label film according to claim 1, wherein: The surface layer comprises homopolypropylene and an anti-blocking agent, and the anti-blocking agent is at least one of silicon dioxide and polymethyl methacrylate; the support layer comprises homopolypropylene, calcium carbonate, titanium dioxide, and an antistatic agent. The calcium carbonate is heavy calcium carbonate, the average particle size of the calcium carbonate is 1-2 µm, the titanium dioxide is rutile titanium dioxide synthesized by the chlorination method, and the average particle size of the titanium dioxide is 0.2-0.4 µm; the melt index of the homopolypropylene in the surface layer and the support layer is 2.8-3.2 g / 10 min, the isotacticity is 95-97%, and the melting point temperature is 160-163 °C.

9. An anti-connected label and easy-to-exhaust in-mold label film, characterized in that: Prepared by the method for preparing the anti-sticking and easy-to-exhaust in-mold label film according to any one of claims 1-8.

10. Application of the anti-connected label and easy exhaust in-mold label film as described in claim 9 in in-mold labeling, characterized in that: After the anti-sticking and easy-to-exhaust in-mold label film is made into an in-mold label, the in-mold label and the plastic part are integrated into one body through an in-mold labeling process to form a plastic part with an in-mold label; When the bonding layer is composed of an ethylene-α-olefin copolymer, the plastic part is a polyethylene plastic part; when the bonding layer is composed of a propylene-α-olefin copolymer, the plastic part is a polypropylene plastic part; when the bonding layer is composed of a maleic anhydride grafted propylene-α-olefin copolymer, the plastic part is a polyester plastic part or a polyamide plastic part.

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