A low-noise adhesive-free film for digital printing and a preparation method thereof

Abstract

The present invention relates to the technical field of biaxially oriented films, and in particular to a low-noise digital printing tackifying adhesive-free film and a preparation method thereof, wherein the low-noise digital printing tackifying adhesive-free film comprises a release functional layer, a core layer and a tackifying hot melt adhesive layer arranged in sequence, the release functional layer comprises 0.5-2.5wt% aminosilicone grafted polypropylene and homopolymerized polypropylene, and the surface energy of the release functional layer is 24-26dyn / cm; the core layer comprises homopolymerized polypropylene; the tackifying hot melt adhesive layer comprises ethylene-vinyl acetate copolymer A, 5-10wt% ethylene-vinyl acetate copolymer B and 0.2-0.5wt% polyorganosiloxane elastomer. The low-noise digital printing tackifying adhesive-free film of the present invention belongs to a biaxially oriented polypropylene film, does not require secondary coating processing, is energy-saving and environmentally friendly, is smooth to receive and unwind during production and application, has low unwinding noise, and effectively ensures the composite fastness between the film and the printed piece, and is particularly suitable for the coating of digital printed pieces with a high content of silicone oil and wax.

Description

Technical Field

[0001] The invention relates to the technical field of biaxially stretched films, in particular to a low-noise adhesive-free film for digital printing and a preparation method thereof. Background Art

[0002] In the field of digital printing, printed patterns are usually coated to improve the surface gloss and fastness of printed products, play a protective role such as waterproof, anti-fouling, wear-resistant, and fold-resistant, and extend the service life of the product. However, the content of silicone oil and wax in digital printing ink is relatively high, resulting in low surface energy of the printed piece. During the coating, the digital printed piece is not easy to combine with the hot melt adhesive layer, which affects the hot pressing composite effect and causes the insufficient bonding fastness between the printed piece and the film after coating. For this reason, Chinese Patent 109337598A discloses a digital pre-coated film and a preparation method thereof, which improves the fluidity of the ethylene-vinyl acetate polymer by setting the content of vinyl acetate in the ethylene-vinyl acetate polymer, and also reduces the softening point of the ethylene-vinyl acetate polymer, thereby improving the bonding performance of the ethylene-vinyl acetate polymer. At the same time, a tackifier is added to the hot melt adhesive layer, and the tackifier is used to improve the wetting performance and bonding force of the hot melt adhesive to the substrate, thereby improving the bonding strength of the pre-coated film.

[0003] However, the above patents still have the following deficiencies: first, the pre-coating process is still adopted, and the hot melt adhesive layer is formed on the surface of the base coating layer by the cast film method, which is still a secondary processing process, which increases the cost and is not conducive to energy conservation and environmental protection; second, the film coating speed may have to be reduced due to the unsmooth winding and unwinding, which is not conducive to improving the efficiency of downstream applications. At the same time, a large amount of noise may be generated during the slitting process due to the unsmooth winding and unwinding, affecting the health of production workers. Summary of the invention

[0004] Based on this, the purpose of the present invention is to provide a low-noise adhesive-free film for digital printing and a preparation method thereof, which is a biaxially oriented polypropylene film, does not require secondary coating processing, is energy-saving and environmentally friendly, has smooth winding and unwinding during production and application, has low unwinding noise, and effectively ensures the composite fastness between the film and the printed part, and is particularly suitable for lamination of digital printed parts with a high content of silicone oil and wax.

[0005] The technical solution of the present invention is achieved by the following methods:

[0006] A low-noise adhesive-free film for digital printing comprises a release function layer, a core layer and an adhesive hot-melt adhesive layer which are arranged in sequence, wherein the release function layer comprises 0.5-2.5wt% of aminosiloxane grafted polypropylene and homopolypropylene, and the surface energy of the release function layer is 24-26dyn / cm; the core layer comprises homopolypropylene; the adhesive hot-melt adhesive layer comprises ethylene-vinyl acetate copolymer A, 5-10wt% of ethylene-vinyl acetate copolymer B and 0.2-0.5wt% of polyorganosiloxane elastomer; the vinyl acetate content in the ethylene-vinyl acetate copolymer A is 20-25wt%; the long chain branching degree in the ethylene-vinyl acetate copolymer B (the long chain in the present invention specifically refers to the branched chain with C atoms ≥6) is (0.01-0.02) / 1000C, and the vinyl acetate content in the ethylene-vinyl acetate copolymer B is 28-32wt%.

[0007] Starting from the problem that the surface energy of the printed part is low due to the high content of silicone oil and wax in digital printing ink, which affects the composite effect, the inventors have made differentiated functional collaborative designs for the release functional layer and the tackifying hot melt adhesive layer of the film after in-depth research. On the one hand, the components of the tackifying hot melt adhesive layer are innovatively designed, and ethylene-vinyl acetate copolymer (EVA) with different vinyl acetate (VA) contents are added to improve its composite applicability to digital printed parts with high silicone oil and wax content, thereby ensuring the composite effect; on the other hand, the inventors have taken into account the problem that the tackifying hot melt adhesive layer may affect the smoothness of winding and unwinding of the film, and set up a release functional layer, and added a certain amount of aminosilicone grafted polypropylene to the release functional layer, which is conducive to smooth winding and unwinding between the tackifying hot melt adhesive layer and the release functional layer during production and application, and reduces the noise generated during the unwinding process. In addition, the aminosilicone grafted polypropylene will not migrate to the tackifying hot melt adhesive layer during the winding and unwinding process, and will not have an adverse effect on the composite fastness between the tackifying hot melt adhesive layer and the printed part. In addition, in order to further ensure the smoothness of winding and unwinding, the inventor also added a certain amount of polyorganosiloxane elastomer to the thickening hot melt adhesive layer, which is conducive to reducing the sticking phenomenon of the thickening hot melt adhesive layer during the biaxial stretching production of the film, and cooperates with the release functional layer to jointly ensure the smoothness of winding and unwinding during film production and application, and reduce the unwinding noise. Under the differential functional synergy of the release functional layer and the thickening hot melt adhesive layer of the film, the prepared film of the present invention is smooth and non-sticky to the roller during the biaxial stretching production process, and the winding and unwinding process of the film is smooth, which is conducive to reducing the unwinding noise, meeting the application requirements of downstream customers such as secondary slitting and unwinding coating, and at the same time, there is no need to reduce the coating speed during coating, and it is conducive to ensuring the composite fastness between the film thickening hot melt adhesive layer and the printed part, especially suitable for the coating of digital printed parts with a high content of silicone oil and wax.

[0008] The tackifying hot melt adhesive layer of the low-noise tackifying non-adhesive film for digital printing of the present invention comprises ethylene-vinyl acetate copolymer A, 5-10wt% ethylene-vinyl acetate copolymer B and 0.2-0.5wt% polyorganosiloxane elastomer, wherein the content of vinyl acetate in the ethylene-vinyl acetate copolymer A is 20-25wt%; the long chain branching degree (long chain specifically refers to the branched chain with C atoms ≥6) in the ethylene-vinyl acetate copolymer B is (0.01-0.02) / 1000C, and the content of vinyl acetate in the ethylene-vinyl acetate copolymer B is 28-32wt%. Adding 5-10wt% ethylene-vinyl acetate copolymer B (VA content is 28-32wt%) to the tackifying hot melt adhesive layer is beneficial to improving the composite fastness between the film and the printed piece. If the amount of ethylene-vinyl acetate copolymer B with high VA content added is more than 0.5wt%, the resin melt of the tackifying hot melt adhesive layer may be too viscous to be effectively extruded, which is not conducive to the smoothness of production; if the amount of ethylene-vinyl acetate copolymer B with high VA content added is less than 0.2wt%, it will not have an effective tackifying effect, and cannot effectively improve the composite fastness between the film and the printed part, especially it cannot be applied to digital printed parts with high silicone oil and wax content. The vinyl acetate content in the ethylene-vinyl acetate copolymer B described in this application is 28-32wt%, and the long chain branching degree (long chain specifically refers to branched chains with carbon atoms ≥ 6) in the ethylene-vinyl acetate copolymer B is (0.01~0.02) / 1000C. The ethylene-vinyl acetate copolymer B with the higher VA content and the specific long-chain branching degree has better hot tack and is more conducive to ensuring the composite fastness between the tackifying hot melt adhesive layer and the printed piece. Preferably, the long-chain branching degree in the ethylene-vinyl acetate copolymer B is 0.017 / 1000C. Controlling the VA content of the ethylene-vinyl acetate copolymer B to 28-32wt% is conducive to obtaining the best tackifying effect. If the VA content is lower than 28wt%, the tackifying effect is not obvious. If the VA content is higher than 32wt%, it is easy to degrade and break the film during high-temperature co-extrusion, which leads to the inability to produce smoothly. At the same time, ethylene-vinyl acetate copolymer A with a lower VA content (VA content of 20-25wt%) is selected as the main component of the tackifying hot melt adhesive layer. On the one hand, the tackifying hot melt adhesive layer will not be too sticky as a whole. On the other hand, it is conducive to maintaining a certain interlayer bonding force between the tackifying hot melt adhesive layer and the core layer, and there will be no interlayer peeling. It can be biaxially stretched at a large ratio and maintain the smoothness of normal production, while maintaining the adhesion between the tackifying hot melt adhesive layer and the printed material. In order to further ensure smooth production and non-stick rollers, 0.2-0.5wt% polyorganosiloxane elastomer is also added to the tackifying hot melt adhesive layer. The main chain of the polyorganosiloxane elastomer is composed of repeated silicon oxygen bonds (Si-O-Si). The appropriate amount of polyorganosiloxane elastomer will not have an adverse effect on the thermal viscosity of the tackifying hot melt adhesive layer, and the organic groups on the side chains are conducive to its uniform dispersion in the tackifying hot melt adhesive layer.

[0009] It is well known to those skilled in the art that the increase in the viscosity of the hot melt adhesive layer is not conducive to the smoothness of the film itself during production and application. Aminosilicone grafted polypropylene is a macromolecular polymer with a relatively low surface energy. The present invention takes into account the adverse effects of the improvement of the components of the tackifying hot melt adhesive layer on the smoothness of the reeling and unwinding, and chooses to add 0.5-2.5wt% aminosilicone grafted polypropylene to the release functional layer, so that the surface energy of the release functional layer reaches 24-26dyn / cm, and the polyorganosiloxane elastomer in the synergistic tackifying hot melt adhesive layer is conducive to the smooth reeling and unwinding between the tackifying hot melt adhesive layer and the release functional layer during production and application, and reduces the noise generated during the unwinding process. In addition, the aminosilicone grafted polypropylene will not migrate to the tackifying hot melt adhesive layer during the reeling and unwinding process, and will not have an adverse effect on the composite fastness between the tackifying hot melt adhesive layer and the printed piece. If the addition amount of aminosilicone grafted polypropylene is less than 0.5wt%, it cannot effectively improve the decrease in the smoothness of winding and unwinding caused by viscosity increase. If the addition amount of aminosilicone grafted polypropylene is higher than 2.5wt%, due to the presence of polar amino components in aminosilicone grafted polypropylene, the polarity of the release functional layer and the core layer may differ too much, thereby affecting the interlayer bonding strength and causing interlayer peeling during biaxial stretching.

[0010] Further, the aminosilicone grafted polypropylene is prepared by condensation reaction of maleic anhydride grafted polypropylene and aminosilicone, the melt index of the aminosilicone grafted polypropylene is 5-10g / 10min, and the grafting rate of the aminosilicone is 1.5-2.5%. Selecting the melt index of the aminosilicone grafted polypropylene in the above range is conducive to ensuring its melt flow matching with the homopolymer polypropylene in the release functional layer, which is conducive to the stability of the co-extruded melt. The grafting rate of the aminosilicone is 1.5-2.5%. If the grafting rate of the aminosilicone is lower than 1.5%, it is impossible to effectively improve the decline in the smoothness of the winding and unwinding caused by viscosity increase. If the grafting rate of the aminosilicone is higher than 2.5%, due to the presence of polar amino components in the aminosilicone grafted polypropylene, the polarity of the release functional layer and the core layer will be too different, thereby affecting the interlayer bonding force, resulting in the phenomenon of interlayer peeling during the biaxial stretching process, and increasing the risk of degradation of the aminosilicone grafted polypropylene during production and processing, which is not conducive to the quality of film production.

[0011] Furthermore, the tackifying hot melt adhesive layer also includes 1.5-5wt% rosin pentaerythritol ester, and the softening point of the rosin pentaerythritol ester is 80-90°C. In order to further ensure that the prepared tackifying adhesive-free film has the best viscosity, 1.5-5wt% rosin pentaerythritol ester can also be added to the tackifying hot melt adhesive layer, which can form a good tackifying synergistic effect with ethylene-vinyl acetate copolymer B. The use of rosin pentaerythritol ester with a softening point of 80-90°C is conducive to the tackifying hot melt adhesive layer to obtain the best hot viscosity. If the softening point of rosin pentaerythritol ester is higher than 90°C, it cannot form a good tackifying synergistic effect with ethylene-vinyl acetate polymer B. If the softening point of rosin pentaerythritol ester is lower than 80°C, it may cause the resin melt of the tackifying hot melt adhesive layer to be too viscous and unable to be effectively extruded, and it cannot be smoothly reeled and unwound, resulting in film adhesion.

[0012] Furthermore, the melt index of the ethylene-vinyl acetate copolymer A and the ethylene-vinyl acetate copolymer B are both 20-25 g / 10 min, and the weight average molecular weight of the ethylene-vinyl acetate copolymer B is (22-30)×10 4 g / mol, and the molecular weight distribution index is 15-20. Controlling the melt index of ethylene-vinyl acetate copolymer A and ethylene-vinyl acetate copolymer B within the above range is conducive to ensuring good melt fluidity during the processing and production process, and is conducive to the effective extrusion of the tackifying hot melt adhesive layer resin melt without being too sticky, so that the production is smooth and the subsequent film thermal composite can meet the composite fastness requirements. The weight average molecular weight of ethylene-vinyl acetate copolymer B is controlled at (22~30)×10 4 g / mol, the molecular weight distribution index is controlled at 15-20, and the addition of the above-mentioned specific ethylene-vinyl acetate copolymer B has better hot viscosity, which is more conducive to ensuring the composite fastness between the tackifying hot melt adhesive layer and the printed piece. Preferably, the weight average molecular weight of the ethylene-vinyl acetate copolymer B is 28×10 4 g / mol, and the molecular weight distribution index is 17.

[0013] Furthermore, the particle size D50 of the polyorganosiloxane elastomer is 4-12 μm. Adding a polyorganosiloxane elastomer of suitable particle size to the tackifying hot melt adhesive layer can improve the anti-adhesion performance of the tackifying hot melt adhesive layer and prevent the inner and outer layers of the rolled film from contacting each other (i.e., between the tackifying hot melt adhesive layer and the release functional layer) from being smoothly rolled up and unrolled.

[0014] Furthermore, the homopolypropylene in the release functional layer and the core layer is isotactic polypropylene, the isotacticity of the isotactic polypropylene is 95.5-97.5%, and the melt index is 2.8-3.8 g / 10 min. Limiting the homopolypropylene in the release functional layer and the core layer to isotactic polypropylene, and controlling the isotacticity of the isotactic polypropylene to 95.5-97.5% and the melt index to 2.8-3.8 g / 10 min is conducive to ensuring the excellent mechanical properties of the film as a whole, and is also conducive to the affinity between the homopolypropylene in the core layer and the ethylene-vinyl acetate copolymer, avoiding the interlayer peeling phenomenon.

[0015] Furthermore, the thickness of the release functional layer is 0.8-1.5 μm, the thickness of the tackifying hot melt adhesive layer is 2-10 μm, and the total thickness of the low-noise tackifying adhesive-free film for digital printing is 15-30 μm. The thickness of the tackifying hot melt adhesive layer is set to 3-10 μm in the present invention, which can effectively achieve the thickening and tackifying effect of the tackifying hot melt adhesive layer, which is conducive to ensuring the composite effect between the film and the printed part.

[0016] Furthermore, the surface of the tackifying hot melt adhesive layer is subjected to corona and / or flame treatment. After the corona and / or flame treatment, the prepared film has better applicability for further processing.

[0017] The present invention also provides a method for preparing any of the above-mentioned low-noise adhesive-free films for digital printing, comprising the following steps: the component raw materials of the release functional layer, the core layer, and the adhesive hot-melt adhesive layer are put into a batching unit, co-extruded through an extruder after metering, merged in a three-layer die head after a flow channel distributor, and then cooled by a chilled roller to form a resin sheet, the resin sheet is biaxially stretched to form a film, the film is cooled by air shower, the thickness is controlled by a trimming machine, and the film is corona and / or flame treated before being harvested into a film master roll, the film master roll is aging treated, slit, and packaged, and then stored as a finished product.

[0018] Furthermore, Teflon coating is provided on the surface of the tackifying hot melt adhesive layer feed trough of the extruder and on the surface of the stretching roller used for biaxial stretching. It can respectively prevent the ethylene-vinyl acetate copolymer A and the ethylene-vinyl acetate copolymer B from sticking together during the extrusion and stretching process, thereby avoiding affecting the smoothness of processing and the integrity of the film surface, and the appropriate viscosity of the ethylene-vinyl acetate copolymer also avoids the film from slipping, scratching and other problems on the stretching roller with Teflon coating.

[0019] The low-noise adhesive-free film for digital printing described in the present invention belongs to a biaxially stretched polypropylene film, does not require secondary processing, is energy-saving and environmentally friendly, and under the synergistic effect of the differential functions of the release functional layer and the adhesive hot-melt adhesive layer of the film, the prepared film is smooth and does not stick to the roller during the biaxial stretching production process, and the film is smoothly unwound during production and application, which is beneficial to reducing the unwinding noise and meeting the application requirements of downstream customers such as secondary slitting and unwinding coating. At the same time, there is no need to reduce the coating speed during coating, and it is beneficial to ensure the composite fastness between the film adhesive hot-melt adhesive layer and the printed part, and is particularly suitable for the coating of digital printed parts with a high content of silicone oil and wax.

[0020] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic structural diagram of a low-noise adhesive-free film for digital printing according to an embodiment of the present invention;

[0022] Among them, there are a release functional layer 1, a core layer 2, and a tackifying hot melt adhesive layer 3. DETAILED DESCRIPTION

[0023] It should be clear that the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the embodiments of the present application.

[0024] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the embodiments of the present application. The singular forms of "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0025] When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present application. On the contrary, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the attached claims. In the description of the present application, it should be understood that the terms "first", "second", "third", etc. are only used to distinguish similar objects, and do not have to be used to describe a specific order or sequence, nor can they be understood as indicating or implying relative importance. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to the specific circumstances.

[0026] In addition, in the description of this application, unless otherwise specified, "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0027] It should be understood that the embodiments of the present application are not limited to the precise structures described above and shown in the drawings, and various modifications and changes can be made without departing from the scope thereof. The scope of the embodiments of the present application is limited only by the appended claims.

[0028] See also Figure 1 As an embodiment of the present invention, this embodiment provides a low-noise adhesive-free film for digital printing, comprising a release functional layer, a core layer and a tackifying hot melt adhesive layer arranged in sequence, wherein the release functional layer comprises 0.5-2.5wt% aminosilicone grafted polypropylene and homopolymer polypropylene, and the surface energy of the release functional layer is 24-26dyn / cm; the core layer comprises homopolymer polypropylene; the tackifying hot melt adhesive layer comprises ethylene-vinyl acetate copolymer A, 5-10wt% ethylene-vinyl acetate copolymer B and 0.2-0.5wt% polyorganosiloxane elastomer; the vinyl acetate content in the ethylene-vinyl acetate copolymer A is 20-25wt%; the long chain branching degree in the ethylene-vinyl acetate copolymer B (the long chain in the present invention specifically refers to the branched chain with C atoms ≥6) is (0.01~0.02) / 1000C, and the vinyl acetate content in the ethylene-vinyl acetate copolymer B is 28-32wt%.

[0029] Furthermore, the aminosilicone grafted polypropylene is prepared by condensation reaction of maleic anhydride grafted polypropylene and aminosilicone, the melt index of the aminosilicone grafted polypropylene is 5-10g / 10min, and the grafting rate of the aminosilicone is 1.5-2.5%.

[0030] Furthermore, the tackifying hot melt adhesive layer further comprises 1.5-5wt% of rosin pentaerythritol ester, and the softening point of the rosin pentaerythritol ester is 80-90°C.

[0031] Furthermore, the melt index of the ethylene-vinyl acetate copolymer A and the ethylene-vinyl acetate copolymer B are both 20-25 g / 10 min, and the weight average molecular weight of the ethylene-vinyl acetate copolymer B is (22-30)×10 4 g / mol, and the molecular weight distribution index is 15-20.

[0032] Furthermore, the particle size D50 of the polyorganosiloxane elastomer is 4-12 μm.

[0033] Furthermore, the homopolymer polypropylene in the release functional layer and the core layer is isotactic polypropylene, the isotacticity of the isotactic polypropylene is 95.5-97.5%, and the melt index is 2.8-3.8 g / 10 min.

[0034] Furthermore, the thickness of the release functional layer is 0.8-1.5 μm, the thickness of the tackifying hot melt adhesive layer is 2-10 μm, and the total thickness of the low-noise tackifying adhesive-free film for digital printing is 15-30 μm.

[0035] Furthermore, the surface of the tackifying hot melt adhesive layer is subjected to corona and / or flame treatment.

[0036] The present invention also provides a method for preparing any of the above-mentioned low-noise adhesive-free films for digital printing, comprising the following steps: feeding the raw materials of each layer component into a batching unit and then entering an extruder after metering, controlling the extrusion temperature of the release functional layer and the core layer at 240-260°C, and the extrusion temperature of the adhesive hot melt adhesive layer at 200-240°C, and merging them at a multi-layer die head after passing through a flow channel distributor to form a multi-layer structure of resin melt, and then cooling them through a chilled roller at 25-35°C to form a multi-layer structure of resin sheet; introducing the resin sheet into a longitudinal stretching device in a biaxial stretching device, and the surface of the release functional layer is subjected to 130-1 The film is preheated at 35°C, the stretching temperature of the release functional layer and the core layer is controlled at 110-130°C, the tackifying hot melt adhesive layer is preheated at 50-90°C, the stretching temperature is controlled at 50-90°C, and the stretching ratio is 5.2-5.4 times, which is conducive to obtaining a relatively higher stiffness and smooth winding and unwinding of the film; then a transverse stretching device is introduced, after preheating at 165-175°C, it is stretched 8-10 times at 156-160°C, and then shaped at 165-170°C, cooled by air shower, and then the surface of the tackifying hot melt adhesive layer is corona or flame treated to obtain the film mother roll, and finally subjected to aging treatment, slitting and packaging to obtain the tackifying non-adhesive film.

[0037] Furthermore, Teflon coatings are provided on the surface of the tackifying hot melt adhesive layer feed trough of the extruder and on the surface of the stretching roller used for biaxial stretching.

[0038] The physical properties and test methods of the embodiments or comparative examples of the present invention are as follows:

[0039] Film thickness is measured according to GB / T6672-2001;

[0040] Melt index (melt mass flow rate MFR) is based on GB / T3682-2018, polypropylene is measured at 2.16kg and 230℃, ethylene-vinyl acetate copolymer is measured at 2.16kg and 190℃, the unit is g / 10min;

[0041] The surface energy is measured according to GB / T14216, and the surface energy of the film surface is measured with a dyne pen, and the unit is dyn / cm;

[0042] Peel strength of laminated digital printed parts: measured with reference to GB / T8808 (method A), the unit is N / 15mm; the laminated digital printed parts used in the present invention are 250g white card black spot color printed parts (the ink contains 0.5wt% silicone oil), which are aged at 45°C for 2h after lamination and measured under constant temperature and humidity conditions of 25°C and 55%.

[0043] Test method for slitting and unwinding noise: Wind a 6000-meter film roll with a Shore hardness of 85 at 40°C and 60±5% humidity, store it for 30 days, unwind it on the slitting machine at a line speed of 200 meters / minute, and use a GM1356 noise meter to test the surface, middle, and bottom noises. Take the average value of the noises at the three locations in decibels (dB).

[0044] Evaluation of production smoothness: whether the film is stratified, broken, and whether the winding and unwinding are smooth.

[0045] It should be noted that the VA content in the ethylene-vinyl acetate copolymer A used in the embodiments of the present invention is 20 wt %.

[0046] It should be noted that the proportions described in the embodiments of the present invention or comparative examples are all weight percentages. The components and contents of each layer in the embodiments of the present invention and comparative examples are shown in Table 1 below.

[0047] Table 1

[0048]

[0049] Example 1

[0050] This embodiment provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resin layers of the low-noise digital printing adhesive-free film of this embodiment comprises the following steps:

[0051] Preparation of release functional layer resin: 99.5wt% homopolymer polypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 0.5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin.

[0052] Preparation of core layer resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was used as the core layer resin.

[0053] Preparation of tackifying hot melt adhesive layer resin: 94.8wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%), 5wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 28wt%, long chain branching degree of 0.01 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and 0.2wt% polysiloxane elastomer (particle size D50 is 5μm) are evenly mixed to obtain a tackifying hot melt adhesive layer resin.

[0054] The preparation method of the BOPP film of this embodiment comprises the following steps: feeding the raw materials of each layer component into a batching unit and then entering an extruder after being metered, controlling the extrusion temperature of the release functional layer and the core layer at 240-260°C, and the extrusion temperature of the tackifying hot melt adhesive layer at 200-240°C, and merging them at a multi-layer die head after passing through a flow channel distributor to form a multi-layer structure of resin melt, and then cooling it through a chilled roller at 25-35°C to form a multi-layer structure of resin sheet; introducing the resin sheet into a longitudinal stretching device in a biaxial stretching device, and the release functional layer The surface of the release layer is preheated at 130-135°C, the stretching temperature of the release functional layer and the core layer is controlled at 110-130°C, the tackifying hot melt adhesive layer is preheated at 50-90°C, the stretching temperature is controlled at 50-90°C, and the stretching ratio is 5.2-5.4 times; then the transverse stretching device is introduced, after preheating at 165-175°C, it is stretched 8-10 times at 156-160°C, and then fixed at 165-170°C, cooled by air shower, and then the surface of the tackifying hot melt adhesive layer is corona treated (the energy density of the corona treatment is 1.875KJ / m 2 ), the film mother roll is collected, and finally after aging treatment, slitting and packaging, a low-noise tackified non-adhesive film for digital printing is obtained.

[0055] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0056] This embodiment also provides a laminated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The laminated digital printed part is obtained by directly thermally laminating the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0057] Example 2

[0058] This embodiment provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resin layers of the low-noise digital printing adhesive-free film of this embodiment comprises the following steps:

[0059] Preparation of release functional layer resin: 98.5wt% homopolymer polypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 1.5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin. Preparation of core layer resin: 100wt% isotactic polypropylene (isotacticity of 95.5%, melt index of 3.8 g / 10min) was taken as core layer resin.

[0060] Preparation of tackifying hot melt adhesive layer resin: 91.8wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%), 8wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 30wt%, long chain branching degree of 0.017 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and 0.2wt% polysiloxane elastomer (particle size D50 is 5μm) are evenly mixed to obtain a tackifying hot melt adhesive layer resin.

[0061] The preparation method of the low-noise adhesive-free film for digital printing of this embodiment is the same as that of embodiment 1, so it is not described in detail. The preparation method has a smooth process and smooth winding and unwinding.

[0062] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0063] This embodiment also provides a laminated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The laminated digital printed part is obtained by directly thermally laminating the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0064] Example 3

[0065] This embodiment provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resin layers of the low-noise digital printing adhesive-free film of this embodiment comprises the following steps:

[0066] Preparation of release functional layer resin: 97.5wt% homopolypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 2.5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin. Preparation of core layer resin: 100wt% isotactic polypropylene (isotacticity of 95.5%, melt index of 3.8 g / 10min) was taken as core layer resin.

[0067] Preparation of tackifying hot melt adhesive layer resin: 89.8wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%), 10wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 32wt%, long chain branching degree of 0.02 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and 0.2wt% polysiloxane elastomer (particle size D50 is 5μm) are evenly mixed to obtain a tackifying hot melt adhesive layer resin.

[0068] The preparation method of the low-noise adhesive-free film for digital printing of this embodiment is the same as that of embodiment 1, so it is not described in detail. The preparation method has a smooth process and smooth winding and unwinding.

[0069] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0070] This embodiment also provides a laminated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The laminated digital printed part is obtained by directly thermally laminating the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0071] Example 4

[0072] This embodiment provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resin layers of the low-noise digital printing adhesive-free film of this embodiment comprises the following steps:

[0073] Preparation of release functional layer resin: 98.5wt% homopolymer polypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 1.5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin. Preparation of core layer resin: 100wt% isotactic polypropylene (isotacticity of 95.5%, melt index of 3.8 g / 10min) was taken as core layer resin.

[0074] Preparation of tackifying hot melt adhesive layer resin: 90.3wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%), 8wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 30wt%, long chain branching degree of 0.017 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and 0.2wt% polysiloxane elastomer (particle size D50 is 5μm) and 1.5wt% rosin pentaerythritol ester (softening point is 85℃) are evenly mixed to obtain a tackifying hot melt adhesive layer resin.

[0075] The preparation method of the low-noise adhesive-free film for digital printing of this embodiment is the same as that of embodiment 1, so it is not described in detail. The preparation method has a smooth process and smooth winding and unwinding.

[0076] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0077] This embodiment also provides a laminated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The laminated digital printed part is obtained by directly thermally laminating the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0078] Comparative Example 1

[0079] This comparative example provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resins of each layer of the low-noise digital printing adhesive-free film of this comparative example comprises the following steps:

[0080] Preparation of release functional layer resin: 100 wt % homopolypropylene (melt index of 3.8 g / 10 min, isotacticity of 95.5%) was used as the release functional layer resin.

[0081] Preparation of core layer resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was used as the core layer resin.

[0082] Preparation of tackifying hot melt adhesive layer resin: 91.8wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%), 8wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 30wt%, long chain branching degree of 0.017 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and 0.2wt% polysiloxane elastomer (particle size D50 is 5μm) are evenly mixed to obtain a tackifying hot melt adhesive layer resin.

[0083] The preparation method of the low-noise adhesive-free film for digital printing in this comparative example is the same as that in Example 1, so it is not described in detail. In this preparation method, the winding and unwinding of the roll is not smooth enough.

[0084] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0085] This comparative example also provides a coated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The coated digital printed part is obtained by directly thermally compounding the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0086] Comparative Example 2

[0087] This comparative example provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resins of each layer of the low-noise digital printing adhesive-free film of this comparative example comprises the following steps:

[0088] Preparation of release functional layer resin: 95wt% homopolymer polypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin.

[0089] Preparation of core layer resin: 100 wt % isotactic polypropylene (isotacticity: 95.5%, melt index: 3.8 g / 10 min) was used as the core layer resin.

[0090] Preparation of tackifying hot melt adhesive layer resin: 91.8wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%), 8wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 30wt%, long chain branching degree of 0.017 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and 0.2wt% polysiloxane elastomer (particle size D50 is 5μm) are evenly mixed to obtain a tackifying hot melt adhesive layer resin.

[0091] The preparation method of the low-noise adhesive-free film for digital printing in this comparative example is the same as that in Example 1, so it is not described in detail. In this preparation method, the process is not smooth enough and there is a layer peeling phenomenon.

[0092] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0093] This comparative example also provides a coated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The coated digital printed part is obtained by directly thermally compounding the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0094] Comparative Example 3

[0095] This comparative example provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resins of each layer of the low-noise digital printing adhesive-free film of this comparative example comprises the following steps:

[0096] Preparation of release functional layer resin: 98.5wt% homopolymer polypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 1.5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin. Preparation of core layer resin: 100wt% isotactic polypropylene (isotacticity of 95.5%, melt index of 3.8 g / 10min) was taken as core layer resin.

[0097] Preparation of tackifying hot melt adhesive layer resin: 99.8wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%) and 0.2wt% polysiloxane elastomer (particle size D50 of 5μm) were mixed evenly to obtain tackifying hot melt adhesive layer resin.

[0098] The preparation method of the low-noise adhesive-free film for digital printing in this comparative example is the same as that in Example 1, so it is not described in detail. The preparation method has a smooth process.

[0099] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0100] This comparative example also provides a coated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The coated digital printed part is obtained by directly thermally compounding the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0101] Comparative Example 4

[0102] This comparative example provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resins of each layer of the low-noise digital printing adhesive-free film of this comparative example comprises the following steps:

[0103] Preparation of release functional layer resin: 98.5wt% homopolymer polypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 1.5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin. Preparation of core layer resin: 100wt% isotactic polypropylene (isotacticity of 95.5%, melt index of 3.8 g / 10min) was taken as core layer resin.

[0104] Preparation of tackifying hot melt adhesive layer resin: 79.8wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%), 20wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 30wt%, long chain branching degree of 0.017 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and 0.2wt% polysiloxane elastomer (particle size D50 is 5μm) are evenly mixed to obtain a tackifying hot melt adhesive layer resin.

[0105] The preparation method of the low-noise digital printing adhesive-free film of this comparative example is the same as that of Example 1, so it is not described in detail. In this preparation method, the process is easy to stick to the roller, and the winding and unwinding are not smooth.

[0106] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 2 μm, the thickness of the core layer is 13 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0107] This comparative example also provides a coated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The coated digital printed part is obtained by directly thermally compounding the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0108] Comparative Example 5

[0109] This comparative example provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resins of each layer of the low-noise digital printing adhesive-free film of this comparative example comprises the following steps:

[0110] Preparation of release functional layer resin: 98.5wt% homopolymer polypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 1.5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin. Preparation of core layer resin: 100wt% isotactic polypropylene (isotacticity of 95.5%, melt index of 3.8 g / 10min) was taken as core layer resin.

[0111] Preparation of tackifying hot melt adhesive layer resin: 91.8wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%), 8wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 40wt%, long chain branching degree of 0.017 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and 0.2wt% polysiloxane elastomer (particle size D50 is 5μm) are evenly mixed to obtain a tackifying hot melt adhesive layer resin.

[0112] The preparation method of the low-noise digital printing adhesive-free film of this comparative example is the same as that of Example 1, so it is not described in detail. In this preparation method, the process is easy to stick to the roller, and the winding and unwinding are not smooth.

[0113] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0114] This comparative example also provides a coated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The coated digital printed part is obtained by directly thermally compounding the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0115] Comparative Example 6

[0116] This comparative example provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resins of each layer of the low-noise digital printing adhesive-free film of this comparative example comprises the following steps:

[0117] Preparation of release functional layer resin: 98.5wt% homopolymer polypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 1.5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin. Preparation of core layer resin: 100wt% isotactic polypropylene (isotacticity of 95.5%, melt index of 3.8 g / 10min) was taken as core layer resin.

[0118] Preparation of tackifying hot melt adhesive layer resin: 92wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%) and 8wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 30wt%, long chain branching degree of 0.017 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and mixed evenly to obtain a tackifying hot melt adhesive layer resin.

[0119] The preparation method of the low-noise digital printing adhesive-free film of this comparative example is the same as that of Example 1, so it is not described in detail. In this preparation method, the process is easy to stick to the roller, and the winding and unwinding are not smooth.

[0120] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0121] This comparative example also provides a coated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The coated digital printed part is obtained by directly thermally compounding the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0122] Comparative Example 7

[0123] This comparative example provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resins of each layer of the low-noise digital printing adhesive-free film of this comparative example comprises the following steps:

[0124] Preparation of release functional layer resin: 98.5wt% homopolymer polypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 1.5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin. Preparation of core layer resin: 100wt% isotactic polypropylene (isotacticity of 95.5%, melt index of 3.8 g / 10min) was taken as core layer resin.

[0125] Preparation of tackifying hot melt adhesive layer resin: 91.8wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%), 8wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 30wt%, long chain branching degree of 0.005 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and 0.2wt% polysiloxane elastomer (particle size D50 is 5μm) are evenly mixed to obtain a tackifying hot melt adhesive layer resin.

[0126] The preparation method of the low-noise adhesive-free film for digital printing in this comparative example is the same as that in Example 1, so it is not described in detail. The preparation method has a smooth process and smooth winding and unwinding.

[0127] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0128] This comparative example also provides a coated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The coated digital printed part is obtained by directly thermally compounding the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0129] Comparative Example 8

[0130] This comparative example provides a low-noise adhesive-free film for digital printing, including a release functional layer, a core layer and an adhesive hot melt adhesive layer arranged in sequence. The specific structure can be found in Figure 1 The method for preparing the resins of each layer of the low-noise digital printing adhesive-free film of this comparative example comprises the following steps:

[0131] Preparation of release functional layer resin: 98.5wt% homopolymer polypropylene (melt index of 3.8g / 10min, isotacticity of 95.5%) and 1.5wt% aminosilicone grafted polypropylene (melt index of 5g / 10min, grafting rate of aminosilicone of 1.5%) were mixed evenly to obtain release functional layer resin. Preparation of core layer resin: 100wt% isotactic polypropylene (isotacticity of 95.5%, melt index of 3.8 g / 10min) was taken as core layer resin.

[0132] Preparation of tackifying hot melt adhesive layer resin: 91.8wt% ethylene-vinyl acetate copolymer A (melt index of 20g / 10min, VA content of 20wt%), 8wt% ethylene-vinyl acetate copolymer B (melt index of 20g / 10min, VA content of 30wt%, long chain branching degree of 0.03 / 1000C, weight average molecular weight of ethylene-vinyl acetate copolymer B of 28×10 4 g / mol, molecular weight distribution index is 17) and 0.2wt% polysiloxane elastomer (particle size D50 is 5μm) are evenly mixed to obtain a tackifying hot melt adhesive layer resin.

[0133] The preparation method of the low-noise digital printing adhesive-free film of this comparative example is the same as that of Example 1, so it is not described in detail. In this preparation method, the process is easy to stick to the roller, and the winding and unwinding are not smooth.

[0134] The total thickness of the film is 20 μm, of which the thickness of the release functional layer is 1 μm, the thickness of the core layer is 14 μm, and the thickness of the tackifying hot melt adhesive layer is 5 μm.

[0135] This comparative example also provides a coated digital printed part, comprising a low-noise digital printing adhesive-free film and a digital printed part with heavy silicone oil arranged in sequence. The coated digital printed part is obtained by directly thermally compounding the low-noise digital printing adhesive-free film on the digital printed part under the conditions of 100°C, 10MPa, and 20m / min.

[0136] The performance tests of the low-noise digital printing adhesive-free films and coated digital printing of Examples 1 to 4 and Comparative Examples 1 to 8 are shown in Table 2 below.

[0137] Table 2

[0138]

[0139] It can be seen from Example 2 and Comparative Example 1 that if only ethylene-vinyl acetate copolymer B is added to the tackifying hot melt adhesive layer, and aminosilicone grafted polypropylene is not added to the release functional layer accordingly, the film cannot be produced smoothly, and the unwinding noise of the resulting film is large. It can be seen from Example 2 and Comparative Example 3 that if ethylene-vinyl acetate copolymer B is not added to the tackifying hot melt adhesive layer, the peeling strength between the non-adhesive film and the digital printed part will be too low. It can be seen from Example 2 and Comparative Example 6 that if polyorganosiloxane elastomer is not added to the tackifying hot melt adhesive layer, the film cannot be produced smoothly, and the unwinding noise of the resulting film is large. It can be seen that the technical effect of the present invention can only be achieved under the synergistic effect of the aminosilicone grafted polypropylene added to the release functional layer and the ethylene-vinyl acetate copolymer B and polyorganosiloxane elastomer added to the tackifying hot melt adhesive layer.

[0140] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. A low-noise adhesive-free film for digital printing, characterized in that: The invention comprises a release function layer, a core layer and a tackifying hot melt adhesive layer which are arranged in sequence, wherein the release function layer comprises 0.5-2.5wt% aminosilicone grafted polypropylene and homopolymer polypropylene, the surface energy of the release function layer is 24-26dyn / cm, the melt index of the aminosilicone grafted polypropylene is 5-10g / 10min, and the grafting rate of the aminosilicone is 1.5-2.5%; the core layer comprises homopolymer polypropylene; the tackifying hot melt adhesive layer comprises ethylene-vinyl acetate copolymer A, 5-10wt% ethylene-vinyl acetate copolymer B and 0.2-0.5wt% polyorganosiloxane Elastomer; the vinyl acetate content in the ethylene-vinyl acetate copolymer A is 20-25wt%; the long chain branching degree in the ethylene-vinyl acetate copolymer B is (0.01-0.02) / 1000C, the long chain specifically refers to the branched chain with C atoms ≥6, the vinyl acetate content in the ethylene-vinyl acetate copolymer B is 28-32wt%, the melt index of the ethylene-vinyl acetate copolymer A and the ethylene-vinyl acetate copolymer B are both 20-25g / 10min, and the weight average molecular weight of the ethylene-vinyl acetate copolymer B is (22-30)×10 4 g / mol, and the molecular weight distribution index of the ethylene-vinyl acetate copolymer B is 15-20.

2. The low-noise adhesive-free film for digital printing according to claim 1, characterized in that: The aminosilicone grafted polypropylene is prepared by condensation reaction of maleic anhydride grafted polypropylene and aminosilicone.

3. The low-noise adhesive-free film for digital printing according to claim 1, characterized in that: The tackifying hot melt adhesive layer further comprises 1.5-5wt% of rosin pentaerythritol ester, and the softening point of the rosin pentaerythritol ester is 80-90°C.

4. The low-noise adhesive-free film for digital printing according to claim 1, characterized in that: The particle size D50 of the polyorganosiloxane elastomer is 4-12 μm.

5. The low-noise adhesive-free film for digital printing according to claim 1, characterized in that: The homopolymer polypropylene in the release functional layer and the core layer is isotactic polypropylene, the isotacticity of the isotactic polypropylene is 95.5-97.5%, and the melt index is 2.8-3.8 g / 10 min.

6. The low-noise adhesive-free film for digital printing according to claim 1, characterized in that: The thickness of the release functional layer is 0.8-1.5 μm, the thickness of the tackifying hot melt adhesive layer is 2-10 μm, and the total thickness of the low-noise tackifying adhesive-free film for digital printing is 15-30 μm.

7. The low-noise adhesive-free film for digital printing according to claim 1, characterized in that: The surface of the tackifying hot melt adhesive layer is subjected to corona and / or flame treatment.

8. A method for preparing a low-noise adhesive-free film for digital printing according to any one of claims 1 to 7, characterized in that: The following steps are involved: The component raw materials of the release functional layer, the core layer, and the tackifying hot melt adhesive layer are put into the batching unit, and are co-extruded through the extruder after being measured. After passing through the flow channel distributor, they are merged in the three-layer die head, and then cooled by the chilled roller to form a resin sheet. The resin sheet is biaxially stretched to form a film. The film is cooled by air shower, and the thickness is controlled by the trimming machine. After the film is subjected to corona and / or flame treatment, it is harvested into a film mother roll. The film mother roll is subjected to aging treatment, slitting, packaging, and stored as a finished product.

9. The method for preparing a low-noise adhesive-free film for digital printing according to claim 8, characterized in that: Teflon coatings are provided on the surface of the feed trough of the tackifying hot melt adhesive layer of the extruder and on the surface of the stretching roller used in the biaxial stretching.

Images