A flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage, and a preparation method and application thereof

Abstract

The present application relates to a kind of strong ink adhesion, low shrinkage flexible heat shrinkable composite film and its preparation method and application, and the flexible heat shrinkable composite film includes upper surface layer, lower surface layer and the core layer being sandwiched between upper surface layer and lower surface layer, upper surface layer raw material includes PETG modified polyester chip, opening agent and slip agent, lower surface layer raw material includes PS chip and butadiene styrene resin chip, core layer raw material includes PETG polyester chip, PS chip, toughening agent and chain extender, the thickness of the strong ink adhesion, low shrinkage flexible heat shrinkable composite film is 20-60 μm.The preparation method of the present application is simple, conducive to industrial production, and the heat shrinkable composite film prepared has the advantages of PETG and PS heat shrinkable film, ink is more easily attached to the surface layer and is not easily deinked, has low shrinkage and good flexibility, does not delaminate, and can meet the market demand for low shrinkage flexible bottle body, especially suitable for thin bottle type packaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat-shrinkable composite film, in particular to a flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage force, and a preparation method and application thereof. BACKGROUND

[0002] PETG heat-shrinkable film is widely used for shrink labels of beverage bottles, daily necessities, cosmetics, electronic products and other containers with complex shapes due to its excellent mechanical properties, good shrinkability, environmental friendliness and low natural shrinkage rate during storage. However, as a copolyester, the conjugation of benzene ring and ester group in the molecular chain of PETG heat-shrinkable film makes the film less flexible, and the shrinked film is hard and brittle with a large shrinkage force. In actual use, the shrinkage force has no effect on bottles with large thickness, but people have higher and higher requirements for the outer packaging of high-end products, especially with the thinning and specialization of packaging bottles, the large shrinkage force can cause the deformation of label patterns or the deformation of the bottle. The shrinkage force of PS heat-shrinkable film is low, and the label and the container are well matched, which can be closely matched with containers of various shapes and can also meet the novel packaging with different shapes, and has good gloss and transparency. Its performance is suitable for thin bottle packaging. However, the strength of PS heat-shrinkable film is low, the toughness is poor, and it is easy to cause label cracking during use, and special ink and solvent must be used for printing. Therefore, it is urgent to provide a heat-shrinkable composite film to avoid the disadvantages of single PETG heat-shrinkable film and PS heat-shrinkable film, and to have the advantages of both PETG and PS heat-shrinkable film to meet the market demand for low shrinkage force flexible bottles. With the personalization of packaging film printing, the layering of printed patterns and the strengthening of three-dimensional effect, light screen printing is often used, but when PETG material is used as the printing surface layer in ordinary composite film, light screen printing often loses points and causes ink bleeding. In order to overcome this problem, the PETG material for the printing layer needs to be modified to increase the surface tension of the surface layer, so that the surface layer has strong ink adhesion to achieve the effect of no point loss and no ink bleeding in light screen printing. Therefore, it is urgent to provide a flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage force to meet the market demand.

[0003] Therefore, the present application is proposed. SUMMARY

[0004] The present application aims to provide a flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage force, a preparation method and application thereof, which adopts a three-layer film structure design, the upper surface layer A is modified by glycidyl methacrylate (GMA) PETG polyester chips, which can improve the polarity of the molecular chain of PETG, so that the ink adhesion of the upper surface layer A is strong and easy to print; the lower surface layer C includes PS chips and butadiene styrene resin chips, the flexible chain segment butadiene in the butadiene styrene resin molecules can give the film high shrinkage, better softness and hand feeling, and low shrinkage force; the core layer B includes PETG polyester chips, PS chips, toughening agent and chain extender, so as to ensure low shrinkage force, and also benefit the interlayer adhesion of the three layers, solving the interlayer peeling problem of the label during heat shrinkage.

[0005] The present application is realized by the following technical scheme, a flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage force according to the present application, which comprises an upper surface layer, a lower surface layer and a core layer sandwiched between the upper surface layer and the lower surface layer, the raw materials of the upper surface layer include PETG modified polyester chips, opening agent and slip agent, and the mass percentage of the PETG modified polyester chips, opening agent and slip agent is (96-98)%:(1-3)%:(1-3)%; the raw materials of the lower surface layer include PS chips and butadiene styrene resin chips, and the mass percentage of the PS chips and butadiene styrene resin chips is (90-98)%:(2-10)%; the raw materials of the core layer include PETG polyester chips, PS chips, toughening agent and chain extender, and the mass percentage of the PETG polyester chips, PS chips, toughening agent and chain extender is (50-65)%:(34-49)%:0.5%:0.5%, the thickness of the flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage force is 20-60μm, wherein the upper surface layer is used as a printing layer.

[0006] Further, the PETG modified polyester chips are obtained by chemical reaction of PETG raw materials and glycidyl methacrylate (GMA) in a high-pressure reaction kettle, specifically including: adding PETG raw materials and GMA accounting for (2-8)% of the mass percentage of PETG into the reaction kettle, stirring at a speed of 120-180rpm for 10-15min, raising the temperature in the reaction kettle to 275-285℃, reducing the pressure to 100Pa, and reacting for 1-2h under the above conditions to obtain a polymer melt, which is extruded, granulated and dried to obtain the PETG modified polyester chips. The active acrylate double bond in GMA can improve the polarity of the molecular chain of PETG, and the obtained PETG modified polyester chips as a printing layer have improved surface polarity, reduced surface contact angle, better hydrophilic property, and ink more easily adhered to the surface and less prone to ink bleeding.

[0007] Preferably, the opening agent is selected from one of alumina, mica powder, kaolin, and silicon dioxide, the slip agent is selected from one of stearic acid amide, oleic acid amide, and erucic acid amide, the toughening agent is selected from one of ethylene-vinyl acetate copolymer and polymethyl methacrylate, the chain extender is selected from one of phthalic anhydride and pyromellitic dianhydride, and the butadiene-styrene resin is selected from one of Asahi Kasei Asaflex 810, BASF Styrolux 684D, and BASF 2G66.

[0008] Further, the flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage has a shrinkage force less than 2.9 N, stable other performance indexes, a longitudinal tensile strength of 46-60 MPa, a transverse tensile strength of 150-200 MPa, a longitudinal elongation at break of 410-470%, a transverse elongation at break of 33-42%, a longitudinal elastic modulus of 1320-1740 MPa, and a transverse elastic modulus of 2240-2680 MPa.

[0009] The application further provides a preparation method of the flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage.

[0010] (1) The upper surface layer raw material, the core layer raw material, and the lower surface layer raw material are respectively put into corresponding high-speed mixers, stirred and uniformly mixed at room temperature to obtain the upper surface layer mixed raw material, the core layer mixed raw material, and the lower surface layer mixed raw material; the rotation speed of the high-speed mixer is 400-600 rpm, and the stirring time is 5-10 min.

[0011] The upper surface layer raw material comprises PETG modified polyester chips, an opening agent, and a slip agent, and the mass percentage of the PETG modified polyester chips, the opening agent, and the slip agent is (96-98)%: (1-3)%: (1-3)%; the lower surface layer raw material comprises PS chips and butadiene-styrene resin chips, and the mass percentage of the PS chips and the butadiene-styrene resin chips is (90-98)%: (2-10)%; and the core layer raw material comprises PETG polyester chips, PS chips, a toughening agent, and a chain extender, and the mass percentage of the PETG polyester chips, the PS chips, the toughening agent, and the chain extender is (50-65)%: (34-49)%: 0.5%: 0.5%.

[0012] (2) The raw materials of each layer are respectively put into the corresponding twin-screw vacuum extruder to melt and plasticize to obtain the melt of each layer, the temperature of the twin-screw vacuum extruder is controlled at 240-265℃, the mass ratio of the melt of the upper surface layer, the core layer and the lower surface layer is adjusted to 1:(1-10):1 by adjusting the rotating speed of the extruder; after the melt of each layer is filtered to remove impurities by a precision filter, the melt is respectively sent to the die head of three different flow channels through a melt distribution system, the three different flow channels correspond to the melt of the upper surface layer, the melt of the core layer and the melt of the lower surface layer respectively, the three kinds of melt are combined and extruded at the die head and then rapidly cooled by a quenching roller to obtain a cast sheet, the extrusion temperature of the die head is 240-265℃;

[0013] (3) The cast sheet is stretched in two directions to form a film, first stretched longitudinally, then stretched transversely, finally, after shaping, cooling and winding, a flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage is obtained.

[0014] Preferably, in step (1), the mass percentage of PETG modified polyester chips, opening agent and slip agent in the raw material of the upper surface layer is (96-98)%:(1-3)%:(1-3)%; the mass percentage of PS chips and butylphenyl resin chips in the raw material of the lower surface layer is (90-98)%:(2-10)%; the mass percentage of PETG polyester chips, PS chips, toughening agent and chain extender in the raw material of the core layer is (50-65)%:(34-49)%:0.5%:0.5%.

[0015] Further, the PETG modified polyester chips in step (1) are obtained by chemical reaction of PETG raw material and GMA in a high-pressure reaction kettle, specifically including: adding PETG raw material and GMA accounting for (2-8)% of the mass percentage of PETG into the reaction kettle, stirring at a speed of 120-180 rpm for 10-15 min, raising the temperature in the reaction kettle to 275-285℃, reducing the pressure to 100 Pa, and reacting for 1-2 h under the above conditions to obtain a polymer melt, which is then extruded, granulated and dried to obtain the PETG modified polyester chips.

[0016] Preferably, in step (1), the opening agent is selected from one of alumina, mica powder, kaolin and silicon dioxide, the slip agent is selected from one of stearic acid amide, oleic acid amide and erucic acid amide; the toughening agent is selected from one of ethylene-vinyl acetate copolymer and polymethyl methacrylate, the chain extender is selected from one of phthalic anhydride and pyromellitic dianhydride, and the butylphenyl resin is selected from one of Asahi Chemical Asaflex 810, BASF Styrolux 684D and BASF 2G66.

[0017] Preferably, in step (2), the temperature of the quenching roller is 25-30℃, and the linear speed of rotation is 70-80 m / min.

[0018] Preferably, the longitudinal stretching conditions in step (3) are: preheating temperature 85-100℃, stretching temperature 85-95℃, stretching multiple 1.0-2.0, and cooling setting temperature 70-90℃; and the transverse stretching conditions are: preheating temperature 85-100℃, stretching temperature 80-100℃, stretching multiple 4.0-6.0, and cooling setting temperature 70-90℃.

[0019] The flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage force provided by the present application is particularly suitable for thin bottle type packaging, wherein the upper surface layer is used as a printing layer.

[0020] Compared with the prior art, the present application has obvious advantages and beneficial effects. By means of the above technical scheme, the present application can achieve considerable technical progress and practicability, and has wide utilization value, and at least has the following advantages:

[0021] (1) The present application adopts a three-layer film structure design, the upper surface layer A is made of GMA modified PETG polyester chips, the high active acrylate double bond in GMA can improve the polarity of the PETG molecular chain, and the obtained PETG modified polyester chips, as a printing layer, can improve the surface polarity of the film, reduce the surface contact angle, and have better hydrophilic property, so that the ink is more easily attached to the surface layer and is not easy to be removed. The lower surface layer C includes PS chips and butadiene styrene resin chips, the flexible chain segment butadiene in the butadiene styrene resin molecules can give the film high shrinkage rate, better softness and hand feeling, and low shrinkage force; the core layer B includes PETG polyester chips, PS chips, toughening agent and chain extender, which can form good compatibility with the PETG polyester chips in the upper surface layer and the PS chips in the lower surface layer during the melt film forming process, improve the adhesion of the core layer to the upper and lower surface layers, thereby ensuring low shrinkage force, and also benefiting the interlayer adhesion of the three layers, solving the problem of interlayer peeling of the label during heat shrinkage.

[0022] (2) The preparation method of the present application is simple, efficient, and beneficial to industrial production. The flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage force prepared by the present application has the advantages of PETG and PS heat-shrinkable film, can meet the market demand for low shrinkage force flexible bottle body, solves the problems of missing points and ink removal in light screen printing when PETG material is used as a printing surface layer by GMA modified PETG; the lower surface layer uses PS chips and butadiene styrene resin chips to reduce the shrinkage force of the film while ensuring the shrinkage rate; the core layer uses PETG polyester chips and PS chips to reduce the shrinkage force while facilitating the interlayer combination. The flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage force prepared by the present application has excellent performance, and is particularly suitable for thin bottle type packaging. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1It is a structural schematic diagram of the flexible heat shrinkage composite film with strong ink adhesion and low shrinkage prepared by the application; wherein, A is an upper surface layer, B is a core layer, and C is a lower surface layer. DETAILED DESCRIPTION

[0024] To make the purpose, technical solutions and advantages of the embodiments of the application clearer, the technical solutions of the application will be described clearly and completely below in combination with specific embodiments. Obviously, the described embodiments are some of the embodiments of the application, rather than all the embodiments. Based on the embodiments of the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0025] Embodiment 1

[0026] A flexible heat shrinkage composite film with strong ink adhesion and low shrinkage comprises an upper surface layer A, a core layer B and a lower surface layer C arranged in layers, wherein the raw materials of each layer comprise:

[0027] The upper surface layer comprises 98wt% PETG modified polyester chips, 1wt% opening agent and 1wt% slip agent; the opening agent is selected from silica; and the slip agent is selected from oleic acid amide;

[0028] The core layer comprises 50wt% PS chips, 49wt% PETG polyester chips, 0.5wt% toughening agent and 0.5wt% chain extender; the toughening agent is selected from ethylene-vinyl acetate copolymer; and the chain extender is selected from pyromellitic dianhydride;

[0029] The lower surface layer comprises 94wt% PS chips and 6wt% butyl benzene resin; the butyl benzene resin is selected from BASF Styrolux 684D.

[0030] The preparation process of the flexible heat shrinkage composite film with strong ink adhesion and low shrinkage comprises the following steps:

[0031] (1) The raw materials of the upper surface layer, the core layer and the lower surface layer are respectively put into corresponding high-speed mixers, and stirred at 500rpm for 5min at room temperature to obtain the mixed raw materials of the upper surface layer, the core layer and the lower surface layer, respectively;

[0032] (2) The raw materials of each layer are respectively fed into the corresponding twin-screw vacuum extruder for melting and plasticizing to obtain the melt of each layer. The temperature of the twin-screw vacuum extruder is controlled at 240-265℃. The mass ratio of the melt of the upper surface layer, the core layer and the lower surface layer is adjusted to 1:8:1 by adjusting the rotating speed of the extruder. After the melt of each layer is filtered to remove impurities by a precision filter, the melt is respectively fed into the die of three different flow channels through a melt distribution system. The three flow channels correspond to the upper surface layer, the core layer and the lower surface layer respectively. The three kinds of molten polymers (i.e. the melt) are combined and extruded at the die, and then rapidly cooled by a quenching roller to obtain a cast sheet. The extrusion temperature of the die is controlled at 245℃. The temperature of the quenching roller is controlled at 25-30℃ during the quenching process, and the linear speed of the rotating quenching roller is 75 m / min.

[0033] (3) The cast sheet is stretched in two directions to form a film. The film is first stretched in the longitudinal direction and then stretched in the transverse direction. The longitudinal stretching conditions are as follows: the preheating temperature is 90℃, the stretching temperature is 90℃, the stretching multiple is 1.0, and the cooling and setting temperature is 80℃. The transverse stretching conditions are as follows: the preheating temperature is 90℃, the stretching temperature is 90℃, the stretching multiple is 4.5, and the cooling and setting temperature is 75℃. After the film is set, cooled and wound, a flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage is obtained, and the thickness of the film is 45μm.

[0034] Example 2

[0035] A flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage, comprising an upper surface layer A, a core layer B and a lower surface layer C arranged in layers, wherein the raw materials of each layer comprise:

[0036] The upper surface layer comprises 98wt% PETG modified polyester chips, 1wt% opening agent and 1wt% slip agent. The opening agent is mica powder, and the slip agent is oleic acid amide.

[0037] The core layer comprises 55wt% PS chips, 44wt% PETG polyester chips, 0.5wt% toughening agent and 0.5wt% chain extender. The toughening agent is polymethyl methacrylate, and the chain extender is pyromellitic dianhydride.

[0038] The lower surface layer comprises 94wt% PS chips and 6wt% butyl benzene resin. The butyl benzene resin is BASF Styrolux 684D.

[0039] The preparation process is as described in Example 1. The flexible heat-shrinkable composite film obtained in this example has a thickness of 45μm.

[0040] Example 3

[0041] A flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage, comprising an upper surface layer A, a core layer B and a lower surface layer C arranged in layers, wherein the raw materials of each layer comprise:

[0042] Upper surface layer: 98wt% PETG modified polyester chips, 1wt% opening agent, 1wt% slip agent; the opening agent is selected from kaolin; the slip agent is selected from oleic acid amide;

[0043] Core layer: 60wt% PS chips, 39wt% PETG polyester chips, 0.5wt% toughening agent, 0.5wt% chain extender; the toughening agent is selected from polymethyl methacrylate; the chain extender is selected from pyromellitic dianhydride;

[0044] Lower surface layer: 94wt% PS chips, 6wt% butadiene styrene resin, the butadiene styrene resin is selected from BASF Styrolux 684D.

[0045] The preparation process is as in Example 1, and the flexible heat-shrinkable composite film obtained in the embodiment has a thickness of 45μm.

[0046] Example 4

[0047] A flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage, comprising an upper surface layer A, a core layer B and a lower surface layer C arranged in layers, wherein the raw materials of each layer comprise:

[0048] Upper surface layer: 98wt% PETG modified polyester chips, 1wt% opening agent, 1wt% slip agent; the opening agent is selected from kaolin; the slip agent is selected from oleic acid amide;

[0049] Core layer: 65wt% PS chips, 34wt% PETG polyester chips, 0.5wt% toughening agent, 0.5wt% chain extender; the toughening agent is selected from polymethyl methacrylate; the chain extender is selected from pyromellitic dianhydride;

[0050] Lower surface layer: 94wt% PS chips, 6wt% butadiene styrene resin, the butadiene styrene resin is selected from BASF Styrolux 684D.

[0051] The preparation process is as in Example 1, and the flexible heat-shrinkable composite film obtained in the embodiment has a thickness of 45μm.

[0052] Example 5

[0053] A flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage, comprising an upper surface layer A, a core layer B and a lower surface layer C arranged in layers, wherein the raw materials of each layer comprise:

[0054] Upper surface layer: 98wt% PETG modified polyester chips, 1wt% opening agent, 1wt% slip agent; the opening agent is selected from kaolin; the slip agent is selected from oleic acid amide;

[0055] Core layer: 60wt% PS chip, 39wt% PETG polyester chip, 0.5wt% toughening agent, 0.5wt% chain extender; the toughening agent is selected from polymethyl methacrylate; the chain extender is selected from pyromellitic dianhydride;

[0056] Lower surface layer: 98wt% PS chip, 2wt% butadiene styrene resin, and the butadiene styrene resin is selected from BASF Styrolux 684D.

[0057] The preparation process is as shown in Embodiment 1, and the flexible heat-shrinkable composite film obtained in the embodiment has a thickness of 45μm.

[0058] Embodiment 6

[0059] A flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage, comprising an upper surface layer A, a core layer B and a lower surface layer C arranged in layers, wherein the raw materials of each layer comprise:

[0060] Upper surface layer: 98wt% PETG modified polyester chip, 1wt% opening agent, 1wt% slip agent; the opening agent is selected from mica powder; the slip agent is selected from oleic acid amide;

[0061] Core layer: 60wt% PS chip, 39wt% PETG polyester chip, 0.5wt% toughening agent, 0.5wt% chain extender; the toughening agent is selected from polymethyl methacrylate; the chain extender is selected from pyromellitic dianhydride;

[0062] Lower surface layer: 96wt% PS chip, 4wt% butadiene styrene resin, and the butadiene styrene resin is selected from BASF 2G66.

[0063] The preparation process is as shown in Embodiment 1, and the flexible heat-shrinkable composite film obtained in the embodiment has a thickness of 45μm.

[0064] Embodiment 7

[0065] A flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage, comprising an upper surface layer A, a core layer B and a lower surface layer C arranged in layers, wherein the raw materials of each layer comprise:

[0066] Upper surface layer: 98wt% PETG modified polyester chip, 1wt% opening agent, 1wt% slip agent; the opening agent is selected from mica powder; the slip agent is selected from oleic acid amide;

[0067] Core layer: 60wt% PS chip, 39wt% PETG polyester chip, 0.5wt% toughening agent, 0.5wt% chain extender; the toughening agent is selected from polymethyl methacrylate; the chain extender is selected from pyromellitic dianhydride;

[0068] Lower surface layer: 92wt% PS chip, 8wt% butylphenyl resin, butylphenyl resin is selected from BASF Styrolux 684D.

[0069] The preparation process is as in Example 1, and the flexible heat-shrinkable composite film obtained in the example has a thickness of 45 μm.

[0070] Example 8

[0071] A flexible heat-shrinkable composite film with strong ink adhesion and low shrinkage, comprising an upper surface layer A, a core layer B and a lower surface layer C arranged in layers, wherein the raw materials of each layer comprise:

[0072] Upper surface layer: 98wt% PETG modified polyester chip, 1wt% opening agent, 1wt% slip agent; the opening agent is selected from alumina; the slip agent is selected from stearic acid amide;

[0073] Core layer: 60wt% PS chip, 39wt% PETG polyester chip, 0.5wt% toughening agent, 0.5wt% chain extender; the toughening agent is selected from ethylene-vinyl acetate copolymer; the chain extender is selected from pyromellitic dianhydride;

[0074] Lower surface layer: 90wt% PS chip, 10wt% butylphenyl resin, butylphenyl resin is selected from Asakura Asaflex 810.

[0075] The preparation process is as in Example 1, and the flexible heat-shrinkable composite film obtained in the example has a thickness of 45 μm.

[0076] Comparative Example 1

[0077] A heat-shrinkable composite film, comprising an upper surface layer A, a core layer B and a lower surface layer C arranged in layers, wherein the raw materials of each layer comprise:

[0078] Upper surface layer: 98wt% PETG polyester chip, 1wt% opening agent, 1wt% slip agent; the opening agent is selected from silicon dioxide; the slip agent is selected from oleic acid amide;

[0079] Core layer: 60wt% PS chip, 39wt% PETG polyester chip, 0.5wt% toughening agent, 0.5wt% chain extender; the toughening agent is selected from polymethyl methacrylate; the chain extender is selected from pyromellitic dianhydride;

[0080] Lower surface layer C: 98wt% PETG polyester chip, 1wt% opening agent, 1wt% slip agent, the opening agent is selected from silicon dioxide; the slip agent is selected from oleic acid amide.

[0081] The preparation process is as in Example 1, and the flexible heat-shrinkable composite film obtained in the example has a thickness of 45 μm.

[0082] Comparative Example 2

[0083] A heat-shrinkable composite film comprises an upper surface layer A, a core layer B and a lower surface layer C arranged in layers, wherein the raw materials of each layer comprise:

[0084] The upper surface layer comprises 94wt% PS chips and 6wt% butadiene styrene resin, and the butadiene styrene resin is selected from BASF Styrolux 684D;

[0085] The core layer comprises 60wt% PS chips, 39wt% PETG polyester chips, 0.5wt% toughening agent and 0.5wt% chain extender, wherein the toughening agent is selected from polymethyl methacrylate, and the chain extender is selected from pyromellitic dianhydride;

[0086] The lower surface layer comprises 94wt% PS chips and 6wt% butadiene styrene resin, and the butadiene styrene resin is selected from BASF Styrolux 684D.

[0087] The preparation process is as in Embodiment 1, and the thickness is 45μm.

[0088] The ink adhesion test is performed by using the cross-hatch test method, and the cross-hatch (1mm×1mm) is cut on the ink-printed surface of the film, and the cross-hatch is adhered with 3M tape, and there is no bubble, and the cross-hatch is pulled off once, and the number of cross-hatches falling off the tape is checked. The results are as follows: in Embodiments 1-8, the surface appearance of the cross-cut area is smooth, and almost no ink falls off; compared with Embodiment 1, in Comparative Example 1, the ink falls off at the cross-cut area and the edge, and the affected cross-cut area is about 5%; compared with Embodiment 1, in Comparative Example 2, the ink falls off at the cross-cut area and the edge, and the affected cross-cut area is about 10%.

[0089] The properties of the composite films obtained in Embodiments 1-8 and Comparative Examples 1-2 are tested, and the results are shown in Table 1. The shrinkage force test method is as follows: the film heat shrinkage performance tester is used, the composite film sample is cut into a long strip with a width of 15mm and a length of 150mm (the shrinkage direction), and is clamped on the sample clamping device, and the sample is heated and shrunk in the test cavity after reaching the set temperature of 50℃, and the sample is taken out of the cavity when the measured shrinkage force value reaches the out-of-cavity condition, and the maximum force value measured in the cavity during heating is the heat shrinkage force, i.e. the shrinkage force of the present application. The test methods of the other properties are all known techniques in the art, and are not described herein.

[0090] Table 1 Main performance parameters of the heat-shrinkable composite films prepared in the embodiments and comparative examples

[0091]

[0092] It can be seen from the above table that the flexible heat-shrinkable composite film provided by the application has a strong ink adhesion force, a shrinkage force less than 2.9 N, a longitudinal tensile strength of 46-60 MPa, a transverse tensile strength of 150-200 MPa, a longitudinal elongation at break of 410-470%, a transverse elongation at break of 33-42%, a longitudinal elastic modulus of 1320-1740 MPa, and a transverse elastic modulus of 2240-2680 MPa. On the basis of ensuring good performance indexes, the flexible heat-shrinkable composite film can have a strong ink adhesion force, no delamination, low shrinkage force, and low shrinkage rate, and is especially suitable for thin bottle type packaging.

[0093] The above description is only an embodiment of the application and does not limit the application in any form. The application can have other forms of embodiments according to the above structure and function, and the above embodiments are not listed one by one. Therefore, any skilled person in the art can make any simple modification, equivalent change and modification to the above embodiments according to the technical essence of the application without departing from the scope of the technical scheme of the application.

Claims

1. A flexible heat-shrinkable composite film having strong ink adhesion and low shrinkage, characterized by The upper surface layer, the lower surface layer and the core layer sandwiched between the upper surface layer and the lower surface layer; The upper surface layer raw material comprises PETG modified polyester chips, opening agent and slip agent, and the mass percentage of the PETG modified polyester chips, the opening agent and the slip agent is (96-98)%:(1-3)%:(1-3)%; the PETG modified polyester chips are prepared by the following method: PETG raw material and glycidyl methacrylate accounting for (2-8)% of the mass percentage of the PETG are added into a reaction kettle, the temperature in the reaction kettle is raised to 275-285 DEG C after stirring for 10-15 min, the pressure is reduced to 100 Pa, and the polymer melt is obtained after reacting for 1-2 h under the above conditions, and then the polymer melt is extruded, cut into particles and dried to obtain the PETG modified polyester chips; The lower surface layer raw material comprises PS chips and butyl benzene resin chips, and the mass percentage of the PS chips and the butyl benzene resin chips is (90-98)%:(2-10)%; The core layer raw material comprises PETG polyester chips, PS chips, toughening agent and chain extender, and the mass percentage of the PETG polyester chips, the PS chips, the toughening agent and the chain extender is (50-65)%:(34-49)%:0.5%:0.5%; The flexible heat shrinkage composite film with strong ink adhesion and low shrinkage force has a thickness of 20-60 μm, a shrinkage force of less than 2.9 N, a longitudinal tensile strength of 46-60 MPa, a transverse tensile strength of 150-200 MPa, a longitudinal elongation at break of 410-470%, a transverse elongation at break of 33-42%, a longitudinal elastic modulus of 1320-1740 MPa and a transverse elastic modulus of 2240-2680 MPa.

2. The flexible heat shrinkable composite film of claim 1, wherein The opening agent is selected from one of alumina, mica powder, kaolin and silicon dioxide, the slip agent is selected from one of stearic amide, oleic amide and erucic amide, the toughening agent is selected from one of ethylene-vinyl acetate copolymer and polymethyl methacrylate, the chain extender is selected from one of phthalic anhydride and pyromellitic dianhydride, and the butyl benzene resin is selected from one of Asahi Chemical Asaflex 810, BASF Styrolux 684D and BASF 2G66.

3. The flexible heat shrinkable composite film of claim 1, wherein The PETG modified polyester chips are prepared by the following method: (1) the upper surface layer raw material, the core layer raw material and the lower surface layer raw material are respectively put into corresponding high-speed mixers, and are stirred and uniformly mixed at room temperature to obtain the upper surface layer mixed raw material, the core layer mixed raw material and the lower surface layer mixed raw material; the rotation speed of the high-speed mixer is 400-600 rpm, and the stirring time is 5-10 min; (2) The raw materials of each layer are put into the corresponding twin-screw vacuum extruder to melt and plasticize to obtain the melt of each layer, the temperature of the twin-screw vacuum extruder is controlled at 240-265℃, the mass ratio of the melt of the upper surface layer, the core layer and the lower surface layer is adjusted to 1:(1-10):1 by adjusting the rotating speed of the extruder; the melt of each layer is filtered by the precision filter to remove impurities, and then is sent into the die head of three different flow channels through the melt distribution system, the three different flow channels correspond to the melt of the upper surface layer, the melt of the core layer and the melt of the lower surface layer respectively, the three kinds of melt are combined and extruded at the die head, and then are rapidly cooled by the quenching roller to obtain the cast sheet, the extrusion temperature of the die head is 240-265℃; (3) The cast sheet is stretched in two directions to form a film, first stretched longitudinally, then stretched transversely, finally, after shaping, cooling and winding, a flexible heat shrinkage composite film with strong ink adhesion and low shrinkage is obtained.

4. The flexible heat shrinkable composite film of claim 3, wherein The opening agent is selected from one of alumina, mica powder, kaolin and silicon dioxide, the slip agent is selected from one of stearic acid amide, oleic acid amide and erucic acid amide; the toughening agent is selected from one of ethylene-vinyl acetate copolymer and polymethyl methacrylate, the chain extender is selected from one of phthalic anhydride and pyromellitic dianhydride, and the butylphenyl resin is selected from one of Asaflex 810 of Asahi Kasei, Styrolux 684D of BASF and 2G66 of BASF.

5. The flexible heat shrinkable composite film of claim 3, wherein the ink has a high adhesion force and a low shrinkage force. The temperature of the quenching roller in step (2) is 25-30℃, and the rotating linear speed is 70-80m / min.

6. The flexible heat shrinkable composite film of claim 3, wherein the ink has a high adhesion force and a low shrinkage force. In step (3), the longitudinal stretching conditions are: preheating temperature 85-100℃, stretching temperature 85-95℃, stretching multiple 1.0-2.0, and cooling and shaping temperature 70-90℃; the transverse stretching conditions are: preheating temperature 85-100℃, stretching temperature 80-100℃, stretching multiple 4.0-6.0, and cooling and shaping temperature 70-90℃.

7. Use of the flexible heat-shrinkable composite film of claim 1 having strong ink adhesion and low shrinkage in thin bottle type packaging, wherein, The upper surface layer is used as a printing layer.

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