A kind of PETG heat shrinkable label film of easy tearing type and preparation method

Abstract

The application relates to the field of shrink film sleeve labels, in particular to an easy-to-tear PETG heat-shrinkable label film and a preparation method. The easy-to-tear PETG heat-shrinkable label film comprises a core layer and two surface layers, the core layer is located between the two surface layers, the core layer comprises the following components in parts by mass: PETG 94.8-90.6 parts, PLA 5.0-9.0 parts, ultraviolet light initiator DEAP 0.2-0.4 parts; the surface layer comprises the following components in parts by mass: PETG 98-98.5 parts, opening smooth master batch 2.0-1.5 parts. Based on the characteristics that the mechanical properties of the high polymer material decrease after degradation, and the film easy-to-tear performance is enhanced, the method of combining photodegradation and biodegradation is adopted to form specific degradation longitudinal narrow strips on the PETG heat-shrinkable label film, so that the technical effect of easy-to-tear of the PETG heat-shrinkable label film is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of shrink film sleeve labels, in particular to an easy-to-tear PETG heat shrink label film and a preparation method thereof. BACKGROUND

[0002] PETG (polyethylene terephthalate-1,4-cyclohexane dimethyl ester) heat shrink label film is environmentally friendly and non-toxic, has higher shrinkage and mechanical strength compared with PVC (polyvinyl chloride) heat shrink label film, and has good transparency, excellent printing performance, strong storage and transportation environment adaptability, and has become the main variety of shrink label base film.

[0003] Although both PETG labels and PET (polyethylene terephthalate) bottles are PET polyester materials, there are obvious differences in structure and performance between them. PETG is a copolymer modified variety of PET, and has a third, even a fourth copolymer monomer segment in its molecular structure. Compared with PET, the crystallinity of PETG is greatly reduced, and the melting point and softening point are also reduced. In addition, there is printing ink residue on the label during waste disposal, so the two cannot be recycled together and need to be peeled off from the PET bottle first and then disposed of separately. Since the shrink label is in the form of a cylinder wrapped around the bottle and tightly shrunk to the bottle, and the mechanical strength of PETG material is high, the existing PETG label has the problem of not being easy to separate from the PET bottle.

[0004] Currently, in the field of film technology, the commonly used methods to make the film easy to tear include:

[0005] 1. Designing an easy-to-tear line using a highly molecularly oriented strip structure in the film, and tearing the film through the easy-to-tear line. However, for PETG shrink label film, during the preparation process, in order to obtain high shrinkage, highly molecular orientation (stretching) is performed in the transverse direction, so it has transverse easy-to-tear properties. The shrink label is wrapped around the bottle in 360 degrees, and the longitudinal tearing property is required for peeling off from the bottle, and the transverse tearing property of the label cannot solve the problem of not being easy to tear off. More importantly, during the labeling process, the label film shrinks under heat, and the highly molecular orientation is lost, and the easy-to-tear property of the original film also disappears. Therefore, for PETG heat shrink label film, the design of this highly molecularly oriented easy-to-tear line structure is not feasible.

[0006] 2. For packaging films (such as bags), V-shaped tear-offs can be punched on one or both sides, or the film edges can be cut into serrated edges, allowing the film to be torn open through the V-shaped tear-off or serrated edges. This method is also unsuitable for heat-shrink label films because: heat-shrink label films require printing, cutting, folding, punching, and labeling (shrinking) processes before becoming the labels on the bottles. Before labeling, they are processed continuously in rolls, and only during the labeling process are they cut into individual labels. There is no space or possibility to create such tear-offs in the entire post-processing stage of the label. If tear-offs are forcibly punched on the edges of each label, creating numerous "holes" on the label film roll, the roll will break during post-processing due to reduced strength, failing to meet the requirements of high-speed automated production.

[0007] 3. Easy-tear lines are cut into the film using laser technology or easy-tear perforations are punched into the film using a punching machine to make it easy to tear. While this method is applicable to heat-shrink label films and has been used on some other label films, it requires an additional punching or laser cutting process in downstream applications, increasing equipment investment and production costs. Therefore, it has not yet been widely adopted. Summary of the Invention

[0008] To address the aforementioned issues, this application provides an easy-tear PETG heat-shrinkable label film and its preparation method. Based on the characteristic that the mechanical properties of polymer materials decrease after degradation, but the film's tearability increases, this application employs a combination of photodegradation and biodegradation to form specific longitudinal narrow degradation strips on the PETG heat-shrinkable label film, thereby achieving the technical effect of easy tearing of the PETG heat-shrinkable label film.

[0009] To achieve the above technical objectives, one technical solution of this application is:

[0010] An easy-tear PETG heat-shrink label film includes a core layer and two surface layers, wherein the core layer is located between the two surface layers, and the core layer includes the following components by weight: 94.8-90.6 parts PETG, 5.0-9.0 parts PLA, and 0.2-0.4 parts UV photoinitiator DEAP; the surface layers include the following components by weight: 98-98.5 parts PETG and 2.0-1.5 parts opening slip masterbatch.

[0011] Preferably, the core layer comprises the following components by weight: 92.7 parts PETG, 7.0 parts PLA, and 0.3 parts UV photoinitiator DEAP; the surface layer comprises the following components by weight: 98 parts PETG and 2.0 parts open slip masterbatch.

[0012] The above technical solution has the following advantages:

[0013] In the core layer of the PETG heat shrinkable label film main body, a certain amount of photoinitiator and bioplastic PLA are added, PET is blended with PLA, the natural degradation of PET / PLA blended film material can be driven by the degradation of PLA itself, so that the molecular weight of the film material is reduced, the mechanical properties are reduced, and the tearability is enhanced. After the film material is treated by ultraviolet irradiation, the mechanical properties of the film material are reduced due to the photodegradation, and a certain amount of free radicals are also left in the material, which will further accelerate the natural degradation reaction of the PETG / PLA blended film material, so that the mechanical properties of the film material in the treatment area are continuously reduced due to degradation, and the easy tearability is further enhanced.

[0014] To achieve the above technical purposes, the application also provides a preparation method of the easy-to-tear PETG heat shrinkable label film.

[0015] S101, the core layer raw materials and the surface layer raw materials are respectively weighed according to the formula proportion;

[0016] S102, the core layer raw materials and the surface layer raw materials are respectively added into the extruder for plasticization, and then filtered through the filter;

[0017] S103, the filtered material is fed to the T-shaped die casting through the distributor according to the required stacking mode, and then wound after being cooled by the chill roll, stretched in the transverse direction, and degraded by ultraviolet irradiation, to obtain the easy-to-tear PETG heat shrinkable label film roll material.

[0018] Preferably, in step S102, the plasticization temperature of the extruder is 245-270℃.

[0019] Preferably, in step S103, the temperature of the T-shaped die is 265-270℃.

[0020] Preferably, in step S103, the water temperature for cooling the casting roll is 25-32℃.

[0021] Preferably, in step S103, the stretching ratio of the transverse stretching is 1:4-1:6, and the stretching working area includes a preheating zone, a stretching zone, a setting zone and a cooling zone. The temperature of the preheating zone is 90-110℃, the temperature of the stretching zone is 85-95℃, the temperature of the setting zone is 70-82℃, and the temperature of the cooling zone is 40-45℃.

[0022] Preferably, in step S103, the ultraviolet irradiation degradation adopts the following ultraviolet irradiation device: the ultraviolet irradiation device includes a top plate, a plurality of ultraviolet lamps, a grid plate and a liftable support, the top plate is installed at the top end of the liftable support, the plurality of ultraviolet lamps are installed on the bottom surface of the top plate and are distributed in multiple rows, the grid plate is installed at both ends of the liftable support and is located below the ultraviolet lamps, and the multiple rows of ultraviolet lamps correspond to the multiple slits of the grid plate one by one.

[0023] Preferably, the grid plate comprises a plurality of light-blocking plates arranged at equal intervals, the gap width between two adjacent light-blocking plates is 25-45 mm, the width of each light-blocking plate is 60-120 mm, and the thickness of each light-blocking plate is 30-50 mm.

[0024] Preferably, when the grid plate is subjected to ultraviolet light irradiation degradation, the distance between the grid plate and the top plate is 250-400 mm, the distance between the grid plate and the film to be irradiated is 150-200 mm, the wavelength of the ultraviolet light lamp is 230-270 nm, and the light intensity is 140-180 mw / cm 2 .

[0025] As can be seen from the above description, the preparation method has the following advantages:

[0026] 1. The easy-to-tear PETG heat-shrinkable label film can be produced by adding ultraviolet light irradiation equipment and process steps on the basis of the existing ordinary PETG shrink label film forming equipment and process.

[0027] 2. After the shrink label film is formed, the film is irradiated by ultraviolet light through the designed grid-type gap, a plurality of light-degraded specific strip-shaped areas are formed in the longitudinal direction of the film, and a "mechanical property weak area" is formed, which facilitates tearing of the label from the weak area (after shrinkage). BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The preparation process flow chart of the easy-to-tear PETG heat-shrinkable label film is provided.

[0029] Figure 2 The structure schematic diagram of the ultraviolet light irradiation device is provided.

[0030] Figure 3 The structure schematic diagram of the grid plate of the ultraviolet light irradiation device is provided.

[0031] The drawings show that: 1. top plate, 2. ultraviolet light lamp, 3. grid plate, 31. light-blocking plate, 32. gap, 4. liftable support, 41. upper support, 42. lower support, 43. fixing bolt. DETAILED DESCRIPTION

[0032] The embodiments of the present application will be described in detail below, but do not limit the claims of the present application.

[0033] To solve the problem that the existing PETG label is not easy to tear, the present application provides an easy-to-tear PETG heat-shrinkable label film and a preparation method.

[0034] The tearable PETG heat shrinkable label film adopts a three-layer structure, including a core layer and two face layers, and the core layer is located between the two face layers, wherein:

[0035] I. The core layer component allocation ratio (by mass fraction) is as follows:

[0036] 1. PETG (polyethylene terephthalate-1, 4-cyclohexane dimethyl ester) 94.8-90.6 parts,

[0037] S2008, K2012 of SK company in Korea, EmbraceTM copolyester, EmbraceTMLV copolyester, GN001, 6763 of Eastman company in the United States, etc. can be selected;

[0038] 2. PLA (polylactic acid) 5.0-9.0 parts

[0039] Nature PLA polymer 2002D, 2003D, 4032D, etc. can be selected;

[0040] 3. UV initiator DEAP 0.2-0.4 parts;

[0041] The photoinitiator can be selected as DEAP (2, 2-diethoxy-1-phenylhexanone)

[0042] II. The face layer component allocation ratio (by mass fraction) is as follows:

[0043] 1. PETG (polyethylene terephthalate-1, 4-cyclohexane dimethyl ester) 98-98.5 parts, and the same brand product as the core layer can be selected;

[0044] 2. Opening smooth master batch 2.0-1.5 parts, TA10-08 MB13 of Sukano company in Switzerland can be selected.

[0045] Based on the above component allocation formula, the preparation method of the above tearable PETG heat shrinkable label film is given, and the steps are as follows:

[0046] I. Prepare the core layer raw material and the face layer raw material respectively:

[0047] According to the formula proportion, the core layer raw material: PETG, PLA and UV initiator DEAP are weighed, and DEAP and PLA are premixed as a component;

[0048] According to the formula proportion, the face layer raw material: PETG and opening smooth master batch are weighed.

[0049] II. Raw material melting plasticizing extrusion and filtering:

[0050] 1. The core layer raw material is added to the extruder for plasticizing and filtering;

[0051] The premixed PLA and ultraviolet light initiator are metered into the corresponding extruder of the core layer as one component together with PETG, and the extruded material is filtered through a filter;

[0052] The extruder used can be a parallel double-screw extruder with a screw diameter of 92 mm, a length-diameter ratio of 40:1, a rated extrusion capacity of 720 kg / h, and a plasticizing temperature of 245-270°C. The extruder can be matched with a two-gear volumetric metering pump with a capacity of 300 cm 3 / rpm.

[0053] 2. The surface layer raw material is added to the extruder for plasticizing and filtering;

[0054] The PETG and the opening smooth master batch are metered into the corresponding extruder of the surface layer, and the extruded material is filtered through a filter;

[0055] The extruder used can be a parallel double-screw extruder with a screw diameter of 85 mm, a length-diameter ratio of 40:1, a rated extrusion capacity of 580 kg / h, and a plasticizing temperature of 245-270°C. The extruder can be matched with a two-gear volumetric metering pump with a capacity of 126 cm 3 / rpm.

[0056] III. T-die casting:

[0057] The filtered core layer material and the surface layer material are fed to the T-die casting through the distributor according to the required layering mode.

[0058] The T-die can adopt an automatic adjusting hanger type single layer die with a die lip width of 960 mm, a die lip opening of 1.0-3.0, and a T-die temperature of 265-270°C.

[0059] IV. Cooling of the cast sheet:

[0060] The cast sheet is cooled by a quenching roller after casting.

[0061] The quenching roller with the following performance parameters can be used: the cast sheet cooling drum diameter of the quenching roller is 1500 mm, the cast sheet cooling drum water inlet temperature is 25-32°C (preferably 28°C), the roller surface width is 1160 mm, the surface finish is Ra0.025, the roller surface temperature control accuracy is ±1°C, and the quenching roller is matched with an electrostatic adsorption device with a high voltage of 7.5-9.0KV (preferably 8.1KV).

[0062] V. Transverse stretching:

[0063] The cast sheet is transversely stretched by a transverse stretching box after cooling, and the stretching ratio of the transverse stretching is controlled at 1:4-1:6, preferably 1:5.

[0064] The stretching working area includes a preheating zone, a stretching zone, a setting zone and a cooling zone, the temperature of the preheating zone is 90-110℃, the temperature of the stretching zone is 85-95℃, the temperature of the setting zone is 70-82℃, and the temperature of the cooling zone is 40-45℃.

[0065] Six, ultraviolet irradiation degradation:

[0066] The film material after stretching is subjected to photodegradation by ultraviolet irradiation.

[0067] The ultraviolet irradiation degradation can use an ultraviolet irradiation device as shown in Figure 2 , which includes a top plate 1, a plurality of ultraviolet lamps 2, a grid plate 3 and a liftable support 4, the top plate 1 is installed at the top end of the liftable support 4, the plurality of ultraviolet lamps 2 are installed on the bottom surface of the top plate 1 and are distributed in multiple rows, the grid plate 3 is installed at both ends of the liftable support 4 and is located below the ultraviolet lamps 2, and the multiple rows of ultraviolet lamps 2 correspond to the multiple slits of the grid plate 3 one by one.

[0068] Among them:

[0069] As shown in Figure 3 , the grid plate 3 includes a plurality of light-blocking plates 31 arranged at equal intervals, the width of the slit 32 between the adjacent two light-blocking plates is 25-45mm, the width of each light-blocking plate 31 is 60-120mm, and the thickness is 30-50mm, the light-blocking plate is a light-tight plate material, which can be selected from a wooden plate or a metal plate, the width of the grid plate 3 is the same as the maximum width of the film processed by the production line, and the length is 1300-4000mm. During ultraviolet irradiation degradation, the distance between the grid plate 3 and the top plate is 250-400mm, and the distance between the grid plate 3 and the film to be irradiated is 150-200mm, the wavelength of the ultraviolet lamp 2 is 230-270nm (preferably 253.7nm), and the light intensity is 140-180mw / cm 2 (preferably 165mw / cm 2 ). In actual application, the width and length of the grid plate, the width of the light-blocking plate, the width of the slit, the distance between the grid plate and the ultraviolet lamp, and the distance between the grid plate and the film can be set according to the size of the film processed by the production line and the parameters of the production line equipment, and are not limited to the above parameter ranges used for illustration.

[0070] As shown in Figure 2 , the liftable support 4 includes an upper support 41, a lower support 42 and a fixing bolt 43, the upper support 41 and the lower support 42 are made of hollow pipes with different diameters, the outer diameter of the upper support is smaller than the inner diameter of the lower support, the upper support is inserted into the lower support and locked by the fixing bolt, and the upper support is freely movable in the lower support when the fixing bolt is loosened. Thus, the distance between the grid plate and the film can be adjusted. In actual application, it is not limited to the Figure 1The illustrated liftable support structure can also use other liftable supports as long as the height of the grid plate from the film is adjustable.

[0071] Seven, winding:

[0072] After degradation, traction winding is carried out, and the easy-to-tear PETG heat shrinkable label film roll is obtained.

[0073] A double-station contact and gap winder can be used for winding, and the winding width can be 4200mm and the winding diameter can be 1000mm.

[0074] The easy-to-tear PETG heat shrinkable label film roll prepared by the above method can be stored as a semi-finished product, and subsequent sampling detection analysis can be carried out, and according to the use requirements, it can be processed into a finished label film with a certain size specification through the steps of slitting, inspection, packaging, etc.

[0075] The above preparation method can be processed and produced by a three-layer co-extrusion casting sheet horizontal uniaxial stretching production line.

[0076] The equipment selection and equipment process parameters involved in the above preparation method can be adjusted and selected according to the performance requirements of the actual label film and the available equipment, and are not limited to the equipment selection and equipment parameter settings mentioned in the above process.

[0077] In the above preparation method, the ultraviolet light initiator can also use TMO ((2,4,6-trimethylbenzoyl) bis(p-tolyl) phosphine oxide, CAS 270586-78-2), when using TMO, the amount is 1.5-2.5% of the mass of the core layer raw material.

[0078] Next, combined with the above preparation process and formula design scheme, select the raw materials, and specifically make three kinds of easy-to-tear PETG heat shrinkable label films, the formula component ratio in the three implementation schemes is shown in Table 1:

[0079] Table 1 Easy-to-tear PETG heat shrinkable label film formula (mass parts)

[0080]

[0081] The properties of the PETG heat shrinkable label films obtained in the three implementation schemes in Table 1 and the comparative sample were detected, and the test results are shown in Table 2:

[0082] Table 2 PETG heat shrinkable label film (just off-line) conventional data

[0083]

[0084] Note: The comparative sample is a common transparent PETG heat shrinkable label film. Just off-line means that the product is just prepared according to the production process, that is, the product is just prepared product.

[0085] The films in Table 2 were stored for a certain period of time, and then the performance test was carried out, and the change of mechanical properties during the storage period was obtained as shown in Table 3:

[0086] Table 3 Change of mechanical properties of film samples during storage period

[0087]

[0088]

[0089] As can be seen from Table 2, the longitudinal tensile strength and elongation at break of the easy-to-tear PETG heat shrinkable label film just prepared are both reduced compared with the common PETG heat shrinkable label film (comparative sample). As can be seen from Table 3, the test data of the longitudinal tensile strength and elongation at break of the easy-to-tear PETG heat shrinkable label film show a relatively obvious downward trend with the increase of storage time. Therefore, the longitudinal easy-to-tear performance of the easy-to-tear PETG heat shrinkable label film is better than that of the common PETG heat shrinkable label film, and the easy-to-tear performance gradually increases with the increase of time.

[0090] It can be understood that the above specific description of the present application is only used to illustrate the present application and is not limited to the technical solutions described in the embodiments of the present application. Those skilled in the art should understand that the present application can still be modified or replaced equivalently to achieve the same technical effect; as long as it meets the use needs, it is within the protection scope of the present application.

Claims

1. A PETG heat shrinkable label film with easy tearing, comprising a core layer and two layers of surface layers, the core layer being located between the two layers of surface layers, characterized in that, the core layer comprises the following components by mass fraction: PETG 94.8-90.6 parts, PLA 5.0-9.0 parts, UV initiator DEAP 0.2-0.4 parts; the surface layer comprises the following components by mass fraction: PETG 98-98.5 parts, opening smooth master batch 2.0-1.5 parts; the PETG heat shrinkable label film with easy tearing is prepared by using the following UV irradiation device for UV irradiation degradation during preparation: the UV irradiation device comprises a top plate, a plurality of UV lamps, a grid plate and a liftable support, the top plate is installed at the top end of the liftable support, the plurality of UV lamps are installed on the bottom surface of the top plate and are distributed in multiple rows, the grid plate is installed at both ends of the liftable support and is located below the UV lamps, the multiple rows of UV lamps correspond to the multiple slits of the grid plate one by one, and the grid plate comprises a plurality of light blocking plates arranged at equal intervals.

2. The PETG heat shrinkable label film with easy tearing according to claim 1, characterized in that, the core layer comprises the following components by mass fraction: PETG 92.7 parts, PLA 7.0 parts, and UV initiator DEAP 0.3 parts; the surface layer comprises the following components by mass fraction: PETG 98 parts, and opening smooth master batch 2.0 parts.

3. The preparation method of the PETG heat shrinkable label film with easy tearing according to claim 1 or 2, comprising the following steps: S101, respectively weighing the core layer raw materials and the surface layer raw materials according to the formula proportion; S102, plasticizing the core layer raw materials and the surface layer raw materials in the extruder and filtering through the filter; S103, feeding the filtered materials to the T-shaped die casting through the distributor according to the required layering mode, then cooling the cast sheet through the quenching roller, stretching in the transverse direction, and winding after UV irradiation degradation, to obtain the PETG heat shrinkable label film with easy tearing.

4. The preparation method of the PETG heat shrinkable label film with easy tearing according to claim 3, characterized in that, in step S102, the plasticizing temperature of the extruder is 245-270℃.

5. The preparation method of the PETG heat shrinkable label film with easy tearing according to claim 3, characterized in that, in step S103, the temperature of the T-shaped die is 265-270℃.

6. The preparation method of the PETG heat shrinkable label film with easy tearing according to claim 3, characterized in that, in step S103, the water inlet temperature of the quenching roller is 25-32℃.

7. The preparation method of the PETG heat shrinkable label film with easy tearing according to claim 3, characterized in that, in step S103, the stretching ratio of the transverse stretching is 1:4-1:6, and the stretching working area includes a preheating zone, a stretching zone, a setting zone and a cooling zone, the temperature of the preheating zone is 90-110℃, the temperature of the stretching zone is 85-95℃, the temperature of the setting zone is 70-82℃, and the temperature of the cooling zone is 40-45℃.

8. The method of claim 3, wherein the width of the gap between the adjacent two light-blocking plates of the grid plate is 25-45 mm, the width of each light-blocking plate is 60-120 mm, and the thickness of each light-blocking plate is 30-50 mm.

9. The method of claim 3, wherein the width of the gap between the adjacent two light-blocking plates of the grid plate is 25-45 mm, the width of each light-blocking plate is 60-120 mm, and the thickness of each light-blocking plate is 30-50 mm. ​ When the grid plate is irradiated by ultraviolet light, the distance between the grid plate and the top plate is 250-400 mm, the distance between the grid plate and the film to be irradiated is 150-200 mm, the wavelength of the ultraviolet light is 230-270 nm, and the light intensity is 140-180 mw / cm 2 .

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