PE heat-shrinkable packaging film

Abstract

The application relates to the technical field of heat-shrinking packaging material research and development, and discloses a PE heat-shrinking packaging film, which is characterized by the following steps: epoxy group alkenyl functionalized long-chain alkyl POSS monomers are modified on the surface of hydroxylated SiO2 nanoparticles through a hydroxyl-epoxy ring-opening reaction to prepare alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles; the alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles and EVA are effectively compounded through a free radical addition reaction and a molecular chain entanglement effect to prepare SiO2 / EVA composite master batches; the SiO2 / EVA composite master batches are used as modified components of polyethylene resin, and through a blending melting, blow film forming, bidirectional synchronous stretching and cooling setting process, the PE heat-shrinking packaging film is prepared; the film product can meet the technical requirements specified in the GB / T 13519-2016 'Polyethylene Heat-shrinking Film for Packaging' standard, and has practical application value.

Description

Technical Field

[0001] This invention relates to the field of heat shrink packaging material research and development technology, specifically a PE heat shrink packaging film. Background Technology

[0002] PE heat shrink packaging film is a functional packaging material made of polyethylene (PE) as the main raw material through directional stretching. It remains stable at room temperature and shrinks rapidly and tightly wraps the product after being heated by the memory effect. It has the advantages of high transparency, good flexibility and low cost, and is widely used in food, beverage, daily necessities, medicine, hardware and other fields.

[0003] Compared to PVC and PET heat shrink packaging films, PE heat shrink packaging films have the disadvantages of low shrinkage rate and low shrinkage force. They are difficult to wrap irregularly shaped and large-volume items snugly and are prone to loosening during transportation. This is because PE molecular chains have a linear structure, weak intermolecular forces, and extremely high flexibility. During the stretching process in production, although the molecular chains can be forcibly stretched apart, due to their excessive flexibility, some molecular chains will relax and rebound, making it impossible to stably store sufficient tensile stress. Moreover, PE is a semi-crystalline polymer, and the molecules in the crystalline regions are tightly and stably arranged, making it difficult for them to move and shrink rapidly when heated.

[0004] In addition, although PE heat shrink film has the advantage of low cost, it lacks strength and rigidity, and is prone to deformation, tearing and other damage during use.

[0005] Research has found that introducing EVA (ethylene-vinyl acetate copolymer, which is copolymerized from two monomers, ethylene E and vinyl acetate VA) into the PE matrix can significantly enhance the shrinkage rate and shrinkage force of PE heat shrink packaging film. This is because the polar VA units in EVA insert into the PE molecular chains, breaking the original regular arrangement of PE, reducing the number and size of crystalline regions, thereby reducing the overall crystallinity and enhancing the interaction force.

[0006] There are existing reports of using nano-silica (SiO2) as a filler to enhance the mechanical strength of polyethylene. Silica is widely available and inexpensive, and can significantly improve the mechanical strength of polyethylene even at low addition levels. Summary of the Invention

[0007] This invention develops and prepares an epoxy-alkenylated long-chain alkyl POSS monomer, which is first modified on the surface of SiO2 nanoparticles via a hydroxyl-epoxy ring-opening reaction, and then grafted onto the EVA molecular backbone via a free radical addition reaction to obtain a SiO2 / EVA composite masterbatch. The SiO2 / EVA composite masterbatch is then used to modify polyethylene resin to produce a PE heat-shrinkable packaging film. This film product meets the technical requirements specified in GB / T 13519-2016 "Polyethylene Heat-Shrinkable Film for Packaging" standard and has practical application value.

[0008] A PE heat-shrink packaging film, comprising the following raw materials in parts by weight:

[0009] 40-60 parts low-density polyethylene resin;

[0010] 20-40 parts linear low-density polyethylene resin;

[0011] 10-30 parts metallocene polyethylene resin;

[0012] 10-30 parts of SiO2 / EVA composite masterbatch;

[0013] 3-8 parts of compound additives;

[0014] The SiO2 / EVA composite masterbatch has the following formulation: 85-95wt% EVA and 5-15wt% alkenyl functionalized long-chain alkyl POSS-type SiO2 nanoparticles.

[0015] Alkenyl-functionalized long-chain alkyl POSS-type SiO2 nanoparticles were prepared by modifying the surface of hydroxylated SiO2 nanoparticles with epoxy-alkenylated long-chain alkyl POSS monomers via a hydroxyl-epoxy ring-opening reaction.

[0016] Preferably, the method for preparing the epoxy-alkenylated long-chain alkyl POSS monomer is as follows:

[0017] Secondary aminolated long-chain alkyl POSS monomers were prepared by nucleophilic substitution of the -NH2 functional group of 1 molar equivalent of octadecylamine with the chlorine functional group of 0.91-0.95 molar equivalent of 3-chloropropylheptaisobutyl POSS.

[0018] Tertiary amino-alkenylated long-chain alkyl POSS monomers were prepared by nucleophilic substitution of the -NH-functional group of 1 molar equivalent of secondary amino-alkenylated long-chain alkyl POSS monomer with the chlorine functional group of 0.91-0.95 molar equivalent of 6-chloro-1-hexene.

[0019] By utilizing a nucleophilic substitution reaction mechanism, epoxy-alkenylated long-chain alkyl POSS monomers were prepared by quaternization reaction of the tertiary amine functional group of a 1 molar equivalent tertiary amine-alkenylated long-chain alkyl POSS monomer with the chlorine functional group of 1.01-1.05 molar equivalent epichlorohydrin.

[0020] Preferably, the preparation method of the SiO2 / EVA composite masterbatch is as follows: free radicals are generated in EVA under the action of a peroxide initiator, and the alkenyl functional groups of alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles undergo an addition reaction with the free radicals in EVA. Furthermore, the long alkyl chains modified on the surface of the alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles are physically entangled with the EVA molecular chains to achieve effective composite of EVA and SiO2, thereby obtaining the SiO2 / EVA composite masterbatch.

[0021] Preferably, the peroxide initiator is one of dicumyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, and tert-butyl peroxide.

[0022] Preferably, the mass ratio of epoxy-alkenylated long-chain alkyl POSS monomers to hydroxylated SiO2 nanoparticles in the alkenylated functionalized long-chain alkyl POSS type SiO2 nanoparticles is 1:(3-6).

[0023] Preferably, the particle size of the hydroxylated SiO2 nanoparticles is 10-20 nm.

[0024] Preferably, the composite additive includes 1-3 parts by weight of antioxidant, 1-2 parts by weight of UV protectant and 1-3 parts by weight of slip agent.

[0025] Preferably, the antioxidant is one or a combination of two of antioxidant 168, antioxidant 1010, and antioxidant 1076.

[0026] Preferably, the UV protectant is one or a combination of two of the following: UV protectant UV-329, UV protectant UV-326, and UV protectant UV-531.

[0027] Preferably, the slip agent is polyethylene wax or zinc stearate.

[0028] Beneficial effects:

[0029] Based on molecular design mechanism, this invention uses octadecylamine as the base material and sequentially reacts it with 3-chloropropylheptaisobutyl POSS, 6-chloro-1-hexene and epichlorohydrin to undergo nucleophilic substitution reactions to obtain epoxy-alkenylated long-chain alkyl POSS monomers.

[0030] Epoxy-alkenylated long-chain alkyl POSS monomers were modified on the surface of hydroxylated SiO2 nanoparticles by hydroxyl-epoxy ring-opening reaction to obtain alkenyl-functionalized long-chain alkyl POSS type SiO2 nanoparticles.

[0031] Under the action of a free radical initiator, macromolecular free radicals are generated on the main chain of EVA molecules through hydrogen extraction reaction. By utilizing free radical addition reaction and molecular chain entanglement effect, alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles and EVA are effectively combined to obtain SiO2 / EVA composite masterbatch.

[0032] Using SiO2 / EVA composite masterbatch as a modifying component of polyethylene resin, PE heat shrink packaging film was prepared through blending and melting, blow molding, biaxial synchronous stretching and cooling and shaping processes.

[0033] The experimental results show that the PE heat shrink packaging film product prepared by the self-developed SiO2 / EVA composite masterbatch of this invention has achieved significant improvements in mechanical properties and shrinkage performance compared with conventional PE heat shrink film. Detailed Implementation

[0034] Example 1:

[0035] The synthesis process of epoxy-alkenylated long-chain alkyl POSS monomers is as follows:

[0036] Procedure 1: A nucleophilic substitution reaction was carried out between the -NH2 functional group of 1 molar equivalent of octadecylamine and the chlorine functional group of 0.93 molar equivalent of 3-chloropropylheptaisobutyl POSS (CAS No. 480438-84-4) to prepare a secondary amino-modified long-chain alkyl POSS monomer, the chemical structure of which is as follows:

[0037] ;

[0038] Procedure 2: A nucleophilic substitution reaction is carried out between the -NH- functional group of 1 molar equivalent of secondary amino-modified long-chain alkyl POSS monomer and the chlorine functional group of 0.95 molar equivalent of 6-chloro-1-hexene to prepare a tertiary amino-modified alkenylated long-chain alkyl POSS monomer, the chemical structure of which is as follows:

[0039] ;

[0040] Step 3: Utilizing a nucleophilic substitution mechanism, a quaternization reaction is carried out between the tertiary amine functional group of a 1 molar equivalent of tertiary amine-alkenylated long-chain alkyl POSS monomer and the chlorine functional group of 1.02 molar equivalent of epichlorohydrin to prepare an epoxy-alkenylated long-chain alkyl POSS monomer. Its chemical structural formula is as follows:

[0041] ;

[0042] The specific experimental steps for synthesizing epoxy-alkenylated long-chain alkyl POSS monomers are as follows:

[0043] 2.7 g of octadecylamine and 20 mL of anhydrous tetrahydrofuran were added to a three-necked flask and stirred at room temperature until completely dissolved. Then, 50 mL of anhydrous tetrahydrofuran solution containing 8.3 g of 3-chloropropylheptaisobutyl POSS and 1.5 mL of triethylamine were added to the three-necked flask in sequence. The mixture was heated to 60 °C and stirred for 8 h. After cooling to room temperature, the solvent was removed by rotary evaporation. The mixture was washed with deionized water and dried to obtain the secondary amino-modified long-chain alkyl POSS monomer.

[0044] 5.6 g of secondary amino-modified long-chain alkyl POSS monomer and 50 mL of anhydrous tetrahydrofuran were added to a three-necked flask and stirred at room temperature until completely dissolved. Then, 10 mL of anhydrous tetrahydrofuran solution containing 1.1 g of 6-chloro-1-hexene and 1.2 mL of triethylamine were added to the three-necked flask in sequence. The mixture was heated to 70 °C and stirred for 6 h. After cooling to room temperature, the solvent was removed by rotary evaporation. The mixture was washed with deionized water and dried to obtain tertiary amino-modified long-chain alkyl POSS monomer.

[0045] Under nitrogen protection, 4.0 g of tertiary amino-alkenylated long-chain alkyl POSS monomer and 40 mL of anhydrous tetrahydrofuran were added to a three-necked flask and stirred at room temperature until completely dissolved. Then, 5 mL of anhydrous tetrahydrofuran solution containing 0.3 g of epichlorohydrin was added to the three-necked flask and stirred at room temperature for 16 h. The solvent was removed by rotary evaporation and dried to obtain epoxy-alkenylated long-chain alkyl POSS monomer.

[0046] The 1H NMR characterization of epoxy-alkenylated long-chain alkyl POSS monomers is as follows: 1 H NMR (CDCl3, 400MHz) δ: 0.58-0.60 (d, 14H), 0.75-0.78 (t, 2H), 0.83-0.87 (t, 3H), 0.95-0.96 (d, 42H), 1.23-1.37 (m, 30H), 1.49-1.57 (m, 6 H), 1.67-1.79(m, 9H), 2.10-2.14(m, 2H), 3.45-3.57(m, 8H), 3.78-3.79(d, 2H), 3.97-4.04(m, 1H), 4.98-5.12(dd, 2H), 5.71-5.81(m, 1H).

[0047] Example 2:

[0048] Preparation of alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles: The epoxy group of the epoxy group of the epoxy group of the epoxy group of the long-chain alkyl POSS monomer reacts with the hydroxyl functional group on the surface of the hydroxylated SiO2 nanoparticles to modify the surface of the SiO2 nanoparticles with the epoxy group of the epoxy group of the long-chain alkyl POSS monomer, thereby obtaining the alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles.

[0049] The specific experimental steps for preparing alkenyl-functionalized long-chain alkyl POSS-type SiO2 nanoparticles are as follows: Under nitrogen protection, 5g of hydroxylated nano-silica powder (particle size 10-20nm) and 100mL of anhydrous tetrahydrofuran were added to a three-necked flask and stirred and dispersed at room temperature for 30min. Then, 10mL of anhydrous tetrahydrofuran solution containing 1g of epoxy-alkenylated long-chain alkyl POSS monomer and 1.5mL of triethylamine were added dropwise to the three-necked flask. The mixture was heated to 70℃ and stirred for 6h. After cooling to room temperature, the solvent was removed by rotary evaporation. The mixture was repeatedly washed with ethanol, centrifuged, and dried to obtain alkenyl-functionalized long-chain alkyl POSS-type SiO2 nanoparticles.

[0050] Example 3:

[0051] SiO2 / EVA composite masterbatch I was prepared with the following formulation: 95 wt% EVA and 5 wt% alkenyl functionalized long-chain alkyl POSS-type SiO2 nanoparticles. The preparation method was as follows: on the one hand, free radicals were generated in EVA under the action of a peroxide initiator, and the alkenyl functional groups of the alkenyl functionalized long-chain alkyl POSS-type SiO2 nanoparticles were used to carry out an addition reaction with the free radicals in EVA. On the other hand, the long alkyl chains modified on the surface of the alkenyl functionalized long-chain alkyl POSS-type SiO2 nanoparticles were used to generate physical entanglement with the EVA molecular chains, thereby achieving effective composite of EVA and SiO2 and obtaining SiO2 / EVA composite masterbatch I.

[0052] The peroxide initiator can be selected from one of dicumyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, and tert-butyl peroxide; in this embodiment, dicumyl peroxide is selected.

[0053] The specific experimental steps for preparing SiO2 / EVA composite masterbatch I are as follows: First, EVA (model P1207) is dried in a vacuum drying oven at 60℃ for 12h. Then, 9.5g of dried EVA, 0.5g of alkenyl functionalized long-chain alkyl POSS-type SiO2 nanoparticles and 0.1g of dicumyl peroxide initiator are added to a high-speed mixer and mixed evenly. The mixture is then melted, extruded and granulated by a twin-screw extruder to obtain SiO2 / EVA composite masterbatch I.

[0054] The process parameters of the twin-screw extruder are set as follows: preheating temperature 150℃, temperatures of zones 1-6 are 150℃, 160℃, 170℃, 180℃, 180℃, and 185℃ respectively, rotation speed is 60r / min, and melt processing time is 20min.

[0055] Example 4:

[0056] The SiO2 / EVA composite masterbatch II was prepared. The only difference between it and SiO2 / EVA composite masterbatch I is that the formulation is: 90wt% EVA and 10wt% alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles.

[0057] Example 5:

[0058] The SiO2 / EVA composite masterbatch III was prepared. The only difference between it and SiO2 / EVA composite masterbatch I is that the formulation is: 85wt% EVA and 15wt% alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles.

[0059] Example 6:

[0060] A PE heat-shrink packaging film, comprising the following raw materials in parts by weight:

[0061] 50 parts of low-density polyethylene resin (model LD 150DW);

[0062] 30 parts linear low-density polyethylene resin (model 7042);

[0063] 20 parts of metallocene polyethylene resin (model SP1520).

[0064] 15 parts SiO2 / EVA composite masterbatch;

[0065] 1 part antioxidant 168;

[0066] 0.5 parts antioxidant 1010;

[0067] 1 part UV-329 anti-ultraviolet agent;

[0068] 2 parts polyethylene wax slip agent;

[0069] Among them, the SiO2 / EVA composite masterbatch is one of SiO2 / EVA composite masterbatch I, SiO2 / EVA composite masterbatch II, and SiO2 / EVA composite masterbatch III.

[0070] Example 7:

[0071] A method for preparing a PE heat-shrink packaging film includes the following steps:

[0072] Step 1: Prepare the ingredients according to the PE heat shrink packaging film formula. Add each ingredient to a high-speed mixer and mix evenly to obtain a premix.

[0073] Step 2: Add the premixed material into the twin-screw extruder through the feeding port for melt blending, extrusion granulation, blow molding into film using a single-screw extrusion blown film machine, pull it to the stretching oven for bidirectional synchronous stretching, cool it to room temperature through the air ring for shaping, slit and roll it up to obtain PE heat shrink packaging film;

[0074] The process parameters for the twin-screw extruder are set as follows: temperatures in zones 1-6 are 150℃, 160℃, 160℃, 170℃, 180℃, and 190℃, respectively, and the rotation speed is 300 r / min. The process parameters for the single-screw extrusion blown film extruder are set as follows: temperatures in zones 1-3 are 150℃, 170℃, and 180℃, respectively, and the rotation speed is 60 r / min. The traction speed is 7 m / min, the die diameter of the blown film extruder is 50 mm, and the blow-up ratio is 2.1. The process parameters for the biaxial synchronous stretching are set as follows: stretching temperature is 100℃, preheating time is 5 s, and the longitudinal to transverse stretching ratio is 3:1.

[0075] When the SiO2 / EVA composite masterbatch is SiO2 / EVA composite masterbatch I, the resulting film product is denoted as PE heat shrink packaging film I.

[0076] When the SiO2 / EVA composite masterbatch is SiO2 / EVA composite masterbatch II, the resulting film product is denoted as PE heat shrink packaging film II.

[0077] When the SiO2 / EVA composite masterbatch is SiO2 / EVA composite masterbatch III, the resulting film product is denoted as PE heat shrink packaging film III.

[0078] Comparative example:

[0079] Preparation of conventional PE heat shrink film: Compared with PE heat shrink packaging film I, the only difference is that low density polyethylene resin (model LD 150DW) is used to replace SiO2 / EVA composite masterbatch I (i.e., SiO2 / EVA composite masterbatch I is not used in the formulation).

[0080] Performance testing:

[0081] I. Mechanical properties and shrinkage properties of PE heat shrink packaging film samples were tested. The test results were based on the technical standard GB / T 13519-2016 "Polyethylene Heat Shrink Film for Packaging". The test results are shown in Table 1 and Table 2 below.

[0082] Table 1 Performance Test Results of PE Heat Shrink Packaging Film

[0083]

[0084] Table 2 Performance Test Results of PE Heat Shrink Packaging Film

[0085]

[0086] II. Heat sealing performance test of PE heat shrink packaging film samples: The samples were subjected to a heat sealing test with a sealing blade area of ​​15cm × 1cm, a heat sealing temperature of 120℃, a heat sealing pressure of 0.2MPa, and a heat sealing time of 2.0s. The heat sealing strength of the heat-sealed samples was tested according to QB / T 2358-1998 "Test Method for Heat Sealing Strength of Plastic Film Packaging Bags" with a test speed of 100mm / min and a clamp spacing of 50mm.

[0087] The test results are shown in Table 3 below;

[0088] Table 3 Performance Test Results of PE Heat Shrink Packaging Film

[0089]

[0090] A comprehensive analysis of the above experimental results leads to the following conclusions:

[0091] Conclusion 1: The PE heat shrink packaging film product prepared by the self-developed SiO2 / EVA composite masterbatch of this invention has achieved significant improvements in mechanical properties and shrinkage performance compared with conventional PE heat shrink film, meeting the technical requirements specified in GB / T 13519-2016 "Polyethylene Heat Shrink Film for Packaging" standard.

[0092] Conclusion 2: The heat-sealing strength of the PE heat-shrink packaging film prepared by this invention is significantly greater than the technical requirement of JB / T 9086-2007 "Plastic Bag Heat Sealing Machine" for sealing strength ≥15N (material thickness R, 0.08mm≤R<0.18mm), indicating excellent comprehensive performance and practical application value.

Claims

1. A PE heat-shrink packaging film, characterized in that, The ingredients include the following parts by weight: 40-60 parts low-density polyethylene resin; 20-40 parts linear low-density polyethylene resin; 10-30 parts metallocene polyethylene resin; 10-30 parts of SiO2 / EVA composite masterbatch; 3-8 parts of compound additives; The SiO2 / EVA composite masterbatch has the following formulation: 85-95wt% EVA and 5-15wt% alkenyl functionalized long-chain alkyl POSS-type SiO2 nanoparticles. Alkenyl-functionalized long-chain alkyl POSS type SiO2 nanoparticles were prepared by modifying the surface of hydroxylated SiO2 nanoparticles with epoxy-alkenylated long-chain alkyl POSS monomers via a hydroxyl-epoxy ring-opening reaction. The chemical structural formula of the epoxy-alkenylated long-chain alkyl POSS monomer is as follows: 。 2. The PE heat-shrink packaging film according to claim 1, characterized in that, The preparation method of the epoxy-alkenylated long-chain alkyl POSS monomer is as follows: Secondary aminolated long-chain alkyl POSS monomers were prepared by nucleophilic substitution of the -NH2 functional group of 1 molar equivalent of octadecylamine with the chlorine functional group of 0.91-0.95 molar equivalent of 3-chloropropylheptaisobutyl POSS. Tertiary amino-alkenylated long-chain alkyl POSS monomers were prepared by nucleophilic substitution of the -NH-functional group of 1 molar equivalent of secondary amino-alkenylated long-chain alkyl POSS monomer with the chlorine functional group of 0.91-0.95 molar equivalent of 6-chloro-1-hexene. By utilizing a nucleophilic substitution reaction mechanism, epoxy-alkenylated long-chain alkyl POSS monomers were prepared by quaternization reaction of the tertiary amine functional group of a 1 molar equivalent tertiary amine-alkenylated long-chain alkyl POSS monomer with the chlorine functional group of 1.01-1.05 molar equivalent epichlorohydrin.

3. The PE heat-shrink packaging film according to claim 1, characterized in that, The preparation method of the SiO2 / EVA composite masterbatch is as follows: free radicals are generated in EVA under the action of a peroxide initiator. The alkenyl functional groups of alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles undergo an addition reaction with the free radicals in EVA. Furthermore, the long alkyl chains modified on the surface of the alkenyl functionalized long-chain alkyl POSS type SiO2 nanoparticles are physically entangled with the EVA molecular chains to achieve effective composite of EVA and SiO2, thus obtaining the SiO2 / EVA composite masterbatch.

4. The PE heat-shrink packaging film according to claim 3, characterized in that, The peroxide initiator is one of dicumyl peroxide, tert-butyl hydroperoxide, benzoyl peroxide, and tert-butyl peroxide.

5. A PE heat-shrink packaging film according to claim 1, characterized in that, The mass ratio of epoxy-alkenylated long-chain alkyl POSS monomers to hydroxylated SiO2 nanoparticles in the alkenyl-functionalized long-chain alkyl POSS type SiO2 nanoparticles is 1:(3-6).

6. The PE heat-shrink packaging film according to claim 5, characterized in that, The hydroxylated SiO2 nanoparticles have a particle size of 10-20 nm.

7. The PE heat-shrink packaging film according to claim 1, characterized in that, The composite additive includes 1-3 parts by weight of antioxidant, 1-2 parts by weight of UV protectant and 1-3 parts by weight of slip agent.

8. A PE heat-shrink packaging film according to claim 7, characterized in that, The antioxidant is one or a combination of two of antioxidant 168, antioxidant 1010, and antioxidant 1076.

9. A PE heat-shrink packaging film according to claim 7, characterized in that, The UV protectant is one or a combination of two of the following: UV protectant UV-329, UV protectant UV-326, and UV protectant UV-531.

10. A PE heat-shrink packaging film according to claim 7, characterized in that, The slip agent is polyethylene wax or zinc stearate.

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