CN115923289B - High-transparency high-strength polyethylene heat-shrinkable film and preparation method thereof - Google Patents
High-transparency high-strength polyethylene heat-shrinkable film and preparation method thereof Download PDFInfo
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Abstract
The application relates to the field of packaging materials, and particularly discloses a high-transparency high-strength polyethylene heat-shrinkable film and a preparation method thereof. The high-transparency high-strength polyethylene heat-shrinkable film comprises a layer A, a layer B, a layer C, a layer D and a layer E which are sequentially attached from inside to outside; the layer A and the layer E comprise the following raw materials in parts by weight: 30-50 parts of low-density polyethylene, 15-25 parts of metallocene polyethylene and 30-50 parts of linear low-density polyethylene; the layer B, the layer C and the layer D all comprise the following raw materials in parts by weight: 3-7 parts of low-density polyethylene, 40-80 parts of high-density polyethylene and 30-40 parts of metallocene polyethylene. The high-transparency high-strength polyethylene heat-shrinkable film has the advantages of high transparency, good mechanical strength, stable stacking and difficult atomization in packaging.
Description
Technical Field
The application relates to the technical field of packaging materials, in particular to a high-transparency high-strength polyethylene heat-shrinkable film and a preparation method thereof.
Background
The heat-shrinkable film is commonly called a heat-shrinkable film, and is a film which can shrink greatly after being heated, thus being capable of tightly wrapping objects and keeping the shape of the objects for a long time. The heat-shrinkable film is formed by adopting a high polymer molecular chain stretching orientation principle design and a rapid cooling shaping method. The polyethylene heat-shrinkable film has high impact strength and high heat sealing strength after processing, can meet the functions of dampproofing, dustproof, touch-proof, anti-theft, transparent display and the like of commodities, and can increase the attractive appearance of products. The heat-shrinkable film is mainly used for packaging relatively heavy articles such as bottled beverages, such as wine, pop cans, mineral water collection packages and the like, and can partially replace paper box packages.
In the prior art, the Chinese patent application document of application number CN2018108230461 discloses a heat-shrinkable film, which comprises an inner layer, a middle layer and an outer layer, wherein the inner layer and the outer layer are prepared from the following raw materials in percentage by weight: 20-40% of high-density polyethylene, 20-40% of high-pressure polyethylene and 30-60% of medium-density metallocene polyethylene; the middle layer is prepared from the following raw materials in percentage by weight: 0-30% of high-density polyethylene, 0-30% of high-pressure polyethylene and 50-100% of medium-density metallocene polyethylene; the density of the high-density polyethylene is 0.938-0.942g/cm 3 21.6kg melt mass flow rate of 5-10g/10min; the density of the high-pressure polyethylene is 0.918-0.926g/cm 3 2.16kg melt mass flow rate of 0.5-2.0g/10min; the medium density metallocene polyethylene is copolymer of ethylene and 1-hexene and has density of 0.932-0.938g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The melt mass flow rate is 0.1-0.8g/10min.
In view of the above related art, the inventors found that although the above heat-shrinkable film has good mechanical properties and reduced heat-shrinking temperature of the film, the high-density polyethylene and the medium-density polyethylene are used in large amounts, so that the blend has a high density, and the produced heat-shrinkable film has a high surface bloom, a high haze and a low transparency, and thus the strength and the transparency of the heat-shrinkable film cannot be simultaneously achieved.
Disclosure of Invention
In order to simultaneously improve the strength and transparency of the heat-shrinkable film, the application provides a high-transparency high-strength polyethylene heat-shrinkable film and a preparation method thereof.
In a first aspect, the application provides a high-transparency high-strength polyethylene heat-shrinkable film, which adopts the following technical scheme: the high-transparency high-strength polyethylene heat-shrinkable film comprises a layer A, a layer B, a layer C, a layer D and a layer E which are sequentially attached from inside to outside;
the layer A and the layer E comprise the following raw materials in parts by weight: 30-50 parts of low-density polyethylene, 15-25 parts of metallocene polyethylene and 30-50 parts of linear low-density polyethylene;
the layer B, the layer C and the layer D all comprise the following raw materials in parts by weight: 3-7 parts of low-density polyethylene, 40-80 parts of high-density polyethylene and 30-40 parts of metallocene polyethylene.
By adopting the technical scheme, the metallocene polyethylene and the linear low-density polyethylene are used in the layer A and the layer E, the metallocene polyethylene has outstanding tensile property, impact resistance and puncture resistance, better transparency and lower haze value, the linear low-density polyethylene has high strength, good toughness and rigidity, good environmental stress cracking resistance, good impact strength and tear strength, the transparency is better than that of the high-density polyethylene, the high-density polyethylene is used in the layer B, the layer C and the layer D, the excellent environmental stress cracking resistance is achieved, and the metallocene polyethylene and the low-density polyethylene are used for improving the transparency of the layer B, the layer C and the layer D, so that the thermal shrinkage film with high strength and high transparency is prepared.
Optionally, the metallocene polyethylene in the A layer and the E layer has a density of 0.916-0.92g/cm 3 The melt index is 0.2-0.22g/10min;
the density of the metallocene polyethylene in the B layer, the C layer and the D layer is 0.918-0.93g/cm 3 The melt index is 1-1.2g/10min; the density of the low density polyethylene in the A layer, the B layer, the C layer, the D layer and the E layer is 0.910-0.9259g/cm 3 The melt index is 0.25-0.28g/10min; the linear low density polyethylene has a density of 0.915 to 0.918g/cm 3 The melt index is 2-2.1g/10min; the density of the high-density polyethylene is 0.945 to 0.95g/cm 3 The melt index is 0.18-0.19g/10min.
By adopting the technical scheme, the metallocene polyethylene, the linear low-density polyethylene, the high-density polyethylene and the low-density polyethylene with proper density and melt index are used, so that the prepared heat-shrinkable film has higher mechanical strength and better transparency.
Optionally, 10-15 parts by weight of antifogging agent is added into the layer A.
By adopting the technical scheme, the antifogging agent is added in the innermost layer A, so that the antifogging effect of the inner layer of the heat-shrinkable film can be improved, and the definition of the film can be improved.
Optionally, the preparation method of the antifogging agent comprises the following steps:
adding chitosan into acetic acid solution with concentration of 1-2wt% to obtain chitosan solution with concentration of 0.5-1wt%, adding cellulose nanofibrils, performing ultrasonic treatment for 30-40min, freeze drying, and pulverizing to obtain hydrophilic matrix;
mixing the hydrophilic matrix with polycarbonate, extruding and granulating to obtain hydrophilic particles;
adding polyvinyl alcohol into deionized water, heating to 80-90 ℃, stirring for 2-3h, adding polytetrafluoroethylene emulsion, graphene and lotus root silk fiber, performing ultrasonic treatment for 20-30min, and defoaming at room temperature for 10-12h to prepare a casting solution;
and uniformly spraying the casting film liquid on the hydrophilic particles, and then freeze-drying.
By adopting the technical scheme, chitosan is dissolved in acetic acid solution, uniform and transparent chitosan can be formed, a large number of hydroxyl groups are arranged on the surface of cellulose nanofibrils, so that hydrogen bonds are formed among fiber bundles and are tightly connected with each other, after ultrasonic treatment, the hydroxyl groups on the cellulose nanofibrils can form effective hydrogen bonds with amine groups on the chitosan, a crosslinked reticular structure is formed in the chitosan solution, the chitosan and the cellulose nanofibrils are mixed and freeze-dried, and the cellulose nanofibrils are embedded into a chitosan matrix to generate a three-dimensional porous structure due to sublimation of ice crystals, and the chitosan can promote good dispersion of the cellulose nanofibrils, so that the uniformity of the internal structure of a hydrophilic matrix is improved, the hydrophilic matrix has higher mechanical flexibility and compression rebound resilience, and the tensile strength and the shrinkage rate of a heat shrinkage film are improved conveniently; then mixing and extruding a hydrophilic matrix and polycarbonate, wherein the polycarbonate is a hydrophilic substance which can easily absorb moisture, has a three-dimensional porous structure, can be uniformly distributed in the polycarbonate or on the surface, and further improves the hydrophilicity of the polycarbonate, so that hydrophilic particles with stronger hydrophilicity are obtained; then preparing a casting solution by using graphene, lotus root fibers, polytetrafluoroethylene emulsion and the like, after spraying the casting solution on hydrophilic particles, solidifying the casting solution to form a surface film on the hydrophilic particles, wherein the graphene can increase the roughness and the porosity of the surface film, so that the hydrophobicity of the surface film is improved, the wettability resistance of the surface film is improved, and finger-shaped holes are formed in the film formed by the polytetrafluoroethylene by the graphene, so that water vapor can permeate into the hydrophilic particles along the surface film; the added lotus root silk fiber not only can improve the mechanical strength of a surface film, but also can promote the formation and development of a directional pore canal structure, so that the surface film has a porous canal structure, and the lotus root silk fiber is used as a heterogeneous solid phase component, plays a role in nuclear point when casting film liquid is crystallized, and reduces the energy barrier of ice crystal nucleation, so that more directional arranged ice crystals with larger size are formed, and the directional pore canal formed after the ice crystals are sublimated and removed can provide a large number of quick channels when the subsequent water vapor enters hydrophilic particles, therefore, when the heat shrink film is packaged into an easy product, the water vapor can be absorbed when the water vapor is generated inside due to the temperature rise, the internal atomization of the heat shrink film is prevented, and the internal product cannot be seen clearly.
Optionally, the antifogging agent comprises the following raw materials in parts by weight: 2-3 parts of polycarbonate, 2-3 parts of chitosan, 1-2 parts of cellulose nanofibrils, 1-1.5 parts of polytetrafluoroethylene emulsion, 0.3-0.6 part of graphene, 0.1-0.3 part of lotus root silk fiber and 0.5-1 part of lotus root silk fiber
Polyvinyl alcohol and 8-10 parts of deionized water.
Through adopting above-mentioned technical scheme, each raw materials of above quantity can make outside hydrophobic, inside hydrophilic antifogging agent, and steam can get into hydrophilic granule along the pore that lotus root silk fibre, the graphite alkene formed in the surface film, is absorbed by hydrophilic granule to prevent that thermal contraction membrane inlayer from producing the water smoke.
Optionally, the lotus root silk fiber is pretreated by the following steps:
dispersing hydrophobic silica into an aqueous solution of polyethylene glycol with the concentration of 3-5wt%, then uniformly spraying the aqueous solution onto lotus root silk fibers, and drying, wherein the mass ratio of the aqueous solution of the hydrophobic silica and the polyethylene glycol to the lotus root silk fibers is 0.3-0.5:0.6-1:1-3.
Through adopting above-mentioned technical scheme, lotus root silk fibre has hydrophilicity, when blending with polytetrafluoroethylene emulsion, difficult dispersion is even, consequently utilizes the cohesiveness of polyethylene glycol, bonds hydrophobic silica on lotus root silk fibre, and hydrophobic silica can increase lotus root silk fibre surface roughness, improves its dispersity with polytetrafluoroethylene, and hydrophobic silica is the nonpolar material moreover, can be even with polytetrafluoroethylene dispersion, improves lotus root silk fibre and polytetrafluoroethylene's adhesion stress.
Optionally, a surface friction modifier is bonded on the side of the E layer far from the D layer through an adhesive, wherein the surface friction modifier comprises 1-2 parts by weight of polyurethane elastomer, 0.6-1.6 parts by weight of carbon nano tube and 0.3-0.7 part by weight of carbon fiber.
By adopting the technical scheme, the surface of the heat-shrinkable film is smooth, the heat-shrinkable film is unstable during stacking and unsafe to transport, so that the friction modifier is added to the outer surface of the E layer, the friction modifier is prepared by blending a thermosetting polyurethane elastomer, a carbon nano tube and a carbon fiber, the carbon fiber and the carbon nano tube can form a three-dimensional composite structure in the friction modifier, the tensile strength of the friction modifier is improved, the friction modifier is good in wear resistance, and the friction modifier is elastic, can form a friction increasing layer on the E layer, the surface friction coefficient of the E layer is improved, and the stacking stability is improved.
Optionally, the preparation method of the surface friction modifier comprises the following steps:
treating the carbon nanotubes with sodium hydroxide solution to obtain hydroxylated carbon nanotubes; and (3) treating the carbon fiber by a silane coupling agent, and then mixing the carbon fiber with the hydroxylated carbon nano tube and the polyurethane elastomer, extruding and granulating.
Through adopting above-mentioned technical scheme, after the carbon nanotube is hydroxylated, can form dipole effect and hydrogen bond effect with the polar group on the polyurethane elastomer, form compatible system, the friction modifier on E layer surface produces the microcrack because of stack friction, when two crack surfaces contact together again, the molecule between the crack surfaces forms the hydrogen bond again to produce self-repairing effect, improve stack stability.
Optionally, the surface friction modifier has an average particle size of 5-10 μm and the surface friction modifier is used in an amount of 30-50g/m 3 。
By adopting the technical scheme, the friction surface modifier with smaller particle size can be uniformly distributed on the surface of the E layer, so that the friction force between the E layers during stacking is improved, and the stacking stability is improved.
In a second aspect, the application provides a preparation method of a high-transparency high-strength polyethylene heat-shrinkable film, which adopts the following technical scheme:
a preparation method of a high-transparency high-strength polyethylene heat-shrinkable film comprises the steps of weighing raw materials of a layer A, a layer B, a layer C, a layer D and a layer E, and uniformly mixing the raw materials;
according to the thickness ratio of the layer A, the layer B, the layer C, the layer D and the layer E being 1:1:1:1, the raw materials of each layer are melted, blown, cooled and shaped, pulled and stretched, cut and rolled to prepare the high-transparency high-strength polyethylene heat-shrinkable film.
By adopting the technical scheme, after the raw materials of all layers are blended, the thermal shrinkage film is prepared by melting and inflation, and the preparation process is simple.
In summary, the application has the following beneficial effects:
1. the application adopts low-density polyethylene, metallocene polyethylene and linear low-density polyethylene as raw materials of the layer A and the layer E, and adopts metallocene polyethylene, high-density polyethylene and other raw materials in the layer B, the layer C and the layer D in the middle to prepare the heat-shrinkable film with high mechanical strength and good transparency.
2. In the application, the antifogging agent is preferably added in the layer A, and the antifogging agent is prepared by coating hydrophilic particles by casting film liquid, the casting film liquid can form a surface film with a porous structure due to the inclusion of lotus root fibers and graphene, the hydrophilic particles are prepared into a porous hydrophilic matrix by freeze drying chitosan and cellulose nanofibrils, and then the porous hydrophilic matrix is blended with polycarbonate for extrusion, so that water vapor generated in the heat-shrinkable film can permeate into the hydrophilic particles along pore channels on the surface film and be absorbed by the hydrophilic particles, thereby preventing the product wrapped by the heat-shrinkable film from generating water vapor, atomizing the inside of the heat-shrinkable film and affecting the definition, and the transparency of the heat-shrinkable film is slightly affected by raw materials used for the antifogging agent.
3. In the application, the surface friction modifier is preferably adhered to the outer surface of the E layer through the adhesive, the surface friction modifier is prepared by blending and extruding a thermosetting polyurethane elastomer, a carbon nano tube and a carbon fiber, the carbon nano tube and the carbon fiber can further improve the toughness and the elasticity of the surface friction modifier, so that the surface friction coefficient is increased, the stacking stability is improved, and the adhesion of the surface friction modifier has less influence on the transparency of thermal shrinkage.
Detailed Description
Preparation examples 1 to 9 of antifogging agent
Preparation example 1: adding 3kg of chitosan with deacetylation degree higher than 90% into acetic acid solution with concentration of 2wt% to prepare chitosan solution with concentration of 1wt%, adding 2kg of cellulose nanofibrils, performing ultrasonic treatment for 40min, freezing at-20 ℃ for 28h, then performing freeze drying at-60 ℃ under vacuum pressure of 1Pa for 72h, and crushing to prepare a hydrophilic matrix;
mixing the hydrophilic matrix with 3kg of polycarbonate, extruding and granulating to obtain hydrophilic particles;
adding 1kg of polyvinyl alcohol into 10kg of deionized water, heating to 90 ℃, stirring for 3 hours, adding 1.5kg of polytetrafluoroethylene emulsion, 0.6kg of graphene and 0.3kg of lotus root silk fiber, carrying out ultrasonic treatment for 30 minutes, and defoaming for 12 hours at room temperature to prepare a casting solution;
and uniformly spraying the casting solution on the hydrophilic particles, and then freeze-drying for 5 days under the conditions that the temperature is-49 ℃ and the vacuum degree is 14 Pa.
Preparation example 2: adding 2kg of chitosan with deacetylation degree higher than 90% into acetic acid solution with concentration of 1wt% to prepare chitosan solution with concentration of 0.5wt%, adding 1kg of cellulose nanofibrils, performing ultrasonic treatment for 30min, freezing at-20 ℃ for 28h, then freeze-drying at-60 ℃ under vacuum pressure of 1Pa for 72h, and crushing to prepare a hydrophilic matrix;
mixing the hydrophilic matrix with 2kg of polycarbonate, extruding and granulating to obtain hydrophilic particles;
adding 0.5kg of polyvinyl alcohol into 8kg of deionized water, heating to 80 ℃, stirring for 2 hours, adding 1kg of polytetrafluoroethylene emulsion, 0.3kg of graphene and 0.1kg of lotus root silk fiber, performing ultrasonic treatment for 20 minutes, and defoaming for 10 hours at room temperature to prepare a casting solution;
and uniformly spraying the casting solution on the hydrophilic particles, and then freeze-drying for 5 days under the conditions that the temperature is-49 ℃ and the vacuum degree is 14 Pa.
Preparation example 3: adding 1kg of polyvinyl alcohol into 10kg of deionized water, heating to 90 ℃, stirring for 3 hours, adding 1.5kg of polytetrafluoroethylene emulsion and 0.3kg of lotus root silk fiber, carrying out ultrasonic treatment for 30 minutes, and defoaming for 12 hours at room temperature to prepare a casting solution;
the casting solution was uniformly sprayed on polycarbonate, and then freeze-dried at a temperature of-49℃and a vacuum of 14Pa for 5 days.
Preparation example 4: the difference from preparation example 1 is that the casting solution was sprayed uniformly onto the hydrophilic substrate without adding polycarbonate.
Preparation example 5: the difference from preparation example 1 is that no lotus root fibers were added to the casting solution.
Preparation example 6: the difference from the preparation example 1 is that no graphene was added to the casting solution.
Example 7: the difference from preparation example 1 is that polytetrafluoroethylene emulsion was used as the casting solution, and lotus root fibers and graphene were not added.
Preparation example 8 differs from preparation example 1 in that hydrophobic silica is dispersed into an aqueous solution of polyethylene glycol having a concentration of 5wt%, and then uniformly sprayed onto lotus root silk fibers, and dried, wherein the mass ratio of the aqueous solution of hydrophobic silica, polyethylene glycol and lotus root silk fibers is 0.3:0.6:1.
Preparation example 9 differs from preparation example 1 in that hydrophobic silica is dispersed into an aqueous solution of polyethylene glycol having a concentration of 5wt%, and then uniformly sprayed onto lotus root silk fibers, and dried, wherein the mass ratio of the aqueous solution of hydrophobic silica, polyethylene glycol and lotus root silk fibers is 0.5:1:3.
Preparation examples 10 to 13 of surface Friction modifiers
Preparation example 10: immersing 1.6kg of carbon nanotubes in 15wt% sodium hydroxide solution for 20min, filtering, washing and drying to obtain hydroxylated carbon nanotubes; 0.7kg of carbon fiber is subjected to soaking treatment by ethanol solution of silane coupling agent KH550 with concentration of 2.5wt% for 30min, filtering, washing, drying, mixing with hydroxylated carbon nano tube and 2kg of polyurethane elastomer, melting at 190 ℃, extruding and granulating, wherein the polyurethane elastomer is thermosetting powder selected from Qingdao Mei Heng Plastic powder Co., ltd, and the product number is 002.
Preparation example 11: immersing 0.6kg of carbon nano tube in 15wt% sodium hydroxide solution for 20min, filtering, washing and drying to obtain hydroxylated carbon nano tube; 0.3kg of carbon fiber is subjected to soaking treatment by ethanol solution of silane coupling agent KH550 with concentration of 2.5wt% for 30min, filtering, washing, drying, mixing with hydroxylated carbon nano tube and 1kg of polyurethane elastomer, melting at 190 ℃, extruding and granulating, wherein the polyurethane elastomer is thermosetting powder selected from Qingdao Mei Heng Plastic powder Co., ltd, and the product number is 002.
Preparation example 12: the difference from preparation example 11 is that the hydroxylated carbon nanotubes are not added.
Preparation example 13: the difference from preparation example 11 is that no carbon fiber was added.
Examples
Example 1: a high-transparency high-strength heat-shrinkable film with a thickness of 150 μm comprises a layer A, a layer B, a layer C, a layer D and a layer E which are sequentially bonded, wherein the density of metallocene polyethylene in the layer A and the layer E in the table 1 is 0.916g/cm 3 The melt index was 0.2g/10min and the density of the metallocene polyethylene in the B, C and D layers was 0.918g/cm 3 The melt index is 1g/10min, and can be 3505MC or 2703MC, and 3505MC is taken as an example; the melt index of the low density polyethylene in the A layer, the B layer, the C layer, the D layer and the E layer is 0.9225g/cm 3 The melt index was 0.25g/10min, and the melt index of the linear low density polyethylene was 0.915g/cm 3 The melt index is 0.2g/10min, and the density of the high-density polyethylene is 0.945g/cm 3 The melt index was 0.18g/10min.
The preparation method of the high-transparency high-strength heat-shrinkable film comprises the following steps:
weighing the raw materials of the layer A, the layer B, the layer C, the layer D and the layer E, and respectively and uniformly mixing;
according to the thickness ratio of the layer A, the layer B, the layer C, the layer D and the layer E being 1:1:1:1, the raw materials of each layer are melted, blown, cooled and shaped, pulled, stretched, cut and wound to obtain the high-transparency high-strength polyethylene heat-shrinkable film, wherein the melting temperature is 180 ℃, the blowing ratio is 1:3.8, the cooling roller temperature is 20 ℃, and the winding tension is 80N.
TABLE 1
Example 4: a high-transparency high-strength heat-shrinkable film is different from example 1 in that 15kg of an antifogging agent, which was prepared in preparation example 1, was further added to the layer A.
Example 5: a high-transparency high-strength heat-shrinkable film is different from example 1 in that 10kg of an antifogging agent, which was prepared in preparation example 2, was further added to the layer A.
Example 6: a high-transparency high-strength heat-shrinkable film is different from example 4 in that an antifogging agent in the A layer is produced by production example 3.
Example 7: a high-transparency high-strength heat-shrinkable film is different from example 4 in that an antifogging agent in the A layer is produced from production example 4.
Example 8: a high-transparency high-strength heat-shrinkable film is different from example 4 in that an antifogging agent in the A layer was produced from production example 5.
Example 9: a high-transparency high-strength heat-shrinkable film is different from example 4 in that an antifogging agent in the A layer is produced by production example 6.
Example 10: a high-transparency high-strength heat-shrinkable film is different from example 4 in that an antifogging agent in the A layer is produced by production example 7.
Example 11: a high-transparency high-strength heat-shrinkable film is different from example 4 in that the antifogging agent in the A layer is prepared in preparation example 8.
Example 12: a high-transparency high-strength heat-shrinkable film is different from example 4 in that the antifogging agent in the A layer is prepared in preparation example 9.
Example 13: a high transparency high strength heat shrinkable film differs from example 4 in that the antifogging agent in layer A is xylitol ester.
Example 14: a high-transparency high-strength heat-shrinkable film was distinguished from example 12 in that a surface friction modifier having a particle diameter of 5 μm was adhered to the side of the E layer remote from the D layer by an adhesive, and the surface friction modifier was prepared from preparation 10 in an amount of 50g/m 3 The adhesive is selected from Hua Jishi QIS-3033, and the amount of the adhesive is 20g/m 3 。
Example 15: a high-transparency high-strength heat-shrinkable film was distinguished from example 12 in that a surface friction modifier having a particle diameter of 10 μm was further bonded to the side of the E layer remote from the D layer by an adhesive, the surface friction modifier being prepared in preparation 11 in an amount of 30g/m 3 The adhesive is selected from Hua Jishi QIS-3033, and the amount of the adhesive is 10g/m 3 。
Example 16: a high-transparency high-strength heat-shrinkable film was distinguished from example 12 in that the E layer was further bonded on the side remote from the D layer by an adhesive with a surface friction modifier having a particle diameter of 5 μm, which was prepared from preparation 12 in an amount of 50g/m 3 The adhesive is selected from Hua Jishi QIS-3033, and the amount of the adhesive is 20g/m 3 。
Example 17: a high-transparency high-strength heat-shrinkable film was distinguished from example 12 in that the E layer was further bonded on the side remote from the D layer by an adhesive with a surface friction modifier having a particle diameter of 5 μm, which was prepared from preparation 13 in an amount of 50g/m 3 The adhesive is selected from Hua Jishi QIS-3033, and the amount of the adhesive is 20g/m 3 。
Comparative example
Comparative examples 1-3: a high-transparency high-strength heat-shrinkable film was different from example 1 in that the raw material amounts are shown in Table 2.
TABLE 2
Comparative example 4: an ultrathin low-pressure heat-shrinkable film is formed by co-extrusion of five layers, and comprises an outer layer, a secondary outer layer, a middle layer, a secondary inner layer and an inner layer, wherein the outer layer comprises 70% of low-pressure polyethylene, 20% of special polyethylene for the heat-shrinkable film, and 10% of color master batch and auxiliary materials in percentage by weight; the secondary outer layer, the secondary inner layer and the middle layer are composed of 55% of low-pressure polyethylene, 35% of polyethylene special for the heat-shrinkable film, 10% of color master batch and auxiliary materials; the inner layer consists of 40% and 40% of polyethylene special for the heat shrinkage film, 20% of color master batch and auxiliary materials. The outer layer is calculated according to the thickness percentage: a secondary outer layer: an intermediate layer: secondary inner layer: the thickness ratio of the inner layer is 20 percent: 15%:30%:15%:20%. Mixing the raw materials according to the formula, putting into a host machine, heating to 210 ℃ for extrusion, blowing up according to the proportion of 1:4, cooling and shaping, drawing and stretching, slitting, and finally rolling and warehousing.
Performance test
Heat-shrinkable films were prepared according to the methods in examples and comparative examples, and the properties of the heat-shrinkable films were examined with reference to the following methods, and the examination results are recorded in table 3.
1. Tensile strength and nominal strain at break; determination of the tensile Properties of plastics according to GB/T1040.3-2006 section 3: test conditions for films and sheets.
2. Shrinkage ratio: the detection was carried out according to GB/T13519-2016 polyethylene heat-shrinkable film for packaging.
3. Transparency: the detection is carried out according to GB/T2410-1980 test method for light transmittance and haze of transparent plastics, and the detection wavelength is 500nm.
4. High temperature anti-fog properties: referring to GB4455-2006 agricultural polyethylene blow molding greenhouse film, 200ml of tap water is placed in a disposable water cup, the disposable water cup is placed in a water bath kettle, after the disposable water cup is heated to the set temperature of 60 ℃, the A layer film of the heat shrinkage film faces to a cup opening, the A layer film is bound to the cup opening by rubber bands, and then the film is pressed down to form an angle of 15 degrees with the horizontal plane in a constant-temperature water bath, and the fog situation of the A layer film of the heat shrinkage film is observed and recorded.
5. Surface coefficient of friction of layer E: the detection was carried out according to GB/T10006-2021 determination of the coefficient of friction of Plastic films and sheets.
TABLE 3 Table 3
In examples 1-3, different five-layer raw materials are adopted for blow molding to prepare the heat-shrinkable film, and the heat-shrinkable film has high shrinkage, high tensile strength and nominal stress at break and good transparency.
Examples 4 and 5 are different from example 1 in that antifogging agents prepared in preparation examples 1 and 2 are also used, respectively, and it is shown in table 3 that the heat-shrinkable films prepared in examples 4 and 5 have increased tensile strength, further improved mechanical properties, increased contact angle of the a layer with water, prolonged antifogging time, and good antifogging effect.
Example 6 an antifogging agent prepared in preparation example 3 was used, in which a hydrophilic matrix prepared from chitosan and cellulose nanofibrils was not added, but a casting solution was directly sprayed on polycarbonate, and the tensile strength of the heat-shrinkable film prepared in example 6 was reduced and the antifogging time was shortened, compared with example 4.
Example 7 an antifogging agent prepared in preparation example 4 was used, in which polycarbonate was not used, but a casting solution was sprayed on a hydrophilic substrate made of chitosan and cellulose nanofibrils, and it is shown in table 3 that the tensile strength of the heat-shrinkable film prepared in example 7 was not changed much, the contact angle with water was not changed much, but the antifogging time was significantly shortened.
In examples 8, 9 and 10, the antifogging agents prepared in preparation examples 5, 6 and 7 were used, and in preparation examples 5 and 6, respectively, lotus root fibers and graphene were not added to the casting solution, and in preparation example 7, graphene and lotus root fibers were not added, respectively, the tensile strength of the heat-shrinkable films prepared in examples 8 and 9 was reduced, the antifogging time was shortened, the mechanical properties of the heat-shrinkable films in example 10 were lower than those in examples 8 and 9, and the antifogging effect was further reduced, indicating that the lotus root fibers and graphene could synergistically improve the antifogging effect of the layer a.
The antifogging agents prepared in preparation examples 8 and 9 were used in examples 11 and 12, respectively, and were different from preparation example 1 in that the lotus root filaments were pretreated with hydrophobic silica in preparation examples 8 and 9, and it is shown in table 3 that the heat-shrinkable films prepared in examples 11 and 12 were higher in tensile strength than in example 4, and most importantly, the antifogging effect was enhanced.
Example 13 differs from example 4 in that a commercially available hydrophilic xylitol ester was used as an antifogging agent, and the antifogging effect of the heat shrinkable film was increased as compared with example 1, but was inferior to example 4.
In examples 14 and 15, the surface friction modifiers prepared in preparation examples 10 and 11 were further added to the E layer as compared with example 12, and as shown in Table 3, the surface friction of the E layer was effectively improved in the heat shrinkable films prepared in examples 14 and 15, and the heat shrinkable films were prevented from being unstable when stacked.
The surface friction modifiers prepared in preparation examples 12 and 13 were used in examples 16 and 17, respectively, and the heat-shrinkable films prepared in examples 16 and 17 showed significantly lower surface friction coefficients of the E layer than those of example 14.
Comparative example 1 in comparison with example 1, the use of 3505 type metallocene polyethylene instead of 6026 type metallocene polyethylene and 7042N linear low density polyethylene in the a layer and the E layer produced heat-shrinkable films having lower tensile strength and clarity than example 1.
In comparative example 2, the heat-shrinkable film prepared in comparative example 2 was increased in transparency but decreased in tensile strength, as shown in table 3, by using an equivalent amount of 2420D low-density polyethylene instead of 3505 type metallocene polyethylene, without adding 3505 type metallocene polyethylene to the B layer and the D layer.
Comparative example 3 the raw materials in the a layer and the E layer were changed compared to example 1, the 3505 type metallocene polyethylene was used instead of the 6026 type metallocene polyethylene and the 7042N linear low density polyethylene, and the 3505 type metallocene polyethylene in the B layer and the D layer was replaced with the equivalent amount 2420D low density polyethylene, and the heat shrinkable film prepared in comparative example 3 was reduced in tensile strength, reduced in shrinkage, and deteriorated in transparency compared to example 1.
Comparative example 4 is a five-layer co-extruded heat-shrinkable film prepared in the prior art, which has good heat shrinkage, but low transparency and lower mechanical strength than example 1.
The present embodiment is only for explanation of the present application and is not to be construed as limiting the present application, and modifications to the present embodiment, which may not creatively contribute to the present application as required by those skilled in the art after reading the present specification, are all protected by patent laws within the scope of claims of the present application.
Claims (5)
1. The high-transparency high-strength polyethylene heat-shrinkable film is characterized by comprising an A layer, a B layer, a C layer, a D layer and an E layer which are sequentially bonded from inside to outside;
the layer A and the layer E comprise the following raw materials in parts by weight: 30-50 parts of low-density polyethylene, 15-25 parts of metallocene polyethylene and 30-50 parts of linear low-density polyethylene;
the layer B, the layer C and the layer D all comprise the following raw materials in parts by weight: 3-7 parts of low-density polyethylene, 40-80 parts of high-density polyethylene and 30-40 parts of metallocene polyethylene;
the surface friction modifier is bonded on one side of the E layer far away from the D layer through an adhesive and comprises 1-2 parts by weight of polyurethane elastomer, 0.6-1.6 parts by weight of carbon nano tube and 0.3-0.7 part by weight of carbon fiber;
the preparation method of the surface friction modifier comprises the following steps: treating the carbon nanotubes with sodium hydroxide solution to obtain hydroxylated carbon nanotubes; treating carbon fibers by a silane coupling agent, and then mixing the carbon fibers with the hydroxylated carbon nano tube and the polyurethane elastomer, extruding and granulating;
the average grain diameter of the surface friction modifier is 5-10 mu m, and the dosage of the surface friction modifier is 30-50g/m 3 ；
10-15 parts by weight of antifogging agent is added into the layer A;
the preparation method of the antifogging agent comprises the following steps:
adding chitosan into acetic acid solution with concentration of 1-2wt% to obtain chitosan solution with concentration of 0.5-1wt%, adding cellulose nanofibrils, performing ultrasonic treatment for 30-40min, freeze drying, and pulverizing to obtain hydrophilic matrix;
mixing the hydrophilic matrix with polycarbonate, extruding and granulating to obtain hydrophilic particles;
adding polyvinyl alcohol into deionized water, heating to 80-90 ℃, stirring for 2-3h, adding polytetrafluoroethylene emulsion, graphene and lotus root silk fiber, performing ultrasonic treatment for 20-30min, and defoaming at room temperature for 10-12h to prepare a casting solution;
and uniformly spraying the casting film liquid on the hydrophilic particles, and then freeze-drying.
2. The high-transparency high-strength polyethylene heat-shrinkable film according to claim 1, wherein: the density of the metallocene polyethylene in the A layer and the E layer is 0.916-0.92g/cm 3 The melt index is 0.2-0.22g/10min;
the density of the metallocene polyethylene in the B layer, the C layer and the D layer is 0.918-0.93g/cm 3 The melt index is 1-1.2g/10min;
the density of the low density polyethylene in the A layer, the B layer, the C layer, the D layer and the E layer is 0.910-0.9259g/cm 3 The melt index is 0.25-0.28g/10min; the linear low density polyethylene has a density of 0.915 to 0.918g/cm 3 The melt index is 2-2.1g/10min; the density of the high-density polyethylene is 0.945 to 0.95g/cm 3 The melt index is 0.18-0.19g/10min.
3. The high-transparency high-strength polyethylene heat-shrinkable film according to claim 1, wherein the antifogging agent comprises the following raw materials in parts by weight: 2-3 parts of polycarbonate, 2-3 parts of chitosan, 1-2 parts of cellulose nanofibrils, 1-1.5 parts of polytetrafluoroethylene emulsion, 0.3-0.6 part of graphene, 0.1-0.3 part of lotus root silk fiber, 0.5-1 part of polyvinyl alcohol and 8-10 parts of deionized water.
4. A high transparency high strength polyethylene heat shrinkable film according to claim 3, wherein the lotus root filaments are pretreated by:
dispersing hydrophobic silica into an aqueous solution of polyethylene glycol with the concentration of 3-5wt%, then uniformly spraying the aqueous solution onto lotus root silk fibers, and drying, wherein the mass ratio of the aqueous solution of the hydrophobic silica and the polyethylene glycol to the lotus root silk fibers is 0.3-0.5:0.6-1:1-3.
5. The method for producing a high-transparency high-strength polyethylene heat-shrinkable film according to any one of claims 1 to 4, comprising the steps of:
weighing the raw materials of the layer A, the layer B, the layer C, the layer D and the layer E, and respectively and uniformly mixing;
according to the thickness ratio of the layer A, the layer B, the layer C, the layer D and the layer E being 1:1:1:1, the raw materials of each layer are melted, blown, cooled and shaped, pulled and stretched, cut and rolled to prepare the high-transparency high-strength polyethylene heat-shrinkable film.
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| JP2005329980A (en) * | 2004-05-20 | 2005-12-02 | Heisei Polymer Co Ltd | Heat shrinkable packaging material |
| CN104311949A (en) * | 2014-10-11 | 2015-01-28 | 中国石油化工股份有限公司 | High-strength polyethylene material for preparing heat shrinkable film, and preparation method of high-strength polyethylene material |
| CN104426414A (en) * | 2013-08-23 | 2015-03-18 | 纳米新能源（唐山）有限责任公司 | Power generation effect-improved friction generator and preparation method thereof |
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| JP2005329980A (en) * | 2004-05-20 | 2005-12-02 | Heisei Polymer Co Ltd | Heat shrinkable packaging material |
| CN104426414A (en) * | 2013-08-23 | 2015-03-18 | 纳米新能源（唐山）有限责任公司 | Power generation effect-improved friction generator and preparation method thereof |
| CN104311949A (en) * | 2014-10-11 | 2015-01-28 | 中国石油化工股份有限公司 | High-strength polyethylene material for preparing heat shrinkable film, and preparation method of high-strength polyethylene material |
| CN110216960A (en) * | 2019-06-03 | 2019-09-10 | 黄山永新股份有限公司 | A kind of bloom low haze PE heat shrink films and preparation method thereof |
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