Disclosure of Invention
Based on the above, the invention aims to provide an integrated easy-to-recycle in-mold label film for a high-density polyethylene bottle, and a preparation method and application thereof, wherein the integrated easy-to-recycle in-mold label film for the high-density polyethylene bottle can be labeled in a mold to meet the bonding fastness required by labeling, and can be stripped from the high-density polyethylene bottle in a stripping manner during recycling, thereby being beneficial to recycling of single materials.
In order to achieve the above purpose, the present invention adopts the following technical scheme.
The integrated molding easy-to-recycle in-mold label film for the high-density polyethylene bottle comprises a surface layer, a coloring layer, a foaming supporting layer, a connecting layer and a hot melt adhesive layer which are sequentially arranged, wherein the surface layer comprises polypropylene and an anti-blocking agent, the coloring layer comprises polypropylene and titanium pigment, the adding proportion of the titanium pigment in the coloring layer is 5-30wt%, the foaming supporting layer comprises polypropylene and calcium carbonate, the adding proportion of the calcium carbonate in the foaming supporting layer is 5-30wt%, the connecting layer comprises polypropylene and maleic anhydride grafted polypropylene, the content of the maleic anhydride grafted polypropylene in the connecting layer is 30-50wt%, the hot melt adhesive layer comprises propylene-butene copolymer and ethylene-butene copolymer, and the content of the propylene-butene copolymer in the hot melt adhesive layer is 40-60deg.C.
According to the integrated easy-to-recycle in-mold label film for the high-density polyethylene bottle, through the matching of the structures of all layers and the design of the components of all layers, the adhesion fastness of the integrated easy-to-recycle in-mold label film for the high-density polyethylene bottle and the high-density polyethylene bottle not only meets the in-mold labeling requirement, but also can be peeled off cleanly from the surface of the high-density polyethylene bottle in a peeling way during recycling, so that the separation of the high-density polyethylene bottle and the integrated easy-to-recycle in-mold label film for the high-density polyethylene bottle is realized, and the integrated easy-to-recycle in-mold label film for the high-density polyethylene bottle is respectively used as a single material for classification recycling, and the problem that the integrated easy-to-recycle in-mold label film for the high-density polyethylene bottle is self-material and ink on the surface causes recycling pollution of the high-density polyethylene bottle is avoided.
The surface layer is used for surface printing, and the ink can be printed on the surface of the surface layer. By adding an anti-blocking agent to the surface layer, the anti-blocking effect of the surface layer can be improved, and blocking can be prevented. The coloring layer is a white layer and plays a role of white background, the coloring layer adopts polypropylene and 5-30wt% of titanium dioxide, so that the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle can be used as a product form of the white label film, can be used as the white background of the surface layer during surface printing, reduces the white background printing process during surface printing, saves printing cost, has the addition ratio of 5-30wt% of titanium dioxide in the coloring layer, has high price and high product cost if the addition ratio of titanium dioxide in the coloring layer is higher than 30wt%, easily causes peeling delamination between the surface layer and the coloring layer and between the coloring layer and the foaming supporting layer on the other hand, affects interlayer bonding fastness, and cannot play a role of coloring effect if the addition ratio of titanium dioxide in the coloring layer is lower than 5wt%, and has obviously improved light transmittance and cannot be effectively used as the white background of surface printing of the surface layer.
The foaming supporting layer plays a role in force supporting and cavitation, the foaming supporting layer adopts polypropylene and 5-30wt% of calcium carbonate, due to the addition of the calcium carbonate, when the integrally formed easily-recycled in-mold label film for the high-density polyethylene bottle stretches (in the preparation process), stretching pore forming is caused, the cavitation effect is generated, when the integrally formed easily-recycled in-mold label film for the high-density polyethylene bottle carries out in-mold labeling, due to the fact that the in-mold labeling temperature is generally higher (the in-mold labeling temperature is generally 170-190 ℃, the melting point temperature of the integrally formed easily-recycled in-mold label film for the high-density polyethylene bottle is 160-165 ℃), the integrally formed easily-recycled in-mold label film for the high-density polyethylene bottle can be melted, cavitation collapse occurs during melting, and the appearance of the integrally formed easily-recycled in-mold label film for the high-density polyethylene bottle after the integrally formed easily-recycled in-mold label film for the high-density polyethylene bottle is formed on high-density polyethylene bottle is met. The addition ratio of the calcium carbonate in the foaming supporting layer is 5-30wt%, if the addition ratio of the calcium carbonate in the foaming supporting layer is lower than 5wt%, the surface of the integrated easily-recycled in-mold label film for the high-density polyethylene bottle is not easy to form orange peel concave-convex patterns when the integrated easily-recycled in-mold label film is applied to the high-density polyethylene bottle, and if the addition ratio of the calcium carbonate in the foaming supporting layer is higher than 30wt%, delamination is easy to occur between the coloring layer and the foaming supporting layer and between the foaming supporting layer and the connecting layer, and the interlayer bonding fastness is affected.
The connecting layer is used for connecting the foaming supporting layer and the hot melt adhesive layer, the connecting layer adopts polypropylene and maleic anhydride grafted polypropylene to connect the foaming supporting layer and the hot melt adhesive layer, and the bonding fastness of the foaming supporting layer, the connecting layer and the hot melt adhesive layer is improved through the interlocking action between high polymer chains and the bonding action between maleic anhydride grafted polypropylene and inorganic filler layers, so that the peeling delamination is prevented. The polypropylene in the connecting layer can be interlocked with the propylene-butene copolymer in the hot melt adhesive layer, and the bonding firmness of the connecting layer and the hot melt adhesive layer is improved through the inter-polymer molecular chain winding and the interlocking effect between partial propylene chain segments. The content of the maleic anhydride grafted polypropylene in the connecting layer is 30-50wt%, and if the content of the maleic anhydride grafted polypropylene is lower than 30wt%, the connecting layer and the foaming supporting layer have poor bonding fastness and are easy to delaminate. If the content of the maleic anhydride-grafted polypropylene is more than 50wt%, the cost is too high.
The hot melt adhesive layer is composed of a propylene-butene copolymer and an ethylene-butene copolymer, wherein the propylene-butene copolymer is a propylene-butene copolymer which is composed of propylene as a main body and butene as a copolymerization unit, the ethylene-butene copolymer is an ethylene-butene copolymer which is composed of ethylene as a main body and butene as a copolymerization unit, and the ethylene-butene copolymer is favorable for heat lamination during in-mold molding with a high-density polyethylene bottle. The hot melt adhesive layer is composed of a propylene-butene copolymer and an ethylene-butene copolymer, on one hand, the bonding fastness of the hot melt adhesive layer and the connecting layer is enhanced by realizing a high molecular chain interlocking effect between the propylene-butene copolymer and the polypropylene in the connecting layer, and on the other hand, the propylene-butene copolymer and the ethylene-butene copolymer can realize a cooperative interlocking, so that after the integrally formed easy-recycling in-mold label film for the high-density polyethylene bottle is applied to the high-density polyethylene bottle, the problem that the material residue of the integrally formed easy-recycling in-mold label film for the high-density polyethylene bottle causes recycling pollution of the high-density polyethylene bottle is avoided based on the high molecular chain interlocking effect between the propylene-butene copolymer in the hot melt adhesive layer and the polypropylene in the connecting layer and the cooperative interlocking effect between the propylene-butene copolymer and the ethylene-butene copolymer in the connecting layer during peeling. In yet another aspect, the propylene-butene copolymer and the ethylene-butene copolymer, through the introduction of the comonomer butene, reduce the melting point of the copolymer, enabling the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottles to be in-mold labeled at blow molding process temperatures without generating bubbles. The content of the propylene-butene copolymer in the hot melt adhesive layer is 40-60wt%, and if the content of the propylene-butene copolymer is lower than 40wt%, the content of the ethylene-butene copolymer is higher, because the hot melt adhesive layer is mainly thermally bonded with a high-density polyethylene bottle through the ethylene-butene copolymer, the bonding fastness of the hot melt adhesive layer and the high-density polyethylene bottle is possibly too high, so that part of materials remain on the high-density polyethylene bottle during peeling and recycling. If the content of the propylene-butene copolymer is higher than 60wt%, the content of the ethylene-butene copolymer is lower, and the hot melt adhesive layer cannot be firmly attached to the high-density polyethylene bottle, so that the label is not firmly attached between the in-mold label film which is integrally formed and easy to recycle and used for the high-density polyethylene bottle and the high-density polyethylene bottle.
Further, the polypropylene in the surface layer, the coloring layer, the foaming supporting layer and the connecting layer is homo-polypropylene, the melt index is 2.5-3.5g/10min (melt index test condition: 230 ℃ C., 2.16 KG), and the isotacticity is 95-97%.
Further, in the connecting layer, the grafting ratio of the maleic anhydride in the maleic anhydride grafted polypropylene is 0.5-1wt%, and the melt index of the maleic anhydride grafted polypropylene is 2.5-3.5g/10min (melt index test condition: 230 ℃ C., 2.16 KG). If the grafting rate of maleic anhydride in the maleic anhydride grafted polypropylene is low, the binding force between the connecting layer and the foaming supporting layer is insufficient, and delamination is easy to generate. The melt index of the maleic anhydride grafted polypropylene is selected to be 2.5-3.5g/10min (melt index test condition: 230 ℃ C., 2.16 KG) and is similar to the melt index of the polypropylene of the connecting layer and the foaming supporting layer, so that on one hand, the mechanical strength is ensured, and on the other hand, the maleic anhydride grafted polypropylene and the polypropylene of the connecting layer and the foaming supporting layer are better dispersed and mutually fused.
Further, in the hot melt adhesive layer, the content of butene in the propylene-butene copolymer is 4-10wt%, the melting point of the propylene-butene copolymer is 75-100 ℃, and the melt index is 3-15g/10min (melt index test condition: 230 ℃ C., 2.16 KG). If the content of butene in the propylene-butene copolymer is lower than 4wt%, and/or the melting point of the propylene-butene copolymer is higher than 100 ℃, the integrally formed easily recycled in-mold label film for the high-density polyethylene bottle is used for in-mold labeling on the high-density polyethylene bottle, the problem of bubble generation caused by weak adhesion is easy, and if the content of butene in the propylene-butene copolymer is higher than 10wt%, and/or the melting point of the propylene-butene copolymer is lower than 75deg.C, the integrally formed easily recycled in-mold label film for the high-density polyethylene bottle is easy to generate adhesive roll breakage after longitudinal stretching in the preparation process, the appearance of the film surface is affected, and the label is generated due to normal temperature viscosity caused by the excessively low melting point when the label film is stored at normal temperature.
Further, in the hot melt adhesive layer, the content of butene in the ethylene-butene copolymer is 5-25wt%, the melting point of the ethylene-butene copolymer is 75-100 ℃, and the melt index is 3-15g/10min (melt index test condition: 230 ℃ C., 2.16 KG). If the content of butene in the ethylene-butene copolymer is lower than 5wt% and/or the melting point of the ethylene-butene copolymer is higher than 100 ℃, the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle is easy to attach and not firm to generate bubble problems when in-mold labeling, and the interlocking capability between the ethylene-butene copolymer and the propylene-butene copolymer polymer chain is weakened, so that the adhesion fastness between the ethylene-butene copolymer and the high-density polyethylene bottle is too high to remain on the surface of the high-density polyethylene bottle, and if the content of butene in the ethylene-butene copolymer is higher than 25wt% and/or the melting point of the propylene-butene copolymer is lower than 75 ℃, the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle is easy to generate adhesive roll breakage after longitudinal stretching in the preparation process, influences the appearance of the film surface, and generates normal temperature adhesion due to the excessively low melting point when being stored at normal temperature, so that the label continuous phenomenon is generated.
Further, the addition proportion of the anti-blocking agent in the surface layer is 0.1-1wt%, the anti-blocking agent is silicon dioxide or polymethyl methacrylate, and the average particle size is 4-5 mu m. The anti-blocking effect of the skin layer is improved by adding 0.1-1wt% of an anti-blocking agent to the skin layer. Silicon dioxide or polymethyl methacrylate is used as an anti-blocking agent, and the average particle size of the anti-blocking agent is 4-5 mu m, so that the anti-blocking agent can protrude out of the surface layer to achieve an anti-blocking effect. This is a conventional technical means in the art, and will not be described in detail herein.
Further, in the coloring layer, the average grain diameter of the titanium dioxide is 0.2-0.4 mu m, and the synthetic process of the titanium dioxide is a chloridizing process. The coloring effect of the coloring layer can be improved by adopting titanium dioxide with the average particle diameter of 0.2-0.4 mu m synthesized by a chlorination process.
Further, in the foaming supporting layer, the average particle diameter of the calcium carbonate is 0.9-2 μm. The calcium carbonate with the average particle size of 0.9-2 mu m is adopted, so that the integrally formed easily-recycled in-mold label film for the high-density polyethylene bottle is conveniently stretched into holes with proper size in the preparation process, cavitation is facilitated, in-mold labeling is carried out on the integrally formed easily-recycled in-mold label film for the high-density polyethylene bottle, cavitation collapse occurs, and orange peel concave-convex appearance is formed.
Further, the connecting layer further comprises an antistatic agent, the content of the antistatic agent in the connecting layer is 0.5-1wt%, and the antistatic agent is glyceryl monostearate or ethylamine. The antistatic agent is added into the connecting layer in an amount of 0.5-1wt% so as to improve the antistatic effect of the integrally formed easily recyclable in-mold label film for the high-density polyethylene bottle.
Further, the thickness of the surface layer is 1-1.5 mu m, the thickness of the coloring layer is 2-10 mu m, the thickness of the foaming supporting layer is 50-80 mu m, the thickness of the connecting layer is 5-10 mu m, and the thickness of the hot melt adhesive layer is 3-10 mu m.
The invention further designs the thickness of each layer, the thickness of the surface layer is 1-1.5 mu m, the average grain diameter based on the anti-blocking agent is 4-5 mu m, if the thickness of the surface layer is less than 1 mu m, the anti-blocking agent is easy to fall off from the surface layer, a guide roller is polluted, the integrally formed easy-recycling in-mold label film for the high-density polyethylene bottle is easy to scratch in the preparation process, and if the thickness of the surface layer is more than 1.5 mu m, the height of the protruding surface layer of the anti-blocking agent is insufficient, the integrally formed easy-recycling in-mold label film for the high-density polyethylene bottle is easy to adhere, and the anti-blocking effect is reduced. The thickness of the coloring layer is 2-10 mu m, if the thickness of the coloring layer is higher than 10 mu m, the product cost is high, and if the thickness of the coloring layer is lower than 2 mu m, the coloring effect is not achieved, the light transmittance is obviously improved, so that the coloring layer cannot be effectively used as a white background when the surface layer is printed on the surface. The thickness of the foaming supporting layer is 50-80 mu m, if the thickness of the foaming supporting layer is lower than 50 mu m, the stiffness of the integrally formed easily-recoverable in-mold label film for the high-density polyethylene bottle is lower, so that the label cannot be Shan Zhangli to affect the label feeding effect, and if the thickness of the foaming supporting layer is higher than 80 mu m, the strength of the integrally formed easily-recoverable in-mold label film for the high-density polyethylene bottle is overlarge, and the integrally formed easily-recoverable in-mold label film for the high-density polyethylene bottle is easy to deform after being applied to the high-density polyethylene bottle (because of the post shrinkage phenomenon after the high-density polyethylene bottle is formed, and when the strength of the integrally formed easily-recoverable in-mold label film for the high-density polyethylene bottle is far higher than the shrinkage stress, the deformation of the high-density polyethylene bottle can be caused). The connecting layer is formed by specifically selecting polypropylene and maleic anhydride grafted polypropylene and controlling the layer thickness to connect the foaming layer (polypropylene and calcium carbonate) and the hot melt adhesive layer (propylene-butene copolymer and ethylene-butene copolymer), the thickness of the connecting layer is 5-10 mu m, if the thickness of the connecting layer is less than 5 mu m, the foaming supporting layer and the hot melt adhesive layer are easy to delaminate, and if the thickness of the connecting layer is more than 10 mu m, the film cost is increased. The thickness of the hot melt adhesive layer is 3-10 mu m, if the thickness of the hot melt adhesive layer is higher, the in-mold label film which is formed integrally and is easy to recycle is easy to be uneven due to the fact that the melting point of the hot melt adhesive layer is low and the shrinkage rate is higher, and if the thickness of the hot melt adhesive layer is lower, the adhesive strength of the hot melt adhesive layer is lower and the adhesion is not firm.
The invention also provides a preparation method of the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle, which adopts an integrally forming process and comprises the following steps:
and after the raw materials of all layers are respectively melted by an extruder, converging the raw materials in a coextrusion die head to form an integrally formed thick sheet, and forming the integrally formed easily-recycled in-die label film for the high-density polyethylene bottle by casting sheet forming, longitudinal stretching, transverse stretching, traction corona rolling, aging treatment, slitting and die pressing.
The invention also provides an application of the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle in the high-density polyethylene bottle.
The integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle is integrated with the high-density polyethylene bottle to form the high-density polyethylene bottle with the in-mold label. The application of the integrally formed and easily recycled in-mold label film for the high-density polyethylene bottle in the high-density polyethylene bottle is characterized in that the high-density polyethylene is melted at 170-190 ℃ and then extruded through an annular die to form a cylindrical blank, then the cylindrical blank is placed into a die with any one of the integrally formed and easily recycled in-mold label films for the high-density polyethylene bottle, an air blowing rod is inserted after cutting the blank, the air blowing rod is used for ventilation (the air blowing pressure is 0.4-0.5 MPa), the blank is expanded, the hot melt adhesive layer of any one of the integrally formed and easily recycled in-mold label films for the high-density polyethylene bottle is melted by waste heat of the blank, and finally the integrally formed and easily recycled in-mold label film for the high-density polyethylene bottle and a plastic part are melted into a whole body through cooling, so that the high-density polyethylene bottle with an in-mold label is formed.
After the high-density polyethylene bottle with the in-mold label is used, when the high-density polyethylene bottle needs to be recovered, the integrally formed easy-to-recover in-mold label film for the high-density polyethylene bottle can be easily torn off from the high-density polyethylene bottle in a stripping mode, and no label material remains on the surface of the high-density polyethylene bottle, so that the in-mold label film with the ink and the high-density polyethylene bottle can be recovered in a classified mode, the recycling of a single material is facilitated, and the transparent high-density polyethylene bottle is particularly suitable for the transparent high-density polyethylene bottle.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention has the innovation points that the structure, the components and the thickness of each layer of the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle are adjusted, so that after the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle is applied to a blow-molded product high-density polyethylene bottle, the bonding fastness of the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle not only meets the in-mold labeling requirement, but also can be cleanly stripped from the surface of the high-density polyethylene bottle in a stripping manner during recycling, thereby realizing the classified recycling of the high-density polyethylene bottle and the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle and the recycling pollution problem caused by the self material of the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle and the surface ink thereof.
(2) The second innovation point of the invention is that the integrated molding easy-to-recycle in-mold label film for the high-density polyethylene bottle is prepared by adopting an integrated molding processing mode, specifically realized by a coextrusion-biaxial stretching process, and realized by replacing an off-line hot melt adhesive spraying mode.
(3) The third innovation point of the invention is that the connecting layer is arranged between the foaming supporting layer and the hot melt adhesive layer, and the bonding fastness between the foaming supporting layer and the hot melt adhesive layer is improved through the connecting layer by adopting the interlocking action between polymer chains and the bonding action between the maleic anhydride grafted polypropylene and inorganic filler layers, so that the peeling and layering of the film are prevented.
For a better understanding and implementation, the present invention is described in detail below with reference to the drawings.
Detailed Description
The present invention will be described more fully hereinafter in order to facilitate an understanding of the present invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
As an embodiment of the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottles of the present invention, please refer to fig. 1, which is a five-layer structure comprising a skin layer 1, a coloring layer 2, a foam supporting layer 3, a connecting layer 4 and a hot melt adhesive layer 5 sequentially disposed.
Wherein the main components of each layer are as follows:
The surface layer 1 comprises polypropylene and an anti-blocking agent;
a coloring layer 2 of polypropylene and titanium dioxide;
The foaming supporting layer 3 is made of polypropylene and calcium carbonate;
The connecting layer 4 is made of polypropylene, maleic anhydride grafted polypropylene and antistatic agent;
and the hot melt adhesive layer 5 is propylene-butene copolymer and ethylene-butene copolymer.
The integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle can adopt a biaxial stretching film forming process, a tape casting film forming process and a blow molding film forming process, and the biaxial stretching film forming process is preferably selected.
The method is realized by adopting an integrated forming processing mode, in particular to a coextrusion-biaxial stretching process, and comprises the following steps of respectively melting all layers of raw materials through an extruder, converging the raw materials in a coextrusion die head to form an integrated thick sheet, and forming the integrated easily-recoverable in-die label film for the high-density polyethylene bottle through casting sheet forming, longitudinal stretching, transverse stretching, traction corona rolling, ageing treatment, slitting and compression molding.
Referring to fig. 2, a is a raw material, B is a melt, C is a thick sheet, D is a film parent roll, E is a film finished product, F is a film molded finished product, G is an extruder extrusion process, H is a quenching process, I is a biaxial stretching process, J is a corona-winding process, K is an aging slitting process, and L is a molding process.
The production process flow is that the screened raw materials A of all layers are premixed according to a design formula, stirred uniformly, weighed, calculated and put into proportion, sent into all extruders, plasticized into melt B in an extrusion process G of the extruders, the melt is conveyed through a pipeline and filtered by a filter, distributed to a die head through a flow channel for coextrusion, then the melt B is quenched by a quenching process H of a chilled roller to form a thick sheet C, and the thick sheet C is subjected to a biaxial stretching process I to form a film, wherein the biaxial stretching process can be a stepwise biaxial stretching process of longitudinal stretching and then transverse stretching or a synchronous biaxial stretching process of longitudinal and transverse synchronous stretching. The film is subjected to cooling, two-side trimming, traction thickness measurement and corona-winding procedures J to obtain a film master roll D, the film master roll D is subjected to an ageing slitting procedure K to form a film finished product E, then a mould pressing procedure L is carried out on a hot melt adhesive layer of the film finished product E, and finally a film mould pressing finished product F is formed.
The temperature of the extruder, the runner, the pipeline, the filter and the die head used in the method is controlled at 230-260 ℃, the quenching temperature is controlled at 25-40 ℃, the process temperature of longitudinal and transverse stretching is controlled at 60-180 ℃ in the step stretching process, the longitudinal stretching ratio is controlled at 4.0-6.0 times, the transverse stretching ratio is controlled at 7.0-10.0 times, the process temperature of longitudinal and transverse stretching is controlled at 150-180 ℃ in the synchronous stretching process, the longitudinal stretching ratio is controlled at 4.0-10.0 times, and the transverse stretching ratio is controlled at 4.0-10.0 times. The film after the biaxial stretching process H can be cooled at room temperature, and is subjected to trimming and traction thickness measurement on two sides to be rolled into a film parent roll D, and the film D is then subjected to die pressing at 110-150 ℃ and 40-80m/min to finally obtain a film die pressing finished product F, namely the integrally formed easily-recycled in-die label film for the high-density polyethylene bottle.
The invention relates to an application process flow of an integrally formed easily recyclable in-mold label film for a high-density polyethylene bottle, which comprises the following steps:
Referring to fig. 3, according to the common general knowledge in the art, a film molding product F is first subjected to a printing process P, which includes but is not limited to a common process such as rotary printing, offset printing, flexography, etc., to obtain a semi-finished product M, then subjected to a die cutting process Q to obtain Shan Zhangmo in-mold labels N, the in-mold labels N are stacked together and placed on a label holder, and finally subjected to a negative pressure label feeding process R and an in-mold labeling process S to obtain a high-density polyethylene bottle O with in-mold labels.
The invention relates to an integrated easy-to-recycle in-mold label film recycling method for a high-density polyethylene bottle, which comprises the following steps:
Referring to fig. 4, the in-mold label is separated from the high-density polyethylene bottle by manually peeling the high-density polyethylene bottle O with the in-mold label, and after separation, no in-mold label material remains on the surface of the high-density polyethylene bottle, so that the two materials are recovered in a classified manner, and the secondary use is convenient.
In the following examples or comparative examples:
description 1. In-mold label film and high-density polyethylene film heat seal strength measurement method:
The test simulates the adhesive fastness of an in-mold label film and a high-density polyethylene bottle after in-mold labeling. Through the casting process, a high-density polyethylene film with the thickness of 100 mu m is obtained, then an in-mold label film and the high-density polyethylene film are subjected to heat sealing by a heat sealing instrument under the conditions of 135 ℃ and 0.18MPa for 1 second, then the film is kept stand for 3 minutes in a test environment, a sample is cut into strips with the width of 15mm and the length of 15cm, finally a heat sealing interface is peeled off, and the heat sealing strength is measured by a universal tensile machine.
Description 2. Method for measuring interlayer binding fastness:
the test marks the stripping difficulty of the hot melt adhesive layer of the inner label film of the mold. The method comprises the steps of performing off-line corona treatment on a hot melt adhesive layer of an in-mold label film to enable the surface tension of the hot melt adhesive layer to reach 40mN/m, compounding the hot melt adhesive layer with the hot melt adhesive layer surface of the in-mold label film by utilizing a high adhesive tape, rolling back and forth three times on the film surface at a speed of about 12cm/s under the dead weight of 2.5kg by utilizing a pressing roll, requiring no bubble between the in-mold label film and the high adhesive tape, cutting a sample into strips with the width of 15mm and the length of 15cm after the sample is placed for 3 minutes in a test environment, finally stripping the in-mold label film from the high adhesive tape, measuring the stripping force by utilizing a universal tensile machine, wherein the stripping force is not less than 10N/15mm, and the in-mold label film still does not delaminate, evaluating the delamination phenomenon, and evaluating the delamination phenomenon of the in-mold label film, namely the delamination phenomenon, the in-mold label film is evaluated, and the delamination degree is evaluated.
Example 1
The embodiment provides an integrally formed easy-recycling in-mold label film for a high-density polyethylene bottle, and the specific structure of the label film is shown in fig. 1, and the label film comprises a surface layer 1, a coloring layer 2, a foaming supporting layer 3, a connecting layer 4 and a hot melt adhesive layer 5 which are sequentially arranged.
Wherein:
The components of the surface layer 1 are 99.5wt% of isotactic polypropylene (isotacticity is 97%, density is 0.905g/cm3, melt index is 3g/10min, melt index test condition is that the melt temperature is 230 ℃, load weight is 2.16 kg) and 0.5wt% of silicon dioxide (average particle size is 5 μm);
The coloring layer 2 comprises 85wt% of isotactic polypropylene (isotacticity is 97%, density is 0.905g/cm3, melt index is 3g/10min, melt index test condition is that the melting temperature is 230 ℃, load weight is 2.16 kg) and 15wt% of titanium dioxide (chloridizing process, rutile type, average grain diameter is 0.3 μm);
the foaming supporting layer 3 comprises 85wt% of isotactic polypropylene (with isotacticity of 97%, density of 0.905g/cm3, melt index of 3g/10min, melt index test condition: melt temperature of 230 ℃ and load weight of 2.16 kg) and 15wt% of calcium carbonate (with average particle size of 1.2 μm);
The tie layer 4 had a composition of 50wt% isotactic polypropylene (isotacticity 97%, density 0.905g/cm3, melt index 3g/10min, melt index test conditions: melt temperature 230 ℃, load weight 2.16 kg), 49.5wt% maleic anhydride grafted polypropylene (maleic anhydride grafting ratio 1wt%, density 0.905g/cm3, melt index 3g/10min, melt index test conditions: melt temperature 230 ℃, load weight 2.16 kg) and 0.5wt% glyceryl monostearate;
The composition of the hot melt adhesive layer 5 was 50wt% of a propylene-butene copolymer (butene content 9%, density 0.879g/cm3, melt index 8g/10min, melt index test conditions: melt temperature 230 ℃ C., load weight 2.16 kg) and 50wt% of an ethylene-butene copolymer (butene content 18wt%, density 0.905g/cm3, melt index 7.5g/10min, melt index test conditions: melt temperature 230 ℃ C., load weight 2.16 kg).
The embodiment also provides a preparation method of the integrally formed easily recyclable in-mold label film for the high-density polyethylene bottle, referring to fig. 2, the specific production process flow comprises the steps of premixing the screened raw materials A according to a design formula, uniformly stirring, weighing, calculating the input proportion, feeding into each extruder, plasticizing into a melt B in an extrusion process G of the extruder, conveying the melt through a pipeline, filtering by a filter, distributing the melt B to a die head through a flow channel for coextrusion, forming a thick sheet C through a quenching process H of a chilled roller, and forming a film through a biaxial stretching process I, wherein the biaxial stretching process is a step-by-step double-stretching process of longitudinal stretching and transverse stretching. Shaping, cooling, trimming two sides, traction thickness measurement, corona and master winding J, thus obtaining a film master winding D, forming a film finished product E after the film master winding D is subjected to an ageing slitting process K, then performing a mould pressing process L on a hot melt adhesive layer of the film finished product E, and finally forming a film mould pressing finished product F.
Wherein, production facility is flat membrane method substep biaxially oriented polypropylene production line that Bruker (BRUECKNER) company of germany provided, and main extruder (be used for foaming supporting layer 3) screw rod is the diameter is 150mm, and the length-diameter ratio is 33:1 single screw extruder, and 4 auxiliary extruders (be used for top layer 1, dyed layer 2, tie layer 4 and hot melt adhesive layer 5 respectively) are the single screw extruder of screw diameter 120mm, length-diameter ratio is 30:1. The temperature of the extruder is 250 ℃ except for the feeding section, the temperature of each section of a filter, a runner and a die head is 250 ℃, the quenching (casting sheet) temperature is 30 ℃, the corresponding temperatures of a preheating zone, a stretching zone and a shaping zone which are passed through by a longitudinal stretching process are 140 ℃, 135 ℃ and 140 ℃, the stretching ratio is 5.0, the corresponding temperatures of the preheating zone, the stretching zone and the shaping zone which are passed through by transverse stretching are 176 ℃, the stretching zone is 157 ℃, the shaping zone is 168 ℃, the stretching ratio is 8.5, the production speed is 300m/min, and the corona strength of the surface layer surface is 30 W.min/m2. After the film is cut, the film is molded under the condition of 130 ℃ and 60m/min, and finally a film molded finished product is obtained.
The total thickness of the integrally formed easy-recycling in-mold label film for the high-density polyethylene bottle of this example was 105. Mu.m, the thickness of the surface layer 1 was 1. Mu.m, the thickness of the coloring layer 2 was 10. Mu.m, the thickness of the foaming layer 3 was 79. Mu.m, the thickness of the connecting layer 4 was 10. Mu.m, and the thickness of the hot melt adhesive layer was 5. Mu.m.
The heat sealing strength of the in-mold label film and the high-density polyethylene film in the integrated easy-to-recycle in-mold label film for the high-density polyethylene bottle is 3.2N/15mm, and the interlayer bonding fastness is measured without layering.
Referring to fig. 3, an in-mold label film F is first subjected to a printing process P including, but not limited to, a common process such as rotary printing, offset printing, flexography, etc. to obtain a semi-finished product M, then subjected to a die cutting process Q to obtain Shan Zhangmo in-mold labels N, the in-mold labels N are stacked together and placed on a label holder, and finally the in-mold label is obtained by a negative pressure label feeding process R and an in-mold label sticking process S.
Referring to fig. 4, the process for recycling the in-mold label film for the integrated molding of the high-density polyethylene bottle in the embodiment separates the in-mold label from the high-density polyethylene bottle by manually peeling the high-density polyethylene bottle O with the in-mold label, and after the separation, no in-mold label material remains on the surface of the high-density polyethylene bottle, so that the two materials are recycled in a classified manner, and the secondary use is convenient. Based on the measurement of interlayer bonding fastness, the method has the advantages that the interlayer bonding strength is not less than 10N/15mm, the heat sealing strength of the in-mold label film and the high-density polyethylene film is far higher than 3.2N/15mm, the in-mold label film can be torn off from the surface of the high-density polyethylene bottle without layering, and no label material remains on the surface of the high-density polyethylene bottle.
For ease of comparison, the differences in formulation versus performance of the layers were designed based on example 1, with only the proportions of the materials changed, and a systematic comparison was made below in the form of a list. The method comprises the following steps:
Example 2
This example is substantially the same as example 1 except that in the integrally formed easy recycling in-mold label film for high density polyethylene bottle of this example, the hot melt adhesive layer 5 is composed of 40wt% of propylene-butene copolymer and 60wt% of ethylene-butene copolymer. See table 1 for details.
Comparative example 1
This comparative example is substantially the same as example 1 except that in the integrally formed easy recycling in-mold label film for high density polyethylene bottle of this comparative example, the hot melt adhesive layer 5 is composed of 30wt% of propylene-butene copolymer and 70wt% of ethylene-butene copolymer. See table 1 for details.
Comparative example 2
This comparative example is substantially the same as example 1 except that in the integrally formed easy recycling in-mold label film for high density polyethylene bottle of this comparative example, the hot melt adhesive layer 5 is composed of 70wt% of propylene-butene copolymer and 30wt% of ethylene-butene copolymer. See table 1 for details.
TABLE 1 formulation composition of the layers of examples 1-2 and comparative examples 1-2
Example 3
This example is substantially the same as example 1 except that in the integrally formed easy-to-recycle in-mold label film for a high density polyethylene bottle of this example, the propylene-butene copolymer used in the hot melt adhesive layer 5 had a butene content of 4wt% and the ethylene-butene copolymer had a butene content of 5wt%. See table 2 for details.
Example 4
This example is substantially the same as example 1 except that in the integrally formed easy-to-recycle in-mold label film for a high density polyethylene bottle of this example, the propylene-butene copolymer used in the hot melt adhesive layer 5 had a butene content of 10% by weight and the ethylene-butene copolymer had a butene content of 25% by weight. See table 2 for details.
Table 2 formulation composition of each layer of examples 3-4
Comparative example 3
This comparative example is substantially the same as example 1 except that in the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottle of this comparative example, the ethylene-butene copolymer used in the hot melt adhesive layer 5 had a butene content of 2% by weight. See table 3 for details.
Comparative example 4
This comparative example is substantially the same as example 1 except that in the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottle of this comparative example, the ethylene-butene copolymer used in the hot melt adhesive layer 5 has a butene content of 30% by weight. See table 3 for details.
Table 3 composition of the layer formulations of comparative examples 3-4
Comparative example 5
This comparative example is substantially the same as example 1 except that in the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottle of this comparative example, the butene content of the propylene-butene copolymer used in the hot melt adhesive layer 5 was 2% by weight. See table 4 for details.
Comparative example 6
This comparative example is substantially the same as example 1 except that in the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottle of this comparative example, the propylene-butene copolymer used in the hot melt adhesive layer 5 has a butene content of 15% by weight. See table 4 for details.
Table 4 composition of the layer formulations of comparative examples 5-6
Example 5
This example is substantially the same as example 1 except that in the integrally formed easy-to-recycle in-mold label film for a high-density polyethylene bottle of this example, the content of polypropylene in the colored layer 2 was 70wt% and the content of titanium dioxide was 30wt%. See table 5 for details.
Comparative example 7
This comparative example was substantially the same as example 1 except that in the integrally formed easy-to-recycle in-mold label film for high-density polyethylene bottle of this comparative example, the content of polypropylene in the colored layer 2 was 60% by weight and the content of titanium dioxide was 40% by weight. See table 5 for details.
Example 6
This example is substantially the same as example 1 except that in the integrally formed easy-to-recycle in-mold label film for a high density polyethylene bottle of this example, the polypropylene content in the foamed support layer 3 was 70wt% and the calcium carbonate content was 30wt%. See table 5 for details.
Comparative example 8
This comparative example was substantially the same as example 1 except that in the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottle of this comparative example, the content of polypropylene in the foamed support layer 3 was 60% by weight and the content of calcium carbonate was 40% by weight. See table 5 for details.
TABLE 5 formulation composition of the layers of examples 5-6 and comparative examples 7-8
Example 7
This example is substantially the same as example 5 except that in the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottle of this example, the content of polypropylene in the tie layer 4 was 69.5wt% and the content of maleic anhydride-grafted polypropylene was 30wt%. See table 6 for details.
Comparative example 9
This comparative example was substantially the same as example 7 except that in the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottle of this comparative example, the content of polypropylene in the tie layer 4 was 79.5wt% and the content of maleic anhydride-grafted polypropylene was 20wt%. See table 6 for details.
Example 8
This example is substantially the same as example 7 except that in the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottle of this example, the grafting ratio of maleic anhydride in the maleic anhydride-grafted polypropylene employed in the tie layer 4 was 0.5wt%. See table 6 for details.
Comparative example 10
This comparative example was substantially the same as example 7 except that in the integrally formed easy-to-recycle in-mold label film for high density polyethylene bottle of this comparative example, the grafting ratio of maleic anhydride in the maleic anhydride-grafted polypropylene employed in the tie layer 4 was 0.2wt%. See table 6 for details.
TABLE 6 results of layer formulation composition and performance testing for examples 7-8 and comparative examples 9-10
Referring to tables 1-6, the integrally formed and easily recycled in-mold label film for high-density polyethylene bottles of the invention, through the design of each layer structure, components and thickness, has the bonding fastness which meets the in-mold labeling requirement after being applied to blow molding products of high-density polyethylene bottles, and can be cleanly stripped from the surface of the high-density polyethylene bottles in a stripping manner during recycling, thereby realizing the classified recycling of the high-density polyethylene bottles and the integrally formed and easily recycled in-mold label film for high-density polyethylene bottles and avoiding the recycling pollution problem caused by the self material of the integrally formed and easily recycled in-mold label film for high-density polyethylene bottles and the surface ink thereof.
In the hot melt adhesive layer 5 for the integrally formed easy-to-recycle in-mold label film for high-density polyethylene bottle of comparative example 1, the content of propylene-butene copolymer was low, the content of ethylene-butene copolymer was high, and after the integrally formed easy-to-recycle in-mold label film for high-density polyethylene bottle of comparative example 1 was applied to high-density polyethylene bottle and peeled off, trace materials remained on the high-density polyethylene bottle and could not be effectively recycled as a single material.
In the hot melt adhesive layer 5 for the integrally formed easy-to-recycle in-mold label film of the high-density polyethylene bottle of comparative example 2, the content of the propylene-butene copolymer was high, the content of the ethylene-butene copolymer was low, and the integrally formed easy-to-recycle in-mold label film for the high-density polyethylene bottle of comparative example 2 had the condition of weak labeling with the application to the high-density polyethylene bottle.
In the hot melt adhesive layer 5 for the integrally formed easy-to-recycle in-mold label film of the high-density polyethylene bottle of comparative example 3, the content of butene in the ethylene-butene copolymer is low, the integrally formed easy-to-recycle in-mold label film of the high-density polyethylene bottle of comparative example 3 is applied to the high-density polyethylene bottle, air bubbles are easily generated due to weak adhesion during in-mold labeling, and the interlocking capability between the ethylene-butene copolymer and the propylene-butene copolymer polymer chain is weakened, so that the adhesion fastness of the ethylene-butene copolymer and the high-density polyethylene bottle is too high, and trace materials remain on the high-density polyethylene bottle and cannot be effectively recycled as a single material.
In the hot melt adhesive layer 5 for the integrally formed easy-recycling in-mold label film of the high-density polyethylene bottle of comparative example 4, the content of butene in the ethylene-butene copolymer is high, and the adhesive roller is easy to be damaged by longitudinal stretching in the preparation process, so that the appearance of the film surface is influenced.
In the hot melt adhesive layer 5 for the integrally formed easy-to-recycle in-mold label film of the high-density polyethylene bottle of comparative example 5, the content of butene in the propylene-butene copolymer was low, the integrally formed easy-to-recycle in-mold label film of the comparative example 5 for the high-density polyethylene bottle was applied to the high-density polyethylene bottle, and was easily attached to the high-density polyethylene bottle in the in-mold labeling to generate bubbles, and trace materials remained on the high-density polyethylene bottle in the peeling recovery, and could not be effectively recycled as a single material.
In the hot melt adhesive layer 5 for the integrally formed easy-recycling in-mold label film of the high-density polyethylene bottle of comparative example 6, the content of butene in the propylene-butene copolymer is high, and the adhesive roller is easy to break after longitudinal stretching in the preparation process, so that the appearance of the film surface is affected.
In the coloring layer 2 of the integrated molding easy-recycling in-mold label film for the high-density polyethylene bottle of the comparative example 7, the content of titanium dioxide is high, the production cost is high, layering is easy between the surface layer 1 and the coloring layer 2 and between the coloring layer 2 and the foaming supporting layer 3, and after the integrated molding easy-recycling in-mold label film for the high-density polyethylene bottle of the comparative example 7 is applied to the high-density polyethylene bottle and stripped and recycled, a large amount of materials remain on the high-density polyethylene bottle and cannot be effectively recycled as a single material.
In the foam supporting layer 3 of the integrated easy-to-recycle in-mold label film for high-density polyethylene bottle of comparative example 8, the content of calcium carbonate is high, delamination is easy between the coloring layer 2 and the foam supporting layer 3 and between the foam supporting layer 3 and the connecting layer 4, and after the integrated easy-to-recycle in-mold label film for high-density polyethylene bottle of comparative example 8 is applied to the high-density polyethylene bottle and stripped and recycled, a large amount of materials remain on the high-density polyethylene bottle and cannot be effectively recycled as a single material.
In the foaming connecting layer 4 of the integral molding easy-recycling in-mold label film for the high-density polyethylene bottle of the comparative example 9, the content of maleic anhydride grafted polypropylene is low, the bonding between the maleic anhydride grafted polypropylene and calcium carbonate in the foaming supporting layer 3 is poor, the bonding fastness between the connecting layer and the foaming supporting layer is easy to laminate, and the integral molding easy-recycling in-mold label film for the high-density polyethylene bottle of the comparative example 9 is easy to laminate and is peeled off and recycled, and a large amount of materials remain on the high-density polyethylene bottle and cannot be effectively recycled as a single material.
In the foaming connecting layer 4 of the integral molding easy-recycling in-mold label film for the high-density polyethylene bottle of the comparative example 10, the grafting rate of maleic anhydride in the maleic anhydride grafted polypropylene is low, the bonding force between the connecting layer and the foaming supporting layer is insufficient, delamination is easy to occur, and after the integral molding easy-recycling in-mold label film for the high-density polyethylene bottle of the comparative example 10 is applied to the high-density polyethylene bottle and stripped for recycling, a large amount of materials remain on the high-density polyethylene bottle and cannot be effectively recycled as a single material.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that modifications and improvements can be made by those skilled in the art without departing from the spirit of the invention, and the invention is intended to encompass such modifications and improvements.