A surface anti-corrosion and breathable valve bag and its preparation method

Abstract

This application relates to the field of packaging bags, and specifically discloses a surface anti-corrosion and breathable valve bag and its preparation method. The surface anti-corrosion and breathable valve bag includes kraft paper and a polymer film located inside the kraft paper. Small holes are punched in both the kraft paper and the polymer film. It is characterized in that an adhesive is contained between the kraft paper and the polymer film. The adhesive comprises the following raw materials in parts by weight: 1-4 parts of nitrile rubber, 10-20 parts of EVA, 35-65 parts of high-density polyethylene, 0.5-1 part of compatibilizer, 1-3 parts of coupling-modified inorganic filler, 10-20 parts of ethylene-octene copolymer, and 1-2 parts of antioxidant. The surface anti-corrosion and breathable valve bag of this application has the advantages of good anti-corrosion property and breathability, tight bonding between the kraft paper and the polymer film, and not being easily delaminated.

Description

Technical Field

[0001] The present application relates to the technical field of packaging bags, and more specifically, it relates to a surface anti-corrosion and breathable valve bag and a preparation method thereof. Background Art

[0002] With the environmental protection requirements, carbon black, as the main raw material in the rubber industry, needs to be packed in valve bags. As a type of packaging bag, when packing carbon black materials, the valve bag is fed from the valve opening at the top or bottom, and becomes square after filling the materials, having the advantages of neat and beautiful stacking, high packaging efficiency, convenient transportation, and low breakage rate.

[0003] When packing nanoscale solid material fumed silica with a valve bag, since the materials just loaded into the packaging bag contain free chlorine and some hydrochloric acid gas, and the pH value is between 3 and 4 at this time, the corrosion of kraft packaging paper is very serious, and the kraft paper can be corroded into shredded paper, thus losing the packaging function. Moreover, when packing fumed silica, air flow packaging is adopted, and there is a large amount of gas in the packaging bag. Since the kraft paper has good sealing performance, the gas in the bag cannot be discharged in time, the air pressure in the bag is large, and the materials cannot be loaded into the packaging bag.

[0004] In the prior art, the Chinese invention patent application document with the application number CN2004100208078 discloses a surface anti-corrosion and breathable industrial paper packaging bag for nanomaterials, which is made of kraft packaging paper, with a layer of film coated on the inner side of the packaging bag, and small holes are punched from the inside to the outside. The film materials are polyethylene, polypropylene, biaxially oriented polyethylene, ethylene-vinyl acetate copolymer, etc.

[0005] The above-mentioned packaging bag coats a polymer material on the inner side of the kraft paper to solve the anti-corrosion problem, and punches large holes in the kraft paper to solve the problem of discharging corrosive gas in the packaging bag. However, it uses the method of film laminating to compound high-pressure polyethylene and kraft paper. The main component of kraft paper is lignin, which is a complex non-crystalline polymer, while high-pressure polyethylene belongs to thermoplastic polymer materials. The two belong to different types of materials, so the compatibility is not good, and the bonding strength between the kraft paper and the high-pressure polyethylene film on its surface needs to be improved. Summary of the Invention

[0006] In order to improve the bonding strength between the kraft paper and the surface film material, prevent the valve bag from delaminating and affecting the packaging performance, the present application provides a surface anti-corrosion and breathable valve bag and a preparation method thereof.

[0007] In the first aspect, the present application provides a surface anti-corrosion and breathable valve bag, adopting the following technical solution:

[0008] A surface anti-corrosion and breathable valve bag, comprising kraft paper and a polymer film located inside the kraft paper. Small holes are punched in both the kraft paper and the polymer film. An adhesive is contained between the kraft paper and the polymer film. The adhesive comprises raw materials in the following parts by weight: 1-4 parts of nitrile rubber, 10-20 parts of EVA, 35-65 parts of high-density polyethylene, 0.5-1 part of compatibilizer, 1-3 parts of coupling-modified inorganic filler, 10-20 parts of ethylene-octene copolymer, and 1-2 parts of antioxidant.

[0009] By adopting the above technical solution, because the particle size of inorganic nanoparticles is small and the specific surface area is large, they are extremely easy to agglomerate, so it is not easy to disperse evenly in the adhesive. Using a coupling agent to activate and modify the filler can make the inorganic filler disperse well in the adhesive, form a chemical bond between the filler and the matrix resin, realize the interfacial coupling effect, and enhance the interfacial bonding strength; adding coupling-modified inorganic filler to the adhesive makes the surface energy of the inorganic filler transition from inorganic to organic, thereby increasing the interfacial bonding strength between the kraft paper and the polymer film to improve and enhance the packaging performance of the valve bag.

[0010] Using a polyethylene layer as the inner layer makes use of the strong stability of polyethylene, avoids chemical reactions between the objects stored inside and the polyethylene layer, and improves the anti-corrosion ability of the bag body.

[0011] Optionally, after mixing the inorganic filler and a rare earth coupling agent with an addition amount of 1.5-2% of the mass of the inorganic filler, heating to 75-80 °C, mixing and stirring for 8-10 min, and cooling, a coupling-modified inorganic filler is obtained.

[0012] By adopting the above technical solution, after the inorganic filler is treated with a rare earth coupling agent, there are two different groups in the rare earth coupling agent molecule. One group can react with the surface chemical groups of the inorganic substance to form a strong chemical bond, that is, form hydroxyl groups with trace moisture on the surface of the powder body, and carry out chemical reactions or physical adsorption with the coupling agent to form a strong chemical bond. The other group has good compatibility with organic polymer materials and can physically entangle with the long chains of polymer materials, thereby firmly combining two materials with different properties, that is, connecting the interface between the inorganic material and the polymer material to form a network structure, increasing the mutual bonding force, and thus improving the bonding strength between the kraft paper and the polymer film.

[0013] Optionally, the inorganic filler comprises nano-silica and nano-calcium carbonate with a mass ratio of 1:0.8-1.

[0014] By adopting the above technical solution, nano-silica and nano-calcium carbonate have a large specific surface area and a large number of hydroxyl groups on the surface, so their reaction activity is high, which can effectively improve the compatibility and bonding force between the adhesive and the kraft paper and the polymer film.

[0015] Optionally, the polymer film comprises raw materials in the following parts by weight: 8.5 - 9 parts of EVA, 1 - 1.5 parts of high-density polyethylene, and 0.5 - 0.8 parts of HDPE-Cu composite particles with a copper shell and HDPE particles as the core.

[0016] By adopting the above technical solution, the HDPE-Cu composite particles are formed by electroless plating of copper on HDPE particles, and a closely combined and uniformly distributed copper coating is formed on the surface of HDPE, thereby forming composite particles with HDPE particles as the core and copper as the shell. After the composite particles are melted, they have excellent fluidity, and copper is uniformly distributed in the polymer film, which can form a dense tissue structure without holes and cracks, making the impedance arc of the polymer film larger, increasing the resistance to corrosion reaction, slowing down the corrosion rate, and improving the corrosion resistance of the polymer film.

[0017] Optionally, a reinforcing layer is coated on the side of the polymer film away from the adhesive. The reinforcing layer comprises raw materials in the following parts by weight: 10 - 20 parts of EVA, 5 - 10 parts of epoxy butyl rubber, 3 - 7 parts of polyethyleneimine-modified mesoporous titanium dioxide, and 1 - 5 parts

[0018] nitrogen-doped carbon dots, and 1 - 3 parts of polyvinyl alcohol fibers.

[0019] By adopting the above technical solution, due to the addition of HDPE-Cu composite particles in the polymer film, at the initial stage of acid corrosion, more copper ions penetrate, resulting in the corrosion of the polymer film. However, as time goes by, the penetration of copper ions tends to be stable, and the filled copper can effectively isolate the corrosive gas from penetrating to the surface of the kraft paper through the pores, hindering the diffusion of corrosive substances, so that the polymer film has a strong long-term anti-corrosion ability; a reinforcing layer is coated on the polymer film. The nitrogen-doped carbon dots contain abundant carbon, nitrogen, etc., and can form an adsorption film, effectively protecting the copper from being corroded by acidic gases and improving the weakening of the initial corrosion resistance caused by the addition of HDPE-Cu composite particles; after the mesoporous titanium dioxide is modified by polyethyleneimine, a large number of polyethyleneimine chains with amino groups are attached to its surface. Since the molecular chain of polyethyleneimine is 600 and is relatively short, it can better adhere to the mesoporous titanium dioxide. When the polyethyleneimine-modified mesoporous silica contacts the epoxy polymer chain in the epoxy butyl rubber, the amino group on the polyethyleneimine chain will react with the epoxy group on the epoxy polymer chain, so as to be tightly combined together, thus forming a coating with a large number of embedded mesoporous titanium dioxide and a relatively dense structure on the polymer film. There are extremely small pores on the surface of the polymer film, and the corrosive gas in the air will penetrate through the polymer film to the kraft paper and corrode the kraft paper. Therefore, a reinforcing layer is coated on the inner side of the polymer film. When the corrosive gas enters the polymer film through the reinforcing layer, the mesoporous silica can play a hindering role, either changing its movement path or passing through the inside of the mesoporous titanium dioxide, so as to extend the path of the corrosive gas reaching the kraft paper. Since the reinforcing layer contains a large amount of mesoporous titanium dioxide, due to the cumulative effect, the movement path of the corrosive gas is greatly extended, thus improving the anti-corrosion performance of the valve pocket.

[0020] Optionally, the nitrogen-doped carbon dots are prepared by the following method: Dissolve citric acid and polyethyleneimine in ultrapure water, then heat at 180-190 °C for 15-16 h, filter with a 0.45 μm filter membrane, dialyze and then freeze-dry to obtain the nitrogen-doped carbon dots.

[0021] By adopting the above technical solution, polyethyleneimine contains a large number of vinyl groups, amino groups, and nitrogen-carbon bonds. It is an obvious polymer of corrosion inhibitor, has a strong adsorption effect, can interact with metal cations to form metal complexes, helps to form a covering layer on the metal surface to achieve the protection of the metal. However, it is toxic and does not meet the concept of sustainable development. Carbon dots have good biocompatibility. Using citric acid as a carbon source and an oxygen source, nitrogen-doped carbon dots are synthesized as corrosion inhibitors. The heteroatoms with lone pair electrons in it interact with the empty orbitals of copper to form coordination bonds. The strong force of the chemical bond makes the corrosion inhibitor molecules or ions firmly adsorbed on the copper surface, thereby reducing the corrosion of copper and improving the initial corrosion resistance of the HDPE-Cu composite particles.

[0022] Optionally, the polyethyleneimine-modified mesoporous titanium dioxide is prepared by the following method: adding mesoporous titanium dioxide into absolute ethanol, adding polyethyleneimine, heating to 120-140 °C, stirring for 7-8 h, centrifuging, washing, and drying to obtain polyethyleneimine-modified mesoporous titanium dioxide.

[0023] By adopting the above technical solution, a large number of polyethyleneimine chains are attached to the mesoporous titanium dioxide. The -NH2 on the polyethyleneimine chain can react with the epoxy groups in the epoxy butyl rubber. With the mesoporous titanium dioxide as the central core, the strengthening layer is cured more tightly. In addition, since the strengthening layer contains a large number of mesoporous titanium dioxide particles, the diffusion channels of corrosive gases are blocked or extended, improving the anti-corrosion performance of the valve bag.

[0024] Optionally, the polyvinyl alcohol fiber is prepared by the following method: dissolving polyvinyl alcohol in deionized water to prepare a shell solution with a concentration of 15-20 wt%, dissolving BTA in oleic acid to prepare a core solution with a concentration of 28-30 wt%;

[0025] Electrospinning the shell solution and the core solution with a coaxial needle nozzle to obtain polyvinyl alcohol fibers.

[0026] By adopting the above technical solution, using polyvinyl alcohol as the shell material and oleic acid and BTA as the core materials, polyvinyl alcohol fibers are prepared by electrospinning. Under acidic conditions, BTA is preferentially released, thus achieving the anti-corrosion effect.

[0027] In a second aspect, the present application provides a method for preparing a surface anti-corrosion and breathable valve bag, adopting the following technical solution:

[0028] A method for preparing a surface anti-corrosion and breathable valve bag, adhesive preparation: mixing nitrile rubber, EVA, high-density polyethylene, coupling-modified inorganic filler, ethylene-octene copolymer, and antioxidant, extruding and pelletizing to obtain the adhesive;

[0029] Valve bag preparation: melting the adhesive and brushing it on kraft paper, laminating a polymer film on the adhesive, and drying to obtain the substrate;

[0030] Punching and bag making: punching holes in the substrate, slitting, corner cutting, and heat sealing to obtain the valve bag.

[0031] By adopting the above technical solution, melting the adhesive and brushing it on kraft paper, and then laminating the polymer film on the adhesive, thereby bonding the kraft paper and the polymer film, enhancing the adhesion between the polymer film and the kraft paper, making the layer structure of the valve bag tightly connected and not easily delaminated.

[0032] Optionally, before punching and bag making, the substrate is processed as follows: 10-20 parts by weight of EVA, 5-10 parts of epoxy butyl rubber, 3-7 parts of polyethyleneimine modified mesoporous titanium dioxide, 1-5 parts of nitrogen-doped carbon dots, and 1-3 parts of polyvinyl alcohol fiber are mixed and then extruded and granulated, and then coated on the polymer film by hot melting. After drying, a reinforcing layer is obtained.

[0033] By adopting the above technical solution, a reinforcing layer is provided on the polymer film, which can further improve the corrosion resistance of the polymer film to acidic gases.

[0034] In summary, the present application has the following beneficial effects:

[0035] 1. Since the present application uses an adhesive to composite kraft paper and a polymer film, and the adhesive is made of materials such as EVA, high molecular polyethylene, nitrile rubber, and coupling-modified filler, the coupling-modified inorganic filler can form a transition between the kraft paper and the polymer film, improving the interfacial bonding strength between the kraft paper and the polymer film; moreover, using nitrile rubber and EVA as the base materials of the adhesive, when the made adhesive is used for a valve pocket without kraft paper, the valve pocket packaging does not need to be disassembled, and it can be put into the rubber mixing equipment together with fumed silica, improving the feeding efficiency, avoiding pouring carbon black out of the valve pocket, which will increase the impurity content due to the contact of carbon black with air, and reducing the harm caused by dust during carbon black feeding to the human body, and avoiding the valve pocket being treated as waste and resulting in resource waste.

[0036] 2. In the present application, it is preferably to use high-density polyethylene, EVA, and HDPE-Cu composite particles to prepare the polymer film, and the made polymer film has high mechanical strength and good corrosion resistance.

[0037] 3. In the present application, it is preferably to coat a reinforcing layer on the inner side of the polymer film. The reinforcing layer contains nitrogen-doped carbon dots, polyethyleneimine modified mesoporous titanium dioxide, and polyvinyl alcohol fiber, etc. The nitrogen-doped carbon dots can adsorb on copper metal, improving the initial corrosion resistance of the polymer film, while the polyethyleneimine modified mesoporous titanium dioxide and polyvinyl alcohol fiber can improve the long-term corrosion resistance of the polymer film. Specific Embodiments

[0038] Preparation Examples 1-3 of Coupling-Modified Inorganic Filler

[0039] Preparation Example 1: 1 kg of inorganic filler and a rare earth coupling agent with an addition amount of 1.5% of the mass of the inorganic filler are put into a high-speed mixer, heated to 75 °C, mixed and stirred for 10 min, and then discharged after cooling to 40 °C to obtain a coupling-modified inorganic filler. The inorganic filler includes nano-silica and nano-calcium carbonate with a mass ratio of 1:1. The average particle size of the nano-calcium carbonate is 50 nm, the particle size of the nano-silica is 100-200 nm, and the rare earth coupling agent model is WOT, selected from Guangdong Weilinna.

[0040] Preparation Example 2: 3 kg of inorganic filler and a rare earth coupling agent with an addition amount of 1.5% of the mass of the inorganic filler were put into a high-speed mixer, heated to 75 °C, mixed and stirred for 10 min, and discharged after cooling to 40 °C to obtain a coupling-modified inorganic filler. The inorganic filler includes nano-silica and nano-calcium carbonate with a mass ratio of 1:1. The average particle size of the nano-calcium carbonate is 50 nm, and the particle size of the nano-silica is 100 - 200 nm. The model of the rare earth coupling agent is WOT, selected from Guangdong Weilinna.

[0041] Preparation Example 3: The difference from Preparation Example 1 is that an equal amount of silane coupling agent KH550 is used to replace the rare earth coupling agent.

[0042] Example

[0043] Example 1: A surface anti-corrosion and breathable valve bag includes kraft paper and a polymer film on the inner side of the kraft paper. Small holes are punched on both the kraft paper and the polymer film. The vertical and horizontal arrangement of the small holes is 3×5 mm, and the hole diameter is 1 mm. The polymer film is a high-density polyethylene film with a thickness of 0.1 mm. There is an adhesive between the polymer film and the kraft paper, and the dosage of the adhesive is 12 g / m 2 , and the raw material dosage of the adhesive is shown in Table 1. Among them, nitrile rubber is prepared by copolymerizing acrylonitrile monomer and butadiene. The mass content of the acrylonitrile monomer is 25%. The mass content of vinyl acetate in EVA is 25%, the melt index is 150 g / 10 min, and the density is 0.95 g / cm 3 , the model is Korea Hunan VA900, the model of the high-density polyethylene is HTA001HD, the compatibilizer is high-density polyethylene grafted maleic anhydride with a grafting rate of 1%, selected from Dow GR205 of the United States, the ethylene-octene copolymer is selected from Dow 8540 of the United States, the antioxidant is antioxidant 1010, and the coupling-modified inorganic filler is made from Preparation Example 1.

[0044] The preparation method of the above surface anti-corrosion and breathable valve bag includes the following steps:

[0045] Adhesive preparation: Mix nitrile rubber, EVA, high-density polyethylene, coupling-modified inorganic filler, ethylene-octene copolymer and antioxidant, melt, extrude and pelletize at 170 °C to obtain the adhesive;

[0046] Valve bag preparation: After the adhesive is melted, it is brushed on the kraft paper, and the polymer film is laminated on the adhesive and dried to obtain the substrate. The brushing speed of the adhesive is 20 m / min, the temperature of the drying tunnel is 70 °C, and the lamination pressure is controlled at 120 MPa;

[0047] Punching and bag making: Punch holes in the substrate, and through slitting, corner cutting and heat sealing, a valve bag is obtained. Slitting is to slit the punched substrate into individual valve bag bodies, and the overall length of each individual valve bag body is 800 mm; Corner cutting is to cut off the four angles of each individual valve bag body respectively, and the corner cutting size is 70*70 mm; Heat sealing is to heat seal the two ends of the valve bag body after corner cutting respectively. When heat sealing, the temperature of the upper and lower hot knives is 140 °C, and the heat sealing time is 0.9 seconds.

[0048] Table 1 Raw material dosages of adhesives in Examples 1-3

[0049] Raw materials / kg Example 1 Example 2 Example 3 Nitrile rubber 3 4 1 EVA 14 20 10 High-density polyethylene 50 65 35 Compatibilizer 0.8 1 0.5 Coupling modified inorganic filler 1 3 2 Ethylene-octene copolymer 15 20 10 Antioxidant 1.5 2 1

[0050] Example 2: A surface anti-corrosion and breathable valve bag, which is different from Example 1 in that the raw material dosages of the adhesive are as shown in Table 1, and the coupled and modified inorganic filler is made from Preparation Example 2.

[0051] Example 3: A surface anti-corrosion and breathable valve bag, which is different from Example 1 in that the raw material dosages of the adhesive are as shown in Table 1.

[0052] Example 4: A surface anti-corrosion and breathable valve bag, which is different from Example 1 in that the coupling modifier in the adhesive is made from Preparation Example 3.

[0053] Example 5: A surface anti-corrosion and breathable valve bag, which is different from Example 1 in that the raw materials of the polymer film include the following raw materials: 9 kg of EVA, 1 kg of high-density polyethylene, and 0.8 kg of HDPE-Cu composite particles with a copper shell and HDPE particles as the core. The mass content of vinyl acetate in EVA is 25%, the melt index is 150 g / 10 min, and the density is 0.95 g / cm 3 , the model is Korea Hunan VA900, the high-density polyethylene is selected from Qatar Petrochemical HHM55028BN, the average size of the HDPE-Cu composite particles with a copper shell and HDPE particles as the core is 85 μm, the thickness of the copper shell is 1 μm, and the HDPE-Cu composite particles are prepared by forming a copper coating on the surface of HDPE particles by electroless copper plating. The specific method is as follows: The HDPE particles of the model Qatar Petrochemical HHM55028BN are ultrasonically cleaned at room temperature for 10 min to remove surface oil stains, and then soaked in the roughening solution at room temperature for 10 min to make the surface of the HDPE particles rough, increase the surface area and improve the surface hydrophilicity. The roughening solution is a mixture of CrO3 with a concentration of 400 g / L and sulfuric acid with a concentration of 150 mL / L with a mass ratio of 1:1. Then soak in the sensitizing solution at room temperature for 10 min and soak in the activating solution at room temperature for 10 min. Sensitization makes the surface of the HDPE particles adsorb a layer of Sn with strong reducibility 2+, for reducing silver ions in the activation solution. The sensitization solution includes SnCl2 with a concentration of 20 g / L and concentrated hydrochloric acid with a concentration of 40 mL / L at a mass ratio of 1:1. The activation solution includes a silver nitrate solution with a concentration of 3 g / L, into which 6 mol / L ammonia water solution is dropped until the precipitate dissolves. The HDPE particles are taken out from the activation solution, washed with deionized water, and then immersed in the electroless copper plating solution to plate copper at room temperature for 25 minutes.

[0054] The preparation method of the above surface anti-corrosion and breathable valve bag includes the following steps:

[0055] Preparation of the polymer film: Mix EVA, high-density polyethylene, and HDPE-Cu composite particles with copper as the shell and HDPE particles as the core, heat to 180 °C and melt, then blow the film to obtain the polymer film;

[0056] Preparation of the adhesive: Mix nitrile rubber, EVA, high-density polyethylene, coupling-modified inorganic filler, ethylene-octene copolymer, and antioxidant, melt, extrude, and granulate at 170 °C to obtain the adhesive;

[0057] Preparation of the valve bag: After melting the adhesive, brush it on kraft paper, laminate the polymer film on the adhesive, and dry to obtain the substrate. The brushing speed of the adhesive is 20 m / min, the temperature of the drying tunnel is 70 °C, and the lamination pressure is controlled at 120 MPa;

[0058] Punching and bag making: Punch holes in the substrate, and through slitting, corner cutting, and heat sealing, obtain the valve bag. Slitting is to slit the punched substrate into individual valve bag bodies, and the overall length of a single valve bag body is 800 mm; Corner cutting is to cut off the four corners of a single valve bag body respectively, and the corner cutting size is 70*70 mm; Heat sealing is to heat seal the two ends of the valve bag body after corner cutting is completed. When heat sealing, the temperature of the upper and lower hot knives is 140 °C, and the heat sealing time is 0.9 seconds.

[0059] Example 6: A surface anti-corrosion and breathable valve bag, which is different from Example 5 in that the HDPE-Cu composite particles with copper as the shell and HDPE particles as the core are not added to the polymer film.

[0060] Example 7: A surface anti-corrosion and breathable valve bag, which is different from Example 5 in that 20 kg of EVA, 10 kg of epoxy butyl rubber, 7 kg of polyethyleneimine-modified mesoporous titanium dioxide, 5 kg of nitrogen-doped carbon dots, and 3 kg of polyvinyl alcohol fibers are mixed and then extruded and granulated. After melting, it is coated on the polymer film at a coating amount of 10 g / m 2 to obtain a strengthening layer after drying. The mass content of vinyl acetate in EVA is 25%, the melt index is 150 g / 10 min, and the density is 0.95 g / cm 3, model number is Hunan VA900 from South Korea. The epoxy butyl rubber is made by the following method: Cut the butyl rubber into pieces, dissolve it with n-hexane to make a rubber solution with a concentration of 15wt%, add m-chloroperbenzoic acid, stir and react at 45°C for 45 minutes, wash with sodium hydroxide solution, and then wash with deionized water until the rubber solution becomes neutral. Flocculate with ethanol and vacuum dry at 50°C. The molar ratio of the double bond to m-chloroperbenzoic acid is 1:1.1. The polyethyleneimine-modified mesoporous titanium dioxide is made by the following method: Add 20g of mesoporous titanium dioxide to 200ml of absolute ethanol, add 10g of polyethyleneimine, heat to 120°C, stir for 8 hours, then centrifuge at a speed of 6000rpm for 20 minutes, wash, and dry. The nitrogen-doped carbon dots are made by the following method: Dissolve 10g of citric acid and 60g of polyethyleneimine in 300mL of ultrapure water, then heat at 180°C for 16 hours, filter with a 0.45μm filter membrane, dialyze in ultrapure water with a 1000Da dialysis membrane for 24 hours, change the water every 4 hours, and then freeze-dry. The polyvinyl alcohol fiber is made by the following method: Dissolve polyvinyl alcohol with deionized water to make a shell solution with a concentration of 15wt%. Dissolve BTA (benzotriazole) with oleic acid to make a core solution with a concentration of 28wt%. Electrospin the shell solution and the core solution with a coaxial needle nozzle. The spinning voltage is 20kv, the distance from the coaxial needle nozzle to the drum receiver is 15cm, the inner diameter of the coaxial needle is 0.6mm, the outer diameter is 0.9mm, and the volume of the syringe is 10ml.

[0061] Example 8: A surface anti-corrosion and breathable valve bag, different from Example 7 in that polyethyleneimine-modified mesoporous titanium dioxide is not added to the reinforcing layer.

[0062] Example 9: A surface anti-corrosion and breathable valve bag, different from Example 7 in that polyvinyl alcohol fiber is not added to the reinforcing layer.

[0063] Example 10: A surface anti-corrosion and breathable valve bag, different from Example 7 in that nitrogen-doped carbon dots are not added to the reinforcing layer.

[0064] Comparative Example

[0065] Comparative Example 1: A surface anti-corrosion and breathable valve bag, different from Example 1 in that the coupling-modified inorganic filler is not added.

[0066] Comparative Example 2: A surface anti-corrosion and breathable valve bag, different from Example 1 in that the inorganic filler is not treated with coupling modification.

[0067] Comparative Example 3: An industrial paper packaging bag made of a surface anti-corrosion and breathable nanomaterial. The preparation method is as follows: After thoroughly mixing 100 parts of high-pressure polyethylene and 5 parts of fumed silica, it is double-sided film-coated on the inner and outer surfaces of the kraft paper packaging bag 2 with a coater, and the thickness is 0.2 mm; it is applicable to solid substances within the pH range of 4.5 - 9; to increase the exhaustibility, pores are punched from the inside out, and a solid punching nail is used to roll and punch small holes 3 with a vertical and horizontal arrangement of 5×10 mm and a hole diameter of 0.7 mm.

[0068] Performance detection test

[0069] Prepare valve bags according to the methods in the examples and comparative examples, and conduct performance detection with reference to the following methods. Record the detection results in Table 2.

[0070] 1. Tensile strength: Detect according to GB / T1040.3 - 2006 "Determination of Tensile Properties of Plastics - Part 3 Test Conditions for Films and Sheets".

[0071] 2. Corrosion resistance: Immerse the made valve bag in a hydrochloric acid solution with a pH value of 4 for 24 hours, then detect the tensile strength. Immerse it for 30 days and detect the tensile strength again. Calculate the reduction rate of the tensile strength by the method of (tensile strength after immersion - initial tensile strength) / initial tensile strength × 100%.

[0072] 3. Adhesion between the polymer film and kraft paper: Detect according to GB / T30768 - 2014 "Paper and Plastic Composite Films and Bags for Food Packaging".

[0073] Table 2 Performance Detection of Surface Anti-corrosion and Breathable Valve Bags

[0074]

[0075] In the valve bags made in Example 1 and Example 2, the kraft paper and the polymer film are compounded using an adhesive, and the adhesives in Example 1 and Example 2 respectively use the coupled and modified inorganic fillers made in Preparation Example 1 and Preparation Example 2. As shown in Table 2, the valve bags made in Example 1 and Example 2 have a high adhesion and a large adhesive force between the kraft paper and the polymer film, are not easy to delaminate, have a high tensile strength and strong tensile resistance, and after immersion in an acidic solution, the decreasing trend of the tensile strength is similar to that of Comparative Example 3, and have good corrosion resistance.

[0076] The adhesive in Example 4 uses the coupled and modified inorganic filler made in Preparation Example 3. Compared with Example 1, the adhesion between the kraft paper and the polymer film in the valve bag made in Example 4 decreases, and the tensile strength weakens, but it still has good corrosion resistance.

[0077] Compared with Example 1, in Example 5, a polymer film was prepared using high-density polyethylene, EVA, and HDPE-Cu composite particles. The valve bags made in Example 5 were immersed in an acidic solution, and the decrease rate of tensile strength increased at 24 h but decreased at 30 d, indicating that the polymer film prepared in Example 5 can further improve the long-term corrosion resistance of the valve bags.

[0078] Compared with Example 5, in Example 6, HDPE-Cu composite particles were not added to the polymer film. As shown in Table 2, after the valve bags prepared in Example 6 were immersed in hydrochloric acid solution for 24 h, the decrease rate of tensile strength was smaller than that in Example 5, but the decrease rate of tensile strength after 30 d increased, indicating that although the addition of HDPE-Cu composite particles will reduce the initial anti-corrosion effect of the polymer film, it can improve the long-term anti-corrosion effect of the polymer film.

[0079] Compared with Example 5, in Example 7, a reinforcing layer was also provided on the polymer film. As shown in Table 2, after the valve bags prepared in Example 7 were immersed in hydrochloric acid, the decrease in tensile strength after 24 h and 30 d was smaller than that in Example 5, indicating that the reinforcing layer can further enhance the corrosion resistance of the polymer film.

[0080] Compared with Example 7, in Example 8, polyethyleneimine-modified mesoporous titanium dioxide was not added, and compared with Example 7, in Example 9, polyvinyl alcohol fibers were not added. As shown in Table 2, the long-term corrosion resistance of the valve bags prepared in Example 8 and Example 9 decreased significantly.

[0081] Compared with Example 7, in Example 10, nitrogen-doped carbon dots were not added to the reinforcing layer. For the valve bags made in Example 10, the initial decrease rate of tensile strength increased significantly, while the increase in the decrease rate of tensile strength after 30 d was not obvious, indicating that nitrogen-doped carbon dots can significantly reduce the initial corrosion caused by HDPE-Cu composite particles.

[0082] Compared with Example 1, in Comparative Example 1, the coupling-modified inorganic filler was not added respectively. Compared with Example 1, in Comparative Example 2, the inorganic filler was not treated by coupling. The tensile strength of the valve bags made in Comparative Example 1 and Comparative Example 2 decreased, and the adhesion between the kraft paper and the polymer film decreased.

[0083] In Comparative Example 3, the polymer film and the kraft paper were laminated to be composite. The adhesion between the kraft paper and the polymer film was smaller than that in Example 1, and the tensile strength of the packaging bag was lower than that in Example 1. Although the corrosion resistance was similar to that in Example 1, it was inferior to that in Example 5 and Example 11.

[0084] This specific embodiment is only an interpretation of the present application and does not limit the present application. After reading this specification, those skilled in the art can make modifications to this embodiment that do not contribute creatively as needed, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A surface anti-corrosion and breathable valve bag, comprising kraft paper and a polymer film located inside the kraft paper. Small holes are punched in both the kraft paper and the polymer film. It is characterized in that, An adhesive is contained between the kraft paper and the polymer film. The adhesive comprises raw materials in the following parts by weight: 1-4 parts of nitrile rubber, 10-20 parts of EVA, 35-65 parts of high-density polyethylene, 0.5-1 part of compatibilizer, 1-3 parts of coupling-modified inorganic filler, 10-20 parts of ethylene-octene copolymer, and 1-2 parts of antioxidant; The polymer film comprises raw materials in the following parts by weight: 8.5-9 parts of EVA, 1-1.5 parts of high-density polyethylene, and 0.5-0.8 part of HDPE-Cu composite particles with a copper shell and HDPE particles as the core; The coupling-modified inorganic filler is prepared by the following method: Mix the inorganic filler and a rare earth coupling agent with an addition amount of 1.5-2% of the mass of the inorganic filler, heat up to 75-80 °C, mix and stir for 8-10 min, and then cool to obtain the coupling-modified inorganic filler; The inorganic filler comprises nano-silica and nano-calcium carbonate with a mass ratio of 1:0.8-1; A reinforcing layer is coated on one side of the polymer film away from the adhesive. The reinforcing layer comprises raw materials in the following parts by weight: 10-20 parts of EVA, 5-10 parts of epoxy butyl rubber, 3-7 parts of polyethyleneimine-modified mesoporous titanium dioxide, 1-5 parts of nitrogen-doped carbon dots, and 1-3 parts of polyvinyl alcohol fibers.

2. The surface anti-corrosion and breathable valve bag according to claim 1, characterized in that, The nitrogen-doped carbon dots are prepared by the following method: Dissolve citric acid and polyethyleneimine in ultrapure water, then heat at 180-190 °C for 15-16 h, filter with a 0.45 μm filter membrane, dialyze, and then freeze-dry to obtain the nitrogen-doped carbon dots.

3. The surface anti-corrosion and air-permeable valve bag according to claim 1, wherein The polyethyleneimine-modified mesoporous titanium dioxide is prepared by the following method: Add mesoporous titanium dioxide to absolute ethanol, add polyethyleneimine, heat up to 120-140 °C, stir for 7-8 h, then centrifuge, wash, and dry to obtain the polyethyleneimine-modified mesoporous titanium dioxide.

4. The surface anti-corrosion and breathable valve bag according to claim 1, wherein The polyvinyl alcohol fibers are prepared by the following method: Dissolve polyvinyl alcohol in deionized water to prepare a shell solution with a concentration of 15-20 wt%, dissolve BTA in oleic acid to prepare a core solution with a concentration of 28-30 wt%; Electrospinning is carried out on the shell solution and the core solution with a coaxial needle nozzle to obtain the polyvinyl alcohol fibers.

5. The preparation method of the surface anti-corrosion and air-permeable valve bag according to any one of claims 1-4, characterized in that, It includes the following steps: Adhesive preparation: Mix nitrile rubber, EVA, high-density polyethylene, coupling-modified inorganic filler, ethylene-octene copolymer, and antioxidant, and extrude and pelletize to obtain the adhesive; Valve bag preparation: Melt the adhesive, brush it on the kraft paper, laminate the polymer film on the adhesive, and dry to obtain the substrate; Punching and bag making: Punch holes in the substrate, and after slitting, corner cutting, and heat sealing, obtain the valve bag.

6. The preparation method of the surface anti-corrosion and breathable valve bag according to claim 5, characterized in that, Before punching and bag making, the substrate is treated as follows: Mix 10-20 parts of EVA, 5-10 parts of epoxy butyl rubber, 3-7 parts of polyethyleneimine-modified mesoporous titanium dioxide, 1-5 parts of nitrogen-doped carbon dots, and 1-3 parts of polyvinyl alcohol fibers by weight, extrude and pelletize, melt and coat on the polymer film, and dry to obtain the reinforcing layer.

Images