Die-cutting rule passivation solution and use method thereof

Abstract

The invention provides a die-cutting rule passivation solution and a use method thereof. The passivation solution is prepared from 5%-10% of molybdate, 0.5%-2% of benzotriazole, 8%-15% of amino-epoxy bifunctional modified silicone oil, 3%-8% of a polyether dispersant and a solvent. Through a double corrosion inhibition mechanism of molybdate passivation and azole adsorption, a compact protective layer is formed on the surface of the die-cutting knife, and the adhesive force of a passive film is improved by combining the characteristics of modified silicone oil. The using method comprises the steps of ultrasonic dipping and gradient curing, and the problem that a 20-50 [mu] m thin film is broken due to tool rusting is effectively solved. According to special working conditions, 0.5-2 mu m polytetrafluoroethylene emulsion can be selectively overlaid to serve as an auxiliary lubricating layer, the service life of the die-cutting knife can be prolonged, the problem of film breakage of an existing die-cutting knife is greatly solved, and the die-cutting knife is suitable for precise packaging machining.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal surface processing, in particular to a passivation solution, especially a passivation solution suitable for die cutting knives, and a use method of the passivation solution. BACKGROUND

[0002] The packaging of products needs to be designed according to the shape contour of the products, and die cutting can make the packaging film accurately fit the products, provide good wrapping and protection, and ensure the stability of the products in the package. Die cutting usually uses a die cutting knife corresponding to the product to cut the packaging film, so that the packaging film can adapt to the packaging of products of various sizes.

[0003] However, during die cutting, the packaging film often has film breakage, film rupture or film discontinuity. Especially for 20-50um ultra-thin film, the tensile strength and tear resistance are relatively poor, and the film breakage is more serious. Improving the mechanical properties of the film body to adapt to the existing equipment not only produces a lot of trial costs, but also has a long evaluation time, low efficiency and uncertain effect. Considering that the die cutting knife itself will also be worn and rusted during long-term service, which will cause the blade angle to become larger and the sharpness to decrease, which is one of the main reasons for film breakage, and improvement of the rust prevention of the surface of the die cutting knife is also helpful to solve the above problems. However, for packaging film, especially food packaging film, the rust inhibitor is easy to remain on the surface of the knife, and when it contacts the food packaging film, it may precipitate carcinogens such as benzene series and polycyclic aromatic hydrocarbons, and electroplating / phosphating treatment may introduce hexavalent chromium or phosphate to contaminate the film. The existing passivation solution will cause the blade angle to increase, resulting in increased cutting resistance.

[0004] Therefore, it is necessary to improve the die cutting knife body to solve the technical problem of film breakage caused by rusting and large blade angle of the die cutting knife after long-term work. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art, and provides a die cutting knife passivation solution with good surface bonding effect, which reduces the rusting and dulling of the die cutting knife during use, and further reduces the film breakage problem of the die cutting knife.

[0006] To achieve the above-mentioned purpose, the technical scheme provided by the present application is as follows: A die cutting knife passivation solution, by weight percentage, comprising the following components: corrosion inhibitor: 5%-10% of molybdate compound, 0.5%-2% of azole organic corrosion inhibitor; film former: 8%-15% of organic silicon resin; dispersant: 3%-8% of polyether compound; pH adjuster: 1%-3% of organic acid; the dispersant is a block polyether with an HLB value of 12-14, and the structure is EO m -PO n -EO m，wherein m = 10-30, n = 20-70; the balance is solvent.

[0007] The molybdate compound can be selected from sodium molybdate, ammonium molybdate, etc., and for food safety considerations, phosphorus-containing molybdate or phosphorus molybdate compound or mixture should be avoided.

[0008] In the dispersant, EO is ethylene oxide, and PO is propylene oxide. In the synthesis of polyether, the two form block or random copolymers through ring-opening polymerization. The general structure is usually EO m -PO n -EO m or similar block structure, wherein m and n represent the number of repeating units.

[0009] Further, the solvent is selected from at least one of deionized water, ethanol, propylene glycol, ethyl acetate, and the conductivity is ≤5 μS / cm. The solvent is used to mix various components in the passivation solution, which can be selected from common low-toxic or non-toxic reagents, and organic solvents are selected to facilitate subsequent drying and solidification to remove the solvent, so that the coating is arranged on the die cutter surface and is closely combined with the die cutter surface.

[0010] The azole organic corrosion inhibitor includes benzotriazole and derivatives thereof. The benzotriazole and derivatives thereof are preferably selected from at least one of benzotriazole, methylbenzotriazole, 2-mercaptobenzothiazole, etc.

[0011] The silicone resin is an amino-epoxy bifunctional modified silicone oil, the viscosity is 200-500 mPa·s, and the mass ratio of the amino-epoxy bifunctional modified silicone oil to the polyether compound is 1:0.3-0.8.

[0012] Further, the main chain of the amino-epoxy bifunctional modified silicone oil includes polydimethylsiloxane, and the side chain branched from the main chain includes an aminopropyl group and an epoxypropyl group.

[0013] The application also provides a use method of the die cutter passivation solution having at least any one of the technical features. S1: cleaning the surface of the die cutter to remove residues and rust on the surface of the die cutter; S2: attaching the passivation solution to the die cutter with the surface cleaned; S3: drying the passivation solution and making it adhere to the surface of the die cutter.

[0014] The cleaning of the surface of the die cutter can specifically include but is not limited to the following: using sewage alcohol to remove oil stains, dust, and composite film residues, etc., and if there is slight rust on the surface, using fine sandpaper of 600 mesh or more to polish clean and wiping with a cloth.

[0015] Methods for attaching the passivation liquid to the die-cutting knife include but are not limited to placing the passivation liquid in a sprayer and spraying it onto the surface of the die-cutting knife, and applying the passivation liquid to the knife surface with a lint-free soft cloth, sponge, brush, etc., wherein the passivation liquid is mainly attached to the blade, seams and other easily oxidized parts. More preferably, the passivation liquid can be completely coated on the surface of the die-cutting knife to ensure that the passivation liquid, especially the passivation film formed by the passivation liquid, is intact.

[0016] Methods for drying the passivation solution include, but are not limited to, natural air drying and heat drying. After tool processing is completed, multiple tools should be separated by rust-proof paper or hung with hooks or other components, and moisture-proof treatment should be carried out. In particular, the relative humidity of the room where the tools are stored should be controlled below 50%RH.

[0017] Furthermore, in S2, the die-cutting knife is immersed in the passivation solution and ultrasonically treated at 35-50° C. for 10-30 min.

[0018] In S3, the die cutter is placed in an oven for drying at a gradient temperature increase, wherein the temperature is increased to 60-80° C. for drying in the first stage and is cured at 100-120° C. in the second stage.

[0019] In S3, before drying, polytetrafluoroethylene emulsion is coated on the surface of the die cutter with the passivation liquid attached thereto, and the polytetrafluoroethylene emulsion is solidified into a coating during drying, and surface finishing is performed after drying.

[0020] Furthermore, the PTFE emulsion coating has a thickness of 0.5-2 μm, and the surface finishing includes polishing to a roughness Ra of 0.5 μm or less. The use of PTFE emulsion is primarily to prevent substances such as molybdate from migrating, penetrating, or transferring to the composite film surface, ensuring the hygienic safety of food film and improving uneven coating thickness caused by gravity during the drying process. Specifically, after the die cutter is assembled, the PTFE layer provides a margin for grinding and polishing, preventing damage to the passivation layer during the polishing process.

[0021] The advantages and beneficial effects of the present invention are: 1. The passivation solution of the present invention forms a passivation film with molybdate and azole organic corrosion inhibitor to inhibit oxidative corrosion and block the penetration of corrosive media, thereby significantly improving the anti-corrosion performance of the die-cutting knife.

[0022] 2. Amino-epoxy bifunctional modified silicone oil has both flexibility and adhesion. The main chain polydimethylsiloxane provides hydrophobicity, and the side chain amino / epoxy groups enhance the chemical bonding with the metal surface, so that the passivation film remains intact under high-frequency working conditions of the tool.

[0023] 3. The passivation liquid of the present invention is dried in steps to achieve uniform leveling and high-temperature curing of the passivation liquid, promote the improvement of the cross-linking density of the resin, and avoid the stress cracking problem of the film layer caused by traditional single-temperature curing.

[0024] 4. After the polytetrafluoroethylene emulsion is compounded with the passivation film and cured, the surface roughness of the die-cutting knife can be further reduced, the service life of the die-cutting knife can be increased, and the possibility of the coating material adhering to the inside of the food packaging can be reduced, thereby improving food safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a flow chart of the method for using the passivation solution of the present invention; Figure 2 It is a die-cutting knife photo that the present invention part has used passivating liquid. DETAILED DESCRIPTION

[0026] The present invention provides a die cutter passivation liquid, the components of which include corrosion inhibitor, film former, dispersant, pH regulator and solvent. The corrosion inhibitor includes molybdate compound and benzotriazole. The molybdate compound is used as an anode corrosion inhibitor, and the MoO4 2- A passivation film of iron molybdate (FeMoO4) is formed on the metal surface, MoO4 2- Compared with chromate, it is non-toxic and environmentally friendly, and molybdate ions have self-repairing ability, which can quickly cover the active sites of the anode and inhibit Fe→Fe 2+ The passivation effect increases exponentially with increasing concentration. 5% is the critical film-forming concentration, 10% is the saturation concentration, and oversaturation will cause the passivation coating to become brittle. Corrosion inhibitors also include benzotriazole (BTA), which reacts with Fe via the lone pair electrons of the N atom. 3+ Coordinate to form [Fe(BTA)] on the metal surface n The adsorption layer blocks the penetration path of the corrosive medium. BTA molecules adsorb in a vertical orientation, forming a dense monolayer. BTA and molybdate form a dual mechanism of "physical shielding + chemical passivation." It is worth noting that the critical adsorption concentration of BTA is 0.5%. Excessive concentrations can lead to intermolecular π-π stacking and crystallization.

[0027] The film-forming agent uses a silicone oil system with polydimethylsiloxane (PDMS) as the backbone, providing a hydrophobic barrier with a contact angle greater than 110°. Pendant groups include aminopropyl and epoxypropyl groups. The aminopropyl groups form hydrogen bonds with the hydroxyl groups of the molybdate via -NH2, enhancing initial adhesion. The epoxypropyl groups undergo ring-opening and cross-linking during the curing phase, forming a three-dimensional network with the corrosion inhibitor. The viscosity of the film-forming agent is preferably between 200 and 500 mPa·s. A low viscosity facilitates the penetration of the passivation solution into the microscopic pores of the tool during ultrasonic treatment, while a higher viscosity improves the leveling of the film layer, effectively preventing orange peel defects after the passivation solution cures.

[0028] The ratio of the film forming agent to the polyether dispersant is preferably 1:0.3-0.8, and the polyether segment can be inserted into the gap of the silicone oil molecules to form an "anchoring-stretching" structure, with the hydrophilic end of the film forming agent adsorbed on the metal surface and the hydrophobic end compatible with the silicone oil.

[0029] The polyether compound used as the dispersant is preferably a block polyether with an HLB (hydrophilic-lipophilic balance) of 12-14, such as a polyoxypropylene polyoxyethylene copolymer solution, which encapsulates the molybdate particles by micellization to prevent the molybdate particles from settling. The dispersion of the molybdate can be achieved by ultrasonic dispersion to make the particle size of the molybdate composite D50 < 200 nm.

[0030] The pH regulator is preferably selected from acetic acid, citric acid or tartaric acid, etc. to dissociate hydrogen ions to stabilize the pH of the solution at 4.5-5.5, which promotes the formation of iron ion hydroxyl oxide (FeOOH) in this interval, and avoids excessive hydrolysis of molybdate to form MoO3 precipitate. The carboxyl group of the organic acid forms a hydrogen bond network with BTA, which can also effectively prolong the residence time of the corrosion inhibitor.

[0031] In the present application, the conductivity of the solvent system needs to be strictly controlled, especially for deionized water, reducing the impurities contained therein is beneficial to prevent impurities from remaining on the die cutter surface after solvent evaporation, thereby preventing pitting corrosion. As a preferred embodiment, a co-boiling drying solvent is prepared by compounding ethanol / propylene glycol at a volume ratio of 3:1, which has a boiling point of 78-83°C, which is beneficial to shorten the solvent evaporation time.

[0032] The present application further provides a use method of the above-mentioned passivation solution, which comprises an interface reaction stage, in which the die cutter is immersed in the passivation solution, and then ultrasonic cavitation is used to generate micro-jets to remove the relatively loose oxides on the surface of the die cutter, while BTA is preferentially adsorbed on the Fe grain boundary. And produce the effect of temporary adhesion. Then the die cutter is transferred to an oven for staged curing, in the first stage, the solvent volatilizes, the flexible movement of the silicone molecular chain occurs under heat and is driven by the surface tension, so that the siloxane backbone is oriented along the normal direction of the cutter surface; in the second stage, the ring-opening of the epoxy group occurs nucleophilic addition with the adjacent amino group, NH2-R + CH2-O-CH2→ NH-R-CH2-O-CH2-OH, thereby increasing the crosslinking density.

[0033] As a preferred embodiment, a 0.5-2 μm polytetrafluoroethylene (PTFE) composite layer can also be coated on the surface of the die cutter before curing, which can penetrate into the pore of the silicone network and block the migration process of organic matter during the curing process.

[0034] This gradient treatment process precisely controls molecular movement and reaction paths, making the passivation film have both high density and strong adhesion. Compared with traditional processes, the continuous working time of the tool is greatly improved and the film breakage rate is reduced, which is particularly suitable for precision die-cutting operations.

[0035] The following embodiments are further described in conjunction with the accompanying drawings and examples. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0036] It is worth noting that the die cutter blades of each embodiment were polished with 600-grit sandpaper before being coated with the passivation solution, and then scrubbed with ethanol to remove oil stains, and the die cutter surface was dried with a hair dryer. The polyethers used in each embodiment are as follows: Pluronic P123 (EO 20 -PO 70 -EO 20 )、Pluronic F127(EO 100 -PO 65 -EO 100 )、Pluronic L64(EO 13 -PO 30 -EO 13 )、Tergitol XD(PO 10 -EO 12 -PO 10 ).

[0037] Example 1 This embodiment provides a die-cutting knife passivation liquid, which comprises, by weight percentage, 6% sodium molybdate, 1.2% benzotriazole, 10% amino-epoxy bifunctional modified silicone oil (viscosity 350 mPa·s), 4% block polyether (Pluronic P123) dispersant, 2% citric acid, and the balance being a mixed solvent of deionized water and ethanol (a 3:1 volume ratio).

[0038] The use of the die cutting knife passivation liquid is as follows: S1, preparation of passivation solution: Sodium molybdate and benzotriazole were dissolved in a 40°C solvent, silicone oil and polyether dispersant were added, and the above substances were stirred at 3000 r / min for 30 min using a blender. Ultrasonic dispersion (40 kHz) was performed to make the molybdate particle size D50 ≤ 180 nm. Finally, citric acid was added to adjust the pH to 5.0.

[0039] S2, ultrasonic immersion: The die-cutting knife is immersed in a 45°C passivation solution and ultrasonically treated at 50kHz for 20 minutes. The cavitation effect causes the passivation solution to penetrate into the microscopic pits of the tool.

[0040] S3, segmented curing: Stage 1: Transfer the die cutter to a 65°C oven and dry for 1 hour until the passivation film thickness reaches 15±2μm; The second stage: the die-cutting knife is then air-cooled to room temperature and transferred to a 110°C oven for drying and curing for 2 hours.

[0041] Example 2 This embodiment provides a die-cutting knife passivation liquid, which comprises, by weight percentage, 10% ammonium molybdate, 0.5% methylbenzotriazole, 8% amino-epoxy bifunctional modified silicone oil (viscosity 500 mPa·s), 8% polyether (Pluronic F127) dispersant, 3% tartaric acid, and a solvent of propylene glycol and ethyl acetate (a mixed solvent in a volume ratio of 1:2).

[0042] The use of the die cutting knife passivation liquid is as follows: S1, preparation of passivation solution: pre-dissolve ammonium molybdate and methylbenzotriazole in a solvent at 60°C, then mix silicone oil and dispersant in a ratio of 1:0.8 and add to the solvent. Transfer the above substances to a magnetic stirrer and stir magnetically at 800 rpm for 2 hours. Add tartaric acid to adjust the pH to 4.8, and add the remaining dispersant.

[0043] S2, spraying treatment: Use high-pressure airless spraying equipment (pressure 0.3MPa) to evenly spray the passivation liquid onto the surface of the die cutter, with a wet film thickness of 25μm, and let it stand for 10 minutes to level.

[0044] S3, segmented curing: The first stage: the die cutter is transferred to an 80°C oven and dried for 40 minutes until the passivation film thickness reaches 20±1μm; The second stage: the die-cutting knife is then air-cooled to room temperature and transferred to a 120°C oven for drying and curing for 1.5 hours.

[0045] Example 3 This embodiment provides a die-cutting knife passivation liquid, which is composed, by weight percentage, of: 8% sodium molybdate + 2% ammonium molybdate, 2% benzotriazole, 12% amino-epoxy bifunctional modified silicone oil (viscosity 400 mPa·s), 5% polyether (Pluronic L64) dispersant, 1.5% acetic acid, and a solvent of deionized water and propylene glycol (volume ratio 1:1).

[0046] The use of the die cutting knife passivation liquid is as follows: S1, preparation of passivation solution: Sodium molybdate, ammonium molybdate and benzotriazole were dissolved in a 50°C solvent, silicone oil and polyether dispersant were added, and the above substances were stirred at 2000 r / min for 50 min using a blender. Ultrasonic dispersion (40 kHz) was performed to make the molybdate particle size D60 ≤ 200 nm. Finally, acetic acid was added to adjust the pH to 5.5.

[0047] S2, Ultrasonic Impregnation: Immerse the die cutter in a 40°C passivation solution and ultrasonically treat at 50kHz for 30 minutes. Immediately after impregnation, spray with 0.5μm PTFE emulsion (DuPont TE-3879) at a pressure of 0.2MPa, achieving a coverage of >95%.

[0048] S3, segmented curing: The first stage: the die cutter is transferred to a 60°C oven and dried for 1 hour, and the PTFE particles are simultaneously melted and embedded in the surface layer of the passivation film; The second stage: the die-cutting knife is then air-cooled to room temperature and then cured in an oven at 100°C for 2 hours to form an interpenetrating network structure with the silicone oil and PTFE.

[0049] S4, surface finishing: Use wool wheel + aluminum oxide polishing paste (particle size 0.5μm) to polish the PTFE layer to a roughness of Ra ≤ 0.3μm.

[0050] Example 4 This embodiment provides a die-cutting knife passivation liquid, which comprises, by weight percentage, 5% sodium molybdate, 0.5% 2-mercaptobenzothiazole, 15% amino-epoxy bifunctional modified silicone oil (viscosity 400 mPa·s), 3% polyether (Tergitol XD) dispersant, 1% acetic acid, and deionized water as the solvent, wherein the deionized water is distilled to a conductivity of 3 μS / cm.

[0051] The use of the die cutting knife passivation liquid is as follows: S1, preparation of passivation solution: Sodium molybdate and 2-mercaptobenzothiazole were dissolved in a 55°C solvent, silicone oil and polyether dispersant were added, and the above substances were stirred at 2000 r / min for 50 min using a blender. Ultrasonic dispersion (40 kHz) was performed to make the molybdate particle size D70 ≤ 250 nm. Finally, acetic acid was added to adjust the pH to 5.2.

[0052] S2, spraying treatment: Use high-pressure airless spray equipment (pressure 0.5MPa) to evenly spray the passivation liquid onto the surface of the die cutter, with a wet film thickness of 30μm. Let it stand and level for 10 minutes, then use a spin coater to spin at 3000r / min for 30s on the passivation film surface to form a 2μm PTFE layer.

[0053] S3, segmented curing: Stage 1: Transfer the die cutter to a 70°C oven and dry for 50 minutes until the passivation film thickness reaches 25±2μm; The second stage: the die-cutting knife is then air-cooled to room temperature and transferred to a 100°C oven for drying and curing for 3 hours.

[0054] S4, laser trimming the surface and edge of the passivation film to make the roughness of the PTFE layer Ra ≤ 0.5μm.

[0055] Comparative Example A die cutting knife that has not undergone a surface treatment process with a passivation liquid.

[0056] The die-cutting knives (initial blade angle 20°) obtained in the above examples and comparative examples were placed in a high-speed precision die-cutting machine (speed range 200-600 times / min) and continuously die-cut at 400 times / min on a 25 μm thick PET film (tensile strength ≥180 MPa, in compliance with GB / T 13542 standard) at a constant die-cutting pressure of 15 MPa at 25°C and 60% RH.

[0057] The test results are shown in the following table: As can be seen from the above table, see Figure 2 The die-cutting knife shown in the figure (left side without passivation film, right side with passivation film) shows that the passivation solution of the present invention can effectively increase the service life of the die-cutting knife for film die-cutting and reduce the film breakage rate of the die-cutting knife. In addition, the die-cutting knife containing the PTFE composite layer has a longer service life.

[0058] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A die-cutting knife passivation liquid, characterized in that: According to weight percentage, it includes the following components: Corrosion inhibitors: including molybdate compounds 5%-10%, azole organic corrosion inhibitors 0.5%-2%; Film-forming agent: silicone resin 8%-15%; Dispersant: polyether compound 3%-8%; pH regulator: organic acid 1%-3%; The dispersant is a block polyether with an HLB value of 12-14, and its structure is EO m -PO n -EO m , wherein m=10-30, n=20-70; the balance is solvent.

2. The die-cutting knife passivation liquid according to claim 1, characterized in that: The solvent is selected from at least one of deionized water, ethanol, propylene glycol, and ethyl acetate, and has a conductivity of ≤5 μS / cm.

3. The die-cutting knife passivation liquid according to claim 1, characterized in that: The azole organic corrosion inhibitor includes benzotriazole and its derivatives.

4. The die-cutting knife passivation liquid according to claim 1, characterized in that: The organosilicon resin is amino-epoxy bifunctional modified silicone oil with a viscosity of 200-500 mPa·s, and the mass ratio of the organosilicon resin to the polyether compound is 1:0.3-0.

8.

5. The die-cutting knife passivation liquid according to claim 4, characterized in that: The main chain of the amino-epoxy bifunctional modified silicone oil includes polydimethylsiloxane, and the side chains grafted from the main chain include aminopropyl and epoxypropyl.

6. The method for using the die-cutting knife passivation liquid according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: Clean the surface of the die-cutting knife to remove residues and rust on the surface of the die-cutting knife; S2: attaching the passivation liquid to the die-cutting knife whose surface has been cleaned; S3: Dry the passivation liquid and make it adhere to the surface of the die cutting knife.

7. The method for using the die-cutting knife passivation liquid according to claim 6, characterized in that: In S2, the die-cutting knife is immersed in the passivation solution and ultrasonically treated at 35-50° C. for 10-30 minutes.

8. The method for using the die-cutting knife passivation liquid according to claim 6, characterized in that: In S3, the die cutter is placed in an oven for drying at a gradient temperature increase, wherein the temperature is increased to 60-80° C. for drying in the first stage and is cured at 100-120° C. in the second stage.

9. The method for using the die-cutting knife passivation liquid according to any one of claims 6 to 8, characterized in that: In S3, before drying, polytetrafluoroethylene emulsion is coated on the surface of the die cutter with the passivation liquid attached thereto. The polytetrafluoroethylene emulsion solidifies into a coating during drying, and surface finishing is performed after drying. The polytetrafluoroethylene emulsion has a solid content of 50%-60% and a viscosity of 50-200 mPa·s.

10. The method for using the die-cutting knife passivation liquid according to claim 9, characterized in that: The thickness of the polytetrafluoroethylene emulsion coating is 0.5-2 μm, and the surface finishing includes polishing to make the roughness Ra of the polytetrafluoroethylene coating less than or equal to 0.5 μm.

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