CN115491103B - Water-based polyester modified epoxy back paint, preparation method thereof, environment-friendly household appliance color-coated plate with excellent foaming performance and production method thereof - Google Patents

Water-based polyester modified epoxy back paint, preparation method thereof, environment-friendly household appliance color-coated plate with excellent foaming performance and production method thereof Download PDF

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CN115491103B
CN115491103B CN202211188741.8A CN202211188741A CN115491103B CN 115491103 B CN115491103 B CN 115491103B CN 202211188741 A CN202211188741 A CN 202211188741A CN 115491103 B CN115491103 B CN 115491103B
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paint
water
units
environment
aqueous
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CN115491103A (en
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钱婷婷
施国兰
张宜
汤晓东
柴立涛
蔡明�
吴银义
孙霖
何峰
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Maanshan Iron and Steel Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D163/00—Coating compositions based on epoxy resins; Coating compositions based on derivatives of epoxy resins
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G59/00—Polycondensates containing more than one epoxy group per molecule; Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups
    • C08G59/18—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing
    • C08G59/40—Macromolecules obtained by polymerising compounds containing more than one epoxy group per molecule using curing agents or catalysts which react with the epoxy groups ; e.g. general methods of curing characterised by the curing agents used
    • C08G59/50—Amines
    • C08G59/504—Amines containing an atom other than nitrogen belonging to the amine group, carbon and hydrogen
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/08—Anti-corrosive paints
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2503/00—Polyurethanes

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  • Chemical & Material Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Paints Or Removers (AREA)

Abstract

The invention provides a waterborne polyester modified epoxy back paint, a preparation method thereof, an environment-friendly household appliance color coated plate with excellent foaming performance and a production method thereof. When the paint is used for the color-coated plates of household appliances, the relation between the furnace temperature T of the curing section and the thickness T m of the back paint film, the advancing speed V of the steel belt, the thickness T b of the base plate and the viscosity eta of the paint, T=6×t m+V/5+10×tb+100×(㏒10 eta) is realized, the environment-friendly color-coated plates of household appliances are realized, the comprehensive performance is superior, and especially, the foaming performance of the paint is superior to that of the existing solvent-based color-coated plates.

Description

Water-based polyester modified epoxy back paint, preparation method thereof, environment-friendly household appliance color-coated plate with excellent foaming performance and production method thereof
Technical Field
The invention belongs to the technical field of metal surface treatment and corrosion protection, and particularly relates to a waterborne polyester modified epoxy back paint, a preparation method thereof, an environment-friendly household appliance color-coated plate with excellent foaming performance and a production method thereof.
Background
The precoated coiled material coating is used as an important field of the coating industry, the production process of the precoated coiled material coating still takes the solvent type dominant due to the factors of performance and cost, but partial products also contain benzene, ether, malignant solvents and other harmful solvents due to the fact that the precoated coiled material coating contains a large amount of organic volatile matters, so that the precoated coiled material coating has serious environmental damage. The state releases a series of environmental protection regulations such as 'volatile organic compound pollution discharge charging test point method', 'harmful substance limit in industrial protective coating', and the like, so that enterprises in various working procedures are forced to accelerate the development progress of environmental-friendly products including water-based coatings. The water-based paint has the characteristics of environmental protection, no or low VOC emission, little peculiar smell, clean process, incombustibility, explosion resistance and the like, meets the requirements of green environmental protection production, and has very broad application prospect.
The aqueous epoxy paint is an environment-friendly paint in which water is used as a main solvent or a dispersion medium to waterborne an epoxy resin. The water-based paint has great difference between the physical properties of the paint and those of solvent-based paint because the medium is water, and the problems of viscosity, leveling property, compatibility of the production line and the like of the water-based paint are solved on the basis of the existing production line, so that the processes of coating, leveling, curing and the like become key technologies.
The color-coated plates have various emphasis because of different purposes, such as the color-coated plates of the washing machine are required to resist strong washing agents; besides the durability and the processing performance, the color-coated plate for the refrigerator back plate is required to be foamed to ensure the heat preservation performance of the refrigerator body and the like. Because the quality of the color-coated plate heat-insulating layer foam body for the refrigerator is directly related to the quality of the refrigerator product, the foaming is a key performance index in the refrigerator production.
The water-based system product has low maturity compared with the solvent-based product due to the restriction of performance, cost and the like, but the practical use environment of the household appliance color-coated plate is mild, and the requirement of corrosion resistance is lower than that of the building color-coated plate. However, the processing deformation degree of the household appliance color-coated plate is required to be higher than that of the building color-coated plate.
In recent years, technologies in various aspects are rapidly developed, and papers and patents related to water-based paint are also continuously seen. The patent CN 111925715A published in 11 months 13 in 2020 discloses a high corrosion resistance water-based paint for color coated plates and a preparation method thereof, and discloses a high corrosion resistance water-based paint for color coated plates and a preparation method thereof. The water-based paint is prepared by mixing the following raw materials in percentage by weight: 30 to 50 percent of graphene oxide modified waterborne epoxy resin, 5 to 20 percent of acrylic emulsion, 5 to 10 percent of nano silica sol, 20 to 40 percent of waterborne color paste, 0.1 to 1 percent of wetting agent, 0.1 to 1 percent of flatting agent and 5 to 20 percent of water. The water-based paint for the color-coated plate has the advantages of simple preparation process, smooth appearance, good glossiness, high film hardness, good adhesiveness and the like of the obtained coating, meanwhile, creatively uses graphene oxide modified water-based epoxy resin to improve the hardness, compactness and corrosion resistance of the coating, and meanwhile, nano silica sol is introduced into the paint, so that the micro defects of the coating can be repaired, and the comprehensive performance of the coating is further improved. The thickness of the coating in the patent is 20 microns, and the corrosion resistance is almost consistent with the specification of the solvent type color coated plate in the prior national standard GB/T13448.
An aqueous coating agent comprising at least one hydroxyl-containing compound (a), at least one compound (B) having isocyanate groups and having hydrolyzable silane groups, and at least one catalyst (C), characterized in that the compound (B) has less than 90 mol% of at least one structural unit-N (X-SiR "x(OR')3-x)n(X'-SiR"y(OR')3-y)m (I) wherein R ' =hydrogen, alkyl or cycloalkyl, X, X ' =linear and/or branched alkylene or cycloalkylene having 1 to 20 carbon atoms, R" =alkyl, cycloalkyl, aryl or aralkyl, n=0 to 2, m=0 to 2, m+n=0 to 2, and more than 10 mol% to 90 mol% of at least one structural unit-Z- (X-R) of formula (I) wherein R ' =hydrogen, alkyl or cycloalkyl, X, X ' =linear and/or branched alkylene or cycloalkylene having 1 to 20 carbon atoms, R "=alkyl, cycloalkyl, aryl or aralkyl, n=0 to 2, and X, y=0 to 2, and more than 10 mol% of at least one structural unit-Z- (X-SiR) of formula (I) wherein R ' =h-, -R-, wherein R-, -R-, and R-, are applied as a multi-step coating method, or the use of the coating process for automotive repair lacquering and/or for coating plastic substrates.
Low temperature curing of aqueous coatings, publication No. CN 113227279A, published at 6/8/2021, provides an aqueous basecoat composition that can be cured at low temperatures, preferably in the range of 80 ℃ to 140 ℃ and that additionally provides improved film properties such as hardness, grindability/polishability and adhesion. The invention focuses on the composition of the low-temperature cured water-based paint, and does not disclose the related process and effect on the color-coated plate.
The invention discloses a water-based nano coiled material coating and a preparation method thereof in publication number CN103232771A, which belong to a water-based nano coiled material coating and a preparation technology thereof, wherein the publication number CN103232771A is published in the 8 th 2013. Firstly, the non-toxic, odorless and incombustible characteristics of inorganic materials are used as basic powder materials of coiled material coatings, the nano technology and the nano materials are used for compounding, upgrading and modifying film forming substances such as aqueous acrylic emulsion, aqueous epoxy resin and water-soluble functional auxiliary agents in the inorganic materials, after the waterborne coiled material coatings are effectively completed, gaps of large-particle micrometer materials in a coating structure are filled by using various nano powder materials, so that the coating generates the enhancement effect of the coating function under the synergistic effect of the multi-effect combination of the nano-micrometer materials, the defect of performance reduction of the water-based coiled material coatings of the micrometer technology is effectively overcome, and the technical performance of the water-based coiled material coatings is remarkably improved. The invention improves the production efficiency, eliminates the fire hazard and industrial pollution of the traditional solvent coiled material coating, and realizes the purposes of safety, environmental protection, low consumption and high efficiency production.
The preparation of the water-based paint in the prior art is focused on, and the effect of the water-based pattern applied to the color-coated plates of the household appliances is not solved, and the foaming performance is good.
Disclosure of Invention
The invention aims to provide a waterborne polyester modified epoxy back paint and a preparation method thereof, wherein an epoxy resin with excellent processability and excellent polyester modified corrosion resistance is adopted as the resin, and a coating with excellent performance is obtained through formulation design.
The invention also aims to provide an environment-friendly household appliance color-coated plate with excellent foaming performance and a production method thereof, wherein the polyester modified epoxy resin with excellent corrosion resistance and excellent processability is adopted as the resin, and the environment-friendly household appliance color-coated plate is obtained by matching with the design of the technological parameters of a production line, so that the product has excellent comprehensive performance, and particularly, the foaming performance of the product is superior to that of the traditional solvent-based color-coated plate.
The specific technical scheme of the invention is as follows:
the aqueous polyester modified epoxy back paint comprises the following raw materials in percentage by mass:
35-50 parts of water-based epoxy resin;
8-12 parts of polyester resin;
pigment and filler: 15-30 parts of a lubricant;
Aqueous curing agent: 5-10 parts;
Acid catalyst: 1-2 parts;
Polytetrafluoroethylene wax auxiliary agent: 0.2-0.5 part;
Organically treating the silica matting agent: 0.3-0.8 part;
Aqueous leveling agent: 0.4-0.8 part;
aqueous wetting agent: 0.4-1.0 parts;
And (3) a plasticizer: 0.1-0.4 part;
Solvent: 22-35 parts.
The mass ratio of the aqueous epoxy resin to the polyester resin is as follows: 4-6:1;
The aqueous epoxy resin is selected from Jiangsu Sanmu group E-44 (6101);
The polyester resin is selected from the chemical SK9080D of the general family;
The design concept of the selection of the resin is as follows: the epoxy resin molecule E-44 (6101) and the ether group and the hydroxyl group contained in the epoxy resin molecule E-44 are both strong polar groups, the-OH of the epoxy resin is dispersed at a proper distance, the-OH in bisphenol core molecules is difficult to attract each other, and the effective adhering polarity is more. These groups can provide a strong bond between E-44 (6101) and the substrate, particularly the metal surface; in addition, the molecular structure is compact, the cohesive force is strong, the internal stress is small, and the cracking is difficult. The modified E-44 (6101) can effectively regulate the internal structure of the coating, improve the internal stress of the coating, reduce the peeling between the coating and the metal substrate and improve the adhesive force.
The pigment and filler is selected from rutile titanium dioxide R996 of Langfang Boma chemical Co;
the aqueous curing agent is selected from CYDHD-220 of Shanghai Yue Yi chemical industry Co., ltd;
the design idea of the curing agent is as follows: in order to endow the coating film with better weather resistance, the invention selects silane resin CYDHD-220 containing amino functional groups, and the amino groups are connected with the silane resin through Si-C bonds, so that the structure can play a role of a catalyst for condensation reaction of silanol groups and alkoxy groups in the resin, and simultaneously, the amino groups in the structure can react with epoxy resin to form a space three-dimensional network structure.
The acid catalyst is selected from: U.S. Chemie N-2500;
The polytetrafluoroethylene wax auxiliary agent is selected from trefoil wax powder polytetrafluoroethylene wax SST-4MG;
The organically treated silica matting agent is selected from the group consisting of SYLOID C807 of Graves China company Limited;
the aqueous leveling agent is selected from the group consisting of Pick chemical BYK333;
The aqueous wetting agent is selected from german di-high TEGO-270;
compared with other organic coatings, the water-based coating has poorer corrosion resistance, increases the difficulty of construction control of the water-based coating due to larger surface energy of water and uneven volatilization of aqueous solution in the baking process, and has poor surface performance of a coating film, easy occurrence of phenomena such as orange peel, pinholes, wrinkling and the like, unsmooth and poor leveling property. To overcome the defects as much as possible, a certain amount of water-based surface wetting agent and leveling agent are added into the studied paint, so that good effect is achieved.
The plasticizer is selected from dibutyl phthalate;
the plasticizer is generally a small molecular compound, has good compatibility with the polymer, can be filled between chain segments of adjacent macromolecules, increases the distance, weakens the interaction force of the adjacent macromolecules, and eliminates the internal stress, thereby reducing the tendency of brittle fracture and effectively increasing the adhesive force to a certain extent.
The solvent is selected from: one or more of N, N-dimethylformamide, ethylene glycol butyl ether, isopropanol and deionized water;
The preferable solvents are N, N-dimethylformamide, isopropanol and deionized water, and the mass ratio is as follows: 3:3:16-30;
The invention provides a preparation method of a waterborne polyester modified epoxy back paint, which comprises the following steps:
1): neutralizing the formula amount of water-based epoxy resin with N, N-dimethylformamide, premixing the water-based epoxy resin with pigment and filler and deionized water for 25-35min, grinding the water-based epoxy resin with a sand mill to be less than 10 mu m to obtain slurry, and controlling the grinding temperature to be 20-50 ℃;
2): adding polyester resin and isopropanol in the formula amount into the slurry, uniformly mixing, adding an acid catalyst, a water-based curing agent, a polytetrafluoroethylene wax auxiliary agent, a water-based leveling agent, a water-based wetting agent and an organic treatment silicon dioxide matting agent, dispersing and stirring at a high speed of 3000rpm for 1.8-2.5h, uniformly mixing, regulating the viscosity to 100-130s (No. 4 Ford cup, 25 ℃), and finally filtering to obtain the modified polyester resin.
By the preparation method, the waterborne polyester resin is linked on the C chain of the epoxy resin, and the waterborne polyester modified epoxy resin is realized, so that the foaming performance is excellent, and the rest performances are not influenced.
An environment-friendly household appliance color-coated plate with excellent foaming performance comprises a passivation substrate and a paint film;
The passivation substrate: a galvanized steel plate or a galvanized aluminum-magnesium steel plate is adopted, and a plating layer with different thickness or equal thickness is formed on the two sides;
The total weight of the double-sided plating layer of the galvanized steel sheet is controlled as follows: the pure zinc plating layer is not lower than 80g/m 2;
The total weight of the double-sided plating layer of the galvanized aluminum magnesium steel plate is controlled as follows: the zinc-aluminum-magnesium coating is not lower than 60g/m 2.
The passivation substrate is a chromium passivation substrate, and the passivation film weight is not lower than 10mg/cm 2.
The yield strength of the passivated substrate is less than or equal to 200MPa, and the elongation is more than or equal to 40%.
The paint film is formed on the passivation substrate after the waterborne polyester modified epoxy back paint is used as a coating.
The preparation method of the environment-friendly household appliance color coated plate with excellent foaming performance provided by the invention comprises the following process flows: passivating a substrate, coating aqueous polyester modified epoxy back paint, drying, solidifying, cooling, checking and coiling.
The drying and curing steps are specifically as follows: the curing section furnace temperature T is related to the back paint film thickness T m, the steel strip advancing speed V, the substrate thickness T b and the coating viscosity η, t=6×t m+V/5+10×tb+100×(㏒10 η). T is in units of °C, T m is in units of μm, V is in units of m/min, T b is in units of mm, η is in units of s, at 25 ℃, ford 4# cup. In the calculation of the above formula, the numerical value of the unit is substituted into the formula. Preferred t m：5± 2μm,V：50-80m/min,tb: 0.3-0.6mm, eta, 80+/-20 s. The specific relationship between the curing section furnace temperature T and the back paint film thickness T m, the steel belt advancing speed V, the substrate thickness T b and the paint viscosity eta is determined according to the coating and curing characteristics of the environment-friendly composite back paint. According to the formula, the prepared color-coated plate of the water-based polyester modified epoxy back paint after curing has excellent performances, especially excellent foaming performance.
In the invention, the production line speed, namely the strip steel advancing speed, is inversely proportional to the curing time, the curing time of the back paint is controlled by controlling the production line speed in production, and the curing time is 36s-120s by the formula, wherein the length of the production line is 30-100 m. The quality of the back paint is directly related to the curing time and temperature, especially the foaming adhesive property. The foaming adhesion of the paint film is mainly related to the quantity of active hydroxyl groups (or polar groups) in the paint film and the crosslinking density of the paint film, and in general, the higher the crosslinking density of the paint film is, the more difficult the foaming adhesion is, such as the harder the simple polyester back paint is to foam. On the other hand, the more reactive hydroxyl groups or polar groups remain in the paint film, the easier the foaming. The solvent is fast in volatilization speed, poor in leveling property and easy to generate pinhole defects in the coating; the volatilization speed is low, the residual quantity of the solvent in the coating is increased, and the performance of the coating is affected. Only by properly controlling the volatilization rate of the solvent, the excellent performance of the coating can be ensured. If the curing temperature or time is insufficient, the crosslinking density of the paint film is small, and the corrosion resistance is reduced; if the curing is excessive, namely the curing temperature and the curing time are too long, the crosslinking of the paint film is too sufficient, the reactive groups are too few, the reaction degree with the subsequent foaming material is low, the foaming adhesive property is poor, the curing temperature is increased within a certain curing temperature range, and the curing time can be reduced. The fluctuation of the viscosity of the paint can influence the thickness of the subsequent upper film, the thickness of the back paint coating is increased, the internal temperature difference of the primer is increased, and the curing temperature is required to be properly increased or the curing time is prolonged to ensure the consistency of the back paint performance of different thicknesses in order to completely cure the internal primer.
The solvent in the solvent type epoxy paint is easy to volatilize, the solvent volatilizes from the system firstly in the film forming process, then the amine curing agent reacts with the epoxy resin to be cured into a film, and the condensation film forming process does not exist. In the aqueous system, the evaporation of water is slow, so that the film forming of the aqueous epoxy resin emulsion is carried out in the process of evaporating water, the curing agent contacts the surfaces of the epoxy resin particles to carry out curing and crosslinking reaction, and then the molecules of the curing agent diffuse into the epoxy resin particles to carry out further crosslinking and curing reaction. Under capillary pressure, the epoxy resin particles are brought close to each other with evaporation of water, and are coagulated and solidified into a uniform film.
The inventor finds that the setting of the process window parameters of the water-based paint production line is the core of influencing the surface quality, the service performance and the like of the water-based color-coated plate. According to the characteristics and the curing effect of the back paint, the formula is designed, and the color-coated plate with excellent performance is produced. The water-based coiled material coating polyester back paint prepared by the invention has the properties of high hardness, adhesive force, good flexibility and the like. Flexibility aspect: test results show that the prepared water-based coiled material polyester back paint can reach 3-5T without peeling on a T bend, reaches the standard of solvent-based polyester paint, and has flexibility performance which is higher than that of the traditional epoxy back paint by 5-6T; in terms of hardness, the hardness of the prepared water-based coiled material polyester back paint reaches the hardness of Mitsubishi pencil 4H without scratches; adhesion aspect: test results show that the coating falling degree of the prepared water-based coiled material polyester back paint in a hundred-grid test is less than 5%, and the coating falling area of the water-based coiled material polyester back paint is 5% -8% better than that of a solvent-based polyester paint; the prepared water-based back paint finished product has the foaming adhesion reaching 95 percent, and has the characteristics of environmental protection and green color-coated plates of traditional solvent type household appliances. The performance of the aqueous home appliance back paint prepared by the invention reaches the level of the solvent-based products of the same type, and even certain indexes have advantages such as foaming performance, and the aqueous home appliance back paint can completely replace the solvent-based products.
Drawings
FIG. 1 is a MEK resistant of example 2;
FIG. 2 is a MEK resistant of comparative example 1;
FIG. 3 shows the foaming adhesive ratio of example 1;
FIG. 4 is the foam adhesion rate of comparative example 1;
FIG. 5 is the results of a 240 hour neutral salt spray experiment of example 1;
FIG. 6 is the results of a 240 hour neutral salt spray experiment of example 2;
FIG. 7 is the results of a 240 hour neutral salt spray test of example 3.
Detailed Description
This patent is specifically illustrated by examples and comparative examples according to the invention by changing the composition of the environment-friendly composite back paint and the double control requirements of the working procedure and process.
Example 1-example 3
The aqueous polyester modified epoxy back paint comprises the following raw materials in percentage by mass: the types of raw materials are shown in Table 1, and the specific amounts are shown in Table 2.
Comparative example 1-comparative example 2
The aqueous polyester modified epoxy back paint comprises the following raw materials in percentage by mass: the types of raw materials are shown in Table 1, and the specific amounts are shown in Table 2.
TABLE 1 raw material information
Table 2 raw material amounts (parts by mass) of the environmental-friendly composite back paint of each example and comparative example
Raw materials Example 1 Example 2 Example 3 Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4
OF-100 8 8 12 8 8 12 8
E-44(6101) 40 48 50 / 64 50 48
E-51(618) / / / 40 / / /
Aqueous epoxy resin: polyester resin 5 6 4.166 5 8 4.166 6
R996 16 22 30 16 22 30 22
CYDHD-220 6 5 9 6 5 9 5
N-2500 1.3 1.6 1.9 1.3 1.6 1.9 1.6
Polytetrafluoroethylene wax SST-4 0.2 0.3 0.5 0.2 0.3 0.5 0.3
BYK333 0.8 0.4 0.5 0.8 0.4 0.5 0.4
SYLOID C807 0.6 0.4 0.8 0.6 0.4 0.8 0.4
TEGO-270 0.6 0.9 0.5 0.6 0.9 0.5 0.9
Dibutyl phthalate 0.3 0.4 0.1 0.3 0.4 0.1 0.4
Isopropyl alcohol 3 3 3 3 3 3 3
Deionized water 23 16 29 23 16 29 16
N, N-dimethylformamide 3 3 3 3 3 3 3
Step 1: after the water-based epoxy resin is neutralized by N, N-dimethylformamide, the water-based epoxy resin is premixed with pigment and filler and deionized water for 25-35min, and then is ground to be less than 10 mu m by a sand mill to obtain slurry, wherein the grinding temperature is controlled to be 20-50 ℃.
Step 2: adding polyester resin and isopropanol into the slurry, uniformly mixing, adding an acid catalyst, a water-based curing agent, a polytetrafluoroethylene wax auxiliary agent, a water-based leveling agent, a water-based wetting agent and an organically treated silica matting agent, dispersing and stirring for 2 hours at a high speed of 3000rpm, and adjusting the viscosity to 100-130s (No. 4 Ford cup, 25 ℃) after uniform mixing. And finally filtering.
The coating prepared by the invention is a waterborne polyester modified epoxy back paint.
The preparation method of the environment-friendly composite back paint household appliance color-coated plate with excellent foaming performance, which is described in the above examples and comparative examples, comprises the following process flows:
Passivating a substrate, coating a back paint, drying, solidifying, cooling, checking and coiling.
The passivation substrate: a galvanized steel plate or a galvanized aluminum-magnesium steel plate is adopted, and a plating layer with different thickness or equal thickness is formed on the two sides;
TABLE 3 substrate information
Substrate type Number plate Composition of the components Weight of double-sided coating
Galvanized sheet TDX53D WZn＞99％ ≥80g/m2
Galvanized aluminum magnesium plate TDX53D+ZM WMg＜3％;WAl＜3％ ≥60g/m2
The passivation substrate is a chromium passivation substrate, and the passivation film weight is not lower than 10mg/cm 2.
The yield strength of the substrate is less than or equal to 200MPa, and the elongation is more than or equal to 40%.
The drying and curing steps are specifically as follows: the curing section furnace temperature T is related to the back paint film thickness T m, the steel strip advancing speed V, the substrate thickness T b and the coating viscosity η, t=6×t m+V/5+10×tb+100×(㏒10 η). T is in units of °C, T m is in units of μm, V is in units of m/min, T b is in units of mm, η is in units of s, at 25 ℃, ford 4# cup. In the calculation of the above formula, the numerical value of the unit is substituted into the formula. Preferred t m： 5±2μm,V：50-80m/min,tb: 0.3-0.6mm, eta, 80+/-20 s. The specific relationship between the curing section furnace temperature T and the back paint film thickness T m, the steel belt advancing speed V, the substrate thickness T b and the paint viscosity eta is determined according to the coating and curing characteristics of the environment-friendly composite back paint. The water in the coating volatilizes, and the coating performance is greatly influenced. The volatilization speed is high, the leveling property is poor, and pinhole defects are easy to occur in the coating; the volatilization speed is low, the residual quantity of the solvent in the coating is increased, and the performance of the coating is affected. Only by properly controlling the volatilization rate of the solvent, the excellent performance of the coating can be ensured.
The process parameters of the environment-friendly composite back paint household appliance color-coated plate with excellent foaming performance produced by the specific examples and the comparative examples are shown in table 4.
Table 4 production parameters of examples and comparative examples
The properties of the products produced according to the above methods for each example and comparative example are shown in Table 5, test methods: GB/T13448-2019; stacking 6 templates, and placing the templates from bottom to top in the sequence of (1) facing upwards; (2) 2 blocks face down; 2 blocks are contacted back to back, enamel codes with the diameter of 70mm and the mass of 500g are applied on a template, the template is separated after the pressure is removed after the enamel codes are placed in a (50-soil) 2 ℃ oven for 4 hours, and the difficulty and the damage degree of the surface of a paint film during separation are checked.
Table 5 test results for example aqueous back coats
The data in the horizontal direction shown in each table are data which do not satisfy the requirements of the present invention.
As can be seen from the above table, the ratio of the polyester resin to the epoxy resin is required to be within a certain range, namely, the aqueous epoxy resin: polyester resin=4-6: 1, the polyester resin has the defects of incomplete curing, easy adhesion and poor solvent MEK resistance. If the proportion of the polyester resin is too high, the crosslinking degree density is too high, the flexibility is insufficient, the pencil hardness is increased, and the T-bend performance is reduced.
Comparative example 1, although the composition and curing process meet the requirements of the present invention, the E-51 (618) epoxy resin is adopted, the foaming rate is low, the adhesive force is poor, and the flexibility does not meet the requirements; the epoxy resin of comparative example 2 is used in a large amount, and the polyester resin is too low in proportion, so that the polyester resin is not completely cured and is easy to adhere, and the solvent MEK resistance is also poor, and the foaming rate is extremely low. Comparative example 3 the mixing time during the preparation of the coating was too long after neutralization of the aqueous epoxy resin with N, N-dimethylformamide, and mixing with the pigment and the deionized water, which did not meet the requirements of the present invention, decreased foaming ratio, poor adhesion, and low hardness. Comparative example 4 even though the coating was prepared to produce according to the present invention, the curing time was not controlled according to the formula of the present invention, and the curing temperature was low, resulting in poor solvent-resistant MEK properties of the product, low foaming rate, and low flexibility.
In conclusion, the paint components and the production process are controlled according to the design of the invention, and the obtained environment-friendly household appliance color-coated plate has excellent foaming performance; example 2 shows that the color coated plate of the household appliance has strong scrubbing resistance when the plate surface is free from bottom exposure when the MEK is resistant for 120 times, and the plate surface is free from bottom exposure when the MEK is resistant for 100 times in comparative example 1. The neutral salt spray corrosion of the product provided by the embodiment of the invention does not have red rust for 240 hours, (the positive neutral salt spray corrosion of the solvent type household appliance color coated plate is 240 hours), and the corrosion resistance is excellent.
The foregoing description is only illustrative of the present invention, and it is to be understood that the specific implementation of the present invention is not limited by the foregoing manner, and it is within the scope of the present invention to apply the technical concept and technical solution of the present invention to other situations without any substantial improvement or any improvement.

Claims (5)

1. The environment-friendly household electrical appliance color-coated plate with excellent foaming performance is characterized in that the environment-friendly household electrical appliance color-coated plate with excellent foaming performance comprises a passivation substrate and a paint film; the paint film is a film formed on a passivation substrate after the waterborne polyester modified epoxy back paint is cured;
The preparation method of the environment-friendly household appliance color-coated plate with excellent foaming performance comprises the following process flows: passivating a substrate, carrying out waterborne polyester modified epoxy back paint, drying, solidifying, cooling, checking and coiling;
The drying and curing steps are specifically as follows: the relation between the curing section furnace temperature T and the back paint film thickness T m, the steel belt advancing speed V, the substrate thickness T b and the paint viscosity eta, wherein T=6×t m+V/5+10×tb+ 100×(㏒10 eta); t is in units of temperature, T m is in units of μm, V is in units of m/min, T b is in units of mm, eta is in units of s, at 25 ℃, ford 4# cup;
the aqueous polyester modified epoxy back paint comprises the following raw materials in percentage by mass:
35-50 parts of water-based epoxy resin;
8-12 parts of polyester resin;
pigment and filler: 15-30 parts of a lubricant;
Aqueous curing agent: 5-10 parts;
Acid catalyst: 1-2 parts;
Polytetrafluoroethylene wax auxiliary agent: 0.2-0.5 part;
Organically treating the silica matting agent: 0.3-0.8 part;
Aqueous leveling agent: 0.4-0.8 part;
aqueous wetting agent: 0.4-1.0 parts;
And (3) a plasticizer: 0.1-0.4 part;
Solvent: 22-35 parts of a lubricant;
The mass ratio of the aqueous epoxy resin to the polyester resin is as follows: 4-6:1;
the aqueous epoxy resin is selected from Jiangsu Sanmu group E-44;
The preparation method of the aqueous polyester modified epoxy back paint comprises the following steps:
Step 1: neutralizing the formula amount of water-based epoxy resin with N, N-dimethylformamide, premixing with pigment and filler and deionized water, grinding to below 10 μm by a sand mill to obtain slurry, and controlling the grinding temperature to be 20-50 ℃;
Step 2: adding polyester resin and isopropanol in the formula amount into the slurry, uniformly mixing, adding an acid catalyst, a water-based curing agent, a polytetrafluoroethylene wax auxiliary agent, a water-based leveling agent, a water-based wetting agent and an organic treatment silica matting agent, dispersing and stirring at a high speed, uniformly mixing, adjusting the viscosity to 100-130s, a No. 4 Ford cup, and filtering at 25 ℃ to obtain the modified polyester resin;
In the step 1), premixing is carried out for 25-35min.
2. The environmentally friendly household electrical appliance color coated sheet with excellent foaming property according to claim 1, wherein the passivation substrate is characterized in that: the galvanized steel sheet or the galvanized aluminum-magnesium steel sheet is adopted, and the plating layers with different or equal thickness on the two sides are adopted.
3. The environmentally-friendly household appliance color coated sheet with excellent foaming property according to claim 1 or 2, wherein the total weight of the double-sided coating layer of the galvanized steel sheet is controlled as follows: the pure zinc plating layer is not lower than 80g/m 2; the total weight of the double-sided plating layer of the galvanized aluminum magnesium steel plate is controlled as follows: the zinc-aluminum-magnesium coating is not lower than 60g/m 2.
4. A method for preparing the environment-friendly household appliance color coated sheet with excellent foaming performance as claimed in any one of claims 1 to 3, which is characterized by comprising the following process flows: passivating a substrate, carrying out waterborne polyester modified epoxy back paint, drying, solidifying, cooling, checking and coiling.
5. The method for preparing the environment-friendly household appliance color coated sheet with excellent foaming performance according to claim 4, which is characterized in that the drying and curing steps are as follows: the relation between the curing section furnace temperature T and the back paint film thickness T m, the steel belt advancing speed V, the substrate thickness T b and the paint viscosity eta, wherein T=6×t m+V/5+10×tb+ 100×(㏒10 eta); t is in units of °C, T m is in units of μm, V is in units of m/min, T b is in units of mm, η is in units of s, at 25 ℃, ford 4# cup.
CN202211188741.8A 2022-09-27 2022-09-27 Water-based polyester modified epoxy back paint, preparation method thereof, environment-friendly household appliance color-coated plate with excellent foaming performance and production method thereof Active CN115491103B (en)

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