CN111205443A

CN111205443A - Polyester resin for two-piece can printing ink, two-piece can printing ink and preparation method of two-piece can printing ink

Info

Publication number: CN111205443A
Application number: CN202010133562.9A
Authority: CN
Inventors: 杜坤扬; 张龙斌
Original assignee: Shanghai Super Color Ink Co ltd
Current assignee: Shanghai Super Color Ink Co ltd
Priority date: 2020-03-02
Filing date: 2020-03-02
Publication date: 2020-05-29

Abstract

The invention provides a polyester resin for ink of a two-piece can, which is prepared from the following raw materials in parts by weight: 25-32 parts of dicarboxylic acid, 12-16 parts of saturated fatty acid, 6-12 parts of dihydric alcohol, 24-32 parts of polyhydric alcohol, 8-13 parts of anhydride, 1-3 parts of lactone, 0.02-0.03 part of catalyst and 0.2-0.5 part of antioxidant. The invention also provides a preparation method of the polyester resin for the two-piece can ink. The invention also provides two-piece can ink which is prepared from the polyester resin, the amino resin, the organic solvent, the catalyst, the organic pigment powder, the filler and the auxiliary agent. Meanwhile, the invention also discloses a method for preparing the two-piece can printing ink by using the polyester resin. The two-piece can ink prepared by the method has the advantages of good viscoelastic thixotropy, pigment wettability, scratch resistance, ink flying resistance and the like, particularly the pencil hardness can reach 7H, and the ink flying test reaches 5 grades.

Description

Polyester resin for two-piece can printing ink, two-piece can printing ink and preparation method of two-piece can printing ink

Technical Field

The invention belongs to the field of chemical industry, and relates to ink, in particular to polyester resin for two-piece can ink, the two-piece can ink and a preparation method thereof.

Background

With the technological progress and the improvement of the living standard of people, people have more and more demands on canned food and beverage, and the requirements are also higher and higher. In recent years, glass bottled foods and beverages have been eliminated from the market due to safety reasons, and two-piece canned foods and beverages using aluminum as a base material have been favored in the market. The two-piece can is made of stretched aluminum and is formed in one step through the processes of uncoiling, die cutting, primary stretching, secondary stretching, cleaning, drying, printing, external coating, internal spraying, drying and the like. The process has the advantages of high production efficiency, low energy consumption, low production loss and VOC discharge far lower than the limit of national standards. The sample tank made by the process has exquisite printing pattern and can be recycled.

Two-piece canned foods and beverages require special two-piece can inks. At present, in the field of two-piece can ink, the technology is more advanced by foreign companies such as INX international ink company. In recent years, with the demand of domestic markets, some domestic ink companies are also developing two-piece tank inks slowly. Compared with the two-piece jar printing ink technology abroad, the two-piece jar printing ink in China has the problems of serious ink flying, poorer transferability, poor visco-elastic thixotropy, poor scratch resistance and the like. Therefore, the domestic two-piece ink technology has to make breakthroughs in these aspects to surpass the foreign technology.

The performance of the two-piece tank ink mainly depends on the performance of the polyester resin, so that in order to solve the problems of ink misting, transferability, viscoelasticity and scratch resistance, a polyester resin for the two-piece tank ink with high scratch resistance, good ink misting resistance and good transfer viscoelasticity is urgently needed to be synthesized, a short plate with high performance is made up, the application field of the polyester resin is further expanded, and the domestic market demand is met.

Disclosure of Invention

The invention provides polyester resin for two-piece can ink, two-piece can ink and a preparation method thereof, aiming at the defects of the prior art, and the polyester resin for two-piece can ink, the two-piece can ink and the preparation method thereof are used for solving the technical problems of serious ink flying, poor transferability, poor visco-elastic thixotropy and poor scratch resistance of the two-piece can ink in the prior art.

The invention provides a polyester resin for two-piece can printing ink, which is prepared from the following raw materials in parts by weight:

further, the dicarboxylic acid is any one or a mixture of more than two of terephthalic acid, isophthalic acid, phthalic acid, adipic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, malic acid, dimer acid, tetrahydrophthalic acid, hexahydroisophthalic acid, 1, 2-cyclohexanedicarboxylic acid and 1, 4-cyclohexanedicarboxylic acid in any proportion.

Further, the saturated fatty acid is any one or a mixture of more than two of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid and arachidic acid in any proportion.

Further, the dihydric alcohol is any one or a mixture of two or more of ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 4-butanediol, 2-methyl-1, 3-propanediol, neopentyl glycol, 1, 6-hexanediol, 1, 7-heptanediol, 1, 9-nonanediol, hydroxypivalyl hydroxypivalate, 2-ethyl-2-butyl-1, 3-propanediol, 2, 4-trimethyl-1, 3-pentanediol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetrahydrofuran glycol, 1, 4-cyclohexanediol, 1, 3-cyclohexanediol, 1, 2-cyclohexanediol, and hydrogenated bisphenol a diol at any ratio.

Further, the polyol is any one or a mixture of more than two of glycerol, pentaerythritol, trimethylolpropane, trimethylolethane and polyether polyol in any proportion.

Further, the acid anhydride is any one or a mixture of more than two of trimellitic anhydride, phthalic anhydride, tetrahydrophthalic anhydride and hexahydrophthalic anhydride in any proportion.

Further, the lactone is any one of caprolactone and butyrolactone or a mixture of the two.

Further, the catalyst is one or a mixture of more than two of monobutyl tin oxide, dibutyl tin oxide chloride, dibutyl tin dilaurate, dibutyl tin oxalate and monobutyl tin trichloride in any proportion.

Further, the antioxidant is any one or a mixture of more than two of dibutyl hydroxy toluene, pentaerythritol tetra (di-tert-butyl hydroxy hydrocinnamate), β (octadecyl 3, 5-di-tert-butyl-4-hydroxyphenyl) propionate, tris (nonylphenyl) phosphite and tris (2, 4-di-tert-butylphenyl) phosphite in any proportion.

The invention also provides a preparation method of the polyester resin for the two-piece can ink, which comprises the following steps:

1) weighing the raw materials in parts by weight;

2) introducing nitrogen, adding dicarboxylic acid, saturated fatty acid, dihydric alcohol, polyalcohol, anhydride, lactone, catalyst and antioxidant, heating to 130 ℃, and keeping the temperature for 1H;

3) heating to 148-152 ℃, and keeping the temperature for 1H;

4) heating to 158-162 ℃, and dividing water by a water separator and preserving heat for 2H;

5) heating to 168-172 ℃, and keeping the temperature for 0.5H;

6) heating to 178-182 ℃, and keeping the temperature for 2H;

7) heating to 188-192 ℃, and keeping the temperature for 0.5H;

8) heating to 198-200 ℃, and keeping the temperature for 1H;

9) heating to 202-205 ℃, and keeping the temperature for 1H;

10) and stopping nitrogen after heat preservation is finished. Adding a vacuum pump to firstly vacuumize the device to 0.05MPa of vacuum degree and keep the vacuum degree for 15-25 minutes, and then gradually increasing the vacuum degree to 0.08MPa and keeping the vacuum degree for 15-25 minutes;

11) and (3) testing the acid value of the resin, cooling to 70-80 ℃ when the acid value is less than 35mgKOH/g, adding diluent polyethylene glycol 200 accounting for 20% of the total mass of the materials before reaction, and filtering to obtain the polyester resin for the two-piece tank ink.

Specifically, the specifications of the obtained novel polyester resin for two-piece can ink are as follows: linseed oil having a viscosity (mPa & s/25 ℃) of 30000-.

The invention also provides a two-piece can printing ink which is prepared from the following raw materials in parts by weight:

45 to 55 parts of the polyester resin for two-piece can ink according to claim 1,

Furthermore, the molecular weight of the polyester resin for the two-piece tank ink is 3000-6000, and the hydroxyl value is 20-100 mgKOH/g.

Further, the amino resin is any one or a mixture of more than two of urea-formaldehyde resin, melamine-formaldehyde resin and polyamide polyamine epichlorohydrin in any proportion.

Further, the organic solvent is any one or a mixture of more than two of triethylene glycol monobutyl ether, diethylene glycol monobutyl ether, tripropylene glycol propylene glycol butyl ether, dipropylene glycol monobutyl ether, tripropylene glycol and polyalcohol butyl ether in any proportion.

Further, the catalyst is one or a mixture of more than two of p-toluenesulfonic acid, ion exchange resin, aluminum sulfate and heteropoly acid in any proportion.

Further, the organic pigment powder has a yellow spectrum: c.i. pigment yellow 12, c.i. pigment yellow 13, c.i. pigment yellow 14, c.i. pigment yellow 74, c.i. pigment yellow 81, c.i. pigment yellow 83, and the like; orange chromatography: c.i. pigment orange 64, c.i. pigment orange 13, and the like; red color spectrum: c.i. pigment red 48: 2, c.i. pigment red 49: 1, c.i. pigment red 53: 1, pigment red 57: 1, etc.; blue chromatography: c.i. pigment blue 15: 1, c.i. pigment blue 15: 3, c.i. pigment blue 15: 4, C.I. pigment blue 61 in any proportion.

Further, the filler is any one or a mixture of more than two of talcum powder, fumed silica and polytetrafluoroethylene wax in any proportion.

Further, the auxiliary agent is any one or a mixture of two of a wetting agent and a dispersing agent.

The invention also provides a preparation method of the two-piece can printing ink, which comprises the following steps:

1) weighing the raw materials in parts by weight;

2) adding the polyester resin, the amino resin, the organic solvent and the auxiliary agent for the two-piece tank ink of claim 1 into a batching barrel, fully and uniformly stirring until the temperature of the mixture reaches 55-65 ℃,

3) gradually adding organic pigment powder and filler, continuously stirring for 25-35 minutes after adding, grinding the mixture by using a three-roll machine until the fineness is less than 5 mu m, and repeatedly grinding the mixture until the fineness is less than 5 mu m;

4) and (4) adding a catalyst after sampling and detecting the fineness, sampling and detecting the viscosity, hue and dryness of the ink, and packaging after the detection is qualified.

The resin is a carrier of the pigment in the ink, is a core material of the ink, has good and bad performance, and can directly influence the printing adaptability of the ink, such as viscosity, drying property, fluidity and the like. And the protection requirement of the ink film on the substrate after curing.

Various pigment powders are coated with resin by thoroughly mixing and dispersing the pigments with a high-speed stirrer and a three-roll mill to form a viscous colloidal fluid. The ink is uniformly applied to the printing substrate by the printer to display various desired patterns. And then, accelerating the ink curing at high temperature in an oven, and forming a layer of film with color patterns on the substrate.

The curing principle of the ink is that hydroxyl of polyester resin and alkoxymethyl on amino resin in the ink are heated and have a crosslinking reaction under the condition of being catalyzed by p-toluenesulfonic acid (the temperature is 120-150 ℃) to generate a solid which is not softened, and a layer of film which has adhesive force to a substrate and color is formed.

The addition of the organic solvent and the auxiliary agent is to adjust the viscosity and viscosity of the ink more appropriately, thereby being beneficial to the printing performance of the ink.

Compared with the prior art, the invention has the advantages of positive and obvious technical effect. The two-piece can ink obtained by the method has the advantages of good viscoelastic thixotropy, pigment wettability, scratch resistance, ink flying resistance and the like, particularly the pencil hardness can reach 7H, and the ink flying test reaches 5 grades.

Detailed Description

The embodiment of the invention provides a preparation method of polyester resin for a two-piece tank, which comprises the following steps:

introducing nitrogen, putting 25-32 parts of dicarboxylic acid, 12-16 parts of saturated fatty acid, 6-12 parts of dihydric alcohol, 24-32 parts of polyhydric alcohol, 8-13 parts of anhydride, 1-3 parts of lactone, 0.02-0.03 part of catalyst, 0.2-0.5 part of antioxidant and the like into a reaction kettle, slowly heating to 130 ℃, and preserving heat for 1H;

heating to 148-152 ℃, and keeping the temperature for 1H;

heating to 158-162 ℃, and dividing water by a water separator and preserving heat for 2H;

heating to 168-172 ℃, and keeping the temperature for 0.5H;

heating to 178-182 ℃, and keeping the temperature for 2H;

heating to 188-192 ℃, and keeping the temperature for 0.5H;

heating to 198-200 ℃, and keeping the temperature for 1H;

heating to 202-205 ℃, and keeping the temperature for 1H;

and stopping nitrogen after heat preservation is finished. Adding a vacuum pump to firstly vacuumize the device to 0.05MPa of vacuum degree and keep the vacuum degree for 20 minutes, and then gradually increasing the vacuum degree to 0.08MPa and keeping the vacuum degree for 20 minutes;

and (3) testing the acid value of the resin, when the acid value is less than 35mgKOH/g, cooling to 70-80 ℃, adding a diluent polyethylene glycol 200 accounting for 20% of the total mass of the materials before reaction, and filtering to obtain the polyester resin for the two-piece tank ink.

The specification of the resin is as follows: linseed oil having a viscosity (mPa & s/25 ℃) of 30000-.

The invention also discloses a method for preparing the two-piece can printing ink by using the polyester resin. The preparation process of the two-piece can ink comprises the following steps:

adding 45-55 parts of polyester resin, 7-12 parts of amino resin, 3-15 parts of organic solvent and 1-4 parts of auxiliary agent into a mixing barrel, fully and uniformly stirring until the temperature of the mixture reaches 60 ℃, gradually adding 20-30 parts of organic pigment powder and 3-5 parts of filler, continuously stirring for 30 minutes after the addition is finished, and grinding by using a three-roll machine to obtain the fineness. Sampling and detecting the fine powder, and then adding 0-0.5 part of catalyst. And sampling to detect the viscosity, hue and dryness of the ink, and packaging after the detection is qualified.

Example 1

A method for preparing a polyester resin for two-piece cans, the method comprising:

preparing polyester resin, wherein the weight percentage of each component is as follows:

isophthalic acid	29.67％
		Lauric acid	15.4％
2-Ethyl-2-butyl-1, 3-propanediol	8.2％
		Trimethylolpropane	31.0％
Phthalic anhydride	12.2％
		Caprolactone ester	3％
Dibutyl tin oxide	0.03％
		Dibutylhydroxytoluene	0.5％

Introducing nitrogen, putting all materials in equal proportion into a reaction kettle, slowly heating to 130 ℃, and keeping the temperature for 1H;

heating to 148-152 ℃, and keeping the temperature for 1H;

heating to 168-172 ℃, and keeping the temperature for 0.5H;

heating to 178-182 ℃, and keeping the temperature for 2H;

heating to 188-192 ℃, and keeping the temperature for 0.5H;

heating to 198-200 ℃, and keeping the temperature for 1H;

heating to 202-205 ℃, and keeping the temperature for 1H;

Technical indices with polyester resin: linseed oil viscosity (mPa & s/25 ℃)30000-, acid value (mgKOH/g) less than or equal to 35, solid content > 85%, softening point-20-0 ℃, hydroxyl value of 20-100mg KOH/g, molecular weight (Mw) 3000-.

Example 2

Preparing two-piece jar printing ink yellow base color ink, wherein the weight percentage of each component is as follows:

polyester resin (from example 1)	45％
		Diethylene glycol monobutyl ether	4％
Tripropylene glycol	8％
		Dispersing agent: methylene bis (naphthalene) sulfonic acid sodium salt	3％
Fumed silica	2％
		C.i. pigment yellow 83	25％
Amino resin	12％
		P-toluenesulfonic acid	1％

The preparation method comprises the following steps: the polyester resin (obtained in example 2), diethylene glycol monobutyl ether, tripropylene glycol, wetting dispersant and amino resin were mixed, stirred at high speed with a stirrer until the temperature of the mixture reached 60 ℃, then c.i. pigment yellow 83 and fumed silica were added with stirring, and after the addition, stirred at high speed for 30 minutes. Then grinding by a three-roll grinder. When the fineness is less than 5 μm, adding p-toluenesulfonic acid catalyst and stirring uniformly. And then testing viscosity, ink flying, color phase and drying property, and packaging after the product is qualified.

Example 3

Preparing two-piece tank printing ink red base color ink, wherein the weight percentage of each component is as follows:

the preparation method comprises the following steps: the polyester resin (obtained in example 1), diethylene glycol monobutyl ether, tripropylene glycol, wetting dispersant, amino resin were mixed, stirred at high speed with a stirrer until the mixture temperature reached 60 ℃, and then c.i. pigment red 48: 2 and fumed silica, and stirring at high speed for 30 minutes after the addition. Then grinding by a three-roll grinder. When the fineness is less than 5 μm, adding p-toluenesulfonic acid catalyst and stirring uniformly. And then testing viscosity, ink flying, color phase and drying property, and packaging after the product is qualified.

Example 4

Preparing blue base ink of two-piece tank ink, wherein the components in percentage by weight are as follows:

polyester resin (from example 1)	40％
		Diethylene glycol monobutyl ether	8％
Tripropylene glycol	6％
		Dispersing agent: methylene bis (naphthalene) sulfonic acid sodium salt	3％
Fumed silica	1％
		C.i. pigment blue 15: 3	32％
Amino resin	9％
		P-toluenesulfonic acid	1％

The preparation method comprises the following steps: the polyester resin (obtained in example 1), diethylene glycol monobutyl ether, tripropylene glycol, wetting dispersant, amino resin were mixed, stirred at high speed with a stirrer until the mixture temperature reached 60 ℃, and then c.i. pigment blue 15: 3 and fumed silica, and stirring at high speed for 30 minutes after the addition. Then grinding by a three-roll grinder. When the fineness is less than 5 μm, adding p-toluenesulfonic acid catalyst and stirring uniformly. And then testing viscosity, ink flying, color phase and drying property, and packaging after the product is qualified.

Example 5

Preparing two-piece tank printing ink orange base printing ink, wherein the components in percentage by weight are as follows:

the preparation method comprises the following steps: polyester resin (obtained in example 1), diethylene glycol monobutyl ether, tripropylene glycol, wetting dispersant and amino resin were mixed, stirred at high speed with a stirrer until the temperature of the mixture reached 60 ℃, then c.i. pigment orange 64 and fumed silica were added with stirring, and after the addition, stirred at high speed for 30 minutes. Then grinding by a three-roll grinder. When the fineness is less than 5 μm, adding p-toluenesulfonic acid catalyst and stirring uniformly. And then testing viscosity, ink flying, color phase and drying property, and packaging after the product is qualified.

Performance testing of the inks

The base ink for the two-piece can ink prepared in the above examples 2, 3, 4 and 5 and the base ink for the other domestic two-piece can ink currently on the market were used for the ink base performance test, and the test results are shown in table one. Taking a proper amount of printing ink, spreading the printing ink by using a multi-section spreading instrument, coating the printing ink on a plate with the thickness of 1 square meter being 0.5-2 g on a passivated aluminum tank, directly coating common gloss oil (the weight of the dry film of the gloss oil on the plate with the thickness of 1 square meter being 3-4 g) by using a wire bar coater, and baking the plate in an oven at the temperature of 200 ℃ for 2min, wherein the curing temperature is 190-. And (3) testing the physical and chemical properties of the coating, and after the coating is cooked at 85 ℃ for 30min, testing the common cooking performance of the ink, wherein the test results are shown in a table II.

Taking a proper amount of printing ink, spreading the printing ink by using a multi-section color spreading instrument, coating the printing ink on a plate with the thickness of 1 square meter being 0.5-2 g, coating the printing ink on a passivated aluminum tank, directly coating high-temperature gloss oil (the weight of the dry film of the gloss oil on the plate with the thickness of 1 square meter being 3-4 g) by using a wire bar coater, baking the printing ink in a baking oven at the temperature of 200 ℃ for 2min, and curing the printing ink at the temperature of 190-195 ℃. And testing the physical and chemical properties of the coating, and after steaming at 121 ℃ for 30min, testing the high-temperature steaming performance of the ink, wherein the test results are shown in a table II.

Table one: base ink basic performance data comparison table

Table two: base color ink development performance data comparison table

In tables I and II:

(1) the viscosity was measured using a viscometer at a working temperature of 32 ℃ and a reading after 1 minute at 400 rpm.

(2) The fluidity is the ink film development diameter after 0.1g of ink is subjected to a pressure of 100g for 10min at a temperature of 25 ℃.

(3) The ink flying performance is tested by a viscosity meter, and the ink gram is taken by the receiving object after the working temperature is 32 ℃ and the rotating speed is 1 minute at 1200. The 5 th level represents less flying ink, and the 0 th level represents more flying ink.

(4) Fineness is the result of direct reading with a fineness board.

(5) The transferability was measured by a multi-stage color developing instrument, and the transfer effect of the ink from the rubber roller to the steel roller was good, and OK was good.

(6) The solvent resistance is calculated once after the non-dust cloth is stained with butanone and the designated coating area is wiped back and forth with 1KG force.

(7) The flexibility is that the base plate is punched into a cup shape with the diameter of 45mm and the height of 10mm, and whether the appearance of the coating has the phenomenon of peeling and paint falling is observed. OK represents good flexibility.

(8) The boiling resistance is that the finished product is boiled in water bath at the constant temperature of 85 ℃ for 30min, and the appearance and the adhesive force of the coating are observed. The 0 grade represents good adhesion, and the coating does not turn white and fade.

(9) The high-temperature cooking resistance is that the finished product is cooked in water bath at the temperature of 121 ℃ for 30min, and the appearance and the adhesive force of the coating are observed. The 0 grade represents good adhesion, and the coating does not turn white and fade.

(10) The heat resistance is the condition that the finished product is placed in an oven at 200 ℃ for 30min, and the color change of the coating is observed. OK represents that the coating has no obvious yellowing and fading phenomena.

(11) The gloss retention is the ratio of the gloss of the finished product before and after poaching, expressed in% by number. The higher the light retention, the more excellent the performance.

(12) And drawing a cross-shaped grid shape on the finished product coating by using a grid cutter, and drawing a cutter transversely and longitudinally to form one hundred small grids with the grid size of 1mm X1 mm. The cut of the hundred grid knife should reach the bottom layer of the oil layer. The incision was taped with 3M tape and pulled apart, the tape having an adhesion of 350-400 g/sq. And finally, observing the condition of the grid area by using a magnifying glass, and verifying the adhesion performance of the coating or the ink on the surface of the product by using an ink 1mm cross method or an adhesive tape method. The 0 rating represents no peeling of the ink film, and the 5 rating represents 40% peeling of the ink film.

The first and second comparison data show that the two-piece ink for the tank made of the polyester resin prepared by the invention has greatly improved ink flying and the surface hardness of the ink, and reduces the occurrence probability of the problems of tank body pollution caused by the ink, necking scratch and the like in production. The polyester resin has low requirements on reaction equipment, and the synthesis process is simple and is more beneficial to large-scale production. Has great advantages for competition in the same industry.

Claims

1. A polyester resin for two-piece can ink, which is characterized in that: the material is prepared from the following raw materials in parts by weight:

2. the polyester resin for two-piece can ink according to claim 1, wherein the dicarboxylic acid is one or a mixture of two or more of terephthalic acid, isophthalic acid, phthalic acid, adipic acid, succinic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, malic acid, dimer acid, tetrahydrophthalic acid, hexahydroisophthalic acid, 1, 2-cyclohexanedicarboxylic acid, and 1, 4-cyclohexanedicarboxylic acid, the saturated fatty acid is one or a mixture of two or more of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid, the diol is ethylene glycol, 1, 2-propylene glycol, 1, 3-propylene glycol, 1, 4-butylene glycol, 2-methyl-1, 3-propylene glycol, neopentyl glycol, 1, 6-hexylene glycol, 1, 7-heptanediol, 1, 9-nonanediol, hydroxypivalyl hydroxypivalate, 2-ethyl-2-butyl-1, 3-propylene glycol, 2, 4-pentamethyl-1, 3-butylene glycol, 2, 3-trimethylolpropane, 1, 3-trimethylolpropane, pentaerythritol, trimethylolpropane.

3. The method for preparing the polyester resin for two-piece can ink according to claim 1, comprising the steps of:

1) weighing the raw materials in parts by weight;

3) heating to 148-152 ℃, and keeping the temperature for 1H;

5) heating to 168-172 ℃, and keeping the temperature for 0.5H;

6) heating to 178-182 ℃, and keeping the temperature for 2H;

7) heating to 188-192 ℃, and keeping the temperature for 0.5H;

8) heating to 198-200 ℃, and keeping the temperature for 1H;

9) heating to 202-205 ℃, and keeping the temperature for 1H;

10) stopping nitrogen gas after heat preservation is finished; adding a vacuum pump to firstly vacuumize the device to 0.05MPa of vacuum degree and keep the vacuum degree for 15-25 minutes, and then gradually increasing the vacuum degree to 0.08MPa and keeping the vacuum degree for 15-25 minutes;

4. The two-piece can printing ink is characterized by being prepared from the following raw materials in parts by weight:

5. The two-piece can ink of claim 4, wherein: the molecular weight of the polyester resin for the two-piece can ink is as follows: 3000-6000, a hydroxyl value of 20-100mg KOH/g.

6. The two-piece can ink of claim 4, wherein: the amino resin is any one or a mixture of more than two of urea-formaldehyde resin, melamine formaldehyde resin and polyamide polyamine epichlorohydrin in any proportion; the organic solvent is any one or a mixture of more than two of triethylene glycol monobutyl ether, diethylene glycol monobutyl ether, tripropylene glycol propylene glycol butyl ether, dipropylene glycol monobutyl ether, tripropylene glycol and polyalcohol butyl ether in any proportion; the catalyst is any one or a mixture of more than two of p-toluenesulfonic acid, ion exchange resin, aluminum sulfate and heteropoly acid in any proportion; the organic pigment powder has a yellow spectrum: c.i. pigment yellow 12, c.i. pigment yellow 13, c.i. pigment yellow 14, c.i. pigment yellow 74, c.i. pigment yellow 81, c.i. pigment yellow 83, and the like; orange chromatography: c.i. pigment orange 64, c.i. pigment orange 13, and the like; red color spectrum: c.i. pigment red 48: 2, c.i. pigment red 49: 1, c.i. pigment red 53: 1, pigment red 57: 1, etc.; blue chromatography: c.i. pigment blue 15: 1, c.i. pigment blue 15: 3, c.i. pigment blue 15: 4, any one or a mixture of more than two of the C.I. pigment blue 61 in any proportion; the filler is any one or a mixture of more than two of talcum powder, fumed silica and polytetrafluoroethylene wax in any proportion.

7. The two-piece can ink of claim 4, wherein: the auxiliary agent is any one or a mixture of two of a wetting agent and a dispersing agent.

8. The method of preparing a two-piece can ink of claim 4, comprising the steps of:

1) weighing the raw materials in parts by weight;

2) adding the polyester resin, the amino resin, the organic solvent and the auxiliary agent for the two-piece can ink, which are disclosed by claim 1, into a batching barrel, and fully and uniformly stirring until the temperature of the mixture reaches 55-65 ℃;