CN115404715A - A coating for improving the printing effect of paper ink and its preparation method and application - Google Patents

Abstract

The invention discloses a paint for improving the printing effect of paper ink and its preparation method and application, belonging to the technical field of printing paint, and the key points of the technical scheme are: the preparation raw materials of the paint include chitosan, nano-cellulose and starch; The preparation steps are: first prepare a chitosan solution, then uniformly disperse the nanocellulose into the chitosan solution to obtain a homogeneous nanocellulose-chitosan solution; finally add anionic starch to the nanocellulose-shell In the polysaccharide solution, the nanocellulose-chitosan composite starch coating is obtained after gelatinization at a constant temperature. The coating of the present invention can be applied to the coating of kraft paper, and improve the water-based ink printing effect, optical properties, mechanical properties and water resistance of kraft paper; and has the advantages of safety and environmental protection; the coating can also improve the overall printing quality, which is convenient to meet the needs of the market Demand for fine print.

Description

A coating for improving the printing effect of paper ink and its preparation method and application

technical field

The invention relates to the technical field of motor casings, in particular to a coating for improving the printing effect of paper ink and its preparation method and application.

Background technique

Kraft paper is increasingly favored by food producers, packers and environmentalists for its toughness, strength, unbleached treatment and attractive natural brown appearance.

However, compared with the bright and white sulfate bleached cardboard, in order to ensure its natural and environmental protection, the surface of kraft paper is not coated, the porosity between fibers is higher, and the surface smoothness is lower. The ink has strong permeability during printing, which leads to poor reproducibility of ink color; especially the printing effect of water-based ink developed in recent years, such as printing density, ink layer friction resistance, etc., needs to be improved, resulting in Kraft paper packaging printing has a single tone and the overall printing quality is not high, which is far from meeting the needs of fine prints.

In order to solve the above problems, a coating for improving the printing effect of paper ink and its preparation method and application are provided on the basis of the prior art.

Contents of the invention

The purpose of the present invention is to provide a kind of coating that improves paper ink printing effect and its preparation method and application, this coating can be applied to the coating of kraft paper, and improve the water-based ink printing effect of kraft paper, such as the color saturation of printing paper, gloss The properties such as printing density, friction resistance, etc. are all improved; secondly, the coating can also improve the optical properties, mechanical properties and water resistance of kraft paper; thirdly, its ingredients are natural products such as starch, nanocellulose, chitosan, etc. , the raw materials are widely available, and can be naturally degraded, which has the advantages of safety and environmental protection; finally, the coating can also improve the overall printing quality, and can effectively improve the kraft paper packaging caused by printing density and poor friction resistance of the ink layer. The problem of single printing tone is convenient to meet the market's demand for fine prints.

Above-mentioned technical purpose of the present invention is achieved through the following technical solutions:

The invention discloses a coating for improving the printing effect of paper water-based ink, and the preparation raw materials of the coating include chitosan, nano-cellulose and starch.

Further, the starch is anionic starch; the adding weight ratio of the chitosan and nanocellulose is 1:2-5, and the adding weight ratio of the anionic starch and nanocellulose-chitosan solution is 20～ 30: 100-150.

The present invention also provides a kind of preparation method of the coating that improves paper water-based ink printing effect, it is characterized in that: comprise the steps:

S1, dissolving chitosan in an acetic acid solution to obtain a solution one; then adjusting the pH of the solution one by sodium hydroxide to obtain a chitosan solution;

S2. Uniformly dispersing the nanocellulose into the chitosan solution described in step S1 to obtain a homogeneous nanocellulose-chitosan solution;

S3. Add the anionic starch into the nano-cellulose-chitosan solution, stir evenly, then heat in a water bath and gelatinize at a constant temperature in sequence to obtain the nano-cellulose-chitosan composite starch coating.

Further, the mass fraction of the acetic acid solution described in step S1 is 2-5%; the pH value of the chitosan solution described in step S1 is 6-7.

Further, in step S2, a homogeneous nanocellulose-chitosan solution is obtained through a homogenizer; wherein, the homogenization speed of the homogenization process is 28000-30000rp/min, and the time of the homogenization process is 5-8min.

Further, in step S3, when the water bath is heated, the mixture formed by the anionic starch and the nanocellulose-chitosan solution needs to be stirred, and the stirring starting temperature of the mixture is 75° C. to 80° C.; and the temperature of the mixture reaches At 95°C, it enters the constant temperature gelatinization stage.

Further, the viscosity of the nanocellulose-chitosan composite starch coating is 2500-2800cp.

By adopting the above-mentioned technical scheme, firstly, chitosan, nanocellulose and starch are all natural products, and all of them have the characteristics of abundant reserves and good degradation performance. Therefore, chitosan, nanocellulose and anionic starch are used as Coatings synthesized from raw materials have the advantages of environmental protection and safety.

Secondly, anionic starches include phosphate starch, starch with carboxyl and sulfonic acid groups, xanthate starch, oxidized starch with carboxyl and carbonyl groups, etc.; nanocellulose in coatings has the characteristics of high strength, and the surface of nanocellulose It has abundant active groups. Therefore, when the coating containing nanocellulose penetrates into the pores of paper fibers, it can form stable bonds between fibers, between fibers and starch, and between starch and starch. , so that it can effectively modify the paper surface.

Again, on the basis of the mutual bonding between paper fiber, starch and nanocellulose, the acidified chitosan has a positive charge, and the anionic starch has a negative charge. In addition, chitosan can also form a stable system with nanocellulose rich in surface hydroxyl groups; therefore, the binding force between kraft paper fiber, nanocellulose, starch and chitosan can be further enhanced.

Finally, while starch has excellent viscosity and film-forming properties, due to its semi-crystalline nature, film-forming mechanical properties are poor; nanocellulose has the characteristics of large specific surface area, good biocompatibility, and high strength; chitosan Sugar also has good antibacterial and film-forming properties. Therefore, the components within the specific parameter range provided by this scheme complement each other and cooperate with each other to obtain optical properties, mechanical properties, water resistance, and printing effects. , leveling and antibacterial properties are relatively excellent coatings; on the contrary, when preparing coatings, the corresponding components are higher or lower than the corresponding parameter range, and its fluidity, viscosity and leveling properties are poor.

The present invention also provides an application of a coating for improving the printing effect of paper water-based ink, and the nano-cellulose-chitosan composite starch coating is applied to improve the optical properties, mechanical properties, water resistance and printing effect of the kraft paper surface.

Further, the optical properties include one or a combination of gloss and smoothness; the mechanical properties include one or a combination of folding resistance and tear resistance; the printing effect includes color saturation, gloss One or a combination of degree, printing density, and friction resistance of printed graphics.

By adopting the above technical scheme, the porosity between fibers can be effectively reduced; before coating, the surface of kraft paper has clearly visible pores formed by intersecting fibers and fibers, and the surface is rough; after coating, the coating is evenly attached to the surface of the paper, All pores on the surface are filled and the surface is smooth. There is still a large amount of pore structure in the lower layer where no paint penetrates into the kraft paper, while part of the paint has penetrated into the pores between the fibers in the upper surface where the paint has been coated, indicating that the paint has good leveling and viscosity. Moderate, good film-forming property, good coating effect.

Nanocellulose-chitosan composite starch coating has good leveling and film-forming properties, making the printing density of kraft paper after coating significantly higher than that before coating; because the coating improves the smoothness and gloss of kraft paper degree, so that the color saturation and gloss of the printed pattern can be improved.

At the same time, the kraft paper fiber, nanocellulose, chitosan and starch are closely combined through multiple interactions, so that the nanocellulose-chitosan composite starch coating can obtain excellent hydrophobicity; on the one hand, after kraft paper coating , the paint penetrates into the kraft paper fiber pores, the water absorption of the kraft paper is significantly reduced, and the water resistance is significantly enhanced; Ink color rendering power.

In addition, due to the combination of high-strength nanocellulose and other ingredients in the coating, the folding and tearing resistance of kraft paper after coating have increased to varying degrees, of which the folding resistance increased by 15.2%, and the tearing resistance increased by 15.2%. The increase is 19.3%, indicating that the coating can better improve the mechanical properties of kraft paper, and enhance the resistance to folding and tearing during the printing production process of kraft paper. It can be seen from the above that the nanocellulose-chitosan composite starch coating can effectively improve the optical properties, mechanical properties, water resistance and printing effect of the kraft paper surface.

In summary, the present invention has the following beneficial effects:

1. The nanocellulose-chitosan composite starch coating of the present invention can be applied to the coating of kraft paper, and improve the water-based ink printing effect of kraft paper, such as the color saturation, gloss, printing density, friction resistance, etc. of printing paper performance has been improved.

2. The nanocellulose-chitosan composite starch coating of the present invention can improve the optical properties, mechanical properties and water resistance of kraft paper, such as improving the folding resistance, tear resistance, water resistance and other properties of paper.

3. The composition of the nanocellulose-chitosan composite starch coating of the present invention is the natural products such as starch, nanocellulose, chitosan, and raw material source is wide, and can degrade naturally, can not produce harm to environment; Has safety and environmental protection The advantages.

4. The nanocellulose-chitosan composite starch coating of the present invention can improve the overall printing quality, and can also effectively improve the problem of single color tone of kraft paper packaging printing caused by printing density, poor friction resistance of the ink layer, etc. It is convenient to meet the market demand for fine prints.

Description of drawings

Fig. 1 is the comparative figure of kraft paper surface glossiness and smoothness before and after coating of the application example of the present invention;

Fig. 2 is a comparison chart of kraft paper folding endurance and tear resistance before and after coating of an application example of the present invention;

Fig. 3 is a comparison diagram of the printing effect of kraft paper before coating and after coating of the application example of the present invention;

Fig. 4 is a comparison chart of printing densities of kraft paper water-based inks before and after coating in an application example of the present invention.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the present invention is described in further detail:

Embodiment 1: a kind of preparation method of the coating that improves paper water-based ink printing effect, comprises the steps:

S1, 1 part of chitosan is dissolved in 2% acetic acid solution, and then the pH of the solution is adjusted to 6 by sodium hydroxide to obtain a chitosan solution;

S2. Uniformly disperse 2 parts of nanocellulose into the chitosan solution in step S1 to obtain a homogeneous nanocellulose-chitosan solution.

Wherein, the homogeneous nanocellulose-chitosan solution is obtained through a homogenizer; the rotation speed of the homogenization process is 28000rp/min, and the time of the homogenization process is 5min.

S3. Add 20 parts of anionic starch into 100 parts of nanocellulose-chitosan solution, stir evenly, then heat in a water bath and gelatinize at constant temperature to obtain nanocellulose-chitosan composite starch coating.

Wherein, in step S3, when the water bath is heated, the mixture formed by the anionic starch and the nanocellulose-chitosan solution needs to be stirred, and the stirring starting temperature of the mixture is 75°C; and when the temperature of the mixture reaches 95°C, Enter the constant temperature gelatinization stage; the viscosity of the nanocellulose-chitosan composite starch coating is 2500cp.

Embodiment 2: a kind of preparation method of the coating that improves paper water-based ink printing effect, comprises the steps:

S1, 1 part of chitosan is dissolved in 3% acetic acid solution, and then the pH of the solution is adjusted to 6.5 by sodium hydroxide to obtain a chitosan solution;

S2. Uniformly disperse 4 parts of nanocellulose into the chitosan solution in step S1 to obtain a homogeneous nanocellulose-chitosan solution.

Wherein, the homogeneous nanocellulose-chitosan solution is obtained through a homogenizer; the rotation speed of the homogenization process is 29000rp/min, and the time of the homogenization process is 7min.

S3. Add 25 parts of anionic starch into 125 parts of nanocellulose-chitosan solution, stir evenly, then heat in a water bath and gelatinize at constant temperature to obtain nanocellulose-chitosan composite starch coating.

Wherein, in step S3, when the water bath is heated, the mixture formed by the anionic starch and the nanocellulose-chitosan solution needs to be stirred, and the stirring starting temperature of the mixture is 77°C; and when the temperature of the mixture reaches 95°C, Enter the constant temperature gelatinization stage; the viscosity of the nanocellulose-chitosan composite starch coating is 2650cp.

Embodiment 3: a kind of preparation method of the coating that improves paper water-based ink printing effect, comprises the steps:

S1, 1 part of chitosan is dissolved in 5% acetic acid solution, and then the pH of the solution is adjusted to 7 by sodium hydroxide to obtain a chitosan solution;

S2. Uniformly disperse 5 parts of nanocellulose into the chitosan solution in step S1 to obtain a homogeneous nanocellulose-chitosan solution.

Wherein, the homogeneous nanocellulose-chitosan solution is obtained through a homogenizer; the rotation speed of the homogenization process is 30000rp/min, and the time of the homogenization process is 8min.

S3. Add 30 parts of anionic starch into 150 parts of nanocellulose-chitosan solution, stir evenly, then heat in a water bath and gelatinize at constant temperature to obtain nanocellulose-chitosan composite starch coating.

Wherein, in step S3, when the water bath is heated, the mixture formed by the anionic starch and the nanocellulose-chitosan solution needs to be stirred, and the stirring starting temperature of the mixture is 80°C; and when the temperature of the mixture reaches 95°C, Enter the constant temperature gelatinization stage; the viscosity of the nanocellulose-chitosan composite starch coating is 2800cp.

Application example: the application of a coating to improve the printing effect of paper water-based ink, using a fully automatic film coating instrument, and using a 15μm wire rod equipped with a fully automatic film coating instrument, the prepared nanocellulose- Chitosan composite starch coating is uniformly coated on the surface of kraft paper, and the number of times of coating is 1 time. After the coating is dried, the coated kraft paper is stored under constant temperature and humidity conditions, and its optical properties and mechanical properties are analyzed. , water resistance and printing effect.

The analysis results are as follows:

1) Optical performance analysis

The gloss and smoothness of the kraft paper surface before and after coating were detected and analyzed respectively.

Analysis results: As shown in Figure 1, the gloss of kraft paper after coating has been increased by nearly 1 times, and the smoothness has increased by 28.6%, indicating that the coating has greatly improved the optical properties of the kraft paper surface; The effect of kraft paper packaging and decoration is improved, which makes it possible for kraft paper to be used in high-end and exquisite packaging, thereby improving the economic benefits of products.

2) Analysis of mechanical properties

The folding endurance and tear resistance of kraft paper before and after coating were tested and analyzed respectively.

Analysis results: As shown in Figure 2, the folding resistance and tear resistance of kraft paper after coating have different degrees of increase, among which, the coating of nano-cellulose-chitosan composite anionic starch is higher than that of anionic starch coated. Compared with uncoated kraft paper, the kraft paper coated with nanocellulose-chitosan composite anionic starch has a 15.2% increase in folding endurance and a 19.3% increase in tear resistance. It shows that the nanocellulose-chitosan composite anionic starch coating can better improve the mechanical properties of kraft paper, and enhance the folding resistance and tear resistance of kraft paper printing production process.

3) Water resistance analysis

The water absorption of kraft paper before and after coating was tested and analyzed respectively.

Analysis results: As shown in Table 1, the water absorption of kraft paper after coating is significantly reduced, indicating that its water resistance is enhanced.

Water absorption of kraft paper before and after coating in table 1

4) Analysis of printing effect

a. Printed color saturation and gloss contrast

At present, the patterns of kraft paper printing products are mostly solid and single-color printing. Therefore, black ink is selected for printing in this embodiment.

The results are as follows: As shown in Figure 3, the left side is the printing effect picture of kraft paper before coating, and the right side is the printing effect picture of kraft paper after coating. It can be seen from the effect comparison chart of the two that the kraft paper after coating The color saturation and gloss of the printed pattern are significantly higher than that of uncoated kraft paper.

b. Printing density comparison

The printed areas of the two are measured with a spectrodensitometer to obtain the printing density of the printed pattern.

Analysis results: It can be found that the printing density of kraft paper after coating is significantly higher than that before coating.

c. Adhesion test

Ink printing was carried out on kraft paper without rubbing treatment and rubbing treatment respectively, and the printing densities of the two were detected and analyzed.

Analysis results: As shown in Figure 4, the printing density of the coated kraft paper printing pattern after rubbing and before rubbing is not much different, indicating that the printing ink and the coating have good adhesion, so that the printed graphics have strong rubbing resistance.

This specific embodiment is only an explanation of the present invention, and it is not a limitation of the present invention. Those skilled in the art can make modifications to this embodiment without creative contribution as required after reading this specification, but as long as they are within the rights of the present invention All claims are protected by patent law.

Claims (9)

1. a kind of coating that improves paper water-based ink printing effect is characterized in that: the preparation raw material of described coating comprises chitosan, nano-cellulose and starch. 2. A coating for improving the printing effect of paper water-based ink according to claim 1, characterized in that: the starch is anionic starch; the weight ratio of chitosan and nanocellulose is 1:2-5 , the adding weight ratio of the anionic starch and the nano cellulose-chitosan solution is 20-30:100-150. 3. according to the preparation method of a kind of coating that improves paper water-based ink printing effect according to any one of claim 1-2, it is characterized in that: comprise the steps: S1, dissolving chitosan in an acetic acid solution to obtain a solution one; then adjusting the pH of the solution one by sodium hydroxide to obtain a chitosan solution; S2. Uniformly dispersing the nanocellulose into the chitosan solution described in step S1 to obtain a homogeneous nanocellulose-chitosan solution; S3. Add the anionic starch into the nano-cellulose-chitosan solution, stir evenly, then heat in a water bath and gelatinize at a constant temperature in sequence to obtain the nano-cellulose-chitosan composite starch coating. 4. a kind of preparation method of the coating that improves paper water-based ink printing effect according to claim 3 is characterized in that: the massfraction of the acetic acid solution described in step S1 is 2～5%; The pH of the sugar solution is 6-7. 5. a kind of preparation method of the coating that improves paper water-based ink printing effect according to claim 3 is characterized in that: in step S2, obtain homogeneous nanocellulose-chitosan solution by homogenizer; Wherein, The homogenization speed of the homogenization process is 28000-30000rp/min, and the time of the homogenization process is 5-8 minutes. 6. a kind of preparation method of the coating that improves paper water-based ink printing effect according to claim 3 is characterized in that: in step S3, when water-bath heating needs to form to anion starch and nanocellulose-chitosan solution The mixture is stirred, and the starting temperature of the mixture is 75° C. to 80° C.; and when the temperature of the mixture reaches 95° C., it enters the constant temperature gelatinization stage. 7. a kind of preparation method of the coating that improves paper water-based ink printing effect according to claim 3 is characterized in that: the viscosity of described nano-cellulose-chitosan composite starch coating is 2500-2800cp. 8. An application of a coating to improve the printing effect of paper water-based ink, characterized in that: the nanocellulose-chitosan composite starch coating is applied to improve the optical performance, mechanical properties, water resistance and printing effect of the kraft paper surface . 9. The application of a coating for improving the printing effect of paper water-based ink according to claim 8, characterized in that: the optical properties include one or a combination of gloss and smoothness; the mechanical properties include folding resistance One or a combination of degrees and tear resistance; the printing effect includes one or a combination of color saturation, gloss, printing density, and friction resistance of printed graphics.

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