Development and research of polyurethane bright pa

2022-10-02
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Development and research of polyurethane gloss coating for printing paper

Abstract: the preparation method of polyurethane coating for printing paper is introduced, and the effects of resin, curing agent type, crosslinking rate and branch structure on product properties are discussed. The results show that the coating has excellent solvent resistance and wear resistance

key words: Polyurethane bright paint; Solvent resistance; Wear resistance

Chinese Library Classification Number: tq630.7 document identification code: a article number: (2013)

0 · introduction

since the reform and opening up, with the continuous improvement of people's living standards, the grade of room decoration has also been gradually improved, which puts forward new requirements for the creative design of wood furniture, and naturally puts forward higher requirements for the variety, quality and grade of modern wood furniture []. Sticker furniture is favored by the majority of consumers for its lifelike wood grain, low price and good quality. However, the high-end market of sticker furniture coating has been occupied by foreign coating companies, resulting in the high cost of furniture factories. In order to reduce the production cost of furniture factories, improve enterprise efficiency, and meet the market demand, we have developed polyurethane coating for printing paper. This paper focuses on the solvent resistance and wear resistance of polyurethane gloss finish, analyzes the influence of resin, curing agent type, cross-linking rate, cross-linking degree and branch structure on product performance, and through a large number of experiments, a scratch resistant, solvent resistant and wear-resistant polyurethane gloss finish is finally prepared, and its printability (fast drying, meeting the requirements of assembly line) can completely replace imported products, Industrial production has been affirmed by customers

1. Experimental part

1.1 raw material

a component: under the needs of technological innovation and convenient operation, the modified acrylic resin, modified polyester resin, aldehyde ketone resin, chloroacetic acid resin and solvent are all industrial grade. Additives, Digo, slock

b component (curing agent): TDI adduct, TDI Trimer, HDI Trimer

diluents: toluene, xylene, ethyl acetate, all of which are industrial grade

1.2 experimental equipment

sfj-400 grinding, stirring and dispersing multipurpose machine, Shanghai Modern Environmental Engineering Technology Co., Ltd; Paint film preparer, Shanghai Pushen Chemical Machinery Co., Ltd; Portable caien cup, Taiwan

1.3 formula

see Table 1 for the distribution of group a polyurethane bright finish

Table 1 component a formula of polyurethane bright finish paint

see Table 2 for the formula of curing agent supporting polyurethane bright finish paint, which ranks first in the world

Table 2. See Table 3 for the formula of the curing agent supporting the polyurethane gloss finish.

see Table 3 for the formula of the diluent supporting the polyurethane gloss finish

Table 3 diluent formula for polyurethane bright finish paint

1.4 preparation and coating of paint

paint component A and component B according to the following construction ratio, m (component a) ∶ m (component B) = 100:30100:40100:50, adjust the viscosity to 16S with diluent, and use 50 for the adjusted paint μ M paint film preparer is evenly coated on the paper, roasted in the 150 ℃ oven for 3min, or roasted in the 120 ℃ oven for 10min, and then taken out. Wait a moment, wipe the paper back and forth with cotton gauze dipped in butanone (MEK), and judge its solvent resistance by the degree of damage of the paint film (loss of light and color); Use JM-1 paint film abrasion tester to test its abrasion resistance, and use 3M tape to peel it to test whether it is easy to release

1#a group assigned 1#, 2#, 3# #b component drying speed, but the wear resistance was not very good; 3. The surface crusting of component A is too fast, which is not conducive to on-site operation; 4 #, 5 #, 6 #, group A is allocated with 1 #, 2 #, 3 #, and the dry speed of component B is all right, but the wear resistance is best with group 6 #, group A is allocated with 1 # B. 4 #, 5 #, 6 # group a allocated 4 # B component drying speed is slightly slow, so the dosage of drier needs to be increased in the formula. According to the on-site operation, the paint surface should be skinned slowly. After printing, the paint film dries quickly, improving the printing speed. Finally, it is confirmed that 6 # group a allocated 1 # B component is the best combination, and when m (component a) ∶ m (component B) =100:40, the abrasion resistance and solvent resistance of the paint film can meet the online operation requirements of the printing plant. At present, the product has been industrialized for 2 years, completely replacing imported products, reducing the cost of printing plants, improving efficiency, and has been highly praised by customers

1.5 performance index of polyurethane bright finish paint

performance index of polyurethane bright finish paint is shown in Table 4

Table 4 performance index of polyurethane bright finish

2. Precautions for field application

(1) use summer diluent in summer and winter diluent in winter

(2) if the paper is rough, it can be primed with paper sealing paint, and then coated with PU bright finish

(3) if customers require different gloss, add matting paste and adjust it to the required gloss

(4) if the customer requires the product to resist yellowing (printing light color patterns), use HDI Trimer curing agent

(5) if the customer has high requirements for solvent resistance and wear resistance of face paint, paper sealing paint can also be used for priming, and then Pu bright finish paint can be applied

3. Results and discussion

to improve the scratch resistance, wear resistance and solvent resistance of polyurethane bright paint film, it is necessary to make the surface of the paint film have sufficient tensile and compressive stress, that is, there should be a reasonable balance between the flexibility and rigidity of its surface. In the combination of rigidity and flexibility, acrylic acid and polyester are used for grafting reaction, which can balance the hardness, flexibility and other properties, Because polyester itself has a small amount of c=c bonds, they can be copolymerized with acrylic monomers [3]

3.1 improving rigidity

some monomer polymerized acrylic resins with higher glass transition temperature can be selected, such as acrylic acid, methacrylic acid and other monomer polymerized resins, which have high hardness, rapid drying, high tensile strength and low elongation. In addition, the distribution and size of the relative molecular weight are also important. If the relative molecular weight is evenly distributed, the performance is relatively uniform. The low relative molecular weight will not shrink greatly during the drying process of the paint film, which is very helpful for the resistance of the paint film to "subsidence", but the functional group distribution of the polymerized acrylic resin is relatively random, which affects the bridge density of its reaction with the curing agent to a certain extent, Therefore, it is necessary to consider a compatible polyester resin for grafting

3.2 improve flexibility

the toughness characteristics of polyester resin itself can make the surface of paint film elastic and provide tensile capacity, but the distribution of functional groups of condensation polyester is more regular. In order to achieve dense bridging rate, polyester resin with branched structure and more branches should be selected

in short, in order to improve the wear resistance of the paint film, we must achieve the combination of hardness and softness, as well as hardness and toughness

3.3 effect of curing agent

tdi adduct or its trimer is helpful to the crosslinking speed. Its dry speed and hardness are ideal, but its crosslinking quality is not as good as that of HDI Trimer system curing agent, resulting in poor scratch resistance, wear resistance and weather resistance. However, HDI curing agent solidifies slowly, and too slow crosslinking rate is easy to produce many paint film defects, such as dark bubbles, wrinkles, and low printing speed, Reduce production efficiency [4]

in order to solve the above problems, it is necessary to catalyze the reaction speed. However, if general metal driers are used, their type and dosage should be strictly controlled, otherwise the application period is too short, resulting in the scrapping of the coating. Therefore, when selecting driers, their impact on the application period and the efficiency of catalysis should be carefully considered

3.4a, the influence of the distribution ratio of group B

the amount of curing agent is high, and the drying speed and solvent resistance of the paint film are better. This work should be carried out by professionals, but if the proportion is too high, the application period is short, it is not conducive to on-site operation and the cost is high, and the customer is unwilling to accept it. The amount of curing agent is too small, and the drying speed of paint film is slow, which is also not conducive to improving the printing speed on site. The curing agent should have an appropriate amount to take into account the film performance, customer site application and product cost

the wear resistance of the paint film is also related to the friction coefficient of the paint film. Adding wax or fluorosurfactant can reduce the surface tension of the film, thus reducing the friction coefficient of the paint film and increasing its wear resistance [5]

4 · conclusion

through the scientific design of resins, additives and other materials and their proportions, a wear-resistant and solvent resistant polyurethane bright finish for printing paper has been developed. This product has high cost performance, strong competitiveness, and performance to meet customer requirements. It has completely replaced imported products and obtained industrial production, which has been highly praised by customers

references

[1] Geng Yaozong Production technology and practical formula of modern wood furniture paint [M] 2nd Edition Beijing: China Light Industry Press, 2007:

[2] Dai Xinyou Furniture coating and painting technology [M] 2nd Edition Beijing: Chemical Industry Press, 2008:268

[3] Zhou Han Preparation of 2KPU bright products with scratch resistance and wear resistance [ J ] China paint, 2005 (02):

[4] Yu Zhaonian Coating technology [M] Volume II Beijing: Chemical Industry Press, 1999:350

[5] Hong Xiaoyin, Feng Hanbao Paint chemistry [M] Beijing: Science Press, 1997:129

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