Preparation and properties of high gloss self drying waterborne alkyd resin
Yang Lifeng 1, Dong Qunfeng 1, peikemei 2
(1. Zhejiang tiannv group paint Co., Ltd., Tongxiang, Zhejiang 314505; 2. Department of chemistry, Zhejiang University of technology, Hangzhou 310018)
Abstract: the basic alkyd resin was synthesized from Tung linoleic acid, linoleic acid, pentaerythritol, neopentyl glycol, isophthalic acid, benzoic acid, maleic anhydride, etc., and then grafted into the basic alkyd resin molecule after mixing styrene, acrylic monomers and organosilicon monomers, a kind of high gloss self drying water-borne acrylic modified alkyd resin for water-based coating was prepared. The molecular structure of the resin and the particle size and contact angle of the emulsion were characterized by infrared spectroscopy (FT-IR), 1H NMR (Zeta), nanoparticle analyzer and contact angle measuring instrument, and the properties of the film were systematically characterized according to the relevant national standards. The results show that the waterborne alkyd resin has the characteristics of high gloss, self drying at room temperature, strong water resistance and excellent adhesion, which can be used to prepare high gloss self drying waterborne alkyd anticorrosive coating.
Key words: high gloss type; self drying at room temperature; waterborne alkyd resin; functional monomer
0 Introduction
Alkyd resin refers to the resin formed by polycondensation of polyols, polyacids and monoacids (vegetable oil), also known as vegetable oil modified polyester resin. Alkyd resin is the backbone resin of coating industry, which has the characteristics of rich raw materials, large quantity, wide range, good comprehensive performance and high cost performance. In recent decades, the emission of volatile organic pollutants (VOC) related to coatings has become an important part of air pollution. Many countries and regions have formulated strict laws, regulations and standards to limit the emission of VOC and encourage the use of environment-friendly products. Environmental friendly coatings have become the development trend of coating industry, among which water-based coatings are widely concerned because of their outstanding green and environmental characteristics. The VOC content of the traditional solvent alkyd coating is very high, and a large amount of VOC is discharged into the environment in the process of production and use, while the VOC content of the waterborne alkyd coating system is very low, which meets the needs of the modern coating industry. Therefore, the development of high-performance waterborne alkyd coatings has become a hot and difficult point in the coating industry.
The waterborne alkyd coatings can be divided into two types: external emulsification and internal emulsification. The alkyd emulsion system prepared by external emulsification has large particle size, storage stability and poor gloss. At present, internal emulsification is mainly used to synthesize water-soluble alkyd resin dispersion in industry. The advantage of waterborne alkyd resin lies in the reduction of VOC content, but there are also obvious disadvantages of waterborne alkyd coating, such as the great latent heat of evaporation and surface tension of water, which is not conducive to the drying, dispersion and coating of pigment, causing flash rust on the metal matrix in the drying process, and affecting the film performance due to hydrolysis of ester bond in the storage process, so it is necessary to improve the paint through comprehensive modification Membrane properties.
In this paper, two-step synthesis of high gloss self drying waterborne acrylic modified alkyd resin was carried out: the first step is to optimize the preparation of basic alkyd resin; the second step is to introduce styrene, acrylic monomers, organosilicon monomers and other mixed modified basic alkyd resin to achieve comprehensive performance improvement and water-based. According to the test results, the synthetic raw materials were optimized and selected, the structure and properties of the synthetic resin were systematically characterized, and compared with the properties of the same coating products on the market.
1 test part
1.1 test materials and instruments
Tonglinoleic acid: industrial grade, Anhui rifinda oil deep processing Co., Ltd.; linoleic acid: industrial grade, Anhui rifinda oil deep processing Co., Ltd.; benzoic acid: industrial grade, Jiangsu Jiamai Chemical Co., Ltd.; isophthalic acid: industrial grade, Korea lotian group; phthalic anhydride: excellent product, Zhenjiang Liancheng Chemical Industry Co., Ltd.; maleic anhydride: excellent Product, Nanjing Zhongteng Chemical Co., Ltd.; pentaerythritol: superior product, Hubei Yihua Chemical Co., Ltd.; KH-570: industrial grade, Nanjing Shuguang Chemical Group Co., Ltd.; methacrylic acid: first grade, Jiangsu Sanmu Chemical Co., Ltd.; methyl methacrylate: industrial grade, Jiangsu Sanmu Chemical Co., Ltd.; butyl methacrylate: Industrial grade, Jiang Su Sanmu Chemical Co., Ltd.; lauryl methacrylate: industrial grade, Zhejiang Kant new materials Co., Ltd.; ethylene TERT carbonate: industrial grade, shell company; styrene: industrial grade, Jiangsu Sanmu Chemical Co., Ltd.; tk250: industrial grade, Shanghai Manhai Schmitt Chemical Co., Ltd.; Di tert butyl peroxide: industrial grade, Nantong Aoyu Chemical Co., Ltd Ltd.; ethylene glycol butyl ether: industrial grade, Jiangsu Dena Chemical Co., Ltd.; propylene glycol methyl ether: industrial grade, Jiangsu Hualun xingjuhe Chemical Sales Co., Ltd.; N, N-Dimethylethanolamine: industrial grade, Shanghai Hechuang Chemical Co., Ltd.
Fourier transform infrared spectrometer: avater370, Nicolet instrument company of the United States; nuclear magnetic resonance spectrometer: avance av400mhz, Bruker company of Switzerland; nano particle size meter: delsa nano C, Beckman Kurt company of the United States; contact angle meter: jc100cs, Shanghai Zhongchen digital technology equipment Co., Ltd.; scanning electron microscope: jeol 5610lv, Japan Electronics Co., Ltd.
1.2 preparation of waterborne high gloss self drying alkyd coating
Add Tung linoleic acid, linoleic acid, benzoic acid, isophthalic acid, maleic anhydride, pentaerythritol, tk250, etc. into a four port flask, slowly raise the temperature to 150 ℃ for 1 h, 180 ℃ for 1 h, 210 ℃ for 1.5 h, and then 220 ℃ for 1.5 h. Finally, xylene was added and esterified at 210 ` 220 ℃ until the acid value was less than 7 mgKOH / g. Take out xylene, add mixed solvent of propylene glycol methyl ether and ethylene glycol butyl ether to reduce temperature, and mix with diluted material. Raise the temperature of the above-mentioned synthetic basic alkyd resin solution to 120 ` 125 ℃, add two-thirds of all acrylic acid mixed monomers drop evenly within 2 hours, and then add the remaining acrylic monomers and KH-570 mixture drop evenly within 1 hour. After dropping, keep the temperature at 120 ~ 125 ℃ for 1 hour, and then interval 1 H after adding initiator twice, cooling and discharging, the modified alkyd resin can be obtained. The addition of neutralizer to pH is 7 ~ 8.5, and diluted with deionized water to solid (42 + 2)%, that is, high gloss self drying waterborne acrylic modified alkyd resin emulsion.
A certain amount of resin emulsion was accurately dissolved in proper amount of deionized water, then wetting agent, dispersant and defoamer were added to the emulsion of waterborne acrylic modified alkyd resin, and then dispersed. After the dispersion is even, pigment and filler are added, and the resin matrix can completely wet the pigment and filler with high-speed dispersion. The whole system is grinded and dispersed by a sand mill until the fineness of the system is less than 30? M. Add leveling agent, thickener, etc. to the sanded paint, adjust the color and viscosity, and after filtration, it will be a high gloss and self drying waterborne acrylic modified alkyd paint.
1.3 performance test of resin paint film
The spraying method specified in GB / T 1727 general preparation method of paint film shall be adopted, and the thickness of paint film shall be measured according to GB / T 13452.2 determination of film thickness of paints and varnishes. The freeze-thaw stability shall be in accordance with GB / T 9268 determination of freeze-thaw resistance of latex paint. The nonvolatile content shall be in accordance with GB / T 1725 determination of nonvolatile content of paints, varnishes and plastics. The surface drying and dry time shall be in accordance with GB 1728 test method for drying time of paint film and putty film. Bending test shall be in accordance with GB / T 6742 bending test of paints and varnishes. Impact test shall be conducted in accordance with GB / T 1732 test method for impact resistance of paint film. Adhesion test shall be in accordance with GB / T 1731 test method for flexibility of paint film. Gloss test shall be carried out in accordance with GB / T 9754 paint and varnishes - Determination of 20 °, 60 ° and 85 ° specular gloss of paint films without metallic pigments. Hardness test GB / T 1730. Water resistance test GB / T 1733 test method for water resistance of paint film.
2 results and discussion
2.1 selection of raw materials for synthesis of waterborne alkyd resin
Pentaerythritol contains four primary hydroxyl groups, four primary hydroxyl groups have symmetrical structure. Compared with the same type of glycerin alkyd resin, the alkyd resin synthesized by pentaerythritol has compact structure, fast drying, high film hardness, good luster, light retention, water resistance and outdoor durability. Tung linoleic acid and linoleic acid contain a certain amount of double bonds, and the esterification activity is moderate, so they are suitable for preparing self drying resin. Maleic anhydride can increase the crosslinking degree of the paint film, improve the hardness and dryness, easily copolymerize with styrene and acrylate monomers, and has large steric resistance, which can effectively protect the ester bond in the resin and improve the hydrolysis stability of the resin. Benzoic acid, as a monobasic acid, can effectively regulate the functionality of alkyd resin. It can replace some fatty acids, increase the benzene ring unit, improve the water resistance, hardness and dryness of paint film. Styrene monomer can improve the film hardness and water resistance. Methacrylic acid, as a water-soluble monomer, reacts with neutralizer to form salt to realize the water-based resin. Lauryl methacrylate can enhance the water resistance and flexibility of the paint film. It can improve the hydrolysis resistance of resin and the water resistance and alkali resistance of paint film. γ - methacryloxypropyltrimethoxysilane (KH-570) is a modified monomer, which is helpful to improve the water resistance and oxidation resistance of the resin.
Initiator is the key material to control the polymerization rate, which affects the molecular weight, solid content and hardness of polymer. The activity of different monomers, decomposition temperature, half-life and initiation efficiency should be considered in the selection of initiator. The selection of initiator generally needs to consider two indexes: the half-life of initiator and the reaction temperature of 10 h half-life. Theoretically, the lower the temperature is, the higher the reaction activity is, the faster the decomposition is, and the faster the polymerization rate is. The main indexes of six common solution polymerization initiators are listed in Table 1. Based on the factors of solvent, monomer, product quality and safety, di tert butyl peroxide was selected as the initiator.
Table 1 10 h half-life temperature and common reaction temperature of common solution polymerization initiators
Initiator
10 h half-life temperature / (c
Common reaction temperature / (c
Azodiisobutyronitrile (AIBN)
Sixty-four
50~80
Benzoyl peroxide (BPO)
Seventy-two
80~110
Diisopropylperoxide (DCP)
One hundred and fifteen
110~140
Di tert butyl peroxide
One hundred and twenty-six
120~140
Tert butyl hydrogen peroxide
One hundred and twenty-one
120~140
Cumene hydrogen peroxide
One hundred and fifty-eight
130~160
The following four aspects should be considered in the selection of solvent: environmental protection of solvent; solvent solubility and water miscibility; boiling point of solvent; volatilization rate and storage stability. According to the above requirements, the mixed solvent of propylene glycol methyl ether and ethylene glycol butyl ether (the ratio of the two is 3:1) was selected as the solvent.
In this paper, the hydrophilic group - COOH was introduced into the film-forming material molecules, and the salt was neutralized by - COOH and neutralizer to achieve water solubility. The main function of neutralizer is to adjust and control the pH of paint and increase the water solubility of resin. When choosing neutralizer, not only the influence of neutralizer on the water solubility of resin, but also its volatility, odor and stability should be considered. At present, most of the neutralizers used in waterborne industrial coatings are ammonia water, diethylamine / triethylamine and N, N-Dimethylethanolamine. Ammonia water is volatile and has a strong smell. The neutralization value of diethylamine / triethylamine is unstable and toxic. Therefore, this work adopts strong alkalinity, low cost and moderate volatilization rate