Synthesis of Rosin Modified Phenolic Resin for Lithographic Offset Printing Ink

Rosin modified phenolic resin is mainly composed of rosin, alkyl phenol, polyhydric alcohol and formaldehyde. After certain condensation polymerization reaction, high molecular weight and low acid value resin are obtained. Because of its unique honeycomb structure characteristics, it can be well wetted with pigments, and can react with the gelling agent to obtain a certain viscoelastic binder material and is widely used in lithographic inks. The experimental results show that the performance of the resin depends to a great extent on the type of alkyl phenol. The phenols used in the rosin-modified phenolic resins are t-butyl phenol, octyl phenol, nonyl phenol, and dodecyl phenol. There is also a poorly oil-soluble phenol, bisphenol A. The use of high-grade alkyl phenol makes the resin have good solubility, high viscosity and large molecular weight, and can basically meet the needs of high-speed printing and large-scale use of aromatic-free mineral oil. The length and the degree of branching of the alkylphenol have a great influence on the reactivity of the condensate, the softening point and the degree of accommodation of the rosin-modified resin.

one. Synthetic process of rosin modified phenolic resin

Rosin modified phenolic resin is still characterized by traditional synthetic processes. The one-step method is characterized by directly reacting phenol, aldehyde and other raw materials with rosin and directly reacting. The process form is simple, but the following steps require higher temperature and other control requirements; the two-step method is characterized by pre-synthesizing phenolic aldehyde intermediates, and then with rosin. The system reacts to form a resin with low acid value, high softening point, and solubility of a certain molecular weight and a certain mineral oil solvent through each specific reaction stage.

1. One-step process

One-step reaction principle:

1 Resol synthesis:

An alkylphenol is added to the molten rosin, and the paraformaldehyde is present as a particulate in the system, which is subsequently decomposed into the monomeric formaldehyde and polycondensed with the alkylphenol.

Formation of 2-methyl hydrazine

During dehydration, the activity of hydroxymethyl groups in the system increases rapidly during the process of temperature increase, dehydration occurs within the hydroxymethyl group, condensation and etherification reaction between methylol groups, and various phenolic aldehydes with different degrees of polymerization are formed. Condensate.

3 Addition of rosin with methine hydrazine and maleic anhydride

Maleic anhydride was added at 180°C, utilizing the unsaturated double bond of maleic anhydride and the double bond addition in rosin acid. Simultaneous Diels-Alder addition reaction of methine oxime and rosin acid resulted in the formation of maleic anhydride. Benzoinhydrofuran compounds.

4 Polyester Esterification

The presence of a large number of carboxyl groups in the system can destroy the balance of the system and cause instability of the resin. Therefore, we added polyols to reduce the acid value of the system by utilizing the hydroxylation of the polyol and the carboxyl group in the system. At the same time, through the esterification of polyols, high polymers suitable for offset printing inks have been formed.

2. Two-step process

The two-step reaction principle:

1 Under the action of special catalysts, formaldehyde forms a large number of reactive hydroxymethyl-containing resol oligomers in the solution of alkyl phenols. Since the system does not have the inhibitory effect of rosin acid, it is possible to synthesize condensates of more than 5 phenolic building blocks.

2 Polyesters and rosins are esterified at high temperatures and the desired acid values ​​can be reached relatively quickly under the action of alkaline catalysts.

3 In the well-reacted rosin polyol ester, the synthetic resole phenolic resin was slowly added dropwise to control the rate of dropwise addition and temperature, and the dropwise addition was completed. Dehydration is heated up to form the desired resin.

The advantage of the one-step process is that the waste is removed in the form of steam and is easily handled by environmental protection. However, the phenol condensation reaction occurring in the molten rosin is liable to occur due to high reaction temperature and uneven dissolution resulting in many side reactions, thus the detection and quality of the condensation product. Adjustment is difficult to control and it is not easy to obtain a stable resin product. The advantage of the two-step method is that the phenolic condensation oligomers with relatively stable structure and composition can be obtained, the reaction stages can be easily monitored, and the product quality is also relatively stable. The disadvantage is that traditional phenolic syrup condensates must be acid-neutralized and can react with rosin after being rinsed with a large amount of water for several times to remove salts, thereby generating a large amount of phenol-containing waste water, causing great damage to the environment, and extremely time-consuming.

One-step and two-step processes are problems that have long been the focus of ink manufacturers. Recently, however, the successful development of a process for synthesizing phenolic condensates with the no-clean process has effectively promoted the rationalization of the two-step synthesis route.

Here is the difference between the two-step method of no-clean process and the traditional water-wash process:
The main differences between the traditional washing process and the no-cleaning process

two. Development of resin binders

Ink linking materials are still dominated by rosin-modified phenolic resins. In view of the large number of patent documents published in recent years, the main work is still focused on how to select alkyl phenols, use of fatty acid or fatty acid modified alkyd resins and various changes. Sex craftsmanship. In addition to adapting to the tendency of ink solvents to dearomatize, general lithographic inks contain 10% to 30% of aromatic solvents, aromatics to 1% or less, and their aniline points will rise above 10°C, which will greatly reduce the ability to dissolve the resin and make inks. The fluidity and the deterioration of the gloss must be adapted to the more soluble resins. Satisfying the need to produce lithographic inks using the squeezed water process, squeezing the lithographic inks using the squeezed water process is considered to be the most efficient, better quality and lower cost production method. The wet pigments and binders are kneaded and dewatered at a certain temperature. The pigment particles can be directly dispersed into the ink binder. According to the size of the pigment particles and the surface treatment conditions, it is necessary to control the binder with the proper surface tension and water resistance performance, from low polarity, high solubility, high molecular weight rosin. The connection material made of the modified phenolic resin is suitable for the manufacturing process of the squeezing ink.

The development of ink is inseparable from the development of resin, adapting to the development of the printing industry, stabilizing the quality of resin products, improving the production process, and developing new products will be the focus of resin development.

(Author/Shanghai Peony Ink Co., Ltd. Chen Bin Shen Xijun)

Guangdong Packaging (4th Issue, 2005)