In our packaging and printing process, we occasionally encounter streaks of printing or light color phenomenon. This kind of failure, which is called no ink-removing and ink-dropping roller, is caused by the swelling of the color and filler of the packaging printing ink system. Causes the overall gelation of the ink.
Explain from a theoretical point of view: the yield value of the ink is too high, and the ink is too short to become a cheese. From a practical point of view, too many pigments and fillers in the ink cause the ink to gel or cause water to enter the ink system during the storage process and cause partial flocculation.
For a long time, people have used continuous stirring of the ink in the ink fountain for bloating or gelatinization, or installed a stirrer in the ink fountain, and also put an iron bar on the ink to push the ink to the ink fountain roller to keep the flow of the packaging printing ink. Sex. Most operators prefer to use medium- or high-viscosity varnish or thinner to adjust the ink (but this must be used with it, otherwise it will continue to swell or gel). Some manufacturers, however, dumped the ink and replaced it with ink with good fluidity and resistance to water. Throughout this failure, the author has conducted a cursory discussion of this issue around this issue and discussed new ways to eliminate the failure and communicate with colleagues in the packaging and printing industry.
First, the concept of gelation of the ink and the acid and alkali The problem of gelation of the packaging printing ink in the early ink (oxidative drying type and osmotic drying type) ink is often encountered in the solvent type (volatile drying type) and Occasionally encountered in water-based ink. We know that the cause of gelation is very complicated (including the process flow of ink manufacturing, such as the addition and subsequent addition of driers). With the development of science and technology and the use of new materials, we have strengthened the study of scientific theories and the control of the quality of ink component materials. When the composition of the ink changes, various problems are effectively controlled. But generally, after a failure occurs, operators often do nothing. Caused by the phenomenon of ink gelation, I think there are the following six reasons:
1. The molecular weight of the ink system is too large (viscosity is too high);
2. There are too many solid components (even small viscosity resin binders are no exception);
3 ink system acid value is too high;
4. Pigments, fillers with alkaline;
5. Too much desiccant content or improper order of addition (eg two results before and after ink production);
6. The solvent of the ink system is especially too much dry fast solvent.
From the above six reasons, it can be found that the first two belong to the category of physics and the latter four belong to the category of chemistry (reaction). When we explore around the last four reasons, we will also find that the temperature of the dispersion process is too high, the volatilization of the solvent, and improper use of auxiliary additives may also cause the ink to gelate. In the fifth issue of the "Guangdong Packaging" magazine in 1998, the author's "Study of green packaging printing inks" analyzed the molecular weight of only 330 rosin resin in the production of solvent-based flexible fast-dry packaging printing The gelation phenomenon occurred in the ink, and the failure of the stacking and difficult to ink, described the advantages and disadvantages of the strong acid pigment carbon black pigment and rosin acid value. This is sufficient to indicate that the acid is electrophilic and is an electron acceptor (proton donor); the base is nucleophilic and is an electron donor (proton acceptor). There are also so-called amphoteric solvents and resins (both proton donors and proton acceptors of water, alcohols, carboxylic acids, and nitrocellulose, etc.), followed by an aliphatic hydrocarbon solvent that does not form hydrogen bonds, and The pigments, amphoteric pigments, etc. are all related to the gelation of the ink. It is often said that when the acid-base characteristics of pigments are not compatible with the acid-base characteristics of the binders, we can use a variety of resins and pigments, fillers to adapt the acid-base characteristics, or choose the appropriate solvent to make the acid and alkali The characteristics are improved, which is a regular remedy.
When we explore the chemical (reaction) category, we find that when the stoichiometric concentration reaches a certain value (strictly speaking, a very narrow concentration range), various macroscopic properties will suddenly change. From the microscopic point of view, the active molecules of the ink system begin to associate and form aggregates of unequal size. Such aggregates are called micelles or micelles, also known as associative colloids. An important characteristic of micelles is the result of their solubilizing action, which greatly increases the solubility of the originally insoluble or sparingly soluble substances - commonly known as bloating. This speeds up the chemical reaction. The mechanism of the reaction is likely to have a close relationship with the binder, especially the pigment dispersion process.
Second, eliminate swelling, to avoid the effective way of gel In addition to the reasons mentioned above, the driers in the ink system can also directly affect the viscosity of the ink in the storage process, increased growth and pigment, filler precipitation. For example, a highly viscous alkyd resin is ground with a basic pigment zinc oxide and driers to promote gelation and swell of the ink during storage. This is due to the reaction of free fatty acids and basic pigments during thermal processing. Therefore, in the production of inks using high viscosity ink materials, lead, cobalt, and manganese driers should not be added during the grinding process. However, after adding 1% benzoic acid, the tendency to swell can be reduced. Another drawback of driers is that they can accelerate pigment precipitation during storage. For example, when titanium dioxide is used to make inks, zinc naphthenate is added during grinding, and the pigments tend to precipitate and form a lump.
In recent years, people have proposed such remedial measures in terms of swelling, gelation, and sedimentation around packaging printing inks. The solution to this problem is often caused by the appearance of faults. This method of passive operation not only increases the production costs and delays of the packaging and printing manufacturers, but also brings with it certain processing difficulties. The phenomenon of gelation, thickening and blocking of the ink system is related to the reaction of the salt-based pigment with a higher acid value or a binder containing free fatty acids to soap. The binder itself agglutinates, the ink system absorbs moisture, the pigment content is too high, the binder and the pigment used are not balanced (inappropriate), the adjuvant of the binder and grease is poorly miscible, and the polymer binder is acid Absorption of dissolved structures by pigments can lead to gelation of the ink. The general remedies are nothing more than the following four methods:
1. When it is too thick or the gelation occurs due to the high degree of polymerization of the linking material, dilute with aliphatic hydrocarbons, esters, and ketones.
2. React to gelatinized inks. Rosin is dissolved in linoleic oil and its high acid content is used to relieve it.
3. Add naphthalic acid metal salts to the packaging printing ink.
4. The ink needs to add inorganic salt, can control the gel.
By analyzing the ink formulation structure and combining many years of practical experience, the author believes that the improved phosphate ester titanate coupling agent produced by Yizheng Tianyang Chemical Factory (National Inspection-Exempt Product) not only has excellent dispersion properties for pigments, but also To make swollen, gelatinized packaging printing ink "rejuvenated." For example, in the printing process, only 3% to 5% of the anti-expansion breaker needs to be added to the swelled ink, so that the above failure can be controlled and the original structure and viscosity of the ink can be restored. According to the characteristics of anti-expansion breaker produced by Yizheng Tianyang Chemical Plant, we only need to add 1.5% to 2.5% anti-expansion breaker in pigments and fillers to avoid packaging printing. Swelling and gelatinization. It is also possible to use toluene, xylene in a ratio of 1:1 to dilute with the product first, and then add the ink in the ink to grind and disperse together, which can not only greatly improve the dispersibility of the pigment, but also prevent the packaging printing ink from being produced and stored. In the printing process, due to swelling, gelation, precipitation, resulting in streaks or color fading. At the same time, the degree of branching of the ink can be greatly increased to increase the attachment fastness of the ink film, and the baking temperature and the blowing amount of the printing ink or the volatile drying type (solvent type) printing ink can be reduced, thereby effectively promoting the normal printing of the packaging printing ink. Printing fluidity. (Liu Jiaju)
Explain from a theoretical point of view: the yield value of the ink is too high, and the ink is too short to become a cheese. From a practical point of view, too many pigments and fillers in the ink cause the ink to gel or cause water to enter the ink system during the storage process and cause partial flocculation.
For a long time, people have used continuous stirring of the ink in the ink fountain for bloating or gelatinization, or installed a stirrer in the ink fountain, and also put an iron bar on the ink to push the ink to the ink fountain roller to keep the flow of the packaging printing ink. Sex. Most operators prefer to use medium- or high-viscosity varnish or thinner to adjust the ink (but this must be used with it, otherwise it will continue to swell or gel). Some manufacturers, however, dumped the ink and replaced it with ink with good fluidity and resistance to water. Throughout this failure, the author has conducted a cursory discussion of this issue around this issue and discussed new ways to eliminate the failure and communicate with colleagues in the packaging and printing industry.
First, the concept of gelation of the ink and the acid and alkali The problem of gelation of the packaging printing ink in the early ink (oxidative drying type and osmotic drying type) ink is often encountered in the solvent type (volatile drying type) and Occasionally encountered in water-based ink. We know that the cause of gelation is very complicated (including the process flow of ink manufacturing, such as the addition and subsequent addition of driers). With the development of science and technology and the use of new materials, we have strengthened the study of scientific theories and the control of the quality of ink component materials. When the composition of the ink changes, various problems are effectively controlled. But generally, after a failure occurs, operators often do nothing. Caused by the phenomenon of ink gelation, I think there are the following six reasons:
1. The molecular weight of the ink system is too large (viscosity is too high);
2. There are too many solid components (even small viscosity resin binders are no exception);
3 ink system acid value is too high;
4. Pigments, fillers with alkaline;
5. Too much desiccant content or improper order of addition (eg two results before and after ink production);
6. The solvent of the ink system is especially too much dry fast solvent.
From the above six reasons, it can be found that the first two belong to the category of physics and the latter four belong to the category of chemistry (reaction). When we explore around the last four reasons, we will also find that the temperature of the dispersion process is too high, the volatilization of the solvent, and improper use of auxiliary additives may also cause the ink to gelate. In the fifth issue of the "Guangdong Packaging" magazine in 1998, the author's "Study of green packaging printing inks" analyzed the molecular weight of only 330 rosin resin in the production of solvent-based flexible fast-dry packaging printing The gelation phenomenon occurred in the ink, and the failure of the stacking and difficult to ink, described the advantages and disadvantages of the strong acid pigment carbon black pigment and rosin acid value. This is sufficient to indicate that the acid is electrophilic and is an electron acceptor (proton donor); the base is nucleophilic and is an electron donor (proton acceptor). There are also so-called amphoteric solvents and resins (both proton donors and proton acceptors of water, alcohols, carboxylic acids, and nitrocellulose, etc.), followed by an aliphatic hydrocarbon solvent that does not form hydrogen bonds, and The pigments, amphoteric pigments, etc. are all related to the gelation of the ink. It is often said that when the acid-base characteristics of pigments are not compatible with the acid-base characteristics of the binders, we can use a variety of resins and pigments, fillers to adapt the acid-base characteristics, or choose the appropriate solvent to make the acid and alkali The characteristics are improved, which is a regular remedy.
When we explore the chemical (reaction) category, we find that when the stoichiometric concentration reaches a certain value (strictly speaking, a very narrow concentration range), various macroscopic properties will suddenly change. From the microscopic point of view, the active molecules of the ink system begin to associate and form aggregates of unequal size. Such aggregates are called micelles or micelles, also known as associative colloids. An important characteristic of micelles is the result of their solubilizing action, which greatly increases the solubility of the originally insoluble or sparingly soluble substances - commonly known as bloating. This speeds up the chemical reaction. The mechanism of the reaction is likely to have a close relationship with the binder, especially the pigment dispersion process.
Second, eliminate swelling, to avoid the effective way of gel In addition to the reasons mentioned above, the driers in the ink system can also directly affect the viscosity of the ink in the storage process, increased growth and pigment, filler precipitation. For example, a highly viscous alkyd resin is ground with a basic pigment zinc oxide and driers to promote gelation and swell of the ink during storage. This is due to the reaction of free fatty acids and basic pigments during thermal processing. Therefore, in the production of inks using high viscosity ink materials, lead, cobalt, and manganese driers should not be added during the grinding process. However, after adding 1% benzoic acid, the tendency to swell can be reduced. Another drawback of driers is that they can accelerate pigment precipitation during storage. For example, when titanium dioxide is used to make inks, zinc naphthenate is added during grinding, and the pigments tend to precipitate and form a lump.
In recent years, people have proposed such remedial measures in terms of swelling, gelation, and sedimentation around packaging printing inks. The solution to this problem is often caused by the appearance of faults. This method of passive operation not only increases the production costs and delays of the packaging and printing manufacturers, but also brings with it certain processing difficulties. The phenomenon of gelation, thickening and blocking of the ink system is related to the reaction of the salt-based pigment with a higher acid value or a binder containing free fatty acids to soap. The binder itself agglutinates, the ink system absorbs moisture, the pigment content is too high, the binder and the pigment used are not balanced (inappropriate), the adjuvant of the binder and grease is poorly miscible, and the polymer binder is acid Absorption of dissolved structures by pigments can lead to gelation of the ink. The general remedies are nothing more than the following four methods:
1. When it is too thick or the gelation occurs due to the high degree of polymerization of the linking material, dilute with aliphatic hydrocarbons, esters, and ketones.
2. React to gelatinized inks. Rosin is dissolved in linoleic oil and its high acid content is used to relieve it.
3. Add naphthalic acid metal salts to the packaging printing ink.
4. The ink needs to add inorganic salt, can control the gel.
By analyzing the ink formulation structure and combining many years of practical experience, the author believes that the improved phosphate ester titanate coupling agent produced by Yizheng Tianyang Chemical Factory (National Inspection-Exempt Product) not only has excellent dispersion properties for pigments, but also To make swollen, gelatinized packaging printing ink "rejuvenated." For example, in the printing process, only 3% to 5% of the anti-expansion breaker needs to be added to the swelled ink, so that the above failure can be controlled and the original structure and viscosity of the ink can be restored. According to the characteristics of anti-expansion breaker produced by Yizheng Tianyang Chemical Plant, we only need to add 1.5% to 2.5% anti-expansion breaker in pigments and fillers to avoid packaging printing. Swelling and gelatinization. It is also possible to use toluene, xylene in a ratio of 1:1 to dilute with the product first, and then add the ink in the ink to grind and disperse together, which can not only greatly improve the dispersibility of the pigment, but also prevent the packaging printing ink from being produced and stored. In the printing process, due to swelling, gelation, precipitation, resulting in streaks or color fading. At the same time, the degree of branching of the ink can be greatly increased to increase the attachment fastness of the ink film, and the baking temperature and the blowing amount of the printing ink or the volatile drying type (solvent type) printing ink can be reduced, thereby effectively promoting the normal printing of the packaging printing ink. Printing fluidity. (Liu Jiaju)
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