JPS6123828B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to printing ink or paint (hereinafter collectively referred to as
The present invention relates to a method for producing a pigment composition useful for use in coating materials, particularly for aqueous coating materials, and more specifically relates to a method for producing a pigment composition that can be obtained by simple operations and has excellent gloss and the like when used in coating materials. Conventionally, methods for producing pigment compositions for coating materials include (1) adding a dry pigment to a vehicle such as a thermoplastic resin;
Plasticizers, solvents, etc. are kneaded together using two rolls, etc. to produce so-called color chips and color masterbatches. (2) The water content during pigment production is reduced to 50-80
Known methods include a flushing method in which an aqueous pigment suspension containing % by weight, so-called pigment press cake, is mixed with an oil vehicle, water is substituted for the vehicle, and the pigment is transferred into the vehicle. The method (1) described above requires a great deal of labor and time to grind the dried pigment, and is unsuitable for mass production and is uneconomical. Furthermore, the dried pigment caused problems such as scattering during work, which was undesirable from a sanitary control point of view. Method (2) is a method mainly used for lithographic printing inks, in which the pigment press cake is mixed with liquid varnish, thoroughly kneaded with a kneader, etc., and the separated water is removed to remove the pigment from the aqueous phase. This is a method of transitioning to a phase. Since this method does not involve a pigment drying process, agglomeration of the pigment can be prevented and a printing ink with good dispersibility can be obtained. Also known is a method in which a solution of a resin in an organic solvent is added to a pigment press cake to perform flushing. However, it has been difficult to apply these flushing methods to dry printing inks such as gravure printing inks or flexographic printing because the organic solvent is significantly scattered and evaporated. Flushing itself was difficult with water-based varnishes. The present invention is a method for producing a pigment composition that can be applied to quick-drying printing inks such as gravure printing or flexographic printing, and is particularly suitable for producing a pigment composition for aqueous coatings. That is, this is a method of heating and melting a pigment press cake and a thermoplastic resin that is solid at room temperature and is insoluble in water. The heat-melting method according to the present invention involves thermally softening the thermoplastic resin, which is solid at room temperature, stirring the highly viscous mixture with the pigment press cake, and using a powerful stirrer capable of dispersing and transferring the pigment into the thermoplastic resin. Use. Examples of such a stirrer include a kneader and the like. As the thermoplastic resin, a resin that is solid at room temperature and water-insoluble is used. With resin that is liquid at room temperature, strong force (shear) is not applied during heating, and the heating efficiency is poor. Furthermore, water-soluble resins are not preferred because flushing itself is difficult to proceed. However, the resin may be hydrophilic enough to be wetted by water. In the present invention, resins that can be water-solubilized by basic substances or acidic substances, or resins that are soluble in alcohol, are used in the aqueous coating agent, and are therefore preferably applied. In other words, it is difficult to perform flushing using water-soluble resins, and therefore, to produce water-based coatings, dry pigments had to be ground and kneaded. By applying the present invention to insoluble resins, aqueous coatings can be applied without using dry pigments. Examples of resins that can be made water-soluble by basic or acidic substances include styrene.
These include acrylic acid resin, acrylic ester-acrylic acid resin, styrene-maleic acid resin, rosin-modified maleic acid resin, and rosin-modified fumaric acid resin. Examples of resins that dissolve in alcohol include rosin-modified maleic acid resins, rosin-modified fumaric acid resins, polyamide resins, ketone resins, and polyester resins. These resins have a softening point
Preferably, the temperature is in the range of 70 to 140°C. In addition to the above-mentioned thermoplastic resins, it can also be applied to other organic solvent plastic resins having an appropriate softening point (within the above-mentioned range), such as maleic acid resins, ketone resins, rosins, petroleum resins, polyamide resins, and alkyd resins. I can do it. In addition, the softening point referred to in the present invention refers to the softening temperature measured by the ring and ball method softening point test (ASTM E28-58T) (the same applies hereinafter). If the softening point of the resin used is too low, the viscosity during heating and wading will be low, making it difficult to sludge and impeding the dispersibility of the pigment. When this happens, there is a tendency for the printability and physical properties of the coating film to deteriorate in the printing ink.
I didn't like it. On the other hand, if the softening point of the resin is too high, fluidity due to heat softening of the resin will not be achieved during heating and softening, making it difficult to disperse the pigment and making it impossible to obtain a glossy pigment composition when used in a coating material. . Furthermore, resins that change in quality due to heat, such as Sierrak, are not preferred because they may turn into gels. In the present invention, the surfactant added as necessary assists the dispersibility of the pigment, and various commonly known pigment dispersion aids can be used. For example, nonionic activators, anionic activators, and cationic activators such as polyoxyethylene nonylphenol ether, polyoxyethylene sorbitan monolaurate, sodium alkylbenzenesulfonate, and naphthalene sulfonic acid are used. The amount of these surfactants added is usually up to 10% by weight based on the thermoplastic resin.
If the amount added is too large, the printability of the coating material and the physical properties of the coating film tend to deteriorate, which is not preferable. Pigment press cake can be applied to both inorganic pigments and organic pigments, and the pigment content contained in the pigment press cake is preferably 20% by weight or more.If the pigment press cake contains a large amount of water, the required settling time will increase and efficiency will decrease. Therefore, it is undesirable. In the manufacturing method of the present invention, a required amount of thermoplastic resin that is solid at room temperature is placed in a stirrer such as a kneader, and while heating, about half or one-third of the pigment press cake is added and then mixed. . As the resin is softened by heat, the resin adsorbs onto the pigment in the pigment presscake and is replaced by water, resulting in an extremely highly viscous mixture. If adsorption of the resin to the pigment is insufficient, it can be completed by adding a surfactant in an amount of up to 10% by weight based on the resin content. Furthermore, when adding the remaining amount of pigment press cake once or in several batches while being careful not to reduce the stirring efficiency and continuing heating and mixing, the resin will be adsorbed to the pigment and a large amount of water will be separated. It's coming. 〓It is desirable to drain the water during the mixing process. The above manufacturing method is one example of a desirable method, and the method is not limited to the above method. The heating temperature during heating needs to be adjusted depending on the softening point of the resin used. If the resin has a low softening point, heating at too high a temperature will lower the viscosity too much and reduce the efficiency. . Therefore, for resins with low softening points, at relatively low temperatures,
For resins with a high softening point, it is preferable to soften at a relatively high temperature. 20 below the softening point of thermoplastic resin
It is preferable to heat the mixture at a temperature between 200°C and 200°C. At temperatures considerably lower than the softening point, softening is difficult and requires a great deal of effort and time. Furthermore, at temperatures above 200°C, the fluidity of the resin becomes too large due to thermal softening, and shearing cannot be applied. Furthermore, it has adverse effects such as deterioration of the resin or pigment. In the present invention, a particularly preferred method is one in which heating and heating is carried out at a temperature from 20° C. lower than the softening point of the resin to the softening point, and efficient heating can be carried out. Note that depending on the resin, the melt viscosity may be too high at a temperature near the softening point, but in this case, heating and softening is performed at a temperature higher than the softening point. For example, in the case of a styrene-maleic acid resin having a softening point of 120°C, a pigment composition can be obtained extremely efficiently by heating and heating to 110°C. Also, water is separated during heating and curing, but this water gradually evaporates. In order to promote this evaporation, it was desirable to maintain the temperature during heating and sintering at 100°C or higher. By heating and heating for 1 to 2 hours, the amount of water in the composition becomes extremely small, the adsorption of the resin to the pigment is sufficient, and the desired pigment composition can be obtained.
Next, the temperature of this pigment composition is rapidly lowered to room temperature, the mixture is continued to be stirred, and the pigment composition is pulverized to a particle size of several millimeters in diameter, and then taken out. Various ratios of resin and pigment can be applied to the pigment composition according to the present invention, but the higher the pigment content, the higher the versatility and the higher the utility value when later applied to a coating material. If the resin content is too low, the viscosity and fluidity during mixing will be poor, the amount of resin adsorbed to the pigment will be small, and it will be difficult to sufficiently improve the gloss of the coating, and the resulting pigment composition will usually be poor. It is desirable that the pigment content of the product is in the range of 50 to 90% by weight. The production method of the present invention is a method that can be applied to quick-drying printing inks such as gravure printing inks and flexographic printing inks, and is particularly applicable to aqueous coating materials, and it is a method that is applicable to aqueous coating materials and does not involve a pigment aggregation step (drying). Therefore, when used in coating materials, this method can omit or reduce the dispersion process using shearing force, impact, etc. such as roll milling and ball milling. Moreover, there is almost no scattering of components other than water during the work, making the work extremely environmentally hygienic, and the scattering of dry pigments, which is a drawback of conventional methods, can be prevented. Since the obtained pigment composition is granular, it is extremely easy to handle, has a large pigment content, and is extremely brittle.
It also swells and dissolves easily in solvents. Therefore,
It is easily dispersible and can be made into a coating material for printing ink etc. using Teisolver or other general agitators, and is extremely glossy compared to coating materials using pigment compositions obtained by conventional methods. agent is obtained. Furthermore, although a few percent of water may remain in the pigment composition, this pigment composition can be used to produce not only aqueous coatings but also alcoholic coatings and the like without causing any problems. Next, the present invention will be explained based on examples. In the examples, "parts" and "%" refer to "parts by weight", respectively.
Indicates "% by weight". Example 1 150 parts of Hyros T-21 (styrene-maleic acid resin, softening point 120°C, manufactured by Hoshi Kogaku) was placed in a kneader, and while heating to 110°C, Lyonol Yellow was added.
GGT press cake (benzine yellow, pigment content)
37%, manufactured by Toyo Ink Manufacturing Co., Ltd.) was added and 300 parts were mixed. After 10 minutes, as the resin heat softens, some of the water evaporates, and the resin adsorbs to the pigment in the pigment press cake, replacing it with water, separating the water, and causing layer transition. The viscosity gradually increased. After a further 15 minutes, 300 parts of the above press cake were added, followed by heating and sintering. After 25 minutes, water was separated, layer transition occurred again, and the mixture became highly viscous after 30 minutes. Further, 300 parts of the above press cake was added and then heated and heated. As the residual water evaporated, the mixture became extremely viscous after 1 hour, and the dispersion was completed. Next, rapid cooling was started (to room temperature), and then pulverization was carried out, and when the particle size reached an appropriate particle size of several millimeters in diameter, this pigment composition (referred to as pigment composition A) was taken out and worked. Completed. For comparison, the heating temperature was 90℃ and 220℃.
When the other conditions were the same, it was found that it was virtually impossible to sum at 90°C, and at 220°C
In this case, sufficient shearing was not applied, resulting in not only poor dispersion but also odor due to deterioration of the resin. Next, a water-based printing ink was prepared using this pigment composition A.

[Table] For 75 parts of composition (1) obtained by dissolving and dispersing the above composition using a dissolver,

[Table] 〓

Claims (1)

[Claims] 1. A pigment composition characterized in that a thermoplastic resin that is solid at room temperature and is insoluble in water and a pigment press cake are heated and mixed, with the addition of a surfactant if necessary. How things are manufactured. 2. The method for producing a pigment composition according to claim 1, wherein the thermoplastic resin is a resin that can be made water-soluble by either a basic substance or an acidic substance. 3. The method for producing a pigment composition according to claim 1, wherein the thermoplastic resin is a resin that dissolves in alcohol. 4. The method for producing a pigment composition according to any one of claims 1 to 3, wherein the heating and curing is carried out at a temperature between 20° C. lower than the softening point of the thermoplastic resin and the softening point.