Question and answer 6 of the hottest plastic packa

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Q & A on plastic packaging printing and composite technology (VI)

51. How does the polymer swell and dissolve

the dissolution of polymer has two stages: swelling first and then dissolution. The cooperation with parts manufacturers and automobile engine manufacturers is getting closer and closer. Because there are a lot of voids between the chain segments of polymer molecules, when it comes into contact with solvents, solvent molecules can penetrate, "First, the volume of the polymer is increased, so that the chain is pushed away, and the gap between the chain segments is increased. The solvent continues to penetrate, so that more molecules are solvated. The distance between the chain segments is getting larger and larger, and finally the whole long chain of the macromolecule is separated from each other and enters the solvent to complete the dissolution process."

52. What is the role of solvents in plastics and composites

solvent is an important part of gravure ink and flexographic ink, and it is also an indispensable material in plastic film composite adhesive

solvent has the ability to dissolve substances and volatilize itself. Its volatilization speed is an important factor that determines the ink layer drying of volatile ink and affects the printing quality. If the solvent volatilizes slowly, the printing reproducibility will be poor. However, in rotary printing, if the solvent is not completely volatilized, the ink layer is easy to adhere during printing. On the contrary, if the solvent in the ink volatilizes too fast in the printing process, the printing color will be light and stick to the roller. Therefore, the choice of solvent is very important

53. How many solvents are commonly used in gravure and flexo printing

common solvents for gravure and flexo printing are:

hydrocarbons: toluene, etc

esters: methyl acetate, ethyl acetate, n-butyl acetate, etc

ketones: acetone, methyl ethyl ketone, etc

alcohols: isopropanol, isobutanol, n-butanol, ethanol, etc

54. What are isopropanol and its properties

isopropanol (CH3) 2choh, colorless transparent. It smells like ethanol. Specific gravity 0.7851 (20/4 °) ℃. The melting point is 117.3 ℃. Distillate at boiling point of 78.10 ℃. It can dissolve many organic compounds and some inorganic substances. It can burn. Ethanol evaporation and air mixing can form explosives, explosion limit 3 0% (volume). It is widely used. Such as thinner for water-based plastic ink. In summer, it can be used as a mixed solvent for polyamide gravure printing ink

55. What is ethanol and its properties

ethanol CH3CH2OH, commonly known as alcohol. Colorless, transparent, volatile and flammable liquid. It smells of wine. The specific gravity is 0.7893 (20/4 °). The melting point is 117.3 ℃. Boiling point 78.4 ℃. Soluble in water, methanol, ether, chloroform, etc. Hygroscopic. It can form azeotropic mixture with water. Ordinary alcohol contains 95.57% ethanol by weight, which is distilled at 78.10 ℃. It can dissolve many organic compounds and some inorganic substances. It can burn. The mixture of ethanol evaporation and air can form explosives, with an explosion limit of 3.5 ~ 18.0% (volume). It is widely used. Such as thinner for water-based plastic ink. In summer, it can be used as a mixed solvent for polyamide gravure printing ink

56. What is butanol? What is its use in plastic printing

butanol c4h9oh has four isomers. The important ones are n-butanol and isobutanol. It can be used as a slow drying agent for plastic gravure printing ink

(1) n-butanol CH3 (CH2) 2ch2oh, colorless liquid with wine smell. Specific gravity 0.8098 (20/4 °). Boiling point 117.7 °. Freezing point - 89.0 °. Soluble in water, miscible with ethanol and ether. Vapor and air form explosive mixture, explosion limit 3 2% (volume), used as solvent and dehydrating agent

(2) isobutanol (CH3) 2chch2oh, colorless transparent liquid. It has a special smell. Specific gravity 0.806 (15 ℃). Melting point -108 ℃. Boiling point 107 ℃. Soluble in water, ethanol and acetic acid. The vapor and air form an explosive mixture, and the lower explosion limit is 2.4% (volume). Used in solvents, plasticizers and antioxidants

57. What solvent is methyl ethyl ketone commonly used in the solvent formula of gravure printing ink? What are its characteristics

methyl ethyl ketone is the abbreviation of methyl (base) ethyl (base) ketone ch3coc2h5. Also known as butanone. Colorless flammable liquid. It is poisonous and can cause blindness after drinking. Specific gravity 0.7915 (20/4 °) melting point 97.8 ℃. Boiling point 64.65 ℃. It is miscible with water and various organic solvents

58. How to choose the solvent of plastic printing ink

plastic printing ink usually needs to consider the following factors: (1) the speed of the printing machine; (2) Structure of drying system; (3) Characteristics of printing materials; (4) Indoor temperature and relative humidity; (5) The type of printing plate, the solvent cannot corrode the printing plate; (6) It should have good solubility, free of any mechanical impurities and free acids, bases and moisture; It has good evaporation rate (commonly known as dryness). These requirements are the key indicators for the selection of ink solvents. (7) The solvent cannot react with the components of the ink; (8) The odor is small and the toxicity is small (the ideal solvent is non-toxic and odorless), the volatile gas should meet the requirements of environmental protection, and it should reach the actual non-toxic level when used in food packaging; After printing, the product shall not have the odor of residual solvent. (9) Stable storage, no decomposition, no moisture absorption; (10) Low price and abundant supply

59. What are the factors affecting ink volatilization

(1) ratio of mixed solvents. The volatilization speed of mixed solvents is restricted by the solvent molecules, and its volatilization speed is not the average value of their volatilization speed

(2) effect of resin. The solvent volatilization in the ink is more complex. When the resin is dissolved in the dry solvent, the two substance molecules are closely combined with each other (the role of the solvent). At this time, the volatilization speed of the solvent is lower than that of the solvent itself. For liquid inks with a certain viscosity, the volatilization of the attached solvent during the drying process, the resin content is increasing, and the volatilization rate of the solvent also slows down

(3) condition of pigment particles. When making ink, when adding pigments, fillers and other materials, the evaporation rate of the solvent will be greatly reduced. The finer the pigment particles and the larger the surface area, the slower the evaporation rate of the solvent

(4) influence of ambient temperature and humidity. The higher the room temperature of the printing workshop is, the faster the solvent volatilizes, and vice versa. Indoor air circulation, solvent volatilization is fast, if indoor is relatively blocked, solvent volatilization is slow. Therefore, high-speed gravure or flexo printing machines are equipped with heating and exhaust devices. Conditional plastic printing plants should be equipped with solvent recovery devices, which can not only solve the problem of drying the solvent volatile ink layer, but also solve the problem of sewage discharge, which is conducive to the physical and mental health of employees

63. What is the difference between the viscosity and viscosity of ink

viscosity is also called viscosity (hysteresis) or internal friction. A characteristic of a fluid (including liquid and gas) that prevents its relative flow. When a liquid is stirred, its flow rate is directly proportional to the applied force (shear stress) = constant x shear rate

the viscosity is mainly determined by the composition of the ink. If the viscosity of the binder in the ink is high, the viscosity of the ink is also high; In addition, the solvent content is large and the viscosity is small; High pigment content and viscosity;. The higher the temperature in the workshop, the lower the meal degree, and so on

the viscosity of ink is also called adhesion. It refers to the ink in the printing process, between the ink roll and the ink roll, between the ink roll and the printing plate, between the printing plate and the printed object, at the moment of the separation of the ink film, a force against the separation of the ink layer is generated in the ink molecule, which is called the adhesion of the ink

the low viscosity of the ink will make the binder penetrate into the paper too much, making the printed matter lack luster and affecting the fixation of the imprint. From the perspective of printing plastic, the thin layer formed is too thin, resulting in the weak color and gloss of the printed products. If the ink viscosity is too high. Printing paper and plastic will cause poor ink transfer, uneven ink, and even block the plate line. Therefore, the viscosity of the ink must be moderate. Inking oil is used to adjust the viscosity of printing paper. When it is necessary to increase the viscosity of the ink, add No. 0 inking oil, and when it is necessary to reduce the viscosity, add No. 6 inking oil. Plastic film gravure printing and flexographic printing, color plastic film fast drying thinner and slow drying thinner to adjust ink viscosity. Viscosity is related to printing speed. The higher the printing speed is, the lower the viscosity is. Flexible relief ink is more viscous than gravure ink. Gravure ink pigment content%, viscosity (poise) 0; Soft ink pigment content%, viscosity (poise)

64. What are the contents of conventional ink determination

(1) color of ink; (2) Viscosity of ink; (3) The absolute viscosity of ink, measured in poise or centipoise. It can be calculated by comparing the outflow time of the fluid with falling ball viscosity in the capillary viscometer; (4) Adhesion of ink; (5) Dryness of ink; (6) Coloring power of ink; (7) Fineness of ink; (8) Fluidity of ink; (9) Acid and alkali resistance of ink. Determination of ethanol resistance

65. How are plastic inks classified and named

There are many kinds of plastic inks, and there is no unified regulation on their classification and nomenclature. Generally, there are the following:

(1) according to the type of printing plate, plastic ink is divided into: Plastic letterpress printing ink. Plastic intaglio ink, plastic flexo ink and plastic wire (hole) ink

(2) according to the drying form of plastic ink, it can be divided into oxidation drying ink, volatile drying ink and double liquid melon composite ink

(3) it can be divided into polyamide type, acrylic type and rubber type inks according to the used connecting materials

(4) according to the different solvents used, it can be divided into. Mixed solvent type, water type, benzene type, etc

66. Why can't different kinds of plastic inks be mixed

plastic inks generally vary according to the speed of the printing machine, the characteristics of the printed materials and the process used. For example, plastic lead printing and plastic flexible relief printing, although both are embossed, the former printing speed is very slow and requires oxidized conjunctive ink, while the latter printing speed is fast and requires volatile dry ink, which must not be used mutually. For another example, plastic flexible relief printing and plastic intaglio printing are both rotary printing, with similar printing speed, and both use volatile ink. However, the former is a resin version, so it is necessary to consider whether the solvent in the ink has corrosive effect on the printing plate. The latter is a metal plate, so there is no need to consider the influence of solvent on the printing plate. In addition, the transmission system of the tension machine used earlier in the market of commonly used packaging materials includes the reducer and the polyethylene, polypropylene, polyester, cellophane, etc. in the ordinary belt materials are all plastic transparent films, but their printability is not the same, and they also need the corresponding ink

67. What printability should plastic gravure inks have

plastic film gravure printing ink is the thinnest, the least viscous, like spray paint, contains many solvents, and is a colloidal fluid with good fluidity and transferability. The ink manufacturer is designed according to the following conditions

(1) the printing speed of gravure printing machine is very fast. The printing speed of domestic satellite gravure rotary printing machine and split gravure printing machine is m/min, and the printing speed of imported split gravure rotary printing machine can be as high as m/min. In addition, the concave depth of gravure is generally um, and the deepest can reach 40um. The ink transfer rate on the printing plate is generally% and the ink layer thickness on the substrate is um. Such a fast printing and the concave depth of the printing plate can not be achieved by oxidation conjunctiva alone. Therefore, volatile drying ink should be used to fill and coat the intaglio lines by its own fluidity and adhesion. The drying of the printing ink layer is completed by the evaporation of the solvent contained in the ink

(2) for plastic packaging materials

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