Home xin Review materials for special printing materials?

Review materials for special printing materials?

by admin

composition of paper:
plant fiber, filler, rubber and pigment
formation of paper: pulping, papermaking, finishing and processing,
physical properties of paper: quantitative, thickness and tightness, hardness and softness
chemical properties of paper:
moisture, ash, acid-base, resistance Sizing degree
optical properties of paper: whiteness, gloss and opacity
surface properties of paper:
smoothness and flatness, ink absorption and surface strength
mechanical properties of paper: tensile strength, folding resistance, tear resistance and viscoelasticity
types of printing paper: News printing paper, books and periodicals, offset, coating Synthetic paper and composite paper
packaging and printing materials: paperboard and corrugated board, plastic, metal, composite packaging materials, glass and ceramic packaging materials

composition and classification of ink:
pigment, filler, binder and auxiliary agent
structure and stability of ink:
structural system of ink Stability of ink
rheological properties of ink:
ink fluid and rheological curve, viscosity, yield value, thixotropy, fluidity and fluidity, specificity
drying properties of ink:
permeability drying, oxidative polymerization drying, volatile drying, radiation curing drying
Relationship between ink dryness and printing:
factors affecting ink dryness:
optical properties of ink: color, coloring power, transparency and gloss
resistance of ink: light resistance, heat resistance, acid, alkali, water and solvent resistance
viscoelasticity of ink: viscosity and wiredrawing
physical properties of ink: density Fineness, dispersion and permeability
types of printing inks: lithographic printing ink, relief printing ink, screen printing ink, optical printing ink, thermal printing ink, functional printing ink and digital printing ink

1 Definition and basic composition of paper:
paper: sheet material with plant fiber as the main component, which is used in printing, writing, painting, packaging, daily life, industrial and agricultural production and other fields
basic composition: 1) plant fiber 2) auxiliary materials: rubber, color, filler and chemical additives
2 Types of papermaking raw materials: 1) wood fiber raw materials (coniferous wood and broad-leaved wood) 2) non wood fiber raw materials (reed, bagasse, rice and wheat straw, phloem and seed wool, etc.) 3) waste paper
chemical composition: cellulose and hemicellulose (carbohydrate), lignin, extract (substances dissolved in water or organic solvent)
3 Biological structure of papermaking raw materials: plants are composed of cells
main types of plant cells: 1) sclerenchyma cells: necessary substances in fiber paper; 2) parenchyma cells: miscellaneous cells, which need to be removed
fibers play a role of mechanical support in plants
4 Paper sizing purpose: improve the water resistance of paper
sizing methods: internal sizing, surface sizing, double sizing
5 Surface sizing features: improve the hydrophobicity and printability of the paper; Improve the physical strength and surface properties of paper; Less glue loss (compared with internal sizing); Reduce the deformation or difference between two sides of the paper; The equipment used is complex, the price of sizing agent is expensive and the production cost is high
surface sizing is generally limited to paper with high requirements and special purposes, such as banknote paper, map paper, securities paper, offset printing paper, whiteboard paper, etc.
6 The function of paper filling is related to the type of filler
filling is to add fine pigment or synthetic filler of white mineral to the paper material
types of commonly used fillers: talc (3mgo • 4sio2 • H2O), calcium carbonate, titanium dioxide (titanium dioxide), etc.
functions: ⑴ improve the optical properties of paper; (2) improve the surface properties of paper; (3) meet some special properties of paper; (4) save fiber raw materials
7 The main process engineering of pulping: the process of dissociating plant fiber raw materials into pulp by chemical or mechanical methods, or a combination of both
main process:
8 Pulping methods and differences: 1) chemical method: lime method, caustic soda method, sulfate method and sulfite method 2) semi chemical method
3) chemical mechanical method 4) mechanical method
9 Purpose, principle and process of pulp washing:
washing purpose: separate pulp from cooking waste liquid (including fiber cell wall and cell cavity) to ensure the cleanness of pulp
washing principle: filtration, extrusion and diffusion
washing method: multi-stage countercurrent washing is generally adopted
10 Principle of pulp screening and purification
screening: the process of fiber impurity separation with perforated or slotted sieve plate by using the difference between the size and shape of impurities and fibers. Fiber bundles, UN digested fragments, knots, miscellaneous cells and other fibrous impurities are removed by screening
purification: the process of fiber impurity separation is carried out by using the different specific gravity of impurities and fibers. Remove non fibrous impurities such as mud, sand and metal by purification
11 Types of bleaching agents commonly used for pulp:

oxidizing bleaching agents: Cl2, chlorine dioxide (ClO2), hypochlorite, H2O2, O2, ozone, etc. Chemical pulp is mainly bleached by this method. Lignin is dissolved through oxidation to realize bleaching and improve the purity and whiteness of pulp
reducing bleaching agent: bisulfite, etc. this method is mainly used for the bleaching of high yield pulp. Change the chromogenic group of lignin and colored substances into colorless group and decolorize the pulp
12 Pulping process of waste paper:
shredding: the waste paper is treated into pulp suspension containing fiber bundles and small pieces of paper by hydraulic pulper, and the shredding rate is generally less than 75%
dredging: the shredded pulp suspension is treated by dredging equipment to further separate fibers and promote the shredding and separation of ink particles
impurity removal: through screening Remove light and heavy impurities (including ink particles) from waste paper by means of purification and deinking
13 Main technological process of papermaking:
14 Beating mechanism and task
beating: use physical methods (such as mechanical shear, friction, hydraulic impact, etc.) to treat fiber suspension (pulp) to make it meet the requirements of paper machine production, so as to obtain the expected paper quality. This process is called beating
beating task: ⑴ use physical methods, Carry out mechanical or fluid treatment on the pulp to make the fiber subject to shear force and change the fiber shape. (2) adapt to the requirements of paper machine, and control the forming and water filtering performance of paper on the web
15 Main effect of beating on fibers: beating enhances the bonding force between fibers and improves the tensile strength, burst resistance, folding resistance, smoothness and tightness of paper. At the same time, it will also reduce the average length of the fiber and the absorption and opacity
crushing effect: break the outer layers of the primary and secondary walls of the fiber. Crushing increases the specific surface area of the fiber, which is conducive to the combination of fiber and fiber during paper forming
cutting effect: the fiber is cut laterally by mechanical shearing
wire splitting brooming effect: the mechanical, hydraulic and friction effects cause the fiber to split longitudinally, broom at both ends, hair on the surface, and improve the bonding force between fibers
16 Structural characteristics of paper: 1) it has multi-phase and complex structural element components
2) anisotropic distribution of structural elements: it makes the paper form vertical and horizontal strength difference Vertical and horizontal deformation difference
3) it has the characteristics of hairy and fine pore colloid: it makes the paper absorbent
4) the binding force between structural elements determines the nature of the paper: many performance indexes (especially strength indexes) of the paper are related to the binding force of fibers
5) the structure of the paper has two sides: poor smoothness on both sides and poor surface strength on both sides
17 The main reason for the difference between the positive and negative sides of the paper
reason: when the paper is formed, the water is filtered through the net in one direction
front: the side away from the net is relatively smooth, with more filler and fine fiber content, compact structure and high smoothness
back: the side close to the net is relatively rough, with less filler and fine fiber content (loss with water), The structure is relatively loose
when the paper is formed, it is inevitable, and the difference between the two sides of the high-quality paper is small
18. The main reason for the difference in the longitudinal and transverse strength of the paper
longitudinal: the direction parallel to the running direction of the paper machine when the paper is copied
transverse: perpendicular to the running direction of the paper machine
reason: in the pulp suspension, the fibers are arranged disorderly. After forming, under the action of inertial force, the number of fibers arranged along the longitudinal direction and the number of fibers arranged along the transverse direction
the existence of longitudinal and transverse direction makes the mechanical properties of the paper in two directions different, such as the number of equal dimensions of tensile strength, forming the longitudinal and transverse direction

19 Main properties of printing paper (paperboard)
general properties: appearance quality, quantity, thickness, tightness, dimensional stability, etc.
mechanical properties: tensile strength, burst resistance, folding resistance, tear resistance, elongation, ring compression strength, stiffness, tensile energy absorption
permeability: air permeability, moisture permeability, oil permeability, water resistance, hydrophobicity, etc.
optical properties: whiteness, gloss, color, (opacity), etc.
surface properties: smoothness, surface friction coefficient, roughness, adhesion, hair and powder removal, etc
printing performance: surface strength, ink absorption, sizing degree, etc.
20 General performance index of paper
quantitative: the weight of paper or paperboard per unit area, expressed in g /m2
thickness: refers to the vertical distance between the upper and lower surfaces of paper or paperboard under a certain pressure per unit area, often expressed in mm
or μ M refers to
tightness: the weight of paper per unit volume, i.e. the ratio of quantitative and thickness, in g /m3, also known as apparent density
loose thickness: the volume of paper with a certain weight, which is the reciprocal of tightness, in cm3 /g
water content: the ratio of the mass of water contained in paper or paperboard to the total mass of the paper or paperboard, expressed in percentage
21 Water content of paper and its influence on paper performance
paper has hygroscopicity and dehumidification. The nature of paper depends on the surrounding environmental conditions (such as temperature and humidity)
equilibrium water content: under certain environmental temperature and humidity conditions, the water content of paper can reach a fixed value, and the water content at this time is called this temperature Equilibrium moisture content under humidity
change of paper moisture content: 1) deformation: it causes the expansion of paper size and affects the dimensional stability of paper, generally transverse shrinkage> longitudinal shrinkage
2) strength change: it affects the strength of paper
22 Main factors affecting the water content of paper:
1) pulp type and purity: it is mainly the content of hemicellulose. Hygroscopicity: hemicellulose> cellulose
2) temperature: under a certain humidity, the water content of paper is inversely proportional to the temperature (approximately linear relationship
3) humidity: when the temperature is constant, the water content of paper does not have a linear relationship with the relative humidity
23 Moisture absorption and dehumidification process of paper:
high humidity and low temperature: moisture content caused by humidity change

Related Posts

Leave a Comment