SU1719518A1 - Base for heat-sensitive paper and method for its preparation - Google Patents

Abstract

The invention relates to the pulp and paper industry and improves the physical and mechanical properties of the base. The components are mixed in the following quantity, wt.%: Softwood sulphate pulp from coniferous wood 10-40, unbleached sulphate pulp from coniferous wood 10-35, bleached sulphate pulp from hardwood 20-35 and recycled fiber produced by condenser paper 15-25. From this mass is obtained by casting the base web and calendering from it so that each side of the base web is passed through metal and paper shafts. 2 sp.f-ly, 2 tables.

Description

This invention relates to heat sensitive base formulations and a process for their preparation and can be used in the pulp and paper industry.

Heat-sensitive paper is used for recording information in thermal recording devices and most often is an inert base coated with a heat-sensitive coating on one of its sides.

The characteristics of heat sensitive paper largely depend on the properties of the base and the method of its preparation.

In this connection, an improvement in the quality of heat-sensitive paper can be achieved primarily through the development of new and improved known compositions of the base and methods for its preparation.

For example, the known base for heat sensitive paper, containing

unbleached sulphate pulp, which is obtained by preparing the starting components, casting a web on a paper machine and subsequent calendering, in which one side of the base passes through the metal and the other through the paper roll.

The base obtained has a mass of 1 m 45-51 g, a thickness of 45-52 µm and is characterized by rather high strength (breaking force in the machine direction is not less than 49.0 (5.0) N. (kgf).

However, the substrate has high rigidity and smoothness, which may be the reason for the decrease in adhesion to the heat-sensitive coating and its detachment in the finished product.

In addition, the resulting heat sensitive paper is rigid, suitable for recording information at a slow speed (not

cl

more than 1 m / s) and therefore has limited use.

Closest to the present invention is the base of heat-sensitive paper, containing white sulfate pulp of softwood from 70 May. % and bleached sulphate pulp of hardwood 30 wt.%.

The base is obtained by preparing the base mass for the base, namely: diluting the raw materials to 50 ° SR, diluting with water to the required concentration, purifying the resulting mass and then forming the base web from the mass of the base fabric on a paper machine. The base removed from the reel is moistened and calendered on a supercalender so that one side of it comes along the metal shaft, and the other side over the paper shaft of the calender.

The base thus obtained is suitable for applying on one of its surfaces successively black and then white heat-sensitive paints.

Heat sensitive paper is released in rolls of a width of 1000 mm and 878 mm. The roll diameter should be 6QO ± 1QO mm. The paper is suitable for recording information at high speed and has the following physical and mechanical characteristics:

The mass of paper with an area of 1 m2, g 46 ± 2/5,

Thickness, mkm 49 ± 2,

Destructive force, kgf in machine direction 39 (4,0),

Smoothness, sec., Not less than 220

Breathability ml / min, not more than 60

Whiteness,%, not less than 75

However, the base, chosen as a prototype, is characterized by insufficient values of physical and mechanical properties, which leads to a decrease in consumer properties of heat sensitive paper.

A significant disadvantage of the base is the low mechanical strength, which determines the unsatisfactory mechanical properties of the final product.

High air permeability is the main cause of penetration through the pores of the base of black ink and, accordingly, a reduction in the aesthetic appearance of paper.

Partial elimination of these deficiencies of the foundation can be achieved with a given composition only by increasing the mass of 1 m2, but this, in turn, is impractical because it leads to an increase in the thickness of the substrate and

accordingly, an increase in the diameter of the rolls, which is not always consistent with the dimensions of the devices.

The basis of the prototype is characterized by high smoothness, which may be the reason for its low adhesion to the heat-sensitive coating and may cause its detachment in the finished product.

At the same time, the smoothness of the base is determined only by the lower limit, which is inconsistent with the requirements of metrology and complicates the stabilization of the quality indicators of heat-sensitive paper.

The technology of obtaining the base of the prototype is rather complicated, and the calendering carried out in the proposed manner leads to an increased curl of the base and, accordingly, heat-sensitive paper.

The purpose of the invention is to improve the physicomechanical properties of the substrate.

The goal is achieved by the fact that the base for heat-sensitive paper, containing bleached sulphate pulp from softwood and hardwood, additionally contains unbleached sulphate pulp from coniferous wood and recycled fiber produced by capacitor paper in the following ratio of components, wt.%:

Belen sulphate pulp from coniferous wood 10-40 Nebelen sulphate pulp from coniferous wood 10-35 Belen sulphate pulp from deciduous wood 20-35 Recycled fiber produced by condenser paper 15-25 With this method of obtaining a base for heat-sensitive paper, including the preparation of the original pulp, casting the web out of it and then calendering by passing the web through metal and paper rolls; during calendering, each side of the base web is passed through metal mu and paper shafts.

 With the specified optimal ratio of components of the base with different sizes of fibers and their origin, as well as with the specified method of obtaining, a deeper interaction of the functional groups of fibers occurs, which ultimately leads to an improvement in the physical and mechanical properties of the base.

When choosing the optimal content of the base components, we were guided by the qualitative indicators of the base itself and the heat-sensitive paper.

It is established that the use-. Bleached sulphate pulp from coniferous wood below 10% leads to a significant decrease in the whiteness of the base, i.e. deterioration of the presentation, and above 40% - dramatically increases the smoothness and torsion of the base, which significantly impairs the further technology of using the base.

The content of unbleached sulphate pulp from coniferous wood below 10% does not allow to obtain a basis of high mechanical strength. The introduction of this component in excess of 35% dramatically increases the rigidity of the base and. reduces its technological properties with further processing.

The amount of bleached sulphate pulp from hardwood less than 20% significantly increases the rigidity and reduces the whiteness of the base, but higher than 35% increases the air permeability of the base while reducing mechanical strength.

The introduction of circulating fiber produced by condenser paper below 15% increases the air permeability and transparency of the base, and above 25% increases its curliness, which complicates its further use.

Preparation of the base for heat-sensitive paper is carried out in accordance with the working recipes, examples of which are presented in Table 1,

A base for heat-sensitive paper is obtained according to the following scheme.

Bleached and unbleached sulphate pulp from softwood and bleached sulphate pulp from hardwood are loaded into the pulper in the required quantities. Then the resulting mixture is pumped into the receiving basin, diluted at the same time to a concentration of 2.0-2.4%;

 After that, the mixture is fed to a stream of conical mills for grinding to (55 ± 2) ° СР with a fiber length of 50-70 dg and to a composite basin, where mixing of condenser paper is produced with recycled fiber. The circulating fiber is a mixture of waste capacitor paper 4-30 microns thick, i.e. with a degree of grinding 80-98 ° ShR and a fiber length of 18-80 dg, diluted in water to a certain concentration. Then the mixture of all components of the pulp is crushed on average to 70 ° SR and a length of 50-60 dg, diluted to a concentration of 0.3-0.4%. Thereafter, the resulting mass is suitable for forming the base fabric.

The formation of the base fabric occurs on the paper machine. In the roll, the paper web is cut into two rolls of 1060 mm each (or 980 mm) and fed to the calender.

The arrangement of the rolls in the calender includes a central metal shaft with a diameter of 200 mm, on both sides of which two paper calender rolls and one metal shaft with a diameter of 600 mm are successively arranged. The circuit is also equipped with roll paper rolls located in pairs on both sides of the system called

shafts. .

The base web is refilled according to a scheme in which the base web is passed between a metal shaft and a paper shaft arranged one at a time.

side of the central shaft. Then through a pair of paper-guiding rollers between the central metal shaft and the paper shaft located on the other side of the central shaft.

then on the second pair of guide rollers. The direction of movement of the base web is shown in the diagram by an arrow.

Calendering is carried out at a pressure in hydraulic cylinders of 15 ± 1 kgf / cm2, temperature in-alov not higher than -80 ° C. In this case, the calendering according to the described scheme ensures that each side of the base passes through the metal and paper shafts.

Example 1 The pulper was loaded with 10 kg of bleached softwood sulphate pulp of the HB-1 brand, 35 kg of unbleached sulphate pulp of the coniferous wood of the EK-2 brand and 35 kg of bleached sulphate of bleached hardwood of the OB-1 brand. After grinding, the resulting mixture was pumped into the receiving basin, diluted with water to a concentration of 2.0-2.4%. After dissolution, the mixture was fed to conical mills (MCL-01 - 9 pieces), where the grinding of fibers to 55 ± 2 ° SR took place with a length of 50-70 dg. A mixture of chopped fibers was pumped into a composite

a pool where it was mixed with 20 kg diluted to a concentration of 2.0-2.4% of reusable fiber produced by capacitor paper. Then, the mass containing all the original components was ground into

conic mills up to 7 0 ° SR and lengths of 50-60 dg and directed to the formation of the base on the paper machine B-37A. After cutting the web, two rolls of the base were applied for calendering, which was carried out so that each side of the base once came into contact with the metal and paper rolls of the calender. Physico-mechanical characteristics of the obtained base and heat-sensitive paper are presented in table 2. For comparison, similar data for the prototype and heat sensitive paper based on it were entered into the table.

Example 2. A mixture containing 20 kg of bleached sulphate pulp HBB-2.30 kg of unbleached sulphate pulp from softwood EK-1 and 30 kg of bleached sulphate pulp from hardwood brand OB-2 were placed in a hydraulic disperser and crushed as described in Example 1. Then, 20 kg of recycled fiber from capacitor paper was added to the mixture. The resulting mass was further prepared as in Example 1 and directed to the formation of the base. The properties of the base and heat sensitive paper are presented in Table 2.

Example 3. The initial weight for the preparation of the base, containing 30 kg of bleached sulphate pulp from softwood CB-3, 30 kg of unbleached sulphate pulp from coniferous wood EK-3, 25 kg of bleached sulphate pulp from deciduous wood OB-1 and 15 kg of recycled fiber production of capacitor paper, prepared and applied to obtain the base as in example 1. The properties of the obtained base and heat-sensitive paper are presented in table 2.

Example 4. The initial weight for the formation of the base, containing 40 kg of bleached sulphate pulp from softwood HB-1, 20 kg of unbleached sulphate pulp from coniferous wood EK-1, 20 kg of bleached sulphate pulp from hardwood OB-2 and 20 kg of recycled fiber production of capacitor paper, prepared and used to form the base web as described in Example 1. The properties of the base and paper obtained are listed in Table 2.

Example 5. Initial weight for the preparation of a base for heat sensitive paper containing 40 kg of bleached sulphate pulp from HB-5 softwood, 10 kg of unbleached sulphate pulp from EC-2 softwood, 25 kg of bleached sulphate hardwood pulp from OB-1 and 25 kg of recycled fiber produced by capacitor paper, prepared and used to form the base as described in Example 1. The properties of the base and the corresponding heat sensitive paper are given in Table 2.

From table 2 it follows that the proposed basis and heat sensitive paper on this

Based on all indicators superior prototype.

A significant advantage of the proposed base is a higher value of mechanical strength (the breaking force in the machine direction increased by almost 20%). Increasing the strength of the base provides a more durable heat sensitive paper. This reduces the weight of 1 meter of paper and its

thickness, which, in turn, makes it possible to obtain rolls of the required diameter, corresponding to the dimensions of the devices.

The proposed framework is characterized

lower air permeability, which reduces the penetration of black paint on the back side of heat-sensitive paper and allows to preserve its aesthetics.

At the same time, the proposed base has a lower smoothness, which improves its adhesion to the heat-sensitive coating and reduces the likelihood of its detachment in the finished product.

In addition, an important advantage

The proposed basis is that the amount of smoothness is limited to the upper and lower limits, which is consistent with the requirements of metrology and stabilizes the quality indicators of heat-sensitive

paper.

The proposed method is simple to implement and provides a base that is characterized by higher rates of physico-mechanical properties.

properties and less curl, which simplifies its further use.

Thus, the proposed base and method for producing it allows the fabrication of heat sensitive paper of higher quality suitable for recording information at high speed.

Claims (2)

Claim 1. Base for heat sensitive paper, containing bleached sulphate pulp from softwood and hardwood, characterized in that, in order to improve the physical and mechanical properties of the substrate, it additionally contains unbleached sulphate pulp from coniferous wood and recycled fiber produced by condenser paper the degree of grinding 80-98 ° ShR and a fiber length of 18-80 Dg in the following ratio of components, wt.%: Belen sulfate pulp from coniferous wood 10-40 Besen sulfate-cellulose from deciduous wood 20-35 Nebelen sulfate pulp from coniferous wood 10-35 Recycled fiber produced by capacitor paper15-25 0 2. A method of obtaining a base for heat-sensitive paper, including preparing the initial pulp, pouring a web out of it and then calendering it by passing the web along metal and paper shafts, so that when calendering each side cloths are passed through metal and paper shafts .. Table 1 table 2