A non-fade thermal printing paper and a method for preparing the same

Abstract

An anti-erasable thermal printing paper and its preparation method are disclosed. To address the defect of thermal printing paper being easily erased upon contact with alcohol, this invention improves upon this by addressing the following three aspects: 1. Adding a transparent top coating layer to the developing layer to protect it and prevent alcohol penetration and damage; 2. Using a coating formula with stronger color development; 3. Employing a curtain coating process for more precise coating amount, uniform coverage, and comprehensive protection. The beneficial effects of this invention are: 1. Excellent barcode information scanning and reading; 2. Higher image retention rate; 3. Improved retention rate and alcohol penetration resistance of the thermal paper.

Description

Technical Field

[0001] This invention belongs to the field of thermal printing paper manufacturing technology, and relates to a thermal printing paper with anti-staining function and its preparation method. Background Technology

[0002] Medical thermal printing paper with anti-erasing properties is mainly used for printing labels in medical settings. Because medical personnel frequently come into contact with alcohol and then touch labels on patients' IV drip bottles, the ink on the labels can be dissolved by the alcohol, becoming blurred or disappearing, resulting in incomplete label information. Existing medical thermal printing paper has the following shortcomings: 1. Before printing, the text printed after the thermal paper comes into contact with alcohol is unclear, and barcode scanning is abnormal; 2. After printing, the image on the thermal paper will melt away after contact with alcohol, with a retention rate of <60%. These shortcomings cause significant inconvenience during the use of thermal printing paper. Summary of the Invention

[0003] To address these shortcomings, this invention provides a thermal printing paper with anti-staining function and its manufacturing process and method by adjusting the product structure, coating formulation, and production process. This thermal printing paper is particularly suitable for use in the medical field.

[0004] This invention improves upon the following three aspects to obtain anti-erasing thermal printing paper: 1. Adding a transparent top coating layer on the color developing layer to protect it and prevent alcohol from penetrating and damaging it; 2. Using a coating formula with stronger color development; 3. Using a curtain coating process for more precise coating amount, uniform coverage, and no dead corners in protection.

[0005] The aforementioned anti-marking thermal printing paper includes a substrate layer at the bottom, a base coating layer above the substrate layer, a top coating layer above the base coating layer, and a top coating layer above the top coating layer, wherein the coating amounts of the base coating layer, the top coating layer, and the top coating layer are 4-5 g / m², 3-4 g / m², and 1-3 g / m², respectively.

[0006] The substrate layer is made from base paper, which is pure wood pulp base paper with a strength of 40-70 g / m².

[0007] The base coating is composed of a mixture of raw materials such as kaolin, PVA, styrene-butadiene latex, and hollow sphere pigments, and its main function is:

[0008] A. Leveling and increasing opacity: Improving the smoothness of the original paper surface and the opacity of the paper during the coating process;

[0009] B. Prevent penetration: Ensures that the effective components of the base coating do not penetrate into the substrate layer (base paper);

[0010] C. Reduce heat loss: During the printing process, heat is concentrated in the color development layer and not conducted to the substrate layer. This allows for higher printing sensitivity and speed with a small amount of thermal coating, thereby reducing production costs.

[0011] The surface coating is made of PVA, color developer polishing liquid, colorless dye polishing liquid, sensitizer and styrene-butadiene latex and other raw materials. Its main function is: when the thermal paper is printed, the print head heats up (also known as the hot head), which instantly heats the paper surface it is in contact with. This causes the colorless dye molecules in the thermochromic layer of the heated part of the paper surface to react with the color developer, that is, to become colored dye, thereby displaying the color of the font or pattern.

[0012] The top coating is composed of a mixture of kaolin, silica, PVA, zinc stearate, anti-organic solvents, lubricants, and crosslinking agents, and its main function is:

[0013] 1) Isolation and protection: mainly a mixture of silica and anti-organic solvent. An organic material is coated on the surface of silica to form a silica structure, namely fumed silica. Due to its small particle size, the network structure has hydrophobic properties to inhibit flow. In addition, the action of PVA and crosslinking agent crosslinks and binds the molecular chains together to improve the adhesion effect. It has good sealing and anti-permeability, establishes a permeation barrier, and prevents alcohol, water, oil, etc. from penetrating into the color layer and damaging the printed pattern, thus playing a protective role such as anti-erasing.

[0014] 2) Improve smoothness: This is mainly achieved by adding lubricants and zinc stearate, along with calendering and shaping during manufacturing, which improves the surface smoothness, brightness, and light stability of thermal paper.

[0015] 3) Preventing adhesion: The main component of the top coating is kaolin, which is mixed with other raw materials to form a very smooth, flat, and non-sticky thin layer. This can prevent the top coating from adhering to the print head. At the same time, kaolin has thermal conductivity and does not hinder the transfer of heat during printing, thus not affecting the color development effect.

[0016] The present invention also provides a method for preparing the above-mentioned anti-marking thermal printing paper, the method of which is as follows:

[0017] Step 1): Material Preparation

[0018] Preparation of base coat coating

[0019] According to the mixing ratio and order of addition in the primer coating ratio table (see Table 1), the raw materials are added to the mixing tank in sequence. After addition, the mixture is stirred at the specified speed and time to obtain a primer coating with a solid content of 30-35%. The mass ratio of water, calcined kaolin, PVA adhesive, styrene-butadiene latex, and pigment is 205-220:51-55:2-4:11-15:30-34:

[0020]

[0021] Table 1. Mixing ratio of primer coating

[0022] Topcoat coating preparation;

[0023] According to the proportions and order of addition in the topcoat coating formulation table (see Table 2), the raw materials are added to the mixing tank in sequence. After addition, the mixture is stirred at the specified speed and time to obtain a topcoat coating with a solid content of 25-32%. The mass ratio of water, PVA adhesive, color developer slurry, colorless dye slurry, sensitizer slurry, and styrene-butadiene latex is 190-210:17-20:38-42:20-24:9-11:8-11.

[0024]

[0025] Table 2. Topcoat Coating Mixing Ratio

[0026] Topcoat coating preparation

[0027] According to the proportions and order of addition in the topcoat coating mixing table (see Table 3), the raw materials are added to the mixing and dispersion tank in sequence. After addition, the mixture is stirred at the specified speed and time to obtain a topcoat coating with a solid content of 18-22%. The mass ratio of kaolin dispersion, silica dispersion, PVA adhesive, zinc stearate, anti-organic solvent mixture, lubricant, crosslinking agent, defoamer, and water is 23-26:13-15:17-19:10-13:4-6:15-17:8-10:0.3-0.5:390-410.

[0028]

[0029]

[0030] Table 3 Top Coating Coating Proportioning Table

[0031] Step 2): Prepare anti-marking thermal printing paper

[0032] The coating process utilizes a multi-functional thermal paper curtain coating machine with a speed of 500 meters per minute. This multi-functional thermal paper coating equipment mainly consists of a winding and unwinding system, a curtain coating system, a drying system, a transmission system, and an electrical control system. The drying system comprises 18 sets of hot air ovens. Through curtain coating, the machine can complete the application of the base coating, top coating, and top coating, as well as paper shaping and / or calendering of medical-grade three-proof thermal paper in a single operation at a high speed of 500 meters per minute.

[0033] 2.1) Substrate layer: The base paper is pure wood pulp paper with a width of 1560mm-1760mm and a strength of 40-70g / ㎡.

[0034] 2.2) Apply a base coat of paint and then dry it to form the base coat.

[0035] 2.3) Apply a second coat of topcoat paint and then dry it to form a topcoat.

[0036] 2.4) Apply a third coat of topcoat paint and then dry it to form the topcoat layer;

[0037] 2.5) Shaping and calendering: The coated paper is shaped by a solid cast iron roller and a rubber-coated soft roller under the pressure of 150KN / m by a hydraulic system to improve the smoothness and brightness of the paper. The paper is then wound up and packaged to obtain the anti-marking thermal printing paper.

[0038] The coating amounts for the primer, topcoat, and topcoat are 4-5 g / m², 3-4 g / m², and 1-3 g / m², respectively.

[0039] The drying temperature is controlled between 80℃ and 120℃.

[0040] The moisture content of the finished paper after coating and drying is controlled at 6.0%-7.5%.

[0041] The beneficial effects of this invention are as follows:

[0042] 1. The barcode information is scanned and read well. The non-direct touch screen coating method causes less damage to the base coating and top coating, and the coating is thin and uniform (low cost), resulting in clearer display and good barcode scanning and reading.

[0043] 2. Higher image retention rate. Adjustments to the formulation of the base coating and top coating improve the water and oil resistance of the thermal paper, resulting in an image retention rate of ≥85%.

[0044] 3. The top coating provides an anti-permeation barrier layer against alcohol penetration, thereby effectively preventing alcohol from penetrating into the thermal color developing layer and avoiding color degradation of the thermal color developing layer, which would cause the text or pattern to become blurred or disappear. This improves the retention rate and anti-alcohol penetration performance of the thermal paper. Attached Figure Description

[0045] Figure 1 This is a simplified structural diagram of the anti-marking thermal printing paper of the present invention;

[0046] Figure 2 This is a flowchart illustrating the preparation process of the anti-marking thermal printing paper of the present invention. Detailed Implementation

[0047] Example 1

[0048] Step 1): Material Preparation

[0049] The base paper is 1560mm wide and made of pure wood pulp at 55g / m².

[0050] Preparation of base coat coating

[0051] According to the proportions and order of addition in the primer coating ratio table (see Table 1), the raw materials are added to the mixing tank in sequence. After addition, the mixture is stirred at the specified speed and time to obtain a primer coating with a solid content of 31%.

[0052]

[0053] Table 1. Mixing ratio of primer coating

[0054] Topcoat coating preparation;

[0055] According to the proportions and order of addition in the topcoat coating ratio table (see Table 2), the raw materials are added to the mixing tank in sequence. After addition, the mixture is stirred at the specified speed and time to obtain a topcoat coating with a solid content of 32%.

[0056]

[0057]

[0058] Table 2. Topcoat Coating Mixing Ratio

[0059] Topcoat coating preparation

[0060] According to the proportions and order of addition in the topcoat coating ratio table (see Table 3), the raw materials are added to the mixing and dispersing tank in sequence. After addition, the mixture is stirred at the specified speed and time to obtain a topcoat coating with a solid content of 19%.

[0061]

[0062]

[0063] Table 3 Top Coating Coating Proportioning Table

[0064] Step 2): Prepare anti-marking thermal printing paper

[0065] The coating process utilizes a multi-functional thermal paper curtain coating machine with a speed of 500 meters per minute. This multi-functional thermal paper coating equipment mainly consists of a winding and unwinding system, a curtain coating system, a drying system, a transmission system, and an electrical control system. The drying system comprises 18 sets of hot air ovens. Through curtain coating, the machine can complete the application of the base coating, top coating, and top coating, as well as paper shaping and / or calendering of medical-grade three-proof thermal paper in a single operation at a high speed of 500 meters per minute.

[0066] 2.1) Prepare the base layer: The specifications of the base paper are 1560mm-1760mm in width and 40-70g / ㎡ pure wood pulp paper.

[0067] 2.2) Apply a base coat of paint and then dry it to form the base coat.

[0068] 2.3) Apply a second coat of topcoat paint and then dry it to form a topcoat.

[0069] 2.4) Apply a third coat of topcoat paint and then dry it to form the topcoat layer;

[0070] 2.5) Shaping and calendering: The coated paper is shaped by a solid cast iron roller and a rubber-coated soft roller under the pressure of 150KN / m by a hydraulic system to improve the smoothness and brightness of the paper. The paper is then wound up and packaged to obtain the anti-marking thermal printing paper.

[0071] The coating amounts for the primer, topcoat, and topcoat are 4-5 g / m², 3-4 g / m², and 1-3 g / m², respectively.

[0072] The drying temperature is controlled between 80℃ and 120℃.

[0073] The moisture content of the finished paper after coating and drying is controlled at 6.0%-7.5%.

[0074] Example 2 was carried out using the same production process and formula. Example 2 used pure wood pulp paper with a width of 1560mm and a strength of 58g / ㎡.

[0075] Performance testing

[0076] The technical properties of the printing papers from Examples 1 and 2 after coating were tested, and the test results are shown in Table 4 below:

[0077]

[0078]

[0079] Table 4.

Claims

1. A type of anti-erasable thermal printing paper, characterized in that, The anti-marking thermal printing paper includes a substrate layer at the bottom, a base coating layer above the substrate layer, a top coating layer above the base coating layer, and a top coating layer above the top coating layer, wherein the coating amounts of the base coating layer, the top coating layer, and the top coating layer are 4-5 g / m², 3-4 g / m², and 1-3 g / m², respectively. The base coating is prepared from water, calcined kaolin, PVA adhesive, styrene-butadiene latex and pigments in the following mass ratio of 205-220:51-55:2-4:11-15:30-34. The surface coating is prepared from water, PVA adhesive, color developer polishing slurry, colorless dye polishing slurry, sensitizer polishing slurry and styrene-butadiene latex in the following mass ratio of 190-210:17-20:38-42:20-24:9-11:8-11; The top coating is prepared from kaolin dispersion, silica dispersion, PVA adhesive, zinc stearate, anti-organic solvent mixture, lubricant, crosslinking agent, defoamer and water in the following mass ratio of 23-26:13-15:17-19:10-13:4-6:15-17:8-10:0.3-0.5:390-410. The anti-organic solvent mixed solution is C 18 –C 30 linear alkane; The crosslinking agent is C 12 H 20 O6.

2. The method for preparing thermal printing paper as described in claim 1, characterized in that, The preparation method includes the following steps: Step 1): Prepare the base coat, top coat, and top layer coating according to the mass proportions; Step 2): Preparing anti-marking thermal printing paper: 2.1) Prepare the base layer: The base paper should be 1560mm-1760mm wide and made of pure wood pulp at 40-70g / m². 2.2) Apply a base coat of paint and then dry it to form the base coat. 2.3) Apply a second coat of topcoat paint and then dry it to form a topcoat. 2.4) Apply a third coat using the topcoat paint, then dry to form the topcoat layer; 2.5) After shaping and calendering, the paper is wound up and packaged to obtain the anti-marking thermal printing paper. The application rates of the primer, topcoat, and topcoat are 4-5 g / m², 3-4 g / m², and 1-3 g / m², respectively. The drying temperature should be controlled between 80℃ and 120℃; The moisture content of the finished paper after coating and drying is controlled at 6.0%-7.5%; The three coating processes are carried out using a multi-functional thermal paper curtain coating machine with a machine speed of 500 meters per minute.

Images