Manufacturing method of body paper suitable for rotary digital printing and bar code label paper

Abstract

The invention belongs to the technical field of papermaking, and discloses a manufacturing method of body paper suitable for rotary digital printing and bar code label paper. The manufacturing method comprises the following steps: by taking bleached sulfate needlebush chemical pulp and needlebush hot-ground chemimechanical pulp as fiber raw materials, mixing the bleached sulfate needlebush chemical pulp and the needlebush hot-ground chemimechanical pulp in a weight ratio of (20-40%): (60-80%) to form mixed pulp; the raw paper suitable for rotary digital printing is prepared through sizing, pulp screening, pulp flowing, net part dehydration forming, drying and specific surface coating; carboxymethyl cellulose salt with the substitution degree of 1-1.3 is added between the sizing step and the pulp screening step, and the dosage is 3-5 kg / t paper. The prepared paper product has an excellent ink fixing effect, is high in longitudinal and transverse tearability, has excellent printing processing performance, is relatively low in cost, and can be used as bar code label paper.

Description

Technical Field

[0001] This invention belongs to the field of papermaking technology, and relates to a method for manufacturing base paper suitable for rotary digital printing and barcode label paper. Background Technology

[0002] The base paper suitable for rotary digital printing can be used to produce barcode labels. Post-processing requires digital printing, die-cutting, and other steps. Generally, the paper must possess excellent longitudinal and transverse strength, excellent ink drying performance, and excellent digital printing results. Paper used for barcode labels is called barcode label paper. Domestically, papers that meet these requirements mainly include coated paper and writing paper.

[0003] Currently, the production cost of these papers is high, resulting in high processing costs for barcode processing companies and seriously affecting the industry's development. Furthermore, existing barcode label papers often fall short in meeting digital printing requirements, primarily due to slow ink drying, which severely impacts processing speed and efficiency. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for manufacturing base paper suitable for rotary digital printing and barcode label paper. The resulting paper product has excellent water-ink adhesion effect, high tear strength in both the longitudinal and transverse directions, excellent printing and processing performance, and low cost, and can be used as barcode label paper.

[0005] This invention provides a method for manufacturing base paper suitable for rotary digital printing, comprising the following steps: using bleached sulfate softwood chemical pulp and softwood thermomechanical pulp as fiber raw materials, wherein the weight ratio of bleached sulfate softwood chemical pulp to softwood thermomechanical pulp is 20-40%: 60-80%, the mixture is mixed to form a mixed pulp, and then subjected to sizing, sieving, flow, wire dewatering and forming, drying, and surface coating to produce base paper suitable for rotary digital printing;

[0006] The freeness of the bleached sulfate softwood chemical pulp is controlled at 48-52°SR, and the freeness of the softwood thermomechanical pulp is controlled at 46-50°SR. Carboxymethyl cellulose salt with a degree of substitution of 1-1.3 is added between the pulping and screening processes, at a dosage of 3-5 kg / t paper. The coating material for the surface includes: more than 98 parts by weight of calcium silicate pigment; 8-15 parts by weight of polyvinyl acetate latex; and less than 2 parts by weight of nano titanium dioxide.

[0007] In some embodiments, the calcium silicate pigment has a honeycomb structure and a median particle size of 4–8 micrometers; the calcium silicate pigment is a byproduct of alumina extraction from fly ash; and the nano-titanium dioxide has a particle size of 20–50 nanometers.

[0008] In some embodiments, the coating applied to the surface comprises: 98 to 99.5 parts by weight of calcium silicate pigment; and 0.5 to 2 parts by weight of nano-titanium dioxide.

[0009] In some embodiments, the coating applied to the surface further includes: 0.2-0.5 parts by weight of polyvinyl alcohol; 0.5-1 parts by weight of lubricant; and 0.5-1 parts by weight of water-repellent agent.

[0010] In some embodiments, the mixed slurry is prepared into a mixed slurry with a concentration of 3 to 3.2%.

[0011] In some embodiments, the slurry concentration is 0.9-1.2%, and the slurry is applied after sand and air removal.

[0012] In some embodiments, 6-12 kg / t of fluorescent whitening agent is added between the sizing and screening processes.

[0013] In some embodiments, the basis weight of the base paper suitable for rotary digital printing is 80–120 g / m³. 2 The whiteness is 98-100%.

[0014] In some embodiments, the longitudinal tear strength of the base paper suitable for rotary digital printing is ≥400mN, and the transverse tear strength is ≥350mN.

[0015] This invention provides a barcode label paper, which is manufactured by the method described above.

[0016] Compared with existing technologies, the pulp used in this invention is bleached sulfate softwood chemical pulp (NBKP) and softwood thermomechanical pulp (CTMP), with a weight ratio of NBKP 20-40% and CTMP 60-80%. Using all softwood pulp ensures paper tear resistance, while replacing traditional bleached chemical pulp with CTMP semi-chemical pulp significantly reduces costs. To ensure paper strength, both NBKP and CTMP are beaten, with beating degrees controlled at 48-52°SR and 46-50°SR, respectively. These high beating degrees effectively improve paper strength and simultaneously cut the fibers to improve paper uniformity. This invention further improves uniformity by adding an anionic uniformity agent in the wet end of papermaking. The anionic uniformity agent is carboxymethyl cellulose salt with a substitution degree of 1.0-1.3, whose anionic properties are consistent with the ionicity of the fibers, effectively dispersing the pulp fibers and improving paper structure uniformity. This invention uses synthetic calcium silicate (CaSiO3) as the main pigment in the surface coating. CaSiO3 has strong absorption properties, which can improve the ink drying speed during digital printing on paper. Furthermore, a small amount of nano-titanium dioxide is incorporated into the coating pigment. Nano-titanium dioxide has a high specific surface area and opacifying properties, which can improve the coating's barrier effect on pigment particles in the ink, ensuring that pigment particles are retained on the paper surface as much as possible.

[0017] Therefore, the paper products produced by this invention have excellent ink drying properties and printing effects, high tear strength in both directions, and low cost, and can be used as barcode label paper. Attached Figure Description

[0018] Figure 1 This is a photograph of the actual product after die-cutting according to Embodiment 1 of the present invention. Detailed Implementation

[0019] The technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0020] This invention provides a method for manufacturing base paper suitable for rotary digital printing, comprising the following steps: using bleached sulfate softwood chemical pulp and softwood thermomechanical pulp as fiber raw materials, wherein the weight ratio of bleached sulfate softwood chemical pulp to softwood thermomechanical pulp is 20-40%: 60-80%, the mixture is mixed to form a mixed pulp, and then subjected to sizing, screening, flow, wire dewatering and forming, drying, and surface coating to produce base paper suitable for rotary digital printing;

[0021] The freeness of the bleached sulfate softwood chemical pulp is controlled at 48-52°SR, and the freeness of the softwood thermomechanical pulp is controlled at 46-50°SR. Carboxymethyl cellulose salt with a degree of substitution of 1-1.3 is added between the pulping and screening processes, at a dosage of 3-5 kg / t paper. The coating material for the surface includes: more than 98 parts by weight of calcium silicate pigment; 8-15 parts by weight of polyvinyl acetate latex; and less than 2 parts by weight of nano titanium dioxide.

[0022] The paper product obtained by this invention has excellent water-ink adhesion, high tear strength in both the longitudinal and transverse directions, excellent printing and processing performance, and low cost, and can be used as barcode label paper.

[0023] In this embodiment of the invention, bleached sulfate softwood chemical pulp (NBKP) and softwood thermomechanical pulp (CTMP) are used as fiber raw materials for blending, with the weight ratio of NBKP to CTMP being 20-40%:60-80%. In some embodiments, the weight ratio of NBKP to CTMP is 25%:75%, 30%:70%, or 35%:65%.

[0024] The bleached sulfate softwood pulp described in this invention is a chemical wood pulp produced from softwood through a bleached sulfate pulping process. Specifically, it is made from softwood (such as spruce and larch) through processes including slicing, cooking, washing, and screening. The bleached pulp is treated with chlorine or peroxide to achieve a brightness of 85% ISO or higher. The fiber length is generally 2.8-4.0 mm, and the tensile strength is ≥65 N·m / g. Conventional chemithermomechanical pulp (CTMP) is a pulping technique that combines chemical pretreatment (such as alkaline sodium sulfite impregnation) with mechanical refining. The parameters of the softwood CTMP described in this invention include: brightness 78-82%, fiber length 2.5-3.8 mm, and tensile strength ≥45 N·m / g. This invention uses all-needle pulp for papermaking. The longer the fiber length, the higher the tear strength, ensuring high requirements for longitudinal and transverse tear strength of the paper (e.g., ensuring longitudinal tear strength ≥400mN; transverse tear strength ≥350mN), which is beneficial for post-processing operations such as die-cutting of barcode label paper. At the same time, this invention uses CTMP semi-chemical pulp instead of traditional bleached chemical pulp, significantly reducing costs.

[0025] Furthermore, to ensure paper strength, both NBKP and CTMP undergo beating, with the beating degree controlled at 48-52°SR and 46-50°SR, respectively. This embodiment of the invention controls a relatively high beating degree, which not only effectively improves paper strength but also cuts the fibers as necessary, thus improving paper uniformity. The beating degree, also known as freeness, is denoted by °SR and is an indicator of pulp refining effectiveness; it is obtained according to national standard methods.

[0026] According to the above pulp ratio, the paper product described in the embodiments of the present invention is preferably produced by mixing and adjusting the pulp, screening the thick pulp, adjusting the ingredients, flushing the pulp, removing sand and air, then sizing, screening the paper machine, passing through the headbox, dewatering and forming the wire section, pressing, pre-drying, surface coating, post-drying, and finally calendering, winding, and packaging.

[0027] In embodiments of the present invention, the mixed slurry can be prepared into a mixed slurry with a concentration of 3 to 3.2%, and the flushing concentration of the mixed slurry can be 0.9 to 1.2%. The slurry preparation, flushing, and desanding and degassing are all commonly used processes in the art and are not particularly limited.

[0028] In this embodiment of the invention, sizing is performed on conventional paper machine equipment, preferably with the addition of anionic leveling agents and fluorescent whitening agents before the paper machine screen. Specifically, a carboxymethyl cellulose salt with a degree of substitution of 1-1.3 is added between the sizing and screening processes, at a dosage of 3-5 kg / t of paper. Since 100% long-fiber softwood pulp is used, paper uniformity is a key concern. This embodiment of the invention uses an anionic leveling agent (specifically, high-substitution sodium carboxymethyl cellulose, CMC) added before the paper machine screen to improve paper uniformity. Because high-substitution sodium carboxymethyl cellulose has a substitution degree of 1.0-1.3, and its anionic properties are consistent with the ionic properties of the fibers, the surface of the long fibers after beating combines with CMC to form a surface with strong anionic properties. This enhances the repulsion between fibers, effectively dispersing the pulp fibers, preventing fiber agglomeration, and thus improving paper structure uniformity. The dosage of the anionic leveling agent is 3-5 kg / t of paper.

[0029] To ensure paper whiteness, this invention preferably adds 6-12 kg / t of fluorescent whitening agent to the pulp, more preferably 7-11 kg / t; the addition point is before the paper machine screen. The specific fluorescent whitening agent is tetrasodium 4,4'-bis[[4-[bis(2-hydroxyethyl)amino]-6-(4-sulfoaniline)-1,3,5-triazine-2-yl]amino]stilbene-2,2'-disulfonic acid, which is pale yellow in appearance, has a molecular weight of 1165, and a fluorescence intensity above 100. In the embodiments of this invention, the headbox, wire dewatering and forming, pressing, calendering, etc., involved are all commonly used processes in the art and are not particularly limited.

[0030] To ensure excellent digital printing results on paper, this embodiment of the invention uses synthesized calcium silicate (CaSiO3) as the main pigment for surface coating. The surface coating comprises at least 98 parts by weight of the pigment CaSiO3, preferably 98-99.5 parts. Specifically, the median particle size of the pigment CaSiO3 is controlled at 4-8 micrometers. CaSiO3 has a unique honeycomb structure and extremely strong absorption capacity, which can effectively improve the ink drying speed during digital printing on paper. Furthermore, the synthesized calcium silicate can be obtained as a byproduct of alumina extraction from fly ash, resulting in lower costs.

[0031] To further improve the printing effect, the coating material applied to the surface preferably contains 0.5-2.0 parts by weight of nano-titanium dioxide (nano-TiO2), for example, 0.5 parts, 1 part, or 2 parts. Specifically, the nano-titanium dioxide has a particle size of 20-50 nanometers and has an extremely high specific surface area (e.g., a specific surface area of ​​120-250 m²). 2 / g), with extremely strong covering power, which helps to improve the barrier effect of the coating on pigment particles in the ink, so that the pigment particles are retained on the paper surface as much as possible, thereby improving the ink's color fixation effect, etc.

[0032] Furthermore, the surface coating described in this embodiment of the invention comprises: 8-15 parts by weight of polyvinyl acetate latex, more specifically 9-13 parts. Specifically, its solid content is 48-52%, its room temperature viscosity is 500-800 mPa·s, its pH value is 5-6, its glass transition temperature is 28-30°C, and its particle size is 0.5-2.0 micrometers. In this embodiment of the invention, the surface coating further comprises, by weight: 0.2-0.5 parts of polyvinyl alcohol; 0.5-1 parts of lubricant; and 0.5-1 parts of water-resistant agent. The polyvinyl alcohol serves to improve the adhesion strength of the coating, with a molecular weight of 50,000-100,000. The lubricant is preferably calcium stearate, with a solid content of 50%, primarily improving the rheological properties of the coating. The water-resistant agent is ammonium zirconium carbonate, with a solid content of 50%, primarily improving the water resistance of the coating.

[0033] As a preferred embodiment, the specific coating formulation of the present invention is as follows:

[0034] Table 1. Coating formulations of some embodiments of the present invention.

[0035] Components Formula (per serving) <![CDATA[CaSiO3]]> 98.0-99.5 Nano titanium dioxide 0.5-2.0 Polyvinyl acetate latex 8-15 Polyvinyl alcohol 0.2-0.5 lubricant 0.5-1.0 Water-resistant agent 0.5-1.0

[0036] This invention provides a barcode label paper, manufactured by the method described above. In embodiments of this invention, the barcode label paper is produced by rolling and packaging following the aforementioned forming process.

[0037] The main parameters of the base paper product suitable for rotary digital printing obtained in the embodiments of the present invention are: basis weight 80-120 g / m³. 2The paper's whiteness is preferably 98-100%; its smoothness is ≥200s. For example, the longitudinal tear strength of the base paper is ≥400mN, such as 400-485mN; the transverse tear strength is ≥350mN (such as 350-400mN); and the solid print density (black) is ≥1.2. This paper product exhibits excellent ink-water adhesion, high longitudinal and transverse tear strength, excellent printing and processing performance, and low cost, which is beneficial to industry development.

[0038] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention. Unless otherwise specified, all figures are by weight. Furthermore, all raw materials and reagents used in this invention are commercially available. NBKP has a whiteness of 85% ISO or higher, a fiber length of 2.8-4.0 mm, and a tensile strength ≥65 N·m / g; CTMP has a whiteness of 78-82%, a fiber length of 2.5-3.8 mm, and a tensile strength ≥45 N·m / g. The leveling agent is sodium carboxymethyl cellulose with a degree of substitution of 1-1.3; the fluorescent whitening agent has a molecular weight of 1165 and a fluorescence intensity of ≥100. The calcium silicate pigment has a honeycomb structure with a median particle size of 4-8 micrometers; the calcium silicate pigment is a byproduct of alumina extraction from fly ash, with a particle size of 20-50 nanometers. Polyvinyl alcohol improves the adhesion strength of the coating, with a molecular weight of 50,000-100,000. The lubricant is calcium stearate with a solid content of 50%; the water-resistant agent is ammonium zirconium carbonate with a solid content of 50%.

[0039] Example 1

[0040] The pulp mix ratio is: 25% bleached sulfate softwood chemical pulp (NBKP) and 75% softwood thermomechanical pulp (CTMP); the freeness of NBKP and CTMP are 50°SR and 47°SR, respectively. After mixing, the pulp is adjusted to a concentration of 3.1%, then passed through a thick pulp screen, conditioning, and flushing, at which point the concentration is controlled at 1.12%. After further desanding and deaeration, and sizing, a uniformity agent and a fluorescent whitening agent are added before the paper machine screen, at dosages of 5 kg / t paper and 10 kg / t paper, respectively. The pulp then passes through the paper machine screen, headbox, wire section dewatering and forming, pressing, pre-drying, surface coating, post-drying, calendering, winding, and packaging to produce barcode label paper.

[0041] The pulp concentrations at the inlet and outlet of the paper machine screens were 1.0% and 0.98%, respectively, and the inlet and outlet pressures were 2.5 bar and 0.21 bar, respectively. The headbox outlet concentration was 0.98%, the pH value was 8.3, the wire section white water concentration was 0.24%, and the press section first and second press pressures were 720 and 800 kN / m, respectively. The pre-drying moisture content was 6.8%, and the post-drying moisture content was 6.5% (the following examples are basically the same). The surface coating formulation is as follows. The measured basis weight was 118 g / m³. 2The paper has a whiteness of 99.5%, a smoothness of 255s, a longitudinal tear strength of 436mN, a transverse tear strength of 361mN, and a solid print density (black) of 1.5.

[0042] Table 2. Coating formulation of Example 1

[0043] Components Formula (per serving) <![CDATA[CaSiO3]]> 99 Nano titanium dioxide 1 Polyvinyl acetate latex 11 Polyvinyl alcohol 0.3 lubricant 0.7 Water-resistant agent 0.7

[0044] Example 2

[0045] The pulp mix ratio is: 30% bleached sulfate softwood chemical pulp (NBKP) and 70% thermomechanical pulp (CTMP); the freeness of NBKP and CTMP are 48°SR and 48°SR, respectively. After mixing, the pulp is adjusted to a concentration of 3.0%, passed through a thickener screen, conditioning, and flushing, at which point the concentration is controlled at 0.92%. It then undergoes desanding, deaeration, and sizing. A uniformity agent and a fluorescent whitening agent are added before the paper machine screen, at dosages of 3 kg / t paper and 8 kg / t paper, respectively. The pulp then passes through the paper machine screen, headbox, wire section dewatering and forming, pressing, pre-drying, surface coating, post-drying, calendering, winding, and packaging to produce barcode label paper. The surface coating formula is as follows: Basis weight 80 g / m³. 2 The paper has a whiteness of 99%, a smoothness of 245s, a longitudinal tear strength of 455mN, a transverse tear strength of 385mN, and a solid print density (black) of 1.6.

[0046] Table 3. Coating formulation for Example 2

[0047] Components Formula (per serving) <![CDATA[CaSiO3]]> 98 Nano titanium dioxide 2 Polyvinyl acetate latex 9.5 Polyvinyl alcohol 0.4 lubricant 0.5 Water-resistant agent 0.5

[0048] Example 3

[0049] The pulp mix ratio is: 35% bleached sulfate softwood chemical pulp (NBKP) and 65% thermomechanical pulp (CTMP). The freeness of NBKP and CTMP are 51°SR and 49°SR, respectively. After mixing, the pulp is adjusted to a concentration of 3.1%, then passed through a thickener screen, conditioning, and flushing, at which point the concentration is controlled at 0.98%. After further desanding and deaeration, and sizing, a leveling agent and a fluorescent whitening agent are added before the paper machine screen, at dosages of 4 kg / t paper and 9 kg / t paper, respectively. The pulp then passes through the paper machine screen, headbox, wire section dewatering and forming, pressing, pre-drying, surface coating, post-drying, calendering, winding, and packaging to produce barcode label paper. The surface coating formula is as follows.

[0050] Table 4. Coating formulation for Example 3

[0051] Components Formula (per serving) <![CDATA[CaSiO3]]> 99.5 Nano titanium dioxide 0.5 Polyvinyl acetate latex 12 Polyvinyl alcohol 0.35 lubricant 0.8 Water-resistant agent 0.8

[0052] The quantitative result was 90 g / m³. 2The paper has a whiteness of 98.5%, a smoothness of 235s, a longitudinal tear strength of 481mN, a transverse tear strength of 392mN, and a solid print density (black) of 1.7.

[0053] After digital printing of barcode labels as described in Example 1, the die-cut product is as follows: Figure 1 As shown. For traditional paper, its whiteness is 75-85%, smoothness is 30-50s, longitudinal tear strength is 100-200mN; transverse tear strength is 60-120mN, and printing solid density (black) is 0.3-0.8.

[0054] As can be seen from the above embodiments, the paper product obtained by the manufacturing method of the present invention has excellent water-ink adhesion effect, high tear strength in both the longitudinal and transverse directions, excellent printing and processing performance, and low cost, and can be used as barcode label paper.

[0055] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be noted that due to the limitations of textual expression, while there are objectively infinite specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the inventive concept and technical solution to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A method for manufacturing base paper suitable for rotary digital printing, characterized in that, Includes the following steps: Using bleached sulfate softwood chemical pulp and softwood thermomechanical pulp as fiber raw materials, the weight ratio of bleached sulfate softwood chemical pulp to softwood thermomechanical pulp is 20-40%: 60-80%. After mixing, a mixed pulp is formed. The pulp is then subjected to sizing, screening, flow, wire dewatering and forming, drying, and surface coating to produce base paper suitable for rotary digital printing. The freeness of the bleached sulfate softwood chemical pulp is controlled at 48-52°SR, and the freeness of the softwood thermomechanical pulp is controlled at 46-50°SR; a carboxymethyl cellulose salt with a degree of substitution of 1-1.3 is added between the pulping and screening processes, at a dosage of 3-5 kg / t paper. The coating applied to the surface comprises: more than 98 parts by weight of calcium silicate pigment; 8-15 parts by weight of polyvinyl acetate latex and less than 2 parts by weight of nano titanium dioxide.

2. The manufacturing method according to claim 1, characterized in that, The calcium silicate pigment has a honeycomb structure and a median particle size of 4–8 micrometers; the calcium silicate pigment is a byproduct of alumina extraction from fly ash; the nano-titanium dioxide has a particle size of 20–50 nanometers.

3. The manufacturing method according to claim 2, characterized in that, The coating material applied to the surface comprises: 98 to 99.5 parts by weight of calcium silicate pigment; and 0.5 to 2 parts by weight of nano-titanium dioxide.

4. The manufacturing method according to any one of claims 1-3, characterized in that, The coating applied to the surface further includes: 0.2-0.5 parts by weight of polyvinyl alcohol; 0.5-1 parts by weight of lubricant; and 0.5-1 parts by weight of water-repellent agent.

5. The manufacturing method according to any one of claims 1-3, characterized in that, The mixed slurry is prepared to a concentration of 3-3.2%.

6. The manufacturing method according to any one of claims 1-3, characterized in that, The slurry concentration is 0.9-1.2%, and it is applied after sand and air removal.

7. The manufacturing method according to any one of claims 1-3, characterized in that, A fluorescent whitening agent of 6-12 kg / t paper is added between the sizing and screening processes.

8. The manufacturing method according to claim 7, characterized in that, The basis weight of the base paper suitable for rotary digital printing is 80-120 g / m³. 2 The whiteness is 98-100%.

9. The manufacturing method according to any one of claims 1-3, characterized in that, The longitudinal tear strength of the base paper suitable for rotary digital printing is ≥400mN, and the transverse tear strength is ≥350mN.

10. A barcode label paper, characterized in that, It is prepared by the manufacturing method according to any one of claims 1-9.

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