Coated paper special for gold and silver card backing paper and production process and application thereof

Abstract

The invention provides special coated paper for gold and silver card backing paper and a production process and application thereof, and relates to the technical field of special coated paper for gold and silver card backing paper. The preparation method comprises the following steps: grinding chemi-mechanical pulp, mixing the chemi-mechanical pulp with bleached broadleaf wood sulfate pulp and ground calcium carbonate, and squeezing to obtain raw paper; the special coated paper for the backing paper of the gold and silver cards is prepared by coating upper and lower net surfaces of paper with surface glue, then carrying out hard calendaring, then sequentially coating a prime coating, an intermediate coating and a topcoat coating with specific components and proportions, and then carrying out super calendaring, thereby obtaining the special coated paper for the backing paper of the gold and silver cards. According to the technology, the number of convex points is effectively controlled to be smaller than or equal to 5 / m < 2 > after the processed gold and silver cards are processed, the problem that the convex points of common coated paper are shorter than those of white cards when the common coated paper is used for processing the gold and silver cards is effectively solved, the PPS, flatness and smoothness of the paper are better than those of the common coated paper, and the high requirement of the gold and silver cards for flatness is better met.

Description

Technical Field

[0001] This invention relates to the field of coated paper technology, and in particular to a special coated paper for gold and silver card backing, its production process, and its application. Background Technology

[0002] Currently, the base paper for gold and silver cardstock is generally white cardstock, coated cardstock, and coated paper. The first two are multi-layered paper made, meaning the base paper has multiple layers, and the basis weight is generally higher, with a minimum of 170gsm or more. Coated paper, on the other hand, can achieve a lower basis weight. The focus of coated paper used for gold and silver cardstock base paper is different from that of ordinary coated paper used for printing. Ordinary coated paper focuses on printing performance and post-printing processing performance. For example, ordinary coated paper cannot produce color bleeding during printing, and it cannot shed powder or crease during post-printing processing. To increase thickness and reduce costs, existing ordinary coated paper typically incorporates a higher bulk of chemimechanical pulp into the base paper. This chemimechanical pulp generally contains fiber bundles or stone cells. Under single-layer coated paper conditions, these fiber bundles and stone cells inevitably appear on the surface of the base paper. Although coating somewhat masks them, slight protrusions of varying degrees remain. These protrusions have almost no impact on ordinary printing, but when used as a metallized card backing paper, the high smoothness and high gloss of the metallized film amplify the protrusions. Coated paper for metallized card backing paper applications requires superior bonding strength with the metallized film, and the adhesive needs better spreading and wetting ability on the coated paper surface, but excessive adhesive penetration into the base paper layer cannot lead to fiber swelling and warping. Therefore, the focus for metallized card backing paper applications is on superior surface fineness and smoothness, as well as excellent metallized film processing performance. Summary of the Invention

[0003] In view of this, the present invention proposes a special coated paper for gold and silver card backing, its production process, and its application. The present invention can effectively solve the problem of surface protrusion in chemimechanical pulp, while obtaining a paper surface with higher smoothness and fineness, meeting the exquisite requirements of gold and silver cards.

[0004] The technical solution of this invention is implemented as follows: A production process for coated paper specifically for gold and silver card backing includes the following steps: S1. The chemimechanical pulp is ground to obtain ground chemimechanical pulp, which is then mixed with bleached hardwood sulfate pulp. After mixing, ground calcium carbonate (GCC) is added to obtain pulp. The pulp is dewatered and formed through a single-layer headbox and then pressed to obtain base paper. The fiber bundle mass content of the chemimechanical pulp is ≤0.04%, and the stone cell content is ≤10 cells / 0.02㎡. S2. Apply a layer of surface adhesive to both the upper and lower wire mesh surfaces of the base paper, with an adhesive application amount of 1.0±0.5g / m². 2The surface sizing agent comprises enzymatically cleaved starch, polystyrene acrylate copolymer emulsion (SAE), and water in a mass ratio of 10.0:1.0~1.5:88.5~89.0. S3. After applying sizing to the paper surface, hard calendering is performed. S4. Apply a base coat to the top and bottom paper surfaces using a film transfer method, with a coating amount of 5±3 gsm on each side; the base coat comprises ground calcium carbonate, carboxylated styrene-butadiene latex (SBR), starch, and glyoxal in a mass ratio of 89.0:1.8~2.0:8.5~9.0:0.3~0.4. S5. Apply a layer of intermediate coating to the top and bottom paper base coatings using a scraper, with a coating amount of 10±1 gsm for each layer; the intermediate coating comprises ground calcium carbonate, carboxylated styrene-butadiene latex and polyamide epichlorohydrin resin (PAE) in a mass ratio of 91.7:7.5~8.5:0.3~0.4. S6. Apply a topcoat coating to the top and bottom paper coatings using a scraper, with a coating amount of 10±1 gsm for each coating. The topcoat coating comprises ground calcium carbonate, precipitated calcium carbonate (PCC), and carboxylated styrene-butadiene latex in a mass ratio of 84.0~85.0:9.0~9.5:6.5~7.0. S7. Supercalender the coated paper to obtain a special coated paper for gold and silver card backing.

[0005] Furthermore, in step S1, the mass ratio of the milled pulp to the bleached hardwood sulfate pulp is 85~90:10~15.

[0006] Furthermore, in step S1, ground calcium carbonate is added to control the ash content of the slurry to be 12%~14%.

[0007] Furthermore, in step S1, the grinding disc has a tooth width of 1.4-1.7 mm, a groove width of 2.2-3.0 mm, and a net energy consumption of 50-60 kWh / t for grinding.

[0008] Furthermore, in step S3, the linear voltage of the hard pressing is 50±5KN / m.

[0009] Furthermore, the carboxylated styrene-butadiene latex of the topcoat has a tg value of 25-27℃.

[0010] Furthermore, in step S7, the moisture content of the paper is controlled at 5.0 ± 0.3% before supercalendering.

[0011] Furthermore, in step S7, the temperature of the supercalendering is 160-180℃ and the supercalendering line pressure is 115~125KN / m.

[0012] Coated paper prepared by the above-described production process.

[0013] The application of the coated paper of the present invention in the preparation of gold and silver card backing paper.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention controls the fiber bundle and stone cell content by selecting the pulp type, using a specific grinding method, and adjusting the ratio of chemimechanical pulp, thereby controlling the number of bumps in the gold and silver cards to be ≤5 per meter. 2 This effectively solves the problem of unevenness in the use of ordinary coated paper for gold and silver card processing compared to white card.

[0015] 2. Compared to ordinary coated paper, because there are no requirements for resistance to folding and bursting, the base coating and intermediate coating use only a small amount of latex, mainly using starch as an adhesive. The cost of the adhesive is lower, which helps to improve the competitiveness of the product.

[0016] 3. The paper of this invention uses polystyrene acrylate copolymer emulsion for the surface adhesive, glyoxal water-resistant agent that can crosslink with starch for the base coating, PAE water-resistant agent for the intermediate coating, and high Tg latex with superior water resistance for the top coating. This combination of waterproof and water-resistant solutions, with the coatings at each stage being mixed in specific proportions, can effectively prevent excessive penetration of adhesive during aluminum film coating and the negative impact of adhesive on coating strength, avoiding problems such as warping and poor film adhesion. The low moisture content after overpressure also helps to prevent warping.

[0017] 4. Using high Tg latex for the top coating can provide higher adhesion of the aluminum plating film; By employing a hard calendering and overpressure method, under relatively suitable temperature and pressure, the PPS, flatness, and smoothness of the paper are superior to those of ordinary coated paper. The coated paper prepared by this invention has a PPS roughness ≤0.8μm, smoothness ≥650s, flatness ≤35, and coating water resistance ≥250s. The paper has excellent performance and broad application prospects. Detailed Implementation

[0018] To better understand the technical content of this invention, specific embodiments are provided below to further illustrate the invention.

[0019] Unless otherwise specified, the experimental methods used in the embodiments of this invention are all conventional methods.

[0020] Unless otherwise specified, all materials and reagents used in the embodiments of this invention are commercially available.

[0021] The polystyrene acrylate copolymer emulsion of the present invention is a paper surface sizing agent, manufactured by Zhejiang Kesike High-Tech Materials Co., Ltd.

[0022] Example 1 A production process for coated paper specifically for gold and silver card backing includes the following steps: S1. The chemimechanical pulp is ground to obtain ground chemimechanical pulp, which is then mixed with bleached hardwood sulfate pulp at a mass ratio of 88:12. After mixing, ground calcium carbonate is added to control the ash content of the pulp to 12%. The pulp is then dewatered and formed in a single-layer headbox and pressed to obtain base paper with a basis weight of 91.6 gsm. The chemimechanical pulp has a fiber bundle mass content of 0.025% and a stone cell content of 6 per 0.02 m². The grinding disc has a tooth width of 1.65 mm, a groove width of 2.54 mm, and a net grinding energy consumption of 55 kWh / t. S2. Apply a layer of surface adhesive to both the upper and lower wire mesh surfaces of the base paper, with an adhesive application rate of 0.8 g / m². 2 The surface colloid comprises enzymatically cleaved starch, polystyrene-acrylate copolymer emulsion, and water in a mass ratio of 10.0:1.3:88.7. S3. After sizing the paper surface, hard calendering is performed under an online pressing condition of 50KN / m to improve the flatness of the base paper; S4. Apply a base coat to the top and bottom paper surfaces using a film transfer method, with a coating amount of 4.0 gsm on each side; the base coat comprises ground calcium carbonate, carboxylated styrene-butadiene latex, starch, and glyoxal in a mass ratio of 89.0:2.0:8.7:0.3. S5. Apply a layer of intermediate coating to the top and bottom paper base coatings using a scraper, with a coating amount of 9.5 gsm for each layer; the intermediate coating comprises ground calcium carbonate, carboxylated styrene-butadiene latex and polyamide epichlorohydrin resin in a mass ratio of 91.7:8.0:0.3. S6. Apply a topcoat coating to the top and bottom paper coatings using a scraper, with a coating amount of 10.0 gsm for each coating. The topcoat coating comprises ground calcium carbonate, precipitated calcium carbonate, and carboxylated styrene-butadiene latex in a mass ratio of 84.1:9.2:6.7. The tg value of the carboxylated styrene-butadiene latex is 26°C. S7. The coated paper is supercalendered. The moisture content of the paper is controlled at 5.0% before supercalendering. The supercalendering temperature is 170℃ and the supercalendering line pressure is 120KN / m to obtain a special coated paper for gold and silver card backing.

[0023] Example 2 A production process for coated paper specifically for gold and silver card backing includes the following steps: S1. The chemimechanical pulp is ground to obtain ground chemimechanical pulp, which is then mixed with bleached hardwood sulfate pulp at a mass ratio of 86:14. After mixing, ground calcium carbonate is added to control the ash content of the pulp to 14%. The pulp is then dewatered and formed in a single-layer headbox and pressed to obtain a base paper with a basis weight of 92.2 gsm. The chemimechanical pulp has a fiber bundle mass content of 0.025% and a stone cell content of 6 per 0.02 m². The grinding disc has a tooth width of 1.65 mm, a groove width of 2.54 mm, and a net grinding energy consumption of 55 kWh / t. S2. Apply a layer of surface adhesive to both the upper and lower wire mesh surfaces of the base paper, with an adhesive application rate of 1.2 g / m². 2 The surface colloid comprises enzymatically cleaved starch, polystyrene-acrylate copolymer emulsion, and water in a mass ratio of 10.0:1.3:88.7. S3. After sizing the paper surface, hard calendering is performed under an online pressing condition of 50KN / m to improve the flatness of the base paper; S4. Apply a base coat to the top and bottom paper surfaces using a film transfer method, with a coating amount of 5.0 gsm on each side; the base coat comprises ground calcium carbonate, carboxylated styrene-butadiene latex, starch, and glyoxal in a mass ratio of 89.0:2.0:8.7:0.3. S5. Apply a layer of intermediate coating to the top and bottom paper base coatings using a scraper, with a coating amount of 10.0 gsm for each layer; the intermediate coating comprises ground calcium carbonate, carboxylated styrene-butadiene latex and polyamide epichlorohydrin resin in a mass ratio of 91.7:8.0:0.3. S6. Apply a topcoat coating to the top and bottom paper coatings using a scraper, with a coating amount of 10.5 gsm for each coating. The topcoat coating comprises ground calcium carbonate, precipitated calcium carbonate, and carboxylated styrene-butadiene latex in a mass ratio of 84.1:9.2:6.7. The tg value of the carboxylated styrene-butadiene latex is 26°C. S7. The coated paper is supercalendered. The moisture content of the paper is controlled at 5.0% before supercalendering. The supercalendering temperature is 170℃ and the supercalendering line pressure is 120KN / m to obtain a special coated paper for gold and silver card backing.

[0024] Comparative Example 1 Based on Example 2, the tooth width of the refiner was increased to 3.0 mm, the groove width was increased to 4.0 mm, and the rest remained unchanged.

[0025] Comparative Example 2 Based on Example 2, the tooth width of the refiner was increased to 3.0 mm and the groove width was increased to 4.0 mm. At the same time, the net energy consumption of chemimechanical pulp refinement was increased from 55 kWh / t to 85 kWh / t, while the rest remained unchanged.

[0026] Comparative Example 3 Based on Example 2, the primer coating does not contain glyoxal, and the intermediate coating does not contain polyamide epichlorohydrin resin; the rest remains unchanged. The primer coating of this comparative example includes ground calcium carbonate, carboxylated styrene-butadiene latex, and starch in a mass ratio of 89.0:2.3:8.7, and the intermediate coating includes ground calcium carbonate and carboxylated styrene-butadiene latex in a mass ratio of 91.7:8.3.

[0027] Comparative Example 4 Based on Example 2, the glyoxal in the primer coating was replaced with an equal amount of PAE, and the PAE in the intermediate coating was replaced with an equal amount of glyoxal, while the rest remained unchanged. The primer coating in this comparative example comprises ground calcium carbonate, carboxylated styrene-butadiene latex, starch, and polyamide epichlorohydrin resin in a mass ratio of 89.0:2.0:8.7:0.3, and the intermediate coating comprises ground calcium carbonate, carboxylated styrene-butadiene latex, and glyoxal in a mass ratio of 91.7:8.0:0.3.

[0028] Comparative Example 5 Based on Example 2, the glyoxal in the primer coating was replaced with an equal amount of SAE, and the PAE in the intermediate coating was replaced with an equal amount of SAE, while the rest remained unchanged. The primer coating in this comparative example comprises ground calcium carbonate, carboxylated styrene-butadiene latex, starch, and SAE in a mass ratio of 89.0:2.0:8.7:0.3, and the intermediate coating comprises ground calcium carbonate, carboxylated styrene-butadiene latex, and SAE in a mass ratio of 91.7:8.0:0.3.

[0029] Comparative Example 6 Based on Example 2, the Tg value of the carboxylated styrene-butadiene latex in the topcoat was adjusted from 26°C to 18°C, while the rest remained unchanged.

[0030] Comparative Example 7 Based on Example 2, the temperature of supercalendering was reduced from 170°C to 130°C, and the supercalendering pulse voltage was reduced from 120 kN / m to 100 kN / m, while the rest remained unchanged.

[0031] The coated paper prepared in the above examples and comparative examples was subjected to performance testing, and the results are shown in Table 1 below.

[0032] Basis weight: in accordance with GB / T 451.2-2023 "Paper and paperboard - Part 2: Determination of basis weight"; Looseness: Calculated by dividing the thickness by the basis weight, with the thickness conforming to GB / T 451.3-2002 "Determination of Thickness of Paper and Paperboard"; PPS roughness: in accordance with GB / T 22363-2008 "Determination of roughness of paper and paperboard"; Smoothness: According to GB / T 456-2002 "Determination of smoothness of paper and paperboard (Beck method)"; Flatness: The surface roughness is measured using the Surface Roughness Measurement function of the TECHPAP Kheops tester. The principle is to use a light source parallel to the paper surface to illuminate the paper surface, and a camera at the top to photograph the paper surface. The test value is calculated by computer using the Fourier transform method. The higher the value, the worse the surface roughness. Water resistance of the coating: Immerse the paper completely in water at 23°C and start timing. Place a 500g weight (with the bottom roughened by 200-grit sandpaper) at different positions on the paper. At fixed intervals (adjusted according to the water resistance of the coating), drag the weight 2cm and observe whether the white coating peels off the bottom of the weight. If so, it means that the coating has been damaged by water. Record the time in seconds. Test 5 sets and take the average value. The higher the value, the more water resistant the coating. Gold and silver card bump count: After covering the paper with gold and silver card, take a 1 square meter paper sample and observe the number of bumps on the surface of the gold and silver card. The bumps will show reflective points that are different from the normal area.

[0033] Table 1 Paper Test Performance

[0034] Note: The "300+" value means that the measurement will stop after 300 seconds.

[0035] As can be seen from the table above, compared with Example 2, after increasing the tooth width and groove width of the grinding disc in Comparative Example 1, the coarse fibers and fiber bundles of the chemimechanical pulp, as well as the stone cells, were not effectively reduced or shrunk, resulting in varying degrees of deterioration in PPS, smoothness and flatness. The most serious issue was that the number of bumps on the gold and silver cards increased by a factor of 6.

[0036] Compared with Example 2, Comparative Example 2 increased the tooth width and groove width of the grinding disc and increased the net energy consumption of grinding chemical mechanical pulp from 55 kWh / t to 85 kWh / t, but the effect was not significantly improved compared with Comparative Example 1, and the protrusions still seriously exceeded the standard.

[0037] Compared to Example 2, Comparative Example 3 did not contain glyoxal in the base coat and PAE in the intermediate coat, resulting in the paper absorbing more water. The water resistance of the coating decreased from over 300s to 187s, and the paper's flatness decreased from 31.5 in Example 2 to 43.6, showing a significant deterioration in flatness. In addition, PPS and smoothness were also negatively affected to varying degrees.

[0038] Compared to Example 2, Comparative Example 4 showed a slight decrease in coating water resistance, PPS, and smoothness when the glyoxal in the primer and the PAE in the intermediate coat were interchanged. This was mainly because glyoxal requires starch to undergo a cross-linking reaction to achieve its maximum effect. When glyoxal is added to an intermediate coat without starch, its effect is weakened.

[0039] Compared to Example 2, Comparative Example 5 replaced glyoxal in the base coating and PAE in the intermediate coating with SAE sizing agent. Similarly, PPS, smoothness, flatness and water resistance all deteriorated. In particular, the water resistance of the coating dropped to 215s. This shows that the combination of glyoxal and PAE in a specific addition method and ratio can play a synergistic role and improve the performance of paper.

[0040] Compared to Example 2, Comparative Example 6 reduced the tg value of the SBR latex in the topcoat from 26°C to 18°C, which is commonly used for coated paper. The main change was in the water resistance of the coating, which decreased to 86s, much lower than in Example 2. Combined with Comparative Examples 3-5, this shows that using a latex with a suitable tg value in the topcoat has a significant impact on the coating, and its impact is even greater than that of the water-resistant agent in the primer and intermediate coats.

[0041] Compared with Example 2, Comparative Example 7 reduced the supercalendering temperature from 170°C to 130°C and the supercalendering pressure from 120 kN / m to 100 kN / m. The bulk of the paper increased, but the PPS, smoothness, and flatness all deteriorated significantly. The number of bumps also increased to 7. This shows that using appropriate supercalendering temperature and supercalendering pressure can significantly improve the surface finish of the paper.

[0042] The above results demonstrate that, by controlling the fiber bundle and stone cell content of the chemimechanical pulp raw material and employing a specific method to refine the chemimechanical pulp, and under the combined effects of a specific ratio of chemimechanical pulp and hard calendering and supercalendering, the key indicator of the number of raised dots in papermaking for gold and silver cards can be controlled to 5 dots / m². 2 To avoid the negative impact of mechanical pulp on PPS and smoothness, this invention employs a combination of sizing and water-resistant design. The surface sizing uses SAE, the base coating uses glyoxal (which cross-links with the high proportion of starch in the base coating to improve water resistance), the intermediate coating uses PAE (for rapid curing and water resistance), and the top coating uses high-tg latex (for superior water resistance and better glue spreading during gold and silver card lamination). This design reduces the risk of poor paper surface smoothness due to water penetration and fiber swelling during sizing and lamination, thus affecting the quality of the gold and silver cards. Both base weight coated papers prepared in this embodiment achieve the desired results.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A production process for coated paper specifically for gold and silver card backing, characterized in that, Includes the following steps: S1. The chemimechanical pulp is ground to obtain ground chemimechanical pulp, which is then mixed with bleached hardwood sulfate pulp. After mixing, ground calcium carbonate is added to obtain pulp. The pulp is dewatered and formed through a single-layer headbox and then pressed to obtain base paper. The fiber bundle mass content of the chemimechanical pulp is ≤0.04%, and the stone cell content is ≤10 cells / 0.02㎡. S2. Apply a layer of surface adhesive to both the upper and lower wire mesh surfaces of the base paper, with an adhesive application amount of 1.0±0.5g / m². 2 The surface sizing agent comprises enzymatically cleaved starch, polystyrene-acrylate copolymer emulsion, and water in a mass ratio of 10.0:1.0~1.5:88.5~89.

0. S3. After applying sizing to the paper surface, hard calendering is performed. S4. Apply a layer of primer coating to the top and bottom paper surfaces using a film transfer method, with a coating amount of 5±3gsm on each side. The primer coating comprises ground calcium carbonate, carboxylated styrene-butadiene latex, starch, and glyoxal in a mass ratio of 89.0:1.8~2.0:8.5~9.0:0.3~0.

4. S5. Apply a layer of intermediate coating to the top and bottom paper base coatings using a scraper, with a coating amount of 10±1gsm for each layer; the intermediate coating comprises ground calcium carbonate, carboxylated styrene-butadiene latex and polyamide epichlorohydrin resin in a mass ratio of 91.7:7.5~8.5:0.3~0.

4. S6. Apply a topcoat coating to the top and bottom paper coatings using a scraper, with a coating amount of 10±1 gsm for each coating. The topcoat coating comprises ground calcium carbonate, precipitated calcium carbonate, and carboxylated styrene-butadiene latex in a mass ratio of 84.0~85.0:9.0~9.5:6.5~7.

0. S7. Supercalender the coated paper to obtain a special coated paper for gold and silver card backing.

2. The production process of the special coated paper for gold and silver card backing paper according to claim 1, characterized in that, In step S1, the mass ratio of the ground pulverized pulp to the bleached hardwood sulfate pulp is 85~90:10~15.

3. The production process of the special coated paper for gold and silver card backing paper according to claim 1, characterized in that, In step S1, ground calcium carbonate is added to control the ash content of the slurry to be 12%~14%.

4. The production process of the coated paper for gold and silver card backing paper according to claim 1, characterized in that, In step S1, the grinding disc has a tooth width of 1.4-1.7 mm, a groove width of 2.2-3.0 mm, and a net energy consumption of 50-60 kWh / t for grinding.

5. The production process of the special coated paper for gold and silver card backing paper according to claim 1, characterized in that, In step S3, the linear voltage of the hard pressing is 50±5KN / m.

6. The production process of the coated paper for gold and silver card backing paper according to claim 1, characterized in that, The carboxylated styrene-butadiene latex of the topcoat has a tg value of 25-27℃.

7. The production process of the coated paper for gold and silver card backing paper according to claim 1, characterized in that, In step S7, the moisture content of the paper is controlled at 5.0 ± 0.3% before supercalendering.

8. The production process of the coated paper for gold and silver card backing paper according to claim 1, characterized in that, In step S7, the temperature of the supercalendering is 160-180℃ and the supercalendering line pressure is 115~125KN / m.

9. Coated paper prepared by the production process according to any one of claims 1-8.

10. The use of coated paper prepared by the production process according to any one of claims 1-8 or the coated paper shown in claim 9 in the preparation of gold and silver card backing paper.

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