A multi-layered thin base paper composite paper and a pre-embossing roller thereof

Abstract

The utility model discloses a kind of multilayer thin base paper composite paper and its pre-embossed roller, including at least two thin base papers, the thin base paper of at least two is formed with bottom pattern embossed base paper after being pre-embossed by mechanical nesting, the bottom pattern is composed of several micro-embossed points, then each road the embossed base paper converges and is stacked to form multilayer paper web, or each road the embossed base paper and the thin base paper that is not pre-embossed converge and are stacked to form multilayer paper web;The utility model effectively solves the technical problem that low grammage thin base paper embossing effect is not good, and the prepared composite paper has thicker overall thickness, more fluffy structure and smoother delicate touch;Meanwhile, the production cost of finished paper is significantly reduced by the application of low grammage raw material, realizes high cost performance, and provides key technical support for the leapfrog development of paper material to "lightweight, functional, environmental protection".

Description

Technical Field

[0001] This utility model relates to the technical field of household paper manufacturing, and in particular to a multi-layer thin base paper composite paper material and its pre-embossing roller. Background Technology

[0002] In the field of household paper, the embossing process commonly used in multi-layer paper materials (such as facial tissues, toilet paper, and wiping paper) mainly involves the pressing action of embossing rollers and rubber rollers to form embossed patterns on the base paper, thereby improving the paper's aesthetics, cleaning ability, and wiping effect. However, the traditional embossing process has certain requirements for the basis weight of the base paper, requiring the use of medium to high basis weight base paper of 15-30 g / m², resulting in high manufacturing costs for the finished paper.

[0003] However, for low-grammage paper (typically thin base paper with a specified weight of 8-20 g / m² and a thickness of only 0.07-0.13 mm), the manufacturing cost is lower than that of medium- and high-grammage base paper of 15-30 g / m². However, the fundamental compatibility barrier when performing embossing processes on this type of low-grammage paper has led to its long-standing reputation as "unable to be effectively embossed," as specifically manifested in the following ways: The contradiction between the physical properties of low-basis-weight paper and embossing processes The core physical characteristics of low-grammage paper (sparse fibers, low strength, and poor toughness) are incompatible with the mechanical requirements of the embossing process: 1) Fragile fiber structure: Low-grammage paper is made of short fibers randomly interwoven, and the bonding force between fibers is weak. During embossing, the local pressure applied by the embossing roller convex points can easily cause fiber breakage, forming a "press-through" defect; 2) Poor thickness uniformity: The thickness of low-grammage paper fluctuates greatly, and the gap between the embossing roller and the rubber roller is difficult to precisely match the paper thickness, resulting in insufficient pressure in some areas and excessive pressure in others (press-through), making it impossible to form a uniform embossing structure; 3) Weak resilience: The fiber elastic modulus of low-grammage paper is low, and the fibers are prone to plastic deformation after embossing. The embossing points are prone to collapse, making it impossible to form a stable "convex-concave" structure.

[0004] 2. Limitations of the adaptability of existing embossing techniques Traditional embossing processes (suitable for medium-to-high basis weight paper materials, such as 15-30 g / m²) achieve embossing through methods such as "steel-to-glue" and "convex-concave embossing." However, when this technology is directly applied to low basis weight paper materials, it has the following fatal flaws: 1) Embossing parameter mismatch: The design of the raised dots on the traditional embossing rollers is seriously mismatched with the thickness of low basis weight paper materials (0.07-0.13 mm)—the height of the raised dots is much greater than the thickness of the paper. Not only are the tips of the raised dots prone to piercing the paper during embossing, but there is also a great difficulty in matching the pressure between the rollers, increasing the manufacturing difficulty; 2) 1) Traditional embossing has a large area, and after embossing, the paper not only has a large shadow of the embossed pattern, resulting in a poor visual effect, but also has problems such as hard touch, grainy texture, and poor water absorption; 2) Limited functional expansion: Low basis weight paper is difficult to form an effective embossing structure (such as raised dots with a depth ≥0.4mm), and cannot improve the interlayer bonding of glue-free composite through embossing (under traditional processes, the anti-delamination strength of glue-free composite is only 0.2N / 15mm), and can only rely on high-cost processes (such as adhesive composite) or sacrifice functions (such as abandoning embossing).

[0005] However, in recent years, driven by the trends of "lightweight" and "environmentally friendly", the market demand for low-grammage paper materials has surged. However, existing technologies cannot solve the problems of its composite and embossing, which leads to limited product performance and inability to meet market demand.

[0006] In summary, developing an embossing process suitable for low-grammage paper materials and resolving their core contradictions of "embossing-blurring-collapse" has become a key breakthrough in promoting the lightweight and functional development of paper materials. Utility Model Content

[0007] This invention aims to overcome the shortcomings of the prior art and provide a multi-layer thin base paper composite paper material and its pre-embossing roller. By optimizing the distribution parameters of micro-embossing points, the basis weight of the thin base paper and the stacking process, it also takes into account the softness and fluffiness of the paper.

[0008] To achieve the above objectives, the present invention provides a multi-layer thin base paper composite paper material, comprising at least two low-grammage thin base papers. The at least two thin base papers are respectively mechanically nested and pre-embossed to form at least two embossed base papers with background patterns. The background patterns are composed of several micro-embossing dots. Subsequently, the embossed base papers after pre-embossing are combined and stacked to form a multi-layer paper web. The background pattern of the embossed base paper satisfies the following characteristics: • The total area of ​​each micro-embossing point within a unit square decimeter accounts for 13-20% of the total area. • The area of ​​each micro-embossed dot is 0.015-0.23 mm. 2 .

[0009] Furthermore, the pre-embossed base paper is combined and stacked with the un-pre-embossed thin base paper to form a multi-layer paper web.

[0010] Furthermore, the background pattern of the embossed base paper also satisfies the following characteristics: • The distance between any two adjacent micro-embossing dots in the same row is 0.2-0.95mm; • The row spacing between any two adjacent rows of micro-embossed dots is 0.2-0.95mm.

[0011] Furthermore, the basis weight of each sheet of the thin base paper is 8-20 g / m².

[0012] Furthermore, the depth of each of the micro-embossing points is 0.3-0.9 mm.

[0013] Furthermore, the embossed base paper is laminated by mechanical nesting to form a multi-layered paper web, wherein the multi-layered paper web is partially embossed to form a layered pattern.

[0014] Furthermore, the embossed base paper and thin base paper are laminated by mechanical nesting to form a multi-layered paper web, wherein the multi-layered paper web is partially embossed to form a layered pattern.

[0015] Furthermore, at least two pre-embossed base papers are used as interlayers and sandwiched between two un-pre-embossed thin base papers, thereby stacking the embossed base papers and thin base papers to form a multi-layered paper web.

[0016] Furthermore, each of the embossed base papers is pre-embossed to form a background pattern, and then the embossed base papers are combined and stacked to form multiple layers of paper.

[0017] Furthermore, the embossed base paper after pre-embossing is divided into at least two pre-stacked paper webs. Each pre-stacked paper web contains at least one embossed base paper. One pre-stacked paper web is first mechanically nested and embossed once, and then merged and stacked with other pre-stacked paper webs for a second mechanical nesting and embossing process, thereby making the thin base paper of each path composite to form a multi-layered paper web.

[0018] Furthermore, at least two of the pre-stacked paper webs converge in an opposing stacking manner, causing the micro-embossing points of the two adjacent embossed base papers in the opposing stacked pre-stacked paper webs to form one or a combination of the following bonding forms: • The outer bottom surfaces of the micro-embossing dots on two adjacent embossed base papers are fully or partially in contact and bonded together; • The micro-embossing points of two adjacent embossing base papers are not nested with each other, and the micro-embossing points of one embossing base paper do not contact or adhere to the non-embossed flat area of ​​the other embossing base paper.

[0019] Furthermore, in the multi-layered paper web having multiple embossed base papers, the micro-embossing dots of any two adjacent embossed base papers form the following bonding pattern: • The micro-embossing dots of two adjacent embossing base papers protrude in the same direction, and the micro-embossing dots of one embossing base paper (1B, 3B) are completely or partially misaligned with the micro-embossing dots of the other embossing base paper, so that the bottom surface of the micro-embossing dots of the upper embossing base paper comes into contact with and adheres to the non-embossed plane area of ​​the lower embossing base paper.

[0020] A pre-embossing roller includes a pre-embossing roller adapted for use in multilayer thin paper composites, wherein the roller surface of the pre-embossing roller has a plurality of embossing protrusions that match the background pattern of the embossing base paper, and the embossing protrusions satisfy the following characteristics: • The total area of ​​all embossed protrusions within a unit square decimeter accounts for 13-20% of the total area. • The area of ​​each of the embossed protrusions is 0.015-0.23 mm2.

[0021] The present invention adopts the above-mentioned solution, and its beneficial effects are as follows: by optimizing and improving the embossing process, and through parameter characteristics, roller group coordination and other methods, the embossing process of low grammage thin base paper is realized, resulting in a multi-layered paper web with "full-coverage background pattern + partial overlapping pattern", which solves the problems of embossing effect and interlayer bonding of low grammage thin base paper. The prepared paper material has a thicker overall thickness, a more fluffy structure and a smoother and more delicate touch. At the same time, the application of low grammage raw materials significantly reduces production costs and achieves high cost performance, providing key technical support for the leapfrog development of paper materials towards "lightweight, functional and environmentally friendly" directions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the production process for implementing Case 1.

[0023] Figure 2 This is a schematic diagram of the multi-layer paper web in Case Study 1.

[0024] Figure 3 This is a schematic diagram of the apparatus used to prepare multi-layer paper webs in Case Study 1.

[0025] Figure 4 A schematic diagram of the production process for implementing Case 2.

[0026] Figure 5 This is a schematic diagram of the multi-layer paper web in Case Study 2.

[0027] Figure 6 This is a schematic diagram of the apparatus used to prepare multi-layer paper webs in Case Study 2.

[0028] Figure 7 This is a schematic diagram of the background pattern E.

[0029] Figure 8 This is a schematic diagram of the layered pattern F.

[0030] Figure 9 This is an exploded diagram of the background pattern E and the layered pattern F of the four-way thin base paper.

[0031] Figure 10 This is a schematic diagram of the apparatus used to prepare multi-layer paper webs in Case Study 3.

[0032] Figure 11 This is a schematic diagram of the multi-layer paper web in Case Study 3.

[0033] Figure 12 This is a schematic diagram of the apparatus used to prepare multi-layer paper webs in Case Study 4.

[0034] Figure 13 This is a schematic diagram of the multi-layer paper web in Case Study 4.

[0035] Figure 14 This is a schematic diagram of the apparatus used to prepare multi-layer paper webs in Case Study 5.

[0036] Figure 15 This is a schematic diagram of the multi-layer paper web in Case Study 5.

[0037] Figure 16 This is a schematic diagram of the apparatus used to prepare multi-layer paper webs in Case Study 6.

[0038] Figure 17 This is a schematic diagram of the multi-layer paper web in Case Study 6.

[0039] Among them, 1-embossing roller group, 11-pre-pressing roller, 12-pre-embossing roller, 2-composite roller group, 21-composite pattern roller, 211-pressing roller, 22-composite back roller, 1A, 2A, 3A, 4A-thin base paper, 1B, 2B, 3B, 4B-embossing base paper, 1C, 2C-pre-stacked paper web, D-multi-layer paper web, E-background pattern, F-stacked pattern, a-dot spacing, b-line spacing. Detailed Implementation

[0040] To facilitate understanding of this utility model, a more complete description of it is provided below with reference to the accompanying drawings. The drawings illustrate preferred embodiments of the utility model. However, this utility model can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to provide a more thorough and complete understanding of the disclosure of this utility model.

[0041] See appendix Figure 1-15As shown in this embodiment, a multilayer thin base paper composite paper material includes at least three low-grammage thin base papers 1A, 2A, 3A, and 4A. For ease of explanation, a four-layer thin base paper is used as an example. Those skilled in the art can choose more layers of thin base paper (such as five layers) or three layers of thin base paper according to actual product requirements. No specific limitation is made here, which belongs to the derivative technical solution. Specifically, with reference to the accompanying drawings, each layer of thin base paper in this embodiment is defined as numbered 1A, 2A, 3A, and 4A, and each layer of embossed base paper is defined as numbered 1B, 2B, 3B, and 4B. At least two layers of the thin base paper 1A, 2A, 3A, and 4A are pre-embossed by mechanical nesting to form embossed base papers 1B, 2B, 3B, and 4B with a background pattern E. The background pattern E is composed of several micro-embossed dots.

[0042] Specifically, see Appendix Figure 3 and 6 As shown, for embossed base papers 1B, 2B, 3B, and 4B that require the formation of a background pattern E, a set of embossing rollers 1 can be mechanically nested for pre-embossing, thereby forming a background pattern E composed of several micro-embossing dots (the arrangement of these micro-embossing dots can be either regular or random, depending on the product pattern requirements; those skilled in the art can design appropriate patterns as needed, and no specific limitation is made here). Each set of embossing rollers 1 includes a pre-pressing roller 11 and a pre-embossing roller 12 (a rigid metal roller) that are pressed together. The surface of the pre-embossing roller 12 has several raised embossing bosses. Thus, thin base papers 1A, 2A, 3A, and 4A pass through the gap between the roller surfaces of the pre-pressing roller 11 and the pre-embossing roller 12. At this time, the pre-pressing... The embossing protrusions of the embossing roller 12 press against the thin base papers 1A, 2A, 3A, and 4A, causing the thin base papers 1A, 2A, 3A, and 4A to be locally thinned under the concentrated pressure of the protruding tips of the embossing protrusions (forming micro-embossing dots). At the same time, the rubber roller deforms due to elasticity under pressure, providing support for the thin base papers 1A, 2A, 3A, and 4A and preventing them from being punctured. Meanwhile, the non-protruding part of the pre-embossing roller 12 contacts the elastic surface of the rubber roller, applying a uniform base pressure only to the thin base papers 1A, 2A, 3A, and 4A, allowing the thin base papers 1A, 2A, 3A, and 4A to maintain their original thickness (forming non-embossed flat areas). Finally, the surface of the thin base papers 1A, 2A, 3A, and 4A is embossed to form a background pattern E composed of several micro-embossing dots, resulting in embossed base papers 1B, 2B, 3B, and 4B.

[0043] Based on this, according to actual product requirements, appropriate numbers of thin base papers 1A, 2A, 3A, and 4A can be selected for pre-embossing. Then, the pre-embossed base papers 1B, 2B, 3B, and 4B can be combined and stacked to form a multi-layer paper web D. Alternatively, the embossed base papers 1B, 2B, 3B, and 4B can be combined and stacked with un-pre-embossed thin base papers 1A, 2A, 3A, and 4A to form a multi-layer paper web D. At this point, the multi-layer paper web D can be laminated. The lamination process can employ methods such as adhesive lamination or mechanical glue-free lamination. These lamination methods are common in the field. For ease of understanding, the following explanation uses mechanical glue-free lamination as an example: The embossed base papers 1B, 2B, 3B, and 4B are laminated using mechanical nesting to form the multi-layer paper web D. Alternatively, the embossed base papers 1B, 2B, 3B, and 4B, along with the thin base papers 1A, 2A, 3A, and 4A, are laminated using mechanical nesting to form the multi-layer paper web D. The multi-layer paper web D is partially embossed to form a layered pattern F. For details, please refer to the appendix. Figure 8-12 As shown, the aforementioned mechanical nesting can be achieved using a composite roller group 2, thereby mechanically nesting and bonding the stacked embossed base papers 1B, 2B, 3B, and 4B, or mechanically nesting and bonding the stacked embossed base papers 1B, 2B, 3B, and 4B with the thin base papers 1A, 2A, 3A, and 4A. The composite roller group 2 includes a composite pattern roller 21 (made of hard metal, the roller surface of which can be configured according to different product requirements, such as...) that is pressed and fitted together. Figure 6 The composite flower roller 21 shown is suitable for tissue paper making and has dotted / lined protrusions on its surface. It can also be replaced with, for example... Figure 3 The illustrated embossing roller 211, suitable for roll paper and having at least one annular strip-shaped protrusion on its surface (those skilled in the art can select a suitable protrusion structure as needed), and the composite back roller 22 (which can be a smooth, flat, hard steel roller or a soft rubber roller; the appropriate roller surface can be selected according to the composite requirements). The composite pattern roller 21 has locally formed raised composite bosses on its surface. Thus, each embossing base paper 1B, 2B, 3B, 4B, or each embossing base paper 1B, 2B, 3B, 4B and thin base paper 1A, 2A, 3A, 4A together enter the gap between the composite pattern roller 21 and the composite back roller 22 and pass through, utilizing... The composite bosses of the composite roller 21 press and squeeze the stacked embossing base papers 1B, 2B, 3B, and 4B, or the embossing base papers 1B, 2B, 3B, and 4B with thin base papers 1A, 2A, 3A, and 4A, thereby locally thinning them under concentrated pressure from the protruding tips of the composite bosses (forming a stacked pattern F). Simultaneously, the composite back roller 22 provides support for the embossing base papers 1B, 2B, 3B, and 4B and / or the thin base papers 1A, 2A, 3A, and 4A, preventing punctures and maintaining their original thickness. Finally, they are laminated together to form a multi-layered paper web D, and a stacked pattern F is locally formed on the surface of the multi-layered paper web D. This stacked pattern F can be as follows: Figure 8 and9 The "Yunrou" lettering shown can be used by those skilled in the art to design layered patterns F as needed based on actual pattern design, without any specific limitations here.

[0044] In this embodiment, the embossing roller group 1 and the composite roller group 2 may also adopt other phase-derived pressing structures, such as the embossing forms in the patent "CN112095366A A glue-free composite device and glue-free composite paper material". No specific restrictions are made here, and the art can set a suitable structural form as needed.

[0045] In this embodiment, the background pattern E formed by the pre-embossed base papers 1B, 2B, 3B, and 4B satisfies the following characteristics: The total area of ​​all micro-embossing dots within a unit square decimeter accounts for 13-20%. Generally, the size of a single finished sheet of paper is 128×180mm, 190×132mm, etc., i.e., 1dm. 2 The area of ​​each finished sheet of paper is less than 4 dm. 2 (100cm) 2 The area of ​​each finished sheet of paper is less than 400 cm². 2 ).

[0046] (2) The area of ​​each micro-embossed dot is 0.015-0.23 mm. 2 The “point area” mentioned here refers to the area of ​​the horizontal plane formed by the top surface of the embossing protrusion acting on the paper surface, excluding the side surface area formed by the sidewall of the embossing protrusion.

[0047] Similarly, in order to prepare the aforementioned background pattern E for embossing, the thin base papers 1A, 2A, 3A, and 4A are embossed by the embossing roller group 1 to form embossed base papers 1B, 2B, 3B, and 4B with the background pattern E. The pre-embossing roller 12 has a number of embossing protrusions on its surface that match the background pattern E of the embossed base papers 1B, 2B, 3B, and 4B. These embossing protrusions satisfy the following characteristics: • The total area of ​​all embossed protrusions within a unit square decimeter accounts for 13-20% of the total area. • The area of ​​each embossed boss is 0.015-0.23 mm². 2 .

[0048] To facilitate understanding of the above features, further explanations are provided below. By elaborating on the parameter settings of "dot area and total area ratio" for the background pattern E, the core objective of the background pattern E is to address the pain points in embossing low-grammage thin base paper (8-20g / m²): poor forming effect (easy to puncture or blurry indentation), insufficient stiffness of the embossing structure (poor support leading to texture deformation and collapse), etc.

[0049] In this embodiment, the percentage (13-20%) of the total area of ​​micro-embossing dots per unit square decimeter is explained as follows: First, 'unit square decimeter' refers to each 1 dm² area (1 dm² = 100 cm²). Second, in the background pattern E within each square decimeter area, the sum of the areas of all micro-embossing dots accounts for 13-20% of the total area of ​​that square decimeter area. By setting the area percentage (13-20%) range to match the fiber distribution of low-basis-weight thin base paper 1A, 2A, 3A, and 4A—the pressure (pressure / area) at the tip of the embossing protrusion is 3-5 MPa (just enough to compress the fibers without piercing them), while the contact area of ​​the waist of the embossing protrusion (accounting for 60-70% of a single protrusion) fully adheres to the rubber roller (eliminating gaps), ensuring that the embossing dots are "both clear and complete."

[0050] Secondly, by using a dot area of ​​0.015-0.23mm for each micro-embossing point. 2 The method was used to calculate that the number of micro-embossing dots was approximately 5,652-133,333 / dm² (i.e., about 56-1333 / cm²). Because low-grammage thin base paper (1A, 2A, 3A, 4A) has low fiber content (8-20 g / m²) and a loose structure, it is easy for excessive pressure on a single embossing dot to cause puncture, or insufficient pressure to cause blurred indentations. Therefore, the dot area set in this embodiment is 0.015-0.23 mm². 2 Define the lower limit of the number of micro-embossing points per unit area (56 points / cm²) and the upper limit of the number of micro-embossing points per unit area (1333 points / cm²).

[0051] Specifically, when the area of ​​each micro-embossing dot is 0.23 mm 2 If the corresponding minimum number of micro-embossing dots per unit area is 56, then the distribution of these dots is "sparse large dots" (i.e., large area of ​​each dot and relatively sparse distribution). If the number of micro-embossing dots per unit area is less than 56 (e.g., 50), each micro-embossing dot will have to bear greater pressure (the total pressure is distributed among 50 dots → the pressure on each dot increases). Low-grammage thin base paper 1A, 2A, 3A, and 4A are easily punctured by the tips of the embossing protrusions due to their low fiber strength (breaking strength is only 20-30N).

[0052] Specifically, when the area of ​​each micro-embossed dot is 0.015 mm... 2If the maximum number of micro-embossed dots per unit area is 1333 / cm², then the paper exhibits "sparse large dots" (i.e., small area of ​​each dot and relatively dense distribution). If the number of micro-embossed dots per unit area is greater than 1333 / cm² (e.g., 1500 / cm²), the embossing protrusions are too densely distributed, the fibers between the micro-embossed dots are excessively squeezed, the paper's absorbency (e.g., the water absorption speed of tissue paper) decreases by 25%-30% (because the pores between fibers are closed by the embossed dots), and the softness decreases (EMTEC value < 70), which cannot meet the skin-friendly requirements of sanitary paper and cannot form clear and complete micro-embossed dots.

[0053] Therefore, the area of ​​the micro-embossed dots is 0.015-0.23 mm. 2 The combined effect of the area ratio (13-20%) ensures that the pressure of each embossing protrusion on the low-grammage thin base paper 1A, 2A, 3A, and 4A is dispersed (avoiding puncture) and concentrated (ensuring indentation), ultimately achieving the forming effect of "no puncture, no blurring, and uniform full coverage of embossing points".

[0054] In this embodiment, for regular and orderly pattern designs, the background pattern E of the pre-embossed base papers 1B, 2B, 3B, and 4B also satisfies the following characteristics: (3) The distance a between any two adjacent micro-embossing points in the same row is 0.2-0.95 mm; (4) The row spacing b between any two adjacent rows of micro-embossing dots is 0.2-0.95mm.

[0055] Furthermore, the direction of the aforementioned dot spacing a is parallel to the roller axis, and the direction of the row spacing b is parallel to the paper feeding direction.

[0056] Specifically, the dot spacing 'a' (0.2-0.95mm) is explained as follows: It refers to the lateral distance between any two adjacent micro-embossing dots in the same row. Since the thickness of low-basis-weight thin base paper is only 0.07-0.13mm (approximately 1 / 3 the thickness of ordinary A4 paper, with a loose fiber structure, poor rigidity, and weak tensile strength), its embossing quality highly depends on the stretching and shaping effect of the embossing protrusions on the fibers. The upper and lower limits (0.2-0.95mm) of the dot spacing 'a' (lateral distance between adjacent embossing dots) are essentially set to optimize the degree of fiber stretching and stress balance during the embossing process by adjusting the distribution density of the embossing protrusions, thus avoiding insufficient stretching (leading to blurred indentations) or excessive stretching (leading to fiber breakage) that affects product performance. Therefore, based on the implementation, the lower limit (a < 0.2mm) and upper limit (0.95mm) of the dot spacing 'a' are set. If the dot spacing a < 0.2mm (e.g., 0.15mm), the waist spacing between adjacent embossing bosses on the pre-embossing roller is too small (at this time, the waist width of the boss is 0.05-0.1mm). This causes the pre-pressing roller to deform under pressure and fail to completely fill the gap between the bosses, forming a "virtual gap". The virtual gap results in insufficient effective pressing depth of the embossing boss tip into the thin base paper. During the embossing process, the fibers need sufficient pressing depth to achieve plastic deformation of transverse stretching and longitudinal compression. When the pressing depth is insufficient, the tensile stress on the fibers does not reach the threshold for their orientation and cannot be fully unfolded and tightly filled into the embossed area. Ultimately, the fibers in the embossed area become loose due to insufficient stretching, failing to form a clear embossed outline, resulting in a blurred embossed area. If the dot spacing a > 0.95 mm (e.g., 1.0 mm), the waist distance between adjacent embossing bosses on the pre-embossing roller is too large. Although the pre-embossing roller can completely fill the gap, the bosses are sparsely distributed (only 10 points per 10 mm row), resulting in a lack of effective support points for the fibers in the unpressed area between the two bosses. During the embossing process, the thin base paper is subjected to continuous traction force as the roller rotates, and the fibers in the unpressed area are stretched simultaneously in the longitudinal direction (roller rotation direction) and the transverse direction (dot spacing direction). Due to the low support point density (1 support point / mm at a dot spacing of 1.0 mm, lower than 1.05 points / mm at 0.95 mm), the fiber tensile stress cannot be dispersed by the constraint of adjacent bosses. The local fiber stretching exceeds its elastic limit, ultimately causing the tensile stress to exceed the fiber's breaking strength, resulting in irreversible fiber breakage, manifested as local paper damage, holes, or edge tearing.

[0057] In summary, by setting the lower limit of the dot spacing a to 0.2mm and the upper limit to 0.95mm, the "appropriateness" of fiber stretching can be achieved. The core of this setting is to balance the stretching degree of low basis weight thin paper fibers by adjusting the distribution density of the embossing protrusions—ensuring that the fibers are fully stretched to shape the indentation, while avoiding excessive stretching that could lead to breakage, ultimately achieving an embossing effect with clear indentations and a complete structure.

[0058] Specifically, regarding the row spacing b (0.2-0.95mm): In low-basis-weight thin base paper (thickness 0.07-0.13mm), the longitudinal fibers exhibit a "closer arrangement" characteristic due to the papermaking process, resulting in significantly weaker tensile properties (longitudinal tensile strength 1.0-1.5kN / m) compared to the transverse fibers. The upper and lower limits (0.2-0.95mm) of the row spacing b (the distance between two adjacent longitudinal embossing points) are essentially set to match the tensile load-bearing capacity of the longitudinal fibers by adjusting the distribution density of the longitudinal embossing points—avoiding both localized overload caused by fiber stretching (manifested as uneven indentation depth) and excessive stretching due to insufficient tensile support (manifested as row misalignment or fiber breakage), ultimately achieving "uniform shaping" and "structural stability" of the longitudinal fibers. Therefore, when the row spacing b is less than 0.2mm (e.g., 0.18mm), the longitudinal embossing protrusions of the pre-embossing roller are too densely arranged, and the stretching effect area of ​​the fibers on the fibers of two adjacent rows of embossing protrusions overlaps (the longitudinal stretching effect radius is about 0.15-0.2mm). At this time, the longitudinal fibers are simultaneously subjected to the tensile stress of the upper and lower rows of embossing protrusions, forming a "superimposed stretching effect". Since the longitudinal fibers of low basis weight paper are densely arranged but have poor tensile strength, the superimposed stretching stress will cause local fiber segments (fibers between adjacent embossing points) to be subjected to tensile forces exceeding their elastic limits. Specifically, this manifests as differences in the amount of stretching in different areas of the longitudinal fibers (including overstretching and understretching), ultimately resulting in significant deviations in the embossing depth and an uneven background pattern. When the row spacing b is greater than 0.95mm (e.g., 1.3mm), the spacing between the longitudinal embossing bosses on the pre-embossing roller is too large (only 7-8 points within 10mm longitudinally). This causes the longitudinal fibers to form "long fiber free segments" (the length of fiber segments not fixed by embossing points is >0.5mm) between adjacent rows of embossing bosses. Due to the weak tensile strength of the longitudinal fibers in low-grammage paper, they are subjected to continuous longitudinal traction force as the roller rotates during the embossing process. At this time, the "long fiber free segments" are subjected to unrestrained excessive stretching due to the lack of mechanical fixation by the embossing bosses (support point density <0.8 points / mm), resulting in fiber breakage and fiber displacement. Specifically, this manifests as the offset of the embossing point position (row and column misalignment), accompanied by local fiber breakage, ultimately affecting the regularity of the background pattern.

[0059] In summary, by setting the lower limit of row spacing b to 0.2mm and the upper limit to 0.95mm, the stretching state of the longitudinal fibers can be precisely controlled. The essence of this setting is to adjust the distribution density of the longitudinal embossing points to adapt to the characteristics of the longitudinal fibers of low-grammage thin base paper, which are "closely arranged and have weak tensile strength". This avoids "uneven superimposed stretching" (inconsistent depth) caused by too small a spacing, and also prevents "insufficient support and excessive stretching" (row and column misalignment / breakage) caused by too large a spacing. Ultimately, it achieves uniform shaping and structural stability of the longitudinal fibers, ensuring the clarity and regularity of the embossing pattern.

[0060] In summary, the parameter settings for the background pattern E (dot spacing a: 0.2-0.95mm, line spacing b: 0.2-0.95mm, unit quantity 56-1333 / cm², area ratio per square decimeter 13-20%) are precisely optimized for the embossing characteristics of low-grammage paper. By setting the dot spacing a and line spacing b within these ranges, the core principle is to precisely control the tensile strength of the fibers by matching the "low rigidity and weak tensile strength" of the thin base paper. The lower limit of 0.2mm avoids "insufficient stretching" (dot spacing) or "stretch overlap" (line spacing) caused by excessively dense protrusions, ensuring sufficient fiber shaping. The upper limit of 0.95mm avoids "excessive stretching and breakage" (dot spacing) or "excessive stretch displacement" (line spacing) caused by excessively sparse protrusions, ensuring fiber structural stability. Ultimately, this achieves a high-quality embossing effect with clear indentations, regular patterns, and no breaks or damage. By synergistically managing the number and area ratio of micro-embossing dots within a unit square decimeter area, the contradiction between "concentrated embossing pressure" and "fragility of low-grammage paper" is balanced, ultimately achieving a high-density background effect with "clear forming and uniform pattern".

[0061] In this embodiment, each micro-embossing dot is a circular, elliptical, rhomboid, or polygonal structure with a planar dimension of 0.2×0.5-0.5×0.8mm (length×width) and a depth of 0.3-0.9mm (preferably 0.5mm), ensuring that the embossing dot has sufficient mechanical strength while avoiding puncturing the thin base paper.

[0062] To facilitate understanding of the above-mentioned multilayer thin base paper composite paper materials, the following explanations are provided in conjunction with different implementation examples. Implementation Case 1: See Appendix Figure 1-3 As shown, for ease of explanation, in this case, the thin base papers 2A and 3A are defined as needing to form a background pattern E, while the thin base papers 1A and 4A are surface layers that do not require a background pattern E. Specifically, the two sets of thin base papers 2A and 3A are pre-embossed by mechanical nesting to form embossed base papers 2B and 3B with a background pattern E. Then, the two pre-embossed layers of embossed base papers 2B and 3B are used as interlayers and sandwiched between the two sets of thin base papers 1A and 4A that have not been pre-embossed, so that the two sets of embossed base papers 2B and 3B and the two sets of thin base papers 1A and 4A are stacked to form a multi-layer paper web D (here, the multi-layer paper web D is composed of "1A-2B-3B-4A" in the stacking order). Because the micro-embossed dots of the background pattern E on the surface of the pre-embossed base paper 2B and 3B are delicate and soft to the touch, the laminated paper products can avoid the background pattern E showing through the surface layer. For consumers, there is no visual difference compared with traditional multi-layer paper products. There is no unevenness in the touch, and the overall characteristics are soft. At the same time, the paper products with the pre-embossed base paper 2B and 3B sandwiched in are more fluffy and thicker than the composite paper products of traditional multi-layer paper directly stacked.

[0063] Implementation Case 2: See Appendix Figure 4-6 As shown, for ease of explanation, the thin base papers 1A, 2A, 3A, and 4A in this case are defined as the embossed base papers 1B, 2B, 3B, and 4B that need to be embossed to form a background pattern E. Specifically, each of the thin base papers 1A, 2A, 3A, and 4A is pre-embossed to form embossed base papers 1B, 2B, 3B, and 4B with the background pattern E. Subsequently, the embossed base papers 1B, 2B, 3B, and 4B are combined and stacked to form multiple layers of paper web D. Visually, the background pattern E can be seen on both the front and back of the laminated paper product, presenting a delicate visual effect. Furthermore, because the micro-embossed dots of the background pattern E are delicate and soft to the touch without being abrupt, the overall product exhibits a soft characteristic. Secondly, the overall thickness of the laminated paper product is more fluffy and thicker than that of the first implementation case.

[0064] In summary, the above implementation case one or implementation case two uses four-channel thin base paper 1A, 2A, 3A, 4A as an example. However, in actual production, those skilled in the art can appropriately reduce the number of channels to three or increase it to five or more channels of thin base paper as needed. This belongs to the above-mentioned extended solutions, and its structure and principle are the same as those in the above implementation cases. They will not be elaborated here.

[0065] In this embodiment, see Appendix Figure 10 and 12 As shown, taking three-way thin base paper 1A, 2A, 3A and four-way thin base paper 1A, 2A, 3A, 4A as examples, each thin base paper is pre-embossed. After pre-embossing, each embossed base paper is divided into at least two pre-stacked paper webs 1C and 2C. Each pre-stacked paper web 1C and 2C contains at least one embossed base paper 1B, 2B, 3B, 4B. For ease of understanding, the following is combined with the appendix. Figure 12-13 The specific case shown is explained as follows: If one pre-stacked paper web 1C contains two embossed base papers 1B and 2B, and the other pre-stacked paper web 2C contains two embossed base papers 3B and 4B, then the two layers of embossed base papers 1B and 2B are first combined and stacked, and then mechanically nested and embossed to form pre-stacked paper web 1. Subsequently, it is combined and stacked with the other pre-stacked paper web 2C, and then mechanically nested and embossed a second time, ultimately causing the thin base papers 1A, 2A, 3A, and 4A to be composited to form multi-layered paper web D. Specifically, the above-mentioned process design of "pre-stacked paper webs 1C and 2C splitting → opposing stacking → mechanical nesting bonding" is for low-grammage thin base paper (8-20g / m²) glue-free lamination. Through the synergistic effect of "splitting pressure → opposing reinforcement nesting → multi-form bonding complementarity," it solves the problems of "easy delamination when directly stacked" and "insufficient bonding strength of a single bonding form" in traditional multi-layered paper materials.

[0066] For easier understanding, please refer to the appendix. Figure 12-13As shown, taking four thin base papers 1A, 2A, 3A, and 4A as an example, the branching scheme can be as follows: the first pre-stacked paper web 1C (containing two thin base papers 1A and 2A) and the second pre-stacked paper web 2C (containing two thin base papers 3A and 4A). The first pre-stacked paper web 1C first passes through a pair of stacking pressure rollers that are pressed tightly together (the two stacking pressure rollers can be any one or two of the following: rubber rollers, pattern rollers, and steel rollers; no specific restrictions are made here. In addition, to save costs, the composite pattern roller 21 can also serve as a stacking pressure roller. Only one stacking pressure roller needs to be set up for pressing and cooperating, which can also achieve the effect of one mechanical nesting embossing). At this time, the thin base papers 1A and 2A in the first pre-stacked paper web 1C that have undergone one mechanical nesting embossing not only combine together, but also form a stacked pattern F. Subsequently, the two pre-stacked paper webs 1C and 2C are stacked together and fed into the composite roller group 2 for further secondary mechanical nesting and embossing, so that the thin base papers (1A, 2A, 3A, 4A) are not only combined together, but also further form a stacked pattern F.

[0067] Therefore, by using the two mechanical nesting embossing methods described above, the embossing base papers 1B, 2B, 3B, and 4B are divided into at least two pre-stacked paper webs 1C and 2C (each pre-stacked paper web contains 1-2 embossing base papers). The first pre-stacked paper web 1C undergoes one mechanical nesting embossing process, and then merges with the second pre-stacked paper web 2C for a second mechanical nesting embossing process. Thus, by employing a process of "partial pre-stacking → overall stacking," the total number of layers is distributed across different pre-stacked paper webs 1C and 2C (as in the example above with 4 layers of embossing base papers 1B, 2B, and 3B). The 4B pre-stacked paper web is divided into two paths, each containing two layers of embossed base paper. Each path only needs to process 1-2 layers of thin base paper in a localized stacking, thus effectively dispersing pressure and controlling displacement error. That is, the number of layers in each path of pre-stacked paper web 1C and 2C is small (1-2 layers), the linear pressure during local stacking is smaller (only 50%-60% of the overall stacking), avoiding damage to low-grammage thin base paper due to excessive pressure, and the paper path of thin base paper in each path is short (only 1-2 paths need to be aligned), resulting in smaller lateral displacement error, laying the foundation for accurate alignment of the subsequent overall stacking.

[0068] In this embodiment, at least two pre-stacked paper webs 1C and 2C converge in an opposing stacking manner, causing the micro-embossing dots of two adjacent embossed base papers 2B and 3B in the opposing stacked pre-stacked paper webs 1C and 2C to form one or a combination of the following bonding forms: (1) The outer bottom surfaces of the micro-embossing dots of the two adjacent embossing base papers 2B and 3B are fully or partially in contact and bonded, that is: the convex surface of the micro-embossing dots of the upper embossing base paper 2B and the convex surface of the micro-embossing dots of the lower embossing base paper 3B are arranged opposite to each other, presenting a "point-to-point" bonding form.

[0069] (2) The micro-embossing points of the two adjacent embossing base papers 2B and 3B are not nested with each other, and the micro-embossing points of one embossing base paper 2B do not contact or adhere to the non-embossed plane area of ​​the other embossing base paper 3B. That is, the convex surface of the embossing point of the upper embossing base paper 2B should avoid embedding into the non-embossed plane area of ​​the embossing base paper 3B as much as possible.

[0070] By using the aforementioned bonding methods 1 and 2 of micro-embossing points between the two pre-stacked paper webs, it is ensured that each pre-stacked paper web 1C and 2C can still maintain sufficient stiffness and thickness after being laminated.

[0071] In this embodiment, in the pre-stacked paper webs 1C and 2C having multiple embossed base papers 1B, 2B, 3B, and 4B, the micro-embossing dots of any two adjacent embossed base papers 1B, 2B, 3B, and 4B form the following bonding pattern: (1) The micro-embossing points of two adjacent embossing base papers (1B and 2B, or 3B and 4B) are raised in the same direction, and the micro-embossing points of one embossing base paper 1B and 3B are completely or partially misaligned with the micro-embossing points of the other embossing base paper 2B and 4B, so that the bottom surface of the micro-embossing points of the upper embossing base paper 1B and 3B is in contact with the non-embossed plane area of ​​the lower embossing base paper 2B and 4B. That is, the convex surface of the embossing points of the upper thin base paper 1B / 3B should avoid embedding into the non-embossed plane area of ​​the lower thin base paper 2B / 3B as much as possible.

[0072] By using the bonding method 1 of the micro-embossing points between the various embossed base papers 2B and 3B in the same pre-stacked paper web 1C and 2C, it is ensured that the pre-stacked paper web can still maintain sufficient stiffness and thickness after the thin base papers are composited to form the pre-stacked paper web.

[0073] In summary, by employing a "pre-embossing-pre-lamination-glue-lamination" process for various thin base papers 1A, 2A, 3A, and 4A, a multi-layered paper web D with a "full-coverage background pattern E + partial lamination pattern F" is obtained. This solves the interlayer bonding problem in low-grammage thin base paper lamination. The resulting composite paper material possesses greater overall thickness, a more fluffy structure, and a smoother, more delicate feel. Simultaneously, the application of low-grammage raw materials significantly reduces production costs, achieving high cost-effectiveness and providing key technological support for the leapfrog development of paper materials towards "lightweight, functional, and environmentally friendly" directions.

[0074] To facilitate understanding of the composite paper materials described above, the following explanations are provided in conjunction with specific implementation examples.

[0075] Implementation Case 3: See Appendix Figure 10 and 11 As shown, three thin base paper is used, defined as the first thin base paper 1A, the second thin base paper 2A, and the third thin base paper 3A.

[0076] Thin base paper parameters: Three-way thin base paper, all with a basis weight of 9g / m² and a thickness of 0.07mm.

[0077] Pre-embossing process: Three sets of embossing rollers 1 mechanically nest and pre-emboss three thin base papers to form three embossed base papers 1B, 2B, and 3B. Each embossed base paper 1B, 2B, and 3B forms a background pattern E composed of several evenly distributed micro-embossing dots. The characteristics of the background pattern E are: the plane area of ​​the micro-embossing dots is 0.17 mm², the depth is 0.5 mm; the dot spacing a of the background pattern E is 0.80 mm, the row spacing b is 0.50 mm, the number of micro-embossing dots per unit area is 76 / cm² (i.e., 7,600 dots / dm²), and the area ratio of micro-embossing dots per unit area is 13%.

[0078] Pre-lamination process: The three embossing base papers 1B, 2B, and 3B are divided into two pre-lamination paper webs 1C and 2C (the first pre-lamination paper web 1C includes embossing base paper 1B and embossing base paper 2B, and the second pre-lamination paper web 2C includes embossing base paper 3B). The embossing base paper 1B and embossing base paper 2B of the first pre-lamination paper web 1C are first combined and laminated and then subjected to a mechanical nesting embossing process.

[0079] Composite process: Two pre-stacked paper webs 1C and 2C are fed into composite roller group 2 for secondary mechanical nesting composite, ultimately forming a multi-layered paper web D with a local stacked pattern F.

[0080] Performance characteristics: The base pattern E and the layered pattern F are clear and complete, the composite does not delaminate, the tensile strength (transverse) is 1.5kN / m, the softness (EMTEC) is 85, the thickness retention rate (500g static pressure for 30 seconds) is 82%, and the anti-delamination strength is 0.55N / 15mm.

[0081] Implementation Case 4: See Appendix Figure 12 and 13 As shown, four thin base paper is used, defined as the first thin base paper 1A, the second thin base paper 2A, the third thin base paper 3A, and the fourth thin base paper 4A.

[0082] Thin base paper parameters: four-way thin base paper, grammage 10g / m², 10g / m², 10g / m², 10g / m², thickness 0.07-0.075mm.

[0083] Pre-embossing process: Four sets of embossing rollers 1 mechanically nest and pre-emboss four thin base papers to form four embossed base papers 1B, 2B, 3B, and 4B. Each embossed base paper 1B, 2B, 3B, and 4B forms a background pattern E composed of several uniformly distributed micro-embossing dots. The characteristics of the background pattern E are: the plane size of the micro-embossing dots is 0.4×0.5mm (area is 0.2mm²), and the depth is 0.5mm; the dot spacing a of the background pattern E is 0.80mm, the row spacing b is 0.57mm, the number of micro-embossing dots per unit area is 80 / cm² (8000 / dm²), and the area ratio of micro-embossing dots per unit area is 16%.

[0084] Pre-lamination process: The four thin base paper is divided into two pre-lamination paper webs 1C and 2C (the first pre-lamination paper web 1C includes the first thin base paper 1A and the second thin base paper 2A, and the second pre-lamination paper web includes the third thin base paper 3A and the fourth thin base paper 4A). The first thin base paper 1A and the second thin base paper 2A of the first pre-lamination paper web are first merged and laminated and then mechanically nested and embossed once.

[0085] Composite process: Two pre-stacked paper webs 1C and 2C are fed into composite roller group 2 for secondary mechanical nesting composite to form a multi-layered paper web D with local stacked pattern F.

[0086] Performance characteristics: The base pattern E and the layered pattern F are clear and complete, the composite does not delaminate, the tensile strength (transverse) is 1.8kN / m, the softness (EMTEC) is 90, the thickness retention rate (500g static pressure for 30 seconds) is 85%, and the anti-delamination strength is 0.62N / 15mm.

[0087] Comparative example: Two sets of base paper, each with a basis weight of 24 g / m², and 40 micro-embossing dots per square centimeter. The two sets of thin base paper are directly stacked and laminated only by point-to-flat bonding. Performance: tensile strength (transverse) 1.0 kN / m, softness (EMTEC) 70, thickness retention (500g static pressure for 30 seconds) 65%, and delamination resistance 0.3 N / 15 mm.

[0088] By comparing the implementation cases three and four with the comparative examples, it can be seen that the composite paper material of this utility model is significantly superior to the prior art in key performance aspects such as interlayer bonding strength, softness, and thickness retention. The specific performance comparison table is as follows: Implementation Case 5: See Appendix Figure 14 and 15As shown, four thin base papers are used, defined as the first thin base paper 1A, the second thin base paper 2A, the third thin base paper 3A, and the fourth thin base paper 4A. All four thin base papers 1A, 2A, 3A, and 4A need to form a background pattern E. Among them, thin base papers 2A, 3A, and 4A form the background pattern E through pre-embossing treatment, while thin base paper 1A is embossed by a pre-set layered pressure roller and a composite pattern roller 21 in a mechanical nesting embossing method with a relatively better embossing effect, so as to simultaneously form the background pattern E and the layered pattern F.

[0089] Specifically, this implementation case five adopts an appendix. Figure 14 The embossing apparatus shown in the diagram involves pre-embossing thin base papers 2A, 3A, and 4A through embossing roller group 1 to form embossed base papers 2B, 3B, and 4B with a background pattern E. Thin base paper 1A is then embossed through a stacking pressure roller and a composite embossing roller 21 to form embossed base paper 1B with a background pattern E and a stacked pattern F. Subsequently, the pre-embossed embossed base papers 2B, 3B, and 4B, along with the embossed base paper 1B, are fed into the space between the composite embossing roller 21 and the composite rubber roller. The composite embossing roller 21 has high-pressure embossing bosses with varying heights and low... The embossing boss, in conjunction with the composite back roller 22, embosses the stacked thin base paper 1A and embossing base papers 2B, 3B, and 4B to form a partial stacked pattern F. Meanwhile, the low embossing boss, in conjunction with the composite embossing roller 21 and the composite rubber roller, embosses the thin base paper 1A to form an embossing base paper 1B with a background pattern E. Finally, a multi-layered paper web D is formed by four embossing base papers 1B, 2B, 3B, and 4B. Using this method, the overall equipment cost is lower and the economy is better. It can save a set of embossing rollers 1, and the texture pattern of the multi-layered paper web D after embossing is clearer and more complete.

[0090] Implementation Case Six: See Appendix Figure 16 and 17 As shown, four thin base papers are used, defined as the first thin base paper 1A, the second thin base paper 2A, the third thin base paper 3A, and the fourth thin base paper 4A. All four thin base papers 1A, 2A, 3A, and 4A need to form a background pattern E. Among them, the first thin base paper 1A and the second thin base paper 2A share the same embossing roller group 1, and the third thin base paper 3A and the fourth thin base paper 4A share the same embossing roller group 1. That is, the thin base paper 1A and the thin base paper 2A are first stacked and pre-embossed to form embossed base papers 1B and 2B with background pattern E, and the thin base paper 3A and the thin base paper 4A are first stacked and pre-embossed to form embossed base papers 3B and 4B with background pattern E. Next, the four layers of embossed base paper 1B, 2B, 3B, and 4B, after pre-embossing, are combined and embossed at the gap between the embossing roller 21 and the back roller 2, thereby forming a multi-layered paper web D with a layered pattern F by combining the embossed base paper 1B, 2B, 3B, and 4B. Using this method, the overall equipment cost is lower and the economic efficiency is better.

[0091] In summary, in any of the above implementation examples, the thin base paper 1A, 2A, 3A, and 4A can be composed of a single layer, two layers, or more. Those skilled in the art can appropriately select the number of thin base paper layers based on the actual product or papermaking process. As long as the basis weight meets the basic condition of 8-20 g / m² for low-basis-weight paper, the synergistic forming of pre-embossing and composite embossing can be achieved, ensuring that the background pattern E and the layered pattern F are distinct, three-dimensional, and soft to the touch in the multi-layer paper web D. Secondly, the embossing protrusions between the pre-embossing rollers 21 of different embossing roller groups 1 can be designed with different sizes, resulting in differences in the size of the protrusions in the background pattern E of the embossed base paper formed by each embossing roller group 1. In particular, the protrusion size of the background pattern E of the embossed base paper used as the interlayer is slightly larger than that of the surface embossed base paper. This effectively improves the support and bulkiness of the composite multi-layer paper web D without affecting the surface flatness and tactile comfort of the multi-layer paper web D.

[0092] The embodiments described above are merely preferred embodiments of this utility model and are not intended to limit the utility model in any way. Any modifications or alterations made by those skilled in the art to the technical solution of this utility model without departing from its scope are equivalent embodiments of this utility model. Therefore, all equivalent changes made based on the concept of this utility model without departing from its scope should be covered within the protection scope of this utility model.

Claims

1. A multilayer thin base paper composite paper material, comprising at least two layers of thin base paper (1A, 2A, 3A, 4A), characterized in that: At least two of the aforementioned thin base papers (1A, 2A, 3A, 4A) are pre-embossed using mechanical nesting to form at least two embossed base papers (1B, 2B, 3B, 4B) with a background pattern (E), wherein the background pattern (E) is composed of a plurality of micro-embossing dots; subsequently, the pre-embossed base papers (1B, 2B, 3B, 4B) are combined and stacked to form a multi-layer paper web (D), wherein the background pattern (E) of the embossed base papers (1B, 2B, 3B, 4B) satisfies the following characteristics: • The total area of ​​all micro-embossing points within a unit square decimeter accounts for 13-20% of the total area. • The area of ​​each micro-embossed dot is 0.015-0.23 mm. 2 .

2. The multilayer thin base paper composite paper material according to claim 1, characterized in that: After pre-embossing, the embossed base paper (1B, 2B, 3B, 4B) is also combined with the un-pre-embossed thin base paper (1A, 2A, 3A, 4A) to form a multi-layer paper web (D).

3. The multilayer thin base paper composite paper material according to claim 1, characterized in that: The background pattern (E) of the embossed base paper (1B, 2B, 3B, 4B) also satisfies the following characteristics: • The distance (a) between any two adjacent micro-embossing dots in the same row is 0.2-0.95 mm; • The row spacing (b) between any two adjacent rows of micro-embossed dots is 0.2-0.95 mm.

4. The multilayer thin base paper composite paper material according to claim 1, characterized in that: The basis weight of each of the thin base papers (1A, 2A, 3A, 4A) is 8-20 g / m²; the depth of each of the micro-embossing dots is 0.3-0.9 mm.

5. The multilayer thin base paper composite paper material according to claim 1, characterized in that: The embossed base papers (1B, 2B, 3B, 4B) are laminated by mechanical nesting to form a multi-layer paper web (D), wherein the multi-layer paper web (D) is partially embossed to form a layered pattern (F).

6. The multilayer thin base paper composite paper material according to claim 1, characterized in that: The embossed base paper (1B, 2B, 3B, 4B) and thin base paper (1A, 2A, 3A, 4A) are laminated by mechanical nesting to form a multi-layer paper web (D), wherein the multi-layer paper web (D) is partially embossed. Layered pattern (F) .

7. The multilayer thin base paper composite paper material according to claim 2, characterized in that: At least two pre-embossed base papers (2B, 3B) are used as interlayers and sandwiched between two un-pre-embossed thin base papers (1A, 4A), thereby stacking the embossed base papers (2B, 3B) and the thin base papers (1A, 4A) to form a multi-layer paper web (D).

8. The multilayer thin base paper composite paper material according to claim 1, characterized in that: Each of the embossed base papers (1B, 2B, 3B, 4B) is pre-embossed to form a background pattern (E), and then the embossed base papers (1B, 2B, 3B, 4B) are combined and stacked to form a multi-layered paper web (D).

9. The multilayer thin base paper composite paper material according to claim 8, characterized in that: After pre-embossing, each of the embossed base papers (1B, 2B, 3B, 4B) is divided into at least two pre-stacked paper webs (1C, 2C). Each of the pre-stacked paper webs (1C, 2C) contains at least one embossed base paper (1B, 2B, 3B, 4B). One of the pre-stacked paper webs (1C) is first mechanically nested and embossed once, and then merged and stacked with other pre-stacked paper webs (2C) for a second mechanical nesting and embossing process, thereby making each of the thin base papers (1A, 2A, 3A, 4A) composite to form a multi-layered paper web (D).

10. The multilayer thin base paper composite paper material according to claim 9, characterized in that: At least two of the pre-stacked paper webs (1C, 2C) converge in an opposing stacking manner, causing the micro-embossing dots of the two adjacent layers of embossed base paper (2B, 3B) in the opposing stacked pre-stacked paper webs (1C, 2C) to form one or a combination of the following bonding forms: • The outer bottom surfaces of the micro-embossing dots of two adjacent embossed base papers (2B, 3B) are fully or partially in contact and bonded; • The micro-embossing points of the two adjacent embossing base papers (2B, 3B) are not nested with each other, and the micro-embossing points of one embossing base paper (2B) do not contact or adhere to the non-embossed plane area of ​​the other embossing base paper (3B).

11. The multilayer thin base paper composite paper material according to claim 9, characterized in that: In the multi-layer paper web (D) having multiple embossed base papers (1B, 2B, 3B, 4B), the micro-embossing dots of any two adjacent embossed base papers (1B, 2B, 3B, 4B) form the following bonding pattern: • The micro-embossing dots of two adjacent embossing base papers (1B, 2B, 3B, 4B) protrude in the same direction, and the micro-embossing dots of one embossing base paper (1B, 3B) are completely or partially misaligned with the micro-embossing dots of the other embossing base paper (2B, 4B), so that the bottom surface of the micro-embossing dots of the upper embossing base paper (1B, 3B) is in contact with and adhered to the non-embossed plane area of ​​the lower embossing base paper (2B, 4B).

12. A pre-pressing roller, characterized in that: Includes a pre-embossing roller (12) adapted to the multilayer thin base paper composite paper material according to any one of claims 1-11, wherein the roller surface of the pre-embossing roller (12) has a plurality of embossing protrusions that match the background pattern (E) of the embossing base paper (1B, 2B, 3B, 4B), and the embossing protrusions satisfy the following characteristics: • The total area of ​​all embossed protrusions within a unit square decimeter accounts for 13-20% of the total area. • The area of ​​each embossed boss is 0.015-0.23 mm². 2 .

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