High folding endurance special paper and its preparation method and application

Abstract

The application discloses a kind of high folding resistance special paper and its preparation method, utilize the cellulose nanofilament with unique nanometer scale structure, high specific surface area, super high length-diameter ratio as the reinforcing material of cotton pulp fiber, simultaneously utilize pulp screening reorganization technology to realize the accurate regulation of cotton pulp fiber length distribution, optimize fiber distribution interval span, improve the uniformity and the rate of whisk of pulp, while guaranteeing the dewatering and water retention effect of pulp, overcome the problems such as the wide range of traditional cotton pulp fiber length distribution, the poor flexibility caused by the serious damage of fiber strength and the low folding resistance of cotton fiber paper, significantly improve the mechanical strength and flexibility of special paper, and can be applied in the field of high durability and folding strength requirement such as paper money, securities, map, chart paper and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of nanofiber and papermaking, and particularly relates to a high folding resistance special paper and a preparation method and application thereof. BACKGROUND

[0002] Paper, as a flexible material with a three-dimensional (3D) porous structure, is widely used in culture, packaging, printing and people's daily life. The mechanical strength of paper is of great significance to its application scenarios and service life, especially in cases requiring extremely high strength and ultra-long durability. Generally, the mechanical strength of paper includes tensile, tear, burst and folding resistance. Among these strength properties, folding resistance is the only strength test that measures the durability of paper under repeated or rough handling, representing the number of times the paper can be repeatedly folded before losing sufficient tensile strength and breaking. Therefore, compared with other strength tests, folding resistance is more sensitive to the flexibility of paper and will decrease significantly with the use or aging of paper.

[0003] In some special papers that will be repeatedly processed or may be repeatedly folded during use, such as banknotes, securities, maps, charts, etc., extremely high folding resistance is particularly required. These special papers are generally made of cotton fibers with longer length, higher strength and toughness to ensure high folding resistance and long-lasting durability. However, due to the large angle (about 45°) and spiral cross arrangement of the microfibers on the cell wall of cotton fibers with the fiber main shaft, it is difficult to essentially improve the uniformity of the pulp under the given combination of existing beating equipment and process, the fiber floc rate is difficult to improve, the beating energy consumption is high, the fiber length distribution range of the obtained pulp is wide, the fiber strength is severely damaged, leading to poor flexibility, which greatly affects the folding resistance and use effect of cotton fiber paper. In the papermaking industry, chemical enhancers or surface sizing are usually added to improve the folding resistance of paper, but this increases the production process flow and cost of paper. Therefore, it is of great significance to develop special paper with high folding resistance and its preparation technology, which can effectively improve the service ability and life of traditional cellulose special paper, improve the product grade, and meet the requirements of high-end field applications. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application provides a high folding resistance special paper and a preparation method and application thereof to overcome the problems of poor folding resistance, low strength and short service life of cotton fiber paper caused by the difficulty in beating and floc of cotton fibers, high beating energy consumption, wide fiber length distribution range of cotton fiber pulp, severe damage to fiber strength and poor flexibility.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A preparation method of a high folding resistance special paper, comprising the following steps:

[0007] S1: Screening the refined cotton linter pulp according to fiber length to obtain graded cotton pulp;

[0008] The graded cotton pulp is divided into F1 short-fiber cotton pulp, F2 medium-short-fiber cotton pulp, F3 medium-long-fiber cotton pulp and F4 long-fiber cotton pulp;

[0009] S2: reconstitute the graded cotton pulp according to a preset weight ratio and evaluate it according to the reconstitution standard. If the evaluation is qualified, the reconstituted cotton pulp is obtained. If it is unqualified, S2 is repeated until the evaluation is qualified.

[0010] S3: The recombinant cotton pulp and cellulose nanofibrils are mixed in proportion, and then filtered, pressed and dried to obtain high folding-resistant specialty paper.

[0011] Furthermore, the fiber length of the F1 short fiber cotton pulp is 0.1mm-0.3mm, the fiber length of the F2 medium-short fiber cotton pulp is 0.3mm-0.6mm, the fiber length of the F3 medium-long fiber cotton pulp is 0.6mm-1.2mm, and the fiber length of the F4 long fiber cotton pulp is 1.2mm-1.7mm.

[0012] Furthermore, in S2, the preset weight ratio is F1 short fiber cotton pulp: F2 medium short fiber cotton pulp: F3 medium long fiber cotton pulp: F4 long fiber cotton pulp = (40 parts to 60 parts): (10 parts to 30 parts): (5 parts to 25 parts): (5 parts to 20 parts).

[0013] Furthermore, in S2, the preset weight portions are 100 portions in total.

[0014] Furthermore, in S2, the reorganization standard includes average fiber length and beating degree.

[0015] Furthermore, the average length of the fibers is 0.8 mm to 0.9 mm, and the beating degree is 55°SR to 65°SR.

[0016] Furthermore, in S3, the recombinant cotton pulp and the cellulose nanofibrils are mixed in a mass ratio of (90-98):(2-10).

[0017] Furthermore, in S3, the cellulose nanofibrils have a length of 200 μm to 500 μm, a diameter of 20 nm to 100 nm, and an aspect ratio of 2000 to 5000.

[0018] A high folding resistance specialty paper is obtained by using the above-mentioned method for preparing a high folding resistance specialty paper, wherein the basis weight of the high folding resistance specialty paper is 80g / m 2 ~100g / m 2, tensile strength is 65N / cm~90N / cm, and folding endurance is 2400 times~3800 times.

[0019] A high-folding-resistance specialty paper used in banknotes, securities, maps, and nautical charts.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] The present invention provides a method for preparing special paper with high folding resistance. The method utilizes pulp screening and reorganization technology to achieve precise control of the length distribution of cotton pulp fibers, optimize the span of the fiber distribution range, improve the uniformity and brooming rate of the pulp, and ensure the water filtration and water retention effects of the pulp. The method overcomes the problems of traditional cotton pulp with a wide fiber length distribution range, severe damage to fiber strength resulting in poor flexibility, low folding resistance, low strength and short service life of cotton fiber paper, etc.

[0022] Furthermore, the present invention utilizes cellulose nanofibrils with a unique nanoscale structure, high specific surface area and ultra-high aspect ratio (>2000) as a reinforcing material for cotton pulp fibers, giving full play to the excellent interweaving and web-forming ability of cellulose nanofibrils, so that the specialty paper can achieve stress transmission, transfer and dissipation through the orientation and deflection of nanofibers at the cracks when subjected to external force stretching or repeated folding, thereby improving the overall flexibility and folding strength of the paper.

[0023] The invention provides a high folding resistance special paper, which has excellent mechanical strength and flexibility, and can meet the demand for high strength, high flexibility and aging resistance materials. The basis weight of the high folding resistance special paper is 80g / m 2 ~100g / m 2 , tensile strength is 65N / cm~90N / cm, and folding endurance is 2400 times~3800 times.

[0024] The application of the high folding-resistance specialty paper provided by the present invention in specialty paper can be applied to specialty papers with high requirements for durability and folding strength, such as banknotes, securities, maps, nautical charts and other fields. It can solve the technical difficulties currently existing in the high-value application of cellulose-based materials, and has broad application prospects in the fields of specialty paper and composite material reinforcement. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings in the specification are used to provide further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0026] Figure 1 This is a schematic diagram of the preparation process of the present invention. DETAILED DESCRIPTION

[0027] The present invention is described in further detail below:

[0028] A high-folding-resistance specialty paper is prepared by mixing recombinant cotton pulp with an average fiber length of 0.8 mm to 0.9 mm and a beating degree of 55°SR to 65°SR with cellulose nanofibrils with a length of 200 μm to 500 μm, a diameter of 20 nm to 100 nm, and an aspect ratio of 2000 to 5000 in a mass ratio of (90-98): (2-10); the basis weight of the high-folding-resistance specialty paper is 80 g / m 2 ~100g / m 2 The tensile strength is 65N / cm~90N / cm, the tear strength is 2400-3800 times, and it can be used in special papers with high requirements on durability and folding strength, such as banknotes, securities, maps, nautical charts and other fields.

[0029] A method for preparing high-folding-resistance specialty paper comprises the following steps:

[0030] Step 1: Using a screening instrument, the beaten cotton linter pulp with a beating degree of 55°SR to 65°SR, an average fiber length of 0.8mm to 0.9mm, and a length distribution range of 0.1mm to 1.7mm is screened, and the fibers are grouped according to the fiber length as follows: F1 short fibers (0.1mm to 0.3mm), F2 medium short fibers (0.3mm to 0.6mm), F3 medium long fibers (0.6mm to 1.2mm), and F4 long fibers (1.2mm to 1.7mm), to obtain graded cotton pulp;

[0031] Step 2: reconstitute the graded cotton pulp obtained in step 1 according to the following proportions: the weight proportions of F1-F4 are 40-60 parts: 10-30 parts: 5-25 parts: 5-20 parts, respectively, and the total weight proportions of the reconstituted cotton pulp are 100 parts. Then, the average length and beating degree of the reconstituted cotton pulp are evaluated. The average fiber length that needs to be met is 0.8 mm to 0.9 mm, and the beating degree is 55°SR to 65°SR, to obtain reconstituted cotton pulp;

[0032] Step 3: The recombinant cotton pulp obtained in step 2 is mixed with cellulose nanofibrils in a mass ratio of (90-98): (2-10), and high folding-resistant special paper is obtained through processes such as filtering, forming, pressing, and drying.

[0033] The present invention will be described in detail below with reference to the embodiments. It should be noted that, unless there is a conflict, the embodiments and features in the embodiments of the present application can be combined with each other.

[0034] The following detailed description is the description of the embodiments, and is intended to provide further detailed description of the present invention. Unless otherwise indicated, all technical terms adopted in the present invention have the same meaning as those generally understood by those skilled in the art of the application. The terms used in the present invention are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present invention.

[0035] Example 1

[0036] A method for preparing high-folding-resistance specialty paper comprises the following steps:

[0037] Step 1: Using a screening instrument, the beaten cotton linter pulp with a beating degree of 55°SR, an average fiber length of 0.9 mm, and a length distribution range of 0.1-1.7 mm is screened and grouped according to the fiber length as follows: F1 short fiber (0.1-0.3 mm), F2 medium short fiber (0.3-0.6 mm), F3 medium long fiber (0.6-1.2 mm), F4 long fiber (1.2-1.7 mm), to obtain graded cotton pulp;

[0038] Step 2: The graded cotton pulp obtained in step 1 is recombined according to the following proportions: the weight parts of F1-F4 are 40 parts: 15 parts: 25 parts: 20 parts, respectively, and the total weight parts of the recombined are 100 parts. The average length and beating degree are then evaluated. The average fiber length is 0.9 mm and the beating degree is 55°SR, which meets the conditions, thereby obtaining recombined cotton pulp;

[0039] Step 3: The recombinant cotton pulp obtained in step 2 is mixed with cellulose nanofibrils in a mass ratio of 98:2, and the high-folding-resistance special paper is obtained through processes such as filtering, forming, pressing, and drying.

[0040] A high-folding-resistance specialty paper prepared in Example 1 is prepared by mixing recombinant cotton pulp with an average length of 0.8-0.9 mm and a beating degree of 55°SR to 65°SR with cellulose nanofibrils with a length of 200-500 μm, a diameter of 20-100 nm, and an aspect ratio of 2000-5000 in a mass ratio of 98:2; the basis weight of the high-folding-resistance specialty paper is 80 g / m 2 The tensile strength is 65N / cm, the tear strength is 2400 times, and the folding endurance is 2400 times. It can be used in special papers with high requirements on durability and folding strength, such as banknotes, securities, maps, nautical charts and other fields.

[0041] Example 2

[0042] A method for preparing high-folding-resistance specialty paper comprises the following steps:

[0043] Step 1: Using a screening instrument, the beaten cotton linter pulp with a beating degree of 58°SR, an average fiber length of 0.87 mm, and a length distribution range of 0.1-1.7 mm is screened and grouped according to the fiber length as follows: F1 short fiber (0.1-0.3 mm), F2 medium short fiber (0.3-0.6 mm), F3 medium long fiber (0.6-1.2 mm), F4 long fiber (1.2-1.7 mm), to obtain graded cotton pulp;

[0044] Step 2: The graded cotton pulp obtained in step 1 is recombined according to the following proportions: the weight parts of F1-F4 are 54 parts: 17 parts: 18 parts: 11 parts, respectively, and the total weight parts of the recombined are 100 parts. The average length and beating degree are then evaluated. The average fiber length is 0.83 mm and the beating degree is 57°SR, which meets the conditions, thereby obtaining recombined cotton pulp;

[0045] Step 3: The recombinant cotton pulp obtained in step 2 is mixed with cellulose nanofibrils in a mass ratio of 96:4, and the high folding-resistant special paper is obtained through processes such as filtering, forming, pressing, and drying.

[0046] A high-folding-resistance specialty paper prepared in Example 2 is prepared by mixing recombinant cotton pulp with an average fiber length of 0.8-0.9 mm and a beating degree of 55°SR to 65°SR with cellulose nanofibrils with a length of 200-500 μm, a diameter of 20-100 nm, and an aspect ratio of 2000-5000 in a mass ratio of 96:4; the basis weight of the high-folding-resistance specialty paper is 86 g / m 2 The tensile strength is 73N / cm, the tear strength is 2720 times, and it can be used in special papers with high requirements on durability and folding strength, such as banknotes, securities, maps, nautical charts and other fields.

[0047] Example 3

[0048] A method for preparing high-folding-resistance specialty paper comprises the following steps:

[0049] Step 1: Using a screening instrument, the beaten cotton linter pulp with a beating degree of 60°SR, an average fiber length of 0.87 mm, and a length distribution range of 0.1-1.7 mm is screened and grouped according to the fiber length as follows: F1 short fiber (0.1-0.3 mm), F2 medium short fiber (0.3-0.6 mm), F3 medium long fiber (0.6-1.2 mm), F4 long fiber (1.2-1.7 mm), to obtain graded cotton pulp;

[0050] Step 2: The graded cotton pulp obtained in step 1 is recombined according to the following proportions: the weight parts of F1-F4 are 56 parts: 20 parts: 15 parts: 9 parts, respectively, and the total weight parts of the recombined are 100 parts. The average length and beating degree are then evaluated. The average fiber length is 0.85 mm and the beating degree is 59°SR, which meets the conditions, thereby obtaining recombined cotton pulp;

[0051] Step 3: The recombinant cotton pulp obtained in step 2 is mixed with cellulose nanofibrils in a mass ratio of 95:5, and the high folding-resistant special paper is obtained through processes such as filtering, forming, pressing, and drying.

[0052] A high-folding-resistance specialty paper prepared in Example 3 is prepared by mixing recombinant cotton pulp with an average fiber length of 0.8-0.9 mm and a beating degree of 55°SR-65°SR with cellulose nanofibrils with a length of 200-500 μm, a diameter of 20-100 nm, and an aspect ratio of 2000-5000 in a mass ratio of 95:5; the basis weight of the high-folding-resistance specialty paper is 90 g / m 2 The tensile strength is 78N / cm, the tear strength is 3152 times, and the folding endurance is 3152 times. It can be used in special papers with high requirements on durability and folding strength, such as banknotes, securities, maps, nautical charts and other fields.

[0053] Example 4

[0054] A method for preparing high-folding-resistance specialty paper comprises the following steps:

[0055] Step 1: Using a screening instrument, the beaten cotton linter pulp with a beating degree of 62°SR, an average fiber length of 0.83 mm, and a length distribution range of 0.1-1.7 mm is screened and grouped according to the fiber length as follows: F1 short fiber (0.1-0.3 mm), F2 medium short fiber (0.3-0.6 mm), F3 medium long fiber (0.6-1.2 mm), F4 long fiber (1.2-1.7 mm), to obtain graded cotton pulp;

[0056] Step 2: The graded cotton pulp obtained in step 1 is recombined according to the following proportions: the weight parts of F1-F4 are 49 parts: 30 parts: 11 parts: 10 parts, respectively, and the total weight parts of the recombined are 100 parts. The average length and beating degree are then evaluated. The average fiber length is 0.84 mm and the beating degree is 60°SR, which meets the conditions, thereby obtaining recombined cotton pulp;

[0057] Step 3: The recombinant cotton pulp obtained in step 2 is mixed with cellulose nanofibrils in a mass ratio of 93:7, and the high folding-resistant special paper is obtained through processes such as filtering, forming, pressing, and drying.

[0058] A high-folding-resistance specialty paper prepared in Example 4 is prepared by mixing recombinant cotton pulp with an average fiber length of 0.8-0.9 mm and a beating degree of 55°SR-65°SR with cellulose nanofibrils with a length of 200-500 μm, a diameter of 20-100 nm, and an aspect ratio of 2000-5000 in a mass ratio of 93:7; the basis weight of the high-folding-resistance specialty paper is 93 g / m 2 The tensile strength is 87N / cm, the tear strength is 3350 times, and the folding endurance is 3350 times. It can be used in special papers with high requirements on durability and folding strength, such as banknotes, securities, maps, nautical charts and other fields.

[0059] Example 5

[0060] A method for preparing high-folding-resistance specialty paper comprises the following steps:

[0061] Step 1: Using a screening instrument, the beaten cotton linter pulp with a beating degree of 63°SR, an average fiber length of 0.82 mm, and a length distribution range of 0.1-1.7 mm is screened and grouped according to the fiber length as follows: F1 short fiber (0.1-0.3 mm), F2 medium short fiber (0.3-0.6 mm), F3 medium long fiber (0.6-1.2 mm), F4 long fiber (1.2-1.7 mm), to obtain graded cotton pulp;

[0062] Step 2: The graded cotton pulp obtained in step 1 is recombined according to the following proportions: the weight parts of F1-F4 are 55 parts: 25 parts: 15 parts: 5 parts, respectively, and the total weight parts of the recombined are 100 parts. The average length and beating degree are then evaluated. The average fiber length that needs to be met is 0.82 mm, and the beating degree is 63°SR, to obtain a recombined cotton pulp;

[0063] Step 3: The recombinant cotton pulp obtained in step 2 is mixed with cellulose nanofibrils in a mass ratio of 92:8, and the high-folding-resistance special paper is obtained through processes such as filtering, forming, pressing, and drying.

[0064] A high-folding-resistance specialty paper prepared in Example 5 is prepared by mixing recombinant cotton pulp with an average fiber length of 0.8-0.9 mm and a beating degree of 55°SR-65°SR with cellulose nanofibrils with a length of 200-500 μm, a diameter of 20-100 nm, and an aspect ratio of 2000-5000 in a mass ratio of 92:8; the basis weight of the high-folding-resistance specialty paper is 95 g / m 2 The tensile strength is 89N / cm, the tear strength is 3652 times, and the folding endurance is 3652 times. It can be used in special papers with high requirements on durability and folding strength, such as banknotes, securities, maps, nautical charts and other fields.

[0065] Example 6

[0066] A method for preparing high-folding-resistance specialty paper comprises the following steps:

[0067] Step 1: Using a screening instrument, the beaten cotton linter pulp with a beating degree of 65°SR, an average fiber length of 0.8 mm, and a length distribution range of 0.1-1.7 mm is screened and grouped according to the fiber length as follows: F1 short fiber (0.1-0.3 mm), F2 medium short fiber (0.3-0.6 mm), F3 medium long fiber (0.6-1.2 mm), F4 long fiber (1.2-1.7 mm), to obtain graded cotton pulp;

[0068] Step 2: The graded cotton pulp obtained in step 1 is recombined according to the following proportions: the weight proportions of F1-F4 are 60 parts: 30 parts: 5 parts: 5 parts, respectively, and the total weight proportion of the recombined cotton pulp is 100 parts. The average length and beating degree of the recombined cotton pulp are evaluated. The average fiber length that needs to be met is 0.8 mm and the beating degree is 65°SR, thereby obtaining a recombined cotton pulp.

[0069] Step 3: The recombinant cotton pulp obtained in step 2 is mixed with cellulose nanofibrils in a mass ratio of 90:10, and high folding-resistant special paper is obtained through processes such as filtering, forming, pressing, and drying.

[0070] A high-folding-resistance specialty paper prepared in Example 6 is prepared by mixing recombinant cotton pulp with an average fiber length of 0.8-0.9 mm and a beating degree of 55°SR to 65°SR with cellulose nanofibrils with a length of 200-500 μm, a diameter of 20-100 nm, and an aspect ratio of 2000-5000 in a mass ratio of 90:10; the basis weight of the high-folding-resistance specialty paper is 100 g / m 2 The tensile strength is 90N / cm, the tear strength is 3800 times, and the folding endurance is 3800 times. It can be used in special papers with high requirements on durability and folding strength, such as banknotes, securities, maps, nautical charts and other fields.

[0071] The above examples prove that the present invention adopts new technology and new methods to develop and produce a high-folding-resistance special paper, which effectively improves the overall flexibility and folding strength of the paper, overcomes the problems of traditional cotton pulp with a wide fiber length distribution range, severe damage to fiber strength resulting in poor flexibility, and low folding resistance of cotton fiber paper. It is expected to be applied to special papers with high requirements on durability and folding strength, such as banknotes, securities, maps, nautical charts and other fields.

[0072] The embodiments described above are merely preferred technical solutions of the present invention and should not be construed as limiting the present invention. The embodiments and features in the embodiments of this application may be arbitrarily combined with one another unless they conflict. The scope of protection of the present invention shall be the technical solutions described in the claims, including equivalent replacements of the technical features in the technical solutions described in the claims. Equivalent replacements and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A method for preparing high-folding-resistance specialty paper, characterized in that: The following steps are involved: S1: Screening the refined cotton linter pulp according to fiber length to obtain graded cotton pulp; The graded cotton pulp is divided into F1 short-fiber cotton pulp, F2 medium-short-fiber cotton pulp, F3 medium-long-fiber cotton pulp and F4 long-fiber cotton pulp; S2: reconstitute the graded cotton pulp according to a preset weight ratio and evaluate it according to the reconstitution standard. If the evaluation is qualified, the reconstituted cotton pulp is obtained. If it is unqualified, S2 is repeated until the evaluation is qualified. S3: mixing the recombinant cotton pulp and cellulose nanofibrils in proportion, and then filtering, pressing and drying to obtain high-folding-resistance specialty paper; In S2, the recombinant standard includes average fiber length and beating degree, the average fiber length is 0.8 mm to 0.9 mm, and the beating degree is 55°SR to 65°SR; In S3, the recombinant cotton pulp and cellulose nanofibrils are prepared in a mass ratio of (90-98): (2-10); In S3, the aspect ratio of the cellulose nanofibrils is 2000-5000.

2. The method for preparing a high folding-resistant specialty paper according to claim 1, characterized in that: The fiber length of the F1 short-fiber cotton pulp is 0.1 mm to 0.3 mm, the fiber length of the F2 medium-short-fiber cotton pulp is 0.3 mm to 0.6 mm, the fiber length of the F3 medium-long-fiber cotton pulp is 0.6 mm to 1.2 mm, and the fiber length of the F4 long-fiber cotton pulp is 1.2 mm to 1.7 mm.

3. The method for preparing a high folding-resistant specialty paper according to claim 1, characterized in that: In S2, the preset weight ratio is F1 short fiber cotton pulp: F2 medium short fiber cotton pulp: F3 medium long fiber cotton pulp: F4 long fiber cotton pulp = (40 parts to 60 parts): (10 parts to 30 parts): (5 parts to 25 parts): (5 parts to 20 parts).

4. The method for preparing a high folding-resistant specialty paper according to claim 1, characterized in that: In S2, the preset weight portions are 100 portions in total.

5. The method for preparing a high folding-resistant specialty paper according to claim 1, characterized in that: In S3, the cellulose nanofibrils have a length of 200 μm to 500 μm and a diameter of 20 nm to 100 nm.

6. A high folding-resistant specialty paper, characterized in that: The method for preparing a high folding-resistant specialty paper according to any one of claims 1 to 5 is used, wherein the basis weight of the high folding-resistant specialty paper is 80 g / m 2 ~100 g / m 2 , tensile strength is 65 N / cm~90N / cm, and folding endurance is 2400 times~3800 times.

7. Use of the high folding-resistant specialty paper according to claim 6 in banknotes, securities, maps and nautical charts.

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