Paper substrate and preparation method therefor, and paper-based flexible package

Abstract

Disclosed in the present invention are a paper substrate and a preparation method therefor, and a paper-based flexible package. The preparation method for the paper substrate comprises: carrying out pulping, refining and blending on softwood pulp and hardwood pulp to form pulp with a concentration of 0.1-0.6%; adding epoxy resin modified polyacrylate at 5-15 kg / per ton of bone-dry pulp, a rosin size at 0.2-2 kg / per ton of bone-dry pulp, and a wet strength agent at 30-80 kg / per ton of bone-dry pulp; and carrying out papermaking, drying, creping and winding. The paper-based flexible package comprises a package body; the package body is enclosed by a paper substrate to form a hollow cavity, comprising two end sealing portions and front and rear sealing portions; the two end sealing portions and the front and rear sealing portions are connected by means of a plurality of bonding layers; and the bonding layers are formed by the interlocking of plant fibers and polyacrylate. The paper substrate obtained in the present invention has the required heat-sealing properties and strength even at low grammage, ensuring the flexibility of the substrate and facilitating automated continuous production of devices.

Description

A paper substrate and its preparation method and flexible paper-based packaging body Technical Field

[0001] The present invention relates to paper and a preparation method and application thereof, and in particular to a paper substrate and a preparation method thereof, and a flexible paper-based packaging body. Background Art

[0002] Currently, there are two common packaging methods for products such as tissues: one is to use plastic film or plastic bags to form a flexible packaging body, and the other is to use rigid cardboard to form a box-shaped packaging body. Plastic film is a flexible material with excellent heat-sealing properties and good water resistance, which is suitable for paper product assembly line packaging operations and is widely used in the industry. However, it is a petroleum-based material and is not biodegradable. With the increasing requirements for environmental protection and other aspects, people hope that products such as tissues can be packaged entirely with biodegradable substrates, especially paper substrates. Although existing cardboard is biodegradable, due to its high stiffness, it cannot be packaged online using rolls. It must first be processed into box-shaped semi-finished products in a carton factory before it can be used in paper product factories. This reduces packaging efficiency and increases packaging costs. Therefore, there is a need for a thin paper substrate with a certain degree of flexibility that can directly replace plastic film and rigid cardboard to achieve automated packaging.

[0003] However, flexible, thin paper substrates present numerous challenges when used in tissue packaging lines, starting with the bonding process to achieve a hermetic seal. Plastic film is known to be thermoplastic, melting upon heating to form a bond. However, paper substrates made from plant fibers, such as wood pulp and bamboo pulp, lack inherent heat-sealing properties. Therefore, the bonding issue must be addressed when using paper substrates for tissue packaging. Chinese patent applications No. 200520119543.1, No. 200520119544.6, and No. 200520119542.7 disclose methods for applying a sealing coating to the surface of paper to achieve adhesion. However, this method requires applying adhesive to both surfaces of the paper, which is a complex process and has high processing costs. Furthermore, the adhesive layer remains on the paper surface and, due to the properties of the adhesive, is susceptible to delamination and delamination in hot, cold, or humid environments. Furthermore, on the production side, the paper passes through a series of rollers from raw material to finished packaging. Friction and temperature increases during material transportation can leave residual sealing coating on the rollers, causing sticking and affecting equipment operation. Furthermore, the paper rolls can become sticky and unable to unwind properly due to stickiness. Furthermore, during storage and transportation of paper towel products, they are stacked, and the adhesive coating on their surfaces is highly unstable. For example, in humid or hot environments, the paper can stick together, tearing the paper during separation or damaging printed patterns.

[0004] In general, when existing flexible tissue paper substrates are used as packaging bodies, the adhesives are prone to debonding and delamination, which can cause roller sticking during production, and the humid and high-temperature storage environment can cause the internal products to stick together.

[0005] Summary of the Invention

[0006] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a paper substrate with good flexibility, low weight and good heat sealing properties. Another purpose of the present invention is to provide a method for preparing a degradable and easily vacuum-adsorbed paper substrate. Another purpose of the present invention is to provide a flexible paper-based packaging body with high bonding strength, stable bonding performance and conducive to automated continuous production of equipment.

[0007] Technical solution: The paper substrate described in the present invention is prepared by pulping, grinding and mixing coniferous wood pulp and broadleaf wood pulp to form a pulp with a concentration of 0.1 to 0.6%; adding epoxy resin modified polyacrylate in an amount of 5 to 15 kg / ton of absolute dry pulp, rosin glue in an amount of 0.2 to 2 kg / ton of absolute dry pulp, and a wet strength agent in an amount of 30 to 80 kg / ton of absolute dry pulp; and papermaking, drying, wrinkling and rolling to form a paper substrate.

[0008] Furthermore, the paper substrate has a gram weight of 30 to 80 grams per square meter, a thickness of 60 to 180 microns, a longitudinal strength of 4,000 to 8,000 grams per inch, and a thermal bonding strength of 1.7 to 3.5 kilonewtons per meter.

[0009] Preferably, the paper substrate has a gram weight of 40 to 65 grams per square meter, a thickness of 80 to 160 microns, and a thermal bonding strength of 2.0 to 3.5 kilonewtons per meter, which results in higher packaging efficiency and stronger bonding.

[0010] More preferably, the paper substrate is 100 to 140 microns thick. Automatic tissue packaging machines inevitably require folding and adsorption during operation. Thicker materials increase the difficulty of folding, and excessively thick packaging materials can lead to uneven folds and reduced packaging efficiency. Existing packaging machines use vacuum suction to hold the packaging material in place, but thicker materials increase the difficulty of adsorption, impacting both packaging quality and efficiency.

[0011] More preferably, the thermal adhesive strength of the paper substrate is 2.5 to 3.5 kN / m.

[0012] Furthermore, the wet strength agent is one or more of polyamide epichlorohydrin (PAE), polyacrylamide (PAM) and polyethyleneimine (PEI).

[0013] Preferably, the wet strength agent is PAE.

[0014] The method for preparing a paper substrate according to the present invention comprises the following steps:

[0015] Step 1: pulping, refining, and mixing coniferous wood pulp and hardwood wood pulp to form a pulp with a concentration of 0.1 to 0.6%;

[0016] Step 2: adding functional materials to the slurry obtained in step 1, wherein the functional materials include 5-15 kg / ton of absolute dry pulp epoxy resin modified polyacrylate, 0.2-2 kg / ton of absolute dry pulp rosin glue, and 30-80 kg / ton of absolute dry pulp wet strength agent;

[0017] Step 3: papermaking, drying, wrinkling and rolling the product obtained in step 2 to form a paper substrate.

[0018] Furthermore, in step 1, the mass ratio of coniferous wood pulp to broadleaf wood pulp is 70-100:0-30.

[0019] Furthermore, in step 2, the functional monomer also includes 3 to 15 kg / ton of absolute dry pulp of nanocellulose, which can further increase the bonding between the epoxy resin modified polyacrylate and the fiber, thereby increasing thermal stability and heat-sealing bonding strength.

[0020] The dosage of nanocellulose is preferably 5 to 10 kg per ton of absolute dry pulp.

[0021] The flexible paper-based packaging body described in the present invention includes a packaging body body, which is enclosed by a paper substrate to form a hollow cavity, including two end sealing parts and front and back sealing parts; the two end sealing parts and the front and back sealing parts are connected by a plurality of adhesive layers; the adhesive layers are formed by the mosaic of plant fibers and polyacrylate, and the polyacrylate is filled around the plant fibers; the paper substrate is prepared by: pulping, refining, and mixing coniferous wood pulp and hardwood pulp to form a pulp with a concentration of 0.1 to 0.6%; adding epoxy resin modified polyacrylate in an amount of 5 to 15 kg per ton of absolute dry pulp, rosin glue in an amount of 0.2 to 2 kg per ton of absolute dry pulp, and a wet strength agent in an amount of 30 to 80 kg per ton of absolute dry pulp; papermaking, drying, wrinkling, and rolling.

[0022] Furthermore, the shape of the hollow cavity is a cube, a cuboid or a cylinder.

[0023] Furthermore, a tear portion is provided on the side of the packaging body without the adhesive layer.

[0024] Furthermore, the number of adhesive layers on the sealing portions at both ends is 9 or more.

[0025] Preparation principle: The surface of the paper substrate is formed in a state where the fibers are filled with epoxy resin-modified polyacrylate. After the two layers of material are overlapped, a certain temperature and pressure are applied to the materials, and the epoxy resin-modified polyacrylate will fuse, so that a bonding layer as shown in Figure 2 is formed at the overlapping part of the two layers of material. At the bonding part, fibers and fused epoxy resin-modified polyacrylate coexist, and one end of the fiber is embedded in the bonding layer, while the other end is still embedded in the paper. This structure increases the bonding strength between the paper and the bonding layer.

[0026] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0027] 1. The prepared paper substrate still has the heat-sealing, water-repellent and strength required for packaging materials at a low weight, ensuring the flexibility of the substrate and being more conducive to automated continuous production of equipment;

[0028] 2. The surface of the prepared paper substrate has protrusions caused by fibers and wrinkles. When multiple single-package products are stacked, the contact area between adjacent packages is greatly reduced, and even in high-temperature storage environments, the products will not stick together.

[0029] 3. The adhesive layer of the packaging body is formed by the interlocking of plant fibers and polyacrylates, with high bonding strength and stable bonding performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG1 is a schematic structural diagram of a packaging body 1 of the present invention;

[0031] FIG2 is a schematic structural diagram of the adhesive layer 103 of the present invention. DETAILED DESCRIPTION

[0032] In the following examples, the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial sources.

[0033] As shown in Figure 1, the flexible paper-based packaging body includes a packaging body 1, which is made of a paper substrate and encloses a hollow cavity. The packaging body 1 includes two end sealing parts 101 and front and back sealing parts 102. Any end of the two end sealing parts 101 contains at least nine adhesive layers 103, and there is at least one adhesive layer 103 at the folded and overlapping parts of the paper substrate. The front and back sealing parts 102 include a number of adhesive areas set at intervals, forming at least two adhesive layers 103. The adhesive layer 103 is formed by the mosaic of plant fiber and polyacrylate, and the polyacrylate is filled around the plant fiber. Plant fiber is natural fiber such as wood pulp and bamboo pulp used in the papermaking industry. The shape of the hollow cavity is a cube, a rectangular parallelepiped or a cylinder. A tear portion 104 is provided on the top surface of the packaging body 1 where there is no adhesive layer 103. In order to facilitate the removal of paper and convenient storage, the containing part (hollow cavity) can be additionally provided with auxiliary materials as needed.

[0034] Example 1

[0035] A method for preparing a paper substrate comprises the following steps:

[0036] S1. After pulping 90 wt% of softwood pulp and 10 wt% of hardwood pulp, the softwood pulp is refined to 550 CSF and mixed to form a slurry with a concentration of 0.4%;

[0037] S2. Add 10 kg / ton of absolute dry pulp of epoxy resin modified polyacrylate, 1 kg / ton of absolute dry pulp of rosin size, and 80 kg / ton of absolute dry pulp of wet strength agent PAE to the pulp obtained in S1 in the front tank of the machine;

[0038] S3. The product obtained in S2 is paper-made, dried, creped, and rolled up to form a paper substrate 2.

[0039] The basis weight is tested in accordance with GBT 24328.5, the thickness is tested in accordance with GBT 24328.2, the longitudinal strength is tested in accordance with GBT 24328.3, and the thermal bonding strength is tested in accordance with GBT 24328.3.

[0040] The paper substrate 2 obtained in this embodiment has a gram weight of 35.6 g / m2, a thickness of 63 μm, a longitudinal strength of 6363 g / inch, and a thermal bonding strength of 1.95 kN / m.

[0041] Example 2

[0042] A method for preparing a paper substrate comprises the following steps:

[0043] S1. After pulping 80 wt% of softwood pulp and 20 wt% of hardwood pulp, the softwood pulp is refined to 570 CSF and mixed to form a slurry with a concentration of 0.4%;

[0044] S2. Add 10 kg / ton of absolute dry pulp of epoxy resin modified polyacrylate, 1 kg / ton of absolute dry pulp of rosin size, and 60 kg / ton of absolute dry pulp of wet strength agent PAE to the pulp obtained in S1 in the front tank of the machine;

[0045] S3. The product obtained in S2 is paper-made, dried, creped, and rolled up to form a paper substrate 2.

[0046] The paper substrate 2 obtained in this embodiment has a gram weight of 48.6 grams per square meter, a thickness of 110 microns, a longitudinal strength of 6678 grams per inch, and a thermal bonding strength of 2.01 kilonewtons per meter.

[0047] Example 3

[0048] A method for preparing a paper substrate comprises the following steps:

[0049] S1. After pulping 95 wt% of softwood pulp and 5 wt% of hardwood pulp, the softwood pulp is refined to 570 CSF and mixed to form a slurry with a concentration of 0.4%;

[0050] S2. Add 12 kg / ton of absolute dry pulp of epoxy resin modified polyacrylate, 1.5 kg / ton of absolute dry pulp of rosin size, 60 kg / ton of absolute dry pulp of wet strength agent PAE, and 6 kg / ton of absolute dry pulp of nanocellulose to the pulp obtained in S1 in the front tank of the machine;

[0051] S3. The product obtained in S2 is paper-made, dried, creped, and rolled up to form a paper substrate 2.

[0052] The paper substrate 2 obtained in this embodiment has a gram weight of 56.1 grams per square meter, a thickness of 120 microns, a longitudinal strength of 7717 grams per inch, and a thermal bonding strength of 3.5 kilonewtons per meter.

[0053] Example 4

[0054] A method for preparing a paper substrate comprises the following steps:

[0055] S1. After pulping 70 wt% of softwood pulp and 30 wt% of hardwood pulp, the softwood pulp is refined to 560 CSF and mixed to form a slurry with a concentration of 0.1%;

[0056] S2. Add 5 kg / ton of absolute dry pulp of epoxy resin modified polyacrylate, 0.2 kg / ton of absolute dry pulp of rosin size, 30 kg / ton of absolute dry pulp of wet strength agent PAM, and 3 kg / ton of absolute dry pulp of nanocellulose to the pulp obtained in S1 in the front tank of the machine;

[0057] S3. The product obtained in S2 is paper-made, dried, creped, and rolled up to form a paper substrate 2.

[0058] The paper substrate 2 obtained in this embodiment has a gram weight of 30 grams per square meter, a thickness of 60 microns, a longitudinal strength of 4000 grams per inch, and a thermal bonding strength of 1.7 kilonewtons per meter.

[0059] Example 5

[0060] A method for preparing a paper substrate comprises the following steps:

[0061] S1. After pulping 100 wt% of softwood pulp and 0 wt% of hardwood pulp, the softwood pulp is refined to 570 CSF and mixed to form a slurry with a concentration of 0.6%;

[0062] S2. Add 15 kg / ton of absolute dry pulp of epoxy resin modified polyacrylate, 2 kg / ton of absolute dry pulp of rosin size, 45 kg / ton of absolute dry pulp of wet strength agent PEI, and 15 kg / ton of absolute dry pulp of nanocellulose to the pulp obtained in S1 in the front tank of the machine;

[0063] S3. The product obtained in S2 is paper-made, dried, creped, and rolled up to form a paper substrate 2.

[0064] The paper substrate 2 obtained in this embodiment has a gram weight of 80 grams per square meter, a thickness of 180 microns, a longitudinal strength of 8000 grams per inch, and a thermal bonding strength of 2.7 kilonewtons per meter.

[0065] Example 6

[0066] A method for preparing a paper substrate comprises the following steps:

[0067] S1. After pulping 75 wt% of softwood pulp and 25 wt% of hardwood pulp, the softwood pulp is refined to 570 CSF and mixed to form a slurry with a concentration of 0.2%;

[0068] S2. Add 8 kg / ton of absolute dry pulp of epoxy resin modified polyacrylate, 0.5 kg / ton of absolute dry pulp of rosin size, 40 kg / ton of absolute dry pulp of wet strength agent PAE+PEI (mass ratio is 1:1), and 9 kg / ton of absolute dry pulp of nanocellulose to the pulp obtained in S1 in the front tank of the machine;

[0069] S3. The product obtained in S2 is paper-made, dried, creped, and rolled up to form a paper substrate 2.

[0070] The paper substrate 2 obtained in this embodiment has a gram weight of 40.1 grams per square meter, a thickness of 75 micrometers, a longitudinal strength of 5021 grams per inch, and a thermal bonding strength of 2.9 kilonewtons per meter.

[0071] Example 7

[0072] A method for preparing a paper substrate comprises the following steps:

[0073] S1. After pulping 85 wt% of softwood pulp and 15 wt% of hardwood pulp, the softwood pulp is refined to 570 CSF and mixed to form a slurry with a concentration of 0.3%;

[0074] S2. Add 13 kg / ton of absolute dry pulp of epoxy resin modified polyacrylate, 1.8 kg / ton of absolute dry pulp of rosin size, and 55 kg / ton of absolute dry pulp of wet strength agent PAM to the pulp obtained in S1 in the front tank of the machine;

[0075] S3. The product obtained in S2 is paper-made, dried, creped, and rolled up to form a paper substrate 2.

[0076] The paper substrate 2 obtained in this embodiment has a gram weight of 65.3 g / m2, a thickness of 143 μm, a longitudinal strength of 7000 gf / inch, and a thermal bonding strength of 3.2 kN / m.

[0077] Example 8

[0078] A method for preparing a paper substrate comprises the following steps:

[0079] S1. After pulping 92 wt% of softwood pulp and 8 wt% of hardwood pulp, the softwood pulp is refined to 570 CSF and mixed to form a slurry with a concentration of 0.5%;

[0080] S2. Add 9 kg / ton of absolute dry pulp of epoxy resin modified polyacrylate, 1.2 kg / ton of absolute dry pulp of rosin size, 45 kg / ton of absolute dry pulp of wet strength agent PEI, and 6 kg / ton of absolute dry pulp of nanocellulose to the pulp obtained in S1 in the front tank of the machine;

[0081] S3. The product obtained in S2 is paper-made, dried, creped, and rolled up to form a paper substrate 2.

[0082] The paper substrate 2 obtained in this embodiment has a gram weight of 70.2 grams per square meter, a thickness of 147 microns, a longitudinal strength of 7565 grams per inch, and a thermal bonding strength of 2.8 kilonewtons per meter.

[0083] Table 1 Performance data of paper substrate 2 obtained in Examples 1-8

[0084] As can be seen from Table 1 above, considering all the performances, the best embodiment is Embodiment 3.

[0085] Example 9

[0086] The paper substrate 2 obtained in Example 1 is used to prepare the packaging body 1 shown in Figure 1. The paper substrate 2 is enclosed to form a hollow cavity. The folded and overlapping portions of the paper substrate 2 are fixedly connected by hot pressing with an adhesive layer 103. The adhesive layer 103 is formed by interlocking plant fibers and polyacrylate, with the polyacrylate filling the plant fibers. The plant fibers are natural fibers such as wood pulp and bamboo pulp used in the papermaking industry.

[0087] Comparative Example 1

[0088] The remaining steps of this comparative example are the same as those of Example 9, with the only difference being that the polyacrylate in the adhesive layer 103 is replaced by epoxy resin. It was found that the adhesive layer formed after hot pressing was unstable.

[0089] Comparative Example 2

[0090] The remaining steps of this comparative example are the same as those of Example 9, with the only difference being that the plant fibers in the adhesive layer 103 are replaced with carbon fibers. It was found that the adhesive layer formed after hot pressing was unstable.

Claims

1. A paper substrate, characterized in that: The softwood pulp and the hardwood pulp are dispersed and refined to form a pulp with a concentration of 0.1 to 0.6%; epoxy resin modified polyacrylate is added in an amount of 5 to 15 kg / ton of absolute dry pulp, rosin glue is added in an amount of 0.2 to 2 kg / ton of absolute dry pulp, and a wet strength agent is added in an amount of 30 to 80 kg / ton of absolute dry pulp; the paper is made, dried, wrinkled, and rolled to form a paper substrate (2).

2. A paper substrate according to claim 1, characterized in that: The paper substrate (2) has a gram weight of 30 to 80 grams per square meter, a thickness of 60 to 180 microns, a longitudinal strength of 4,000 to 8,000 grams per inch, and a thermal bonding strength of 1.7 to 3.5 kilonewtons per meter.

3. The paper substrate according to claim 1, wherein: The wet strength agent is one or more of polyamide epichlorohydrin, polyacrylamide and polyethyleneimine.

4. A method for preparing a paper substrate, characterized in that: The following steps are involved: Step 1: pulping, refining, and mixing coniferous wood pulp and hardwood wood pulp to form a pulp with a concentration of 0.1 to 0.6%; Step 2: adding functional materials to the slurry obtained in step 1, wherein the functional materials include 5-15 kg / ton of absolute dry pulp epoxy resin modified polyacrylate, 0.2-2 kg / ton of absolute dry pulp rosin glue, and 30-80 kg / ton of absolute dry pulp wet strength agent; Step 3: papermaking, drying, wrinkling and rolling the product obtained in step 2 to form a paper substrate (2).

5. The method for preparing a paper substrate according to claim 4, wherein: In the step 1, the mass ratio of coniferous wood pulp to hardwood wood pulp is 70-100:0-30.

6. The method for preparing a paper substrate according to claim 4, wherein: In the step 2, the functional monomer further comprises 3-15 kg / ton of absolute dry pulp of nanocellulose.

7. A flexible paper-based packaging body, characterized in that: The invention comprises a packaging body (1), wherein the packaging body (1) is enclosed by a paper base material (2) to form a hollow cavity, and comprises two end sealing parts (101) and front and rear sealing parts (102); the two end sealing parts (101) and the front and rear sealing parts (102) are connected by a plurality of adhesive layers (103); the adhesive layers (103) are formed by interlocking plant fibers and polyacrylate, and the polyacrylate is filled around the plant fibers; the preparation method of the paper base material (2) is as follows: pulping, grinding and mixing coniferous wood pulp and broadleaf wood pulp to form a pulp with a concentration of 0.1 to 0.6%; adding epoxy resin modified polyacrylate in an amount of 5 to 15 kg / ton of absolute dry pulp, rosin glue in an amount of 0.2 to 2 kg / ton of absolute dry pulp, and wet strength agent in an amount of 30 to 80 kg / ton of absolute dry pulp; papermaking, drying, wrinkling and rolling.

8. The flexible paper-based packaging body according to claim 7, characterized in that: The shape of the hollow cavity is a cube, a cuboid or a cylinder.

9. The flexible paper-based packaging body according to claim 7, characterized in that: A tear portion (104) is provided on the side of the packaging body (1) where no adhesive layer (103) is provided.

10. The flexible paper-based packaging body according to claim 7, characterized in that: The number of the adhesive layers (103) on the two end sealing parts (101) is more than 9.

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