A high absorbency wetlaid paper and method of making the same

Abstract

The application relates to the field of sanitary products, and provides a high-absorptive wet water-absorption paper and a preparation method thereof, which solves the defects of limited water absorption, non-solid structure and slow liquid diffusion speed of the water-absorption paper obtained by using the existing preparation method of the prior art. The high-absorptive wet water-absorption paper comprises, from top to bottom, a first wet paper layer, a first SAP high-molecular layer, a second wet paper layer, a second SAP high-molecular layer and a dry paper layer which are arranged in a stacking mode, the first wet paper layer and the second wet paper layer both have high loftiness, the loftiness is 5-20 cm 3 / g.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of sanitary products, in particular to a high-absorbency wet water-absorbing paper and a preparation method thereof. BACKGROUND

[0002] High molecular water-absorbing resin can absorb hundreds to thousands of times of water of its own weight, has strong water-absorbing and water-retaining capacity, and is widely used in water-absorbing paper. At present, the common preparation methods of water-absorbing paper on the market are dry composite method and wet composite method. The dry composite method is to disperse high molecular water-absorbing resin onto the surface of the wood pulp layer after spraying glue on the surface of the wood pulp layer. Such an absorbent paper has low water absorption after drying due to the sprayed glue, and the high molecular water-absorbing resin often falls off when applied to disposable absorbent articles such as paper diapers or sanitary napkins, which poses a certain risk. The existing wet water-absorbing paper is usually prepared by adding high molecular water-absorbing resin at the initial stage of forming the wood pulp layer, and then covering a layer of dry paper for composite treatment. The water-absorbing paper obtained by this preparation method has low bulkiness, non-solid structure, slow liquid diffusion speed, and limited liquid absorption capacity.

[0003] Chinese Patent Publication No. CN109837801A discloses a high water-absorbing ratio water-absorbing paper and a manufacturing method thereof. The water-absorbing paper includes a lower layer paper, an upper layer paper, and water-absorbing resin (SAP) particles. The lower layer paper and the upper layer paper are compounded in the wet part during papermaking on a papermaking machine, and the water-absorbing resin (SAP) particles are uniformly added before compounding. After the lower layer paper and the upper layer paper are pressure-compounded, the water-absorbing resin (SAP) particles are embedded in the compounded area of the lower layer paper and the upper layer paper, and then the product is obtained after drying and rolling. The water-absorbing paper of the invention contains high molecular water-absorbing resin (SAP) particles that are not exposed and are uniformly embedded in the paper, and do not fall off during use. The upper and lower surfaces of the water-absorbing paper of the invention are both exposed wood pulp, which quickly absorbs water during the water-absorbing process and quickly diffuses. The diffused water contacts and is absorbed by the high molecular water-absorbing resin (SAP) particles. The high molecular water-absorbing resin (SAP) has high water-absorbing ratio and water-locking effect. However, the water-absorbing paper obtained by the invention has a structure of upper layer paper-middle layer water-absorbing resin particles-lower layer paper, which is relatively thin, has limited water-absorbing capacity, has non-solid structure, and has slow liquid diffusion speed. SUMMARY

[0004] Therefore, in view of the above problems, the present application provides a high-absorbency wet water-absorbing paper and a preparation method thereof, which solves the defects of limited water-absorbing capacity, non-solid structure, and slow liquid diffusion speed of the water-absorbing paper obtained by the existing preparation method.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solution: a preparation method of a high-absorbency wet water-absorbing paper, comprising the following preparation steps:

[0006] (1) Preparation of wet pulp: coniferous wood pulp and fluff pulp are respectively crushed, stirred and uniformly mixed, then the coniferous wood pulp and fluff pulp are mixed in a weight ratio of 6-8:4-2 to obtain mixed pulp, softening agent and bulk agent are added into the mixed pulp, and stirring is continued until the mixture is uniformly mixed to obtain wet pulp, which is pumped into a pulp storage tank;

[0007] (2) SAP spreading: the SAP polymer in the hopper is transported to the storage tank of the polymer spreading device by a screw, and the application amount is adjusted by controlling the rotation speed and surface groove depth of the application roller, and the application amount is controlled at 20-35 g / m 2 , and the temperature of the application roller is controlled at 48-52℃;

[0008] (3) Compounding: the wet pulp obtained in step (1) is transported by a felt cloth, and after preliminary water removal, it is transported to the SAP polymer spreading section I, and the SAP polymer is spread on the surface of the wet pulp online to compound a layer of dry paper, and the pressure of the pressure roller is controlled at 0.3-0.5 Mpa;

[0009] (4) Preliminary drying: the compounded paper is conveyed to a drying cylinder for preliminary drying treatment, and the drying temperature is controlled at 110-135℃ to obtain a semi-finished product in a semi-dry state with a surface layer of dry paper, a middle layer of SAP polymer and a bottom layer of wet paper;

[0010] (5) The semi-dry semi-finished product is peeled off from the drying cylinder by a creping knife with an angle of 8-15° to have a certain three-dimensional structure, and is then conveyed online after creping;

[0011] (6) Secondary SAP spreading: the wet paper pulp obtained in step (1) is conveyed to the SAP polymer spreading section II on another conveying line, and the SAP is spread, and then pressed by a pressure roller with a pressure of 0.3-0.5 Mpa, and then subjected to preliminary drying treatment to obtain wet paper with SAP polymer spread on the surface;

[0012] (7) The semi-finished product conveyed online in step (5) is conveyed by 180° inversion transmission, so that the surface layer of the semi-finished product is wet paper, the middle layer is SAP polymer, and the bottom layer is dry paper, and the wet paper with SAP polymer spread on the surface obtained in step (6) is inverted and conveyed by 180° after inversion transmission, and then compounded with the semi-finished product to obtain water-absorbing paper with a structure of wet paper-SAP polymer-wet paper-SAP polymer-dry paper from top to bottom;

[0013] (8) Drying treatment: the water-absorbing paper is dried by a drying cylinder with a temperature of 110-135℃, and then peeled off from the drying cylinder by a creping knife with an angle of 8-15°, and transferred to an oven for drying treatment, and the water content is controlled at 5-10%, thereby obtaining a high-absorbing wet water-absorbing paper.

[0014] Further: further comprising a PVA aqueous solution application section, the PVA aqueous solution is prepared by stirring and dissolving PVA in water at 90-95℃, the mass concentration of the PVA aqueous solution is 0.5-2%; the PVA aqueous solution application section is performed in step (3) compounding, the specific process is: the wet pulp obtained in step (1) is conveyed by a felt cloth, a paper web is obtained after preliminary pressing and water removal, the PVA aqueous solution is sprayed on the surface of the paper web, and the paper web is transmitted to the SAP high polymer scattering section one, SAP high polymer is scattered on the surface of the paper web sprayed with the PVA aqueous solution, a layer of dry paper is compounded online, and the pressure of the pressure roller is controlled at 0.3-0.5Mpa.

[0015] Further: the amount of the softening agent is 0.2-0.4% of the weight of the mixed pulp.

[0016] Further: the amount of the softening agent is 0.2-0.4% of the weight of the mixed pulp.

[0017] Further: the specific way of the drying treatment in step (8) is that the hot air in the oven is hot air heated by a heat exchanger, the temperature of the hot air is 120-150℃, the hot air enters from the upper part of the oven and blows downward, and the hot air passes through the paper surface and the conveying mesh belt for drying and water removal.

[0018] Further: when the softwood pulp and the fluff pulp are crushed respectively, the concentration of the crushed pulp is 3-7wt%, the crushing time is 15-30min, and the grinding process is not used.

[0019] Further: the softening agent is a polyoxyethylene stearate.

[0020] Further: the softening agent is a polyoxyethylene stearate.

[0021] A high-absorptive wet water-absorbing paper comprises a first wet paper layer, a first SAP high polymer layer, a second wet paper layer, a second SAP high polymer layer and a dry paper layer which are sequentially stacked from top to bottom, the bulkiness of the first wet paper and the second wet paper is 5-20cm / g. 3

[0022] Further: a PVA layer is further arranged between the first wet paper layer and the first SAP high polymer layer.

[0023] By adopting the foregoing technical scheme, the application has the following beneficial effects:

[0024] ​1. The highly absorbent wet-laid absorbent paper of the present invention uses coniferous wood pulp and fluff pulp as the raw materials for the first and second wet-laid paper layers during the preparation process. Compared with traditional paper made only of wood pulp, it has higher bulkiness, faster diffusion speed, and is softer.

[0025] 2. The absorbent paper obtained by the preparation method of the highly absorbent wet-laid absorbent paper of the present invention comprises a first wet-laid paper layer, a first SAP polymer layer, a second wet-laid paper layer, a second SAP polymer layer, and a dry paper layer stacked in sequence from top to bottom. Compared with the traditional wet paper-SAP polymer layer-dry paper structure, the absorbent paper can absorb more liquid, has a higher liquid absorption capacity, and has a more three-dimensional and bulky structure.

[0026] 3. During the production process, the present invention uses a corrugating blade at an angle of 8-15° to peel the semi-dried semi-finished product from the drying drum, giving it a three-dimensional structure. After corrugation, it is then transported online. This specific corrugating process produces paper products with excellent three-dimensional properties. Because the corrugated structural layer—the wet paper layer—is located in the middle of the absorbent paper's final structure, the resulting absorbent paper has a three-dimensional and fluffy structure, facilitating rapid liquid passage and accelerating liquid absorption.

[0027] 4. Furthermore, the absorbent paper of the present invention is sprayed with a layer of PVA aqueous solution before the SAP polymer is spread on the wet paper web. The PVA aqueous solution is rich in hydrophilic groups and is soluble in water. After the SAP is spread, it can, to a certain extent, block direct contact between the SAP and the wet paper web. During the initial drying (initial drying temperature is 110-135°C), the PVA melts within this temperature range and acts as a barrier to the SAP. This can reduce the chance of contact between water in the wet paper web generated during subsequent processing and the SAP, thus providing a certain degree of protection for the SAP, and enabling the SAP in the resulting absorbent paper to maintain relatively good water absorption properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Fig. 1 Schematic diagram of the structure of the highly absorbent wet-process absorbent paper in Example 1 of the present invention;

[0029] Fig. 2 Schematic diagram of the preparation process of Example 1 of the present invention;

[0030] Fig. 3 Schematic diagram of the preparation process of Example 2 of the present invention;

[0031] Fig. 4 This is a schematic structural diagram of the highly absorbent wet-process absorbent paper in Example 2 of the present invention;

[0032] Fig. 5 Schematic diagram of the preparation process of Example 3 of the present invention;

[0033] Fig. 6 Schematic diagram of the structure of the highly absorbent wet-process absorbent paper in Example 3 of the present invention. DETAILED DESCRIPTION Example 1

[0034] refer to Figs. 1-2 A method for preparing highly absorbent wet-process absorbent paper comprises the following steps:

[0035] (1) Preparation of wet pulp: softwood pulp and fluff pulp are crushed and stirred respectively, and then the softwood pulp and fluff pulp are mixed in a weight ratio of 6:4 to obtain mixed pulp, and then polyoxyethylene stearate, sodium stearate, and ethylenediamine are added to the mixed pulp, and the mixture is stirred continuously until the mixture is evenly mixed to obtain wet pulp, which is then pumped into a pulp storage tank; the pulping concentration is 3wt%, and the pulping time is 15min; the amount of polyoxyethylene stearate is 0.2% of the weight of the mixed pulp, the amount of sodium stearate is 0.05% of the weight of the mixed pulp, and the amount of ethylenediamine is 0.1% of the weight of the mixed pulp;

[0036] (2) SAP spreading: The SAP polymer poured into the hopper is conveyed to the storage box of the polymer spreading device by a screw. The application amount is adjusted by controlling the speed of the application roller and the depth of the surface groove. The application amount is controlled at 20g / m 2 , the temperature of the application roller is controlled at 48°C;

[0037] (3) Compounding: The wet pulp obtained in step (1) is conveyed through a felt cloth, initially squeezed to remove water, and then conveyed to the SAP polymer spreading section 1, where SAP polymer is spread online on the surface of the wet pulp, and a layer of dry paper is compounded online, and the paper is pressed by a pressure roller, where the pressure of the pressure roller is controlled at 0.3 MPa;

[0038] (4) Preliminary drying: The composite paper is transferred to a drying drum for preliminary drying. The drying temperature is controlled at 110°C to obtain a semi-dry semi-finished product with a surface layer of dry paper, a middle layer of SAP polymer, and a bottom layer of wet paper.

[0039] (5) Using a wrinkling knife with an angle of 8° to peel the semi-dry semi-finished product off the drying drum, so that it has a certain three-dimensional structure, and then transmit it online after wrinkling;

[0040] (6) Secondary SAP spreading: The wet pulp obtained in step (1) is transferred to the SAP polymer spreading section 2 via another transmission line, and SAP is spread on the wet pulp. The pulp is pressed by a pressure roller, the pressure of which is controlled at 0.3 MPa, and then subjected to a preliminary drying treatment to obtain wet paper with SAP polymer spread on the surface.

[0041] (7) The semi-finished product transmitted online in step (5) is turned over 180° and transmitted, so that the surface layer of the semi-finished product is wet paper, the middle layer is SAP polymer, and the bottom layer is dry paper. The wet paper with SAP polymer sprinkled on the surface obtained in step (6) is then turned over 180° and transmitted and then compounded with the semi-finished product to obtain a water-absorbing paper with a structure of wet paper-SAP polymer-wet paper-SAP polymer-dry paper from top to bottom;

[0042] (8) Drying treatment: The absorbent paper is dried in a drying drum, the temperature of the drying drum is controlled at 110°C, and then peeled off the drying drum by an 8° wrinkling knife, transferred to an oven for drying treatment, and the moisture content is controlled at 5%, thereby obtaining a highly absorbent wet-process absorbent paper; the specific method of the drying treatment is as follows: the hot air in the oven is the hot air heated by a heat exchanger, the temperature of the hot air is 120°C, the hot air enters from the top of the oven and blows downward, and the hot air passes through the paper surface and the conveyor belt to dry and remove water;

[0043] (9) Slitting and rolling.

[0044] The highly absorbent wet-laid absorbent paper obtained by the above-mentioned preparation method has the following structure: a first wet-laid paper layer 1, a first SAP polymer layer 2, a second wet-laid paper layer 3, a second SAP polymer layer 4, and a dry paper layer 5 are stacked in order from top to bottom. The first wet-laid paper layer 1 and the second wet-laid paper layer 3 both have high fluffiness, with a fluffiness of 7 cm 3 / g. Example 2

[0045] refer to Fig. 3 and Fig. 4 And Example 1, compared with Example 1, the preparation method of a highly absorbent wet-process absorbent paper of this embodiment, step (3) is different from that of Example 1, and other schemes are the same as Example 1. Specifically, the compounding process of step (3) is: the wet pulp obtained in step (1) is transported through a felt cloth, and a paper web is obtained after preliminary squeezing and dehydration, the PVA aqueous solution is sprayed on the surface of the paper web, and then the paper web is transported to the SAP polymer spreading section 1, the SAP polymer is spread online on the surface of the paper web sprayed with the PVA aqueous solution, and a layer of dry paper is compounded online, and the paper web is subjected to a pressure roller pressing process, the pressure of the pressure roller is controlled at 0.3-0.5Mpa, and the PVA aqueous solution is prepared by stirring and dissolving PVA in 90°C water, and the mass concentration of the PVA aqueous solution is 1%.

[0046] The highly absorbent wet-process absorbent paper obtained by the above method has the following structure:

[0047] The first wet-laid paper layer 1, the first SAP polymer layer 2, the second wet-laid paper layer 3, the PVA layer 6, the second SAP polymer layer 4, and the dry paper layer 5 are stacked in sequence from top to bottom. The first wet-laid paper layer and the second wet-laid paper layer both have high fluffiness, with a fluffiness of 10 cm 3 / g. Example 3

[0048] refer to Fig. 5 、 Fig. 6 And Example 2, a method for preparing a highly absorbent wet-process absorbent paper in this embodiment, before spreading SAP for the second time in step (6), a layer of PVA aqueous solution shown in Example 2 is sprayed on the wet paper web, and other technical solutions are the same as those in Example 2.

[0049] The absorbent paper obtained by this method has the following structure: a first wet-laid paper layer 1, a first PVA layer 6, a first SAP polymer layer 2, a second wet-laid paper layer 3, a second PVA layer 7, a second SAP polymer layer 4, and a dry paper layer 5, which are stacked in sequence from top to bottom. Example 4

[0050] A method for preparing highly absorbent wet-process absorbent paper comprises the following steps:

[0051] (1) Preparation of wet pulp: Softwood pulp and fluff pulp are crushed and stirred respectively, and then the softwood pulp and fluff pulp are mixed in a weight ratio of 8:2 to obtain mixed pulp. Softener and bulking agent are then added to the mixed pulp, and the mixture is stirred continuously until it is evenly mixed to obtain wet pulp, which is then pumped into a pulp storage tank;

[0052] (2) SAP spreading: The SAP polymer poured into the hopper is conveyed to the storage box of the polymer spreading device by a screw. The application amount is adjusted by controlling the speed of the application roller and the depth of the surface groove. The application amount is controlled at 35g / m 2 , the temperature of the application roller is controlled at 52° C.;

[0053] (3) Compounding: The wet pulp obtained in step (1) is conveyed through a felt cloth, initially squeezed to remove water, and then conveyed to the SAP polymer spreading section 1, where SAP polymer is spread online on the surface of the wet pulp, and a layer of dry paper is compounded online, and the paper is pressed by a pressure roller, where the pressure of the pressure roller is controlled at 0.5 MPa;

[0054] (4) Preliminary drying: The composite paper is transferred to a drying drum for preliminary drying. The drying temperature is controlled at 135°C to obtain a semi-dry semi-finished product with a surface layer of dry paper, a middle layer of SAP polymer, and a bottom layer of wet paper.

[0055] (5) the semi-finished product in semi-dry state is peeled off from the drying cylinder by using a creping blade with an angle of 15°, so as to have a certain three-dimensional structure, and then is transferred on line after the creping treatment;

[0056] (6) secondary spreading of SAP: the wet paper pulp obtained in step (1) is transferred to a SAP polymer spreading section two on another transfer line, and is spread with SAP, and then is pressed by a pressure roller, the pressure of the pressure roller is controlled at 0.5 Mpa, and then is subjected to preliminary drying treatment, so as to obtain wet paper with SAP polymer on the surface;

[0057] (7) the semi-finished product transferred on line in step (5) is combined with the wet paper with SAP polymer on the surface transferred on line in step (6), so as to obtain water-absorbing paper with the structure of dry paper-SAP polymer-wet paper-SAP polymer-wet paper from top to bottom;

[0058] (8) drying treatment: the water-absorbing paper is subjected to drying treatment by a drying cylinder, the temperature of the drying cylinder is controlled at 135℃, and then is peeled off from the drying cylinder by a creping blade with an angle of 15°, and is transferred to an oven for drying treatment, and the water content is controlled at 10%, so as to obtain a high-absorbing wet water-absorbing paper.

[0059] In addition, the process of example four can be improved, for example, PVA aqueous solution is added in the preparation process of example four.

[0060] Although the present application is specifically shown and described in connection with preferred embodiments, those skilled in the art will appreciate that various modifications in form and detail can be made without departing from the spirit and scope of the application as defined by the appended claims.

Claims

1. A method for preparing highly absorbent wet-process absorbent paper, characterized in that: The method comprises the following preparation steps: (1) Preparation of wet pulp: Softwood pulp and fluff pulp are crushed and stirred respectively, and then the softwood pulp and fluff pulp are mixed in a weight ratio of 6-8:4-2 to obtain mixed pulp. Softener and bulking agent are then added to the mixed pulp, and the mixture is stirred continuously until it is evenly mixed to obtain wet pulp, which is then pumped into a pulp storage tank; (2) SAP spreading: The SAP polymer poured into the hopper is conveyed to the storage box of the polymer spreading device by a screw. The application amount is adjusted by controlling the speed of the application roller and the depth of the surface groove. The application amount is controlled at 20-35g / m 2 , the temperature of the application roller is controlled at 48-52°C; (3) Compounding: The wet pulp obtained in step (1) is conveyed through a felt cloth, initially squeezed to remove water, and then conveyed to the SAP polymer spreading section 1, where SAP polymer is spread online on the surface of the wet pulp, and a layer of dry paper is compounded online, and the paper is pressed by a pressure roller, where the pressure of the pressure roller is controlled at 0.3-0.5 MPa; (4) Preliminary drying: The composite paper is transferred to a drying drum for preliminary drying. The drying temperature is controlled at 110-135°C to obtain a semi-dry semi-finished product with a surface layer of dry paper, a middle layer of SAP polymer, and a bottom layer of wet paper. (5) Using a wrinkling knife with an angle of 8-15 degrees to peel the semi-dry semi-finished product off the drying drum, so that it has a certain three-dimensional structure, and then transmit it online after wrinkling; (6) Secondary SAP spreading: The wet pulp obtained in step (1) is transferred to the SAP polymer spreading section 2 via another transmission line, and SAP is spread on the wet pulp. The pulp is pressed by a pressure roller, the pressure of which is controlled at 0.3-0.5 MPa, and then subjected to a preliminary drying treatment to obtain wet paper with SAP polymer spread on the surface. (7) The semi-finished product transmitted online in step (5) is turned over 180° and transmitted, so that the surface layer of the semi-finished product is wet paper, the middle layer is SAP polymer, and the bottom layer is dry paper. The wet paper with SAP polymer sprinkled on the surface obtained in step (6) is then turned over 180° and transmitted and then compounded with the semi-finished product to obtain a water-absorbing paper with a structure of wet paper-SAP polymer-wet paper-SAP polymer-dry paper from top to bottom; (8) Drying: The absorbent paper is dried in a drying drum with the temperature of the drying drum controlled at 110-135°C, and then peeled off the drying drum with a wrinkling knife at an angle of 8-15°. The paper is then transferred to an oven for drying, and the moisture content is controlled at 5-10%. Thus, a highly absorbent wet-process absorbent paper is obtained.

2. The method for preparing a highly absorbent wet-process absorbent paper according to claim 1, wherein: The method further comprises applying a PVA aqueous solution section, wherein the PVA aqueous solution is prepared by stirring and dissolving PVA in water at 90-95° C., and the mass concentration of the PVA aqueous solution is 0.5-2%. The applying PVA aqueous solution section is carried out in the compounding step (3), and the specific process is as follows: the wet pulp obtained in the step (1) is conveyed through a felt cloth, and a paper web is obtained after preliminary squeezing and dehydration, the PVA aqueous solution is sprayed on the surface of the paper web, and the paper web is then conveyed to the SAP polymer spreading section 1, the SAP polymer is spread online on the surface of the paper web sprayed with the PVA aqueous solution, a layer of dry paper is compounded online, and the paper web is pressed by a pressure roller, and the pressure of the pressure roller is controlled at 0.3-0.5 MPa.

3. The method for preparing a highly absorbent wet-process absorbent paper according to claim 1, wherein: The amount of the softener used is 0.2-0.4% of the weight of the mixed pulp.

4. The method for preparing a highly absorbent wet-process absorbent paper according to claim 1, wherein: The dosage of the leavening agent is 0.1-0.3% of the weight of the mixed pulp.

5. The method for preparing a highly absorbent wet-process absorbent paper according to claim 1, wherein: The specific method of the drying treatment in step (8) is as follows: the hot air in the oven is the hot air heated by the heat exchanger, the hot air temperature is 120-150°C, the hot air enters from the top of the oven and blows downward, and the hot air passes through the paper surface and the conveyor belt to dry and remove water.

6. The method for preparing a highly absorbent wet-process absorbent paper according to claim 1, wherein: When the coniferous wood pulp and the fluff pulp are crushed separately, the pulping concentration is 3-7wt% and the pulping time is 15-30min.

7. The method for preparing a highly absorbent wet-process absorbent paper according to claim 1, wherein: The softener is polyoxyethylene stearate.

8. The method for preparing a highly absorbent wet-process absorbent paper according to claim 1, wherein: The leavening agent is a mixture of sodium stearate and ethylenediamine in a weight ratio of 1:2-3.

Images