Process for producing hydrophilic stainless steel gasket

Abstract

The application relates to the technical field of stainless steel packing paper, and particularly discloses a production process of hydrophilic stainless steel packing paper. By introducing styrene-maleic anhydride copolymer and polyamide-epichlorohydrin resin into the packing paper and introducing starch hydroxypropyl trimethyl ammonium chloride on the surface of the packing paper, the hydrophilicity of the packing paper is obviously improved, the influence of the packing paper product on the surface tension of the stainless steel is reduced, the surface tension of the stainless steel is maintained, and the material performance can fully meet the requirements of the production process of the cylinder gasket.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of stainless steel pad paper, in particular to a production process of hydrophilic stainless steel pad paper. BACKGROUND

[0002] The stainless steel pad paper refers to special paper which is inserted to prevent friction of stainless steel during coiling of the stainless steel plate and needs to be in contact with the stainless steel plate for a long time. For some special stainless steel products (such as strip steel used for processing cold storage containers, cylinder gaskets and the like), if the hydrophilicity of the pad paper is poor or is contaminated, the surface tension of the strip steel product will be reduced. Since most of the existing pad paper products have poor hydrophilicity, the stainless steel pad paper needs to be improved.

[0003] A Chinese patent with publication number CN105986504B discloses a manufacturing method of hydrophilic stainless steel pad paper, which comprises the following steps: (1) selecting bleached kraft wood pulp with low extract content as raw material, and first performing pulping and refining treatment to obtain pulp with a refining mass concentration of 3-3.5%; (2) adding 0.5-1wt% of sizing agent styrene-maleic anhydride copolymer and 0.6-1wt% of wet strength agent polyamide-epichlorohydrin resin to the pulp for pulp preparation; (3) sizing the uniformly mixed pulp, removing slag and screening; (4) performing papermaking and pressing treatment in a papermaking system by using a papermaking process; and (5) performing drying and calendering, and then winding and slitting into sheet-shaped finished products. The stainless steel pad paper prepared according to the process has certain hydrophilicity and can pass the 44# daft ink test.

[0004] According to the related art, the inventors believe that although the stainless steel pad paper in the related art can pass the 44# daft ink test, for the stainless steel product used for manufacturing cylinder gaskets, the production process of the cylinder gasket has higher requirements for the material performance, so the stainless steel pad paper in the related art is still insufficient to sufficiently maintain the surface tension of the stainless steel product, which leads to that the stainless steel is difficult to pass the higher level surface tension test and is difficult to be used in cooperation with the stainless steel product used for manufacturing cylinder gaskets. SUMMARY

[0005] The stainless steel pad paper in the related art is insufficient to sufficiently maintain the surface tension of the stainless steel product, which leads to that the stainless steel is difficult to pass the higher level surface tension test and is difficult to be used in cooperation with the stainless steel product used for manufacturing cylinder gaskets. In order to improve this defect, the application provides a production process of hydrophilic stainless steel pad paper.

[0006] The application provides a production process of hydrophilic stainless steel pad paper, which adopts the following technical scheme:

[0007] A production process of hydrophilic stainless steel pad paper, comprising the following steps:

[0008] (1) respectively for coniferous pulp and broad-leaved pulp are carried out pulping, deslagging and refining, then mixed to obtain intermediate pulp, the intermediate pulp is conveyed to the pulp mixing tank after being beaten; the paper machine wet broke pulp is passed through a sieve and then added into the pulp mixing tank to mix with the beaten intermediate pulp to obtain the compounded wood pulp;

[0009] (2) the first sizing agent is added into the pulp mixing tank to mix with the compounded wood pulp to obtain the mixed pulp; the components of the first sizing agent include styrene-maleic anhydride copolymer and polyamide-epichlorohydrin resin; in this step, the total amount of styrene-maleic anhydride copolymer and polyamide-epichlorohydrin resin is 30-40 kg / ton of paper;

[0010] (3) the mixed pulp is ground and then introduced into the papermaking vat, and then the papermaking and pressing are carried out after being washed, desludged, sized and screened to obtain the semi-finished mat paper, and then the second sizing agent is used to size the surface of the semi-finished mat paper according to a sizing amount of 1.5-2.5 g / m 2

[0011] By using the above technical scheme, in addition to adding styrene-maleic anhydride copolymer and polyamide-epichlorohydrin resin as the internal sizing agent in the pulp mixing process to make the internal sizing agent dispersed between the paper fibers, surface sizing is also carried out on the surface of the semi-finished mat paper, and starch hydroxypropyl trimethyl ammonium chloride is applied to the surface of the semi-finished mat paper. Starch hydroxypropyl trimethyl ammonium chloride has good adhesion to paper fibers and strong hydrophilicity. By introducing styrene-maleic anhydride copolymer and polyamide-epichlorohydrin resin into the mat paper and introducing starch hydroxypropyl trimethyl ammonium chloride onto the surface of the mat paper, the hydrophilicity of the mat paper can be obviously improved, thereby reducing the influence of the mat paper product on the surface tension of the stainless steel, helping to maintain the surface tension of the stainless steel, and being able to fully meet the requirements of the production process of the cylinder head gasket on the material performance.

[0012] As a preferred, the components of the first sizing agent further include sodium carboxymethyl cellulose, the amount of the sodium carboxymethyl cellulose is 0.4-1.2% of the absolute dry weight of the compounded wood pulp, and the degree of substitution of the sodium carboxymethyl cellulose is 0.4-1.4.

[0013] ​By adopting the technical scheme, the first sizing agent component is preferred, and sodium carboxymethyl cellulose is added. The sodium carboxymethyl cellulose can be dispersed in the slurry and can form hydrogen bonds between fibers. In addition, the sodium carboxymethyl cellulose can also electrostatically adsorb starch hydroxypropyl trimethyl ammonium chloride loaded on the surface of the semi-finished paper pad in the surface sizing process, thereby increasing the bonding force between the fibers, and therefore the addition of sodium carboxymethyl cellulose helps to improve the tensile strength of the stainless steel paper pad.

[0014] Preferably, the amount of sodium carboxymethyl cellulose is 0.8-1.2% of the weight of the compounded wood pulp absolute dry pulp.

[0015] By adopting the technical scheme, the amount of sodium carboxymethyl cellulose is preferred, which helps to improve the tensile strength of the stainless steel paper pad.

[0016] Preferably, the degree of substitution of the sodium carboxymethyl cellulose is 0.9-1.4.

[0017] By adopting the technical scheme, the degree of substitution of the sodium carboxymethyl cellulose is preferred, which promotes the sufficient dispersion of the sodium carboxymethyl cellulose and helps to improve the tensile strength of the stainless steel paper pad.

[0018] Preferably, the component of the first sizing agent further includes cationic polyacrylamide, and the amount of the cationic polyacrylamide is 0.12-0.50% of the weight of the compounded wood pulp absolute dry pulp.

[0019] By adopting the technical scheme, the component of the first sizing agent further includes cationic polyacrylamide on the basis of adding sodium carboxymethyl cellulose. In addition to participating in the association of hydrogen bonds, the cationic polyacrylamide can also electrostatically adsorb sodium carboxymethyl cellulose, which helps to improve the tensile strength of the stainless steel paper pad.

[0020] Preferably, the amount of the cationic polyacrylamide is 0.32-0.50% of the weight of the compounded wood pulp absolute dry pulp.

[0021] By adopting the technical scheme, the amount of the cationic polyacrylamide is preferred, which helps to improve the tensile strength of the stainless steel paper pad.

[0022] Preferably, in step (2) of the production process of the hydrophilic stainless steel paper pad, wollastonite fibers and a first sizing agent are added together into a pulp mixing tank, the amount of the wollastonite fibers is 1.4-5.7% of the weight of the compounded wood pulp absolute dry pulp, the average length of the wollastonite fibers is 0.7-3.8mm, and the average diameter of the wollastonite fibers is 6.2-20.4μm.

[0023] By adopting the technical scheme, the wollastonite fiber and the first sizing agent are added into the pulp mixing tank. The wollastonite fiber can be electrostatically adsorbed with the components of the first sizing agent, and the components of the first sizing agent can be associated with the hydrogen bond of the paper fiber, so that the wollastonite fiber can be combined with the paper fiber under the action of the first sizing agent. On this basis, since the wollastonite fiber itself has good mechanical properties, the addition of the wollastonite fiber can improve the tensile strength of the stainless steel cushion paper.

[0024] Preferably, the average length of the wollastonite fiber is 2.4-3.8 mm.

[0025] By adopting the technical scheme, the average length of the wollastonite fiber is optimized, which is beneficial to the sufficient combination of the wollastonite fiber and the paper fiber, and improves the tensile strength of the stainless steel cushion paper.

[0026] Preferably, the amount of the wollastonite fiber is 3.2-5.7% of the weight of the compounded wood pulp absolute dry pulp.

[0027] By adopting the technical scheme, the amount of the wollastonite fiber is optimized, which is helpful to sufficiently improve the tensile strength of the stainless steel cushion paper.

[0028] Preferably, the average diameter of the wollastonite fiber is 6.2-10.8 μm.

[0029] By adopting the technical scheme, the average diameter of the wollastonite fiber is optimized, which is helpful to sufficiently improve the tensile strength of the stainless steel cushion paper.

[0030] In summary, the present application has the following beneficial effects:

[0031] 1. By introducing styrene-maleic anhydride copolymer and polyamide-epichlorohydrin resin into the cushion paper and introducing starch hydroxypropyl trimethyl ammonium chloride on the surface of the cushion paper, the hydrophilicity of the cushion paper is obviously improved, the influence of the cushion paper product on the surface tension of the stainless steel is reduced, the surface tension of the stainless steel is maintained, and the material performance can fully meet the requirements of the production process of the cylinder gasket.

[0032] 2. In the present application, carboxymethyl cellulose is preferably used as one of the components of the first sizing agent. The carboxymethyl cellulose can increase the binding force between fibers through hydrogen bond action and electrostatic adsorption, so that the addition of sodium carboxymethyl cellulose helps to improve the tensile strength of the stainless steel cushion paper. DETAILED DESCRIPTION

[0033] The present application is further described in detail below in combination with examples, preparation examples and comparative examples. The raw materials involved in the present application can be obtained by market purchase.

[0034] Examples

[0035] Examples 1-5

[0036] The following is described by taking Example 1 as an example.

[0037] Example 1

[0038] In this example, the speed of the paper production line is 570 m / min, the basis weight deviation is: standard basis weight ± 1 g. The width deviation is: standard width - 0 + 3 mm (all based on the measured width of the paper roll); in the first sizing agent, the styrene-maleic anhydride copolymer is specifically selected as styrene-maleic anhydride copolymer 2000, and the polyamide-epichlorohydrin resin is specifically selected as 1200S3 NC polyamide-epichlorohydrin resin; the second sizing agent is selected as IC 27216 biopolymer. IC 27216 biopolymer.

[0039] The present example provides a production process of hydrophilic stainless steel cushion paper, which comprises the following steps:

[0040] (1) The softwood pulp and hardwood pulp are respectively subjected to pulping, deslagging and refining, and then mixed to obtain intermediate pulp, which is transported to a pulp mixing tank after being beaten; the paper machine wet broke pulp is passed through an inclined screen and then added into the pulp mixing tank according to a weight ratio of 1:5 to be mixed with the beaten intermediate pulp to obtain compounded wood pulp; in this step, the softwood pulp is U-needle wood pulp, and the hardwood pulp is goldfish wood pulp, the weight ratio of the softwood pulp to the hardwood pulp is 0.5:0.5, both of which are bleached kraft wood pulp, and the pulping time of the softwood pulp and the hardwood pulp is 6 min / tank; the mass concentration of the intermediate pulp is 3.5%; based on the total weight of the dry pulp being 100%, the dry pulp composition of the compounded wood pulp is as follows: extractives 0.02%, ash 0.15%, polyhydric sugar 10.8%, lignin 0.17%, and the rest is alpha cellulose; the beating degree of the intermediate pulp after beating is 65.8°SR, and the wet weight is 7.2 g;

[0041] (2) The paper machine wet broke pulp is passed through an inclined screen and then added into the pulp mixing tank to be mixed with the compounded wood pulp, and the first sizing agent is added into the pulp mixing tank to obtain mixed pulp; the components of the first sizing agent include styrene-maleic anhydride copolymer and polyamide-epichlorohydrin resin; in this step, the total amount of the styrene-maleic anhydride copolymer and the polyamide-epichlorohydrin resin is 30 kg / ton of paper, and the weight ratio of the styrene-maleic anhydride copolymer to the polyamide-epichlorohydrin resin is 2:1;

[0042] (3) The mixed pulp is ground and then introduced into a papermaking pulp tank, and after being subjected to pulp washing, deslagging, sizing and screening, the mixed pulp is subjected to papermaking and pressing to obtain semi-finished cushion paper; the second sizing agent is used to size the surface of the semi-finished cushion paper at a sizing amount of 1.5 g / m 2 , and then the semi-finished cushion paper is subjected to drying, calendering and winding to obtain the final product, i.e., the hydrophilic stainless steel cushion paper with a grammage of 35 g / m 2hydrophilic stainless steel pad paper; in this step, the hard roll temperature of the second press section of the calender is 120℃, and the linear pressure is 58kN / m.

[0043] The differences between Examples 1-5 are mainly in the total amount of styrene-maleic anhydride copolymer and polyamide-epichlorohydrin resin, the amount of the second sizing agent, and the raw material ratio of the intermediate pulp.

[0044] Table 1 Total amount of styrene-maleic anhydride copolymer and polyamide-epichlorohydrin resin, amount of the second sizing agent, and raw material ratio of the intermediate pulp

[0045]

[0046] Example 6

[0047] The difference between this example and Example 5 is that the components of the first sizing agent further include sodium carboxymethyl cellulose, the degree of substitution of the sodium carboxymethyl cellulose is 0.4, the degree of polymerization is 750, and the amount of the sodium carboxymethyl cellulose is 0.4% of the weight of the compounded wood pulp on a dry basis.

[0048] The differences between Examples 6-10 are mainly in the percentage of the amount of sodium carboxymethyl cellulose based on the weight of the compounded wood pulp on a dry basis (hereinafter referred to as CMC-Na percentage) as shown in Table 2.

[0049] Table 2 CMC-Na percentage

[0050] Sample Example 6 Example 7 Example 8 Example 9 Example 10 CMC-Na % / % 0.4 0.6 0.8 1.0 1.2

[0051] Examples 10-14

[0052] The differences between Examples 10-14 are mainly in the degree of substitution of sodium carboxymethyl cellulose as shown in Table 3.

[0053] Table 3 Degree of substitution of sodium carboxymethyl cellulose

[0054] Sample Example 10 Example 11 Example 12 Example 13 Example 14 Degree of substitution 0.4 0.7 0.9 1.1 1.4

[0055] Example 15

[0056] The difference between this example and Example 14 is that the components of the first sizing agent further include cationic polyacrylamide, the average molecular weight of the cationic polyacrylamide is 350,000, and the amount of the cationic polyacrylamide is 0.12% of the weight of the compounded wood pulp on a dry basis.

[0057] The differences between Examples 15-19 are mainly in the percentage of the amount of cationic polyacrylamide based on the weight of the compounded wood pulp on a dry basis (hereinafter referred to as CPAM percentage) as shown in Table 4.

[0058] Table 4 CPAM percentage

[0059] Sample Example 15 Example 16 Example 17 Example 18 Example 19 CPAM % / % 0.12 0.20 0.32 0.41 0.50

[0060] Example 20

[0061] The difference between this example and Example 19 is that the components of the first sizing agent do not include sodium carboxymethyl cellulose.

[0062] Example 21

[0063] The difference between this example and Example 19 is that in step (2) of the production process of the hydrophilic stainless steel pad paper, wollastonite fibers and the first sizing agent are added together into the mixing chest, the amount of the wollastonite fibers is 1.4% of the weight of the compounded wood pulp absolutely dry pulp, the average length of the wollastonite fibers is 0.7 mm, and the average diameter of the wollastonite fibers is 20.4 μm.

[0064] As shown in Table 5, the difference between Examples 21-25 is that the average length of the wollastonite fibers (referred to as average length in Table 5) is different.

[0065] Table 5 Average length of wollastonite fibers

[0066] Sample Example 21 Example 22 Example 23 Example 24 Example 25 Average length / mm 0.7 1.6 2.4 3.1 3.8

[0067] Examples 25-29

[0068] As shown in Table 6, the difference between Examples 25-29 is that the percentage of the amount of the wollastonite fibers in the weight of the compounded wood pulp absolutely dry pulp (referred to as the percentage of the wollastonite fibers hereinafter) is different.

[0069] Table 6 Percentage of the wollastonite fibers

[0070] Sample Example 25 Example 26 Example 27 Example 28 Example 29 Wollastonite fibres % / % 1.4 2.6 3.2 4.5 5.7

[0071] Examples 29-33

[0072] As shown in Table 7, the difference between Examples 29-33 is that the average diameter of the wollastonite fibers (referred to as average diameter in Table 7) is different.

[0073] Table 7 Average diameter of the wollastonite fibers

[0074] Sample Example 29 Example 30 Example 31 Example 32 Example 33 Average diameter / pm 20.4 16.2 10.8 7.9 6.2

[0075] Example 34

[0076] The difference between this example and Example 33 is that the components of the first sizing agent do not include sodium carboxymethyl cellulose and cationic polyacrylamide.

[0077] Comparative Example

[0078] Comparative Example 1

[0079] The stainless steel interleaving paper prepared with reference to the specific embodiment of the Chinese patent with publication number CN105986504B has a grammage of 35 g / m 2 .

[0080] Comparative Example 2

[0081] The difference between this comparative example and Example 1 is that no first sizing agent is added into the sizing tank in step (2) of the production process of the hydrophilic stainless steel interleaving paper.

[0082] Comparative Example 3

[0083] The difference between this comparative example and Example 1 is that no sizing is performed on the semi-finished interleaving paper in step (3) of the production process of the hydrophilic stainless steel interleaving paper, and the subsequent drying, calendering and winding are directly performed.

[0084] Performance test method

[0085] I. Surface tension test

[0086] Test steps:

[0087] (1) Place the paper sheet between two steel plates, and then place the paper sheet and the steel plates together into a hot press, and treat them at a pressure of 3.5 MPa at 50℃ for 24 h, and then take them out;

[0088] (2) Open the steel plates, and use a medical absorbent cotton swab to dip 52# surface tension test mixture (Wako and Guangchun Medicine products), draw 3 lines with a width of 5 mm and a length of about 120 mm on the surface of the steel plate in contact with the paper, and observe whether the ink shrinks or breaks after 5 seconds. If the lines are complete and no ink shrinkage or breakage occurs, it indicates that the stainless steel interleaving paper can pass the 52# surface tension test mixture test, and is recorded as qualified, otherwise it is recorded as unqualified, and the results are shown in Table 8.

[0089] Supplementary verification: according to the above steps, 36-44# surface tension test mixture is used for testing, and the results show that the stainless steel interleaving paper of each example and comparative example can pass the 36-44# surface tension test mixture test.

[0090] II. Tensile strength test

[0091] The tensile strength of the stainless steel backing paper of each example and comparative example was detected according to the description of GB / T 12914-2018, and then the tensile strength of the stainless steel backing paper of each example and comparative example was calculated based on the stainless steel backing paper of comparative example 1 as the reference, and the ratio between the tensile strength of the stainless steel backing paper of each example and comparative example and the tensile strength of the stainless steel backing paper of comparative example 1 was recorded as the relative tensile strength, and the results are shown in Table 8.

[0092] Table 8: Test results of surface tension and tensile strength

[0093]

[0094] It can be seen from examples 1-34 and comparative examples 1-3 and Table 8 that the stainless steel backing paper of the present application can pass the 52# surface tension test solution, while the stainless steel backing paper of comparative examples 1-3 cannot pass. Combined with the test results of 36-44# surface tension test solution, it can be excluded that the failure of comparative examples 1-3 is caused by the production process, which indicates that the stainless steel backing paper prepared by the present application has relatively good hydrophilicity. The stainless steel backing paper of the present application has good hydrophilicity, so the influence on the surface tension of stainless steel is relatively small, which helps to maintain the surface tension of stainless steel and fully meets the requirements of the production process of the gas cylinder gasket on the material performance.

[0095] It can be seen from examples 5 and examples 6-14 and Table 8 that the relative tensile strength of examples 6-14 is greater than that of example 5, which indicates that sodium carboxymethyl cellulose can increase the binding force between fibers by forming hydrogen bonds with paper fibers and electrostatic adsorption with starch hydroxypropyl trimethyl ammonium chloride, so the addition of sodium carboxymethyl cellulose helps to improve the tensile strength of the stainless steel backing paper.

[0096] It can be seen from examples 6-10, examples 10-14 and Table 8 that when the degree of substitution of sodium carboxymethyl cellulose is 0.9-1.4 and the amount of sodium carboxymethyl cellulose is 0.8-1.2% of the weight of the compounded wood pulp, the sodium carboxymethyl cellulose has a good effect on improving the tensile strength of the stainless steel backing paper.

[0097] It can be seen from examples 14, examples 15-19 and Table 8 that after adding cationic polyacrylamide to example 14, the cationic polyacrylamide can participate in the association of hydrogen bonds and electrostatic adsorption with sodium carboxymethyl cellulose, which helps to improve the tensile strength of the stainless steel backing paper. When the amount of cationic polyacrylamide is 0.32-0.50% of the weight of the compounded wood pulp, the cationic polyacrylamide has a good effect on improving the tensile strength of the stainless steel backing paper.

[0098] It can be seen from the combination of Example 19, Example 20 and Table 8 that the cationic polyacrylamide is difficult to improve the tensile strength of the stainless steel pad paper when it is not used in combination with sodium carboxymethyl cellulose.

[0099] It can be seen from the combination of Example 19, Example 21-33 and Table 8 that the addition of wollastonite fiber helps to improve the tensile strength of the stainless steel pad paper, and when the average length of the wollastonite fiber is 2.4-3.8 mm, the amount of wollastonite fiber is 3.2-5.7% of the weight of the compounded wood pulp dry pulp, and the average diameter of the wollastonite fiber is 6.2-10.8 μm, the wollastonite fiber can produce a better improvement effect on the tensile strength of the stainless steel pad paper.

[0100] It can be seen from the combination of Example 33, Example 34 and Table 8 that the cationic polyacrylamide is difficult to improve the tensile strength of the stainless steel pad paper when it is not used in combination with sodium carboxymethyl cellulose and cationic polyacrylamide.

[0101] The specific embodiments are only an explanation of the present application, which is not a limitation of the present application, and those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. A production process for hydrophilic stainless steel pad paper, characterized in that, Includes the following steps: (1) The softwood pulp and hardwood pulp are pulped, deslag removed and refined separately, and then mixed to obtain intermediate pulp. The intermediate pulp is then sent to the mixing tank after beating. The wet loss pulp of the paper machine is added to the mixing tank after passing through an inclined screen and mixed with the beating intermediate pulp to obtain compound wood pulp. (2) Add the first sizing agent to the pulp mixing tank and mix it with the compound wood pulp to obtain a mixed pulp; the components of the first sizing agent include styrene-maleic anhydride copolymer and polyamide-epoxychloropropane resin; in this step, the sum of the amounts of styrene-maleic anhydride copolymer and polyamide-epoxychloropropane resin is 30-40 kg / ton of paper; the components of the first sizing agent also include sodium carboxymethyl cellulose, the amount of sodium carboxymethyl cellulose is 0.8-1.2% of the oven-dry weight of the compound wood pulp, and the degree of substitution of sodium carboxymethyl cellulose is 0.9-1.4; the first sizing agent The agent also includes cationic polyacrylamide, the amount of which is 0.12-0.50% of the oven-dry weight of the compound wood pulp; the amount of which is 0.32-0.50% of the oven-dry weight of the compound wood pulp; in this step, wollastonite fibers and the first sizing agent are also added to the pulp mixing tank, the amount of which is 1.4-5.7% of the oven-dry weight of the compound wood pulp, the average length of which is 0.7-3.8 mm, and the average diameter of which is 6.2-20.4 μm; (3) The mixed pulp is ground and then introduced into the papermaking tank. After rinsing, deslagging, sizing and screening, it is then papermade and pressed to obtain semi-finished padding paper. A second sizing agent is applied to the surface of the semi-finished padding paper at a ratio of 1.5-2.5 g / m 2 The sizing agent is applied in a certain amount, and then dried, calendered and wound to obtain hydrophilic stainless steel pad paper; the second sizing agent comprises starch hydroxypropyltrimethylammonium chloride.

2. The production process of the hydrophilic stainless steel pad paper according to claim 1, characterized in that, The average length of the wollastonite fibers is 2.4-3.8 mm.

3. The production process of the hydrophilic stainless steel pad paper according to claim 2, characterized in that, The amount of wollastonite fiber used is 3.2-5.7% of the oven-dry weight of the compound wood pulp.

4. The production process of the hydrophilic stainless steel pad paper according to claim 3, characterized in that, The average diameter of the wollastonite fibers is 6.2-10.8 μm.

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