Air filter paper for ultrasonic welding or hot-press bonding and preparation method thereof

Abstract

The invention belongs to the technical field of papermaking, and particularly relates to air filter paper for ultrasonic welding or hot-press bonding and a preparation method of the air filter paper. The preparation method of the air filter paper for ultrasonic welding or hot-press bonding comprises the following steps: firstly, mixing wood pulp, glass fibers, high-melting-point fibers, low-melting-point fibers, bi-component fibers and water-soluble fibers, repulping, blending and papermaking to prepare air filter base paper, then adding a waterproof agent into acrylic emulsion or styrene-acrylic emulsion to prepare coating emulsion, and finally, carrying out hot-press bonding to obtain the air filter paper for ultrasonic welding or hot-press bonding. And finally, coating air filter base paper with the coating emulsion, and drying to obtain the air filter paper for ultrasonic welding or hot-press bonding. According to the preparation method of the air filter paper provided by the invention, the prepared honeycomb filter paper can be directly welded by ultrasonic equipment, and an adhesive is replaced by an ultrasonic welding mode, so that the production cost is greatly reduced, the carbon emission is reduced, and the inherent mode of honeycomb filter processing is broken; the blank of the filter material applicable to ultrasonic waves or other hot-pressing modes is filled.

Description

Technical Field

[0001] The invention belongs to the technical field of papermaking, and in particular relates to air filter paper for ultrasonic welding or hot pressing bonding and a preparation method thereof. Background Art

[0002] As a key filter material, the demand for air filter paper is increasing day by day. This growth trend is not only reflected in the demand for traditional air filter paper, but also in the demand for new varieties of air filter paper with innovative technology and high performance. The basic function of air filter paper is to efficiently separate impurities in the air through the surface filtration mechanism to ensure air quality.

[0003] Honeycomb filter paper has gradually become the new favorite in the field of air filters due to its ultra-long life and high-efficiency filtering performance, and has received great attention from major domestic and foreign OEMs. The honeycomb filter element is made of special paper for honeycomb filters and has a unique flat paper-corrugated paper-flat paper roll structure. After the filter element is rolled, one end is used as the air intake end and the other end is closed to ensure that the air entering the filter element is purified and prevent impurities from entering the engine combustion chamber, thereby protecting the engine from damage.

[0004] However, there are some problems in the production process of traditional honeycomb filter paper. For example, traditional corrugated paper needs to be glued on one side of the closed end, which not only increases production costs but may also introduce additional pollutants. In addition, the firmness of glue bonding and wind resistance also have certain limitations, which may affect the overall performance of the filter element.

[0005] Patent CN214782930U proposes a honeycomb filter element corrugated composite filter paper, which forms folds by flattening on both sides, shortens the dripping stroke, reduces deformation accumulation, and improves the uniformity of fold distribution, thereby enhancing the wind resistance and burst resistance of the flattened end and reducing the risk of sealing leakage. However, this method still relies on the use of adhesives and still has the problem of environmental pollution. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for preparing air filter paper for ultrasonic welding or hot pressing bonding. The prepared honeycomb filter paper can be directly welded using ultrasonic equipment, replacing the use of adhesives with ultrasonic welding, which greatly reduces production costs and carbon emissions, breaks the inherent mode of honeycomb filter processing, and fills the gap in filter materials suitable for ultrasonic or other hot pressing modes.

[0007] The method for preparing air filter paper for ultrasonic welding or hot pressing bonding of the present invention comprises the following steps: firstly, softwood pulp, hardwood pulp, glass fiber, high melting point fiber, low melting point fiber, bicomponent fiber and water-soluble fiber are mixed and pulped, and pulped to obtain air filter base paper; then, a waterproofing agent is added to acrylic emulsion or styrene acrylic emulsion to obtain a coating emulsion; finally, the coating emulsion is coated on the air filter base paper; and after drying, the air filter paper for ultrasonic welding or hot pressing bonding is obtained;

[0008] The coniferous wood pulp, hardwood wood pulp, glass fiber, high melting point fiber, low melting point fiber, bicomponent fiber, and water-soluble fiber are mixed in the following weight proportions: 5-12 parts, 15-25 parts, 8.4-12.4 parts, 24-48 parts, 5-15 parts, 1.6-7.6 parts, and 8-15 parts.

[0009] The air permeability of the softwood pulp is 400-800, the air permeability of the hardwood pulp is 80-250, the glass fiber is glass fiber wool with a beating degree of 20-60°SR, and the corresponding fiber diameter of the glass fiber is 10μm-500nm.

[0010] The high melting point fiber is a fiber with a melting point of 165-190° C., 0.2-3D, and a length of 4-6 mm, preferably PET, PA, or PU.

[0011] The low melting point fiber is a fiber with a melting point of 125-160° C. and a density of 1-5D, preferably PP or PE.

[0012] The bicomponent fiber is a sheath-core structure fiber with a melting point of 100-120°C, 1-5D, and a length of 4-6mm;

[0013] The water-soluble fiber is a fiber with a diameter of 1-5D and a length of 4-6 mm, preferably a vinylon or carboxymethyl cellulose fiber.

[0014] After mixing coniferous wood pulp, broadleaf wood pulp, glass fiber, high melting point fiber, low melting point fiber, bicomponent fiber and water-soluble fiber, water and sulfuric acid are added and the pulp is pulverized.

[0015] The pulp concentration is 0.5-2.5wt%, and the pulp concentration is 0.2-2wt%.

[0016] The concentration of the coating emulsion is 10-30wt%.

[0017] The coating emulsion is coated on the air filter base paper, and the coating amount is 5-30wt%.

[0018] An air filter paper for ultrasonic welding or hot pressing bonding is prepared by the preparation method of the air filter paper for ultrasonic welding or hot pressing bonding, and is used for preparing honeycomb filter of ultrasonic origami equipment.

[0019] Specifically, the method for preparing the air filter paper for ultrasonic welding or thermal compression bonding comprises the following steps:

[0020] (1) Weigh 5-12 parts of softwood pulp, 15-25 parts of hardwood pulp, 8.4-12.4 parts of glass fiber, 24-48 parts of high melting point fiber, 5-15 parts of low melting point fiber, 1.6-7.6 parts of bicomponent fiber, and 8-15 parts of water-soluble fiber, respectively, and put them into a hydraulic pulper in sequence. Add 7m 3 water, add 500mL sulfuric acid, and make a dispersed slurry after pulping, the pulping concentration is 0.5-2.5wt%, and the slurry concentration is 0.2-2wt%;

[0021] (2) After pulping, dehydration, forming, drying, and winding in the papermaking process, air filter base paper is produced;

[0022] (3) Weighing 500 kg of acrylic emulsion, adding 20 kg of waterproofing agent, stirring evenly, and preparing a coating emulsion, the concentration of the coating emulsion is 10-30 wt%; the waterproofing agent is one of MF, PAPU, aziridine or silicone;

[0023] (4) The prepared coating emulsion is evenly coated on the prepared air filter base paper, with the coating amount being 5-30wt%, and after drying in a drying cylinder, an air filter paper for ultrasonic welding or hot pressing bonding is obtained.

[0024] The high melting point fiber of the present invention plays a key role in the heat sealing effect, and its cost is lower than that of other fibers, thereby reducing the overall cost of the product; the low melting point fiber enhances the adaptability of ultrasonic welding strength or hot pressing temperature, avoiding the risk of poor heat sealing when the strength or temperature is insufficient; the bicomponent fiber increases the strength of the filter paper, avoiding the risk of the filter paper being blown apart during use due to excessive synthetic fiber content, poor fiber bonding, and low strength, and is beneficial to the heat sealing effect. The specific ratio of the high melting point fiber to the bicomponent fiber enhances the heat sealing effect; the low melting point fiber enhances the adaptability of ultrasonic welding strength or hot pressing temperature, avoiding the risk of poor heat sealing when the strength or temperature is insufficient; the glass fiber improves the filtration accuracy of the filter paper, and the addition of the glass fiber The pore size of the filter paper is greatly reduced, and the requirement of high efficiency F7 (0.4μm efficiency 80-90%) of the nano honeycomb filter is also achieved. Since the nano layer of the nano honeycomb filter is easily damaged, and the glass fiber has higher strength and firmness, the use of glass fiber increases the stability of the high efficiency of the high efficiency honeycomb filter; the water-soluble fiber has good dispersibility, which increases the uniformity and strength of the filter paper; the coniferous wood pulp has good fiber strength and fiber bonding force, so that the filter paper has good strength and stiffness; compared with the coniferous wood pulp, although the strength of the broadleaf wood pulp fiber is lower, the fiber bonding force is much greater than the bonding force between synthetic fibers, because the broadleaf wood pulp improves the strength and stiffness of the filter paper, and the diameter of the broadleaf wood pulp is thinner than that of the coniferous wood pulp fiber, which is conducive to reducing the pore size and improving the filtering efficiency. In addition, compared with the synthetic fiber, the present invention has more hydrogen bonds between the wood pulp fibers, so the paper is tighter, thereby reducing the thickness of the filter paper, which is conducive to the formation of the corrugated layer in the honeycomb filter and the channel is smoother.

[0025] The air filter paper prepared by the present invention is suitable for the honeycomb filter paper of ultrasonic origami equipment. In addition to being used for automobile honeycomb filter dedicated to ultrasonic equipment, it can also be used for other filter papers or other products processed by ultrasonic or hot pressing bonding.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The air filter paper for ultrasonic welding or hot pressing bonding prepared by the method of the present invention has the advantages of both full synthetic and wood pulp paper air filters, such as high filtration efficiency, good stiffness, low thickness, and is conducive to honeycomb molding process.

[0028] (2) The air filter paper for ultrasonic welding or hot pressing bonding prepared by the method of the present invention is different from the previous honeycomb air filter paper for automobiles, which must be glued to achieve the purpose of direct bonding between papers. The air filter papers of the present invention are self-bonded by the high-temperature melting characteristics of chemical fibers, and ultrasonic welding is directly used instead of adhesives, which greatly reduces production costs and carbon emissions, breaks the inherent mode of honeycomb filter processing, and fills the gap in filter materials that can be used in ultrasonic or other hot pressing modes without gluing.

[0029] (3) The method for preparing air filter paper for ultrasonic welding or hot pressing bonding of the present invention, in which the slurry prepared by mixing coniferous wood pulp, hardwood pulp, nano-grade glass fiber, high melting point fiber, bicomponent chemical fiber and water-soluble fiber is mixed, greatly reduces the pore size of the filter paper, and also achieves the requirement of high efficiency F7 (0.4μm filtration efficiency 80-90%) of nano honeycomb filtration without covering with a nano layer, thus avoiding the problem of easy damage of the nano layer of the nano honeycomb filter covered with a nano layer. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with specific embodiments.

[0031] The raw materials and additives used in the following examples and comparative examples are all commercially available products. The weight parts of the present invention are all calculated in kg. The softwood pulp used is the brand Alabama, and the hardwood pulp is the brand Goldfish.

[0032] Example 1

[0033] The method for preparing the air filter paper for ultrasonic welding or hot pressing bonding comprises the following steps:

[0034] (1) Weigh 7 kg of softwood pulp (air permeability 550), 19 kg of hardwood pulp (air permeability 150), 10 kg of glass fiber (beating degree 50°SR), 38 kg of high melting point fiber (melting point 190°C, 1.67D, length 6 mm PET fiber), 10 kg of low melting point fiber (melting point 150°C, 3D, length 6 mm PP fiber), 7 kg of bicomponent fiber (5D, length 5 mm ES fiber), and 9 kg of water-soluble fiber (3D, length 6 mm vinylon fiber, water-soluble temperature 80°C), and put them into a hydraulic pulper in sequence. Add 7m 3 water, add 500mL 98wt% sulfuric acid, and make a dispersed slurry after pulping. The pulping concentration is 1.7wt% and the slurry concentration is 1wt%;

[0035] (2) After pulping, dehydration, forming, drying, and winding in the papermaking process, air filter base paper is produced;

[0036] (3) preparing acrylic emulsion, weighing 500 kg of acrylic emulsion, adding 20 kg of PAPU waterproofing agent, stirring evenly, and preparing coating emulsion, the concentration of coating emulsion is 25 wt%;

[0037] (4) The prepared coating emulsion is evenly coated on the prepared air filter base paper, with the coating amount being 18 wt %. After drying in a drying cylinder, air filter paper for ultrasonic welding or hot pressing bonding is obtained.

[0038] Example 2

[0039] The method for preparing the air filter paper for ultrasonic welding or hot pressing bonding comprises the following steps:

[0040] (1) Weigh 12 kg of softwood pulp (air permeability 800), 15 kg of hardwood pulp (air permeability 80), 10 kg of glass fiber (beating degree 40°SR), 28 kg of high melting point fiber (melting point 170°C, 3D, length 4 mm PA fiber), 8 kg of low melting point fiber (melting point 100°C, 3D, length 6 mm PE fiber), 5 kg of bicomponent fiber (3D, length 6 mm ES fiber), and 12 kg of water-soluble fiber (5D, length 4 mm vinylon fiber, water-soluble temperature 80°C), and put them into a hydraulic pulper in sequence. Add 7m 3 water, add 500mL 98wt% sulfuric acid, and make a dispersed slurry after pulping, the pulping concentration is 0.5wt%, and the pulping concentration is 1.5wt%;

[0041] (2) After pulping, dehydration, forming, drying, and winding in the papermaking process, air filter base paper is produced;

[0042] (3) preparing acrylic emulsion, weighing 500 kg of acrylic emulsion, adding 20 kg of PAPU waterproofing agent, stirring evenly, and preparing coating emulsion, the concentration of the coating emulsion is 30 wt%;

[0043] (4) The prepared coating emulsion is evenly coated on the prepared air filter base paper, with a coating amount of 10 wt %, and after drying in a drying cylinder, an air filter paper for ultrasonic welding or hot pressing bonding is obtained.

[0044] Example 3

[0045] The method for preparing the air filter paper for ultrasonic welding or hot pressing bonding comprises the following steps:

[0046] (1) Weigh 5 kg of softwood pulp (air permeability 400), 10 kg of hardwood pulp (air permeability 200), 8.4 kg of glass fiber (beating degree 60°SR), 24 kg of high melting point fiber (melting point 180°C, 1.0D, length 6 mm PU fiber), 5 kg of low melting point fiber (melting point 160°C, 1D, length 4 mm PE fiber), 7.6 kg of bicomponent fiber (5D, length 4 mm ES fiber), and 8 kg of water-soluble fiber (3D, length 5 mm vinylon fiber, water-soluble temperature 80°C), and put them into a hydraulic pulper in sequence. Add 7m 3 water, add 500mL 98wt% sulfuric acid, and make a dispersed slurry after pulping. The pulping concentration is 1.7wt% and the slurry concentration is 2wt%;

[0047] (2) After pulping, dehydration, forming, drying, and winding in the papermaking process, air filter base paper is produced;

[0048] (3) preparing acrylic emulsion, weighing 500 kg of acrylic emulsion, adding 20 kg of PAPU waterproofing agent, stirring evenly, and preparing coating emulsion, the concentration of coating emulsion is 25 wt%;

[0049] (4) The prepared coating emulsion is evenly coated on the prepared air filter base paper, with a coating amount of 5 wt %. After drying in a drying cylinder, air filter paper for ultrasonic welding or hot pressing bonding is obtained.

[0050] Example 4

[0051] The method for preparing the air filter paper for ultrasonic welding or hot pressing bonding comprises the following steps:

[0052] (1) Weigh 10 kg of softwood pulp (air permeability 600), 25 kg of hardwood pulp (air permeability 250), 12.4 kg of glass fiber (beating degree 30°SR), 45 kg of high melting point fiber (melting point 165°C, 0.2D, length 6 mm PET fiber), 15 kg of low melting point fiber (melting point 120°C, 5D, length 6 mm PP fiber), 4.6 kg of bicomponent fiber (1D, length 5 mm ES fiber), and 15 kg of water-soluble fiber (3D, length 4 mm carboxymethyl cellulose fiber, water-soluble temperature 80°C), and put them into a hydraulic pulper in sequence. Add 7m 3 water, add 500mL 98wt% sulfuric acid, and make a dispersed slurry after pulping, the pulping concentration is 2.5wt%, and the slurry concentration is 0.2wt%;

[0053] (2) After pulping, dehydration, forming, drying, and winding in the papermaking process, air filter base paper is produced;

[0054] (3) preparing acrylic emulsion, weighing 500 kg of acrylic emulsion, adding 20 kg of PAPU waterproofing agent, stirring evenly, and preparing coating emulsion, the concentration of the coating emulsion is 10 wt%;

[0055] (4) The prepared coating emulsion is evenly coated on the prepared air filter base paper, with a coating amount of 30 wt %. After drying in a drying cylinder, an air filter paper for ultrasonic welding or hot pressing bonding is obtained.

[0056] Comparative Example 1

[0057] Compared with Example 1, this comparative example removes 38 kg of high melting point fiber, and the other proportions and preparation are exactly the same as those in Example 1, thereby obtaining an air filter paper.

[0058] Comparative Example 2

[0059] Compared with Example 1, this comparative example removes 10 kg of glass fiber, and the other proportions and preparation are exactly the same as those in Example 1, thereby obtaining an air filter paper.

[0060] Comparative Example 3

[0061] Compared with Example 1, this comparative example removes 9 kg of water-soluble fiber, and the other proportions and preparation are exactly the same as those in Example 1, thereby obtaining an air filter paper.

[0062] Comparative Example 4

[0063] Compared with Example 1, this comparative example replaces the "7kg of coniferous wood pulp and 19kg of hardwood wood pulp" in Example 1 with 26kg of hardwood wood pulp. Other proportions and preparation are exactly the same as in Example 1, thereby obtaining an air filter paper.

[0064] Comparative Example 5

[0065] Compared with Example 1, this comparative example removes 10 kg of low-melting-point fibers, and the other proportions and preparation are exactly the same as those in Example 1, thereby obtaining an air filter paper.

[0066] The air filter papers prepared in the examples and comparative examples were measured according to the following standards:

[0067] Quantitative determination: GB / T451.2-2002;

[0068] Thickness measurement: GB / T451.3-2002;

[0069] Maximum pore size determination: GB / T2679.14-1996;

[0070] Air permeability determination: GB / T 22819-2008;

[0071] 0.4μm filtration efficiency determination: EN779 (requires 80%-90%);

[0072] Burst strength test: GB / T454-2002;

[0073] Stiffness: GB / T22364-2018;

[0074] Determination of heat sealability: using the company's internal standard RQB / R-CB002 for testing, the specific testing steps are as follows:

[0075] 1. Turn on the power of the heat press machine and confirm whether the power supply is normal.

[0076] 2. Confirm whether the positions of the temperature adjustment buttons and pressure adjustment buttons of the heat press are normal.

[0077] 3. According to the process requirements, set the working temperature (180℃) and time (30s) of the hot press.

[0078] 4. Place the paper sample to be tested on the hot pressure test surface and press the start button.

[0079] 5. After the test, take out the test paper sample and observe the heat seal strength.

[0080] The judging method is: if it needs to be torn hard and there are obvious marks of adhesion between the papers, it is judged as very good; if it needs to be torn hard but there are no obvious marks of adhesion between the papers, it is judged as good; if it can be separated by tearing with less force, it is judged as fair; if it can be separated without tearing hard, it is judged as poor.

[0081] The above test results are shown in Table 1.

[0082] Table 1 Performance parameter test results

[0083]

[0084]

[0085] From the comparison between Example 1 and Comparative Example 1, it can be seen that high melting point fiber plays a key role in heat sealing; from the comparison between Example 1 and Comparative Example 2, it can be seen that the addition of glass fiber improves the product qualification rate; from the comparison between Example 1 and Comparative Example 3, it can be seen that the addition of water-soluble fiber increases the strength and synergistically improves the stiffness of the paper; from the comparison between Example 1 and Comparative Example 4, it can be seen that the addition of coniferous pulp fiber increases the strength and stiffness of the paper; from the comparison between Example 1 and Comparative Example 5, it can be seen that the addition of low melting point chemical fiber enhances the ultrasonic welding strength or the adaptability of the hot pressing temperature, avoiding the risk of poor heat sealing when the strength or temperature is insufficient.

Claims

1. A method for preparing air filter paper for ultrasonic welding or thermal pressure bonding, characterized in that: First, softwood pulp, hardwood pulp, glass fiber, high melting point fiber, low melting point fiber, bicomponent fiber, and water-soluble fiber are mixed and pulverized, and the slurry is prepared to obtain air filter base paper. Then, acrylic emulsion or styrene acrylic emulsion is added with a waterproofing agent to obtain a coating emulsion. Finally, the coating emulsion is coated on the air filter base paper. After drying, the air filter paper for ultrasonic welding or hot pressing bonding is obtained. The coniferous wood pulp, hardwood wood pulp, glass fiber, high melting point fiber, low melting point fiber, bicomponent fiber, and water-soluble fiber are mixed in the following weight proportions: 5-12 parts, 15-25 parts, 8.4-12.4 parts, 24-48 parts, 5-15 parts, 1.6-7.6 parts, and 8-15 parts.

2. The method for preparing air filter paper for ultrasonic welding or thermal pressure bonding according to claim 1, characterized in that: The air permeability of the softwood pulp is 400-800, the air permeability of the hardwood pulp is 80-250, the glass fiber is glass fiber wool with a beating degree of 20-60°SR, and the corresponding fiber diameter of the glass fiber is 10μm-500nm.

3. The method for preparing air filter paper for ultrasonic welding or thermal pressure bonding according to claim 1, characterized in that: The high melting point fiber is a fiber with a melting point of 165-190°C, 0.2-3D, and a length of 4-6mm; the low melting point fiber is a fiber with a melting point of 125-160°C, and 1-5D.

4. The method for preparing air filter paper for ultrasonic welding or thermal pressure bonding according to claim 1, characterized in that: The bicomponent fiber is a core-skin structure fiber with a melting point of 100-120° C., 1-5D, and a length of 4-6 mm; the water-soluble fiber is a fiber with a 1-5D and a length of 4-6 mm.

5. The method for preparing air filter paper for ultrasonic welding or thermal pressure bonding according to claim 1, characterized in that: After mixing coniferous wood pulp, broadleaf wood pulp, glass fiber, high melting point fiber, low melting point fiber, bicomponent fiber and water-soluble fiber, water and sulfuric acid are added and the pulp is pulverized.

6. The method for preparing air filter paper for ultrasonic welding or thermal pressure bonding according to claim 1, characterized in that: The pulp concentration is 0.5-2.5wt%, and the pulp concentration is 0.2-2wt%.

7. The method for preparing air filter paper for ultrasonic welding or thermal pressure bonding according to claim 1, characterized in that: The concentration of the coating emulsion is 10-30wt%.

8. The method for preparing air filter paper for ultrasonic welding or thermal pressure bonding according to claim 1, characterized in that: The coating emulsion is coated on the air filter base paper, and the coating amount is 5-30wt%.

9. An air filter paper for ultrasonic welding or thermal pressure bonding, characterized in that: The air filter paper is prepared by the method for preparing air filter paper for ultrasonic welding or thermal compression bonding as described in any one of claims 1 to 8.

10. The air filter paper for ultrasonic welding or thermal pressure bonding according to claim 9, characterized in that: It is used to prepare honeycomb filters for ultrasonic origami devices.

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