Nonwoven composite sheet and method for making same

Abstract

The present application relates to the technical field of nonwoven fabric preparation, and in particular to a nonwoven composite sheet and a preparation method thereof. Among them, a nonwoven composite sheet comprises a first surface layer, a core layer and a second surface layer; the first surface layer and the second surface layer are made of flash spun fibers; the core layer is made of spunbond fibers; the weight of the core layer accounts for greater than or equal to 10% and less than or equal to 30% of the total weight. The nonwoven composite sheet provided by the present application uses the core layer spunbond fibers as the skeleton, which significantly improves the tensile breaking strength and tearing strength of the nonwoven composite sheet without affecting the performance of the material itself, and at the same time improves the stiffness of the nonwoven composite sheet. In addition, since the core layer spunbond fibers are low-melting point fibers, the morphology of the flash spun fibers does not change significantly after they are melted and bonded, so the peeling strength of the nonwoven composite sheet is also significantly improved, and it has higher air permeability.

Description

Technical Field

[0001] The present application relates to the technical field of nonwoven fabric preparation, and in particular to a nonwoven composite sheet and a preparation method thereof. Background Art

[0002] In the prior art, a method for simultaneously ensuring the peel strength and opacity of flash-spun sheets is to add pigments to the raw material slices. For example, patent CN1090260C "Improved Flash Spinning Sheet" discloses an improved sheet composed of a bonded ultrafine plexifilamentary film-fibril bundle spun from polyolefin and pigment. The polyolefin accounts for at least 90% of the weight of the fibril bundle, and the pigment accounts for 0.05-10% of the weight of the fibril bundle. The sheet still has high opacity even after being bonded to a delamination strength greater than 120N / m. Although this method is feasible, the sheet after adding pigments is not conducive to recycling, which is not conducive to the reusability of the material and affects its environmental attributes. Summary of the invention

[0003] For flash-steamed nonwoven fabrics, in order to ensure that they have the characteristics of paper and a certain stiffness, they need to be hot-calendered (calendered) to make the fibers thermally bonded; however, in order to ensure that they have a certain air permeability, too high a temperature and pressure cannot be used, otherwise the fibers of the entire facade layer will be melted, making it non-breathable, and the opacity of the material will also be reduced, and the tear strength will also be significantly reduced; but the temperature and pressure cannot be low, otherwise only the surface of the fabric will be thermally bonded. Although the air permeability, opacity and tear strength are maintained, the stiffness of the material is obviously insufficient, and a form of two upper and lower thermally bonded layers and a middle pure fiber layer is formed, which will cause the upper and lower layers of the fabric to be easily peeled off, which is not conducive to the use of the product.

[0004] To solve the corresponding deficiencies, the present application provides a nonwoven composite sheet, comprising

[0005] A first surface layer, a core layer and a second surface layer.

[0006] The first surface layer and the second surface layer are made of flash spun fibers, and the core layer is made of spunbond fibers.

[0007] The weight of the core layer accounts for greater than or equal to 10% and less than or equal to 30% of the total weight.

[0008] In one embodiment, the flash spun fiber raw material is high-density polyethylene, and the melting point of high-density polyethylene is greater than or equal to 130° C. and less than or equal to 135° C. The spunbond fiber raw material is low-density polyethylene, and the melting point of low-density polyethylene is greater than or equal to 100° C. and less than or equal to 110° C.

[0009] In one embodiment, the overall total weight is greater than or equal to 40 g / m 2 And less than or equal to 120g / m2 .

[0010] In one embodiment, the weight of the core layer accounts for greater than or equal to 11% and less than or equal to 20% of the total weight. More preferably, the weight of the core layer accounts for greater than or equal to 15% and less than or equal to 20% of the total weight.

[0011] In one embodiment, the gram weight of the first surface layer and the second surface layer accounts for greater than or equal to 10% and less than or equal to 80% of the total gram weight respectively.

[0012] Preferably, the gram weight of the first surface layer and the second surface layer accounts for the same proportion in the total gram weight.

[0013] Preferably, the weight of the first surface layer and the second surface layer account for different proportions in the total weight. Further, the difference in the weight of the first surface layer and the second surface layer in the total weight is no more than 15%.

[0014] In one embodiment, the stiffness is greater than or equal to 20 mN.cm and less than or equal to 45 mN.cm.

[0015] In one embodiment, the air permeability is greater than or equal to 18 mm / s and less than or equal to 40 mm / s.

[0016] The present application also provides a method for preparing any of the nonwoven composite sheets described above, the steps being as follows:

[0017] The flash-spun fiber raw material is flash-spun and sprayed out to form a fiber mesh, and the fiber mesh forms a fiber net on the mesh curtain;

[0018] The fiber web is cold pressed, and the melted spunbond fibers are condensed on the cold pressed fiber web to obtain a two-layer composite fiber web;

[0019] cold-pressing the two-layer composite fiber web, and stacking a fiber mesh sheet made of flash-spun fibers on the spunbond fiber surface of the cold-pressed two-layer composite fiber web to obtain a three-layer composite fiber web;

[0020] The three-layer composite fiber web is preheated and pressed, and then hot-air shaped and hot-calendered to obtain a non-woven composite sheet.

[0021] In one embodiment, the hot air setting temperature is higher than the melting point of the spunbond fibers and lower than the melting point of the flash spun fibers.

[0022] In one embodiment, the specific preparation process of the fiber web is: high-density polyethylene chips and their matching solvents are mixed in a high-temperature and high-pressure reactor to dissolve and form a uniform solution, which is sprayed out through the spinneret holes of the nozzle to form a fiber bundle containing many ultrafine fibers. The fiber bundle is refracted and diverged through a rotating filament separator to form a fiber mesh with a mesh structure. The continuously formed fiber mesh is stacked on a moving mesh curtain to form a fiber web with a certain gram weight and width.

[0023] In one embodiment, the specific preparation process of the two-layer composite fiber web is as follows: low-density polyethylene chips are added to a screw extruder, heated and melted by the screw extruder, quantitatively metered by a metering pump, and extruded through a die head to form a spinning stream, which is stretched into fibers under the action of strong wind force, and the fibers are condensed on the flash-spun fiber web transmitted from the previous process to form a two-layer composite fiber web.

[0024] In one embodiment, the specific preparation process of the three-layer composite fiber web is as follows: high-density polyethylene chips and their matching solvents are mixed in a high-temperature and high-pressure reactor to dissolve and form a uniform solution, which is sprayed out through the spinneret holes of the nozzle to form a fiber bundle containing many ultrafine fibers. The fiber bundle is refracted and diverged through a rotating filament separator to form a fiber mesh with a mesh structure. The continuously formed fiber mesh is stacked on the two-layer composite fiber web transmitted from the previous process, and a layer of flash spun fiber is stacked on the spunbond fiber of the core layer to obtain a three-layer composite fiber web.

[0025] Preferably, the roller surface temperature of the hot calendering roll is greater than or equal to 120° C. and less than or equal to 150° C., the roller oil pressure is 1.5 to 5.0 MPa, and the roller surface speed is 20 to 60 m / min.

[0026] Preferably, the diameter of the spunbond fiber is greater than or equal to 15 μm and less than or equal to 25 μm, and the diameter of the flash spun fiber is greater than or equal to 0.5 μm and less than or equal to 2 μm.

[0027] Based on the above, compared with the prior art, the embodiments of the present application have the following beneficial effects:

[0028] 1. The nonwoven composite sheet provided in the embodiment of the present application uses spunbond fibers in the material core layer. The spunbond fibers are relatively coarse and the fibers are arranged sparsely. When the fibers melt after heating, if densely arranged fine fibers such as flash spinning or melt blowing are used, the fine fibers will be connected to each other to form an airtight film. The coarser spunbond fibers are sparsely arranged and can still retain more holes when they melt, ensuring the air permeability of the entire nonwoven composite sheet. At the same time, after the spunbond fibers are melted and then cooled and solidified and crystallized, a skeleton structure can be formed to improve the stiffness of the nonwoven composite sheet.

[0029] 2. The embodiment of the present application adopts the core layer spunbond fiber as the skeleton, which significantly improves the tensile breaking strength and tearing strength of the non-woven composite sheet without affecting the performance of the material itself, and at the same time improves the stiffness of the non-woven composite sheet. In addition, since the core layer spunbond fiber is a low melting point fiber, the morphology of the flash-spun fiber does not change significantly after it is melt-bonded, so the peeling strength of the non-woven composite sheet is also significantly improved, and it has higher air permeability.

[0030] 3. In the preparation method adopted in the embodiment of the present application, when the three-layer composite fiber web is heat-set, the spunbond fibers of the low-density polyethylene in the core layer are partially melted, while the morphology of the flash-spun fibers does not change substantially, so that the molten fibers can firmly hold the upper and lower layers of flash-spun fibers together. After the three-layer composite fiber web is shaped and cooled, the molten spunbond fibers re-solidify and crystallize to form a skeleton structure, which effectively improves the stiffness of the product. Finally, the shaped three-layer composite fiber web is hot-calendered on the upper and lower surfaces, so that the flash-spun fibers of the first and second surface layers are thermally bonded on the surface and a smooth surface is formed, so that the fibers on the vertical surface of the non-woven composite sheet are bonded, while the internal fibers still maintain the fiber morphology, ensuring the overall air permeability and mechanical properties.

[0031] Other features and beneficial effects of the present application will be described in the subsequent description, and partly become apparent from the description, or understood by practicing the present application. The purpose and other beneficial effects of the present application can be realized and obtained by the structures specifically pointed out in the description, claims and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can also be obtained based on these drawings without creative work. The positional relationships described in the drawings in the following description are based on the directions of the components in the drawings unless otherwise specified.

[0033] Figure 1 It is a structural schematic diagram of an embodiment of the present application.

[0034] Figure 2 A schematic diagram of a preparation method according to an embodiment of the present application

[0035] Reference numerals:

[0036] 100 first surface layer 200 core layer 300 second surface layer DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The technical features designed in the different implementation modes of the present application described below can be combined with each other as long as they do not conflict with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0038] In the description of this application, it should be noted that all terms (including technical terms and scientific terms) used in this application have the same meaning as those commonly understood by ordinary technicians in the field to which this application belongs, and cannot be understood as limiting this application. It should be further understood that the terms used in this application should be understood to have the same meaning as the meaning of these terms in the context of this specification and the relevant field, and should not be understood in an idealized or overly formal sense, unless explicitly defined in this application.

[0039] Embodiment 1:

[0040] A certain type of HDPE chips from Sinopec was selected, and the HDPE chips with a mass concentration of 15% and the solvent with a mass concentration of 85% (a mixture of 15% difluorochloromethane (R22) and 85% tetrafluorodichloroethane (R114)) were added to the autoclave at the same time and heated to 180°C. After the heating was completed, nitrogen was introduced and pressurized to 12MPa, and the temperature was raised to 230°C at the same time, and stirred for 2h at a stirring speed of 100r / min. After the temperature stabilized, a uniform spinning solution was formed in the autoclave. The uniform solution was sprayed out through the spinneret of the nozzle to form a fiber bundle containing many ultrafine fibers. The fiber bundle was refracted and diverged through the rotating filament plate into a fiber mesh with a mesh structure. The continuously formed fiber mesh was stacked on the moving mesh curtain to form a fiber mesh. The fiber mesh entered the next process after cold pressing. The weight of the flash-spun fiber layer was 20g / m 2 .

[0041] A certain type of LDPE slice from Sinopec is heated and melted by a screw extruder, quantitatively metered by a metering pump, and extruded through a die head to form a spinning stream. The spinning stream is drawn into fibers under the action of strong wind force, and the fibers are condensed on the flash spun fiber web transmitted from the previous process to form a two-layer composite fiber web. The composite fiber web enters the next process after cold pressing. The spunbond layer fiber weight is 20g / m 2 The weight of the two-layer composite fiber web is 40g / m 2 .

[0042] According to the same formula as step 1, a uniform spinning solution is made. The uniform solution is sprayed out through the spinneret of the nozzle to form a fiber bundle containing many ultrafine fibers. The fiber bundle is refracted and diverged by the rotating filament separator to form a fiber mesh with a mesh structure. The continuously formed fiber mesh is stacked on the composite fiber transmitted from the previous process, and the newly formed flash-spun fibers are stacked on top of the spunbond fiber web to form a composite fiber web with a three-layer structure. The composite fiber web enters the next process after preheating and pressing (roller surface temperature 90°C, pressure 0.7MPa). The weight of the upper flash-spun fiber layer is 20g / m 2 The weight of the three-layer composite fiber web is 60g / m 2 .

[0043] The preheated grey fabric enters the hot air stenter setting machine, the setting machine temperature is set to 124℃, the speed is 25m / min, and the set grey fabric enters the hot calendering process. The roller surface temperature is 131℃, and the pressure is 3.5MPa. The desired nonwoven composite sheet is obtained.

[0044] Example 2-3, as shown in Table 1, except that the weight of the core layer is changed to 10 g / m 2 , 5g / m 2 Except for this, everything else is the same as Example 1.

[0045] Example 4, as shown in Table 1, except that the weight of the first surface layer and the second surface layer is changed to 30g / m 2 , the roller surface temperature is 132°C, and the pressure is 4.0 MPa, and the rest is the same as in Example 1.

[0046] Example 5-6. As shown in Table 1, except that the weight of the core layer is changed to 10 g / m 2 , 5g / m 2 , the rest is the same as Example 4.

[0047] Comparative Example 1:

[0048] Select the same HDPE slices as in Example 1, add 15% HDPE slices and 85% solvent (a mixture of 15% difluorochloromethane (R22) and 85% tetrafluorodichloroethane (R114)) at a mass concentration into a high-pressure reactor and heat it to 180°C. After the heating is completed, nitrogen is introduced to increase the pressure to 12MPa, and the temperature is raised to 230°C at the same time, and stirred for 2 hours at a stirring speed of 100r / min. After the temperature stabilizes, a uniform spinning solution is formed in the high-pressure reactor. The uniform solution is ejected through the spinneret hole of the nozzle to form a fiber bundle containing many ultrafine fibers. The fiber bundle is refracted and diverged by the rotating filament separator to form a fiber mesh with a mesh structure. The continuously formed fiber mesh is stacked on the moving mesh curtain to form a fiber net with a gram weight of 60g / m 2After cold pressing, the fiber web enters the hot calendering process. The surface temperature of the hot roller of the hot calendering is 132°C and the pressure is 4.5MPa.

[0049] Comparative Example 2: As shown in Table 1, the formula is the same as that of Comparative Example 1, and the fiber web weight is also 60g / m 2 The surface temperature of the hot roller of the hot calendering was 129°C and the pressure was 4.5 MPa.

[0050] Comparative Example 3: As shown in Table 1. The formula is the same as that of Comparative Example 1, and the fiber web weight is also 60g / m 2 The surface temperature of the hot roller of the hot calendering was 135°C and the pressure was 4.5 MPa.

[0051] Comparative Example 4: As shown in Table 1, the formula is the same as that of Comparative Example 1, and the fiber mesh weight is 70g / m 2 The surface temperature of the hot roller of the hot calendering was 133°C and the pressure was 4.5 MPa.

[0052] Comparative Example 5: As shown in Table 1, the formula is the same as that of Comparative Example 1, and the fiber mesh weight is 70g / m 2 The surface temperature of the hot roller of the hot calendering was 130°C and the pressure was 4.5 MPa.

[0053] Comparative Example 6: As shown in Table 1, the formula is the same as that of Comparative Example 1, and the fiber mesh weight is 70g / m 2 The surface temperature of the hot roller of the hot calendering was 136°C and the pressure was 4.5 MPa.

[0054] Table 1 Examples and Comparative Examples Formulations and Process

[0055]

[0056]

[0057] The performance of each embodiment and comparative example was tested, and the specific items and results are shown in Table 2.

[0058] Table 2 Performance test

[0059]

[0060]

[0061] It can be seen from the data in Table 2 that the peel strength and stiffness of the ordinary flash spun sheets of Comparative Examples 1 to 6 increase with increasing hot calendering temperature, but the air permeability and tear strength decrease. When the hot calendering temperature of the ordinary flash spun sheets decreases, the air permeability and tear strength increase, but the peel strength and stiffness decrease.

[0062] The nonwoven composite sheets provided in Examples 1 to 6 of the present application have low-melting-point spunbond fibers added to the core layer, so that the peel strength and stiffness of the nonwoven composite sheets are still maintained at high levels, and the tear strength does not decrease.

[0063] And it can be seen from Examples 1 to 6 that when there are too few spunbond fibers in the core layer, the spunbond fibers will not work, and the performance of the nonwoven composite sheet will not be significantly improved. However, when there are too many spunbond fibers in the core layer, the spunbond fibers are easy to form an airtight film after melting, which is not conducive to the air permeability of the nonwoven composite sheet. At the same time, it can be found that the core layer weight ratio of Examples 1 and 6 actually exceeds the core layer ratio range of this application, resulting in no obvious improvement in its overall performance.

[0064] In summary, compared with the prior art, the nonwoven composite sheet provided by the present application uses the core layer spunbond fiber as the skeleton, which significantly improves the tensile breaking strength and tearing strength of the nonwoven composite sheet without affecting the performance of the material itself, and at the same time improves the stiffness of the nonwoven composite sheet. In addition, since the core layer spunbond fiber is a low melting point fiber, the morphology of the flash-spun fiber does not change significantly after it is melt-bonded, so the peeling strength of the nonwoven composite sheet is also significantly improved, and it has higher air permeability.

[0065] In addition, those skilled in the art should understand that, although there are many problems in the prior art, each embodiment or technical solution of the present application can be improved in only one or several aspects, without having to solve all the technical problems listed in the prior art or background technology at the same time. Those skilled in the art should understand that the content not mentioned in a claim should not be used as a limitation on the claim.

[0066] Although the terms such as first surface layer, second surface layer, core layer, etc. are used more frequently in this article, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of this application. It is contrary to the spirit of this application to interpret them as any additional restrictions. The terms "first", "second", etc. (if any) in the specification and claims of the embodiments of this application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the above embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the above embodiments can still be modified, or some or all of the technical features can be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a nonwoven composite sheet, characterized in that: Here are the steps: It includes a first surface layer, a core layer and a second surface layer; The first surface layer and the second surface layer are made of flash spun fibers; the core layer is made of spunbond fibers; The weight of the core layer accounts for 10% or more and 30% or less of the total weight; the raw material of the flash-spun fiber is high-density polyethylene, and the melting point of the high-density polyethylene is greater than or equal to 130° C. and less than or equal to 135° C.; the raw material of the spunbond fiber is low-density polyethylene, and the melting point of the low-density polyethylene is greater than or equal to 100° C. and less than or equal to 110° C.; Flash-spun fiber raw materials are flash-spun to form a fiber web, and the fiber web forms a fiber web on a mesh curtain; cold-pressing the fiber web, and agglomerating melted spunbond fibers on the cold-pressed fiber web to obtain a two-layer composite fiber web; cold-pressing the two-layer composite fiber web, and laying the fiber mesh sheet made of the flash-spun fibers on the spunbond fiber surface of the cold-pressed two-layer composite fiber web to obtain a three-layer composite fiber web; The three-layer composite fiber web is preheated and pressed, and then hot-air shaped and hot-calendered to obtain the non-woven composite sheet; The roller surface temperature of the hot calendering roller is greater than or equal to 120°C and less than or equal to 150°C, the roller oil pressure is 1.5-5.0MPa, and the roller surface speed is 20-60m / min; The diameter of the spunbond fiber is greater than or equal to 15 μm and less than or equal to 25 μm, and the diameter of the flash spun fiber is greater than or equal to 0.5 μm and less than or equal to 2 μm.

2. The method for preparing a nonwoven composite sheet according to claim 1, characterized in that: Also includes any one or more of the following properties: The first type, the overall total weight is greater than or equal to 40g / m 2 And less than or equal to 120g / m 2 ; The second type is that the weight of the core layer accounts for greater than or equal to 11% and less than or equal to 20% of the total weight; The third type is that the weight of the first surface layer and the second surface layer accounts for more than or equal to 10% and less than or equal to 80% of the total weight respectively; Fourth, the difference between the weight of the first surface layer and the second surface layer in the total weight is not greater than 15%; The fifth type has a stiffness greater than or equal to 20mN.cm and less than or equal to 45mN.cm; The sixth type has an air permeability greater than or equal to 18 mm / s and less than or equal to 40 mm / s.

3. The preparation method according to claim 1, characterized in that: The hot air setting temperature is higher than the melting point of the spunbond fiber and lower than the melting point of the flash spun fiber.

4. The preparation method according to claim 1, characterized in that: The fiber web preparation process is as follows: high-density polyethylene and a solvent are mixed in a reaction kettle to dissolve and form a uniform solution, the uniform solution is sprayed out through the spinneret holes of a nozzle to form a fiber bundle containing ultrafine fibers, the fiber bundle is refracted and diverged through a rotating filament separator to form the fiber web with a mesh structure, the continuously formed fiber web is stacked on a moving mesh curtain to form the fiber web with a certain grammage and width.

5. The preparation method according to claim 1, characterized in that: The preparation process of the two-layer composite fiber web is as follows: low-density polyethylene is added to a screw extruder, heated and melted by the screw extruder, quantitatively metered by a metering pump, and extruded through a die head to form a spinning stream, and the spinning stream is stretched into the spunbond fiber under the action of wind force, and the spunbond fiber is condensed on the flash spun fiber web transmitted from the previous process to form the two-layer composite fiber web.

6. The preparation method according to claim 1, characterized in that: The preparation process of the three-layer composite fiber web is as follows: high-density polyethylene and a solvent are mixed in a reactor to dissolve and form a uniform solution, the uniform solution is sprayed out through the spinneret holes of the nozzle to form a fiber bundle containing ultrafine fibers, the fiber bundle is refracted and diverged through a rotating filament separator to form the fiber mesh with a mesh structure, the continuously formed fiber mesh is stacked on the two-layer composite fiber web transmitted from the previous process, and a layer of the flash spun fiber is stacked on the surface of the spunbond fiber in the core layer to obtain the three-layer composite fiber web.

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