Multilayer composite fiber sheet as well as preparation method and application thereof

Abstract

The invention provides a multi-layer composite fiber sheet and a preparation method and application thereof, and belongs to the technical field of high polymer materials.The multi-layer composite fiber sheet is characterized in that at least one ethylene-propylene copolymer fiber layer (B) is added between at least two high-density polyethylene fiber layers (A) to form an A-B-A sandwich structure; a plurality of bonding points exist between the ethylene-propylene copolymer and the high-density polyethylene, bonding and curing are achieved, the self heat melting phenomenon cannot occur, and the mechanical property, the heat resistance, the air permeability, the opacity and the layering strength of the multi-layer composite fiber sheet are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and in particular to a multi-layer composite fiber sheet and a preparation method thereof. Background Art

[0002] High-pressure flash spinning is a type of solution spinning. Its fundamental principle is the high-speed phase separation of a polymer solution. The fiber-forming polymer forms a spinning fluid within a high-temperature, high-pressure reaction vessel and is released under atmospheric pressure. The spinning fluid is ejected from the spinneret at high speed under high pressure, experiencing high-speed stretching during this high-speed motion. Due to the sudden drop in pressure, the spinning fluid undergoes high-speed phase separation, causing the low-boiling-point solvent to rapidly expand. This solidifies into continuous nano- and micro-fibers with a cross-linked network structure.

[0003] High-pressure flash spinning primarily uses polyethylene as the raw material. Polyethylene fibers undergo post-processing processes such as compaction and thermal bonding to create polyethylene fiber films for applications in medical packaging, protective clothing, and other fields. However, polyethylene resin is susceptible to thermal overheating, which can lead to a decrease in product performance. This can significantly reduce the product's opacity, air permeability, and layer strength. Furthermore, if the operating temperature exceeds the melting point of polyethylene during use, the product can deform or melt.

[0004] The existing technology uses high-temperature resistant polypropylene to replace polyethylene for flash spinning. Although it can improve the heat resistance of the product, due to the high melting point of polypropylene, the strength and softness of the products prepared from polyethylene fiber film are poor, making it difficult to apply to the field of medical packaging protection. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a multi-layer composite fiber sheet and a preparation method and application thereof.

[0006] To achieve the above objectives, the present invention adopts the following technical solutions: In a first aspect, a multilayer composite fiber sheet is provided, comprising: (A) at least two top fiber layers comprising high-density polyethylene; (B) at least one core fiber layer comprising ethylene-propylene copolymer; the core fiber layer is disposed between the at least two top fiber layers;

[0007] The difference between the melting peak temperature of the ethylene-propylene copolymer and the melting peak temperature of the high-density polyethylene is 10-24°C.

[0008] In some embodiments, the molecular weight distribution coefficient of the ethylene-propylene copolymer is 2.0-2.9.

[0009] In some embodiments, the ethylene-propylene copolymer has an ethylene-derived unit content of 5-11 wt%.

[0010] In some embodiments, the melt flow rate of the ethylene-propylene copolymer at 230° C. and 2.16 kg is 500-2000 g / 10 min, preferably 1000-1500 g / 10 min.

[0011] In some embodiments, the ethylene-propylene copolymer has a melting peak temperature of ≥ 145°C.

[0012] In some embodiments, the density of the high-density polyethylene is 0.940-0.970 g / cm 3 , preferably 0.942-0.958 g / cm 3 .

[0013] In some embodiments, the high-density polyethylene has a peak melting temperature of 125-140°C, preferably 130-138°C.

[0014] In some embodiments, the top fiber layer is made by flash blow spinning; and the core fiber layer is made by melt blow spinning.

[0015] In a second aspect, a method for preparing the multilayer composite fiber sheet is provided, comprising the following steps:

[0016] A spinning solution of high-density polyethylene is prepared, and the spinning solution is spun to obtain the top fiber layer; an ethylene-propylene copolymer is melt-blown to obtain a core fiber layer; and the top fiber layer and the core fiber layer are composited to obtain a multi-layer composite fiber sheet.

[0017] In some embodiments, the method for preparing the multi-layer composite fiber sheet comprises the following steps:

[0018] Adding high-density polyethylene into a first autoclave and a second autoclave containing a solvent, heating and dissolving, to obtain a first mixed liquid and a second mixed liquid respectively;

[0019] Opening the high-pressure control valve between the autoclave and the low-pressure autoclave to allow the first mixed solution to flow into the first low-pressure autoclave and the second mixed solution to flow into the second low-pressure autoclave, heating and dissolving them to obtain a first spinning solution and a second spinning solution, respectively;

[0020] Open the low-pressure control valve to reduce the pressure, so that the first spinning solution and the second spinning solution are spun separately and received by the receiving device to form the first top fiber layer and the second top fiber layer;

[0021] The ethylene-propylene copolymer is added into a screw extruder and melted, and the obtained ethylene-propylene copolymer melt is spun through a melt-blowing die head, and then treated by an electrostatic device, and then a receiving device is used to receive the core fiber layer;

[0022] The first top fiber layer, the second top fiber layer and the core fiber layer are cold pressed and hot rolled to obtain a multi-layer composite fiber sheet.

[0023] In some embodiments, the heating and dissolving conditions of the first autoclave and the second autoclave are independently: temperature of 150-230° C., pressure of 5-25 MPa, and stirring time of 20-30 min.

[0024] In some embodiments, the heating and dissolving conditions of the first and second low-pressure autoclaves are independently: pressure of 5-20 MPa, temperature of 150-230° C., and residence time of 15-30 min.

[0025] In some embodiments, the solvent is at least one of 1,2-dichloroethane, dichloromethane, n-pentane, and cyclohexane.

[0026] In some embodiments, the mass percentage concentration of high-density polyethylene in the first mixed solution and the second mixed solution is independently 5-25%.

[0027] In some embodiments, the temperature of the meltblowing die head is 180-280° C., and the diameter of the spinneret hole is 0.15-0.35 mm.

[0028] In some embodiments, the electrostatic device is an electrostatic discharger; and / or the voltage of the electrostatic device is -30 to -80 kV.

[0029] In a third aspect, a product is provided, wherein the product contains the multi-layer composite fiber sheet or the multi-layer composite fiber sheet prepared by the preparation method.

[0030] In a fourth aspect, a medical device protective packaging product is provided, wherein the medical device protective packaging product contains the multi-layer composite fiber sheet or the multi-layer composite fiber sheet prepared by the preparation method.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention adds at least one layer of ethylene-propylene copolymer fiber layer (B) between at least two layers of high-density polyethylene fiber layers (A) to form an "ABA" sandwich structure. There are multiple bonding points between the ethylene-propylene copolymer and the high-density polyethylene, which are bonded and solidified without self-heat melting, thereby improving the mechanical properties, heat resistance, air permeability, opacity and delamination strength of the multi-layer composite fiber sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1This is a schematic structural diagram of the flash jet spinning equipment for a layer of fiber of the present invention, wherein: 1 is an autoclave; 2 is a low-pressure autoclave; 3 is a spinneret; 4 is a filament separation baffle; 5 is a high-pressure control valve; 6 is a low-pressure control valve; 7 is a heating jacket for the autoclave; 8 is a heating jacket for the low-pressure autoclave; 9 is a stirrer; and 10 is a control device;

[0033] Figure 2 Schematic diagram of the spinning device of the multi-layer composite fiber sheet of the present invention, wherein 11 is the first spinning solution, 12 is the ethylene-propylene copolymer melt, 13 is the second spinning solution, 14 is the compacting roller, 15 is the receiving device, and 16 is the spinning box;

[0034] Figure 3 Schematic diagram of the structure of a melt-blown ethylene-propylene copolymer fiber laying device, wherein 15 is a receiving device; 17 is a melt-blown die head; 18 is a melt-blown ethylene-propylene copolymer fiber; 19 is an electrostatic discharger; and 20 is a metal grounding roller.

[0035] Figure 4 It is a schematic diagram of the spinning device of the multi-layer composite fiber sheet in Comparative Example 3, wherein 21 is the first spinning solution, 22 is the second spinning solution, 23 is the third spinning solution, 24 is the compacting roller, 25 is the receiving device, and 26 is the spinning box. DETAILED DESCRIPTION

[0036] To facilitate understanding of the present invention, the present invention will be described more fully below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0037] As used herein:

[0038] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0039] The conjunction "consisting of" excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim, rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0040] When amount, concentration or other value or parameter are represented with range, preferred range or the range that a series of upper preferred value and lower preferred value limit are expressed, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, and no matter whether this scope is disclosed separately.For example, when disclosing scope " 1-5 ", described scope should be interpreted as including scope " 1-4 ", " 1-3 ", " 1-2 ", " 1-2 and 4-5 ", " 1-3 and 5 " etc.When numerical range is described in this article, unless otherwise stated, otherwise this scope is intended to include its end value and all integers and fractions within this range.

[0041] In these examples, parts and percentages are by mass unless otherwise indicated.

[0042] "Parts by mass" refers to the basic unit of measurement used to express the mass ratio of multiple components. One part can represent any unit of mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, this means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, we could say that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number representing a multiplication factor). It's important to note that, unlike parts by mass, the sum of the mass of all components is not limited to 100 parts.

[0043] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0044] A multi-layer composite fiber sheet comprising (A) at least two top fiber layers comprising high-density polyethylene; (B) at least one core fiber layer comprising ethylene-propylene copolymer, the core fiber layer being disposed between the at least two top fiber layers;

[0045] The difference between the melting peak temperature of the ethylene-propylene copolymer and the melting peak temperature of the high-density polyethylene is 10-24°C.

[0046] The present invention adds at least one layer of melt-blown ethylene-propylene copolymer fiber layer (B) between at least two layers of flash-blown high-density polyethylene fiber layers (A) to form an "ABA" sandwich structure. There are multiple bonding points between the ethylene-propylene copolymer and the high-density polyethylene, which are bonded and solidified without self-melting, thereby improving the mechanical properties, heat resistance, air permeability, opacity and delamination strength of the multi-layer composite fiber sheet.

[0047] The applicant found that the difference between the peak melting temperature of the ethylene-propylene copolymer and the peak melting temperature of the high-density polyethylene is too low, and the top layer and core layer fibers will be excessively bonded during the thermal bonding process, resulting in too low opacity and seriously insufficient heat resistance.

[0048] For example, in different embodiments, the difference between the peak melting temperature of the ethylene-propylene copolymer and the peak melting temperature of the high-density polyethylene is 10-24°C, specifically but not limited to 10°C, 13°C, 15°C, 17°C, 20°C, 22°C, and 24°C.

[0049] In the present invention, the peak melting temperature of high-density polyethylene, and the initial melting temperature and peak melting temperature of ethylene-propylene copolymer are obtained by differential scanning calorimetry using the method described in GB / T 19466.3-2004; the initial melting temperature refers to the extrapolated onset temperature in GB / T 19466.3-2004.

[0050] When the difference between the melting peak temperature of the ethylene-propylene copolymer and the melting peak temperature of the high-density polyethylene is too high, an effective thermal bonding effect cannot be formed during the thermal bonding process, resulting in the composite sheet being unable to become a whole and the delamination strength being significantly insufficient; when the difference between the melting peak temperature of the ethylene-propylene copolymer and the melting peak temperature of the high-density polyethylene is too low, excessive melting is likely to occur during the thermal bonding process, resulting in an inability to effectively improve opacity and heat resistance;

[0051] The applicant found that when the melt flow rate of the ethylene-propylene copolymer is 500-2000 g / 10 min, the fiber can be properly stretched during the spinning process, avoiding abnormal phenomena such as discontinuous flying of the spun fibers, while meeting the mechanical and waterproof performance requirements of the multi-layer composite fiber sheet; preferably, the melt flow rate of the ethylene-propylene copolymer is 1000-1500 g / 10 min, and the multi-layer composite fiber sheet has better waterproofness, opacity and air permeability.

[0052] For example, in different embodiments, the melt flow rate of the ethylene-propylene copolymer is measured according to the GB / T 3682.1 method, and the test conditions are 230° C. and 2.16 kg. The melt flow rate of the ethylene-propylene copolymer can be, but is not limited to, 500 g / 10 min, 700 g / 10 min, 900 g / 10 min, 1100 g / 10 min, 1300 g / 10 min, 1500 g / 10 min, 1700 g / 10 min, 1900 g / 10 min, and 2000 g / 10 min; preferably, it is 1000-1500 g / 10 min.

[0053] For example, in different embodiments, the ethylene-propylene copolymer may have an ethylene-derived unit content of, but is not limited to, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or 11 wt%.

[0054] In the present invention, the ethylene-derived unit content of the ethylene-propylene copolymer is measured by referring to the method specified in SH / T 800.

[0055] In some embodiments, the molecular weight distribution coefficient of the ethylene-propylene copolymer is 2-2.9, for example, but not limited to, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, and 2.9.

[0056] In the present invention, the molecular weight distribution coefficient of the ethylene-propylene copolymer is tested using a high-temperature GPC instrument, the solvent is trichlorobenzene, the sample treatment temperature is 160° C., and the treatment time is 120 min.

[0057] The applicant has found that when the molecular weight distribution coefficient of the ethylene-propylene copolymer is 2-2.9, the ethylene-propylene copolymer and the polyethylene fiber can be better bonded during the thermal bonding process, further improving the delamination strength and effectively avoiding the problem of fiber discontinuity, while also ensuring the opacity of the material.

[0058] In some embodiments, the ethylene-propylene copolymer has a melting peak temperature of ≥ 145°C.

[0059] For example, in different embodiments, the peak melting temperature of the ethylene-propylene copolymer is 145-155°C, for example, but not limited to, 145°C, 148°C, 150°C, 152°C, or 155°C.

[0060] In some embodiments, the ethylene-propylene copolymer has an initial melting temperature of ≤145°C.

[0061] For example, in different embodiments, the initial melting temperature of the ethylene-propylene copolymer is 135-145°C, for example, but not limited to, 135°C, 137°C, 140°C, 143°C, or 145°C.

[0062] The ethylene-propylene copolymer of the present invention can be a commercially available product, or can be prepared in-house, for example, by the Spheripol process.

[0063] The propylene copolymer described in the present invention can be prepared by the following method:

[0064] S1: injecting propylene and a catalyst into a polymerization reactor to carry out a prepolymerization reaction to obtain a prepolymer;

[0065] S2: After the prepolymerization reaction, the prepolymer is polymerized with propylene monomer, hydrogen and ethylene in a loop reactor to obtain a random copolymer;

[0066] S3: The random copolymer produced in the loop reactor is vaporized and then enters the gas phase reactor; in the gas phase reactor, it undergoes copolymerization reaction with ethylene and propylene to obtain ethylene-propylene copolymer.

[0067] The method can be carried out using any catalyst suitable for preparing ethylene-propylene copolymers. Preferably, the above method is carried out using a Ziegler-Natta catalyst, especially a high-yield Ziegler-Natta catalyst (so-called fourth and fifth generation types, which are different from the so-called second generation Ziegler-Natta catalysts of low yield). Ziegler-Natta catalysts suitable for the present invention comprise a catalyst component, a co-catalyst component and at least one electron donor (internal and / or external electron donor, preferably at least one external donor). Preferably, the catalyst component is a Ti-Mg based catalyst component, and a typical co-catalyst is an Al-alkyl based compound. Preferred external donors are known silane based donors, such as dicyclopentyldimethoxysilane or cyclohexylmethyldimethoxysilane.

[0068] Specifically, the added amount of the catalyst is 0.001-0.008% of the mass of propylene.

[0069] Specifically, in step S1, the prepolymerization reaction temperature is 15-25° C. and the time is 10-20 minutes.

[0070] Specifically, in step S2, the polymerization reaction temperature is 40-110°C, preferably 60-100°C, and especially 80-90°C; the pressure is 20-80 bar, preferably 30-60 bar; and the residence time is 0.5-5h, preferably 0.5-2h.

[0071] Specifically, in step S2, the number of loop reactors is two.

[0072] Specifically, in step S3, the polymerization reaction temperature is 50-130° C., more preferably 80-100° C.; the pressure is 5-50 bar, preferably 15-35 bar; and the residence time is 5-15 min.

[0073] The properties of the ethylene-propylene copolymer prepared by the above method can be adjusted and controlled by process conditions known to those skilled in the art, such as at least one of the following parameters: temperature, hydrogen flow rate, ethylene feed, propylene feed, catalyst dosage, residence time, and pressure.

[0074] In some embodiments, the density of the high-density polyethylene is 0.940-0.970 g / cm 3, for example, but not limited to 0.940 g / cm 3 , 0.944g / cm 3 , 0.946g / cm 3 , 0.948g / cm 3 、0.950g / cm 3 、0.952g / cm 3 , 0.954g / cm 3 , 0.956g / cm 3 , 0.958g / cm 3 、0.960g / cm 3 , 0.965g / cm 3 , 0.970g / cm 3 ; preferably 0.942-0.958g / cm 3 .

[0075] In the present invention, the density of high-density polyethylene is measured by referring to the method specified in GB / T 1033.1-2008.

[0076] For example, in different embodiments, the melt flow rate of high-density polyethylene is measured according to the method shown in GB / T3682.1-2018-standard, the test conditions are 190°C, 2.16 kg, and the melt flow rate of high-density polyethylene is 0.1-15 g / 10 min, for example, it can be but not limited to 0.1 g / 10 min, 0.5 g / 10 min, 1 g / 10 min, 3 g / 10 min, 4 g / 10 min, 6 g / 10 min, 8 g / 10 min, 9 g / 10 min, 10 g / 10 min, 13 g / 10 min, 15 g / 10 min; preferably 0.3-2 g / 10 min.

[0077] For example, in different embodiments, the peak melting temperature of the high-density polyethylene is 125-140°C, for example, but not limited to 125°C, 130°C, 135°C, 140°C, preferably 130-138°C.

[0078] For example, in a different embodiment, the top fiber layer is made by flash spinning; and the core fiber layer is made by melt blowing.

[0079] Both component (A) and component (B) may further include additives commonly used in the polyolefin field, such as antioxidants, light stabilizers, nucleating agents, lubricants, antistatic agents, colorants, fillers, and the like.

[0080] Specifically, the mass of the additive is 0.001-30% of the total mass of the multi-layer composite fiber sheet.

[0081] like Figure 1 As shown, the flash jet spinning equipment for producing a high-density polyethylene fiber layer of the present invention includes an autoclave 1, a heating jacket 7, a low-pressure autoclave 2, and a heating jacket 8. The autoclave 1 and the low-pressure autoclave 2 are connected and are equipped with a high-pressure control valve 5; an agitator 9 is installed in the autoclave 1; the output pipe of the low-pressure autoclave 2 is connected to the spinneret 3 through the low-pressure control valve 6, and a filament separation baffle 4 is installed at the outlet of the spinneret 3; the heating jackets (including the autoclave heating jacket 7 and the low-pressure autoclave heating jacket 8), the control valves (including the high-pressure control valve 5 and the low-pressure control valve 6), and the agitator 9 are respectively connected to a control device 10;

[0082] The outer wall of the autoclave 1 described in the present invention is heated by an autoclave heating jacket 7 to meet the temperature requirements of the spinning process. An agitator 9 is installed within the autoclave 1 to fully stir the polymer solution. The agitator 9 is connected to a control device 10 and can be adjusted in speed as needed. The autoclave heating jacket 7 is also connected to the control device 10 and can also be adjusted in temperature according to process requirements. These speed and temperature adjustments are conventional. The outer wall of the low-pressure autoclave 2 described in the present invention is heated by a low-pressure autoclave heating jacket 8. The low-pressure autoclave 2 and the low-pressure autoclave heating jacket 8 are also connected to the control device 10 and can also be adjusted in temperature according to process requirements. The autoclave 1 and the low-pressure autoclave 2 are connected and equipped with a high-pressure control valve 5. When the autoclave control valve 5 is opened, the solution in the autoclave 1 can flow from the autoclave 1 into the low-pressure autoclave 2, and the flow rate and flow rate can be controlled by the high-pressure control valve 5. The output pipe of the low-pressure autoclave 2 is connected to a low-pressure control valve 6, which is connected to the spinneret 3. The filament separation baffle 4 is screwed to the spinneret 3. When the low-pressure control valve 6 is opened, the solution can be sprayed out from the low-pressure kettle 2 through the spinneret 3 and the filament baffle 4, and the flow rate and flow velocity can be controlled by the low-pressure control valve 6; the present invention uses at least two sets of parallel flash spinning equipment to prepare the high-density polyethylene fiber layer of the present invention.

[0083] Specifically, the flash jet spinning equipment for producing the high-density polyethylene fiber layer of the present invention adopts the equipment for flash jet spinning of ultrafine fibers used in CN 101173374A.

[0084] It should be noted that the products of this application are not limited to the production of the above-mentioned production equipment. Technical personnel in this field can also use other types of flash spraying production equipment to produce products according to actual needs, as long as they can produce products with the same technical characteristics and technical effects.

[0085] In a second aspect, a method for preparing a multilayer composite fiber sheet is provided, comprising the following steps:

[0086] A spinning solution of high-density polyethylene is prepared, and the spinning solution is spun to obtain the top fiber layer; an ethylene-propylene copolymer is melt-blown to obtain a core fiber layer; and the top fiber layer and the core fiber layer are composited to obtain a multi-layer composite fiber sheet.

[0087] In some embodiments, a method for preparing a multilayer composite fiber sheet comprises the following steps:

[0088] Adding high-density polyethylene into a first autoclave and a second autoclave containing a solvent, heating and dissolving, to obtain a first mixed liquid and a second mixed liquid respectively;

[0089] Opening the high-pressure control valve between the autoclave and the low-pressure autoclave to allow the first mixed solution to flow into the first low-pressure autoclave and the second mixed solution to flow into the second low-pressure autoclave, heating and dissolving them to obtain a first spinning solution and a second spinning solution, respectively;

[0090] like Figure 2 As shown, the low-pressure control valve is opened to reduce the pressure, so that the first spinning solution 11 and the second spinning solution 13 are spun respectively and received by the receiving device 15 to form the first top fiber layer and the second top fiber layer;

[0091] The ethylene-propylene copolymer is added to a screw extruder and melted. The obtained ethylene-propylene copolymer melt 12 is spun through the spinneret of a melt-blowing die head, and then treated by an electrostatic device and received by a receiving device 15 to form a core fiber layer.

[0092] The first top fiber layer, the second top fiber layer and the core fiber layer are cold pressed and hot rolled by a compacting roller 14 to obtain a multi-layer composite fiber sheet.

[0093] In some embodiments, the HDPE fiber layer has a grammage of 5-50 g / m 2 , for example, but not limited to 5g / m 2 , 10g / m 2 , 20g / m 2 , 30g / m 2 , 40g / m 2 , 50g / m 2 .

[0094] In some embodiments, the ethylene-propylene copolymer fiber layer has a grammage of 5-50 g / m 2 , for example, but not limited to 10g / m 2 , 20g / m 2 , 30g / m 2 , 40g / m 2 , 50g / m 2 .

[0095] In some embodiments, the heating and dissolving conditions in the first autoclave and the second autoclave are independently: temperature of 150-230° C., pressure of 5-25 MPa, and stirring time of 20-30 min.

[0096] In some embodiments, the boiling point of the solvent is ≤100° C.; preferably, the solvent is at least one of 1,2-dichloroethane, dichloromethane, n-pentane, and cyclohexane.

[0097] In some embodiments, the mass percentage concentration of high-density polyethylene in the first mixed solution and the second mixed solution is independently 5-25%; for example, it can be but not limited to 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%.

[0098] In some embodiments, as Figure 3 As shown, the ethylene-propylene copolymer melt is ejected through the spinneret holes of the meltblown die 17, and side-blown hot air is introduced on both sides of the spinneret holes to stretch the fibers to obtain meltblown ethylene-propylene copolymer fibers 18. The meltblown ethylene-propylene copolymer fibers 18 are charged by an electrostatic discharger 19, and then a receiving device 15 is used to receive the meltblown ethylene-propylene copolymer fibers to form a meltblown ethylene-propylene copolymer fiber layer.

[0099] In this embodiment, the electrostatic device is used to process the melt-blown ethylene-propylene copolymer fibers, so that the melt-blown ethylene-propylene copolymer fibers can be fully separated and better received by the receiving device, thereby achieving a stable web laying process.

[0100] In some embodiments, the temperature of the meltblowing die head is 180-280°C, for example, but not limited to 180°C, 200°C, 220°C, 240°C, 260°C, 280°C, preferably 200-250°C.

[0101] The diameter of the spinneret hole is 0.15-0.35 mm, for example, it can be but not limited to 0.15 mm, 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm; preferably, it is 0.2-0.3 mm.

[0102] The voltage of the electrostatic device is -30 to -80 kV, for example, but not limited to -30 kV, -40 kV, -50 kV, -60 kV, -70 kV, -80 kV; preferably, -45 to -60 kV.

[0103] In some embodiments, the hot rolling temperature is 130-150°C, for example, but not limited to, 130°C, 135°C, 140°C, 145°C, or 150°C.

[0104] Specifically, the receiving device is a conductive mesh curtain, which has an opposite charge to the flash-blown high-density polyethylene fiber and the melt-blown ethylene-propylene copolymer fiber, and can enhance the adsorption capacity of the conductive mesh curtain to the flash-blown high-density polyethylene fiber and the melt-blown ethylene-propylene copolymer.

[0105] In one embodiment, a negative pressure suction device is installed on the other side of the conductive mesh curtain without the fiber layer to further enhance the adsorption capacity of the conductive mesh curtain for the flash-blown high-density polyethylene fibers and the melt-blown ethylene-propylene copolymer.

[0106] In a third aspect, a product is provided, wherein the product comprises the multi-layer composite fiber sheet or the multi-layer composite fiber sheet prepared by the preparation method;

[0107] In a fourth aspect, a medical device protective packaging product is provided, which contains the multi-layer composite fiber sheet or the multi-layer composite fiber sheet prepared by the preparation method; the medical device packaging product includes protective clothing, packaging bags, side-sealed bags, etc.

[0108] The raw materials used in the examples and comparative examples are described below, but are not limited to these materials:

[0109] High-density polyethylene A: melting peak temperature is 134°C, density is 0.955 g / cm 3 , melt flow rate is 0.3g / 10min (test conditions are 190℃, 2.16kg), from Sinopec Maoming Branch, model HHM5502LW;

[0110] High-density polyethylene B: melting peak temperature is 136°C, density is 0.945 g / cm 3 , melt flow rate is 1g / 10min (test conditions are 190℃, 2.16kg), from LyondellBasell, model GF7750M2;

[0111] Ethylene-propylene copolymer AK is homemade, and its preparation method is as follows:

[0112] S1: injecting propylene and a commercial fifth-generation Ziegler-Natta catalyst into polymerization reactor A to carry out a prepolymerization reaction to obtain a prepolymer; wherein the prepolymerization reaction temperature is 15-25° C. and the reaction time is 10-20 minutes;

[0113] S2: After the prepolymerization reaction, the prepolymer is polymerized with propylene monomer, hydrogen and ethylene in loop reactor B / C to obtain a random copolymer; wherein the polymerization temperature is 40-110°C, the pressure is 20-80 bar, and the residence time is 0.5-5 hours;

[0114] S3: The random copolymer produced in the loop reactor is vaporized and then fed into a gas phase reactor. In the gas phase reactor, the random copolymer undergoes block copolymerization with ethylene and propylene to produce an ethylene-propylene copolymer. The copolymerization reaction temperature is 50-130°C, the pressure is 5-50 bar, and the residence time is 5-8 minutes.

[0115] Ethylene-propylene copolymer AK is obtained by adjusting and controlling at least one parameter among temperature, hydrogen flow rate, ethylene feed, propylene feed, catalyst dosage, residence time and pressure.

[0116] Ethylene-propylene copolymer A: ethylene-derived unit content of 8 wt%, molecular weight distribution of 2.4, melt flow rate of 1300 g / 10 min, and peak melting temperature of 149°C;

[0117] Ethylene-propylene copolymer B: ethylene-derived unit content of 5 wt%, molecular weight distribution of 2.3, melt flow rate of 1300 g / 10 min, and peak melting temperature of 153°C;

[0118] Ethylene-propylene copolymer C: ethylene-derived unit content of 11 wt%, molecular weight distribution of 2.7, melt flow rate of 1300 g / 10 min, and peak melting temperature of 146°C;

[0119] Ethylene-propylene copolymer D: ethylene-derived unit content of 5 wt%, molecular weight distribution of 2.2, melt flow rate of 1000 g / 10 min, and peak melting temperature of 153°C;

[0120] Ethylene-propylene copolymer E: ethylene-derived unit content of 5 wt%, molecular weight distribution of 2.1, melt flow rate of 1500 g / 10 min, and peak melting temperature of 152°C;

[0121] Ethylene-propylene copolymer F: ethylene-derived unit content of 5 wt%, molecular weight distribution of 2.6, melt flow rate of 2000 g / 10 min, and peak melting temperature of 153°C;

[0122] Ethylene-propylene copolymer G: ethylene-derived unit content of 5 wt%, molecular weight distribution of 2.7, melt flow rate of 500 g / 10 min, and peak melting temperature of 158°C;

[0123] Ethylene-propylene copolymer H: ethylene-derived unit content of 3 wt%, molecular weight distribution of 2.6, melt flow rate of 1300 g / 10 min, and peak melting temperature of 160°C;

[0124] Ethylene-propylene copolymer I: ethylene-derived unit content is 15 wt%, molecular weight distribution is 2.9, melt flow rate is 1300 g / 10 min, and melting peak temperature is 144°C.

[0125] Example 1

[0126] This embodiment provides a multilayer composite fiber sheet, comprising (A) two top fiber layers, each comprising high-density polyethylene A; (B) a core fiber layer, each comprising ethylene-propylene copolymer A; the core fiber layer is disposed between the two top fiber layers; wherein the top fiber layer has a grammage of 25 g / m 2 The core fiber layer has a gram weight of 25g / m 2 .

[0127] The method for preparing the multilayer composite fiber sheet of this embodiment includes the following steps:

[0128] High-density polyethylene A was added to a first autoclave and a second autoclave containing 1,2-dichloroethane, and heated to dissolve, respectively, to obtain a first mixed solution and a second mixed solution; the heating and dissolving conditions in the first autoclave and the second autoclave were both: a temperature of 190° C., a pressure of 15 MPa, and a stirring time of 25 minutes; and the mass percentage concentration of high-density polyethylene A in the first mixed solution and the second mixed solution was both 15 wt %.

[0129] The high-pressure control valve between the autoclave and the low-pressure autoclave was opened to allow the first mixed solution to flow into the first low-pressure autoclave and the second mixed solution to flow into the second low-pressure autoclave, and the mixture was heated and dissolved to obtain a first spinning solution and a second spinning solution, respectively. The heating and dissolving conditions of the first and second low-pressure autoclaves were both: a pressure of 8 MPa, a temperature of 190° C., and a residence time of 20 min.

[0130] like Figure 2 As shown, the low-pressure control valve is opened to reduce the pressure, so that the first spinning solution 11 and the second spinning solution 13 are spun respectively and received by the receiving device 15 to form the first top fiber layer and the second top fiber layer;

[0131] Ethylene-propylene copolymer is added to a single screw extruder to melt, such as Figure 2 and Figure 3 As shown, the obtained ethylene-propylene copolymer melt 12 is ejected through the spinneret of the meltblowing die head 17, and side-blown hot air is introduced on both sides of the spinneret to stretch the fiber to obtain a meltblown ethylene-propylene copolymer fiber 18. The meltblown ethylene-propylene copolymer fiber 18 is charged by an electrostatic discharger 19, the voltage of the electrostatic discharger is 50 kV, and then the meltblown ethylene-propylene copolymer fiber is received by a receiving device 15 to form a core fiber layer; the temperature of the meltblowing die head is 240 ° C, and the diameter of the spinneret is 0.25 mm; in this embodiment, the receiving device 15 is a conductive mesh curtain;

[0132] The first top fiber layer, the second top fiber layer and the core fiber layer are cold-pressed by a compacting roller 14 and then hot-rolled at a temperature of 140° C. to obtain a multi-layer composite fiber sheet.

[0133] Example 2

[0134] This embodiment provides a multilayer composite fiber sheet, comprising (A) two top fiber layers, each comprising high-density polyethylene B; (B) a core fiber layer, each comprising ethylene-propylene copolymer A; the core fiber layer is disposed between the two top fiber layers; wherein the top fiber layer has a gram weight of 30 g / m 2 The core fiber layer has a gram weight of 20g / m 2 .

[0135] The method for preparing the multilayer composite fiber sheet of this embodiment includes the following steps:

[0136] High-density polyethylene B was added to a first autoclave and a second autoclave containing 1,2-dichloroethane, and heated to dissolve, respectively, to obtain a first mixed solution and a second mixed solution; the heating and dissolving conditions in the first autoclave were: temperature 150° C., pressure 25 MPa, and stirring time 25 minutes; the heating and dissolving conditions in the second autoclave were: temperature 230° C., pressure 10 MPa, and stirring time 25 minutes; the mass percentage concentration of high-density polyethylene B in the first mixed solution was 10 wt%, and the mass percentage concentration of high-density polyethylene B in the second mixed solution was 20 wt%;

[0137] The high-pressure control valve between the autoclave and the low-pressure autoclave was opened to allow the first mixed solution to flow into the first low-pressure autoclave and the second mixed solution to flow into the second low-pressure autoclave, and the mixture was heated and dissolved to obtain a first spinning solution and a second spinning solution, respectively. The heating and dissolving conditions in the first low-pressure autoclave were: temperature 150° C., pressure 10 MPa, and stirring time 25 min; the heating and dissolving conditions in the second low-pressure autoclave were: temperature 230° C., pressure 5 MPa, and stirring time 25 min.

[0138] like Figure 2 As shown, the low-pressure control valve is opened to reduce the pressure, so that the first spinning solution 11 and the second spinning solution 13 are spun respectively and received by the receiving device 15 to form the first top fiber layer and the second top fiber layer;

[0139] Ethylene-propylene copolymer is added to a single screw extruder to melt, such as Figure 2 and Figure 3As shown, the obtained ethylene-propylene copolymer melt 12 is ejected through the spinneret of the meltblowing die head 17, and side-blown hot air is introduced on both sides of the spinneret to stretch the fiber to obtain a meltblown ethylene-propylene copolymer fiber 18. The meltblown ethylene-propylene copolymer fiber 18 is charged by an electrostatic discharger 19, the voltage of the electrostatic discharger is 60 kV, and then the meltblown ethylene-propylene copolymer fiber is received by a receiving device 15 to form a core fiber layer; the temperature of the meltblowing die head is 260 ° C, and the diameter of the spinneret is 0.3 mm; in this embodiment, the receiving device 15 is a conductive mesh curtain;

[0140] The first top fiber layer, the second top fiber layer and the core fiber layer are cold-pressed by a compacting roller 14 and then hot-rolled at a temperature of 140° C. to obtain a multi-layer composite fiber sheet.

[0141] Example 3

[0142] This embodiment provides a multilayer composite fiber sheet, comprising (A) two top fiber layers, each comprising high-density polyethylene A; (B) a core fiber layer, each comprising ethylene-propylene copolymer B; the core fiber layer is disposed between the two top fiber layers; wherein the top fiber layer has a gram weight of 25 g / m 2 The core fiber layer has a gram weight of 25g / m 2 .

[0143] The only difference between the method for preparing the multilayer composite fiber sheet of this embodiment and the method for preparing the multilayer composite fiber sheet of Example 1 is that ethylene-propylene copolymer B is used instead of ethylene-propylene copolymer A, and the other steps and parameters remain unchanged.

[0144] Example 4

[0145] This embodiment provides a multilayer composite fiber sheet, comprising (A) two top fiber layers comprising high-density polyethylene A; (B) a core fiber layer comprising ethylene-propylene copolymer C; the core fiber layer is disposed between the two top fiber layers; wherein the top fiber layer has a gram weight of 25 g / m 2 The core fiber layer has a gram weight of 25g / m 2 .

[0146] The only difference between the method for preparing the multilayer composite fiber sheet of this embodiment and the method for preparing the multilayer composite fiber sheet of Example 1 is that ethylene-propylene copolymer C is used instead of ethylene-propylene copolymer A, and the other steps and parameters remain unchanged.

[0147] Example 5

[0148] This embodiment provides a multilayer composite fiber sheet, comprising (A) two top fiber layers, each comprising high-density polyethylene A; (B) a core fiber layer, each comprising ethylene-propylene copolymer D; the core fiber layer is disposed between the two top fiber layers; wherein the top fiber layer has a gram weight of 25 g / m2 The core fiber layer has a gram weight of 25g / m 2 .

[0149] The only difference between the method for preparing the multilayer composite fiber sheet of this embodiment and the method for preparing the multilayer composite fiber sheet of Example 1 is that ethylene-propylene copolymer D is used instead of ethylene-propylene copolymer A, and the other steps and parameters remain unchanged.

[0150] Example 6

[0151] This embodiment provides a multilayer composite fiber sheet, comprising (A) two top fiber layers, which include high-density polyethylene A; (B) a core fiber layer, which includes ethylene-propylene copolymer E; the core fiber layer is arranged between the two top fiber layers; wherein the top fiber layer has a gram weight of 25g / m 2 The core fiber layer has a gram weight of 25g / m 2 .

[0152] The only difference between the preparation method of the multilayer composite fiber sheet of this embodiment and the preparation method of the multilayer composite fiber sheet of Example 1 is that ethylene-propylene copolymer E is used instead of ethylene-propylene copolymer A, and the other steps and parameters remain unchanged.

[0153] Example 7

[0154] This embodiment provides a multilayer composite fiber sheet, comprising (A) two top fiber layers comprising high-density polyethylene A; (B) a core fiber layer comprising ethylene-propylene copolymer F; the core fiber layer is disposed between the two top fiber layers; wherein the top fiber layer has a gram weight of 25 g / m 2 The core fiber layer has a gram weight of 25g / m 2 .

[0155] The only difference between the method for preparing the multilayer composite fiber sheet of this embodiment and the method for preparing the multilayer composite fiber sheet of Example 1 is that ethylene-propylene copolymer F is used instead of ethylene-propylene copolymer A, and the other steps and parameters remain unchanged.

[0156] Example 8

[0157] This embodiment provides a multilayer composite fiber sheet, comprising (A) two top fiber layers comprising high-density polyethylene A; (B) a core fiber layer comprising ethylene-propylene copolymer G; the core fiber layer is disposed between the two top fiber layers; wherein the top fiber layer has a gram weight of 25 g / m 2 The core fiber layer has a gram weight of 25g / m 2 .

[0158] The only difference between the method for preparing the multilayer composite fiber sheet of this embodiment and the method for preparing the multilayer composite fiber sheet of Example 1 is that ethylene-propylene copolymer G is used instead of ethylene-propylene copolymer A, and the other steps and parameters remain unchanged.

[0159] Comparative Example 1

[0160] This comparative example provides a multilayer composite fiber sheet, comprising (A) two top fiber layers comprising high-density polyethylene A; (B) a core fiber layer comprising ethylene-propylene copolymer H; the core fiber layer is disposed between the two top fiber layers; wherein the top fiber layer has a gram weight of 25 g / m 2 The core fiber layer has a gram weight of 25g / m 2 .

[0161] The only difference between the preparation method of the multilayer composite fiber sheet of this comparative example and the preparation method of the multilayer composite fiber sheet of Example 1 is that ethylene-propylene copolymer H is used instead of ethylene-propylene copolymer A, and the other steps and parameters remain unchanged.

[0162] Comparative Example 2

[0163] This comparative example provides a multilayer composite fiber sheet, comprising (A) two top fiber layers comprising high-density polyethylene A; (B) a core fiber layer comprising ethylene-propylene copolymer I; the core fiber layer is disposed between the two top fiber layers; wherein the top fiber layer has a gram weight of 25 g / m 2 The core fiber layer has a gram weight of 25g / m 2 .

[0164] The only difference between the preparation method of the multilayer composite fiber sheet of this comparative example and the preparation method of the multilayer composite fiber sheet of Example 1 is that ethylene-propylene copolymer I is used instead of ethylene-propylene copolymer A, and the other steps and parameters remain unchanged.

[0165] Comparative Example 3

[0166] This comparative example provides a multi-layer composite fiber sheet, including high-density polyethylene A, and the weight of the multi-layer composite fiber sheet is 75g / m 2 .

[0167] The preparation method of the multi-layer composite fiber sheet of this comparative example comprises the following steps:

[0168] High-density polyethylene A was added to a first autoclave, a second autoclave, and a third autoclave containing 1,2-dichloroethane, and heated to dissolve, thereby obtaining a first mixed solution, a second mixed solution, and a third mixed solution, respectively. The heating and dissolving conditions in the first autoclave, the second autoclave, and the third autoclave were all: a temperature of 190° C., a pressure of 15 MPa, and a stirring time of 25 minutes. The mass percentage concentration of high-density polyethylene A in the first mixed solution, the second mixed solution, and the third mixed solution was all 15 wt %.

[0169] The high-pressure control valve between the autoclave and the low-pressure autoclave was opened to allow the first mixed solution to flow into the first low-pressure autoclave, the second mixed solution to flow into the second low-pressure autoclave, and the third mixed solution to flow into the third low-pressure autoclave, and the mixture was heated and dissolved to obtain a first spinning solution, a second spinning solution, and a third spinning solution, respectively. The heating and dissolving conditions of the first, second, and third low-pressure autoclaves were all: a pressure of 8 MPa, a temperature of 190° C., and a residence time of 20 min.

[0170] like Figure 4 As shown, the low-pressure control valve is opened to reduce the pressure, so that the first spinning solution 21, the second spinning solution 22 and the third spinning solution 23 are spun respectively and received into fiber layers by the receiving device 25. In this comparative example, the receiving device 25 is a conductive mesh curtain. The obtained fiber layer is cold-pressed by the compacting roller 24, and then hot-rolled at a temperature of 140°C to obtain a multi-layer composite fiber sheet.

[0171] Performance Testing

[0172] The multilayer composite fiber sheets obtained in the examples and comparative examples were subjected to performance tests, and the test methods were as follows:

[0173] (1) Delamination strength: Referring to the method of ASTM D2724-87, a 2.5 cm * 20 cm strip sample was taken. A notch was manually cut at one end of the strip sample with scissors. The strip sample was then slowly separated manually until the separation line was flush. The strip sample was then tested using a tensile tester with a gauge length of 10 cm and a tensile speed of 100 mm / min. 3000 readings were taken from the platform portion of the test curve to obtain the average value (unit: N / 2.5 cm). The average value of 5 samples was taken.

[0174] (2) Opacity: refer to ISO 2471 standard method and take the average value of 10 samples;

[0175] (3) Air permeability: refer to the Gurley method in ISO 5636 standard and take the average value of 10 samples. The smaller the value corresponding to the Gurley method air permeability (s), the better the air permeability;

[0176] (4) Tensile strength: Refer to ISO 13934-1 standard method, test the transverse and longitudinal tensile strength, and take the average value of 5 samples;

[0177] (5) Heat resistance: Simulate the high-pressure steam sterilization conditions, slightly adjust the temperature and time, and keep other conditions unchanged. Set the temperature to 130°C and the time to 30 min and 60 min. Place the multi-layer composite fiber sheet under the above two conditions to observe whether the multi-layer composite fiber sheet softens, deforms, or shows other changes.

[0178] The test results are shown in Table 1.

[0179] Table 1

[0180]

[0181] From the experimental data in Table 1, it can be seen that the multi-layer composite fiber sheet of the present invention has a delamination strength ≥3N / 2.5cm, an opacity ≥95%, an air permeability ≤10s, a tensile force ≥400N / 5cm, and no change in appearance after high-pressure steam sterilization at 130°C for 60min.

[0182] By comparing Example 1, Examples 3-4 and Comparative Examples 1-2, it can be seen that when the difference between the peak melting temperature of the ethylene-propylene copolymer and the peak melting temperature of the high-density polyethylene is too high or too low, the delamination strength of the obtained multi-layer composite fiber sheet is ≤2.5N / 2.5cm, the opacity is ≤93%, and the tensile force is ≤390N / 5cm, indicating that when the difference between the peak melting temperature of the ethylene-propylene copolymer and the peak melting temperature of the high-density polyethylene is 10-24°C, the anti-delamination ability, air permeability and tensile force of the multi-layer composite fiber sheet can be improved at the same time.

[0183] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A multi-layer composite fiber sheet, characterized in that: The invention comprises (A) at least two top fiber layers comprising high-density polyethylene; (B) at least one core fiber layer comprising ethylene-propylene copolymer; the core fiber layer being disposed between the at least two top fiber layers; The difference between the melting peak temperature of the ethylene-propylene copolymer and the melting peak temperature of the high-density polyethylene is 10-24°C.

2. The multilayer composite fiber sheet according to claim 1, wherein The molecular weight distribution coefficient of the ethylene-propylene copolymer is 2.0-2.

9.

3. The multi-layer composite fiber sheet according to claim 1, wherein The ethylene-propylene copolymer has an ethylene-derived unit content of 5-11 wt%; And / or, the melt flow rate of the ethylene-propylene copolymer at 230° C. and 2.16 kg is 500-2000 g / 10 min, preferably 1000-1500 g / 10 min.

4. The multi-layer composite fiber sheet according to claim 1, wherein The melting peak temperature of the ethylene-propylene copolymer is ≥145°C.

5. The multi-layer composite fiber sheet according to claim 1, wherein The density of the high-density polyethylene is 0.940-0.970 g / cm 3 , preferably 0.942-0.958 g / cm 3 ; and / or, the high-density polyethylene has a peak melting temperature of 125-140° C., preferably 130-138° C.; And / or, the top fiber layer is made by flash spinning; and the core fiber layer is made by melt blowing.

6. A method for preparing the multilayer composite fiber sheet according to any one of claims 1 to 5, characterized in that: The following steps are involved: preparing a spinning solution of high-density polyethylene, and spinning the spinning solution to obtain the top fiber layer; The ethylene-propylene copolymer is melt-blown and spun to obtain a core fiber layer; the top fiber layer and the core fiber layer are composited to obtain a multi-layer composite fiber sheet.

7. The method for preparing a multi-layer composite fiber sheet according to claim 6, wherein: The method comprises the following steps: adding high-density polyethylene into a first autoclave and a second autoclave containing a solvent, heating and dissolving the polyethylene, and obtaining a first mixed liquid and a second mixed liquid respectively; Opening the high-pressure control valve between the autoclave and the low-pressure autoclave to allow the first mixed solution to flow into the first low-pressure autoclave and the second mixed solution to flow into the second low-pressure autoclave, heating and dissolving them to obtain a first spinning solution and a second spinning solution, respectively; Open the low-pressure control valve to reduce the pressure, so that the first spinning solution and the second spinning solution are spun separately and received by the receiving device to form the first top fiber layer and the second top fiber layer; The ethylene-propylene copolymer is added into a screw extruder and melted, and the obtained ethylene-propylene copolymer melt is spun through a melt-blowing die head, and then treated by an electrostatic device, and then a receiving device is used to receive the core fiber layer; The first top fiber layer, the second top fiber layer and the core fiber layer are cold pressed and hot rolled to obtain a multi-layer composite fiber sheet.

8. The method for preparing a multi-layer composite fiber sheet according to claim 7, wherein: The heating and dissolving conditions of the first autoclave and the second autoclave are independently: temperature of 150-230° C., pressure of 5-25 MPa, and stirring time of 20-30 min; And / or, the heating and dissolving conditions of the first low-pressure kettle and the second low-pressure kettle are independently: pressure of 5-20 MPa, temperature of 150-230° C., and residence time of 15-30 min; and / or, the solvent is at least one of 1,2-dichloroethane, dichloromethane, n-pentane, and cyclohexane; And / or, the mass percentage concentration of high-density polyethylene in the first mixed solution and the second mixed solution is independently 5-25%; and / or, the temperature of the meltblowing die head is 180-280° C., and the spinneret diameter is 0.15-0.35 mm; and / or, the electrostatic device is an electrostatic discharger; And / or, the voltage of the electrostatic device is -30 to -80 kV.

9. A product, characterized in that The product contains the multi-layer composite fiber sheet according to any one of claims 1 to 5 or the multi-layer composite fiber sheet prepared by the preparation method according to any one of claims 6 to 8.

10. A medical device protective packaging product, characterized in that: The medical device protective packaging product contains the multi-layer composite fiber sheet according to any one of claims 1 to 5 or the multi-layer composite fiber sheet prepared by the preparation method according to any one of claims 6 to 8.

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