CN111690195A - Nano microporous membrane, and preparation method and application thereof - Google Patents

Abstract

The invention discloses a nano-microporous film, a method for making a nano-microporous film and an application thereof, including the following mass fractions of each component raw material used in the nano-microporous film: polyolefin: 21.3-30 parts, processing aid: 70-70 parts 78.5 parts, plasticizer; 0.02-0.1 part; antioxidant; 0.03-0.2 part, lubricant; 0.04-0.15 part, wherein the molecular weight of the polyolefin is 50,000-1.5 million. In the present invention, a certain molecular weight of polyolefin and a processing aid are mixed in a certain proportion, so that the compounded material meets specific strength requirements. Under the action of intermolecular force and additives, the polyolefin cast base film is stretched and formed The pore size of the microporous structure is greatly reduced, and the pore size can reach the nanometer level, which can achieve 100% protection effect. At the same time, the thickness of the microporous membrane can also be reduced, making it more comfortable to wear as a mask material.

Description

A kind of nano-microporous film, nano-microporous film manufacturing method and application thereof

technical field

The invention relates to the field of design of medical anti-virus masks, in particular to a nano-microporous film, a method for making the nano-microporous film, and applications thereof.

Background technique

Medical masks are generally multi-layer structures, generally referred to as SMS structures. The material is spunbond non-woven fabric + meltblown non-woven fabric + spunbond non-woven fabric, referred to as SMS structure. At present, the main material of meltblown non-woven fabric is polypropylene, which is an ultra-fine electrostatic fiber cloth that can capture dust. After the droplets containing bacteria and viruses are close to the melt-blown non-woven fabric, they will be electrostatically adsorbed on the surface of the non-woven fabric and cannot be penetrated. That's how the material keeps germs out.

The most important thing in the mask is that the barrier layer is the meltblown layer M (Meltblown), and the fiber diameter of the meltblown layer is about 2 microns. The meltblown layer M has smaller pores than the spunbond layer S, and is rich in electrostatic capture effect, which is the core component of the mask function. However, limited by the current spinning technology, the fiber diameter can only be produced at 2 microns, which cannot be further refined, thereby further reducing the pore size and making the pore size reach the virus diameter range. The pore size of the meltblown layer M is basically between 100nm and 200nm, while the diameter of most viruses at present is 50-100nm, which is just smaller than the pore size of the current medical masks, which lays a certain hidden danger for the invasion of viruses. Therefore, seeking a nano-microporous membrane that is thinner and has a smaller pore size so that it can block viruses 100% has become an important research and development direction for high-end hospital masks.

SUMMARY OF THE INVENTION

In order to solve the technical problem that the pore size of the meltblown layer used in the traditional Chinese medical anti-virus mask is larger than that of the virus and cannot block the virus 100%, the present invention provides a nano-microporous film, a method for making the nano-microporous film and its application. to solve the above problems.

The invention provides a nano-microporous film. The nano-microporous film adopts the following raw materials by mass fraction: polyolefin: 21.3-30 parts, processing aid: 70-78.5 parts, plasticizer; 0.02-0.1 part; antioxidant; 0.03-0.2 part, lubricant; 0.04-0.15 part, wherein, the molecular weight of the polyolefin is 50,000-1.5 million.

Further, the polyolefin is polyethylene or polypropylene.

Further, the processing aid is paraffin oil, and the molecular weight of the paraffin oil is 100-500 g/mol.

Further, the plasticizer is a mixture of one or more of phthalic acid esters, aliphatic dibasic acid esters, and phosphoric acid esters. The phthalates specifically refer to dioctyl phthalate (DOP), the aliphatic dibasic acid esters specifically refer to dioctyl oxalate (DOA), and the phosphate esters specifically refer to trioctyl phosphate (TOP).

Preferably, the antioxidant is a mixture of one or more phenolic antioxidants, and the mixture of multiple antioxidants can achieve a synergistic antioxidant effect.

Preferably, the lubricant is a stearic acid polymer compound.

The present invention also proposes a method for making a nano-microporous membrane, comprising the following steps:

S1: Production of raw materials; mix polyolefin, plasticizer, antioxidant and lubricant according to the above-mentioned mass fraction ratio of each component in the nano-microporous film, stir evenly at a temperature of 20 ° C ~ 50 ° C, and add extrusion out of the equipment, and then the processing aids are added in proportion.

S2: extrusion molding; the mixture in step S1 is melt-extruded from a twin-screw extruder at the bottom, and then cast into sheets through a casting roll to obtain a polyolefin cast base film.

S3: stretching; at 90-110° C., the cast base film is firstly stretched in the longitudinal direction, and then stretched in the transverse direction to obtain a polyolefin microporous film with a microporous structure.

S4: Secondary stretching: First, add volatile reagents to the polyolefin microporous film, extract the high-boiling solvent white oil in the polyolefin microporous film using an extraction process, and then perform transverse stretching again at 100-120 °C stretched, dried and corona treated to obtain a polymer nanoporous membrane.

Preferably, the extrusion equipment in step S1 is a twin-screw extruder.

Preferably, the volatile reagent in step S4 is dichloromethane.

The present invention also proposes the application of the nano-microporous membrane prepared by the above method in medical anti-virus masks.

The beneficial effects of the present invention are:

(1) In the present invention, a certain molecular weight of polyolefin and a processing aid are mixed in a certain proportion, so that the composite material meets specific strength requirements, and under the action of intermolecular force and additives, the polyolefin casting base film is stretched The pore size of the formed microporous structure is greatly reduced, and the pore size can reach the nanometer level, which can achieve 100% protection effect. At the same time, the thickness of the microporous membrane can also be reduced, making it more comfortable to wear as a mask material.

(2) In the present invention, plasticizers and antioxidants are added to the raw materials, and the plasticizers enhance the flexibility of the raw materials, making it easier to process, and the antioxidants can reduce the influence of air on the properties of the raw materials, resulting in better product stability.

(3) The nano-microporous film of the present invention is stretched twice, and after the first stretch to form a polyolefin microporous film, an extraction process is used to extract high-boiling white oil, and the nano-microporous film is polymerized The higher the ratio of olefins, the greater the intermolecular forces.

(4) The method of the present invention can use two main materials of polypropylene and polyethylene to process the nano-microporous film, which breaks through the limitation of only using polypropylene to make melt-blown non-woven fabrics in the prior art, and improves the quality of product raw materials. Optional, which can greatly reduce product costs.

Detailed ways

Embodiments of the present invention are described in detail below. The embodiments described below are exemplary, only for explaining the present invention, and should not be construed as limiting the present invention.

A nano-microporous film, the nano-microporous film adopts each component raw material with the following mass fractions: polyolefin: 21.3-30 parts, processing aid: 70-78.5 parts, plasticizer; 0.02-0.1 part; Oxidant; 0.03-0.2 part, lubricant; 0.04-0.15 part, wherein the molecular weight of the polyolefin is 50,000-1.5 million.

The processing aid is a high-viscosity aid, and the raw material after the processing aid is mixed with a certain molecular weight polyolefin has higher intermolecular force and better toughness.

The polyolefin is usually polyethylene or polypropylene.

The processing aid may be paraffin oil, and the molecular weight of the paraffin oil is preferably 100-500 g/mol.

The higher the molecular weight, the greater the intermolecular force, the greater the strength, and the better the structural stability. On the other hand, the higher the molecular weight, the greater the melt index, and the higher the processing difficulty. Reasonable choice is required.

Preferably, the carbon chain number of the paraffin oil is between 6-40, and it is a low molecular oil that has undergone complete isomerization. The higher the carbon chain number, the lower the boiling point of the paraffin oil. The more volatile the paraffin oil is, the lower the solvent concentration is; on the contrary, the lower the carbon chain number, the higher the boiling point of the paraffin oil, the better the stability of the paraffin oil, but the higher the material cost, so the carbon chain number of the paraffin oil needs to be selected reasonably .

The plasticizer is a mixture of one or more of phthalic acid esters, aliphatic dibasic acid esters and phosphoric acid esters. The plasticizer has a plasticizing effect, which can enhance the flexibility of the raw material and make it easier to process. The phthalate plasticizer is preferably dioctyl phthalate (DOP), the aliphatic dibasic acid ester plasticizer is preferably dioctyl oxalate (DOA), and the phosphate ester plasticizer is preferably Use trioctyl phosphate (TOP).

The antioxidant is a mixture of one or more phenolic antioxidants, and the mixture of multiple antioxidants can achieve a synergistic antioxidant effect.

The lubricant is preferably a stearic acid-based polymer compound, and the lubricant is used to reduce friction between films or between films and processing equipment.

A method for making a nano-microporous membrane, comprising the following steps:

S1: Production of raw materials; polyolefin, plasticizer, antioxidant and lubricant are mixed according to the mass fraction ratio of each component in the above-mentioned nano-microporous film, stirred evenly at a temperature of 20 ℃ ~ 50 ℃, and then added to the extrusion equipment , followed by proportional addition of processing aids.

S2: extrusion molding; the mixture in step S1 is melt-extruded from a twin-screw extruder, and then cast into sheets through a casting roll to obtain a polyolefin cast base film.

S3: stretching; at 90-110° C., the cast base film is firstly stretched in the longitudinal direction, and then stretched in the transverse direction to obtain a polyolefin microporous film with a microporous structure.

S4: Secondary stretching: First, add volatile reagents to the polyolefin microporous film, extract the high-boiling solvent white oil in the polyolefin microporous film using an extraction process, and then perform transverse stretching again at 100-120 °C stretched, dried and corona treated to obtain a polymer nanoporous membrane.

The extrusion equipment in step S1 is a twin-screw extruder.

The process of melt extrusion is as follows: the raw material mixture in step S1 is melted and extruded at 180-260 ° C using a twin-screw extruder, passed through a casting die or an annular blowing die, cast into a film, and after cooling ( For example, forced cooling) is drawn at a certain speed to obtain a polyolefin cast base film with uniform thickness. Specifically, the melt extrusion can be extruded by a single-screw or twin-screw extruder. Considering the molding and plasticizing properties of the material, the extrusion temperature is not lower than 190°C. The temperature of the rolls used for casting film formation is 30-100° C., the production line speed is 60-120 kg/h, and the forming thickness is 10-40 microns.

After the casting film is formed, the obtained polyolefin cast base film can be further heat-treated to further improve the crystallinity of the base film and the integrity of the wafer. .

In the present invention, a reagent with lubricating effect is firstly added to the raw material, which is beneficial to the stirring and mixing of the raw material, and the raw material can be extruded more smoothly and smoothly. After one stretch, a volatile reagent is used to extract the white oil. The lubricating component of the polyolefin microporous film after the extraction process is reduced, the proportion of polyolefin is increased, and the intermolecular force is also increased. At this time, it can be stretched again on the basis of the polyolefin microporous film. , due to the large intermolecular force, the pore size of the stretched polyolefin microporous membrane can still maintain a small size.

The nano-microporous membrane prepared by the above method can be used as a barrier layer in medical anti-virus masks.

Various suitable compositions, manufacturing methods and performance test results of the nano-microporous membrane are exemplified by various embodiments below.

Example 1

The raw material components are: polyethylene with a molecular weight of 600,000, plasticizer 250ppm, antioxidant 400ppm, lubricant 500ppm, paraffin oil molecular weight 400g/mol, the mass fraction ratio of paraffin oil and polyethylene is 7: 3, the mixed raw material The total weight is 20g, melt extruded with a twin-screw extruder, cast into a thick film, the extrusion temperature is 220°C, the extrusion rate is 120kg/h, the casting temperature is 60°C, and the thickness of the thick film formed by casting is 30um. The longitudinal stretching ratio is 10 times the stretching ratio, the longitudinal stretching temperature is 90 °C, the primary transverse stretching ratio is 10 times the stretching ratio, the primary transverse stretching temperature is 100 °C, the extraction temperature is 15 °C, and the secondary transverse stretching ratio is The stretching ratio is 10 times, the secondary transverse stretching temperature is 120°C, and the polymer nano-microporous film is obtained after drying, and the thickness of the nano-microporous film is 5um. After testing, the overall pore size of the microporous membrane produced in this example is less than 100 nm, only a small amount is higher than 100 nm, and the average pore size is 52 nm, which reflects the effective physical isolation of various viruses.

Example 2

The raw material components are: polyethylene with a molecular weight of 1.5 million, plasticizer 600ppm, antioxidant 800ppm, lubricant 1000ppm, paraffin oil molecular weight 200g/mol, the mass fraction ratio of paraffin oil and polyethylene is 7: 3, the mixed raw material The total weight is 20g, melt extruded with a twin-screw extruder, cast into a thick film, the extrusion temperature is 220℃, the extrusion volume is 60kg/h, the casting temperature is 60℃, and the thickness of the thick film formed by casting is 30um . The longitudinal stretching ratio is 7 times the stretching ratio, the longitudinal stretching temperature is 95 °C, the primary transverse stretching ratio is 10 times the stretching ratio, the primary transverse stretching temperature is 115 °C, the extraction temperature is 20 °C, and the secondary transverse stretching ratio is The stretching ratio is 10 times, the secondary transverse stretching temperature is 115°C, and the polymer nano-microporous film is obtained after drying, and the thickness of the nano-microporous film is 2um. After testing, its average pore size is 64nm.

Example 3

The raw material components are: polyethylene with a molecular weight of 600,000 (melt index), plasticizer 800ppm, antioxidant 1500ppm, lubricant 1200ppm, paraffin oil molecular weight 600g/mol, and the mass fraction ratio of paraffin oil to polyethylene is 3:1 , the total weight of the mixed raw materials is 20g, melt extruded with a twin-screw extruder, cast into a thick film, the extrusion temperature is 220 ° C, the extrusion volume is 80 kg/h, the casting temperature is 60 ° C, and the casting is formed. The thickness of the thick film is 30um. The longitudinal stretching ratio is 8 times the stretching ratio, the longitudinal stretching temperature is 90 °C, the primary transverse stretching ratio is 10 times the stretching ratio, the primary transverse stretching temperature is 110 °C, the extraction temperature is 18 °C, and the secondary transverse stretching ratio is 10 times the stretching ratio, the secondary transverse stretching temperature is 110°C, and the polymer nano-microporous film is obtained after drying, and the thickness of the nano-microporous film is 4um. After testing, the average pore size is 71nm.

Example 4

The raw material components are: polypropylene with a melt index of 2g/10min, plasticizer 900ppm, antioxidant 1800ppm, lubricant 1400ppm, paraffin oil molecular weight 200g/mol, and the mass fraction ratio of paraffin oil and polyethylene is 3:1. The total weight of the raw materials is 20g, which is melt-extruded with a twin-screw extruder, and cast into a thick film. The thickness is 30um. The longitudinal stretching ratio is 9 times the stretching ratio, the longitudinal stretching temperature is 100 °C, the primary transverse stretching ratio is 10 times the stretching ratio, the primary transverse stretching temperature is 120 °C, the extraction temperature is 20 °C, and the secondary transverse stretching ratio is The stretching ratio is 10 times, the secondary transverse stretching temperature is 120°C, and the polymer nano-microporous film is obtained after drying, and the thickness of the nano-microporous film is 3um. After testing, its average pore size is 63nm.

Table 1 lists the measurement results of each parameter of the nano-microporous membranes prepared in Examples 1-4. Compared with the existing technology, the microporous membrane has outstanding advantages, mainly in the following points: (1) The pore size is small, the pore size is below 100nm, and can even reach 50nm, which can block viruses 100% and reflect better protection. (The aperture of the meltblown layer of the existing mask is 100-200nm); (2) the thickness is thin, only 2-7um, which is one-tenth of the thickness of the meltblown layer of the existing mask, and it is more comfortable to wear after being made into a mask (the existing The thickness of the meltblown layer of the mask is 20-40um); (3) the tensile strength is high, and the tensile strength is above 200Mpa, reflecting higher safety (the strength of the existing mask meltblown layer is about 100MPa). (4) The electrostatic effect is better, and the virus capture ability is higher.

Table 1

In addition, comparing Example 1 and Example 2, the polyethylene in Example 2 has a larger molecular weight, higher intermolecular force, and better toughness, so Example 2 can be stretched thinner. Similarly, compared with Example 3, Example 1 has a larger proportion of polyethylene, and the overall toughness of the microporous membrane is better. In Example 4, polypropylene is used instead of polyethylene, and nano-microporous membranes with more optimized performance of various parameters can also be obtained by using the method of the present invention.

In this specification, schematic representations of such terms do not necessarily refer to the same embodiment. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in one or more embodiments.

Taking the above ideal embodiments according to the present invention as inspiration, and through the above description, relevant personnel can make various changes and modifications without departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the contents in the specification, and the technical scope must be determined according to the scope of the claims.

Claims (10)

1. The nano microporous membrane is characterized by adopting the following raw materials in percentage by mass:

polyolefin: 21.3 to 30 parts by weight of a stabilizer,

processing aid: 70 to 78.5 parts of (C),

a plasticizer; 0.02-0.1 part;

an antioxidant; 0.03 to 0.2 part by weight,

a lubricant; 0.04-0.15 part, wherein the molecular weight of the polyolefin is 5-150 ten thousand.

2. The nanopore membrane of claim 1, wherein: the polyolefin is polyethylene or polypropylene.

3. The nanopore membrane of claim 1, wherein: the processing aid is paraffin oil, and the molecular weight of the paraffin oil is 100-500 g/mol.

4. The nanopore membrane of claim 1, wherein: the plasticizer is one or a mixture of more of phthalic acid esters, aliphatic dibasic acid esters and phosphate esters.

5. The nanopore membrane of claim 1, wherein: the antioxidant is a mixture of one or more phenolic antioxidants.

6. The nanopore membrane of claim 1, wherein: the lubricant is a stearic acid polymer compound.

7. The preparation method of the nanometer microporous membrane is characterized by comprising the following steps:

s1: preparing raw materials; mixing polyolefin, a plasticizer, an antioxidant and a lubricant according to the mass fraction ratio of each component in the nano microporous membrane of any one of claims 1 to 5, stirring uniformly at the temperature of 20-50 ℃, adding into an extrusion device, and then adding a processing aid in proportion;

s2: extrusion molding; the mixture obtained in the step S1 is melted and extruded from a double-screw extruder, and then is cast by a casting roll to form a polyolefin casting base film;

s3: stretching; at 90-110 ℃, firstly longitudinally stretching the cast base film, and then transversely stretching to obtain a polyolefin microporous film with a microporous structure;

s4: and (3) secondary stretching: firstly, adding a volatile reagent on the polyolefin microporous membrane, extracting the high-boiling-point solvent white oil in the polyolefin microporous membrane by using an extraction process, then transversely stretching again at the temperature of 100-120 ℃, and drying and corona-treating to obtain the polymer nano microporous membrane.

8. The method of claim 7, wherein: the extrusion apparatus in step S1 is a twin-screw extruder.

9. The method of claim 7, wherein: the volatile agent in step S4 is dichloromethane.

10. Use of the nanopore membrane prepared by the method of any one of claims 7-9 in a medical anti-virus mask.