JP3004715B2 - New filter material for surgical and clean room masks - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a novel filter material used for surgical masks and clean room masks. This new filter material is a protective non-woven fabric, or a non-woven fabric and a laminate of a stretched polytetrafluoroethylene laminate having a high degree of permeability only at the periphery of the mask,
It uses a microporous stretched polytetrafluoroethylene filter membrane bonded to a support structure-free structure. The present filter material has a structure having a high filtering ability and low airflow resistance. Further, in the filter material including the stack, the generation of lint is small.

BACKGROUND ART Historically, respiratory and facial masks have been worn to prevent the inhalation of toxic or unpleasant dust, smoke, or bacteria. Surgical masks are intended to protect patients from contamination by operating room staff and the like.
The performance of facial masks as the volume of clean room operations increases in the semiconductor and computer industries and in the industries related to materials for use in space, or also due to the emergence of acquired immunodeficiency syndrome (AIDS) Is being taken seriously. In the semiconductor, computer, and other industries, there is a need to prevent very fine patterns on semiconductor chips and contamination of the surface of almost any device that comes into contact with outer space. In the medical / surgical field, there is a need to prevent medical staff from contacting the body fluids of patients with AIDS or hepatitis. However, in each case, it has higher filtration performance,
There is a demand for a highly wearable mask. Further, when used in a clean room, it is necessary that lint is not generated by wearing a mask. In either case, the mask is preferably disposable for hygiene and cost reasons.

Class 100 as clean rooms improve
And class 10 clean rooms have been replaced by class 1000 clean rooms. Class 1 clean rooms are also currently in use. The smaller the numerical value of this class, the smaller the allowable maximum particle diameter together with the allowable total particle number. In the semiconductor industry, cleanliness is directly correlated to the production of products that pass the standards.

As you can imagine, very clean facilities
Designed with air filters, air exchangers, laminar flow hoods, and building materials that allow for such low particle counts. However, although the human operator is also required to be within this level, it is clear that the human body is a major source of particulate contamination. Hair, skin particles, lint from clothing, and scattering of dust adsorbed on clothing are all major pollutants. These substances have become controllable through the development of protective clothing such as lint-free clothing (lintless suits), headgear, boots, and how covers. An unsolved problem is contamination by exhalation.

Exhaled air pollution results from coughing or sneezing, and residues in the mouth and trachea of smokers. The breath of a smoker contains particles with a particle size of 0.2-0.4 μm, even after 10 minutes of smoking, 30 to about 500 times that of a non-smoker. Non-smokers usually exhale little particles (Hoenig, Dan
iels, J. of Environmental Sciences, 48-52, March / Apri
l 1984).

Further, the clean room mask must not emit lint. The biggest drawback of many currently used masks is the generation of lint.

Since clean room operators always wear masks, masks that are more wearable than conventional masks are highly desirable.

Medical / surgical masks require high aerosol and bacterial filtration capabilities for safety and low air permeation resistance to facilitate breathing.

Air passage resistance is U.S. military standard MIL-M-36954C, test method
Measure according to 4.4.1.2. This transmission resistance is indicated by a value “Delta P”. "Delta P" refers to the pressure difference created in the filter material when a certain amount of air is passed through a particular portion of the filter. What is Delta P?
It is shown in terms of millimeters of water corresponding to the pressure of the airflow passing through the filter.

Since the value of Delta P is a measurement of the airflow passing through the filter, it also correlates with the wearability of the mask felt when breathing through a facial mask made of the present filter material. The higher the Delta P value is, the more the person wearing the face mask feels uncomfortable.

In order to breathe easily, a low Delta P value is essential. On the other hand, the smaller the filter hole, the higher the filterability, but the Delta P value also tends to increase.

It is an object of the present invention to solve these problems.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides a microporous permeable filter membrane, preferably
A microporous stretched polytetrafluoroethylene membrane is used as a facial mask by combining 1) a protective cloth, or 2) a protective laminate of a cloth and a microporous stretched polytetrafluoroethylene having high permeability. It is an object of the present invention to provide a filter material having a low resistance, that is, a low Delta P value and a very high filterability, and further provide a filter material having improved breathability. Select several types of membranes and select Delta P
By selecting a method of binding the protective layer to a filter membrane that does not significantly increase the value, high airflow, low delta P
Value and high filtration capacity became possible. As a means for connecting the protective cloth layer or the laminate to the filter membrane, it is preferable that the connection be made only at the peripheral portion of the filter mask-sized sample without using the conventional lamination technique. As a result, a filter membrane which does not require a support structure and which minimizes the increase in the delta P value as a whole was obtained. To protect the filter membrane,
When using a laminate of a nonwoven fabric and a microporous stretched polytetrafluoroethylene membrane having a high permeability, the porous stretched polytetrafluoroethylene portion having a high permeability of the laminate is selected from PTFE. Because of the high permeability of PTFE, the requirement of easy wearing is satisfied when used for a surgical mask. A porous stretched polytetrafluoroethylene having a high permeability is arranged on both surfaces of the composite,
By disposing a microporous stretched polytetrafluoroethylene membrane for filtration, which does not require a support structure, inside both laminates, the Delta P value is small, no lint is generated, and it is suitable for use in a clean room. Thus, a useful complex is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an embodiment of the present invention. The laminated composite (20) consists of a microporous stretched polytetrafluoroethylene filter membrane (1) with no support structure and a two-layer cloth (2)
Is attached to the periphery of the filter material by sewing, welding, bonding, or fusion bonding (3).

FIG. 2 shows a second embodiment of the present invention, in which two layers of microporous stretched polytetrafluoroethylene filter membrane (5) having no support structure are used, and the outer two layers of cloth (6) and its periphery are provided. It is melted and bonded at the portion (7) to form the composite (21).

FIG. 3 shows yet another embodiment of the present invention, wherein a microporous stretched polytetrafluoroethylene filter membrane (8) without a support structure comprises a porous stretch having a very high permeability.
Laminate (9) consisting of PTFE membrane (10) and non-woven fabric (11)
The two layers are joined so that the nonwoven fabric surface is in contact with the membrane (8). The laminated composite (22) is joined at its periphery by seams (12).

FIG. 4 shows another embodiment of the present invention, wherein the microporous expanded polytetrafluoroethylene filter membrane (13) comprises a nonwoven fabric (15) and an expanded polytetrafluoroethylene membrane having a very high permeability ( Laminate (14) 2 consisting of 16)
In one layer of the laminate in contact with the core film (13), the nonwoven fabric surface is in contact with one surface of the core film, and in another layer, the microporous stretched polytetrafluoroethylene layer is the core film (13). Are joined so as to be in contact with the other surface of the These layers are sewn, welded,
Bonded or fused together to form a composite (23).

DETAILED DESCRIPTION OF THE INVENTION What determines the balance between wearability and Delta P is the efficiency of removing particles of the filter material.
Its size is largely related to the efficiency of removing particles, aerosols and bacteria at submicron levels. In the novel filter material of the present invention, it is possible to change this balance as needed, that is, efficiency and wearability,
It can be changed as needed.

For the evaluation of surgical masks, see US Military Standard MIL-M-3.
The criteria defined by 6954C are a minimum of 95 bacteria tested.
% Removal, i.e., a bacterial filtration rate of 95% or more, as determined by the test method described in 4.4.1.1.1 of the same standard. In addition to removing particles, liquids such as splashed blood and other body fluids must also be repulsive.

Although there is no such well-defined standard for filter materials for clean rooms, it is clear that contamination by submicron levels as well as contamination by submicron levels are relevant. clean·
To determine the effectiveness of the filter material for working in a room, a submicron level sodium chloride aerosol was used to test the filterability of particles of this size range. In addition, a lint (Lint) generation test (Helmke / Drum test) was performed to determine which composite structure produced the least amount of lint. Development of the mask filter material WLGore and Associates, Elkton, MD. Manufacturing, delta P value as a filter membrane in the range of 1.34mmH ₂ O of 3.32mmH ₂ O, to select a microporous stretched polytetrafluoroethylene membrane It started with that. The membrane filtration capacity of the membrane itself is high, usually well over 90%. However, using only a microporous stretched polytetrafluoroethylene membrane is a very thin membrane that is easily broken and lacks in thickness,
Not practical, because it is cumbersome. There is a need for membrane protection and support structures, but this should not significantly increase Delta P.

Continuous filament polypropylene having an open structure,
The use of a polyester or polyamide nonwoven has been found to be effective in protecting the microporous expanded polytetrafluoroethylene filtration membrane without unduly increasing Delta P. The weight per square yard ranges from 1.0 oz to 1.5 oz and is available from the Hanes Convesting Company, Conovec, NC
"Elite 20 White" and "Elite 45 White" (El
ite 45 White) is preferred. Hydrophobic fabrics such as polypropylene have the advantage of being water repellent, i.e., not wet during use, and of being thermoplastic. If it is thermoplastic, the hydrophobic cloth can be bonded to the microporous stretched polytetrafluoroethylene filter membrane by thermal bonding or welding.

Delta P values in the complex, about 5~6mmH ₂ O or less, preferably in a 4mmH ₂ O or less, the conventional bonding method for bonding the filter membrane and the outer fabric layer is necessary to avoid is there. When the conventional heat bonding method or the bonding method is used, the Delta P value becomes high. For example, Delta P value is 1.9m
The mH ₂ O filter membranes, delta P value was coupled by continuous thermal bonding polypropylene nonwoven 0.18mmH ₂ O, delta P value 3.3mmH ₂ O laminate was obtained. When the same microporous stretched polytetrafluoroethylene filtration membrane was bonded to two layers of the same nonwoven fabric by sewing or thermal bonding around a mask-sized sample having a size of 4 inches × 7 inches, the delta P value was 2.4 mm H ₂ O, which was only slightly greater than the theoretical value of the Delta P value obtained by adding the Delta P values of both components. Therefore, the feature of the present invention is a structure that does not require a support structure for a filter membrane in which a protective cloth and a laminate are bonded only at the periphery of a mask-sized sample. With such a structure, the high filterability and very good wearability of the filter material of the present invention have become one.

A filter membrane without a support structure and a continuous filament nonwoven fabric, or a laminate of the fabric and a highly permeable stretched polytetrafluoroethylene, are sewn, thermally bonded,
It is possible to bond the sample around the mask size by bonding or fusion. The composite produced by this method is sufficiently rigid to support the attachment of an elastic band or band to hold the mask in position on the body.
As a method for bonding the composite, thermal bonding for bonding by utilizing the thermoplasticity of the nonwoven fabric is desirable.

In order to provide a lint-free property to a clean room mask, a laminate in which a stretched polytetrafluoroethylene membrane having a high permeability and a continuous filament nonwoven fabric have been used. Delta P values of these film itself is a level of from 0.45 to 0.7 inches H ₂ O, delta P value of the laminate of the "Elite 45 White (Elite 45 White)" nonwoven polypropylene, 1.5 inches H ₂ O It was below. Although the filterability of these laminates was low, its intended use is to prevent the generation of lint.

The filter composition with low lint generation consists of the layers of the laminate, with the stretched polytetrafluoroethylene layer having a high permeability of the laminate facing outward, and the polypropylene fabric surface inside the laminate supporting, Adjacent to one side of the structureless microporous stretched polytetrafluoroethylene filter membrane. On the other side of the filter membrane, another set of similar laminates, the polypropylene side of the laminate is adjacent to the filter membrane, and a stretched polytetrafluoroethylene layer having a high permeability of the laminate. However, it is installed so that it may face the outside.

For composites used in surgical masks, a layer of a mask large sample of these composites for a clean room is bonded by heat bonding or welding along the periphery of the sample.

Surgical and clean room filter media were prepared according to the principles described above and tested for their bacterial filtration capacity and Delta P. Table 1 shows the results.

All samples tested are U.S. military standards (ibid.)
Easily reached the bacterium filtration capacity standard (95% or more) set by the Delta P value of 4 mmH ₂ O or less.

Next, a test was performed using a sodium chloride aerosol. Table 2 shows the test results.

As shown by the results in Table 2, the filtration capacity can be adjusted by selecting microporous expanded polytetrafluoroethylene filtration membranes with different permeability, and may be slightly affected by the choice of outer protective cloth. Is adjustable.

The lint generation test of the sample is performed by Helmke drum (Helm
ke Drum) test. The results are shown in Table 3.

As shown in Table 3, by placing a porous stretched polytetrafluoroethylene layer having a high permeability as in Sample E on the outside, the comparative complex was not protected by a highly porous membrane. In comparison with (A), the generation of lint was reduced by 67%.

Filtration of bacterial aerosols For the effectiveness of filter media, US Military Standard MIL-M-36954C
The test was performed as described in section 4.4.1.1.1. The test procedure is described below.

Filtration of virus aerosol The same test as the bacterial filtration described above was carried out except that the agar plate contained bacteria for host of the specific test virus. Commonly used viruses are T7 or Phi-X-1
74.

Delta P For Delta P, which is breathable, US Military Standard MIL-M
The test was performed according to the method described in −36954C section 4.4.1.2.

4.4.1.2. Air exchange pressure The air exchange pressure of various materials is measured using a device that measures the pressure difference required to allow air to pass through the measured surface area under a constant ventilation rate. To measure the pressure difference, use a water filled manometer (m1 and m
Use 2). Air flow measurements were made by Roger Gilmont Instruments
t) Use a (RGI) flow meter or a flow meter with equivalent accuracy. To adjust the flow rate, an electric vacuum pump sucks air through the device using a needle valve. Place the test substance vertically in an orifice with a diameter of 2.5 cm,
The test substance is fixed in line with the air flow and so as to block the air flow. Activate the pump and adjust the air flow to 8 liters per minute. Manometer values m1 and m2
Read and record. This operation is performed at five different locations of the mask, and the average of the measured values is obtained. The air exchange pressure is calculated according to the following equation.

In the formula, _m1 represents the average value of the measurement values obtained using the manometer No. 1 at five places in the low-pressure part of the test substance (mmH
₂ O).

_m2 is the manometer N at 5 places in the high pressure section of the test substance.
Indicates the average value of the measurement values obtained using o.2 (mmH ₂ O).

4.9 is the surface area (cm ² ) of the test substance.

Delta P is the pressure difference per cm ² of the test substance, mmH ₂ O
It is represented by

Helmke drum test for lint generation Recommended Laboratory for Environmental Science (IES-RP-CC-003-87-T,
Helmke drum test for measuring the amount of separable particles having a particle size of 0.3 μm described in October 1989)
It is described below.

Sodium Chloride / Aerosol Filtration Capability In the same manner as in the above device, the filter material was fixed and hermetically sealed, and the sodium chloride / aerosol filtration capability was measured using a device in which the speed of air passing through the sample was set at 3.2 m / min. The sodium chloride aerosol is mixed well into the air stream at the flow rate and passed through a sample of air filter material. Small pieces of the sample are taken from the test stream and the through stream, and the sample is subjected to a dual laser particle counter that measures the exact number of sodium chloride particles in each stream. The penetration value is only the value of the number of particles having a narrow range of particle sizes in the through-flow compared to the number of particles of the same range in the test airflow. The filtration value (%) is 100- (1
00 × penetrating particle ratio).

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Siegfried, Carroll A. United States, Maryland 21921, Elkton, Goodneck Court 129 (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 39/16 B01D 69/12

Claims (11)

(57) [Claims] (1) a. Protective nonwoven fabric or b. Surgical and surgical composites comprising a protective laminate comprising a nonwoven fabric and a highly permeable stretched polytetrafluoroethylene membrane bonded to one or more microporous filter membranes that do not require a support structure. A filter material used for a clean room mask, wherein in both cases (a) and (b), the protective nonwoven fabric or the nonwoven fabric surface of the laminate is in contact with both surfaces of the filter membrane, and the bacterial filtration ability of the composite The filter material used for surgical and clean room masks, wherein the filter membrane is 95% or more, and the filter membrane is bonded to a or b only in a peripheral material portion of the filter material. 2. The filter material according to claim 1, wherein the delta P value of the composition is 5 mm or less. 3. The filter material according to claim 1, wherein the delta P value of the composition is 4 mm or less. 4. The filter membrane has a delta P value of 1.34 mmH ₂ O.
_2. The filter material according to claim 1, wherein the filter material is a microporous stretched polytetrafluoroethylene having a pressure of between 3.3 and 3.32 mmH2O. 5. The filter material according to claim 1, wherein the fabric is a non-woven fabric of continuous filament polyamide, polyester or polyolefin. 6. The filter material according to claim 1, wherein the fabric is a continuous filament polypropylene nonwoven fabric. 7. The protective laminate comprises a continuous filament polypropylene nonwoven fabric bonded to a highly permeable stretched polytetrafluoroethylene membrane, the entire composite comprising a microporous stretched polytetrafluoroethylene.
2. The filter material according to claim 1, wherein the filter film and the protective laminate are composed of two layers of a laminate in which both fabric surfaces of the laminate are connected to one surface of the filter film. 8. The amount of lint generated by the filter material as compared to a similar composite comprising two layers of a continuous filament nonwoven protective fabric bonded to one side of a microporous stretched polytetrafluoroethylene filter membrane. The filter material according to claim 5, wherein is less than or equal to 35%. 9. The filter material according to claim 8, wherein the peripheral portions are joined by sewing. 10. The filter material according to claim 8, wherein the peripheral portions are joined by an adhesive. 11. The filter material according to claim 8, wherein the peripheral portions are joined by heat bonding or welding.