JP2002209822A - Heat resistant cleaning sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat resistant cleaning sheet which is tough, is foliate and is easy to use. SOLUTION: This heat resistant cleaning sheet consists of a porous film which is composed of a methaphenylene isophthalamide-base polymer, has many uniform micropores on the surface and in the inside and has a void ratio of 40 to 90% and a surface aperture ratio of 10 to 70%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant cleaning sheet comprising a porous film of a polymetaphenylene isophthalamide polymer.

[0002]

2. Description of the Related Art Conventionally, dust such as cotton dust, lint, hair, soil dust, and the like from general living environment, and minute dust and dust generated at a manufacturing site such as a factory or a work site, etc. are entangled with fibers. Sheets and films having voids that can be collected on the surface of non-woven fabrics and fiber woven fabrics formed on paper, and paper and the like are used (JP-A-11-29).
5). At present, various materials that entangle even fine dust have been developed and put on the market, but the surface material for cleaning dirt that has accumulated or adhered to high-temperature places is currently the above-mentioned surface material made of aramid or polyamide fiber. There is only. However, in order to increase the collection efficiency for finer dust, it is necessary to reduce the fiber diameter of the fiber bundle to reduce the bulk density of the fiber, but on the other hand, it tends to be torn or torn, so strength,
Usability will be poor. The prior art has not been able to uniformly improve the collecting performance, strength, and ease of use.

[0003]

SUMMARY OF THE INVENTION On the other hand, an object of the present invention is to provide a heat-resistant cleaning sheet made of a polymetaphenylene isophthalamide-based porous film which is tough, thin, and easy to use. It is.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the inventors of the present invention have found that the present invention can be achieved by a cleaning sheet comprising a porous film of a metaphenylene isophthalamide polymer, and have reached the present invention. .

That is, the present invention is as follows. 1. It is made of a metaphenylene isophthalamide-based polymer, has a large number of uniform fine pores on its surface and inside, and has a porosity of 40 to 90%, and a porous film having a surface porosity of 10 to 70%. Heat resistant cleaning sheet. 2. A heat-resistant cleaning sheet comprising a porous film having a surface having an average opening diameter of 0.5 to 20 μm and a thickness of 1 to 200 μm.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a metaphenylene isophthalamide polymer (hereinafter sometimes referred to as a polyamide) refers to a polymer obtained by polycondensation of a meta-aromatic diamine and a meta-aromatic dicarboxylic acid halide, The copolymerization ratio as an amine component or a carboxylic acid component is 40 on a molar basis with respect to the total amount of the aromatic diamine and the meta-aromatic dicarboxylic acid halide.
A polymer obtained by polycondensation using para-aromatic diamine, para-aromatic dichloride, aliphatic diamine, aliphatic dicarboxylic acid, alicyclic diamine, or alicyclic dicarboxylic acid at a ratio of not more than mol%.

More specifically, examples of the meta-aromatic diamine include 1,3-phenylenediamine, 1,6-naphthalenediamine, 1,7-naphthalenediamine, 2,7-naphthalenediamine, and 3,4'-biphenyldiamine. Further, as the meta-aromatic dicarboxylic acid, isophthalic acid, 1,6-
Examples include naphthalenedicarboxylic acid, 1,7-naphthalenedicarboxylic acid, and 3,4-biphenyldicarboxylic acid.

[0008] As for the copolymerized monomer, specifically, para-phenylenediamine as para-aromatic diamine,
4,4′-diaminobiphenyl, 2-methyl-paraphenylenediamine, 2-chloro-paraphenylenediamine, 2,6-naphthalenediamine and the like, terephthalic acid chloride as para-aromatic dicarboxylic acid dichloride,
Biphenyl-4,4'-dicarboxylic acid chloride, 2,
Examples of aliphatic diamines include hexanediamine, decanediamine, dodecanediamine, ethylenediamine, hexamethylenediamine and the like, and aliphatic dicarboxylic acids include ethylenedicarboxylic acid and hexamethylenedicarboxylic acid. However, neither is limited to these.

A preferred method for producing a cleaning sheet comprising a porous membrane of the metaphenylene isophthalamide polymer of the present invention is as follows.

A solution in which a polymetaphenylene isophthalamide-based polymer is dissolved in an amide-based solvent (hereinafter referred to as a dope) is cast on a support, and the cast product is placed on the support while the polymetaphenylene isophthalamide-based polymer is dissolved. It is immersed in an amide-based solvent (hereinafter referred to as a coagulation liquid) containing an incompatible substance to coagulate, washed with water and dried to produce a polymetaphenylene isophthalamide-based polymer porous membrane. The separation from the support may be performed at any stage after solidification. Further, stretching and heat treatment may be added for the purpose of controlling the pore diameter.

The concentration of the polymer in the dope according to the present invention is preferably 3 to 30% by weight, more preferably 5 to 30% by weight.
20% by weight.

Examples of the amide-based solvent include polar solvents such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, but are not limited thereto, and the object of the present invention is as follows. Any material may be used as long as it dissolves the polymetaphenylene isophthalamide polymer according to the present invention and contains an amide group. The reason why the amide solvent is used is to dissolve the polymetaphenylene isophthalamide polymer according to the present invention.

In order to improve the solubility of the polyamide, a monovalent or divalent cation metal salt can be used. The metal salt can be present in the amide solvent according to the present invention at a ratio of 0 to 50 parts by weight based on 100 parts by weight of the polymetaphenylene isophthalamide polymer, and specifically, calcium chloride, lithium chloride, nitric acid, and the like. Lithium, magnesium chloride and the like. The method for dissolving the metal salt in the amide-based solvent may be a conventional method, and may be before, during, or after the dissolution of the polymetaphenylene isophthalamide-based polymer.

Examples of the support include a metal drum, an endless metal belt, and an organic film such as polypropylene, polyethylene, and polyester terephthalate. More preferably, silicon or the like which has been subjected to a release treatment is preferably used.

The temperature of the dope in casting is not particularly limited, but the viscosity is 1 to 2,000.
It is preferred to choose between Poise, preferably 5
Choose to be between ~ 500 Poise. Further, in order to keep the shape of the cast in a sheet shape, it is effective to select the temperature range of the support and the atmosphere around the support, and to adjust the atmosphere around the support by blowing air when the present invention is practiced. However, these conditions can be determined by trial and error.

Examples of the amide solvent used for the coagulation bath include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide and the like, and preferably N-methyl-2. Using pyrrolidone;

Further, substances which are inactive to the polymetaphenylene isophthalamide-based polymer and the amide-based solvent, are not compatible with the polymetaphenylene-isophthalamide-based polymer, and are compatible with the amide-based substance include: Although various substances such as lower alcohols and lower ethers can be used, it is particularly preferable to use water. Mixtures of these can also be used.

In the coagulation liquid, a metal salt may be used in an amount of 1 to 10% by weight based on the amide coagulation liquid for the purpose of adjusting the pore diameter. Specifically, calcium chloride, lithium chloride,
Examples include lithium nitrate and magnesium chloride.

The concentration of the amide-based solvent in the coagulation liquid is 30% by weight or more and 80% by weight or less, and more preferably 50% by weight to 70% by weight, based on the whole coagulation liquid. The temperature of the coagulating liquid is from 0 ° C to 98 ° C, more preferably from 20 ° C to 90 ° C.

When the concentration of the amide solvent is less than 30% by weight and the temperature is less than 0 ° C., the number of pores on the surface of the produced polyamide porous membrane decreases, and the pore diameter decreases.
There is a tendency that the polyamide porous membrane has a low porosity. On the other hand, when the concentration exceeds 80% and the temperature exceeds 98 ° C., the polymer may be granulated and the polyamide porous film may not be formed. Further, when either one of the temperature and the concentration exceeds the above range, it may be a drawback depending on the use, if not so much as when both of them exceed the above range.

The cast, which is a coagulated porous membrane, is then transferred to a washing step, where it is washed with water. The temperature at this time is not particularly limited because it hardly affects the porous shape. This step can be omitted. Whether it can be omitted can be determined by checking the results obtained by experiments and the like.

The drying may be performed to any degree, and includes drying from nip roll processing, which is usually called draining, to full-scale drying using a hot air dryer or the like. However, it is preferable that the cleaning sheet is maintained at a predetermined degree of dryness in order to secure a stable trapping property. Therefore, the degree of dryness is such that the water content is 100 parts by weight with respect to 100 parts by weight of the porous film in a completely dry state. Parts by weight or less, more preferably 30 parts by weight or less, particularly preferably 5 parts by weight or less.

The stretching may be performed by a wet method or a dry method. Further, any method such as uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching may be used. Biaxial stretching is preferred because the holes are deformed and the air permeability decreases. In the stretching, it is preferable to hold and restrain both sides with respect to the stretching direction from the viewpoint of suppressing a decrease in air permeability. The wet stretching is a method in which a polyamide film after solidification is stretched in an amide solvent containing a substance incompatible with a polymetaphenylene isophthalamide polymer. Examples of the amide solvent useful for the stretching bath include N-methyl-2-pyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide and the like, and preferably N-methyl-2.
Using pyrrolidone; Further, as a substance which is inactive to the polymetaphenylene isophthalamide-based polymer and the amide-based solvent and has no compatibility with the polymetaphenylene-isophthalamide-based polymer and has compatibility with the amide-based substance, a lower alcohol, Although various substances such as lower ethers can be used, it is particularly preferable to use water. Mixtures of these can also be used.

The concentration of the amide solvent in the stretching bath is preferably from 5 to 70% by weight, more preferably from 30 to 65% by weight, based on the entire stretching bath. The temperature of the stretching bath is 0 to
The temperature is preferably 98 ° C, more preferably 30 to 90 ° C.
° C. When the concentration of the amide-based solvent in the stretching bath is less than 5% by weight and the temperature of the stretching bath is less than 0 ° C., the plasticization of the polyamide porous membrane is insufficient, and the stretching ratio does not increase, which is expected. Young's modulus may not be obtained. When the concentration exceeds 70% by weight and the temperature exceeds 98 ° C., the dissolution of the polyamide porous membrane proceeds, and it is impossible to improve the Young's modulus by stretching, and the porous structure is collapsed and densification is caused. It proceeds and a polyamide porous membrane cannot be obtained. The stretching ratio is 1.3 to 5 times in the uniaxial direction or 1.3 to 10 times in the two orthogonal directions so that the porosity, the pore size distribution, and the balance of mechanical properties are appropriate. It is preferable to Here, the stretching ratio of 1.3 to 10 in the case of biaxial stretching can be determined as the product (area ratio) of the stretching ratios in both directions.

The heating method of the dry stretching may be either a contact method or a non-contact method. However, it is preferable to hold and restrain both sides in the stretching direction in terms of controlling the hole diameter. The stretching temperature is suitably from 270 to 380 ° C, more preferably from 290 to 360 ° C. If the stretching temperature is lower than 270 ° C., the porous film breaks at a low magnification, and if the temperature is higher than 380 ° C., the porous structure may be crushed and the pores may be closed and densified.
The stretching ratio is 1.3 to 5 times in the uniaxial direction or 1.3 to 10 times in the two orthogonal directions so that the porosity, the pore size distribution, and the balance of mechanical properties are appropriate. It is preferable to Here, the stretching ratio in the case of biaxial stretching is 1.
3 to 10 times can be determined as the product of the stretching ratios in both directions (area ratio).

If desired, the polyamide porous membrane obtained after the coagulation treatment may be immersed in a bath made of an amide solvent containing a substance incompatible with the polymetaphenylene isophthalamide polymer to promote crystallization. good. Examples of amide solvents useful for the immersion treatment bath include N-methyl-2-pyrrolidone, N, N-dimethylacetamide,
N, N-dimethylformamide and the like can be mentioned, and N-methyl-2-pyrrolidone is preferably used. Further, as a substance which is inactive to the polymetaphenylene isophthalamide-based polymer and the amide-based solvent and has no compatibility with the polymetaphenylene-isophthalamide-based polymer and has compatibility with the amide-based substance, a lower alcohol, Although various substances such as lower ethers can be used, it is particularly preferable to use water. Mixtures of these can also be used.

The concentration of the amide solvent in the immersion bath is preferably 50 to 80% by weight based on the entire stretching bath.
More preferably, it is 60 to 70% by weight. The temperature of the stretching bath is preferably 50 to 98 ° C, more preferably 6 to 98 ° C.
0-90 ° C. If the concentration of the amide solvent in the immersion treatment bath exceeds 80% by weight, the polyamide porous membrane may be dissolved and the porous structure may be destroyed. If the concentration is less than 50% by weight, crystallization may not proceed sufficiently. . If the temperature of the immersion treatment bath is lower than 50 ° C., the crystallization of the polyamide porous membrane may not progress or may not progress easily. If the temperature exceeds 98 ° C., the polyamide porous membrane dissolves and the porous structure is destroyed. May be done. After the immersion treatment, the porous polyamide membrane is preferably introduced into water, washed, and then dried. The washing and drying are preferably carried out in the same manner as described above for washing and drying after the coagulation treatment. In the polyamide porous membrane obtained after the immersion treatment, an unnecessary portion with respect to dimethylformamide at 20 ° C. is preferably 10% or more.

In the case where heat treatment is performed, 290 ° C. to 3
It is preferably carried out at a temperature of 80 ° C, more preferably 330-360 ° C. The heat treatment is performed for the purpose of crystallization, and if the temperature is lower than 290 ° C., the effect may not be sufficient. If the temperature exceeds 380 ° C., the polymer may be decomposed.

In this heat treatment, the porosity of the obtained porous membrane may be reduced, or the pores may be closed, so that the air permeability may be deteriorated. The effect can be minimized.

[0030]

EXAMPLES [Evaluation method] [Void ratio] The dried porous membrane was cut into a size of A (mm) × B (mm), and the thickness C (mm) and the weight D (g) were measured (A). , B, C, and D are appropriately selected). From the above, the apparent density E is obtained by the following equation. Subsequently, the true density F of the used polymer is obtained, and the porosity is calculated from the following equation. Apparent density E = D / (A * B * C) * 1000 (g / c
m ³ ) Porosity = (FE) / E * 100 (%)

[Surface porosity] A surface photograph at a magnification of 2000 times observed with a scanning electron microscope having a resolution of 4 to 7 nm was taken up by 150
× Develop at 200 mm width and use a scanner at a resolution of 100,000 pixels / 30000 mm 2 and a diameter of 0.01
The number of pixels is calculated for each hole of μm or more, and the sum is defined as the number of pixels in the opening portion. Surface aperture ratio = total pixels of each hole / 100,000 pixels * 1
00 (%)

[Average pore diameter] A surface photograph at a magnification of 2000 times observed with a scanning electron microscope having a resolution of 4 to 7 nm was taken up to 150
× Develop at 200 mm width and use a scanner at a resolution of 100,000 pixels / 30000 mm 2 and a diameter of 0.01
The number of pixels is calculated for each hole of μm or more, and the sum is defined as the number of pixels in the opening portion. The number of pixels of each hole is accumulated from the pore side, and the diameter of the hole having the number of pixels when the half of the surface porosity is achieved is defined as the average pore diameter.

Examples of the present invention will be described below. As an evaluation method of the examples, soil dust collecting property was evaluated according to the following operations, and the results are shown in Table 1. Surface to be cleaned (decorative board with a surface roughness of 1 μm) 30 cm x 3
Spray 0.1 g of JIS standard test dust uniformly on 0 cm. The seat is attached to a cushion material having a size of 8 cm × 12 cm, and the dust that has been sprayed is cleaned with a load of 29.4 N. The amount of dust collected and held on the sheet is measured.

Example 1 Para-type aramid fiber (single yarn fineness: 1.5 denier, number of fiber yarns: 500 to 2,000)
A heat-resistant cleaning sheet was prepared by adhering a porous film to one surface of a 100% woven fabric (plain woven fabric having a weft density of 5 to 20 fibers / inch) by dot bonding using an aramid varnish on one surface. The porous membrane is made up of N-methyl-2-pyrrolidone (NMP) so that the resulting polymer concentration is 10% by weight in equimolar amounts of metaphenylenediamine and isophthalic chloride.
The solution was polymerized in the reactor to produce a dope. At this time, calcium hydroxide was used as a neutralizing agent. Created dope with PE
It was cast on a T film to a thickness of 300 μm, immersed in a coagulation bath consisting of NMP / water = 60/40% by weight, 80 ° C. for 10 minutes, washed with water, dried at 150 ° C. for 5 minutes, Was obtained. This was further stretched at 350 ° C. in the biaxial direction at a four-fold area ratio to use a porous membrane obtained. This porous membrane has a thickness of 25 μm, a porosity of 60%, and a surface porosity of 50%.
%, And the average opening diameter was 10 μm.

Example 2 As in Example 1, para-type aramid fiber (single yarn fineness 1.5 denier, number of fiber yarns 500 to 500)
Woven cloth (weft density: 5-2)
(A plain woven fabric of 0 / inch), a filter cloth was prepared by adhering a porous membrane by dot bonding to one surface with an aramid varnish by the following method. The dope was prepared by solution polymerization of N-methyl-2-pyrrolidone (hereinafter referred to as NMP) in the porous membrane in N-methyl-2-pyrrolidone (NMP) so that metaphenylene diamine and isophthalic chloride were equimolar and the resulting polymer concentration was 8 wt%. At this time, calcium hydroxide was used as a neutralizing agent. Created dope with PET
Cast to a thickness of 150 μm on a film,
MP / water = 55/45% by weight, immersed in a coagulation bath consisting of 60 ° C. for 5 minutes, NMP / water = 60/40% by weight, 80
C. for 10 minutes, washed with water, and dried at 150.degree. C. for 5 minutes to use a porous membrane made of metaphenylene isophthalamide polymer. This is 35 more
A porous film obtained by heat treatment at 0 ° C. was used. This porous membrane has a thickness of 36 μm, a porosity of 75%, and a surface porosity of 30%.
%, And the average pore diameter was 5 μm.

Comparative Example Para-type aramid fiber (single yarn fineness: 1.5 denier, number of fiber yarns: 500 to 20)
00) (a plain weave having a weft density of 5 to 20 weaves / inch).

[0037]

[Table 1]

[0038]

According to the present invention, it is possible to provide a heat-resistant sheet made of a polymetaphenylene isophthalamide-based porous membrane which is tough, thin-leafed and easy to use.

Claims (2)

[Claims] The present invention comprises a metaphenylene isophthalamide polymer, has a large number of uniform micropores on the surface and inside, has a porosity of 40 to 90%, and a surface porosity of 10 to 70.
% Of the heat-resistant cleaning sheet, comprising a porous membrane having a percentage of 100%. 2. The heat-resistant sheet for cleaning according to claim 1, wherein the sheet comprises a porous film having a surface having an average pore diameter of 0.5 to 20 μm and a thickness of 1 to 200 μm.