JP5013333B2 - Production method of graft-polymerized functional nonwoven fabric - Google Patents

Description

  The present invention relates to a method for producing a graft-polymerized functional nonwoven fabric, and more specifically, after a polymer material nonwoven fabric composed of ultrafine fibers is irradiated with gamma rays, a functional functional group is introduced by emulsion graft polymerization, and harmful metal components and The present invention relates to a method for producing a functional nonwoven fabric used for a filter or the like that adsorbs harmful gases. The “function (sex)” here refers to a function related to filter performance such as adsorption removal of metal ions contained in a liquid and adsorption removal of harmful gases required for air cleaning by an ion exchange function.

In graft polymerization of a polymer base material having air permeability such as a non-woven fabric, most conventional techniques are carried out by electron beam irradiation (for example, see Patent Documents 1 to 4). The main reason is that the irradiation rate is much higher than that of gamma rays (approximately 10 kGy / Sec level) and the electron beam is easily shielded. Because.
On the other hand, in gamma ray irradiation, the irradiation dose rate is low (approximately 10 kGy / Hr level), and high dose irradiation of 30 kGy to 200 kGy found in the prior art requires 3 to 24 hours, which is not economical. Furthermore, since high-level shielding management is required, it has not been used for a long time because it is not easy to incorporate irradiation of a nonwoven fabric as a long continuous base material into a continuous polymerization equipment in a graft polymerization processing equipment.

Due to the above background, electron beam irradiation is applied to graft polymerization of nonwoven fabrics, but there are also limitations. The first restriction is that the transmission power of electron beams is weak, so the raw material (nonwoven fabric base material) wound in a roll must be unfolded and irradiated into a sheet, and this causes tension on the irradiation device. A feed and take-up device for the raw material with control is required.
The second constraint is likely to be accompanied by a decrease in strength, fiber dropping, etc. due to polymer degradation caused by irradiation. Therefore, as a fiber material, fiber / nonwoven fabric base materials such as polypropylene and polyamide, which are susceptible to polymer degradation, have been conventionally unsuitable for this application. It has been limited to non-woven fabrics.
In addition, as a third restriction, it is necessary to configure the nonwoven fabric with relatively thick fibers in consideration of strength reduction due to irradiation of the nonwoven fabric fibers. For example, long fibers of polyethylene, polyethylene / polyester core, and composite fibers are melt-spun and drawn, and then cut into 40-50 mm staple fibers (Note: Sometimes referred to as single fibers; hereinafter referred to as short fibers). Then, this is made into a sheet by a card machine, and the fibers are fixed to a hot press roll (also called a calender roll) process in which needle punching or smooth or pin-like embossing is laid, and it is made into a non-woven fabric. Therefore, a fineness of 2 to 6 dtex (corresponding to a fiber diameter of about 18 to 30 μm depending on the specific gravity of the material) has been used.
In graft polymerization to such a fiber having a large fiber diameter, it is necessary to generate radicals up to the deep part of the fiber in order to increase the grafting ratio. Therefore, the required dose of radiation is increased and the graft reaction time is also increased. It is a long time unit. This is the same even when the radiation is not only an electron beam but also a gamma ray.

In addition, the reactive monomer to be grafted is conventionally used in a monomer stock solution or in a mixed state with an organic solvent such as alcohol dimethyl sulfoxide, but the use of the organic solvent has a large environmental load, It also led to increased costs for operational safety measures and disposal. In this respect, for example, the emulsion graft polymerization method disclosed in Patent Document 4 is advantageous because it uses a reactive (polymerizable) monomer emulsified with water and a surfactant and does not use an organic solvent such as alcohol. is there.
However, in the emulsion graft polymerization method disclosed in Patent Document 4, although it is possible to reduce the radiation dose, the short (single) fiber having a thickness of several decitex as described above is used. When the dose is lowered, there are disadvantages that a sufficient graft rate cannot be achieved and the reaction time becomes longer.

  In addition, many of the production methods and apparatuses found in the prior art have made the electron beam irradiation process and the monomer grafting process continuous to improve the production speed. A tank is required, and it must be a heavy and long device. For example, the traveling speed under electron beam irradiation is practically considered to be about 5 m / min to 20 m / min, but the polymerization reaction tank connected thereto has a long reaction time in liquid, and thus, for example, is found in the prior art. Thus, if it takes 1-2 hours, a reaction tank having a running length of several tens to hundreds of meters is required. Such a continuous method requires a non-woven fabric that can withstand a long run, or requires precise tension control, which requires an excessive investment burden for both facilities and locations that can achieve this, so it is a business for mass production. Therefore, it is not suitable for production of various functional graft nonwoven fabrics.

As described above, in the conventional technology, there are a number of restrictions in terms of equipment, material, fiber diameter, and environment. However, in various fields such as recent semiconductors, liquid crystals, biotechnology, medicine, etc., various ion removal performance, chemical resistance, heat resistance, service life, liquid permeability (ventilation), low, etc. The level of dustiness and other requirements has become much more sophisticated and diversified. Conventional single-layer nonwoven fabrics and graft polymerization methods are difficult to meet these requirements, and they are multifunctional with a wide variety of non-woven fabrics. In addition, it is becoming a situation that requires an efficient graft polymerization method.
In the present invention, the “sufficient graft ratio” varies depending on the use, but is preferably about 100% (graft on the base material) from the relationship between the functional group capacity (= use life) performance, cost, and productivity. The monomer is expressed by weight ratio) as a preferable standard for practical use.
Japanese Patent Laid-Open No. 11-279945 Japanese Patent No. 3787596 Japanese Patent No. 3293301 JP 2005-344047 A

In view of the above-mentioned problems of the prior art, the object of the present invention is to study the graft polymerization method of nonwoven fabric using gamma ray irradiation instead of electron beam irradiation, and to use it suitably for liquid filtration filters and air filter applications. An object of the present invention is to provide a method for producing a high-performance functional nonwoven fabric obtained by graft polymerization of various materials.
In particular, the object of the present invention is (i) that a sufficiently high graft rate can be obtained even when the irradiation dose of gamma rays is lowered, and that a high degree of ion exchange capacity can be provided, and (ii) low dustiness composed of continuous fibers. A non-woven fabric (melt blown non-woven fabric) is used as a base material, and the range of application to polyethylene and other polymer materials can be expanded. (Iii) Various grafting conditions can be easily adjusted, and functional non-woven fabrics that can remove various ions. In order to provide a wide variety of products, we are considering the production of functional nonwoven fabrics consisting of discontinuous processes. In recent years, liquid filtration filters and deodorizing filters, housing, automobile interior materials, and construction, which are becoming increasingly demanding and specialized. It is providing the manufacturing method of a functional nonwoven fabric which can be used suitably for materials, a deodorant sheet material, etc.

  As a result of intensive studies to solve the above problems, the present inventors have focused on melt blown nonwoven fabric among (i) a number of nonwoven fabric manufacturing methods, and are composed of ultrafine continuous fibers in this nonwoven fabric production. When producing a non-woven fabric, the specification of the non-woven fabric base material is selected so that the fiber configuration (fiber diameter, basis weight, fiber filling rate, etc.) suitable for graft polymerization is obtained, and (ii) graft polymerization is performed. By combining the two means of emulsifying the reactive monomer with water and a surfactant, a graft rate exceeding the target can be obtained with a low radiation dose and a short reaction time upon irradiation with gamma rays. I found out that I can do it. With these findings, it is possible to reduce the time of gamma ray irradiation, overcome the problem of low irradiation rate of the gamma ray device, and further suppress the molecular deterioration of the nonwoven fabric substrate by lowering the irradiation dose. Can be graft polymerized to an ultrafine nonwoven fabric made of polyamide or polypropylene which has not been applied, and the present invention has been completed.

That is, according to the first aspect of the present invention, (I) a fiber filling rate of 5 to 45% composed of continuous fibers having a mean fiber diameter of 0.2 to 10 μm made of polyamide or polyolefin as a raw material, and a basis weight of 10 A first step of placing a melt blown nonwoven fabric of ˜100 g / m ² in a sealed state cut off from a nitrogen atmosphere and an atmosphere below freezing, and irradiating the nonwoven fabric with gamma rays of 5 to 30 kGy , and then (II) the atmosphere A second step of graft polymerization in a liquid phase by immersion in a liquid tank of an emulsified vinyl group-containing reactive monomer under a nitrogen atmosphere or under reduced pressure, and (III) a grafted vinyl group-containing monomer The function further comprising a third step for introducing a functional functional group into the chain, and each of the first to third steps being an independent and non-continuous step. Method for producing a nonwoven fabric is provided.

According to a second invention of the present invention, in the first invention, the nonwoven fabric as the graft polymerization base material is made of polyamide, polypropylene, a copolymer of propylene and ethylene, polyethylene, or ethylene. Provided is a method for producing a functional nonwoven fabric, which is a kind selected from copolymers with other α-olefins having 4 or more carbon atoms.
Furthermore, according to a third invention of the present invention, in the first or second invention, the functional functional group is at least selected from a sulfone group, an amino group, a phosphate group, a glucamic acid group, or an iminodiacetic acid group. A method for producing a functional nonwoven fabric is provided.

As described above, the present invention relates to a method for producing a functional nonwoven fabric, and preferred embodiments thereof include the following.
(1) The emulsification is carried out using water and a surfactant as the reactive monomer, and the surfactant used at that time is an anionic surfactant, a cationic surfactant, or an amphoteric ion system. The method for producing any one of the above functional nonwoven fabrics, which is any one of a surfactant, a nonionic surfactant, or a mixture thereof.
(2) The reactive monomer is a monomer having a vinyl group selected from the group consisting of acrylonitrile, glycidyl methacrylate, vinylbenzyl glycidyl ether, and chloromethylstyrene. Production method.

  In addition, as a preferable usage mode of the functional nonwoven fabric obtained from the method for producing the functional nonwoven fabric of the present invention, the above-described functional nonwoven fabric is laminated alone or with another type of nonwoven fabric to form a pleated or cylindrically wound cartridge. It can be. Furthermore, it is possible to provide a cartridge filter for fluid filtration formed by combining the above functional nonwoven fabric and a microporous membrane of high-density polyethylene or PTFE and laminating them into a pleat or a cylindrical shape to form a cartridge. In addition, a gas adsorption type air filter can be provided in combination with another type of non-woven fabric or net.

According to the method for producing a functional nonwoven fabric of the present invention, a nonwoven fabric having a fiber filling rate of 5 to 45% composed of continuous fibers having an average fiber diameter of 0.2 to 10 μm is used, and emulsified with water and a surfactant. By using the reactive monomer, it is possible to provide a method in which the radiation dose of gamma rays is low and a high graft ratio can be obtained in a reaction time much shorter than that of the conventional method. In addition, a way to use gamma ray irradiation with a low irradiation rate, which has been avoided in the past, has been paved, and it is industrially outstanding.
In addition, roll-wrapped non-woven fabric is sealed in a packaging material such as a gas barrier resin film bag as it is, and after degassing and nitrogen replacement, it is sealed with a heat sealer and stored frozen. Batch irradiation processing with strong penetrating gamma rays can be performed in the packaged form. Such a packaging form removes the heat generated at the time of gamma irradiation, and also has a function of cutting off contact with oxygen at a low temperature even after irradiation. It is extremely effective for graft polymerization based on gamma ray irradiation.
Furthermore, according to the present invention, a reactive monomer emulsified with water and a surfactant is grafted and used for polymerization, and an alcohol such as methanol or an organic solvent such as dimethyl sulfoxide is not used. Safety is high and environmental impact can be reduced.

The method for producing a functional nonwoven fabric of the present invention comprises (I) a nonwoven fabric having a fiber filling rate of 5 to 45% composed of continuous fibers having an average fiber diameter of 0.2 to 10 μm made of polyamide or polyolefin as a raw material. A first step of irradiating the nonwoven fabric with gamma rays of 30 kGy or less, in a sealed state isolated from the atmosphere and the atmosphere below freezing point, and then (II) emulsified in the atmosphere or in a nitrogen atmosphere or under reduced pressure. A second step of immersing the polymer in a vinyl group-containing reactive monomer and graft-polymerizing it in a liquid phase; and (III) a step of further introducing a functional functional group into the grafted vinyl group-containing monomer chain. It consists of three processes, and each of the first to third processes consists of independent and non-continuous processes.
Hereafter, the manufacturing method of the functional nonwoven fabric of this invention, etc. are demonstrated in detail.

I. First step:
As a nonwoven fabric used as the base material according to the present invention, the base fiber selected from polyamide or polyolefin is made of continuous fibers having an average fiber diameter of 0.2 to 10 μm, and the fiber filling rate is preferably 5 to 45%. Is selected from non-woven fabrics manufactured by the melt blow method.
Here, the melt blown non-woven fabric is a sheet-like non-woven fabric composed of ultra-fine continuous fibers that melt a thermoplastic polymer (polymer), extrude it from an ultra-fine nozzle, blow off with high-temperature and high-pressure air, and accumulate on a screen conveyor. . This sheet-like nonwoven fabric is a nonwoven fabric produced from a series of continuous processes provided for this application by winding the sheet-like nonwoven fabric in an arbitrary length.

Although the ultrathinning by this melt blown nonwoven fabric varies depending on the type of raw material applied, the average fiber diameter of the melt blown nonwoven fabric that can be produced industrially is in the range of 0.2 to 15 μm. 0.2 to 10 μm. This fiber diameter is a much smaller fiber diameter than that of the conventional short fiber nonwoven fabric. This means an increase in the number of fibers per unit nonwoven fabric weight, that is, the surface area (specific surface area), and also increases the surface of the base material in the graft polymerization reaction, which is a factor for decisively increasing the graft ratio.
Further, not only the fiber diameter but also the filling density of fibers within a certain volume of the nonwoven fabric, that is, the fiber filling rate (sometimes referred to simply as “filling rate%”) can be easily adjusted in the course of manufacturing the original fabric. This fiber filling rate is an important factor that affects the graft rate in relation to the porosity in the nonwoven fabric. In the present invention, the fiber filling rate is 5 to 45% (the porosity is 95 to 55%). It is preferable.
Although a spunbond nonwoven fabric can be used as the continuous fiber nonwoven fabric, it is difficult to realize a fiber diameter of 10 μm or less in the current industrial production, and it is omitted from the subject of the present invention.

  Here, a mechanism that is advantageous for graft polymerization when the fiber diameter is small will be discussed and described in detail. First, when the fiber diameter is reduced, the surface area (specific surface area) per certain weight of the nonwoven fabric substrate increases. Since the graft polymerization of reactive monomers grows from the fiber surface, it is not necessary to penetrate radical generation and graft polymerization by radiation deep into the fiber, and even if the graft ratio of individual fibers is low, the absolute number of fibers Therefore, a high graft ratio as a whole substrate can be obtained by the integration. For this reason, it can be inferred that the radiation dose can be reduced and the graft polymerization time can be shortened.

In the present invention, since the low irradiation dose based on the use of ultrafine fibers is realized, the specific surface area is large with respect to the unit weight, so that generation of radicals in the deep fiber and penetration of graft polymerization are not necessary. Can be considered.
As a result, since damage to the base material can be reduced, the applicable polymer material spreads, and besides polyethylene (PE), polyamide (PA), polypropylene (PP), etc. with molecular weight collapse due to irradiation, A wide range of melt blown nonwoven materials can be used.
In particular, for melt blown nonwoven fabrics made of very fine polypropylene, irradiation of 10 kGy or less is sufficient for graft polymerization, and for the same material, a dose of 5 to 10 kGy is a preferable dose for reducing damage.

  Here, the polyamide (PA) is not particularly limited, and is a synthetic polymer having a general name of nylon having acid amide (—CONH—) as a repeating unit. For example, polyamide 3 (nylon 3), polyamide 4 (nylon 4), polyamide 6 (nylon 6), polyamide 6-6 (nylon 6-6), polyamide 12 (nylon 12) and the like.

As the polyolefin, homopolymers of α-olefins such as propylene, ethylene, butene-1, hexene-1, octene-1, 4-methylpentene-1, or two or more kinds of these α-olefins are random or A block copolymer is mentioned. Among them, polypropylene (PP) is a polypropylene homopolymer or an ethylene / propylene copolymer, and its ethylene content is not particularly specified, but those produced with a metallocene catalyst are deteriorated in physical properties due to radiation damage. Is preferable.
In addition, the polyethylene (PE) is not particularly limited, and any of high density polyethylene, medium density polyethylene, low density polyethylene, ethylene-vinyl acetate copolymer and the like can be made into a nonwoven fabric by melt blowing, and the fiber diameter Those having a thickness of 10 μm or less are suitable for use.

Furthermore, in the manufacturing method of the functional nonwoven fabric of this invention, it is desirable that the fabric weight of a nonwoven fabric is selected from the range of 10-100 g / m < ² > with the range of the above-mentioned average fiber diameter and fiber filling rate.
The fiber filling rate (corresponding to the amount of fibers occupying in the unit volume) is expressed by the following equation, and the porosity (void occupying in the unit volume) has the following relationship.
Filling rate (%) = {weight per unit weight g / m ² / thickness mm / specific gravity / 1,000} × 100 (%)
Porosity (%) = 100−Fiber filling rate (%)

Here, in the present invention, the fiber diameter is dominant with respect to the graft ratio and the graft reaction time, while the basis weight of the nonwoven fabric is proportional to the absolute amount of the number of fibers to be graft-polymerized, and thus affects the graft amount. . Further, the porosity (or fiber filling rate) gives the density and free space (void) of the fibers where the graft chain grows, and thus affects the graft rate to be achieved. If the porosity is too small, that is, if the fiber filling rate is too large, the fibers will be densely arranged in a certain volume, so that the reactive monomer cannot freely penetrate into the nonwoven fabric, and when the reaction proceeds, Becomes a liquid dripping state, which is not preferable. On the other hand, if the porosity is too large, that is, if the fiber filling rate is too small, melt-blown nonwoven fabrics are likely to be fuzzy and have reduced strength, which is not preferable. Therefore, as a base material for graft applications, the fiber filling rate is preferably in the range of 5 to 45%, more preferably in the range of 10 to 40%.
The fiber structure of such a nonwoven fabric is extremely important because it dominates the graft ratio, and it is difficult to achieve good graft polymerization with only a factor of the fiber diameter. In this respect, the melt blown nonwoven fabric is preferable because the fiber structure suitable for the graft polymerization according to the present invention can be controlled relatively freely.

In the present invention, as an example of such an embodiment, a non-woven fabric wound in a roll shape is sealed in a packaging material such as a gas barrier resin film bag using a high gamma ray permeability, and after deaeration and nitrogen replacement operation By batch sealing with a heat sealer and freezing with dry ice or the like, it is possible to perform batch irradiation treatment with gamma rays having strong penetrating power in the form of bulk packaging. This type of packaging removes the heat generated during gamma irradiation and, after irradiation, cuts off contact with oxygen at low temperatures, thus preventing the disappearance of the generated radicals over a long period of time. Therefore, it is extremely effective for graft polymerization based on gamma ray irradiation in the present invention.
In addition, you may use the container by which the state after irradiation of a gamma ray and irradiation is kept in a deaeration sealed state and a frozen state, and it does not stick to the packaging form of the said film bag.

As the packaging material, it is desirable to have a property of blocking oxygen in the air, and as a film material, a multilayer gas barrier property such as polyethylene / nylon / polyethylene three-layer film or polyethylene / EVOH (Eval) / polyethylene is used. The film is suitable. Packaging in such a film bag does not require special labor if a commercially available automatic mechanization apparatus is used. For example, a vacuum degassing and nitrogen filling packaging machine frequently used in the food packaging field can be used.
Since the roll-shaped nonwoven fabric raw material packed in this way is stored in a heat insulating box together with dry ice and irradiated as it is, it is unnecessary to unwind the nonwoven fabric base material and bring the winding equipment into the irradiation equipment.
The non-woven fabric packed as described above is irradiated with gamma rays while being kept cold, and then stored in a frozen state, and then transferred to the graft polymerization step (II) as the next step.

II. Second step:
In the second step of the method for producing the functional nonwoven fabric of the present invention, the non-woven fabric irradiated with gamma rays under the above-mentioned nitrogen atmosphere and kept cold is subjected to emulsified vinyl group-containing reactivity under the atmosphere, nitrogen atmosphere or reduced pressure. This is a step of immersing in a monomer tank and graft polymerizing in a liquid phase.
Specifically, the unpacked nonwoven fabric after gamma irradiation is unpacked and immediately put into a tank of vinyl group-containing reactive monomer emulsified with water and a surfactant, and graft polymerization is conducted in the liquid phase. Complete.

In the present invention, by reacting the vinyl group-containing reactive monomer with water and a surfactant, the reaction in the first step can be performed in a low radiation dose and in a short time.
This is presumably due to the effect of the ultrafine fibers and the fine emulsion monomer droplets being efficiently associated and promoting the reaction. The monomer droplet itself associated with the fiber is considered to have a concentration of about 100%, which can be considered as an increase in graft reactivity. Even if the irradiation amount of gamma rays is low, a sufficient grafting rate can be obtained in a short reaction time. Further, since this is a polymerization reaction in an emulsion liquid, the inside of the tank is filled with a nitrogen atmosphere. A sufficient graft ratio can be achieved by performing nitrogen bubbling on the emulsion before and after the start of the reaction.

As the surfactant for emulsifying the reactive monomer for graft polymerization, any of anionic, cationic, zwitterionic and nonionic surfactants can be used. Moreover, you may use these several types together.
Specifically, the anionic surfactant is not particularly limited, and examples thereof include alkylbenzene-based, alcohol-based, olefin-based, phosphoric acid-based, and amide-based surfactants. Examples thereof include sodium dodecyl sulfate. It is done.
Further, the cationic surfactant is not particularly limited, and examples thereof include octadecylamine acetate and trimethylammonium chloride. The nonionic surfactant is not particularly limited, and examples thereof include ethoxylated fatty alcohol and fatty acid ester, and examples thereof include Tween 80. The zwitterionic surfactant is not particularly limited, and examples thereof include Amphital (trademark) (Kao Corporation).
The concentration of the surfactant to be used is not particularly limited and can be appropriately determined depending on the type and concentration of the reactive monomer. The concentration of the surfactant is preferably 0.1 to 10% based on the total weight of the solvent.
By using the surfactant, it is possible to promote the dispersion of the reactive monomer insoluble in water. The appearance of the emulsion varies depending on the size of the droplets in the dispersed phase, but is generally in an emulsion state, and as the droplet size decreases from microemulsion to nanoemulsion, It becomes transparent.

The water for emulsification is not particularly limited, but ion exchange water, pure water, and ultrapure water are used. By using water instead of an organic solvent as a solvent, problems of waste liquid treatment and working environment can be eliminated, which contributes to environmental protection.
Here, the graft polymerization conditions of the above-mentioned emulsifying monomer are 40 ° C. to 60 ° C., although depending on the reactivity of the monomer. The reaction time ranges from 5 minutes to 40 minutes, and the monomer concentration in the emulsion is appropriately selected from 5 to 30%.

In the present invention, the first step (irradiation) and the second step (graft polymerization) can be considered as continuous steps in terms of shortening the time between steps, but particularly for gamma ray irradiation equipment. Incorporation of such a graft polymerization tank is not preferable in terms of ensuring safe operation and enormous capital investment. Therefore, it is preferable that both processes be discontinuous independent processes.
Further, according to the present invention, it is desirable that the graft substrate is subjected to a cold storage treatment in a nitrogen atmosphere after irradiation. Since the irradiation process (first process) and the graft polymerization process (second process) are separated, the irradiation amount and the graft reaction time in the batch tank of the reactive monomer are changed independently according to the application and purpose. Since it can, it is convenient for the production of a small variety of products. Further, the fact that the first process and the second process are separated and independent gives further freedom in the operation location form. For example, the irradiation can be outsourced to an external contractor, and expensive gamma-ray irradiation devices and electron beam devices and the accompanying buildings, shields, qualified personnel, etc. are not necessary.

In the present specification, “emulsion” generally refers to a system in which droplets of a reactive monomer liquid that is insoluble in water are dispersed in an aqueous solvent. The size of the droplets of the reactive monomer liquid is not limited, and includes a microemulsion of about several nm to several tens of nm and a nanoemulsion of about 1 nm. Therefore, as long as there is a reactive monomer solution and an aqueous solvent that are insoluble in water, the addition of a surfactant reduces the interfacial tension between water / oil and makes it appear to be uniformly mixed. The system is also included.
The present invention includes introducing functional functional groups such as a sulfone group, an amino group, and an iminodiacetic acid group into the graft chain of the monomer formed on the base material through the second step and the third step. It is a waste.

The reactive monomer to be graft-polymerized on the nonwoven fabric substrate includes a monomer having a vinyl group, and is not particularly limited. For example, acrylonitrile (CH ₂ = CHCN), acrolein, glycidyl methacrylate (GMA), vinyl benzyl Examples thereof include glycidyl ether and chloromethylstyrene.
Examples of the monomer having a vinyl group in the reactive monomer also include a vinyl monomer having a phosphate group. For example, mono (2-methacryloyloxyethyl) acid phosphate: CH ₂ = C (CH ₃ ) COO (CH ₂ ) ₂ OPO (OH) ₂ , di (2-methacryloyloxyethyl) acid phosphate: [CH ₂ ═C (CH ₃ ) COO (CH ₂ ) ₂ O] ₂ PO (OH), mono (2-acryloyloxyethyl) acid _{phosphate: CH 2 = CHCOO (CH 2} ) 2 OPO (OH) 2, di (2-acryloyloxyethyl) acid _{phosphate: [CH 2 = CHCOO (CH} 2) 2 O] 2 PO (OH), or a mixture thereof Monomers and the like.

This vinyl group-containing monomer, such as GMA, is grafted onto a base material, and then, as a third step, a functional group having an ion exchange function is introduced into the graft side chain, for example, a sulfonating agent such as sodium sulfite Can be converted into a cation exchange group, or can be aminated with diethanolamine to introduce an anion exchange group. In addition, an iminodiacetic acid group (iminodiacetic acid group, (IDA group: —N (CH ₂ COOH) ₂ ) can be introduced into the graft chain by acting a chelating agent such as iminodiacetic acid.

In the present invention, in the second step, as the reactive monomer introduced into the substrate selected as described above, a monomer having ion exchange itself may be used.
For example, copolymerization in aqueous solution with acrylic acid and sodium styrene sulfonate, sodium methacryl sulfonate, sodium allyl sulfonate, t-butyl acrylamide sulfonic acid, etc. containing strong acidic groups, Examples thereof include vinylbenzyltrimethylammonium chloride, dimethylacrylamide, diethylaminoethyl methacrylate, and dimethylaminopropylacrylamide. Such copolymerization is an embodiment in which the second step and the third step are integrated.

III. Third step:
In the third step of the method for producing a functional nonwoven fabric of the present invention, the above-mentioned vinyl group-containing reactive monomer is graft-polymerized in the liquid phase, that is, the grafted vinyl group-containing monomer chain further functions. This is a step of introducing a functional functional group.
Specifically, a monomer having a vinyl group, such as GMA, is grafted onto a nonwoven fabric substrate, and then, in a third step, a functional group having an ion exchange function is introduced into the graft side chain, for example, sodium sulfite. Is a step of reacting a sulfonating agent such as sulfonate and converting it to a cation exchange group, or amination using diethanolamine or the like to introduce an anion exchange group. In addition, an iminodiacetic acid group can be introduced into the graft chain by acting a chelating agent such as iminodiacetic acid, and a function of adsorbing heavy metals such as lead can be imparted.
Moreover, as a functional functional group introduce | transduced in a 3rd process, at least 1 type chosen from a sulfone group, an amino group, a phosphoric acid group, a glucamic acid group, or an iminodiacetic acid group is mentioned. However, other than these, there are amidoxime group, phosphoric acid group, carboxylic acid group, ethylenediaminetriacetic acid group, iminodiethanol group and the like depending on the desired function, for example, the adsorption function of heavy metals (lead, cadmium, arsenic, etc.).

IV. Use of functional nonwoven fabric The functional nonwoven fabric obtained by the method for producing a functional nonwoven fabric of the present invention can be processed into various filters, for example, first applied to the field of adsorbing and recovering metal ions dissolved in a fluid. it can. For example, various metal ions, copper, sodium, etc. contained in pure water used in semiconductor manufacturing can be adsorbed by sulfone groups, and lead, cadmium, etc. contained in drinking water, waste liquid are captured by iminodiacetic acid groups. can do.
Further, when the fluid is a gas, acidic or alkaline gas contained in the gas can be efficiently adsorbed by converting the ion exchange group into a sulfone group or an amino group.
As an example of removing harmful components contained in the gas, alkali gases such as ammonia and trimethylamine, acidic gases such as NO ₃ and SO ₃ , acetaldehyde, formaldehyde and the like can be adsorbed.

The functional nonwoven fabric filter using the functional nonwoven fabric according to the present invention for a filter application, when used as a filter material for gas and liquid, to reduce the pressure loss, the filter material is formed into a pleated shape, Since the filter is often formed, it can be formed and used in a pleated or cylindrical shape also in the present invention.
Moreover, it can also be used as a cartridge filter for fluid filtration formed by combining the functional nonwoven fabric filter according to the present invention and a microporous membrane of high-density polyethylene or PTFE and laminating them into a pleat or a cylindrical shape.
As described above, the grafted nonwoven substrate is subjected to many mechanical and thermal processes, but the reduction in physical properties of the substrate can be suppressed by reducing the radiation dose in the present invention. It is suitable for.

  EXAMPLES The present invention will be specifically described below with reference to examples. However, the present invention is not limited to only these examples.

[Example 1]
A melt blown non-woven fabric of high-density polyethylene material having an average fiber diameter of 6 μm (abbreviated as MB in Table 1, basis weight 81 g / m ² , thickness 0,38 mm, fiber filling rate 24%) in a roll shape with a width of 30 cm and a winding diameter of 20 cm It was rolled up, placed in a polyethylene / nylon / polyethylene three-layer gas barrier film bag, degassed with a vacuum pump, nitrogen was introduced, and the bag was heat sealed and sealed. This sample was stored together with dry ice in a polystyrene foam box.
This sample was irradiated with 20 kGy of gamma rays (first step).

Next, the irradiated sample was immersed in a pre-prepared emulsion monomer storage tank, and an emulsion graft polymerization reaction was performed for 20 minutes while maintaining the temperature at 40 ° C. under reduced pressure. The monomer solution was previously bubbled with nitrogen (second step).
The monomer solution used is an emulsion of 10% glycidyl methacrylate (GMA) and pure water containing 1% surfactant Tween 80 (manufactured by Kanto Chemical Co., Ltd.) based on the total weight of the solution. When the graft ratio at this time was evaluated, the GMA graft ratio was 150%.
Here, the graft ratio was calculated from the weight of the nonwoven fabric before and after grafting based on the following formula.
Graft rate (%) = 100 × (BA) / A
(In the formula, A represents the nonwoven fabric substrate weight before grafting, and B represents the nonwoven fabric substrate weight after grafting.)

As a third step, this grafted non-woven fabric was reacted with a 10% aqueous sodium sulfite solution at 80 ° C. for 2 hours to give an ion exchange group, thereby introducing a sulfone group.
As the sulfone conversion rate (%) shown in Formula (1), the ratio of the number of moles of the sulfone group converted from the epoxy group to the number of moles of the epoxy group before being converted into the sulfone group was calculated. The result was 90% as shown in Table 1.
Formula (1): Conversion rate (%) = 100 × mol number of sulfone group converted from epoxy group / mol number of epoxy group before being converted to sulfone group

The functional group density of the base fabric unit weight can be calculated from the weight of the nonwoven fabric base fabric and the number of moles of the introduced functional group. The calculation method is exemplified below, and the results are shown in Table 1.
Functional group density (m-mol / g) = number of moles of introduced functional group [m-mol] / weight of functional nonwoven fabric [g]
The above-described functional nonwoven fabric refers to a nonwoven fabric after the introduction of a functional group.

[Example 2]
Graft polymerization was carried out in the same manner as in Example 1 except that the nitrogen-substituted emulsion monomer solution of Example 1 was immersed in the emulsified monomer solution without nitrogen bubbling. The GMA graft ratio was 110%.
As a third step, a 10% aqueous solution of trimethylamine hydrochloride is prepared on the grafted nonwoven fabric, and NaOH is added to the aqueous solution to obtain a pH of 9.4. When the treatment was performed for a time, a trimethylamine-added functional nonwoven fabric having a conversion rate of 95% was obtained. Table 1 shows the evaluation results and the functional group density obtained from the calculation by the method shown in Example 1 above.

[Example 3]
The emulsion graft polymerization reaction was carried out in the same manner as in Example 1 except that a melt blown nonwoven fabric (weight per unit weight 80 g / m ² , thickness 0.56 mm, fiber filling rate 16%) of a high-density polyethylene material having an average fiber diameter of 9 μm was used. Carried out. The GMA graft ratio was 105%.
As a third step, the grafted nonwoven fabric was immersed in a 10% aqueous solution of sodium iminodiacetate at 80 ° C. for 3 hours to obtain an iminodiacetic acid group-added functional nonwoven fabric having a conversion rate of 85%. The functional group density obtained from the evaluation result and calculation is shown in Table 1.

[Example 4]
Example 1 except that a melt-blown non-woven polypropylene material having an average fiber diameter of 0.6 μm (weight per unit area 15 g / m ² , thickness 0.12 mm, fiber filling rate 14%) and gamma ray irradiation dose of 10 kGy was used. Next, an emulsion graft polymerization reaction was carried out. The GMA graft ratio was 170%.
As a third step, 10% of glucamic acid was dissolved in a 90:10 dioxane and water solution and immersed in the grafted nonwoven fabric at 80 ° C. for 30 minutes. As a result, a functional nonwoven fabric of glucamic acid group addition type having a conversion rate of 100% was obtained. The functional group density obtained from the result and calculation is shown in Table 1.

[Example 5]
Except using melt blown non-woven fabric (weight per unit weight 60 g / m ² , thickness 0.50 mm, fiber filling rate 13%) made of polyamide 6 (PA6) with an average fiber diameter of 6 μm, and gamma irradiation dose of 10 kGy As in Example 1, an emulsion graft polymerization reaction was performed. The GMA graft ratio was 190%.
As a third step, the grafted nonwoven fabric was immersed in a 10% aqueous solution of sodium iminodiacetate at 80 ° C. for 3 hours to obtain an iminodiacetic acid group-added functional nonwoven fabric having a conversion rate of 60%. Table 1 shows the functional group amounts obtained from the results and calculations.

[Example 6]
As a third step, the non-woven fabric added with 150% GMA by carrying out the emulsion graft polymerization reaction of Example 1 was immersed in 85% phosphoric acid and immersed at a temperature of 80 ° C. for 30 minutes. As a result, a phosphate group-added functional nonwoven fabric with a conversion rate of 100% was obtained. Table 1 shows the ion exchange equivalents obtained from the results and calculations.

[Comparative Example 1]
Emulsion graft polymerization reaction in the same manner as in Example 1 after irradiating 30 kGy of gamma rays onto a card-type dry nonwoven fabric (weight per unit weight 90 g / m ² ) using high-density polyethylene short fibers having a fineness of 2 dtex (average fiber diameter of 18 μm) (However, the reaction time was 60 minutes).
The GMA graft ratio was 32%. The results are shown in Table 2.

"Comparative Example 2"
Example 1 After irradiating 100 kGy of gamma rays to the card method dry nonwoven fabric (weight per unit weight 90 g / m ² ) using high-density polyethylene short fibers having a fineness of 2 dtex (average fiber diameter 18 μm) used in Comparative Example 1. In the same manner as above, an emulsion graft polymerization reaction (however, the reaction time was 60 minutes) was carried out, but the graft ratio of GMA remained at 75%. The results are shown in Table 2.

[Comparative Example 3]
Graft polymerization (with a reaction time of 60 minutes) was carried out under the same conditions as in Example 1 using a melt blown nonwoven fabric (weight per unit area: 50 g / m ² ) made of high density polyethylene having an average fiber diameter of 12 μm. However, the graft ratio of GMA was 29%. The results are shown in Table 2.

[Comparative Example 4]
The melt-blown nonwoven fabric (weight per unit weight 81 g / m ² , thickness 0.38 mm) made from high-density polyethylene with an average fiber diameter of 6 μm in Example 1 is compacted to 0.15 mm using a hot press roll and filled with fibers. The graft polymerization was carried out under the same conditions as in Example 1 with the rate adjusted to 50%, but the graft rate was 23%. The results are shown in Table 2.

[Comparative Example 5]
The melt blow method (weight per unit weight: 81 g / m ² ) using high density polyethylene having an average fiber diameter of 6 μm in Example 1 as a raw material was irradiated with 30 kGy of gamma rays, and then, as a second step, glycidyl methacrylate as a monomer solution Using a solution of 10% (GMA) and 90% methanol solvent, the reaction was performed for 120 minutes. As a result, the GMA graft ratio was 72%. The results are shown in Table 2.

As is clear from Tables 1 and 2, in Examples 1 to 6, the GMA grafting rate of 100% or more was achieved at a grafting reaction time of 20 minutes at a low irradiation dose of 20 kGy or less. .
On the other hand, in Comparative Example 1 using a dry card method nonwoven fabric using high-density polyethylene short fibers having a fiber diameter of 18 μm, the GMA graft ratio is 32% even when graft polymerization is performed. This is considered to be because the dose of gamma rays is low at 30 kGy. In Comparative Example 2, when the irradiation dose is increased to 100 kGy, the graft rate is improved. However, even when the reaction time is 60 minutes, the graft rate is 75%. Stays. In Comparative Example 3, even when graft polymerization was performed on a melt blown nonwoven fabric made from high-density polyethylene having a fiber diameter of 12 μm, the GMA graft ratio was as low as 29%. Here, the influence of the fiber diameter on the graft ratio is recognized.
Furthermore, in Comparative Example 4, the graft base fabric used in Example 1 was consolidated with a hot press roll and the thickness was reduced. As a result, the fiber filling rate was 50%. Graft polymerization of this nonwoven fabric base material was attempted in the same manner as in Example 1, but the GMA graft ratio reached only 23%. This means that as the fiber filling rate increases, the voids inside the nonwoven fabric decrease, and the penetration of monomers from the nonwoven fabric surface to the interior as the graft polymerization progresses, or the space where the GMA graft chain grows decreases. It is presumed that the cause was.
In Comparative Example 5, graft polymerization was carried out using the nonwoven fabric substrate of Example 1 and the graft monomer in a methanol solvent. However, even if the reaction time required 120 minutes, the graft ratio was 72%. There was a clear difference from Example 1 using the emulsified monomer.

  The functional nonwoven fabric obtained from the method for producing the functional nonwoven fabric of the present invention is suitable for a liquid filter that adsorbs and recovers metals, cations and anions dissolved in a liquid by introducing a functional functional group. It can be suitably used for an air filter that adsorbs and removes harmful gases contained in the atmosphere. Further, for example, it can be used for ultrapure water used in semiconductor and liquid crystal manufacturing processes, and arsenic and heavy metals can be adsorbed and removed, so that it can be used for purification of rivers and groundwater. Furthermore, it can also be used for an air filter that efficiently adsorbs and removes harmful gases contained in the atmosphere.

Claims (3)

(I) A melt blown nonwoven fabric having a fiber filling rate of 5 to 45% and a basis weight of 10 to 100 g / m ² made of continuous fibers having an average fiber diameter of 0.2 to 10 μm made of polyamide or polyolefin as a raw material, in a nitrogen atmosphere And a first step of irradiating the non-woven fabric with 5-30 kGy of gamma rays in a sealed state isolated from the freezing atmosphere and then
(II) a second step of graft polymerization in a liquid phase by immersion in a liquid tank of an emulsified vinyl group-containing reactive monomer under air, nitrogen atmosphere or reduced pressure, and (III) grafted Further comprising a third step of introducing a functional functional group into the vinyl group-containing monomer chain, and
1st-3rd each process consists of an independent discontinuous process, respectively, The manufacturing method of a functional nonwoven fabric characterized by the above-mentioned.   The nonwoven fabric as the base material for graft polymerization is a kind whose fiber raw material is selected from polyamide, polypropylene, a copolymer of propylene and ethylene, polyethylene, or a copolymer of ethylene and another α-olefin having 4 or more carbon atoms. The method for producing a functional nonwoven fabric according to claim 1, wherein:   3. The functional nonwoven fabric according to claim 1 or 2, wherein the functional functional group is at least one selected from a sulfone group, an amino group, a phosphoric acid group, a glucamic acid group, or an iminodiacetic acid group. Method.