A method for producing graft polymers.

Abstract

This invention provides a method for producing graft polymers that allows for a high grafting rate using a simple method. [Solution] The present invention provides a method for producing a graft polymer, comprising: step 1, contacting a substrate with a raw material containing a polymerizable monomer and a thickener to adhere the raw material to the substrate; and step 2, irradiating the substrate to which the raw material has been adhered with radiation to perform graft polymerization and obtain a graft polymer. According to the present invention's method for producing a graft polymer, the grafting rate can be increased by a simple method.

Description

Technical Field

[0001] The present invention relates to a method for producing a graft polymer.

Background Art

[0002] A technique (i.e., graft polymerization technique) for obtaining a graft polymer by forming a polymer compound on the surface of a substrate by graft-polymerizing a polymerizable monomer on the surface of the substrate is known.

[0003] For example, Patent Document 1 discloses a method for producing a grafted fiber (graft polymer) by sealing a fiber imparted with a radically polymerizable compound between polymer films, irradiating an electron beam from above the polymer films, and then performing heat polymerization.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in graft polymerization by radiation, particularly in graft polymerization by irradiating an electron beam, radicals derived from the substrate (fiber) generated by electron beam irradiation react with oxygen in the atmosphere prior to reacting with the monomer, which may cause a problem of a decrease in the graft polymerization rate. [[ID=4i]]

[0006] To suppress such a decrease in graft polymerization rate, it is essential to pre-purge the monomer with nitrogen, or to create a nitrogen atmosphere for polymerization. However, these processes tend to complicate the manufacturing process. Furthermore, even if the decrease in graft polymerization rate can be suppressed at the laboratory level by nitrogen purging, the results do not necessarily match those at the laboratory level when the equipment and facilities are scaled up for mass production, making nitrogen purging and similar treatments not necessarily the optimal method.

[0007] As disclosed in Patent Document 1 above, it is possible to seal fibers contaminated with a radical polymerizable compound between polymer films to block contact with oxygen during graft polymerization. However, even in this case, there was a problem in that steps such as sealing the polymer films and finally peeling off the polymer films were essential.

[0008] The present invention has been made in view of the above, and aims to provide a method for producing graft polymers that can increase the graft rate in a simple manner. [Means for solving the problem]

[0009] The inventors of this invention conducted extensive research to achieve the above objectives and, as a result, discovered that these objectives can be achieved by using raw materials containing polymerizable monomers and thickeners, thus completing the present invention.

[0010] In other words, the present invention encompasses, for example, the subject matter described in the following sections. Item 1 Step 1 involves contacting a substrate with a raw material containing polymerizable monomers and a thickening agent to adhere the raw material to the substrate, Step 2 involves irradiating a substrate to which the aforementioned raw materials are attached with radiation to perform graft polymerization and obtain a graft polymer. A method for producing graft polymers, comprising the following: Section 2 The method for producing a graft polymer according to item 1, wherein the radiation is an electron beam. Section 3 A method for producing a graft polymer according to item 1 or 2, wherein the substrate is a polymer substrate. Section 4 The method for producing a graft polymer according to claim 3, wherein the substrate is a fibrous substrate. Section 5 A method for producing a graft polymer according to any one of claims 1 to 4, wherein the thickening agent is a polymer-based thickening agent. [Effects of the Invention]

[0011] The present invention provides a method for producing graft polymers that allows for a high grafting rate using a simple method. [Modes for carrying out the invention]

[0012] Embodiments of the present invention will be described in detail below. In this specification, the expressions "containing" and "including" include the concepts of "containing," "including," "substantially consisting of," and "consisting only of."

[0013] The present invention provides a method for producing a graft polymer, comprising the following steps 1 and 2. Step 1: A step of adhering a raw material containing a polymerizable monomer and a thickener to a substrate by bringing the raw material into contact with the substrate. Step 2: A step of obtaining a graft polymer by irradiating a substrate to which the raw material is attached with radiation to perform graft polymerization.

[0014] The present invention provides a method for producing graft polymers that, by comprising steps 1 and 2 described above, can easily increase the grafting rate, that is, it can produce graft polymers with a high grafting rate. The graft polymerization method of the present invention may be abbreviated as "the method of production of the present invention" below.

[0015] The graft polymer obtained by the manufacturing method of the present invention is a polymer of polymerizable monomers grafted onto the surface of a substrate.

[0016] Project 1 Step 1 is a step for attaching a raw material containing a predetermined component to a base material.

[0017] (Base material) The type of the base material used in Step 1 is not particularly limited, and various base materials can be used. For example, the base materials that can be used in graft polymerization can also be widely used in the present invention.

[0018] Among them, the base material is preferably a polymer base material. That is, the base material used in Step 1 is preferably a base material formed of a polymer material. When such a base material is used, a polymer of a polymerizable monomer is easily grafted onto the surface of the base material.

[0019] Examples of the polymer base material include various base materials formed mainly of various polymer compounds. Examples of the polymer compound forming the base material include known general-purpose resins or engineering plastics.

[0020] Specifically, examples of the polymer base material include base materials formed of various resins such as polyolefin resins such as polyethylene and polypropylene; acrylic resins such as polymethyl methacrylate; styrene resins such as polystyrene; polyamide resins; celluloses; polyvinyl alcohol resins such as ethylene-vinyl alcohol copolymer (EVOH); fluorine resins such as polytetrafluoroethylene; polycarbonate resins; polyurethane resins; polyvinyl chloride resins; polyester resins; polyacrylonitrile; nylon resins; and the like.

[0021] Among them, in terms of being likely to have a high graft ratio, the polymer base material is preferably a polyolefin resin, a polyamide resin, an ethylene-vinyl alcohol copolymer, or a polyester resin, and more preferably a polyolefin resin.

[0022] From the viewpoint of high grafting rate and processability, the polymer substrate is preferably a fibrous substrate, but it may also be in various other shapes such as polymer films, polymer substrates, polymer thin films, and polymer sheets.

[0023] When the polymer base material is a fiber base material, the fiber base material can be a fiber base material formed from the various resins mentioned above (i.e., synthetic fibers), as well as natural fibers such as wool, silk, cotton, and linen, and semi-synthetic fibers such as rayon and cupro. In terms of easily increasing the grafting rate, polyolefin fibers, polyamide fibers, ethylene-vinyl acetate copolymer fibers, and polyester fibers are preferred as fiber base materials, with polyolefin fibers being more preferred. When the fiber base material is a synthetic fiber, it may be a blend of two or more polymer compounds.

[0024] The aforementioned fibrous base material may be a sheet-like material such as knitted fabrics, woven fabrics, and nonwoven fabrics, or it may be in any shape, such as yarn, hollow fiber, straw, or foam.

[0025] The raw materials used in step 1 contain polymerizable monomers and thickeners, as described above. The raw materials used in step 1 are usually in liquid form.

[0026] (polymerizable monomer) Polymerizable monomers can be broadly categorized into various polymerizable compounds that can be radically polymerized, with vinyl polymerizable monomers being particularly preferred.

[0027] Specific examples of vinyl polymerizable monomers include (meth)acrylic ester compounds, (meth)acrylamide compounds, (meth)acrylic acid, aromatic vinyl compounds, unsaturated nitrile compounds, ethylenically unsaturated ether compounds, salts of vinyl compounds, vinyl halogenated compounds, aliphatic conjugated diene compounds, and other vinyl compounds. Among these, (meth)acrylic ester compounds are preferred as polymerizable monomers.

[0028] In this specification, "(meth)acrylic" means "acrylic" or "methacrylic," "(meth)acrylate" means "acrylate" or "methacrylate," and "(meth)allyl" means "allyl" or "methallyl."

[0029] Examples of (meth)acrylic ester compounds include linear or branched alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, isobutyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, n-nonyl (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, etc.; cyclohexyl (meth)acrylate, 4-t-cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, phenoxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dimethylol tricyclodecanedi( Alicyclic (meth)acrylates such as meth)acrylate, tricyclodecanedimethanol di(meth)acrylate, or N-hydroxyphenyl(meth)acrylate; heterocyclic (meth)acrylates such as tetrahydrofurfuryl(meth)acrylate, 4-(meth)acryloyloxymethyl-2-methyl-2-ethyl-1,3-dioxolane, 4-(meth)acryloyloxymethyl-2-cyclohexyl-1,3-dioxolane, adamantyl(meth)acrylate, cyclic trimethylolpropaneformal(meth)acrylate, or glycidyl(meth)acrylate; hydroxyl group-containing (meth)acrylates such as 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, and 2-hydroxy-3-phenoxypropyl(meth)acrylate;Examples include linear or branched alkylene glycol (meth)acrylates such as tripropylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, 3-methyl-1,5-pentanediol di(meth)acrylate, 2-n-butyl-2-ethyl-1,3-propanediol di(meth)acrylate, pentaerythritol tri(meth)acrylate, or 2-(2-vinyloxyethoxy)ethyl (meth)acrylate; and fluoroalkyl group-containing (meth)acrylates such as 1H,1H,2H,2H-tridecafluorooctyl acrylate.

[0030] Examples of (meth)acrylamide compounds include (meth)acrylamide and N-substituted acry(meth)acrylamide. Examples of N-substituted acrylamides include N-alkyl(meth)acrylamide, with specific examples including N,N-dimethyl(meth)acrylamide, N,N-diethyl(meth)acrylamide, and N-isopropylacrylamide.

[0031] Aromatic vinyl compounds include styrene, α-methylstyrene, o-methylstyrene, p-methylstyrene, o-ethylstyrene, p-ethylstyrene, o-chlorostyrene, p-chlorostyrene, p-methoxystyrene, p-acetoxystyrene, α-vinylnaphthalene, and 2-vinylfluorene.

[0032] Examples of unsaturated nitrile compounds include acrylonitrile, α-chloroacrylonitrile, α-methoxyacrylonitrile, methacrylonitrile, and vinylidene cyanide.

[0033] Examples of ethylenically unsaturated ether compounds include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, methyl allyl ether, and ethyl allyl ether.

[0034] Examples of salts of vinyl compounds include sodium (meth)acrylate and sodium p-styrenesulfonate.

[0035] Examples of vinyl halogen compounds include vinyl chloride, vinylidene chloride, 1,2-dichloroethylene, vinyl bromide, vinylidene bromide, and 1,2-dibromoethylene.

[0036] Examples of aliphatic conjugated diene compounds include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, 2-neopentyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,2-dichloro-1,3-butadiene, 2,3-dichloro-1,3-butadiene, 2-bromo-1,3-butadiene, and 2-cyano-1,3-butadiene.

[0037] Other vinyl compounds include vinyl acetate, vinyl propionate, (meth)acrylic acid, methyl vinyl ether, or N-vinyl caprolactam.

[0038] Furthermore, the polymerizable monomer may include a water-soluble ethylenically unsaturated monomer containing phosphoric acid as an ionic group and a counterion. Examples of water-soluble ethylenically unsaturated monomers containing phosphoric acid as an ionic group and a counterion include mono(2-acryloyloxyethyl) acid phosphate, mono(2-methacryloyloxyethyl) acid phosphate, diphenyl(2-acryloyloxyethyl) phosphate, diphenyl(2-methacryloyloxyethyl) phosphate, phenyl(2-acryloyloxyethyl) phosphate, acid phosphooxyethyl methacrylate, methachloroyloxyethyl acid phosphate, phosphooxypolyoxyethylene glycol monomethacrylate, and acid... Examples include sodium, potassium, or ammonium salts of compounds having a phosphono group in their molecule, such as phosphooxypolyoxypropylene glycol methacrylate, (meth)acryloyloxyethyl acid phosphate, (meth)acryloyloxypropyl acid phosphate, (meth)acryloyloxy-2-hydroxypropyl acid phosphate, (meth)acryloyloxy-3-hydroxypropyl acid phosphate, (meth)acryloyloxy-3-chloro-2-hydroxypropyl acid phosphate, vinyl phosphate, or p-vinylbenzene phosphate.

[0039] The raw materials used in step 1 may include one or more polymerizable monomers.

[0040] (Thickening agent) The type of thickener included in the raw materials is not particularly limited, and for example, known thickeners can be widely used in the present invention. Preferably, the thickener is one or more polymeric thickeners selected from cellulose polymers, plant polymers, microbial polymers, animal polymers, starch polymers, alginic acid polymers, acrylic polymers, other polymeric thickeners, and inorganic water-soluble polymers, and among these, water-soluble polymeric thickeners can be more preferably exemplified.

[0041] Examples of cellulose-based polymers include methylcellulose, ethylcellulose, methylhydroxypropylcellulose, carboxymethylcellulose, hydroxyethylcellulose, hydroxymethylcellulose, hydroxypropylcellulose, nitrocellulose, sodium cellulose sulfate, sodium carboxymethylcellulose, crystalline cellulose, cationized cellulose, and cellulose powder.

[0042] Examples of plant-derived polymers include gum arabic, tragacanth, galactan, carob gum, guar gum, karaya gum, carrageenan, pectin, agar, quince seed, starch (rice, corn, potato, wheat, etc.), algae colloid, tranto gum, and locust bean gum.

[0043] Examples of animal-derived polymers include microbial polymers such as xanthan gum, dextran, succinoglucan, and pullulan, as well as collagen, casein, albumin, and gelatin. Examples of starch-derived polymers include carboxymethyl starch and methylhydroxypropyl starch. Examples of alginate-derived polymers include sodium alginate and propylene glycol alginate.

[0044] Examples of acrylic polymers include sodium polyacrylate, polyethyl acrylate, polyacrylamide, and acryloyldimethyl taurate copolymer. Other polymeric thickeners include vinyl polymers such as polyvinyl methyl ether, carboxyvinyl polymer, polyoxyethylene polymer, polyoxyethylene polyoxypropylene copolymer polymer, polyethyleneimine, and cationic polymer.

[0045] Examples of inorganic water-soluble polymers include bentonite, aluminum magnesium silicate, montmorillonite, bydelite, nontronite, saponite, hectorite, and anhydrous silicic acid.

[0046] In this invention, the thickening agent shall be the surfactant described below, excluding those specified later.

[0047] The molecular weight of the thickener is not particularly limited, as long as it can impart the desired viscosity. The method of manufacturing the thickener is also not particularly limited, and it can be obtained from commercially available products, etc.

[0048] (raw materials) The raw materials contain polymerizable monomers and thickeners as described above, and in particular, the viscosity can be adjusted to a predetermined range by the thickener.

[0049] The raw materials used in step 1 may include other components in addition to polymerizable monomers and thickeners. Examples of other components include surfactants and solvents.

[0050] Examples of surfactants include nonionic surfactants, anionic surfactants, and cationic surfactants, with nonionic surfactants being preferred.

[0051] Examples of nonionic surfactants include polyoxyethylene sorbitan monooleate, polyoxyethylene polyoxypropylene block copolymer, polyethylene glycol octylphenyl ether, and polyoxyethylene lauryl ether. These can be obtained from commercial products, for example. A commercially available polyoxyethylene sorbitan monooleate is, for example, Tween 20 (manufactured by Tokyo Chemical Industry Co., Ltd.). A commercially available polyoxyethylene polyoxypropylene block copolymer is, for example, Purlonic F68 and Purlonic L62 (both manufactured by ADEKA). A commercially available polyethylene glycol tert-octylphenyl ether is, for example, Triton X-100 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.). A commercially available polyoxyethylene lauryl ether is, for example, Brij 35 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0052] If the raw materials contain a solvent, the type of solvent is not particularly limited, and any solvent capable of dissolving the polymerizable monomer and thickener mentioned above can be appropriately selected. For example, if the polymerizable monomer and thickener are water-soluble, hydrophilic solvents are preferred, and examples include water, alcohol compounds, and mixed solvents thereof. Examples of alcohol compounds include lower alcohol compounds with four or fewer carbon atoms.

[0053] Other solvents include various organic solvents. Such organic solvents include hydrocarbon solvents such as benzene, toluene, and xylene; ketone solvents such as acetone, methyl ethyl ketone, and isophorone; alcohol solvents such as tert-butyl alcohol, benzyl alcohol, phenoxyethanol, and phenylpropylene glycol; halogenated hydrocarbon solvents such as methylene chloride and chloroform; ether solvents such as 1,2-dimethoxyethane, tetrahydrofuran, 1,4-dioxane, and anisole; ester solvents such as ethyl acetate, propyl acetate, ethyl carbitol acetate, and butyl carbitol acetate; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; and carbonate solvents such as dimethyl carbonate, diethyl carbonate, and propylene carbonate.

[0054] The raw materials may include polymerizable monomers and thickeners, as well as surfactants and solvents as needed, and may also contain other components as long as they do not impair the effects of the present invention. Examples of other components include pH adjusters, light stabilizers, antioxidants, preservatives, fillers such as inorganic particles, flame retardants, pigments, colorants, fungicides, and lubricants. One or more of these additives may be included in the raw materials.

[0055] The viscosity of the raw material used in step 1 can be, for example, in the range of 20 to 1000 cP at 25°C. Having this viscosity makes graft polymerization less likely to be inhibited, and as a result, the grafting rate in graft polymerization can be increased. The viscosity of the raw material is preferably 20 cP or higher, more preferably 30 cP or higher, even more preferably 40 cP or higher, and particularly preferably 50 cP or higher at 25°C. Furthermore, in terms of facilitating a high grafting rate, the viscosity of the raw material is preferably 1000 cP or lower, more preferably 500 cP or lower, even more preferably 300 cP or lower, and particularly preferably 150 cP or lower.

[0056] The viscosity of the raw material can be measured using a rotational viscometer. Specifically, the spiral viscometer "PC-1TL" from Malcolm Corporation can be used to measure the viscosity of the raw material under the following conditions: measurement temperature of 25°C, rotation speed of 40 rpm, and sample volume of 200 mL.

[0057] In the raw materials used in step 1, the content of the thickener is adjusted, for example, so that the raw materials fall within the viscosity range described above. For example, the content of the thickener varies depending on its molecular weight, but is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and also preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and particularly preferably 1% by mass or less.

[0058] In the raw materials used in step 1, the content of polymerizable monomers is adjusted, for example, so that the raw materials are set within the viscosity range described above. For example, the content of polymerizable monomers is preferably 1% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, even more preferably 15% by mass or more, particularly preferably 20% by mass or more, and also preferably 90% by mass or less, more preferably 60% by mass or less, even more preferably 50% by mass or less, even more preferably 30% by mass or less, and particularly preferably 25% by mass or less, based on the total amount of the raw materials.

[0059] The raw materials used in step 1 may consist only of polymerizable monomers and thickeners.

[0060] If the raw materials used in step 1 contain surfactants, the percentage of surfactants to be contained is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, particularly preferably 0.2% by mass or more, and also preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 5% by mass or less, and particularly preferably 3% by mass or less, based on the total amount of raw materials.

[0061] If the raw materials used in step 1 contain a solvent, the solvent content can be arbitrarily adjusted within a range of 1 to 90% by mass relative to the total amount of the raw materials.

[0062] The method for preparing the raw materials used in step 1 is not particularly limited. For example, the raw materials used in step 1 can be prepared by mixing polymerizable monomers and thickeners with solvents and surfactants in predetermined amounts, if necessary.

[0063] In step 1, the raw material and the substrate are brought into contact. The method of bringing the raw material and the substrate into contact is not particularly limited and can include methods such as immersing the substrate in the raw material or spraying the raw material onto the substrate.

[0064] When immersing a substrate in raw materials, the immersion method is not particularly limited, and known immersion methods can be widely applied. For example, an immersion method can be used in which the entire substrate is immersed in the raw materials and the immersion state is maintained for a predetermined time, or a so-called roll method can be employed in which the substrate is fed out by a roll and passed through a solution tank containing the raw materials.

[0065] The temperature of the raw materials when immersing the base material is not particularly limited; for example, immersion can be carried out at 5 to 80°C, preferably 10 to 50°C. The immersion time is also not particularly limited; for example, the base material should be immersed in the raw materials for at least 15 seconds. The raw materials may be stirred as appropriate while the base material is immersed.

[0066] If the raw materials contain volatile components such as solvents, these volatile components may be evaporated as needed. For example, volatile components can be removed by drying the substrate after contact between the raw materials and the substrate. The drying method is not particularly limited and may include heating or natural drying.

[0067] In step 1, the raw materials come into contact with the substrate, causing the raw materials to adhere to the substrate. Specifically, the polymerizable monomers and thickeners in the raw materials adhere to the substrate. The substrate, with the raw materials attached in this manner, is then subjected to step 2, where graft polymerization takes place.

[0068] Project 2 Step 2 is a step in which graft polymerization is performed by irradiating the "substrate to which the raw material is attached" obtained in Step 1 with radiation. By such graft polymerization, a graft polymer is obtained in which the surface of the substrate is coated with a graft polymer.

[0069] The substrate used in step 2 is the substrate obtained in step 1 to which the raw materials are attached. More specifically, the substrate used in step 2 is a substrate to which at least polymerizable monomers and thickeners are attached. If the raw materials contain surfactants, the surfactants may also be attached to the substrate. If the raw materials contain volatile components such as solvents, the volatile components may be removed in step 1 as described above, or they may be removed in step 2.

[0070] The radiation used in step 2 can be electromagnetic waves or particle beams. Examples of electromagnetic waves include X-rays and gamma rays, while examples of particle beams include alpha rays, beta rays, electron beams, neutron beams, proton beams, and heavy ion beams. Among these, electron beams are preferred.

[0071] Radiation can be irradiated, for example, using known radiation devices. If the radiation is an electron beam, electron beams emitted from various types of electron accelerators such as Cockcroft-Walton, Van de Graaff, Schenkel, linear, Dynamitron, and radiofrequency accelerators can be used. When irradiating with radiation, the acceleration voltage can be in the range of 130kV to 5000kV, and the irradiation dose can be in the range of 5 to 300kGy.

[0072] The radiation irradiation time can be selected within an appropriate range depending on the electron beam acceleration voltage (kV) and electron beam irradiation dose (kGy), for example, from 3 seconds to 1 minute. Radiation irradiation may be applied to only one side of the substrate or to both sides.

[0073] After irradiation with radiation, the substrate can be subjected to heat treatment or appropriate drying treatment as needed.

[0074] In step 2, irradiation with radiation promotes graft polymerization of polymerizable monomers. This causes the polymerization reaction of polymerizable monomers to proceed starting from the substrate surface, forming a polymer of polymerizable monomers on the substrate surface. In other words, graft polymerization induced by radiation irradiation coats the substrate surface with a polymer of polymerizable monomers, resulting in a graft polymer in which the substrate is coated with polymer. In the graft polymer, the substrate surface and the polymer are bonded by covalent bonds.

[0075] Conventionally, in graft polymerization, as mentioned above, radicals originating from the substrate generated by electron beam irradiation react with oxygen in the atmosphere before they can react with the monomer, which leads to a problem of reduced graft polymerization rates.

[0076] In contrast, in the present invention, the raw materials used in step 1 contain a thickening agent and have a certain viscosity, so that the substrate surface is less likely to come into contact with the atmosphere. As a result, the radicals derived from the substrate generated by electron beam irradiation are less affected by oxygen in the atmosphere. Consequently, the radicals derived from the substrate react more readily with polymerizable monomers, allowing graft polymerization by radiation irradiation to proceed efficiently and with a high grafting rate.

[0077] Therefore, in the present invention, unlike the technology disclosed in the aforementioned Patent Document 1, for example, it is not necessary to cover the substrate with a polymer film to isolate it from the atmosphere when irradiating it with radiation. In other words, the manufacturing method of the present invention allows for graft polymerization of polymerizable monomers without requiring the step of covering the substrate with a polymer film.

[0078] However, in the present invention, in order to further increase the graft rate, the substrate before irradiation with radiation, that is, the substrate to which the polymerizable monomer obtained in step 1 is attached, may be pre-coated with a polymer film. In this case, a wide range of films that have been used to coat substrates in conventional radiation polymerization can be used as the polymer film, and for example, polymer films such as polyethylene terephthalate with low oxygen permeability can be preferably used. The thickness of the polymer film is not particularly limited as long as radiation-induced graft polymerization is not inhibited. The method of coating the substrate with the polymer film is also not particularly limited, and for example, a method in which a pair of polymer films are fed out on a roll and the substrate is sealed by sandwiching it from above and below can be mentioned.

[0079] A substrate coated with a polymer film can undergo radiation-induced graft polymerization by irradiating it with radiation in the same manner as described above. After irradiation, the polymer film can be peeled off the substrate using an appropriate method to obtain the graft polymer.

[0080] In step 2, the substrate may be coated with a polymer film as described above before being irradiated with radiation, or the substrate may be irradiated with radiation without coating it with a polymer film, that is, without covering the substrate to which the polymerizable monomer and thickener are attached with any layer. Therefore, according to the method for producing graft polymers of the present invention, a graft polymer with a high graft ratio can be obtained by a simple method.

[0081] The manufacturing method of the present invention may include other steps besides steps 1 and 2, or the manufacturing method of the present invention may consist only of steps 1 and 2.

[0082] The graft polymers obtained by the manufacturing method of the present invention have a substrate covered with a polymer having a high grafting rate and can be widely applied to various uses. For example, graft polymers obtained by the manufacturing method of the present invention can be used in functional clothing, battery diaphragms, water treatment filters, and the like.

[0083] In identifying the inventions contained herein, the components (properties, structures, functions, etc.) described in each embodiment of this disclosure may be combined in any way. That is, this disclosure encompasses all subject matter consisting of any combination of the combinatable components described herein. [Examples]

[0084] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to the embodiments of these examples.

[0085] (Example 1a) A mixture with a viscosity of 69.1 cP (25°C) was prepared by mixing 10% by mass of glycidyl methacrylate as a polymerizable monomer, 0.5% by mass of carboxymethylcellulose (CMC) as a thickener, 1% by mass of Tween 20 as a surfactant, and 88.5% by mass of deionized water as a solvent. A polypropylene nonwoven fabric was immersed in this mixture for 1 minute without nitrogen purging. After this immersion treatment, the polypropylene nonwoven fabric was removed and exposed to air at 25°C for 1 hour. Then, one side of the polypropylene nonwoven fabric was irradiated with a 750 kV, 20 kGY electron beam to perform graft polymerization. Subsequently, the polypropylene nonwoven fabric was heated at 50°C for 1 hour. This resulted in a graft polymer in which the polymerizable monomer polymer was coated onto the substrate.

[0086] (Example 1b) A graft polymer was obtained in the same manner as in Example 1, except that a raw material with a viscosity of 123.0 cP (25°C) was prepared by mixing 10% by mass of glycidyl methacrylate, 0.75% by mass of carboxymethylcellulose (CMC), 1% by mass of Tween 20 as a surfactant, and 88.25% by mass of deionized water.

[0087] (Comparative Example 1a) A graft polymer was obtained in the same manner as in Example 1, except that a raw material with a viscosity of less than 20 cP (25°C) was prepared by mixing 10% by mass of glycidyl methacrylate, 1% by mass of Tween 20, and 89% by mass of deionized water.

[0088] (Example 2a) A graft polymer was obtained in the same manner as in Example 1, except that a raw material with a viscosity of 74.2 cP (25°C) was prepared by mixing 20% ​​by mass of glycidyl methacrylate, 0.5% by mass of carboxymethylcellulose (CMC), 1% by mass of Tween 20 as a surfactant, and 78.5% by mass of deionized water.

[0089] (Example 2b) A graft polymer was obtained in the same manner as in Example 1, except that a raw material with a viscosity of 194.0 cP (25°C) was prepared by mixing 20% ​​by mass of glycidyl methacrylate, 0.75% by mass of carboxymethylcellulose (CMC), 1% by mass of Tween 20 as a surfactant, and 78.25% by mass of deionized water.

[0090] (Example 3a) A graft polymer was obtained in the same manner as in Example 1, except that a raw material with a viscosity of 118.0 cP (25°C) was prepared by mixing 30% by mass of glycidyl methacrylate, 0.5% by mass of carboxymethylcellulose (CMC), 1% by mass of Tween 20 as a surfactant, and 68.5% by mass of deionized water.

[0091] (Example 3b) A graft polymer was obtained in the same manner as in Example 1, except that a raw material with a viscosity of 216.0 cP (25°C) was prepared by mixing 30% by mass of glycidyl methacrylate, 0.75% by mass of carboxymethylcellulose (CMC), 1% by mass of Tween 20 as a surfactant, and 68.25% by mass of deionized water.

[0092] (viscosity measurement) The viscosity of the raw materials was measured using a rotational viscometer. Specifically, a spiral viscometer "PC-1TL" from Malcolm Corporation was used, and the viscosity of the raw materials was measured under the following conditions: measurement temperature of 25°C, rotation speed of 40 rpm, and sample volume of 200 mL.

[0093] (Graft ratio measurement) The graft ratio in graft polymerization is given by the following formula (1) Graft rate (%) = (BA) / A × 100 (1) (In equation (1), A is the mass of the substrate before grafting (g), and B is the mass of the substrate after grafting (g).) This was calculated using the following method. Here, the mass of the substrate before grafting refers to the mass of the substrate weighed before immersion treatment.

[0094] (Evaluation results) Table 1 shows the measurement results of the graft rate of the graft polymers obtained in each example and comparative example. Table 1 also shows the viscosity measurement results of the raw materials used to produce the graft polymers.

[0095] [Table 1]

[0096] The results in Table 1 show that graft polymers with a high grafting rate can be obtained by performing graft polymerization using raw materials containing polymerizable monomers and thickeners.

Claims

1. Step 1 involves contacting a substrate with a raw material containing polymerizable monomers and a thickening agent to adhere the raw material to the substrate, Step 2 involves irradiating a substrate to which the aforementioned raw materials are attached with radiation to perform graft polymerization and obtain a graft polymer. A method for producing graft polymers, comprising the following:

2. The method for producing a graft polymer according to claim 1, wherein the radiation is an electron beam.

3. The method for producing a graft polymer according to claim 1 or 2, wherein the substrate is a polymer substrate.

4. The method for producing a graft polymer according to claim 3, wherein the substrate is a fibrous substrate.

5. The method for producing a graft polymer according to claim 1 or 2, wherein the thickening agent is a polymer-based thickening agent.

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