Antistatic composition for polymer materials

Abstract

To provide an antistatic composition that can express antistatic performance with stable electric resistance values without altering the properties of a polymer material.SOLUTION: An antistatic composition includes an antistatic agent including an imidazoline-based nonionic surfactant and Bronsted acid and a nano material. According to the inventor's findings, such an antistatic composition can express antistatic performance with stable electric resistance values without altering the properties of a polymer material.SELECTED DRAWING: None

Description

Technical Field

[0001] The main object of the present invention is to exhibit antistatic performance with a stable electrical resistance value without changing the properties of the polymer material.

Background Art

[0002] Antistatic agents have attracted attention in various fields as materials for eliminating electrostatic troubles. Among them, attention has been increasing from the viewpoints of unpleasant phenomena such as the adhesion of dust due to static electricity generated by the movement and contact of the human body, and the induction of disasters such as dust explosions. Also, with the sophistication of equipment, problems related to static electricity, such as the induction of serious system failures due to malfunctions of electronic devices in the information, electronics, and precision fields, and the impact on precision production lines that indirectly have a serious impact, have become increasingly major issues with the evolution of civilization, and quite advanced countermeasures are required. Therefore, in recent years, various antistatic products have been emerging at a rapid pace, and particularly recently, products that can stably exhibit an electrical resistance value in the intermediate region between the antistatic level and the conductivity level have been attracting attention. In addition, polymer materials are used in various forms in various industries and are one of the very convenient materials, but since they are insulating materials, antistatic measures are taken by treatments such as adding antistatic agents.

[0003] Surfactants have been utilized as antistatic agents for a long time, and it is known that antistatic performance is exhibited in various hydrophilic groups such as nonionic, anionic, cationic, and amphoteric. Among these hydrophilic groups, it is publicly known that cationic surfactants, in particular, have excellent antistatic performance. Regarding the mechanism of antistatic performance expression by surfactants, when a surfactant is applied to a certain substrate, the surfactant applied to the surface arranges in a form like a continuous phase on the substrate surface. By adsorbing moisture in the air, this arranged surfactant exhibits conductivity and antistatic performance.

[0004] On the other hand, there are concerns about changes in the properties of polymer materials due to stickiness and other issues caused by the addition of surfactants as antistatic agents. For these reasons, there is a need to achieve antistatic performance with a stable electrical resistance value without altering the properties of polymer materials (Non-Patent Literature 1). [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Surface Technology, Vol. 56, No. 8, 447 (2005) [Overview of the project] [Problems that the invention aims to solve]

[0006] The main objective of this invention is to achieve antistatic performance with a stable electrical resistance value without altering the properties of polymer materials. [Means for solving the problem]

[0007] As a result of diligent research to solve the various problems mentioned above, the inventors of this invention discovered that an antistatic agent consisting of an imidazoline-type nonionic surfactant and Brønsted acid is superior. Furthermore, they found that by supporting this antistatic agent on nanomaterials and using it, the changes in the properties of polymer materials caused by the antistatic agent can be suppressed, thus completing the present invention.

[0008] In other words, the present invention is as follows. An antistatic agent composition comprising a nanomaterial and an imidazoline-type nonionic surfactant represented by the following general formula (1) and a Brønsted acid represented by the following general formula (2) in a molar ratio of (1):(2) = 30:70 to 50:50. [ka] [ka]

[0009] However, in the above general formula (1), R 1 R represents a linear or branched alkyl group or alkylene group having 7 to 21 carbon atoms, and in the general formula (2) above, 2 The antistatic agent is characterized by having one to 22 C1 alkyl groups, alkylene groups, or phenyl groups, having 1 to 3 C1 hydroxyalkyl groups, hydroxyphenyl groups, or alkyl groups or alkylene groups in which at least one hydrogen atom is substituted with a fluorine atom, and A is characterized by having one of the following: a carboxylic acid group, a sulfonic acid group, a monovalent phosphate group, or a phosphate ester group.

[0010] An antistatic agent composition for polymer materials, comprising supporting the antistatic agent on a nanomaterial in an amount of 1.0 parts by mass or more.

[0011] An antistatic composition for polymer materials, wherein the nanomaterial is at least one selected from titanium dioxide, silicon dioxide, iron oxide, zirconium dioxide, zinc oxide, aluminum oxide, boehmite, and cerium oxide. [Effects of the Invention]

[0012] The antistatic agent and antistatic composition for polymer materials of the present invention can exhibit antistatic performance with a stable electrical resistance value without altering the properties of the polymer material. [Modes for carrying out the invention]

[0013] The following describes in detail embodiments for carrying out the present invention (hereinafter simply referred to as "this embodiment"). This embodiment is illustrative for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be implemented by modifying it as appropriate within the scope of its gist.

[0014] As a result of intensive studies to solve the various problems described above, the inventors have found that an antistatic agent composed of an imidazoline-type nonionic surfactant and a Bronsted acid is excellent. Further, it has been found that by supporting this antistatic agent on a nanomaterial and using it, changes in the properties of the polymer material due to the antistatic agent can be suppressed.

[0015] (Imidazoline-type nonionic surfactant)

[0016] The type of the imidazoline-type nonionic surfactant is not particularly limited, and an appropriate one can be selected as appropriate. For example, an imidazoline-type nonionic surfactant represented by the general formula (1) that is generally easily available can be mentioned. [Chemical formula]

[0017] R in the general formula (1) 1 is not particularly limited, but from the ease of availability, it is preferably 1 to 22 carbon atoms. Its lower limit is more preferably 7 or more, further preferably 11 or more, still further preferably 13 or more, even more preferably 15 or more, and even further preferably 17 or more. Also, its upper limit is more preferably 22 or less.

[0018] Specifically, for example, 2-(2-heptyl-2-imidazolin-1-yl)ethanol, 2-(2-octyl-2-imidazolin-1-yl)ethanol, 2-(2-nonyl-2-imidazolin-1-yl)ethanol, 2-(2-decyl-2-imidazolin-1-yl)ethanol, 2-(2-undecyl-2-imidazolin-1-yl)ethanol, 2-(2-dodecyl-2-imidazolin-1-yl)ethanol, 2-(2-tridecyl-2-imidazolin-1-yl)ethanol, 2-(2-tetradecyl-2-imidazolin-1-yl)ethanol, 2-(2-pentadecyl-2-imidazolin-1-yl)ethanol, 2-(2-hexadecyl-2-imidazolin-1-yl)ethanol, 2-[2-(2-hexyldecyl)-2-imidazolin-1-yl]ethanol, 2-(2-heptadecyl-2-imidazolin-1-yl)ethanol, 2-[2-(8-heptadecenyl)-2-imidazolin-1-yl]ethanol, 2-(2-henicosyl-2-imidazolin-1-yl)ethanol, etc. can be mentioned.

[0019] The imidazoline-type nonionic surfactant may be used alone or in combination of two or more.

[0020] (Bronsted acid)

[0021] A and R of the Bronsted acid represented by the general formula (2) that can be used in the antistatic agent of this patent 2 are not particularly limited and can be appropriately selected in consideration of the types of other components to be used, desired physical properties, etc. [Chemical formula]

[0022] R of the general formula (2) 2Because they are generally readily available, these can represent linear or branched alkyl groups, alkylene groups, or phenyl groups having 1 to 22 carbon atoms, hydroxyalkyl groups, hydroxyphenyl groups having 1 to 3 carbon atoms and a primary or secondary hydroxyl group, or alkyl groups, alkylene groups in which at least one hydrogen atom is substituted with a fluorine atom. In general formula (2), A can represent a carboxylic acid group, a sulfonic acid group, a monovalent phosphate group, and a phosphate ester group, etc. 2 The combination of A and B is not particularly limited.

[0023] Specifically, examples include aliphatic carboxylic acids, aliphatic sulfonic acids, aliphatic phosphate esters, aromatic carboxylic acids, aromatic sulfonic acids, aromatic phosphate esters, aliphatic hydroxy acids, aromatic hydroxy acids, sulfate esters, vinyl group-containing sulfonic acids, fluorine atom-containing carboxylic acids, fluorine atom-containing sulfonic acids, and the like.

[0024] Specific examples of aliphatic carboxylic acids include, for example, methaneic acid, ethaneic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, (Z)-octadeca-9-enoic acid, (9Z,12Z)-octadeca-9,12-dienoic acid, (9Z,12Z,15Z)-9,12,15-octadecatrienoic acid, (5Z,8Z11Z,14Z)-5,8,11,14-eicosatetraenoic acid, and 2-propenylacrylic acid.

[0025] Specific examples of aliphatic sulfonic acids include, for example, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butanesulfonic acid, pentanesulfonic acid, hexanesulfonic acid, heptanesulfonic acid, octanesulfonic acid, nonanesulfonic acid, decanesulfonic acid, dodecanesulfonic acid, tetradecanesulfonic acid, hexadecanesulfonic acid, and octadecanesulfonic acid.

[0026] Specific examples of aliphatic phosphate esters include, for example, dimethyl phosphate, diethyl phosphate, dibutyl phosphate, dipentyl phosphate, dihexyl phosphate, bis(2-ethylhexyl) phosphate, dioctyl phosphate, dinonyl phosphate, didecyl phosphate, didodecyl phosphate, ditridecyl phosphate, ditetradecyl phosphate, dihexadecyl phosphate, and dioctadecyl phosphate.

[0027] Specific examples of aromatic carboxylic acids include, for example, benzenecarboxylic acid, benzene-1,2-dicarboxylic acid, benzene-1,3-dicarboxylic acid, benzene-1,4-dicarboxylic acid, 2-hydroxybenzenecarboxylic acid, 3,4,5-trihydroxybenzenecarboxylic acid, benzenehexacarboxylic acid, and 3-phenylpropaneoic acid.

[0028] Specific examples of aromatic sulfonic acids include, for instance, dodecylbenzenesulfonic acid and p-toluenesulfonic acid.

[0029] Specific examples of aromatic phosphate esters include, for instance, diphenyl phosphate.

[0030] Specific examples of aliphatic hydroxy acids include hydroxyacetic acid, 2-hydroxypropionic acid, glyceric acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, γ-hydroxybutyric acid, and ricinoleic acid.

[0031] Specific examples of aromatic hydroxy acids include, for example, 2-hydroxybenzoic acid, 4-hydroxy-3-methoxybenzoic acid, diphenylglycolic acid, 2-methoxycinnamic acid, (E)-3,4-dihydroxycinnamic acid, 3-hydroxy-4-methoxycinnamic acid, and 4-hydroxy-3,5-dimethoxycinnamic acid.

[0032] Specific examples of sulfate esters include, for example, dodecyl sulfate.

[0033] Specific examples of vinyl group-containing sulfonic acids include, for example, 2-acrylamido-2-methylpropanesulfonic acid and parastyrenesulfonic acid.

[0034] Specific examples of fluorine-containing carboxylic acids include, for example, perfluorooctanoic acid.

[0035] Specific examples of fluorine-containing sulfonic acids include trifluoroacetate and perfluorooctanesulfonic acid.

[0036] Among these, due to their availability, it is preferable that one or more are selected from the group consisting of aliphatic carboxylic acids, aliphatic sulfonic acids, aliphatic phosphate esters, aromatic carboxylic acids, aromatic sulfonic acids, aromatic phosphoric acids, etc., such as methaneic acid, ethaneic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, heptadecanoic acid, octadecanoic acid, (Z)-octadeca-9-enoic acid, (9Z,12Z)-octadeca-9,12-dienoic acid, (9Z,12Z,15Z)-9,12,15-octadecatrienoic acid, (5Z,8Z,11Z,14Z) -5,8,11,14-Eicosatetraenoic acid, 2-Propenylacrylic acid, Methanesulfonic acid, Ethanolonic acid, Propanesulfonic acid, Butanesulfonic acid, Pentanesulfonic acid, Hexanesulfonic acid, Heptanesulfonic acid, Octanesulfonic acid, Nonanesulfonic acid, Decanesulfonic acid, Dodecanesulfonic acid, Tetradecanesulfonic acid, Hexadecanesulfonic acid, Octadecanesulfonic acid, Dimethyl phosphate, Diethyl phosphate, Dibutyl phosphate, Dipentyl phosphate, Dihexyl phosphate, Bis(2-ethylhexyl) phosphate, Dioctyl phosphate, Dinonyl phosphate, Phosphate It is more preferable that the substance is at least one selected from the group consisting of didecyl acid, didodecyl phosphate, ditridecyl phosphate, ditetradecyl phosphate, dihexadecyl phosphate, dioctadecyl phosphate, benzenecarboxylic acid, benzene-1,2-dicarboxylic acid, benzene-1,3-dicarboxylic acid, benzene-1,4-dicarboxylic acid, 2-hydroxybenzenecarboxylic acid, 3,4,5-trihydroxybenzenecarboxylic acid, benzenehexacarboxylic acid, 3-phenylpropane-2-enoic acid, dodecylbenzenesulfonic acid, p-toluenesulfonic acid, and diphenyl phosphate.

[0037] Brønsted acids may be used individually or in combination of two or more types.

[0038] It is expected that the reaction product of an imidazoline-type nonionic surfactant and a methylating agent will exhibit antistatic properties similar to those of the present invention. However, the use of a methylating agent is more expensive and requires more complicated synthesis procedures compared to Brønsted acid, making Brønsted acid more preferable.

[0039] (Molar ratio)

[0040] In the antistatic agent of the present invention, the molar ratio of the imidazoline-type nonionic surfactant to the Brønsted acid described above is preferably imidazoline-type nonionic surfactant:Brønsted acid = 30:70 to 50:50. The molar ratio is more preferably 30:70, even more preferably 35:65, even more preferably 40:60, even more preferably 45:55, and even more preferably 50:50.

[0041] (Method of manufacturing an antistatic agent)

[0042] The antistatic agent according to this embodiment can be manufactured by mixing the components described above. The manufacturing method of the antistatic agent according to this embodiment includes a step of mixing an imidazoline-type nonionic surfactant and a Brønsted acid. At this time, a salt may be formed. Alternatively, the agent may be manufactured by pre-mixing the solvent described later as "other solvents" or "other additives." In the method for producing the antistatic agent according to this embodiment, it is preferable to mix, for example, an imidazoline-type nonionic surfactant and a Brønsted acid within the molar ratio range described above, using a stirrer or a disperser such as a rotary-orbit mixer.

[0043] (Supporting onto nanomaterials)

[0044] The antistatic agent of the present invention may be used by being supported on a nanomaterial. By supporting the nanomaterial, the bleed-out of the antistatic agent kneaded into the polymer material can be suppressed. The nanomaterials used are not particularly limited, and suitable ones can be selected considering the type of components used and their applications. Examples include titanium dioxide, silicon dioxide, iron oxide, zirconium dioxide, zinc oxide, aluminum oxide, boehmite pseudo, and cerium oxide, which are widely used. Boehmite pseudo is particularly preferred in terms of availability, cost, and effectiveness.

[0045] The average primary particle size of the nanomaterial is not particularly limited as long as it can be dispersed in the polymer material, but it is preferably between 5 nm and 100 nm. The upper limit of this average primary particle size is more preferably 80 nm or less, even more preferably 60 nm or less, even more preferably 50 nm or less, even more preferably 30 nm or less, and even more preferably 20 nm or less. The average primary particle size referred to here is a calculated value from specific surface area data obtained by the BET method.

[0046] Nanomaterials may be used individually or in combination of two or more types.

[0047] The loading of the antistatic agent onto the nanomaterial is not particularly limited, but it is preferable to use nanomaterial in an amount of 1.0 parts by mass or more relative to the antistatic agent. From the viewpoint of suppressing bleed-out, it is more preferable to use 2.0 parts by mass or more.

[0048] (Method for supporting materials on nanomaterials)

[0049] The loading of the antistatic agent onto the nanomaterial according to this embodiment can be achieved by mixing the components. This includes a step of mixing the antistatic agent, which consists of an imidazoline-type nonionic surfactant and a Brønsted acid, with the nanomaterial. For example, it is preferable to disperse and stabilize the nanomaterial, the antistatic agent obtained by mixing the imidazoline-type nonionic surfactant and the Brønsted acid, and other additives in a solvent using a stirrer or disperser.

[0050] Mixing of polymer materials can be carried out by known methods. For example, general methods such as dispersers like rotary mixers and homogenizers, ultrasonic stirrers, rocking mills, ball mills, jet mills, and spike mills can be used. Mixing conditions can be appropriately selected considering the proportions and properties of each component used.

[0051] (polymer material)

[0052] There are no particular limitations on the polymer materials to which the antistatic agent of the present invention can be applied, and a suitable material can be determined by considering the type of antistatic agent used and its application. For example, ABS resin, AS resin, EVA resin, polyethylene resin, PET resin, acrylic resin, polypropylene resin, polystyrene resin, polyvinyl alcohol, polyvinyl chloride resin, and vinylidene chloride resin are examples of materials that are commonly used and readily available.

[0053] (Application of antistatic agents to polymer materials)

[0054] The application of the antistatic agent of the present invention to polymer materials is not particularly limited, but may include coating or mixing. Common coating methods such as dip coating, spin coating, spray coating, roll coating, and bar coating can be used. Methods of kneading include, for example, kneading an antistatic agent into a heated and melted polymer material; adding an antistatic agent when polymerizing monomers or oligomers that are raw materials for the polymer material; preparing a solution by mixing the polymer material and the antistatic agent with a suitable solvent, then removing the solvent from the solution to form the polymer material; and mixing and kneading using roll kneading, bumper kneading, extruders, kneaders, etc.

[0055] (Amount of antistatic agent added to polymer materials)

[0056] The antistatic agent of the present invention can be suitably applied depending on the type of polymer material and other components, and can be applied without upper limit as long as there are no problems with the application of the polymer material to which it is applied. From the viewpoint of antistatic effect, 0.3 parts by weight or more is preferred, 0.5 parts by weight or more is more preferred, and 1.0 part by weight or more is even more preferred, per 100 parts by weight of the polymer material composition.

[0057] (Other solvents, other additives, etc.)

[0058] There are no particular restrictions on the solvent that can be used in the antistatic agent according to this embodiment, and it can be appropriately selected depending on the type of polymer material to which it is applied. Examples include ether-based solvents such as dibutyl ether, tetrahydrofuran, and dioxane; ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, diethyl ketone, and N-methyl-2-pyrrolidone; ester-based solvents such as ethyl acetate, isopropyl acetate, propylene glycol monomethyl ether acetate, methyl acrylate, methyl methacrylate, and isobornyl acrylate; aromatic solvents such as xylene, toluene, and styrene; and hydrocarbon-based solvents such as hexane, methylcyclohexane, and mineral spirits.

[0059] Among these, from the viewpoint of handling, it is preferable that one or more are selected from the group consisting of ester solvents, aromatic solvents, hydrocarbon solvents, etc., and it is more preferable that at least one is selected from the group consisting of methyl acetate, isopropyl acetate, propylene glycol monomethyl ether acetate, methyl acrylate, methyl methacrylate, isobornyl acrylate, xylene, toluene, styrene, hexane, methylcyclohexane, and mineral spirits.

[0060] Other known additives may be used. Examples include leveling agents, UV absorbers, antioxidants, viscosity modifiers, etc.

[0061] The content of each additive is not particularly limited and can be determined to suit the conditions, taking into consideration the type of component used and its intended use. [Examples]

[0062] The present invention will be described in more detail by the following examples and comparative examples, but the present invention is not limited in any way by the following examples. Unless otherwise specified, all reagents used were special grade or first grade reagents manufactured by Tokyo Chemical Industry Co., Ltd.

[0063] (Preparation of antistatic agent)

[0064] The imidazoline-type nonionic surfactant represented by general formula (1) was synthesized by a known method (Japanese Patent Publication No. 10-17554). Subsequently, the imidazoline-type nonionic surfactant and 1 mole of ethaneic acid per 1 mole of the imidazoline-type nonionic surfactant were placed in an ointment jar. Then, under room temperature conditions, a rotation-and-revolution type mixer (device name: Awatori Rentaro (registered trademark) ARE-310, manufactured by Shinky Co., Ltd.) was used to perform a mixing treatment for 10 minutes and a defoaming treatment for 5 minutes to obtain an antistatic agent (Examples 1-8, Comparative Examples 4-9) which is a mixture of the imidazoline-type nonionic surfactant and Brønsted acid or a salt thereof. Comparative Examples 2-3 consisted only of the imidazoline-type nonionic surfactant.

[0065] Details of the surfactants used are as follows:

[0066] Imidazolin-type nonionic surfactants

[0067] [ka]

[0068] In the formula, -CR 1 The group represents a lauric acid residue, an oleic acid residue, or a coconut oil fatty acid residue.

[0069] (Preparation of antistatic agent composition)

[0070] The prepared antistatic agent was mixed with 1.0 to 2.0 times its weight of powdered boehmite particles (particle size (short diameter × long diameter): 10 × 50 nm (arithmetic mean diameter determined by observation with an electron microscope)) (Aluminum Sol-10A, manufactured by Kawaken Fine Chemical Co., Ltd.) in a toluene solution.

[0071] (Incorporation into polymer materials)

[0072] A PS resin toluene solution was obtained by heating and stirring toluene while adjusting the concentration to 20 wt% by dissolving pelletized PS resin (average molecular weight 2,000, Tokyo Chemical Industry Co., Ltd.). Various antistatic agents of the present invention, or nanomaterial-supported antistatic agents, were added to the obtained PS resin toluene solution and made miscible. Then, 4 g of the solution was poured into a Teflon mold measuring 70 mm in length, 70 mm in width, and 1 mm in thickness, and dried overnight at room temperature to obtain a PS resin film containing an antistatic agent (Examples 1-8). For comparison, Comparative Examples 1-9 without the addition of nanomaterials were also obtained.

[0073] (Antistatic performance evaluation)

[0074] The antistatic performance was evaluated by measuring the surface resistance using an ultra-insulating meter (SM-8220, HIOKI E.E. CORPORATION) and a flat plate sample electrode (SME-8311, HIOKI E.E. CORPORATION) under conditions of 25°C, 25% relative humidity, 500V applied voltage, and 60 seconds of measurement time, and was evaluated based on the following criteria. ○: Surface resistance (Ω / □) is 1E+9 or greater, and less than 1E+12. △: Surface resistance (Ω / □) is 1E+12 or greater, but less than 1E+13. ×: Surface resistance (Ω / □) is 1E+13 or greater

[0075] (Adhesion assessment)

[0076] The antistatic agent described in this patent was applied to films that were then stacked together, and the presence or absence of adhesion was visually confirmed and evaluated based on the following criteria. ○: No adhesion △: Has some adhesion properties ×: Adhesive

[0077] Examples of antistatic agent compositions [Table 1]

[0078] Comparative example of an antistatic agent composition [Table 2]

[0079] Based on the above, each of the antistatic agent compositions prepared within the scope of the present invention exhibited low surface resistance values, a positive antistatic performance rating (○), little to no stickiness on the polymer material, and an adhesion rating of △ or higher. Thus, the antistatic agent and antistatic agent composition for polymer materials of the present invention were able to exhibit antistatic performance with stable electrical resistance values ​​without altering the properties of the polymer material.

Claims

[Claim 1] An antistatic agent composition for polymer materials, wherein an antistatic agent for polymer materials is supported on a nanomaterial in an amount of 1.0 parts by mass or more, (a) An imidazoline-type nonionic surfactant represented by general formula (1), (b) A Brønsted acid represented by general formula (2), It contains in a molar ratio (a):(b) = 30:70 to 50:50, and Antistatic composition for polymer materials, characterized in that the nanomaterial is at least one selected from titanium dioxide, silicon dioxide, iron oxide, zirconium dioxide, zinc oxide, aluminum oxide, pseudoboehmite, and cerium oxide: 【Chemistry 1】 【Chemistry 2】 However, in the above general formula (1), R １ R represents a linear or branched alkyl group or alkylene group having 7 to 21 carbon atoms, and in the general formula (2), ２ However, A represents any of the following: a linear or branched alkyl group, alkylene group, or phenyl group having 1 to 22 carbon atoms; a hydroxyalkyl group, hydroxyphenyl group having 1 to 3 carbon atoms and a primary or secondary hydroxyl group; or an alkyl group or alkylene group in which at least one hydrogen atom is substituted with a fluorine atom; and A represents any of the following: a carboxylic acid group, a sulfonic acid group, a monovalent phosphate group, or a phosphate ester group.

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