Dust suppression treatment agent compositions and mixtures

Abstract

To provide a dust suppression treatment agent composition and mixture that can suppress the scattering of dust-generating substances after being mixed with them. [Solution] The dust suppression treatment agent composition of the present invention is a dust suppression treatment agent composition for a dust-generating substance, wherein the dust suppression treatment agent composition comprises an aqueous medium and polytetrafluoroethylene particles, and the aspect ratio of the polytetrafluoroethylene particles is less than 1.65.

Description

[Technical Field]

[0001] The present invention relates to dust suppression treatment agent compositions and mixtures. [Background technology]

[0002] Polytetrafluoroethylene is sometimes used in the form of an aqueous dispersion, in which polytetrafluoroethylene is dispersed in an aqueous medium, due to its ease of handling and other advantages. As a method for producing such an aqueous dispersion, Patent Document 1 discloses a method for obtaining an aqueous dispersion containing polytetrafluoroethylene particles by polymerizing tetrafluoroethylene in a solution containing an i-butyl methacrylate polymer and water, without adding a surfactant. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2021 / 085470 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] As mentioned above, polytetrafluoroethylene is used in various industrial fields due to its excellent properties, and one of its applications is as a raw material for dust suppression treatment agent compositions to suppress the scattering of dust-generating substances. The present inventors evaluated the suitability of an aqueous dispersion containing polytetrafluoroethylene particles obtained by the method described in Patent Document 1 above as a dust suppression treatment agent composition, and found that there is room for improvement in suppressing the scattering of dust-generating substances.

[0005] The present invention has been made in view of the above problems, and aims to provide a dust suppression treatment agent composition and mixture that can suppress the scattering of dust-generating substances after being mixed with them. [Means for solving the problem]

[0006] As a result of intensive studies, the inventors of the present invention have found that the above problems can be solved by the following configuration, and thus have arrived at the present invention. [1] A dust suppression treatment agent composition for dust-containing substances, wherein the dust suppression treatment agent composition contains an aqueous medium and polytetrafluoroethylene particles, and the aspect ratio of the polytetrafluoroethylene particles is less than 1.65. [2] The dust suppression treatment agent composition according to [1], which substantially does not contain an emulsifier having a fluorine atom. [3] The dust suppression treatment agent composition according to [1] or [2], wherein the content of a nonionic emulsifier having no fluorine atom is 5.0% by mass or less based on the total mass of the dust suppression treatment agent composition. [4] The dust suppression treatment agent composition according to any one of [1] to [3], wherein the content of the polytetrafluoroethylene particles is 10 to 70% by mass based on the total mass of the dust suppression treatment agent composition. [5] A mixture comprising the dust suppression treatment agent composition according to any one of [1] to [4] and a dust-containing substance. [6] A mixture comprising polytetrafluoroethylene particles and a dust-containing substance, wherein the aspect ratio of the polytetrafluoroethylene particles is less than 1.65. [Advantages of the Invention]

[0007] According to the present invention, there are provided a dust suppression treatment agent composition and a mixture capable of suppressing the scattering of a dust-containing substance after being mixed with the dust-containing substance. [Modes for Carrying Out the Invention]

[0008] The meanings of the terms in the present invention are as follows. Numerical ranges expressed using "~" represent a range that includes the numbers before and after "~" as the lower and upper limits, respectively. In numerical ranges described stepwise in this specification, the upper or lower limit stated in one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described in this specification, the upper or lower limit stated in one numerical range may be replaced with the values ​​shown in the examples. In this specification, each component may be represented by a single substance or by a combination of two or more substances. When two or more substances are used in combination for each component, the content of that component refers to the total content of the combined substances unless otherwise specified. In this specification, a combination of two or more preferred embodiments is a more preferred embodiment. A "unit" is a general term for an atomic group derived from one monomer molecule, which is directly formed by the polymerization of monomers, and an atomic group obtained by chemically transforming a part of the above atomic group. A "unit based on monomers" will also be simply referred to as a "unit" below. The content (mass %) or mole %) of each unit relative to the total number of units in a polymer is determined by analyzing the polymer using solid-state nuclear magnetic resonance (NMR) spectroscopy. However, the content of each unit calculated from the amount of each monomer used usually closely matches the actual content of each unit.

[0009] [Dust suppression agent composition] The dust suppression treatment agent composition of the present invention is a dust suppression treatment agent composition for a dust-generating substance, wherein the dust suppression treatment agent composition comprises an aqueous medium and polytetrafluoroethylene particles dispersed in the aqueous medium, and the aspect ratio of the polytetrafluoroethylene particles is less than 1.65. Hereinafter, the dust suppression treatment agent composition of the present invention will also be referred to as "this composition." Furthermore, polytetrafluoroethylene particles contained in this composition with an aspect ratio of less than 1.65 will also be referred to as "specific PTFE particles."

[0010] When this composition is mixed with a dust-generating substance, the scattering of the dust-generating substance can be suppressed. This is presumed to be due to the following reasons. The effect of PTFE particles in suppressing the scattering of dust-generating substances is thought to be exerted by the fibrillation of PTFE particles through shearing or other treatments, which then captures the dust-generating substances. Here, since the aspect ratio of the PTFE particles contained in this composition is less than 1.65, they can be uniformly mixed and dispersed with the dust-generating substances. This is thought to facilitate fibrillation of the PTFE particles when the mixture of this composition and the dust-generating substances is subjected to shearing treatment. As a result, it is presumed that the scattering of dust-generating substances can be effectively suppressed.

[0011] [Specified PTFE particles] The polytetrafluoroethylene (hereinafter also referred to as "PTFE") contained in the specific PTFE particles may be a homopolymer of tetrafluoroethylene (hereinafter also referred to as "TFE"), or it may be modified PTFE.

[0012] Modified PTFE preferably contains TFE units and units based on modified monomers copolymerizable with TFE units (hereinafter also referred to as "modified monomer units"). The content of modified monomer units in modified PTFE is preferably 0.0001 to 1% by mass, more preferably 0.0005 to 0.50% by mass, and even more preferably 0.001 to 0.40% by mass, relative to the total units of modified PTFE. A modified monomer unit refers to a part of the molecular structure of modified PTFE that originates from a modified monomer, while the total units of modified PTFE refer to all parts of the molecular structure of modified PTFE that originate from all monomers. The content of modified monomer units can be determined by known methods such as Fourier transform infrared spectroscopy (FT-IR). The modified monomer can be any monomer capable of copolymerizing with TFE, such as perfluoroolefins like hexafluoropropylene; chlorofluoroolefins like chlorotrifluoroethylene; hydrogen-containing fluoroolefins like trifluoroethylene and vinylidene fluoride; perfluorovinyl ether; perfluoroalkyl ethylene; and ethylene. Modified monomers may be used individually or in combination of two or more.

[0013] The PTFE content in the specific PTFE particles is preferably 95 to 100% by mass, more preferably 96 to 100% by mass, and even more preferably 98 to 100% by mass, relative to the total mass of the specific PTFE particles.

[0014] The specified PTFE particles may also contain fluorine-containing polymers other than the aforementioned PTFE or modified PTFE (hereinafter also referred to as "fluorine-containing polymer (Y)"). The specific PTFE particles are preferably PTFE particles obtained by the method for producing the dust suppression treatment agent composition described later, as they are easy to adjust the aspect ratio to less than 1.65. Specifically, the specific PTFE particles are preferably PTFE particles obtained by polymerizing a monomer containing TFE in the presence of a fluorine-containing polymer (Y).

[0015] The fluorine-containing polymer (Y) preferably has units based on monomers having vinyl groups which may be substituted with fluorine atoms, and more preferably has units based on monomers having vinyl groups which are substituted with fluorine atoms.

[0016] A preferred unit based on a monomer having a vinyl group substituted with a fluorine atom is a unit based on perfluoro(alkyl vinyl ether) (hereinafter also referred to as "PAVE") (hereinafter also referred to as "PAVE unit"). PAVE is preferred as a monomer represented by formula (1) because of its excellent polymerization reactivity when producing fluorine-containing polymers (Y) and because it allows for more efficient production of specific PTFE particles. CF2 = CF - OR f1 (1) In formula (1), R f1 R represents a perfluoroalkyl group having 1 to 10 carbon atoms. f1 The number of carbon atoms is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 5, and particularly preferably 1 to 3, from the standpoint of superior polymerization reactivity. Perfluoroalkyl groups may be linear or branched.

[0017] Specific examples of PAVE include perfluoro(methyl vinyl ether) (hereinafter also referred to as "PMVE"), perfluoro(ethyl vinyl ether) (hereinafter also referred to as "PEVE"), and perfluoro(propyl vinyl ether) (hereinafter also referred to as "PPVE"). Among these, PMVE and PPVE are preferred, with PMVE being more preferred, because they allow for the more efficient production of specific PTFE particles.

[0018] When the fluorine-containing polymer (Y) has units based on monomers having vinyl groups which may be substituted with fluorine atoms, the content of units based on monomers having vinyl groups which may be substituted with fluorine atoms is preferably 20 to 60 mol%, more preferably 25 to 60 mol%, and even more preferably 30 to 55 mol% relative to the total units of the fluorine-containing polymer (Y).

[0019] The fluorine-containing polymer (Y) preferably has units based on tetrafluoroethylene (hereinafter also referred to as "TFE") (hereinafter also referred to as "TFE units"), as this provides superior effects of the present invention. When the fluorine-containing polymer (Y) has TFE units, the TFE unit content is preferably 30 to 90 mol%, more preferably 40 to 80 mol%, and even more preferably 45 to 70 mol%, relative to the total units of the fluorine-containing polymer (Y).

[0020] The fluorine-containing polymer (Y) preferably contains TFE units and PAVE units, as this allows for easier adjustment of Tg within the range described below and provides superior effects of the present invention. When the fluoropolymer (Y) contains TFE units and PAVE units, in the fluoropolymer (Y), the PAVE units are preferably 20 to 60 mol%, more preferably 25 to 60 mol%, and still more preferably 30 to 55 mol% based on the total of the TFE units and the PAVE units, from the viewpoints of facilitating the adjustment of Tg within the range described below and enabling the more efficient production of specific PTFE particles.

[0021] The fluoropolymer (Y) may have units other than the TFE units and the PAVE units. Specifically, the fluoropolymer (Y) may have at least one unit selected from the group consisting of units based on vinylidene fluoride (hereinafter also referred to as "VdF"), units based on hexafluoropropylene (hereinafter also referred to as "HFP"), and units based on propylene (hereinafter also referred to as "propylene units"). Further, the fluoropolymer (Y) may have units based on a monomer having two or more polymerizable unsaturated bonds (hereinafter also referred to as "BO units"). The BO units are units based on a monomer having two or more polymerizable unsaturated bonds. Specific examples of the polymerizable unsaturated bond include a carbon atom-carbon atom double bond (C=C) and a carbon atom-carbon atom triple bond (C≡C). The number of polymerizable unsaturated bonds in BO is preferably 2 to 6, more preferably 2 or 3, and still more preferably 2, from the viewpoint of more excellent polymerization reactivity. BO preferably further has a fluorine atom from the viewpoint that the compression set of the crosslinked rubber article at high temperatures becomes smaller. BO is preferably a monomer represented by the formula (3). (CR 31 R 32 =CR 33 ) a3 R 34 (3) In the formula (3), R 31 , R 32 and R 33Each of these independently represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group. a3 represents an integer from 2 to 6. R 34 This represents a α3 valent perfluorohydrocarbon group having 1 to 10 carbon atoms, or a group having an etheric oxygen atom at the terminal or between carbon-carbon bonds of the perfluorohydrocarbon group. Multiple R 31 , multiple R 32 and multiple R 33 Each of these elements may be the same as or different from the others, but it is preferable that they be the same as each other. a3 is preferably 2 or 3, and more preferably 2.

[0022] The following are preferred combinations of each unit contained in the fluorine-containing polymer (Y). Combination 1: Combination of TFE units and PAVE units Combination 2: Combination of TFE units, PAVE units, and BO units Combination 3: Combination of VdF units and HFP units Combination 4: Combination of TFE units and propylene units Among these, combination 1 or combination 2 is preferred, and combination 2 is more preferred.

[0023] The copolymerization composition of the fluorine-containing polymer (Y) in combinations 1 to 4 is preferably as follows. Combinations 1 and 2: TFE units / PAVE units = 80 / 20 to 50 / 50 (molar ratio), if BO units are included, (total of TFE units + PAVE units) / BO units = 100 / 0.01 to 100 / 1 (molar ratio) Combination 3: VdF units / HFP units = 50 / 50 to 78 / 22 (molar ratio) Combination 4: TFE units / Propylene units = 60 / 40~50 / 50 (molar ratio) In addition, in combinations 1 and 2 described above, it is preferable that the PAVE unit is a PMVE unit.

[0024] The fluorine-containing polymer (Y) may contain units based on monomers other than the above monomer, but when producing specific PTFE particles using the fluorine-containing polymer (Y), it is preferable that it substantially contains units based on other monomers, in order to produce the specific PTFE particles more efficiently. "Substantially free of units based on other monomers" means that the content of units based on other monomers is 0.01 mol% or less relative to the total units of the fluorine-containing polymer (Y), with 0 mol% being more preferable. If the compound X described below is used as the other monomer, it is preferable to use a unit based on another monomer.

[0025] Fluorine-containing polymer (Y) has a main chain with 10 carbon atoms. 6 It is preferable that the number of ionic functional groups per atom is 1000 or less. Polymer main chain has 10 carbon atoms 6 The number of ionic functional groups per individual can be determined by known methods such as Fourier transform infrared spectroscopy (FT-IR). Examples of ionic functional groups include cationic and anionic functional groups. Specific examples of ionic functional groups include carboxylic acid groups (-COO - ), sulfonic acid group (-SO3 - ), sulfate group (-SO4 2- ), phosphonic acid group (-PO3 2- ) and phosphate group (-PO4 3- Examples of anionic functional groups include ) and others.

[0026] The Tg of the fluorine-containing polymer (Y) is preferably 10°C or lower. The Tg of the fluorine-containing polymer (Y) is preferably 5°C or lower, more preferably 3°C or lower, and even more preferably 0°C or lower, from the standpoint of efficiently adsorbing the tetrafluoroethylene-containing monomer used in the production of specific PTFE particles using the fluorine-containing polymer (Y). The Tg of the fluorine-containing polymer (Y) is preferably -50°C or higher, more preferably -45°C or higher, and even more preferably -40°C or higher, from the viewpoint of thermal stability after molding. The Tg of fluorine-containing polymers (Y) is measured by differential scanning calorimetry (DSC). One method for adjusting the Tg of the fluorine-containing polymer (Y) to be within the above range is to adjust the type and amount of monomer used in the production of the fluorine-containing polymer (Y).

[0027] When the specific PTFE particles contain a fluorine-containing polymer (Y), the content of the fluorine-containing polymer (Y) in the specific PTFE particles is preferably more than 0% by mass and 5% by mass or less, more preferably more than 0% by mass and 4% by mass or less, and even more preferably more than 0% by mass and 2% by mass or less, based on the total mass of the specific PTFE particles.

[0028] The content of specific PTFE particles is preferably 10 to 70% by mass, more preferably 15 to 60% by mass, and even more preferably 18 to 50% by mass, based on the total mass of the composition. If the content of specific PTFE particles is above the lower limit of the above range, the miscibility with dust-generating substances is superior. Furthermore, if the content of specific PTFE particles is below the upper limit of the above range, it is superior in that it can save storage volume when stored as feedstock. When mixing with dust-generating substances, this composition may be diluted with water before use.

[0029] The aspect ratio of the specific PTFE particles is less than 1.65, and from the viewpoint of achieving superior effects of the present invention, it is preferably 1.64 or less, more preferably 1.60 or less, and even more preferably 1.55 or less. The lower limit of the aspect ratio of specific PTFE particles is preferably 1.00 or higher, more preferably 1.10 or higher, and even more preferably 1.15 or higher, from the standpoint of superior emulsion stability. The aspect ratio of specific PTFE particles is measured by the method described in the Examples section below.

[0030] From the viewpoint of dispersion stability, the average particle size of the specific PTFE particles is preferably 280 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less. Furthermore, the average particle size of the specific PTFE particles is preferably 80 nm or larger, more preferably 90 nm or larger, and even more preferably 100 nm or larger, in order to achieve superior fibrillation performance. The average particle size of specific PTFE particles is determined by measuring the particle size distribution using the composition by laser diffraction and scattering, calculating a cumulative curve with the total volume of the particle collection set to 100%, and then determining the particle size at the point on the cumulative curve where the cumulative volume reaches 50%.

[0031] [Aqueous medium] Examples of aqueous media include water or a mixed solvent of water and a water-soluble organic solvent. Specific examples of water-soluble organic solvents include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol. The aqueous medium contained in this composition may be a polymerization solvent used in the production of a fluorine-containing polymer (Y) or specific PTFE particles.

[0032] The aqueous medium content is preferably 20 to 90% by mass, more preferably 22 to 88% by mass, and even more preferably 25 to 80% by mass, based on the total mass of the composition.

[0033] [Emulsifiers that do not contain fluorine atoms] This composition may contain an emulsifier that does not contain fluorine atoms. Emulsifiers that do not contain fluorine atoms are characterized by being water-soluble. A water-soluble emulsifier is defined as an emulsifier whose solubility in 1000g of water at 25°C is 100mg or more, while a non-water-soluble emulsifier is defined as an emulsifier other than the water-soluble emulsifiers mentioned above.

[0034] Emulsifiers that do not contain fluorine atoms include those that do not contain carbon-carbon double bonds.

[0035] The emulsifier, which does not contain fluorine atoms, may be either ionic or nonionic.

[0036] <An ionic emulsifier that does not contain fluorine atoms> This composition preferably contains an ionic emulsifier that does not contain fluorine atoms, in order to improve the dispersibility of specific PTFE particles and not inhibit fibrillation when mixed with dust-generating substances. Anionic hydrocarbon emulsifiers are examples of ionic emulsifiers that do not contain fluorine atoms. Anionic hydrocarbon emulsifiers refer to emulsifiers having a negatively charged hydrophilic portion such as a carboxylic acid group, sulfonic acid group, sulfate group, phosphonic acid group, and phosphate group, and a hydrophobic portion such as an alkyl group or other hydrocarbon group. Specific examples of anionic hydrocarbon emulsifiers include sodium dodecyl sulfate, highly branched C10 tertiary carboxylic acids supplied by Resolution Performance Products as Versatic® 10, sodium linear alkyl polyethersulfonate supplied by BASF as the Avane® S series, and the sulfosuccinate emulsifier Lankropol® K8300 available from AkzoNobelSurfaceChemistryLLC. Furthermore, specific examples of anionic hydrocarbon emulsifiers include ammonium laurate, triethanolamine laurate, sodium lauryl sulfate, ammonium lauryl sulfate, and triethanolamine lauryl sulfate.

[0037] When the composition contains an ionic emulsifier that does not contain fluorine atoms, the content of the ionic emulsifier that does not contain fluorine atoms is preferably more than 0% by mass and 5.0% by mass or less, more preferably 0.005 to 4.5% by mass, and even more preferably 0.010 to 4.0% by mass, based on the total mass of the composition.

[0038] This composition may or may not contain a nonionic emulsifier that does not contain fluorine atoms. Examples of nonionic emulsifiers that do not contain fluorine atoms include nonionic hydrocarbon emulsifiers. Nonionic hydrocarbon emulsifiers are emulsifiers that exhibit surface activity without dissociating into ions in water and have hydrocarbon groups such as alkyl groups as their hydrophobic portion. Examples of hydrophilic portions of nonionic hydrocarbon emulsifiers include water-soluble functional groups such as polyethylene oxide chains obtained from the polymerization of ethylene oxide. Examples of nonionic hydrocarbon emulsifiers include polyalkylene oxide block copolymers, such as block copolymers having polyethylene oxide and polypropylene oxide.

[0039] Another example of a nonionic hydrocarbon emulsifier is the emulsifier described in paragraphs 0043 to 0052 of Japanese Patent Publication No. 2016-537499.

[0040] The content of the nonionic emulsifier that does not contain fluorine atoms is preferably 5.0% by mass or less, more preferably 2.0% by mass or less, more preferably 1.5% by mass or less, and even more preferably 1.0% by mass or less, based on the total mass of the composition, from the viewpoint of emulsion stability. The lower limit for the content of nonionic emulsifiers that do not contain fluorine atoms is 0% by mass.

[0041] Emulsifiers that do not contain fluorine atoms may contain silicon atoms. Examples of emulsifiers containing silicon atoms include siloxane emulsifiers. Siloxane emulsifiers are hydrocarbon-containing emulsifiers having a siloxane skeleton. Examples of siloxane emulsifiers include those described in U.S. Patent No. 6,841,616 (Wille et al.) and No. 7,977,438 (Brothers et al.).

[0042] Emulsifiers that do not contain fluorine atoms may also be polymer emulsifiers. Examples of polymer emulsifiers include polymers having hydrophilic groups in their side chains. Such polymer emulsifiers include polymers that contain units based on compounds having both a site that can react in polymerization and a hydrophilic group. Also included are polymers that have undergone post-treatment such as hydrolysis, and which contain units based on compounds that have a group that can become a hydrophilic group, even if they do not initially have a hydrophilic group.

[0043] [Emulsifiers containing fluorine atoms] From the standpoint of reducing environmental impact, it is preferable that this composition substantially does not contain emulsifiers containing fluorine atoms. Furthermore, if this composition substantially does not contain emulsifiers containing fluorine atoms, the aspect ratio of specific PTFE particles in this composition can be made smaller. "Substantially free of emulsifiers containing fluorine atoms" means that the content of emulsifiers containing fluorine atoms is 10 ppm by mass or less, with a preference of 150 ppb by mass or less, and a preference of 50 ppb by mass or less, relative to the total mass of the composition. The lower limit is 0 ppb by mass. The content of the emulsifier containing fluorine atoms is preferably 5 ppm by mass or less, more preferably 150 ppb by mass or less, and even more preferably 50 ppb by mass or less, relative to the solid content of the composition. The lower limit is 0 ppb by mass.

[0044] One characteristic of emulsifiers containing fluorine atoms is that they are water-soluble. A water-soluble emulsifier is one in which the solubility in 1000g of water at 25°C is 100mg or more, while a non-water-soluble emulsifier is one in which the emulsifier is not water-soluble. Furthermore, both fluorine-containing polymers and specific PTFE particles are non-water soluble.

[0045] The emulsifier containing a fluorine atom may be either ionic or nonionic. Emulsifiers containing fluorine atoms include those that do not have a carbon-carbon double bond.

[0046] Examples of emulsifiers containing fluorine atoms include anionic fluorine-containing emulsifiers. Examples of anionic fluorine-containing emulsifiers include emulsifiers containing fluorine atoms with a total carbon number of 20 or less in the portion excluding the anionic group, and emulsifiers containing fluorine atoms with a molecular weight of 800 or less in the anionic portion. The above-mentioned "anionic portion" refers to the portion of the anionic fluorine-containing emulsifier excluding the cation.

[0047] The emulsifier containing a fluorine atom may be the same emulsifier containing a silicon atom as described above. The emulsifier containing a fluorine atom may be the polymer emulsifier described above.

[0048] Furthermore, neither the fluorine-containing polymer mentioned above nor compound X described later are considered emulsifiers.

[0049] [Other ingredients] This composition may contain components other than the specified PTFE particles, aqueous medium, and emulsifier described above (hereinafter also referred to as "other components"). Specific examples of other components include ammonia and preservatives. If this composition contains other components, the content of the other components is preferably greater than 0% by mass and 0.3% by mass or less, and more preferably greater than 0% by mass and 0.1% by mass or less, relative to the total mass of this composition.

[0050] [Method for producing a dust suppression agent composition] An example of a method for producing the above-mentioned composition (dust suppression treatment agent composition) includes step 1, in which a monomer containing TFE is polymerized in an aqueous dispersion containing a fluorine-containing polymer (Y) and a first aqueous medium to obtain composition 1 containing a second aqueous medium and the above-mentioned specific PTFE particles dispersed in the second aqueous medium. The method for producing this composition may further include step 2, in which an emulsifier that does not contain fluorine atoms is added to composition 1 obtained in step 1 to obtain composition 2, which comprises a second aqueous medium, the above-mentioned specific PTFE particles dispersed in the second aqueous medium, and the emulsifier that does not contain fluorine atoms. Here, composition 1 obtained in step 1 may be used as the dust suppression agent composition, and if the method for producing this composition includes step 2, composition 2 obtained in step 2 may be used as the dust suppression agent composition.

[0051] According to the method for producing this composition, a dust suppression treatment agent composition containing PTFE particles with an aspect ratio of less than 1.65 can be easily obtained.

[0052] [Process 1] Step 1 is a step of polymerizing a monomer containing TFE in an aqueous dispersion containing a fluorine-containing polymer (Y) and a first aqueous medium to obtain composition 1 containing a second aqueous medium and the above-mentioned specific PTFE particles dispersed in the second aqueous medium. According to Step 1, specific PTFE particles can be efficiently produced using an environmentally friendly aqueous medium without requiring an emulsifier. This is presumed to be because the aqueous dispersion containing the fluorine-containing polymer (Y) functioned as a good polymerization site for the specific PTFE particles. Furthermore, although the reason is unclear, PTFE particles with an aspect ratio of less than 1.65 (i.e., specific PTFE particles) can be easily obtained by performing Step 1. Below, we will first describe in detail the materials used in Step 1, and then describe in detail the procedure for Step 1.

[0053] <Aqueous dispersion> In step 1, an aqueous dispersion containing a fluorine-containing polymer (Y) and a first aqueous medium is used.

[0054] (Fluorine-containing polymer) The fluorine-containing polymer (Y) contained in the aqueous dispersion is the same as the fluorine-containing polymer that may be contained in the specific PTFE particles described above, including its preferred embodiment, so its explanation is omitted.

[0055] Before starting the polymerization of the monomer containing TFE in step 1, the content of the fluorine-containing polymer is preferably 0.01 to 4.0% by mass, more preferably 0.01 to 2.0% by mass, and even more preferably 0.01 to 1.5% by mass, relative to the total mass of the aqueous dispersion, in order to efficiently produce specific PTFE particles.

[0056] In this specification, "before the polymerization of the monomer containing TFE is started in step 1" means immediately before the start of polymerization. Here, "the start of polymerization" refers to the point in time when the monomer containing TFE and the polymerization initiator are brought into the reactor together after the reactor temperature has been raised to above the polymerization temperature, and the point in time when the reactor temperature is raised to above the polymerization temperature after the monomer containing TFE and the polymerization initiator have been brought into the reactor together.

[0057] In step 1, before initiating polymerization of the monomer containing TFE, the concentration of sulfate ions is preferably 10 ppm by mass or less, and more preferably 5 ppm by mass or less, relative to the total mass of the first aqueous medium in the aqueous dispersion, in order to suppress the discoloration of specific PTFE particles. The lower limit is 0 ppm by mass. One example of a method to achieve the above-mentioned sulfate ion concentration is to remove sulfate ions using an anion exchange resin during the production of the fluorine-containing polymer (Y). Here, sulfate ions originate, for example, from polymerization initiators (particularly ammonium persulfate) used in the production of fluorine-containing polymers (Y), and may be present in aqueous dispersions containing fluorine-containing polymers (Y). By keeping the sulfate ion content below 10 ppm by mass (particularly below 5 ppm by mass), it is possible to suppress the formation of low heat-resistant end groups on specific PTFE particles, and as a result, discoloration of specific PTFE particles is suppressed.

[0058] In step 1, before initiating polymerization of the monomer containing TFE, the concentration of ammonium ions is preferably 20 ppm by mass or less, and more preferably 10 ppm by mass or less, relative to the total mass of the first aqueous medium in the aqueous dispersion, in order to suppress aggregation of specific PTFE particles. The lower limit is 0 ppm by mass. One example of a method to achieve the above-mentioned ammonium ion concentration is to remove ammonium ions using a cation exchange resin during the production of a fluorine-containing polymer (Y). Here, ammonium ions originate, for example, from initiators (particularly ammonium persulfate) used in the production of fluorine-containing polymers (Y), and may be present in aqueous dispersions containing fluorine-containing polymers (Y). It is presumed that a ammonium ion content of 20 ppm by mass or less reduces the ionic strength in the first aqueous medium, resulting in improved production efficiency of specific PTFE particles.

[0059] The fluorine-containing polymer (Y) is preferably dispersed in the first aqueous medium in the form of particles. In this case, the average particle size of the fluorine-containing polymer (Y) is preferably 1 to 150 nm, more preferably 10 to 120 nm, and even more preferably 50 to 120 nm, from the standpoint of enabling more efficient production of specific PTFE particles. The average particle size of the fluorine-containing polymer (Y) was determined by measuring the particle size distribution using laser diffraction and scattering methods with an aqueous dispersion. A cumulative curve was obtained by setting the total volume of the particle collection to 100%, and the particle size (D50) at the point on the cumulative curve where the cumulative volume reaches 50% was determined. Detailed measurement conditions are as described in the Examples section.

[0060] A preferred method for producing the fluorine-containing polymer (Y) is to polymerize monomers containing fluorine atoms (preferably a monomer mixture containing TFE and PAVE) in an aqueous medium in the presence of a polymerization initiator. This yields a fluorine-containing polymer dispersed in particulate form in an aqueous medium. The aqueous medium in which the particles of the fluorine-containing polymer (Y) obtained in this manner are dispersed may be used as the aqueous dispersion as is, or another aqueous medium may be added to it and used as the aqueous dispersion. Alternatively, the fluorine-containing polymer (Y) may be dispersed in another aqueous medium by solvent substitution and used as the aqueous dispersion.

[0061] For the polymerization initiator used in the production of the fluorine-containing polymer (Y), water-soluble polymerization initiators are preferred, persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, organic polymerization initiators such as disuccinic acid peroxide and azobisisobutylamidine dihydrochloride are more preferred, persulfates are even more preferred, and ammonium persulfate is particularly preferred.

[0062] Aqueous media used in the production of fluorine-containing polymers (Y) include water or a mixed solvent of water and a water-soluble organic solvent. Specific examples of water-soluble organic solvents include tert-butanol, propylene glycol, dipropylene glycol, dipropylene glycol monomethyl ether, and tripropylene glycol.

[0063] In the production of the fluorine-containing polymer (Y), a compound represented by formula (X) (hereinafter also referred to as "compound X") may be used. Specifically, the method for producing the fluorine-containing polymer (Y) may be a method of polymerizing monomers containing fluorine atoms in an aqueous medium in the presence of compound X and a polymerization initiator. Compound X can be polymerized with specific monomers described later.

[0064] Compound X is a compound represented by formula (X). CX 1 X 2 =CX 3 -LZ ···(X) In formula (X), X 1 and X 2 Each of these is independently a hydrogen atom, an alkyl group, or a fluoroalkyl group. X 3 is a hydrogen atom, a fluorine atom, an alkyl group, or a fluoroalkyl group. L is a single bond or a divalent linking group. Z is -SO3M, -OSO3M, -P(=O)(OM)2, -OP(=O)(OM)2, or -COOM. M is a hydrogen atom, a metal atom, N(R) M1 )4 or P(R M2 )4, and if there are multiple Ms, the multiple Ms may be the same or may be different from each other. R M1 and R M2 Each is independently a hydrogen atom or a substituent, and R M1 Any two of them may be joined together to form a ring, and multiple R M1 They may be the same, or they may be different from each other, R M2 Any two of them may be joined together to form a ring, and multiple R M2 They may be the same, or they may be different from one another.

[0065] In formula (X), 1 and X 2 Each of these is independently a hydrogen atom, an alkyl group, or a fluoroalkyl group. The alkyl group and fluoroalkyl group may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group and the fluoroalkyl group is preferably 1 to 10, more preferably 1 to 3, and even more preferably 1. A specific example of the above fluoroalkyl group is -CF3. X 1 and X 2 From the viewpoint of increasing the number of particles in the first polymer, it is preferable that all of these are hydrogen atoms. In formula (X), 3 This is a hydrogen atom, a fluorine atom, an alkyl group, or a fluoroalkyl group. Specific examples and preferred embodiments of the alkyl and fluoroalkyl groups mentioned above are given by X 1 and X 2 The specific examples and preferred embodiments of alkyl groups and fluoroalkyl groups are the same as those described in [reference]. X 3 From the viewpoint of increasing the number of particles of the fluorine-containing polymer (Y), fluorine atoms or hydrogen atoms are preferred, and hydrogen atoms are more preferred.

[0066] In formula (X), L is a single bond or a divalent linking group. Examples of the above-mentioned divalent linking groups include alkylene groups, carbonyl groups, ether bonds, thioether bonds, sulfonyl groups, -NH-, -SiH2-, phenylene groups, fluoroalkylene groups (e.g., -CF2-), and groups formed by combining two or more of these. Examples of groups formed by combining two or more of these include ester bonds, thioester bonds, amide bonds, sulfonamide bonds, combinations of alkylene groups and ether bonds, combinations of alkylene groups and ester bonds, and combinations of alkylene groups and amide bonds. The alkylene group and the fluoroalkylene group may be linear, branched, or cyclic, with linear or branched being preferred, and branched being more preferred. The number of carbon atoms in the alkylene group and the fluoroalkylene group can be, for example, 1 to 6, with 1 to 4 being preferred.

[0067] Specific examples of L include single bonds, alkylene groups, fluoroalkylene groups, ether bonds, ester bonds, * C -CO-NH-R-* Z Examples include single bonds, alkylene groups with 1 to 6 carbon atoms, fluoroalkylene groups with 1 to 6 carbon atoms, and * C -CO-NH-R-* Z Preferably, a single bond, an alkylene group having 1 to 2 carbon atoms, and * C -CO-NH-R-* Z This is more preferable. Here, * C * is the bonding site with the carbon atom in formula (X), Z is the bonding site with Z in formula (X), and R is an alkylene group having 1 to 6 carbon atoms.

[0068] In equation (X), Z is -SO3M, -OSO3M, -P(=O)(OM)2, -OP(=O)(OM)2, or -COOM. As for Z, from the viewpoint of stabilizing the dispersion and increasing the amount of fluorine-containing polymer (Y) particles, -SO3M and -COOM are preferred, -SO3Na and -COONa are more preferred, and -SO3Na is even more preferred.

[0069] M is a hydrogen atom, a metal atom, N(R) M1 )4 or P(R M2 )4, R M1 and R M2 Each of these is independently a hydrogen atom or a substituent. The metal atom represented by M is preferably a metal atom from Group 1, and more preferably Li, Na, or K. R M1 and R M2 The substituent represented is preferably a monovalent organic group, more preferably a monovalent hydrocarbon group, and even more preferably an alkyl group or an aromatic hydrocarbon group. The number of carbon atoms in the substituent is preferably 1 to 10. The alkyl group may be linear, branched, or cyclic. The above aromatic hydrocarbon group may be monocyclic or polycyclic. A phenyl group is preferred as the above aromatic hydrocarbon group.

[0070] Examples of the molecular weight of compound X include 70 to 900, with 70 to 750 being preferred and 100 to 550 being more preferred from the viewpoint of dispersion stability.

[0071] Specific examples of compound X include vinyl sulfonic acid, vinyl phosphonic acid, (meth)acrylic acid, allyl sulfonic acid, allyl phosphonic acid, butenic acid, crotonic acid, vinyl acetic acid, 2-sulfoethyl methacrylic acid, 4-vinylbenzenesulfonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid, N-tigroylglycine, 6-acrylamidohexanoic acid, 1,1-difluoro-2-methyl-2-[(1-oxo-2-propen-1-yl)amino]-1-propanesulfonic acid, 3-methyl-3-[(2-methyl-1-oxo-2-propen-1-yl)amino]-2-butanesulfonic acid, 2-methacrylamido-2-methylpropanesulfonic acid, 2,3-dimethyl-3-[(1-oxo-2-propen-1-yl)amino]-2-butanesulfonic acid, and their metal salts. Examples of the above-mentioned metal salts include metal salts of metal atoms represented by M.

[0072] Compound X is preferably a vinyl compound having a sulfonic acid group, a phosphonic acid group, or a carboxyl group; an allyl compound having a sulfonic acid group, a phosphonic acid group, or a carboxyl group; (meth)acrylic acid; (meth)acrylamide having a sulfonic acid group, a phosphonic acid group, or a carboxyl group; and metal salts thereof. Vinyl sulfonic acid, sodium vinyl sulfonate, allyl sulfonic acid, sodium allyl sulfonate, 2-acrylamide-2-methyl-1-propanesulfonic acid, sodium 2-acrylamide-2-methyl-1-propanesulfonate, 2-methacrylamide-2-methyl-1-propanesulfonic acid, or sodium 2-methacrylamide-2-methyl-1-propanesulfonate. Note that "(meth)acrylic acid" is a concept that includes both acrylic acid and methacrylic acid, and "(meth)acrylamide" is a concept that includes both acrylamide and methacrylamide.

[0073] Before initiating the polymerization of the monomer used in the production of the fluorine-containing polymer (Y), the content of compound X is preferably 1.0 to 1000 ppm by mass, more preferably 1.0 to 500 ppm by mass, even more preferably 3.0 to 100 ppm by mass, and particularly preferably 5.0 to 30.0 ppm by mass, relative to the total mass of the first aqueous medium, in which the effects of the present invention are more superior.

[0074] The method for producing the fluorine-containing polymer (Y) preferably includes a heating step in which an aqueous medium in which the fluorine-containing polymer (Y) is dispersed is heated. This deactivates the polymerization initiator present in the system, making it less susceptible to the influence of the polymerization initiator used in the production of the fluorine-containing polymer (Y) when producing specific PTFE particles. As a result, it is easier to obtain PTFE with a high molecular weight. The heating temperature in the heating step is preferably 70 to 100°C, more preferably 80 to 98°C, and even more preferably 85 to 95°C, as this can further promote the deactivation of the polymerization initiator in the aqueous medium.

[0075] (1st aqueous medium) The aqueous dispersion used in step 1 contains a first aqueous medium. As described above, the first aqueous medium contained in the aqueous dispersion may be the polymerization solvent used in the production of the fluorine-containing polymer. A specific example of the first aqueous medium contained in the aqueous dispersion is the same as the specific example of the aqueous medium used in the production of the fluorine-containing polymer (Y) described above. Before initiating polymerization of the specific monomer, the content of the first aqueous medium is preferably 60 to 99.9% by mass, more preferably 96 to 99.9% by mass, and even more preferably 98 to 99.9% by mass, relative to the total mass of the aqueous dispersion.

[0076] (Other ingredients) The aqueous dispersion used in step 1 may contain other components besides the fluorine-containing polymer (Y) and the first aqueous medium. Other specific examples of components that the aqueous dispersion may contain include chain transfer agents, pH adjusters, and waxes. Details of these other components are as described above, so a further explanation will be omitted.

[0077] If the aqueous dispersion contains a chain transfer agent, the content of the chain transfer agent is preferably 0.1 to 5 parts by mass per 100 parts by mass of the first aqueous medium. Furthermore, the amount of chain transfer agent used is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 15 parts by mass, and even more preferably 0.1 to 10 parts by mass, per 100 parts by mass of the monomer used in step 1. If the aqueous dispersion contains a pH adjusting agent, the content of the pH adjusting agent is preferably 0.01 to 3.0 parts by mass per 100 parts by mass of the first aqueous medium. If the aqueous dispersion contains wax, the wax content is preferably 1 to 10 parts by mass per 100 parts by mass of the first aqueous medium.

[0078] Before starting the polymerization of the monomer containing TFE in step 1, the concentration of the emulsifier containing fluorine atoms is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, even more preferably 25 ppm by mass or less, and particularly preferably 5 ppm by mass or less, relative to the total mass of the fluorine-containing polymer (Y) in the aqueous dispersion, from the viewpoint of reducing environmental impact. The lower limit is 0 ppm by mass. The details of the emulsifier containing a fluorine atom are as described above, so we will omit further explanation. One example of a method for adjusting the concentration of the emulsifier containing fluorine atoms to the above-mentioned range is a method for producing an aqueous dispersion without using an emulsifier containing fluorine atoms.

[0079] Before starting the polymerization of the monomer containing TFE in step 1, the concentration of fluoride ions is preferably 100 ppm by mass or less, and more preferably 50 ppm by mass or less, relative to the total mass of the aqueous dispersion, from the viewpoint of polymerization stability. The lower limit is 0 ppm by mass. One example of a method to achieve the above-mentioned fluoride ion concentration is to remove fluoride ions using an anion exchange resin during the production of a fluorine-containing polymer. Here, fluoride ions may be present in the aqueous dispersion as a result of the reaction between a polymerization initiator (e.g., ammonium persulfate) and monomers used in the production of fluorine-containing polymers.

[0080] In step 1, a specific monomer containing TFE is used. The amount of TFE used is preferably 97 to 100% by mass, more preferably 98 to 100% by mass, and even more preferably 99 to 100% by mass, relative to the amount of monomer used in step 1.

[0081] The monomer in step 1 may contain fluorine-containing monomers other than TFE, but it does not need to substantially contain fluorine-containing monomers other than TFE. "Substantially free of fluorine-containing monomers other than TFE" means that the amount of fluorine-containing monomers other than TFE used is less than 0.0001% by mass relative to the amount of monomers used in step 1, and may even be 0% by mass. Other fluorine-containing monomers besides TFE include monomers containing a fluorine atom from the examples of modified monomers mentioned above. Two or more fluorine-containing monomers other than TFE may be used in combination.

[0082] The monomer in step 1 may contain monomers other than fluorine-containing monomers (hereinafter also referred to as "other monomers"), but it is preferable that it does not contain other monomers. "Substantially free of other monomers" means that the amount of other monomers used is less than 0.0001% by mass relative to the amount of monomer used in step 1, and 0% by mass is preferred. Other monomers include monomers that do not contain a fluorine atom, as exemplified in the modified monomers mentioned above. Two or more other monomers may be used in combination.

[0083] The amount of monomer used in step 1 is preferably 1 to 50 parts by mass, more preferably 1 to 40 parts by mass, and even more preferably 1 to 30 parts by mass, based on 100 parts by mass of the aqueous medium contained in the aqueous dispersion.

[0084] <Polymerization initiator> In step 1, it is preferable that the specific monomer is polymerized in the presence of a polymerization initiator. Preferred polymerization initiators include oil-soluble radical initiators, water-soluble radical initiators, and water-soluble redox catalysts. Specific examples of oil-soluble radical initiators include oil-soluble organic peroxides such as tert-butyl peroxypivalate (hereinafter also referred to as "PBPV") and diisopropyl peroxydicarbonate (hereinafter also referred to as "IPP"). Specific examples of water-soluble radical initiators include persulfates such as ammonium persulfate and potassium persulfate, and water-soluble organic peroxides such as disuccinic acid peroxide, bisglutaric acid peroxide, and tert-butyl hydroperoxide (hereinafter also referred to as "TBHP"). As a water-soluble redox catalyst, a combination of an oxidizing agent such as bromate or its salt, chloric acid or its salt, persulfate or its salt, permanganate or its salt, or hydrogen peroxide, and a reducing agent such as sulfurous acid or its salt, bisulfite or its salt, thiosulfate or its salt, organic acids, or inorganic salts is preferred. As persulfates, potassium persulfate and ammonium persulfate are preferred. As sulfites, sodium sulfite is preferred. As inorganic salts, combinations of sulfate anions, sulfite anions, and chloride anions with metal ions are examples. As metal ions, transition metals are preferred, including manganese, iron, cobalt, nickel, copper, zinc, cerium, and silver ions, with iron ions being particularly preferred. As an inorganic salt, iron(II) sulfate is preferred. The polymerization initiator is preferably an oil-soluble radical initiator or a water-soluble radical initiator, with water-soluble radical initiators being more preferred because they allow for more efficient production of fluorine-containing polymers. Two or more polymerization initiators may be used in combination.

[0085] The amount of polymerization initiator used is preferably 1 to 1000 ppm, more preferably 5 to 750 ppm, and even more preferably 10 to 500 ppm, per 100 parts by mass of the specific monomer used.

[0086] <Other ingredients> Other components (hereinafter also referred to as "other components") may be used during the polymerization of specific monomers. Specific examples of other components include reducing agents. The amount of other components used is preferably 1 to 2000 ppm per 100 parts by mass of the specific monomer used.

[0087] <Step 1 Procedure> In step 1, a monomer containing TFE is polymerized in an aqueous dispersion to produce a composition 1 comprising a second aqueous medium and the aforementioned specific PTFE particles dispersed in the second aqueous medium.

[0088] The above monomers are introduced into the reaction system (i.e., polymerization reaction vessel) by conventional methods. For example, specific monomers may be introduced into the reaction system continuously or intermittently so that the polymerization pressure reaches a predetermined pressure. Alternatively, specific monomers may be dissolved in an aqueous medium, and the resulting solution may be introduced into the reaction system continuously or intermittently. When a polymerization initiator is used, it may be added to the reaction system all at once or in separate portions.

[0089] The polymerization temperature is preferably 10 to 95°C, and more preferably 15 to 90°C. The polymerization pressure is preferably 0.5 to 4.0 MPaG, and more preferably 0.6 to 3.5 MPaG. For batch processing, the polymerization time is preferably 90 to 1000 minutes, and more preferably 90 to 700 minutes.

[0090] The polymerization of the monomer in step 1 is preferably carried out in a manner where emulsifiers containing fluorine atoms and emulsifiers without fluorine atoms are substantially absent. Details regarding emulsifiers containing fluorine atoms and emulsifiers without fluorine atoms are as described above, so their explanation will be omitted. The condition that emulsifiers containing fluorine atoms and emulsifiers without fluorine atoms are substantially absent means an environment in which the content of emulsifiers containing fluorine atoms and emulsifiers without fluorine atoms is 0.03 ppm by mass or less, relative to the total mass of the first aqueous medium contained in the aqueous dispersion, preferably 0.02 ppm by mass or less, and more preferably 0 ppm by mass.

[0091] <Composition 1> By carrying out step 1, a composition 1 is obtained that comprises a second aqueous medium and the aforementioned specific PTFE particles dispersed in the second aqueous medium.

[0092] (Specified PTFE particles) The specific PTFE particles contained in composition 1 are as described above, so their explanation will be omitted.

[0093] In step 1, it is presumed that when monomers containing TFE polymerize, the TFE monomers polymerize within the particles of the fluorine-containing polymer (Y). Therefore, it is thought that by carrying out step 1, particles containing both the fluorine-containing polymer (Y) and PTFE are produced. In other words, it is presumed that according to step 1, specific PTFE particles are obtained in the form of particles containing both the fluorine-containing polymer (Y) and PTFE.

[0094] If composition 1 contains a fluorine-containing polymer (Y), the content of the fluorine-containing polymer (Y) is preferably 0.10 to 3.0% by mass, more preferably 0.15 to 2.0% by mass, and even more preferably 0.20 to 1.5% by mass, based on the total mass of composition 1.

[0095] The content of specific PTFE particles is preferably 10 to 70% by mass, more preferably 15 to 60% by mass, and even more preferably 18 to 50% by mass, based on the total mass of composition 1.

[0096] In composition 1, the content of PAVE units relative to the total number of units of the polymer (preferably PTFE and fluorine-containing polymer) contained in the specific PTFE particles is preferably 0.1 to 5.0 mol%, more preferably 0.2 to 3.0 mol%, and even more preferably 0.3 to 2.5 mol%. PAVE units are preferably included in fluorine-containing polymers.

[0097] In composition 1, the content of TFE units relative to the total number of polymer units (preferably PTFE and fluorine-containing polymers) contained in specific PTFE particles is preferably 90 to 99.8 mol%, more preferably 93 to 99.5 mol%, and even more preferably 95 to 99.0 mol%. TFE units only need to be present in PTFE, but may also be present in fluorine-containing polymers (Y).

[0098] When composition 1 contains a fluorine-containing polymer (Y), the fluorine-containing polymer (Y) does not necessarily have to be contained in the specific PTFE particles (i.e., the specific PTFE particles and the fluorine-containing polymer (Y) exist separately in composition 1), and may be contained in the specific PTFE particles, but it is preferable that it be contained in the specific PTFE particles.

[0099] The average particle size of the specific PTFE particles in composition 1 is the same as the average particle size of the specific PTFE particles in the composition described above.

[0100] In composition 1, the aspect ratio of the specific PTFE particles is the same as the aspect ratio of the specific PTFE particles in the composition described above.

[0101] (Second aqueous medium) A specific example of the second aqueous medium contained in composition 1 is the same as the specific example of the aqueous medium used in the production of the fluorine-containing polymer (Y) described above. The second aqueous medium may be the first aqueous medium contained in the aqueous dispersion, or it may contain the first aqueous medium contained in the aqueous dispersion and an aqueous medium added separately.

[0102] The content of the second aqueous medium is preferably 20 to 90% by mass, more preferably 22 to 88% by mass, and even more preferably 25 to 80% by mass, relative to the total mass of composition 1, in terms of the dispersion stability of the specific PTFE particles.

[0103] <Other> It is preferable that composition 1 substantially does not contain emulsifiers containing fluorine atoms. Details of emulsifiers containing fluorine atoms are as described above, so their explanation will be omitted. "Substantially free of emulsifiers containing fluorine atoms" means that the content of emulsifiers containing fluorine atoms is 10 ppm by mass or less, preferably 150 ppb by mass or less, and more preferably 50 ppb by mass or less, based on the total mass of composition 1. The lower limit is 0 ppb by mass.

[0104] Composition 1 may contain other components that may be included in the above-described composition.

[0105] In step 1, heat treatment may be performed on composition 1. When performing heat treatment, composition 1 obtained in step 1 may be heated as is, or a radical generating agent may be added before heating, or the content of specific PTFE particles contained in composition 1 may be adjusted by concentration, dilution, etc. before heating.

[0106] [Process 2] Step 2 is a step of adding an emulsifier that does not contain fluorine atoms to the above composition 1 to obtain composition 2 which comprises a second aqueous medium, the above-mentioned specific PTFE particles dispersed in the second aqueous medium, and the emulsifier that does not contain fluorine atoms. Below, we will first describe in detail the materials used in Step 2, and then describe in detail the procedure for Step 2.

[0107] <Composition 1> The composition 1 used in step 2 is as described above, so its explanation will be omitted.

[0108] <Emulsifiers that do not contain fluorine atoms> Details of emulsifiers that do not contain fluorine atoms are as described above. Specifically, these include ionic emulsifiers that do not contain fluorine atoms and nonionic emulsifiers that do not contain fluorine atoms. The amount of emulsifier without fluorine atoms used is preferably 0.01 to 5.0% by mass, more preferably 0.02 to 4.5% by mass, and even more preferably 0.03 to 4.0% by mass, relative to the content of specific PTFE particles contained in composition 1 subjected to step 2. If the amount of emulsifier without fluorine atoms used is above the lower limit of the above range, the dispersion stability of composition 2 is better. If the amount of emulsifier without fluorine atoms used is below the upper limit of the above range, the mixability with dust-generating substances is excellent.

[0109] (An ionic emulsifier that does not contain fluorine atoms) In step 2, it is preferable to use an ionic emulsifier that does not contain fluorine atoms because it provides better emulsion stability. Details of the ionic emulsifier that does not contain fluorine atoms are as described above, so a further explanation will be omitted. The amount of ionic, fluorine-free emulsifier used is preferably 0.01 to 4.0% by mass, more preferably 0.02 to 3.5% by mass, and even more preferably 0.03 to 3.0% by mass, relative to the content of specific PTFE particles contained in composition 1 subjected to step 2. If the amount of ionic, fluorine-free emulsifier used is above the lower limit of the above range, the dispersion stability of composition 2 is better. If the amount of ionic, fluorine-free emulsifier used is below the upper limit of the above range, the mixability with dust-generating substances is excellent.

[0110] (A nonionic emulsifier that does not contain fluorine atoms) In step 2, a nonionic emulsifier that does not contain fluorine atoms may or may not be used. Details of the nonionic emulsifier that does not contain fluorine atoms are as described above, so the explanation will be omitted. The amount of nonionic, fluorine-free emulsifier used is preferably 0 to 3.0% by mass, more preferably 0.001 to 2.8% by mass, and even more preferably 0.005 to 2.5% by mass, relative to the content of specific PTFE particles contained in composition 1 subjected to step 2. If the amount of nonionic, fluorine-free emulsifier used is above the lower limit of the above range, the dispersion stability of composition 2 is better. If the amount of nonionic, fluorine-free emulsifier used is below the upper limit of the above range, the mixing with dust-generating substances is better.

[0111] <Step 2 Procedure> In step 2, an emulsifier that does not contain fluorine atoms is added to composition 1 to produce composition 2.

[0112] <Composition 2> By carrying out step 2, a composition 2 is obtained that comprises a second aqueous medium, the aforementioned specific PTFE particles dispersed in the second aqueous medium, and an emulsifier that does not contain fluorine atoms. Composition 2 may contain other components that may be included in the above-described composition.

[0113] (Specified PTFE particles) The specific PTFE particles contained in composition 2 are the same as the specific PTFE particles contained in composition 1 described above, so their description is omitted.

[0114] As explained in step 1, composition 1 used in step 2 may contain a fluorine-containing polymer (Y). If such composition 1 is used in step 2, composition 2 will also contain a fluorine-containing polymer. If composition 2 contains a fluorine-containing polymer (Y), the fluorine-containing polymer (Y) does not necessarily have to be contained in the specific PTFE particles (i.e., the specific PTFE particles and the fluorine-containing polymer (Y) exist separately in composition 2), or it may be contained in the specific PTFE particles, but it is preferable that it be contained in the specific PTFE particles.

[0115] If composition 2 contains a fluorine-containing polymer (Y), the content of the fluorine-containing polymer (Y) is preferably 0.02 to 3.0% by mass, more preferably 0.02 to 2.0% by mass, and even more preferably 0.02 to 1.5% by mass, based on the total mass of composition 2.

[0116] The content of specific PTFE particles is preferably 10 to 70% by mass, more preferably 15 to 60% by mass, and even more preferably 18 to 50% by mass, based on the total mass of composition 2.

[0117] The average particle size of the specific PTFE particles in composition 2 is the same as the average particle size of the specific PTFE particles in the composition described above.

[0118] In composition 2, the aspect ratio of the specific PTFE particles is the same as the aspect ratio of the specific PTFE particles in the composition described above.

[0119] (Second aqueous medium) The second aqueous medium is as described in step 1, so its explanation will be omitted. The content of the second aqueous medium is preferably 20 to 90% by mass, more preferably 22 to 88% by mass, and even more preferably 25 to 80% by mass, relative to the total mass of composition 2, in terms of the dispersion stability of the specific PTFE particles.

[0120] (Emulsifiers that do not contain fluorine atoms) Details of the emulsifier that does not contain fluorine atoms are as described above, so their explanation will be omitted. The content of the emulsifier that does not contain fluorine atoms is preferably more than 0% by mass and 5.0% by mass or less, more preferably 0.005 to 4.5% by mass, and even more preferably 0.010 to 4.0% by mass, based on the total mass of composition 2. The details of the ionic emulsifier that does not contain fluorine atoms are as described above, so the explanation will be omitted. The content of the ionic emulsifier that does not contain fluorine atoms is preferably more than 0% by mass and 5.0% by mass or less, more preferably 0.005 to 4.5% by mass, and even more preferably 0.010 to 4.0% by mass, based on the total mass of composition 2. The details of the nonionic emulsifier that does not contain fluorine atoms are as described above, so the explanation will be omitted. The content of the nonionic emulsifier that does not contain fluorine atoms is preferably 5.0% by mass or less, more preferably 2.0% by mass or less, and even more preferably 1.5% by mass or less, based on the total mass of composition 2. The lower limit of the content of the nonionic emulsifier that does not contain fluorine atoms is 0% by mass.

[0121] Composition 2 may contain other components that may be included in the above-described composition.

[0122] <Other processes> The method for producing this composition may include steps other than steps 1 and 2. Specific examples of these other steps include an impurity removal step, which involves removing impurities from the composition. If the method for producing this composition does not include step 2 but includes an impurity removal step, the impurity removal step is performed after step 1. Furthermore, if the method for producing this composition includes step 2 and includes an impurity removal step, the impurity removal step may be performed between step 1 and step 2, after step 2, or at both of these timings. The method for removing impurities in the impurity removal process is not particularly limited, but examples include contacting composition 1 or composition 2 with an ion exchange resin (e.g., anion exchange resin, cation exchange resin) or an adsorbent (e.g., zeolite, activated carbon).

[0123] [Mixture] A first embodiment of the mixture of the present invention comprises the above-described composition (dust suppression treatment agent composition) and a dust-generating substance. Hereinafter, the mixture according to the first embodiment will also be referred to as "Mixture 1". Furthermore, a second embodiment of the mixture of the present invention includes the above-mentioned specific PTFE particles and a dust-generating substance. Hereinafter, the mixture according to the second embodiment will also be referred to as "Mixture 2". The details of the mixture will be described below for each embodiment.

[0124] [Mixture 1] Since mixture 1 contains this composition, dust generation from dust-generating substances is less likely. Specifically, by applying known compression or shearing treatments to mixture 1, the fibrillation of specific PTFE particles in mixture 1 is promoted, thereby suppressing the generation of dust from dust-generating substances.

[0125] <Dust suppression treatment agent composition> The present composition (i.e., the dust suppression treatment agent composition of the present invention) is as described above. The content of this composition is preferably 0.01 to 20% by mass, more preferably 0.01 to 10% by mass, even more preferably 0.02 to 8% by mass, and particularly preferably 0.03 to 5% by mass, based on the total mass of mixture 1.

[0126] <Dusting substances> Dusting substances are solid particulate matter that is dispersed and suspended in the air, generating dust. The dust-generating substance may be an inorganic compound, an organic compound, or may contain both. Specific examples of dust-generating substances include powders of various cements; mineral powders such as slaked lime, quicklime powder, silica, fluorite, calcium carbonate, dolomite, magnesite, and talc; clay mineral powders such as kaolin and bentonite; slag powder, a by-product of the manufacturing process of metals such as steel or non-ferrous metals; combustion ash powder from coal and waste; metal powders; gypsum powder; carbon black; activated carbon; ceramic powders such as metal oxides; and powders of pigments. The content of dust-generating substances is preferably 80 to 99.9% by mass, more preferably 85 to 99% by mass, and even more preferably 90 to 98.5% by mass, based on the total mass of mixture 1.

[0127] <Other> It is preferable that mixture 1 substantially does not contain emulsifiers containing fluorine atoms. Details of emulsifiers containing fluorine atoms are as described above. "Substantially free of emulsifiers containing fluorine atoms" means that the content of emulsifiers containing fluorine atoms is 50 ppm by mass or less relative to the solid content of mixture 1, preferably 10 ppm by mass or less, more preferably 1 ppm by mass or less, even more preferably 25 ppb by mass or less, and particularly preferably 10 ppb by mass or less. The lower limit is 0 ppb by mass.

[0128] Mixture 1 may contain an emulsifier that does not contain fluorine atoms. Specific examples of emulsifiers that do not contain fluorine atoms include ionic emulsifiers that do not contain fluorine atoms, and nonionic emulsifiers that do not contain fluorine atoms, as detailed above. If mixture 1 contains an emulsifier that does not contain fluorine atoms, the content of the emulsifier that does not contain fluorine atoms is preferably more than 0% by mass and 0.015% by mass or less, preferably 0.0015 to 0.009% by mass, more preferably 0.0015 to 0.006% by mass, and even more preferably 0.0025 to 0.006% by mass, relative to the solid content mass of mixture 1. If mixture 1 contains an ionic emulsifier that does not contain fluorine atoms, the content of the ionic emulsifier that does not contain fluorine atoms is preferably more than 0% by mass and 0.015% by mass or less, more preferably 0.0015 to 0.009% by mass, and even more preferably 0.0015 to 0.006% by mass, relative to the solid content mass of mixture 1. The content of the nonionic emulsifier that does not contain fluorine atoms is preferably 0.015% by mass or less, more preferably 0.005% by mass or less, and even more preferably 0.003% by mass or less, relative to the solid content of mixture 1. The lower limit of the content of the nonionic emulsifier that does not contain fluorine atoms is 0% by mass.

[0129] <Method for producing mixture 1> Mixture 1 is obtained by mixing the present composition with a dust-generating substance, and the method of its production is not particularly limited; known methods can be employed.

[0130] [Mixture 2] Since mixture 2 contains specific PTFE particles, it is less likely to generate dust from dust-generating substances. Specifically, by applying known compression or shearing treatments to mixture 2, the fibrillation of the specific PTFE particles in mixture 2 is promoted, thereby suppressing the generation of dust from dust-generating substances.

[0131] <Specific PTFE particles> The specific PTFE particles are as described above. The content of specific PTFE particles is preferably 0.02 to 0.50% by mass, more preferably 0.03 to 0.30% by mass, and even more preferably 0.05 to 0.20% by mass, based on the total mass of mixture 2.

[0132] <Dusting substances> The dust-generating substances in mixture 2 are the same as those in mixture 1. The content of dust-generating substances is preferably 99.50 to 99.98% by mass, more preferably 99.70 to 99.97% by mass, and even more preferably 99.80 to 99.95% by mass, based on the total mass of mixture 2.

[0133] <Other> Mixture 2 preferably contains substantially no aqueous medium. Specific examples of aqueous mediums include the aqueous medium contained in the above-described composition. "Substantially free of aqueous media" means that the content of aqueous media is 0.001% by mass or less of the total mass of mixture 2, with 0% by mass being more preferable.

[0134] <Method for producing mixture 2> The method for producing mixture 2 is not particularly limited, and known methods can be employed. For example, one method is to mix the above-mentioned composition with a dust-generating substance to remove the aqueous medium derived from the above-mentioned composition. The method for removing the aqueous medium is not particularly limited, but examples include drying by natural drying or heating. [Examples]

[0135] Hereinafter, the present invention will be described in detail with examples. Examples 1 to 2 are examples, and Examples 3 to 4 are comparative examples. However, the present invention is not limited to these examples.

[0136] [Measurement and Evaluation Methods] <Average Particle Size of PTFE Particles> Using the composition containing PTFE particles obtained in each example as a sample, the average particle size (volume basis, D50) of the PTFE particles was measured using a laser diffraction / scattering particle size distribution measuring device (Otsuka Electronics Co., Ltd., ELSZ).

[0137] <Standard Specific Gravity of PTFE Particles> The standard specific gravity was measured in accordance with ASTM D4895-04. Weighed 12.0 g of the sample (PTFE particles), and held it at 34.5 MPa for 2 minutes in a cylindrical mold with an inner diameter of 28.6 mm. This was placed in an oven at 290 °C and heated at 120 °C / hr. Further, after holding at 380 °C for 30 minutes, it was cooled at 60 °C / hr and held at 294 °C for 24 minutes. After holding the sample in a desiccator at 23 °C for 12 hours, the specific gravity value of the sample with respect to water at 23 °C was measured, and this was taken as the standard specific gravity (hereinafter, also referred to as "SSG"). The smaller the value of SSG, the larger the molecular weight.

[0138] <Melting Point of PTFE Particles> The melting point (Tm) was measured using a DSC8500 manufactured by PerkinElmer, which had been temperature-calibrated in advance using indium and zinc as standard samples. Specifically, 10 mg of the sample for measurement was weighed into an aluminum sample pan, and the melting point was determined from the endothermic peak when the sample was heated to 380 °C at a heating rate of 10 °C / min under an air atmosphere.

[0139] <Aspect Ratio of PTFE Particles> The compositions obtained in each example were diluted to a solid content concentration of 0.2% by mass to prepare sample dispersions. The sample dispersions were dropped onto a substrate and dried. The samples were then deposited with Pt, and at a magnification of 20,000x using a scanning electron microscope (SEM, JEOL JSM-IT700HR InTouchScope), a field of view was randomly selected so that the particles did not overlap, and at least four observation images were saved. From the observation images, more than 800 elliptical particles were selected, and the brightness was adjusted using the image analysis software "MultiImage Tool". The particles and substrate were then binarized, and the aspect ratio of the long side to the short side of the particles was analyzed. The average of the aspect ratios of each particle was taken as the aspect ratio of the PTFE particles.

[0140] <Emulsifier content> The amounts of emulsifiers containing fluorine atoms and emulsifiers without fluorine atoms were calculated from the amount used in the preparation.

[0141] <Fibrillation performance> Using a tubular pump fitted with a Tygon tube with an outer diameter of 7.9 mm and an inner diameter of 4.8 mm, 100 mL of each example of Composition 2 (Compositions 2-1 to 2-4) in a 200 mL beaker was continuously circulated for 2 hours at room temperature (23°C) at a flow rate of 300 mL per minute. After completion, the solid was collected using a 200-mesh nylon filter, and its mass was measured after drying at 120°C for 1 hour. Based on the measured mass of the solid, the fibrillation performance of the PTFE particles was evaluated according to the following criteria. It was determined that a larger amount of solid was more easily fibrillated, and therefore the fibrillation performance was good. Here, if the fibrillation performance is good, when shear treatment is applied to the mixture of composition 2 and the dust-generating substance, the PTFE particles in composition 2 will be more easily fibrillated, and thus it can be said that it has an excellent effect in suppressing the scattering of dust-generating substances. A: The amount of solid material is 2g or more. B: The amount of solid material is less than 2g.

[0142] [Manufacturing of raw material liquid A1] Ultrapure water (319.5 kg) and PMVE (6.01 kg) were charged into a 430 L stainless steel pressure reactor equipped with stirring blades and baffles, and the temperature was raised to 90°C while stirring at 107 rpm. TFE was injected under pressure until the reactor pressure reached 1.37 MPaG, and an aqueous solution of ammonium persulfate (APS) (8.09 mass%, 1 kg) was added to start the reaction. As the reaction started, the pressure inside the reactor decreased, so TFE was added to maintain a constant pressure. After injecting 1.2 kg of TFE, the reactor was cooled and the polymerization reaction was terminated. The polymerization time was 49 minutes. After recovering the remaining gas in the reactor, nitrogen was injected under pressure to 0.10 MPaG while stirring at 40 rpm, and the temperature was raised to 90°C. After heating the reactor for 3 hours, it was cooled and the liquid was drained. This liquid was designated as raw material liquid A1. After freezing and condensing the raw material liquid A1, it was filtered, and the resulting fluorine-containing polymer A1 was analyzed by NMR. The result showed that the TFE units / PMVE units = 52 / 48 (molar ratio).

[0143] [Manufacturing of raw material liquid B1] Dowex Monosphere 650C (DuPont, cation exchange resin, 20g) was added to raw material solution A1 (490g). After 60 minutes of stirring, the raw material solution and ion exchange resin were filtered off. SA10AOH (Mitsubishi Chemical Corporation, anion exchange resin, 20g) was added to the filtered raw material solution. After 60 minutes of stirring, the raw material solution and ion exchange resin were filtered off to obtain raw material solution B1. The content of fluorine-containing polymer A1 was 0.7% by mass relative to the total mass of raw material solution B1.

[0144] [Example 1] Ultrapure water (6.6 kg), raw material solution B1 (52 kg), and paraffin wax (1.5 kg) were charged into a 100 L stainless steel pressure reactor equipped with a stirring blade and baffles to obtain aqueous dispersion B1-1 (corresponding to the aqueous dispersion used in step 1 described above). The concentration of the emulsifier containing fluorine atoms was 0 ppm by mass relative to the total mass of fluorine-containing polymer A1 in aqueous dispersion B1-1. The obtained aqueous dispersion B1-1 was heated to 65°C while being stirred at 95 rpm. TFE was injected under pressure until the reactor pressure reached 1.40 MPaG, and a solution of 14 g of disuccinic acid peroxide (concentration 80% by mass, remainder water) dissolved in 2 L of warm water was poured into the reactor to start polymerization. As polymerization began, the pressure inside the reactor decreased, so TFE was added to maintain a constant pressure. After injecting 15.8 kg of TFE, the reactor was cooled to terminate the polymerization reaction and obtain composition 1-1 (corresponding to composition 1 obtained in step 1 described above). The polymerization time was 184 minutes. Composition 1-1 is a dispersion in which PTFE particles (average particle size 172 nm) containing fluorine-containing polymer A1 and PTFE are dispersed in an aqueous medium, and the solid content concentration was 20.3% by mass. A portion of the obtained composition 1-1 was adjusted to 20°C and stirred to agglomerate the PTFE particles, thereby obtaining PTFE powder. Next, this PTFE powder was dried at 200°C. The obtained PTFE powder (PTFE particles) had an SSG of 2.15, a melting point of 343°C, and an aspect ratio of 1.45. Composition 2-1 (corresponding to Composition 2 obtained in step 2 above) was obtained by adding each component to Composition 1-1 such that the content of ammonium laurate relative to the mass of PTFE particles in Composition 1-1 was 1680 ppm by mass and the content of triethanolamine lauryl sulfate was 630 ppm by mass. No by-product fluorine oligomers were detected in the obtained Composition 2-1. Furthermore, PTFE powder was obtained in the same manner as the method for obtaining PTFE powder using composition 1-1, except that composition 2-1 was used instead of composition 1-1. The physical properties (SSG, melting point, aspect ratio) of the obtained PTFE powder (PTFE particles) were the same as those of the PTFE powder obtained using composition 1-1. In addition, the average particle size of the PTFE particles measured using composition 2-1 instead of composition 1-1 was the same as the average particle size of the PTFE particles measured using composition 1-1.

[0145] [Example 2] Composition 2-2 (corresponding to Composition 2 obtained in step 2 described above) was obtained in the same manner as in Example 1, except that each component was added to Composition 1-1 such that the content of ammonium laurate relative to the mass of PTFE particles was 2800 ppm by mass and the content of triethanolamine lauryl sulfate was 1050 ppm by mass. Furthermore, no by-product fluorine oligomers were detected in the obtained Composition 2-2. Furthermore, PTFE powder was obtained in the same manner as the method for obtaining PTFE powder using composition 1-1, except that composition 2-2 was used instead of composition 1-1. The physical properties (SSG, melting point, aspect ratio) of the obtained PTFE powder (PTFE particles) were the same as those of the PTFE powder obtained using composition 1-1. In addition, the average particle size of the PTFE particles measured using composition 2-2 instead of composition 1-1 was the same as the average particle size of the PTFE particles measured using composition 1-1.

[0146] [Example 3] Composition 1-3 is an aqueous dispersion containing PTFE particles manufactured according to the method described in paragraphs 0055 and 0056 of Japanese Patent No. 5141256. Composition 1-3 is a dispersion in which PTFE particles (average particle size 260 nm) are dispersed in an aqueous medium, has a solid content concentration of 25.0% by mass, and contains CF3CF2OCF2CF2OCF2COONH4, which is an emulsifier having a fluorine atom. A portion of the obtained compositions 1-3 was adjusted to 20°C and stirred to agglomerate the PTFE particles, thereby obtaining PTFE powder. Next, this PTFE powder was dried at 200°C. The obtained PTFE powder had an SSG of 2.21, a melting point of 347°C, and an aspect ratio of 1.65. Composition 2-3 was obtained in the same manner as in Example 1, except that composition 1-3 was used instead of composition 1-1. The content of the emulsifier containing fluorine atoms in composition 2-3 was 58 ppm by mass relative to the content of PTFE particles in composition 2-3. Furthermore, PTFE powder was obtained in the same manner as the method for obtaining PTFE powder using composition 1-3, except that composition 2-3 was used instead of composition 1-3. The physical properties (SSG, melting point, aspect ratio) of the obtained PTFE powder (PTFE particles) were the same as those of the PTFE powder obtained using composition 1-3. In addition, the average particle size of the PTFE particles measured using composition 2-3 instead of composition 1-3 was the same as the average particle size of the PTFE particles measured using composition 1-3.

[0147] [Example 4] Composition 1-4 was an aqueous dispersion containing PTFE particles prepared according to the method described in paragraphs 0100 and 0101 of WO2021 / 085470. Composition 1-4 is a dispersion in which PTFE particles (average particle size 240 nm) are dispersed in an aqueous medium, and has a solid content concentration of 11% by mass. The PTFE particles in Composition 1-4 are particles obtained by polymerizing TFE in the presence of an i-butyl methacrylate polymer. A portion of the obtained compositions 1-4 was adjusted to 20°C and stirred to agglomerate the PTFE particles, thereby obtaining PTFE powder. Next, this PTFE powder was dried with an aqueous ammonium carbonate solution at 275°C. The obtained PTFE powder had an SSG of 2.20, a melting point of 337°C, and an aspect ratio of 1.97. Composition 2-4 was obtained in the same manner as in Example 1, except that composition 1-4 was used instead of composition 1-1. Furthermore, PTFE powder was obtained in the same manner as the method for obtaining PTFE powder using composition 1-4, except that composition 2-4 was used instead of composition 1-4. The physical properties (SSG, melting point, aspect ratio) of the obtained PTFE powder (PTFE particles) were the same as those of the PTFE powder obtained using composition 1-4. In addition, the average particle size of the PTFE particles measured using composition 2-4 instead of composition 1-4 was the same as the average particle size of the PTFE particles measured using composition 1-4.

[0148] [Table 1]

[0149] As shown in Table 1, compositions containing PTFE particles with an aspect ratio of less than 1.65 demonstrated excellent fibrillation performance of the PTFE particles (Examples 1-2). Therefore, it can be said that when a shearing treatment is applied to a mixture of the compositions of Examples 1-2 and a dust-generating substance, the PTFE particles in the composition become more easily fibrillated, thus sufficiently suppressing the scattering of the dust-generating substance.

[0150] Furthermore, the disclosure of Japanese Patent Application No. 2024-177164, filed on 9 October 2024, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually noted to be incorporated by reference.

Claims

1. A dust suppression treatment agent composition for dust-generating substances, The dust suppression treatment agent composition comprises an aqueous medium and polytetrafluoroethylene particles. A dust suppression treatment agent composition characterized in that the aspect ratio of the polytetrafluoroethylene particles is less than 1.

65.

2. A dust suppression treatment agent composition according to claim 1, which substantially does not contain an emulsifier having a fluorine atom.

3. The dust suppression treatment composition according to claim 1, wherein the content of a nonionic emulsifier that does not contain fluorine atoms is 5.0% by mass or less with respect to the total mass of the dust suppression treatment composition.

4. The dust suppression treatment composition according to claim 1, wherein the content of the polytetrafluoroethylene particles is 10 to 70% by mass of the total mass of the dust suppression treatment composition.

5. A mixture characterized by comprising a dust suppression treatment agent composition according to any one of claims 1 to 4 and a dust-generating substance.

6. It contains polytetrafluoroethylene particles and a dust-generating substance. A mixture characterized in that the aspect ratio of the polytetrafluoroethylene particles is less than 1.65.

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