Fluorine-containing resin composition and method for producing the same

Abstract

The present invention provides a fluororesin composition that can be used as a paint. [Solution] A fluorine-containing resin composition comprising 95% by mass or more of a fluorine-containing copolymer (A) containing monomers having functional groups as constituent units, and 100 to 3000 ppm of water (B) as constituent components.

Description

Technical Field

[0001] The present disclosure relates to a fluororesin composition and a method for producing the same.

Background Art

[0002] Paints containing fluororesins are used in many fields because they have excellent properties such as weather resistance, stain resistance, corrosion resistance, chemical resistance, solvent resistance, and heat resistance. As such paints, those in the form of solid fluororesins that are mixed with a solvent during paint formation are being studied in distribution.

[0003] Advantages of distributing in the form of solid fluororesins include cost reduction due to their small volume during distribution and storage, and the ability to appropriately select and use solvents according to the application, substrate, and regulations.

[0004] Patent Documents 1 to 3 disclose removing a solvent by drying in an organic solvent solution of a fluororesin for such purposes.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0006] An object of the present disclosure is to provide a fluororesin composition that can be used as a paint.

Means for Solving the Problems

[0007] This disclosure relates to a fluorine-containing copolymer (A) containing monomers having functional groups as constituent units, at a concentration of 95% by mass or more, and Water (B) 100~3000ppm This is a fluororesin composition characterized by containing as a constituent component.

[0008] The above fluororesin composition is, It is preferable to further contain 0.1 to 2% by mass of an organic solvent (C). The above-mentioned fluorine-containing polymer (A) preferably contains monomers having hydroxyl groups as constituent units, and the hydroxyl value of the fluorine-containing copolymer is preferably 45 mgKOH / g or more. The above-mentioned fluorine-containing copolymer (A) is preferably a fluorine-containing copolymer comprising a fluoroolefin unit and at least one monomer unit selected from the group consisting of vinyl esters, vinyl ethers, (meth)acrylic esters, and allyl ethers.

[0009] The above-mentioned fluorine-containing copolymer (A) contains monomers having an acid value as constituent units, and it is preferable that the acid value of the above-mentioned fluorine-containing copolymer (A) is 1.0 mg KOH / g or more. The above-mentioned fluorine-containing copolymer (A) preferably has a weight-average molecular weight (Mw) of 50,000 or less on a polystyrene basis, as measured by GPC.

[0010] The above-mentioned fluorine-containing copolymer (A) is preferably soluble in parachlorobenzotrifluoride, and its rotational viscosity at 25°C, measured with a B-type viscometer when dissolved in parachlorobenzotrifluoride to a solid content concentration of 50% by mass, is preferably 10,000 mPa·s or less.

[0011] The organic solvent (C) preferably contains at least one selected from the group consisting of n-butyl acetate, ethyl acetate, xylene, toluene, methyl ethyl ketone, methyl isobutyl ketone, acetone, and alcohols having 4 or fewer carbon atoms.

[0012] The fluorine-containing coating composition of this disclosure is preferably in the form of flakes, powder, or pellets at a temperature of 25°C. In terms of pellet shape, it is preferable that the average major diameter is 20 mm or less and the average aspect ratio is 2 or less. The fluorine-containing coating compositions disclosed herein are The above fluorine-containing copolymer (A) is contained in a content of 99.0 to 99.9% by mass. The above water (B) is contained in a concentration of 100 to 3000 ppm. It contains an organic solvent (C) at a content of 0.1 to 1.0% by mass. The above fluorine-containing copolymer (A) is Fluoroolefin units and At least one monomer unit selected from the group consisting of vinyl monomers having a hydroxyl group and vinyl monomers having a carboxyl group, Preferably, it contains at least one monomer unit selected from the group consisting of alkyl vinyl esters and alkyl vinyl ethers.

[0013] The present disclosure also relates to a method for producing a fluororesin composition (A) according to claim 1 or 2, characterized by a step of desolventing a fluororesin solution obtained by dissolving the above-mentioned fluororesin copolymer (A) in an organic solvent (C) at a heat transfer medium temperature of 150°C or lower until the organic solvent (C) is reduced to 2% by mass or less, and then removing water so that the water content is 100 to 3000 ppm. [Effects of the Invention]

[0014] The present disclosure relates to a fluororesin composition in which the solvent used during polymerization is sufficiently removed and the water content is further reduced, as well as a method for producing the same. [Modes for carrying out the invention]

[0015] Hereinafter, the present disclosure will be described in detail. In the present disclosure, the "unit derived from a monomer" may be simply referred to as a "monomer unit". The present disclosure relates to a fluororesin composition having a reduced water content within a predetermined range. For the purpose as described above, it is known to dry an organic solvent solution of a fluorine-containing copolymer in order to obtain a solid fluorine-containing copolymer that does not contain a solvent.

[0016] However, when such a fluororesin composition is dissolved in a solvent and used as a paint, if water remains in the composition, the performance of the paint may deteriorate due to the remaining water.

[0017] Specifically, if water remains, when it is made into a curable paint, the crosslinking density of the paint film may decrease due to the reaction between the curing agent and water.

[0018] In order to reduce such problems, it is desirable to sufficiently remove water. However, if the heating time is lengthened to remove the solvent, the resin may be polymerized, which is a problem in resins that are easily polymerized by heating. Also, the problem of blocking is likely to occur.

[0019] Furthermore, there may be cases where it is necessary to make the fluororesin composition into a pellet shape or a flake shape. The pellet-shaped resin composition has the merit of having a large surface area and good solvent solubility. The flake-shaped resin composition has the merit of excellent blocking resistance by suppressing the contact area. However, in order to make it into a pellet shape or a flake shape, it is desirable to melt the dried resin and rapidly cool and cut it.

[0020] In this process, it is necessary to rapidly cool the molten resin. However, there is a problem that the water content in the resin tends to increase due to the rapid cooling of the resin. In particular, when the resin has a functional group with high affinity for water, such a problem becomes particularly important.

[0021] From the above perspective, reducing the water content is important. The fluororesin composition of this disclosure is characterized in that the amount of water it contains is within a specific range.

[0022] (moisture content) The fluororesin composition disclosed herein has a moisture content (water (B) content in the fluororesin composition) within the range of 100 to 3000 ppm. This moisture content is measured by the Karl Fischer method. The upper limit of the above moisture content is preferably 3000 ppm or less, and more preferably 2000 ppm or less. While a lower moisture content is preferable, achieving a moisture content of 100 ppm or less would require heating to 30°C or higher, which can cause resin blocking. Therefore, the above range is preferable because it eliminates the need for such heating to remove moisture.

[0023] (Fluorine-containing copolymer (A)) The composition of this disclosure contains a fluorine-containing copolymer (A) which comprises monomers having functional groups as constituent units. The fluorine-containing copolymer (A) has excellent properties such as weather resistance and solvent resistance, and this disclosure relates to a composition that can exhibit the properties of such a fluorine-containing copolymer.

[0024] The above-mentioned fluorine-containing copolymer (A) has structural units (b1) derived from fluoroolefins (hereinafter sometimes referred to as "fluoroolefin units"). A fluoroolefin unit (b1) refers to a structure derived from an unsaturated compound containing a fluorine atom. Specifically, examples include tetrafluoroethylene, chlorotrifluoroethylene, trifluoroethylene, vinylidene fluoride, hexafluoropropylene, and pentafluoropropylene, and these can be appropriately selected depending on the properties required for the coating film and the combination with copolymer components. In addition, one or more of these fluoroolefins can be used. Among these, it is preferable to use at least one (e.g., one or two) selected from structural units derived from tetrafluoroethylene and chlorotrifluoroethylene, and in particular, it is preferable to use structural units derived from tetrafluoroethylene.

[0025] The above-mentioned fluorine-containing copolymer (A) contains monomers having functional groups as constituent units. The above-mentioned functional groups are not particularly limited and may include monomers having hydroxyl groups, carboxyl groups, amide groups, amino groups, mercapto groups, glycidyl groups, or isocyanate groups, hydrolyzable silyl groups, etc. When the functional group is used as a curable composition, it is preferable that it acts as a curing functional group, with hydroxyl groups being the most preferred. When the fluorine-containing resin composition of this disclosure is used in a paint, it is preferable that such a functional group acts as a reactive functional group that reacts with the curing agent.

[0026] Examples of monomers having functional groups include vinyl monomers having functional groups, and more specifically, the following can be listed. Examples of monomers containing hydroxyl groups (hydroxyl group-containing monomers) include hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether, and hydroxycyclohexyl vinyl ether; esters of hydroxyalkyl carboxylic acids with vinyl alcohols such as vinyl hydroxyacetate, vinyl hydroxypropioate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate, and vinyl hydroxycyclohexanecarboxylate; and hydroxyalkyl allyl ethers such as hydroxyethyl allyl ether, hydroxypropyl allyl ether, hydroxybutyl allyl ether, hydroxyisobutyl allyl ether, and hydroxycyclohexyl allyl ether. Examples include hydroxyalkyl allyl esters such as hydroxyethyl allyl ester, hydroxypropyl allyl ester, hydroxybutyl allyl ester, hydroxyisobutyl allyl ester, and hydroxycyclohexyl allyl ester; hydroxyalkyl esters of acrylic acid or methacrylic acid such as 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and hydroxypropyl methacrylate; unsaturated alcohols such as 3-methyl-3-buten-1-ol (isoprenol), 3-methyl-2-buten-1-ol, 2-methyl-3-buten-2-ol, 2-methyl-2-buten-1-ol, and 2-methyl-3-buten-1-ol; and one or more of these partially fluorine-substituted compounds. Examples of monomers having a carboxyl group include crotonic acid, undecylenic acid, (meth)acrylic acid, and carboxylalkyl allyl ethers. Examples of monomers having an amide group include (meth)acrylamide and N-methylolacrylamide. Examples of monomers having an amino group include aminoalkyl vinyl ethers and aminoalkyl allyl ethers. Examples of monomers having a glycidyl group include glycidyl (meth)acrylate, glycidyl vinyl ether, and glycidyl allyl ether. Examples of monomers having an isocyanate group include vinyl isocyanate and isocyanate ethyl acrylate. Among these, hydroxyalkyl vinyl ethers, unsaturated alcohols, and carboxylalkyl allyl ethers are preferred, and among these, 4-hydroxybutyl vinyl ether, 2-hydroxyethyl vinyl ether, isoprenol, crotonic acid, and undecylenic acid are preferred.

[0027] The above-mentioned fluorine-containing copolymer (A) preferably contains monomers having the above-mentioned functional group in a proportion of 1 to 50 mol%. The lower limit is more preferably 5 mol%. The upper limit is even more preferably 40 mol%.

[0028] The fluorine-containing copolymer (A) described above preferably has a hydroxyl value of 45 mgKOH / g or more. This range is preferable because, when used in a curable paint, it provides sufficient crosslinking reaction sites, allowing for good coating film properties even when the molecular weight of the polymer is reduced. The hydroxyl value can be adjusted to a predetermined value by controlling the proportion of hydroxyl group-containing monomers used. A hydroxyl value of 50 mgKOH / g or more is more preferable, and 56 mgKOH / g or more is even more preferable. The upper limit of the hydroxyl value is not particularly limited, but for example, it can be 150 mgKOH / g or less.

[0029] The fluorine-containing copolymer (A) preferably further contains at least one monomer unit (for example, one, two, three, or four) selected from the group consisting of vinyl esters, vinyl ethers, (meth)acrylic esters, and allyl ethers. Such monomers are preferable because they lower the melting and softening points of fluorine-containing copolymers, further improving paintability, and impart appropriate physical properties to the coating film, such as hardness, flexibility, gloss, solvent solubility, curing agent compatibility, and adhesion.

[0030] The following are specific examples of vinyl esters, vinyl ethers, (meth)acrylic esters, and allyl ethers that can be used as described above. Examples of the vinyl ethers mentioned above include alkyl vinyl ethers, and more specifically, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, and the like. The alkyl group of the alkyl vinyl ether may be linear or cyclic. Examples of the vinyl esters mentioned above include alkyl vinyl esters (esters of alkyl carboxylic acid and vinyl alcohol), and more specifically, vinyl neononanoate, vinyl versatate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl valerate, vinyl cyclohexanecarboxylate, vinyl benzoate, and p-t-butylbenzoate vinyl. The alkyl group of the alkyl vinyl ester may be linear or cyclic. Examples of the above-mentioned (meth)acrylic esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, (iso)butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of the allyl ethers mentioned above include alkyl allyl ethers, and more specifically, ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether, and cyclohexyl allyl ether. The alkyl group of the alkyl allyl ether may be linear or cyclic.

[0031] Furthermore, in addition to the monomers described above, the monomers may also have constituent units based on monomers having carboxyl groups. Examples of monomers having the carboxyl group mentioned above include α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, succinic acid, succinic anhydride, fumaric acid, fumaric anhydride, crotonic acid, maleic acid, and maleic anhydride, as well as fluorine-substituted monomers such as perfluorobutenoic acid.

[0032] The above-mentioned fluorine-containing copolymer (A), when it contains structural units based on monomers having an acid value (for example, monomers having a carboxyl group), preferably has an acid value of 1.0 mg KOH / g or higher. Having such an acid value is desirable in terms of improving the dispersibility of pigments and the stability of paints. The above acid value can be set to a predetermined value by adjusting the proportion of monomers having a carboxyl group used. The above acid value is more preferably 1.5 mg KOH / g or higher, and even more preferably 2.0 mg KOH / g or higher. The upper limit of the above acid value is not particularly limited, but from the viewpoint of water resistance, weather resistance, and thermal stability, it can be, for example, 30 mg KOH / g or less. When it contains structural units based on monomers having a carboxyl group, the content of structural units based on monomers having a carboxyl group is preferably 0.1 mol% or more, and more preferably 0.5 mol% or more, relative to the total amount of structural units constituting the fluorine-containing copolymer (A). Furthermore, the content of constituent units based on monomers having carboxyl groups is preferably 10 mol% or less, and more preferably 5 mol% or less, relative to the total amount of structural units constituting the fluorine-containing copolymer (A). In terms of suppressing high molecular weight formation, it is preferable that the content of constituent units based on monomers having carboxyl groups be within the above range.

[0033] The fluorine-containing copolymer (A) described above may have constituent units derived from monomers other than those described above, to the extent that it does not impair the purpose of this disclosure.

[0034] Examples of constituent units derived from monomers other than those mentioned above include non-fluorinated olefins, acrylic esters, and allyl ethers. Examples of the non-fluorinated olefins mentioned above include ethylene, propylene, n-butene, and isobutene. Examples of the above-mentioned acrylic esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, (iso)butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. Examples of the above-mentioned allyl ethers include ethyl allyl ether, propyl allyl ether, butyl allyl ether, isobutyl allyl ether, and cyclohexyl allyl ether. One or more of these may be used.

[0035] When copolymerizing the above-mentioned non-fluorinated olefin, its content is preferably 0 to 50 mol% of the total fluorine-containing copolymer. The upper limit is preferably less than 45 mol%, more preferably 40 mol% or less.

[0036] When copolymerizing the above-mentioned acrylic esters or allyl ether esters, their content is preferably 0 to 5 mol% of the total fluorine-containing copolymer.

[0037] In the above-mentioned fluorine-containing copolymer (A), the fluoroolefin units are preferably 10 to 60 mol% of the total polymer units constituting the polymer. By keeping the amount within this range, a composition with excellent weather resistance and solvent resistance can be obtained. The lower limit of the above blending amount is more preferably 25 mol%, and even more preferably 35 mol%. The upper limit of the above blending amount is more preferably 50% by mass.

[0038] In the above fluorine-containing copolymer (A), it is preferable that structural units (b2) derived from at least one (e.g., one, two, three, or four) selected from the group consisting of vinyl esters, vinyl ethers, allyl ethers, and hydroxyl group-containing unsaturated compounds constitute 40 to 90 mol% of the total polymerization units constituting the polymer. By keeping it within this range, a composition with excellent solvent solubility and further excellent pigment dispersibility can be obtained. The lower limit of the above blending amount is more preferably 45 mol%, and even more preferably 50 mol%. The upper limit of the above blending amount is more preferably 75 mol%, and even more preferably 65 mol%.

[0039] The above-mentioned fluorine-containing copolymer preferably has a weight-average molecular weight (Mw) of 50,000 or less, measured on a polystyrene basis by GPC. This range is preferable because it allows for excellent solubility in solvents and enables high solid differentiation. The weight-average molecular weight here refers to the value measured by the measurement method described in the examples.

[0040] The weight-average molecular weight is more preferably 45,000 or less, and even more preferably 40,000 or less. The lower limit of the weight-average molecular weight is not particularly limited, but for example, it is preferably 5,000 from the viewpoint of weather resistance and flexibility.

[0041] The fluorine-containing resin composition of this disclosure contains 95% by mass or more of the fluorine-containing copolymer (A). That is, it basically consists of the fluorine-containing copolymer (A), satisfies the predetermined solvent and water content described above, and may not contain any other components.

[0042] Other components include, for example, impurities from the polymerization of the fluorine-containing copolymer (A). Examples of impurities include the presence of polymerization catalyst residue, unreacted monomers, and raw material impurity residues. The amount of fluorine-containing copolymer (A) in the fluorine-containing resin composition is measured by the weight residue after drying 2 g of resin in an electric furnace at 150°C for 1 hour. The content is more preferably 97% by mass or more, even more preferably 98% by mass or more, and even more preferably 99.0% by mass or more. Since water (B) and organic solvent (C) are sufficiently removed, a higher amount of fluorine-containing copolymer (A) in the fluorine-containing resin composition is preferable, but for example, 99.9% by mass or less is acceptable.

[0043] (Organic solvent (C)) In the fluororesin composition of this disclosure, the content of the organic solvent is preferably 0.1 to 2% by mass. When the organic solvent content is 2% by mass, it is preferable in that it suppresses the generation of odor, a decrease in the blocking properties of the resin, inability to maintain its shape through plasticization, and difficulty in dissolving in the solvent during use. It is more preferable that the organic solvent content is 1.0% by mass or less. Although the amount of organic solvent is better the less, in order to make it 0.1% by mass or less, it becomes necessary to raise the temperature during solvent removal, which can cause excessive heat to be applied to the resin, leading to an increase in the polymer molecular weight and discoloration of the resin. Therefore, it is preferable to keep it within the above range in that it eliminates the need to remove the organic solvent by heating. Solution polymerization, in which a reaction is carried out in an organic solvent, is a well-known and common method in the manufacture of resins. In order to obtain a solid fluororesin composition, it is necessary to remove the organic solvent used in such solution polymerization.

[0044] In this disclosure, "organic solvent" means a volatile organic compound, which has a boiling point and is in a liquid state at room temperature. The above organic solvent is not particularly limited and may include those commonly used as solvents in the chemical field. Specifically, examples include esters such as ethyl acetate, n-butyl acetate, t-butyl acetate, isopropyl acetate, isobutyl acetate, cellosolve acetate, methoxypropyl acetate, and propylene glycol methyl ether acetate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; cyclic ethers such as tetrahydrofuran and dioxane; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; aromatic hydrocarbons such as xylene, toluene, solvent naphtha, and coal tar naphtha; glycol ethers such as propylene glycol methyl ether and ethyl cellosolve; diethylene glycol esters such as carbitol acetate; aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, n-dodecane, and mineral spirits; alcohols with 4 or fewer carbon atoms such as methanol, ethanol, propanol, and butanol; and mixed solvents thereof.

[0045] The amount of organic solvent (C) in the fluororesin composition of this disclosure refers to the value obtained by subtracting the above-mentioned water content from the mass change rate when heated in an electric furnace at 150°C for 1 hour.

[0046] (Shape of resin composition) The fluororesin composition disclosed herein is not particularly limited in shape, but is particularly preferred to be in powder, pellet, or flake form. Specifically, pellet-shaped resin is easy to handle, transport, and store. Furthermore, it can be easily dissolved in a solvent when used, and its weight can be easily reduced. Specifically for pellet shape, the average major diameter of the pellets is preferably 50 mm or less, and more preferably 20 mm or less. On the other hand, the average major diameter of the pellets is, for example, 1 mm or more. The average aspect ratio of the pellets is preferably 2 or less. The average aspect ratio of the pellets is, for example, 1.0 or more. Furthermore, it is preferable that powder with an average major diameter of 1 mm or less accounts for 10% or less of the total. Flake-shaped resin is preferred in that it has excellent resistance to blocking during storage. Furthermore, it is easy to grind during production.

[0047] The fluorine-containing resin composition described above is preferably soluble in parachlorobenzotrifluoride. Parachlorobenzotrifluoride has been increasingly used as a solvent in recent years, and therefore, it is preferable that the composition has excellent solubility in such a solvent. Here, "dissolves" means that when 50 g of the fluorine-containing copolymer is added to 50 g of parachlorobenzotrifluoride at 25°C, it can be dissolved without any residue.

[0048] The above fluororesin composition is preferably such that, when dissolved in parachlorobenzotrifluoride to a solid content concentration of 50% by mass, the rotational viscosity at 25°C, as measured with a B-type viscometer, is 10,000 mPa·s or less. This is preferable because it allows for suitable use as a paint raw material and further reduces viscosity, thus enabling high solid differentiation in the paint. The rotational viscosity is more preferably 8,000 mPa·s or less, and even more preferably 7,000 mPa·s or less. The lower limit of the rotational viscosity is not particularly limited, but is, for example, 20 mPa·s or more.

[0049] (Manufacturing method) The method for producing the resin composition of this disclosure is not particularly limited, but for example, Step (1): A fluorine-containing polymer (A) is dissolved in an organic solvent (C) to obtain a fluorine-containing resin solution. This solution is then desolvented by reducing the pressure under a heat transfer medium temperature of 150°C or lower, and recovered as a composition. Step (2) involves melting the resin obtained in step (1); It can be obtained by a manufacturing method that includes a step (3) of water-cooling and dewatering the molten resin obtained in step (2). The following describes this manufacturing method step by step.

[0050] (Process 1) Step 1 is a step in which a fluorine-containing resin solution obtained by dissolving a fluorine-containing copolymer (A) in an organic solvent (C) is desolvented by reducing the pressure under a heat transfer medium temperature of 150°C or lower, and recovered as a composition containing 2% by mass or less of the organic solvent. The fluorine-containing resin solution used in this step may be a resin solution obtained by solution polymerization in the organic solvent (C), or a fluorine-containing resin obtained by other methods dissolved in an organic solvent, or a resin solution obtained by solution polymerization may be subjected to a predetermined treatment.

[0051] Step 1 is a step of desolventing such a fluororesin solution by reducing the pressure under a heat medium temperature of 150°C or lower. This step yields a composition containing 2% by mass or less of an organic solvent. The lower limit of the organic solvent content may be, for example, 0% by mass. "Under a heat medium temperature of 150°C or lower" means that the heat medium used as a heating means in the heating device is 150°C or lower. By desolventing by heating at such a relatively low temperature, thermal decomposition of the resin can be prevented. Since the fluororesin solution of this disclosure has functional groups, it is prone to reactions and high molecular weight formation upon heating. To improve this problem, it is preferable to keep the temperature below 150°C. As for the lower limit of the internal temperature of the resin in Step 1, it is preferable to keep it above 80°C, and more preferably above 90°C, in order to ensure sufficient desolventing and flow rate / velocity. The upper limit is more preferably below 145°C, and even more preferably below 140°C.

[0052] The degree of vacuum in step 1 described above is not particularly limited, but for example, it can be carried out under conditions of a vacuum of 10 Torr or less.

[0053] The apparatus for removing the solvent described above is not particularly limited, but for example, a thin-film forming apparatus consisting of a stirring blade for forming a thin film, a heating means using a heat transfer medium for evaporating the solvent, and a discharge screw for discharging the solvent-soluble fluororesin can be used, and an apparatus can be used to pass a solvent-soluble fluororesin solution through it and remove the solvent within the apparatus. Known apparatuses can be used for this purpose.

[0054] (Process 2) Step 2 is a step in which the fluorine-containing copolymer, from which the solvent has been removed in Step 1, is heated and melted. The method of heating and melting is not particularly limited, but it can be done by kneading machine or the like. The melting temperature is not particularly limited, but it is preferably carried out within the range of glass transition temperature (Tg) + 20°C to Tg + 150°C. To increase the fluidity of the resin, ensure the flow rate and velocity, and reduce the thermal history, it is more preferable to have a temperature of Tg + 30°C or higher, and even more preferable to have a temperature of Tg + 40°C or higher. The upper limit temperature is preferably such that the internal temperature of the resin is 145°C or lower, and more preferably 140°C or lower from the viewpoint of thermal stability.

[0055] (Step 3) Step 3 described above is a process of water-cooling and dewatering the molten resin obtained in step (2). In the case of pelletization, the molten resin obtained by the above method is extruded in strand form, water-cooled, and then cut to form pellets. In the case of flakeization, the obtained molten resin is cooled into a flat plate form, and then the resin is crushed by impact to form flakes.

[0056] The fluorine-containing copolymer of this disclosure tends to have a relatively low Tg, so cooling is necessary before cutting with a cutter. Such cooling is performed by water cooling, but water cooling causes the fluorine-containing copolymer to contain water. As mentioned above, the fluorine-containing copolymer of this disclosure has a water content within a predetermined range, so when cooling with water is performed in this way, it is preferable to perform the following dehydration. The method for step 3 is not particularly limited, but for example, pelletization can be performed by an underwater cutter. When using an underwater cutter, the temperature of the circulating water is preferably 0 to 30°C, more preferably 0 to 20°C, and the rotation speed of the cutter is preferably 500 to 5000 rpm, more preferably 1500 to 3500 rpm. If the rotation speed is fast relative to the resin extrusion speed, pellets with small particle size and a small aspect ratio tend to be produced, and if the rotation speed is slow relative to the resin extrusion speed, pellets with large particle size and a large aspect ratio can be obtained.

[0057] If the internal temperature of the resin in step 2 is inappropriate, specifically if the internal temperature is too low and the fluidity is too low, or if the internal temperature is too high and the fluidity is too high, continuous extrusion in strand form or continuous cutting with an underwater cutter becomes difficult, so it is necessary to adjust the resin to an appropriate melt viscosity range. Also, if cooling with cooling water is insufficient, the cutting of the resin and the blocking resistance of the resin after cutting will decrease, so it is preferable that the upper limit temperature be below the Tg and melting point.

[0058] In step 3, it is preferable to perform a dewatering step after the cooling step. This is a step to remove water contained in the fluorine-containing copolymer obtained in the cooling step. The dewatering method is not particularly limited and can be performed by centrifugal dewatering, for example. Specifically, a centrifugal dewatering machine manufactured by GALA Corporation can be used. When performing centrifugal dewatering using a centrifugal dewatering machine, the rotation speed is preferably 500 to 10,000 rpm, and more preferably 1,500 to 5,000 rpm. If a sufficient rotation speed cannot be obtained during centrifugal dewatering, the fluorine-containing copolymer will have a high water content after processing, so it is preferable to perform dewatering at a sufficient rotation speed, specifically 500 rpm or more, and more preferably 1,500 rpm or more. If the rotation speed is too high, the obtained resin will be pulverized and its handling properties will decrease, so it is preferable to perform dewatering at less than 10,000 rpm, and more preferably 5,000 rpm or less.

[0059] The method for producing the fluororesin composition of the present disclosure described above is particularly preferably a method that includes a step of removing water from a fluororesin solution, obtained by dissolving a fluororesin solution in which a fluororesin copolymer has been dissolved in an organic solvent, under a heat transfer temperature of 150°C or lower until the organic solvent is reduced to 2% by mass or less, and then removing water so that the water content is 100 to 3000 ppm.

[0060] (Paint composition) The fluororesin composition described above can be suitably used as a resin for paints. Suitable uses include mixing it with a solvent and other co-components to form a resin solution, or using it in combination with a curing agent to form a curable paint.

[0061] When using parachlorobenzotrifluoride (a1) as the solvent, you may also use parachlorobenzotrifluoride (a1), or a mixed solvent of parachlorobenzotrifluoride (a1) and a solvent (a2) with a boiling point of 100°C or less, where the ratio (mass ratio) of (a1) / (a2) in the solvent is (50~100) / (50~0) (excluding 50 / 50).

[0062] In other words, the essential solvent component is parachlorobenzotrifluoride (a1), which has been widely used as a solvent in recent years, and if necessary, a solvent (a2) with a boiling point of 100°C or less may be added to it in a certain proportion. Such a solvent (A) is a solvent composition that has been increasingly used in recent years as parachlorobenzotrifluoride (a1) has become more common, and the composition of this disclosure can accommodate such a solvent composition.

[0063] (Solvents with a boiling point of 100°C or less (a2)) In this disclosure, the solvent may contain only parachlorobenzotrifluoride (a1), or it may be a mixed solvent containing a predetermined proportion of a solvent (a2) having a boiling point of 100°C or less.

[0064] Such solvents are not particularly limited and can be general ones used in the field of paints. Specifically, examples include t-butylacetic acid, dimethyl carbonate, methyl acetate, ethyl acetate, isopropyl acetate, acetone, methyl ethyl ketone, tetrahydrofuran, n-pentane, n-hexane, and n-heptane. Two or more of these may be used in combination.

[0065] When using solvent (a2) with a boiling point of 100°C or lower, the amount used is preferably such that the ratio (mass ratio) of (a1) / (a2) in the solvent is (50~100) / (50~0) (excluding 50 / 50). If (a2) is added in a ratio exceeding 50 / 50, the paintability will decrease, and a good paint film cannot be formed. It is also acceptable to not add any solvent (a2) with a boiling point of 100°C or lower.

[0066] The above paint composition may contain solvents other than the above solvents (a1) and (a2). Examples include esters such as n-butyl acetate, isobutyl acetate, cellosolve acetate, methoxypropyl acetate, propylene glycol methyl ether acetate, and ethyl 3-ethoxypropionate; ketones such as methyl isobutyl ketone and cyclohexanone; cyclic ethers such as dioxane; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; aromatic hydrocarbons such as xylene, toluene, solvent naphtha, and coal tar naphtha; glycol ethers such as propylene glycol methyl ether and ethyl cellosolve; diethylene glycol esters such as carbitol acetate; aliphatic hydrocarbons such as n-octane, n-nonane, n-decane, n-undecane, n-dodecane, and mineral spirits; and mixed solvents thereof. However, the content of other solvents is preferably 10% by mass or less of the total amount of solvent. The solvent contained in the composition greatly affects the coating performance. Therefore, even if other solvents are used, it is preferable that they are used within a range that does not impair the performance of the composition of this disclosure.

[0067] (Other ingredients) The compositions of this disclosure may contain other components as needed. Other components that may be incorporated into the compositions of this disclosure are not limited to, but include, for example, curing agents, curing catalysts, pigments, curing accelerators, curing retarders, pigment dispersants, defoamers, leveling agents, UV absorbers, light stabilizers, thickeners, adhesion improvers, matting agents, and the like.

[0068] (Hardening agent) As described above, the compositions of this disclosure may consist of hydroxyl group-containing polymers as constituent units. In this case, the hydroxyl groups may be used to induce a curing reaction.

[0069] The curing agents that can be used in the compositions of this disclosure are not particularly limited, and compounds that crosslink by reacting with the curable functional groups (e.g., hydroxyl groups or carboxyl groups) of the fluorine-containing polymer can be used. Examples include isocyanates, amino resins, acid anhydrides, polyepoxy compounds, isocyanate group-containing silane compounds, carbodiimides, oxazolines, aziridines, and the like.

[0070] (curing catalyst) When using the above-mentioned curing agent, a curing catalyst may be used depending on the type of curing agent used.

[0071] (Pigment) The pigments that can be used in the compositions of this disclosure are not particularly limited and may include coloring pigments (for example, inorganic pigments such as titanium dioxide, red iron oxide, yellow iron oxide, and carbon black, and organic pigments such as phthalocyanine blue, phthalocyanine green, quinacridone-based red pigments, and isoindolinone-based yellow pigments); extender pigments such as talc, silica, and calcium carbonate; metal powders such as aluminum powder and stainless steel powder; and, if desired, one or more additives such as mica powder, leveling agents, UV absorbers, heat degradation inhibitors, and foam inhibitors. It may also be used as a clear coating that does not contain pigments.

[0072] (Manufacturing method) The compositions of this disclosure do not particularly limit the method of their manufacturing and can be obtained by general methods of mixing the components constituting the composition. As described above, the compositions can be prepared by mixing the components at the painting site.

[0073] Furthermore, if a hardener is used, it may be a two-component paint composition that is mixed during painting.

[0074] (Coating composition) The compositions disclosed herein can be used as paint compositions. When used as paint compositions, the application method is not particularly limited and includes, for example, air spray painting, airless spray painting, rotary atomization painting, curtain coating, dip painting, roller painting, brush painting, and painting with a doctor blade.

[0075] The coating compositions of this disclosure may be used in combination with other coating compositions to form a multi-layer coating film.

[0076] (Application) The paint composition disclosed herein is not particularly limited in its use, and can be suitably used, for example, as a heavy-duty anticorrosive paint in the construction industry for bridges, steel towers, high-rise buildings, etc. The substrate is also not particularly limited and can be used for coating metals (iron, copper, aluminum, etc.), concrete, wood, plastics, etc. Furthermore, it can also be used in the fields of inks and electronic materials.

[0077] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims. [Examples]

[0078] The present disclosure will now be described in detail based on the following examples. In the following examples, unless otherwise specified, "parts" and "%" represent "parts by mass" and "% by mass," respectively.

[0079] (Production Example 1: Preparation of fluorine-containing copolymer solution A) 2500g of butyl acetate, 1032g of vinyl neononanoate (Veova9), 264g of 4-hydroxybutyl vinyl ether (HBVE), and 13.8g of crotonic acid (CTA) were added to a 6000ml stainless steel autoclave. Under reduced pressure and nitrogen purging, 684g of tetrafluoroethylene (TFE) was added. The mixture was heated to 60.0°C with stirring, and 30g of a peroxide-based polymerization initiator was added to start polymerization. The reaction was stopped when the reactor pressure decreased from 1.0 MPaG to 0.4 MPaG, yielding a solution containing polymers with TFE / HBVE / vinyl neononanoate / CTA ratios of 45.5 / 15.3 / 37.9 / 1.3 mol%. The resulting solution was concentrated using an evaporator to remove a predetermined amount of butyl acetate, preparing a fluorine-containing copolymer solution A with a solid content of 65%.

[0080] (Production Example 2: Preparation of Fluorine-Containing Copolymer Solution B) A solution containing polymers in the same proportions as in Production Example 1 was obtained: chlorotrifluoroethylene (CTFE) / cyclohexyl vinyl ether (CHVE) / ethyl vinyl ether (EVE) / 4-hydroxybutyl vinyl ether (HBVE) = 48.4 / 9.5 / 32.9 / 9.2 mol%. The obtained solution was concentrated using an evaporator to prepare fluorine-containing copolymer solution B with a solid content of 50%.

[0081] The properties of the resin composition and the properties of the solutions obtained from the fluorine-containing copolymer solutions A and B were analyzed according to the methods described below. The results are shown in Table 1.

[0082] (Analysis of monomer unit content constituting the copolymer) Elemental analysis was performed on the fluororesin composition, and the measured fluorine content (mass%) was determined. 1 H-NMR, 19 The content (mol%) of each monomer unit was calculated from compositional analysis using F-NMR spectroscopy.

[0083] (Weight molecular weight Mw measurement method) Measuring device: GPC (Model: HLC-8420) manufactured by Tosoh Corporation Measurement conditions: Three TSKgel SuperMultiporeHZ-M columns were used. Tetrahydrofuran was used as the eluent, and polystyrene with a known molecular weight was used as the standard molecular weight sample.

[0084] (Hydroxyl value) The hydroxyl value (unit: mgKOH / g) was calculated using formula (1) based on the above content analysis results of the fluororesin composition. Hydroxyl value = [OH (mass%)] × [KOH molecular weight] ÷ [OH (equivalent)] × 1000 ÷ 100 ... (1) In formula (1), the "KOH molecular weight" is 56.1. In formula (1), "OH (mass%)" represents the weight ratio of all hydroxyl group-containing monomers to all monomers, calculated from the content (mol%) of each monomer unit calculated in the above content analysis. In formula (1), "OH (equivalent)" represents the value calculated from formula (2). [OH (equivalent)] = [Molecular weight of hydroxyl group-containing monomer] ÷ [Number of hydroxyl groups in one molecule of hydroxyl group-containing monomer] ... (2)

[0085] (Acid value) The obtained fluorine-containing copolymer solution was measured by potentiometric titration in accordance with JIS K 5601, and the acid value (mgKOH / g) per gram of fluorine-containing copolymer was calculated using the value of the heating residue (mass%).

[0086] (Heating residue of fluorine-containing copolymer solution) 2 g of fluorine-containing copolymer solution was weighed into an aluminum cup, and the heating residue (mass %) of the fluorine-containing copolymer solution was calculated from the ratio of the initial weight (W0 = 2 g) to the residual weight W1 after heating in an electric furnace at 150°C for 2 hours (heated residue = 100 × residual weight W1 / initial weight W0).

[0087] [Table 1]

[0088] (Example 1) A fluorine-containing copolymer solution A with a solid content of 65% was preheated to 50°C and fed from above into a vertical thin-film dryer with an inlet temperature of 120°C and a vacuum of 10 Torr at a flow rate of 45 L / hr. The desolvation process was carried out in the thin-film dryer with temperatures of 120°C at the inlet, 90°C at the top, and 90°C at the bottom, and n-butyl acetate was recovered. The fluorine-containing copolymer composition after the desolvation process was extruded directly from the die plate through an extruder into cooling water at 10-20°C, and cutting was performed underwater using a pelletizer (underwater cutter) to carry out desolvation and solidification (cooling and pelletization). At this time, the die temperature was set to 150°C, and the temperature of the molten resin composition near the die plate was 130°C. The rotation speed of the pelletizer in the underwater cutter was kept constant at 2500 rpm. After the solidification process in water, the cooling water containing the solid composition was passed through a centrifugal dehydrator (1800 rpm) to dehydrate it, yielding a homogeneous solid fluorine-containing copolymer composition A1 containing trace amounts of organic solvent and water. The obtained fluorine-containing copolymer composition A1 was filled into polyethylene bags and stored at 25°C. The yield of the composition per hour was 28-32 kg / hr. The appearance and various physical properties of the obtained fluorine-containing copolymer composition A1 were evaluated. The results are shown in the table below.

[0089] (Examples 2-9) In the same manner as in Example 1, fluorine-containing copolymer solution A was subjected to solvent removal, solidification (cooling and pelletization), and dehydration treatment under the conditions described in Tables 2 and 3 to obtain homogeneous solid fluorine-containing copolymer compositions A2 to A9 containing trace amounts of organic solvent and water. The obtained fluorine-containing copolymer compositions A2 to A9 were evaluated for appearance and various physical properties. The evaluation results are shown in the table below.

[0090] (Example 10) In the same manner as in Example 1, fluorine-containing copolymer solution B was subjected to solvent removal, solidification (cooling and pelletization), and dehydration treatment under the conditions described in Table 3 to obtain a homogeneous solid fluorine-containing copolymer composition B1 containing trace amounts of organic solvent and water. The obtained fluorine-containing copolymer composition B1 was evaluated for its appearance and various physical properties. The evaluation results are shown in the table below.

[0091] (Example 11) Fluorine-containing copolymer solution A was dried at 150°C for 4 hours using a vacuum dryer and then allowed to cool in a desiccator to obtain fluorine-containing copolymer composition A14. Fluorine-containing copolymer composition A14 was in the form of a mass containing trace amounts of organic solvent and water.

[0092] (Comparative Example 1) In the same manner as in Example 1, under the conditions described in Table 3, fluorine-containing copolymer solution A underwent a desolvent process under reduced pressure using a thin film dryer and pelletized using an underwater cutter in cooling water. Afterward, 100 g of the aqueous solid composition was recovered without passing it through a centrifugal dehydrator. The recovered aqueous composition was spread on a 1000 μm mesh to drain the water, then spread in a 300 mm x 300 mm PP container so that the pellets did not overlap, and dried statically in an air-circulating electric furnace at 25°C. After 96 hours, it was removed from the electric furnace, yielding 70 g of fluorine-containing copolymer composition A10. After removal, it was filled into a polyethylene bag and stored at 25°C. The obtained fluorine-containing copolymer composition A10 was evaluated for its appearance and various physical properties. The results are shown in the table below.

[0093] (Comparative Example 2) In the same manner as in Example 1, fluorine-containing copolymer solution A was subjected to a desolvent process under reduced pressure using a thin film dryer and pelletized using an underwater cutter in cooling water. Then, in the same manner as in Comparative Example 1, the recovered aqueous composition was dried in an air-circulating electric furnace at 25°C without passing it through a centrifugal dewatering machine. After 48 hours, it was removed from the electric furnace to obtain 70 g of fluorine-containing copolymer composition A11. After removal, it was filled into a polyethylene bag and stored at 25°C. The obtained fluorine-containing copolymer composition A11 was evaluated for appearance and various physical properties. The results are shown in the table below.

[0094] (Comparative Example 3) In the same manner as in Example 1, fluorine-containing copolymer solution A was subjected to a desolvent process under reduced pressure using a thin film dryer and pelletized using an underwater cutter in cooling water. Then, in the same manner as in Comparative Examples 1 and 2, the recovered aqueous composition was dried in an air-circulating electric furnace at 25°C without passing it through a centrifugal dehydrator. After 12 hours, it was removed from the electric furnace to obtain 70 g of fluorine-containing copolymer composition A12. After removal, it was filled into a polyethylene bag and stored at 25°C. The obtained fluorine-containing copolymer composition A12 was evaluated for appearance and various physical properties. The results are shown in the table below.

[0095] (Evaluation method) (Solid appearance) The obtained solid fluororesin compositions were visually classified as pelletized or lumpy, and as uniform or heterogeneous in shape. Visual inspection was performed at 25°C.

[0096] (Pellet shape) When the obtained solid fluororesin composition was in pellet form, the shape of 20 randomly sampled pellets was measured, and their major axis and aspect ratio were determined. The average values ​​were defined as the major axis and aspect ratio.

[0097] (Heating residue of fluororesin-containing composition) Two grams of the fluororesin composition were weighed into an aluminum cup. The heating residue (unit: mass%) of the fluororesin composition was calculated from the ratio of the initial weight (W0 = 2 g) to the residual weight W1 after heating in an electric furnace at 150°C for 2 hours (heating residue = 100 × residual weight W1 / initial weight W0). The measured heating residue corresponds to the content of the fluoropolymer (A).

[0098] (Reduction amount during heating) The amount of weight loss during heating (in mass %) was calculated using the formula "Weight loss during heating = 100 - Residual weight after heating".

[0099] (moisture content) The water content (in ppm) was measured using the Karl Fischer method. The measured water content (water content in the table) corresponds to the percentage of water (B).

[0100] (Amount of residual solvent) The amount of residual solvent (unit: mass%) was calculated using the formula "Residual solvent amount = 100 - Residue after heating - (Moisture content / 10000) = Loss during heating - (Moisture content / 10000)". The amount of residual solvent corresponds to the content of organic solvent (C).

[0101] (Weight-average molecular weight Mw and Mw increase rate) Using the weight molecular weight (Mw) measurement method described above, the weight-average molecular weight (Mw) of the fluorine-containing copolymer before desolvent-solidification (cooling and pelletization) and dehydration treatment (Mw before treatment) and the weight-average molecular weight (Mw after treatment) of the fluorine-containing copolymer after treatment were measured. The Mw increase rate (in %) was calculated using the formula "Mw increase rate = 100 × (Mw after treatment) / (Mw before treatment)".

[0102] [Table 2]

[0103] [Table 3]

[0104] [Table 4]

[0105] [Table 5]

[0106] The pellets obtained using the above method were evaluated based on the following method.

[0107] (Transparency and solubility of the solution) 50 g of solid resin (each of the fluorine-containing copolymer compositions prepared in Examples 1-11 and Comparative Examples 1-3) and 50 g of solvent (parachlorobenzotrifluoride (PCBTF) or tert-butyl acetate) were weighed into a poly bottle. The container was rotated for 24 hours at 25°C using a benchtop mixer to dissolve the resin and obtain a resin solution with a solid content of 50% by mass. The obtained solution was stirred at 1200 rpm for 10 minutes using a stirrer, transferred to a glass tube container, and allowed to stand at room temperature for 24 hours. After that, the liquid was visually inspected for turbidity and transparency. The solution was filtered to check for insoluble matter and gels and to confirm solubility.

[0108] (rotational viscosity) The rotational viscosity of the resin solution obtained above was measured at a solution temperature of 25°C using a Type B rotational viscometer.

[0109] (Solution turbidity) The turbidity of the resin solution obtained above was measured using a turbidimeter (integrating sphere turbidimeter PT-200: Nitto Seiko Analytic Co., Ltd.). Cell used: T-type cell T-10 (10mm cell). The solution was filled to about 80% capacity in the cell, set in the apparatus, and the turbidity (in ppm) was measured after 1 minute.

[0110] (Example of coating film manufacturing) A clear coating was prepared using the resin solution described above. The coating was applied to a glass plate at a thickness of 8 mill using an applicator at 25°C and dried at 25°C for 24 hours. The resulting coating was visually evaluated for defects such as blemishes, repellency, and shrinkage, as well as for the transparency of the coating.

[0111] (Film forming property) No abnormalities: ○ (Good) Slight occurrence of blemishes, pops, shrinkage, etc.: △ (Normal) Significant occurrence of defects such as blemishes, cracks, and shrinkage: × (Defective)

[0112] (Appearance: Transparency of the coating) Transparency:〇(Good) Slight cloudiness: △ (normal) Significant clouding: × (Poor)

[0113] [Table 6]

[0114] [Table 7]

[0115] From the results in Tables 2-7 above, it is clear that the compositions of this disclosure have remarkably superior effects. [Industrial applicability]

[0116] The compositions of this disclosure can be suitably used as paint compositions.

Claims

1. A fluorine-containing copolymer (A) containing monomers having functional groups as constituent units, 95% by mass or more, Water (B) 100-3000ppm It contains as a constituent component, The fluorine-containing copolymer (A) is Of the total polymerization units constituting the polymer, 10 to 60 mol% are fluoroolefin units, At least one monomer unit selected from the group consisting of vinyl esters, vinyl ethers, (meth)acrylic esters, and allyl ethers. It is a fluorine-containing copolymer that further contains A fluororesin composition characterized by being in flake or pellet form at a temperature of 25°C.

2. The fluororesin composition according to claim 1, further containing 0.1 to 2% by mass of an organic solvent (C).

3. The fluorine-containing polymer (A) contains monomers having hydroxyl groups as constituent units, and the hydroxyl value of the fluorine-containing polymer is 45 mg KOH / g or more, according to claim 1 or 2.

4. The fluorine-containing polymer (A) contains monomers having an acid value as constituent units, and the acid value of the fluorine-containing polymer (A) is 1.0 mg KOH / g or more, according to claim 1 or 2.

5. The fluorine-containing polymer (A) is a fluorine-containing resin composition according to claim 1 or 2, wherein the weight-average molecular weight (Mw) on a polystyrene basis, as measured by GPC, is 50,000 or less.

6. The fluorine-containing polymer (A) is soluble in parachlorobenzotrifluoride, and the rotational viscosity at 25°C measured with a B-type viscometer when dissolved in parachlorobenzotrifluoride to a solid content concentration of 50% by mass is 10,000 mPa·s or less, according to claim 1 or 2 of the fluorine-containing resin composition.

7. The fluororesin composition according to claim 1 or 2, wherein the organic solvent (C) comprises at least one selected from the group consisting of n-butyl acetate, ethyl acetate, xylene, toluene, methyl ethyl ketone, methyl isobutyl ketone, acetone, and alcohols having 4 or fewer carbon atoms.

8. A fluororesin composition according to claim 1 or 2, which is a paint composition.

9. The fluororesin composition according to claim 1 or 2, wherein the pellet shape is pellet-shaped, and the average major diameter of the pellet is 20 mm or less, and the average aspect ratio is 2 or less.

10. The fluorine-containing copolymer (A) is contained in a content of 99.0 to 99.9% by mass. The aforementioned water (B) is contained in a concentration of 100 to 3000 ppm. It contains an organic solvent (C) at a content of 0.1 to 1.0% by mass. The fluorine-containing copolymer (A) is Of the total polymerization units constituting the polymer, 10 to 60 mol% are fluoroolefin units, At least one monomer unit selected from the group consisting of vinyl monomers having hydroxyl groups and vinyl monomers having carboxyl groups, A fluororesin composition according to claim 1 or 2, comprising at least one monomer unit selected from the group consisting of alkyl vinyl esters and alkyl vinyl ethers.

11. A method for producing a fluororesin composition according to claim 1 or 2, characterized by comprising the step of desolventing a fluororesin solution obtained by dissolving the fluororesin in an organic solvent (C) at a heat transfer medium temperature of 150°C or lower until the organic solvent (C) is reduced to 2% by mass or less, and then removing water so that the water content is 100 to 3000 ppm.

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