JP7559864B2 - Fluororesin particles and method for producing same - Google Patents

Description

The present invention relates to fluororesin particles with excellent fluidity and filling properties and a method for producing the same.

Fluorine-based resins have excellent electrical properties, chemical resistance, waterproofing, and liquid and oil repellency, so they are used in protective films for semiconductors and other electronic components, water-repellent films for inkjet printer heads, and waterproof and oil-resistant coatings for filters.

In particular, fluororesins containing oxolane rings have a bulky ring structure, making them amorphous and highly transparent and heat resistant. In addition, because they are composed only of carbon, fluorine, and oxygen, they have excellent electrical properties, chemical resistance, waterproofness, and liquid and oil repellency. Furthermore, because they are amorphous, they can be melt molded.

Patent Document 1 describes a polymer of perfluoro(2-methylene-4-methyl-1,3-dioxolane (PFMMD) as a fluororesin containing an oxolane ring and a method for producing the same. Example 2 of Patent Document 1 describes an example in which a polymer of perfluoro(2-methylene-4-methyl-1,3-dioxolane) was polymerized in the presence of nitrogen fluoride (N ₂ F ₂ ) in a sealed glass tube. In this example, no solvent was used, and no description was given of the specific form of the obtained polymer. Non-Patent Document 1 describes the bulk polymerization or solution polymerization of PFMMD as a fluororesin containing an oxolane ring to obtain the polymer. In this specification, unless otherwise specified, resin and polymer are described as having the same meaning.

U.S. Pat. No. 3,308,107

Macromolecules 2005, 38, 4237

Non-Patent Document 1 describes that in the case of bulk polymerization, if purification is not performed after polymerization, the optical properties and heat resistance of the resin will decrease, but that these decreases can be reduced by purification. In solution polymerization, polymerization is performed using one of two types of fluorine-based solvents, and then chloroform is added to cause precipitation. There is no description of the specific form of the resin after purification from bulk polymerization, or the resin obtained by precipitation by adding chloroform.

As a result of the study by the present inventors, the resin obtained by the method described in Patent Document 1 and Non-Patent Document 1 had an amorphous, non-particulate form. Therefore, there was a problem with the flowability of the resin. For example, it was found that when melt molding the resin, problems with handling arise, such as difficulty in continuously supplying the resin into the inside of a molding machine. Furthermore, since the resin described in Patent Document 1 and Non-Patent Document 1 has the above form, it was also found that, for example, when filling the resin into a molding machine, it is not possible to fill a desired weight of resin for a given volume, i.e., the filling ability is low. This point also poses the problem that a container with a large volume relative to the weight of the resin is required, which reduces the economic efficiency of transporting the item.

Therefore, in order to solve the above problems, the present invention aims to provide resin particles containing residue units represented by general formula (1) that have excellent fluidity and filling properties, and a method for producing the same.

Furthermore, as a result of further investigations by the present inventors, the resins produced by the methods described in Patent Document 1 and Non-Patent Document 1 have an amorphous, non-particulate form, making it difficult to remove the solvent that has been incorporated into the resin. If the solvent remains in the resin, the amount of weight loss during heating is large, and there are problems such as foaming occurring during molding processing and a worsening of the working environment during molding processing.

The present invention therefore aims to provide resin particles containing residue units represented by general formula (1), which not only have excellent fluidity and filling properties, but also have a small amount of weight loss upon heating, and a method for producing the same.

In addition, in the manufacture of fluororesins, resin particles can generally be obtained by means of emulsion polymerization, suspension polymerization, or the like. However, in these methods, an emulsifier or dispersant is used as a polymerization aid. However, the emulsifier or dispersant used can remain inside the resin particles and become a foreign matter, and can even cause coloring when the resin is heated, impairing transparency and heat resistance. There is a possibility that such methods will not be able to satisfy the strict cleanliness required for semiconductor peripheral parts in recent years.

Therefore, the present invention also aims to provide a method for producing resin particles having excellent fluidity and filling properties and containing a residue unit represented by general formula (1) without using an emulsifier and/or dispersant, and to provide resin particles having a residue unit represented by general formula (1) that do not contain an emulsifier and/or dispersant.

Furthermore, the present invention aims to provide resin particles containing residue units represented by general formula (1), which not only have excellent fluidity and filling properties, but also have a small amount of thermal weight loss and do not contain an emulsifier and/or a dispersant, and a method for producing the same.

The inventors discovered that novel resin particles containing a residue unit represented by the following general formula (1) and having a volume average particle diameter of 5 μm or more and 2000 μm or less have excellent fluidity and packing properties, leading to the completion of the present invention.

In formula (1), Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ each independently represent one of the group consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. The perfluoroalkyl group may have an etheric oxygen atom. Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ may be bonded to each other to form a ring having 4 to 8 carbon atoms, and the ring may contain an etheric oxygen atom.

Furthermore, the inventors discovered that by using a precipitation polymerization method using a specific organic solvent, resin particles can be obtained without using an emulsifier or dispersant, that the resin particles obtained without using an emulsifier or dispersant do not contain emulsifiers or dispersants and are resin particles that retain the inherent transparency and heat resistance of the resin, and further that resin particles can be obtained that have a small amount of weight loss on heating without any solvent remaining inside the resin particles, thus arriving at a preferred embodiment of the present invention.

The present invention is as follows.
[1]
A resin particle comprising a residue unit represented by the following general formula (1) and having a volume average particle size of 5 μm or more and 2000 μm or less:
(In formula (1), Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ each independently represent one of the group consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. The perfluoroalkyl group may have an etheric oxygen atom. Rf ₁ , Rf ₂ , Rf ₃ , and Rf ₄ may be bonded to each other to form a ring having 4 to 8 carbon atoms, and the ring may contain an etheric oxygen atom.)
[2]
The resin particles according to [1], wherein the volume average particle diameter is 5 μm or more and 500 μm or less.
[3]
The resin particles according to [1] or [2], having an angle of repose of 5° or more and 60° or less.
[4]
The resin particles according to any one of [1] to [3], which are a precipitation polymerization product.
[5]
The resin particles according to any one of [1] to [4], having a bulk density of 0.2 g/mL or more and 1.5 g/mL or less.
[6]
The resin particles according to any one of [1] to [5], which have a weight loss of 1% by weight or less when heated at 250° C.
[7]
The resin particles according to any one of [1] to [6], which do not contain an emulsifier and/or a dispersant.
[8]
The particle according to any one of [1] to [7], wherein the residue unit represented by the general formula (1) is a perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit represented by the general formula (2).
[9]
The method includes a step of subjecting a mixture of a radical polymerization initiator, a monomer represented by the following general formula (3), and an organic solvent under polymerization conditions to obtain a resin containing a residue unit represented by general formula (4),
the organic solvent is a solvent in which at least the monomer is dissolved, but at least a part of the resin produced by polymerization is not dissolved, and the resin precipitates,
The method for producing resin particles according to any one of [1] to [7], wherein the resin produced by the polymerization is precipitated as particles in an organic solvent.
(In formula (3), Rf ₅ , Rf ₆ , Rf ₆ and Rf ₇ each independently represent one of the group consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. The perfluoroalkyl group may have an etheric oxygen atom. Rf ₅ , Rf ₆ , Rf ₆ and Rf ₇ may be bonded to each other to form a ring having 4 to 8 carbon atoms, and the ring may contain an etheric oxygen atom.)
(The definitions of Rf ₅ , Rf ₆ , Rf ₆ , and Rf ₇ in formula (4) are the same as those of Rf ₅ , Rf ₆ , Rf ₆ , and Rf ₇ in formula (3), respectively.)
[10]
The method according to [9], wherein the organic solvent dissolves the monomer represented by general formula (3) but does not dissolve the resin containing the residue unit represented by general formula (4).
[11]
The method according to [10], wherein the organic solvent is an organic solvent in which residual resin particles can be confirmed with the naked eye after resin particles having a weight average molecular weight Mw of 5 x ¹⁰ to 70 x ¹⁰ , which contain a residue unit represented by general formula (4), are immersed in an organic solvent in an amount 10 times (w/w) the amount of the resin particles at 50°C for 5 hours or more.
[12]
The method according to [10] or [11], wherein the organic solvent is an organic solvent in which resin particles having a weight average molecular weight Mw of 5 x ¹⁰ to 70 x ^10, which contains a residue unit represented by general formula (4), are immersed in an organic solvent in an amount 10 times (w/w) the amount of the resin particles at 50°C for 5 hours or more, and then the solution is cooled to 25°C. After that, a resin sample remaining in a solid state is recovered, and the weight loss rate of the resin sample is less than 20% by weight.
[13]
The method according to any one of [9] to [12], characterized in that an organic solvent containing a fluorine atom and a hydrogen atom in the molecule is used.
[14]
14. The method according to claim 13, wherein an organic solvent having a hydrogen atom content of 1% by weight or more in the solvent molecule is used.
[15]
The method according to any one of [9] to [13], wherein the monomer represented by the general formula (3) is perfluoro(4-methyl-2-methylene-1,3-dioxolane) represented by the general formula (5), and the residue unit represented by the general formula (4) is a perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit represented by the general formula (6).

The present invention provides fluororesin particles with excellent fluidity and filling properties, and a method for producing fluororesin particles.

Furthermore, according to the present invention, it is possible to provide resin particles that not only have excellent fluidity and filling properties but also do not contain emulsifiers or dispersants, and a method for producing the same, as well as resin particles that not only have excellent fluidity and filling properties but also have a small amount of weight loss on heating, and a method for producing the same.

FIG. 2 is a graph showing the particle size distribution of the resin particles produced in Example 1. FIG. 3 is a graph showing the particle size distribution of the resin particles produced in Example 4.

The present invention is described in detail below.

The present invention relates to resin particles containing a residue unit represented by general formula (1). The fluororesin particles of the present invention are amorphous and have high transparency and high heat resistance because they have a bulky ring structure contained in general formula (1). In addition, because they are composed only of carbon, fluorine and oxygen, they have high electrical properties, chemical resistance, waterproofness, and liquid and oil repellency.

In the present invention, Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ groups in the residue unit represented by general formula (1) each independently represent one of the group consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. The perfluoroalkyl group may have an etheric oxygen atom. Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ may be linked together to form a ring having 4 to 8 carbon atoms, and the ring may contain an etheric oxygen atom.

Examples of linear perfluoroalkyl groups having 1 to 7 carbon atoms include a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group, an undecafluoropentyl group, a tridecafluorohexyl group, and a pentadecafluoroheptyl group. Examples of branched perfluoroalkyl groups having 3 to 7 carbon atoms include a heptafluoroisopropyl group, a nonafluoroisobutyl group, a nonafluorosec-butyl group, and a nonafluorotert-butyl group. Examples of cyclic perfluoroalkyl groups having 3 to 7 carbon atoms include a heptafluorocyclopropyl group, a nonafluorocyclobutyl group, and a tridecafluorocyclohexyl group. Examples of linear perfluoroalkyl groups having 1 to 7 carbon atoms which may have an etheric oxygen atom include, for example, _{-CF2OCF3 group} , -( _CF2 ) _{2OCF3 group} , and -( _CF2 ) _2OCF2CF3 group. Examples of _{cyclic perfluoroalkyl} groups having 3 to 7 carbon atoms which may have an etheric oxygen atom include, for example, 2-(2,3,3,4,4,5,5,6,6-decafluoro)-pyrinyl group, 4-(2,3,3,4,4,5,5,6,6-decafluoro)-pyrinyl group, and 2-(2,3,3,4,4,5,5-heptafluoro)-furanyl group.

In order to achieve excellent heat resistance, it is preferable that at least one of Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ is a member selected from the group consisting of linear perfluoroalkyl groups having 1 to 7 carbon atoms, branched perfluoroalkyl groups having 3 to 7 carbon atoms, and cyclic perfluoroalkyl groups having 3 to 7 carbon atoms.

Examples of the residue unit represented by general formula (1) include the following residue units:

Among these, resin particles containing the following residue units are preferred because they have excellent heat resistance and moldability, and resins containing perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue units represented by general formula (2) are more preferred.

The resin particles of the present invention have a volume average particle diameter of 5 μm or more and 2000 μm or less, which makes them highly fluid and allows them to be continuously supplied to molding machines and the like. The volume average particle diameter is preferably 5 μm or more and 1000 μm or less. Furthermore, by having the volume average particle diameter in the above range, the amount of solvent remaining in the resin particles can be suppressed, resulting in a small amount of weight loss due to heating. Note that the amount of solvent remaining in the resin particles can also be obtained by obtaining the resin particles by a precipitation polymerization method, which will be described later.

It is more preferable that the resin particles of the present invention have a volume average particle diameter of 5 μm or more and 500 μm or less. With a volume average particle diameter in this range, the resin particles have a higher fluidity, can be easily supplied continuously to a molding machine, and the amount of weight loss due to heating is small. Furthermore, the resin particles have a higher packing ability than the resin obtained by the method described in Non-Patent Document 1, and can be efficiently stored in a container. With a volume average particle diameter of 5 μm or more, the resin particles are less likely to be scattered by air currents, improving the handleability of the resin particles of the present invention. In addition, a volume average particle diameter of 500 μm or less is preferable because the resin particles can be melted in a shorter time, improving the efficiency of molding processing.

The resin particles of the present invention preferably have a 90% particle size of 2500 μm or less, more preferably 2000 μm or less, and even more preferably 1000 μm or less. This reduces the content of coarse particles in the resin particles of the present invention, further improving the flowability and moldability.

The resin particles of the present invention preferably have a 10% particle size of 3 μm or more. This reduces the content of fine particles in the resin particles of the present invention, better preventing dusting, and improving fluidity.

The volume average particle size, 90% particle size, 10% particle size and particle size distribution of the resin particles of the present invention can be evaluated by particle size distribution measurement (volume distribution) using a laser diffraction scattering method. The particle size distribution using the laser diffraction scattering method can be quantified with good reproducibility by dispersing the resin particles in water or an organic solvent such as methanol, and if necessary, treating the particles to make the dispersion state uniform using an ultrasonic homogenizer, and then measuring. An example of a laser scattering meter is the Microtrac manufactured by Microtrac Bell Co., Ltd.

The volume average particle diameter, also known as the Mean Volume Diameter, is the average particle diameter expressed on a volume basis. When the particle size distribution is divided into each particle size channel, the representative particle size value of each particle size channel is d, and the volume-based percentage of each particle size channel is v, it is expressed as Σ(vd)/Σ(v).

The 10% particle size refers to the particle size at which the cumulative amount is 10% when the total volume of the powder group is taken as 100%. The 90% particle size refers to the particle size at which the cumulative amount is 90% when the total volume of the powder group is taken as 100%.

The resin particles of the present invention preferably do not contain an emulsifier and/or a dispersant. By not containing an emulsifier and/or a dispersant, the resin and resin particles have excellent transparency and heat resistance. Resin particles that do not contain an emulsifier and/or a dispersant can be produced using the precipitation polymerization method described below. Therefore, the resin particles of the present invention are preferably precipitation polymers. Here, the dispersant is an agent that has the function of dispersing the resin particles in a solvent, and examples of such agents include polyvinyl alcohol, methyl cellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methyl cellulose. The emulsifier is an agent that has the function of emulsifying the resin particles in a solvent, and examples of such agents include fluorine-containing surfactants such as sodium perfluorooctanoate, sodium perfluorooctane sulfonate, and ammonium perfluorooctanoate; non-fluorine-containing surfactants such as sodium lauryl sulfate and ethylene glycol-based polymers.

From the viewpoint of packing property, the bulk density of the resin particles of the present invention is preferably 0.2 g/cm ³ or more and 1.5 g/cm ³ or less. The bulk density can be measured by the method described in the examples below.

The resin particles of the present invention may contain other monomer residue units, such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP), chlorotrifluoroethylene (CTFE), trifluoroethylene, hexafluoroisobutylene, perfluoroalkylethylene, fluorovinyl ether, vinyl fluoride (VF), vinylidene fluoride (VDF), perfluoro-2,2-dimethyl-1,3-dioxole (PDD), perfluoro(allyl vinyl ether), and perfluoro(butenyl vinyl ether).

The resin particles of the present invention preferably have an angle of repose of 5° or more and 60° or less. This increases the fluidity of the resin particles, making it easier to continuously supply them to molding machines and the like. The angle of repose is more preferably 5° or more and 40° or less, and even more preferably 10° or more and 40° or less.

The angle of repose here refers to the angle between a plane and the ridge of the powder when resin powder is piled on a plane. The angle of repose can be evaluated by filling a container with resin powder, allowing it to fall naturally, and measuring the angle formed by the pile of resin powder when piled on a horizontal surface. A specific method for measuring the angle of repose will be described in the Examples below.

In the present invention, there is no restriction on the molecular weight of the resin particles, and examples of the molecular weight include a weight average molecular weight of 2,500 to 2,000,000 as measured by gel permeation chromatography (GPC). From the viewpoint of the melt viscosity and mechanical strength of the resin, it is preferable that the molecular weight is 10,000 to 1,000,000 (g/mol). During the measurement, polymethylmethacrylate is used as a standard sample, and the weight average molecular weight converted into polymethylmethacrylate is calculated from the elution times of the resin particles and the standard sample.

Next, we will explain the method for producing the resin particles of the present invention.

The resin particles of the present invention can be produced, for example, by a method including a step of subjecting a mixture of a radical polymerization initiator, a monomer represented by the following general formula (3), and an organic solvent under polymerization conditions to obtain a resin containing a residue unit represented by general formula (3).

In formula (3), Rf ₅ , Rf ₆ , Rf ₇ and Rf ₈ have the same meanings as Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ in formula (1), respectively.

In formula (4), Rf ₅ , Rf ₆ , Rf ₇ and Rf ₈ have the same meanings as Rf ₁ , Rf ₂ , Rf ₃ and Rf ₄ in formula (1), respectively.

In the method for producing resin particles of the present invention, the organic solvent dissolves at least the monomer represented by general formula (3), but does not dissolve at least a part of the resin containing the residue unit represented by general formula (4) produced by polymerization, and causes precipitation of the resin, and the resin produced by the polymerization precipitates in the organic solvent as particles. The organic solvent used in the method for producing resin particles of the present invention may be referred to as a "precipitation polymerization solvent". More specifically, the precipitation polymerization solvent can be an organic solvent that dissolves the monomer represented by general formula (3) and does not dissolve the resin containing the residue unit represented by general formula (4), and this precipitation polymerization solvent is hereinafter referred to as precipitation polymerization solvent A. In the present invention, by using the precipitation polymerization solvent, the resin produced by the polymerization reaction can be precipitated as particles having a specific volume average particle size, and as a result, resin particles with excellent moldability and filling properties can be produced. In addition, since no polymerization aids such as emulsifiers and dispersants are used, resin particles that do not contain emulsifiers and dispersants that cause deterioration of transparency and heat resistance can be produced.

Here, the precipitation polymerization solvent A means a solvent in which resin particles containing a residue unit represented by the general formula (4) remain after the resin particles are immersed in the organic solvent for a long time. Specifically, when resin particles having a weight average molecular weight Mw of 5×10 ⁴ to 70×10 ⁴ containing the residue unit represented by the general formula (4) are immersed in an organic solvent of 10 times the amount (w/w) of the resin particles at 50° C. for 5 hours or more, and the remaining resin particles can be confirmed with the naked eye in the organic solvent, the organic solvent can be regarded as the precipitation polymerization solvent A. The precipitation polymerization solvent A is preferably an organic solvent in which the weight loss rate of the resin sample remaining in a solid state is recovered after the solution is cooled to 25° C. after immersion for 5 hours or more at 50° C. is less than 20% by weight. The weight loss rate of the resin sample is more preferably less than 12% by weight, and even more preferably less than 10% by weight.

The resin weight loss rate can be measured by the following method. After filtering the cooled solution, the solids on the filter are rinsed with the solvent, washed multiple times with acetone, and then dried to recover the resin sample on the filter. The weight of the recovered resin is measured, and the resin weight is subtracted from the amount of resin immersed in the organic solvent, and the result is divided by the amount of resin immersed in the organic solvent to obtain the resin weight loss rate.

Precipitation polymerization solvents include non-halogenated organic solvents such as acetone, methyl ethyl ketone, hexane, and butyl acetate, chlorine-based organic solvents such as dichloromethane and chloroform, and organic solvents that contain fluorine atoms in the molecule.

Furthermore, as the precipitation polymerization solvent, an organic solvent containing fluorine atoms and hydrogen atoms in the molecule is preferable because it is difficult for a chain transfer reaction to occur in radical polymerization, has a high polymerization yield, and is easy to obtain a high molecular weight substance. Specific examples of the precipitation polymerization solvent containing fluorine atoms and hydrogen atoms in the molecule include 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoroisopropanol, 1,2,2,3,3,4,4-heptafluorocyclopentane, 1H,1H-pentafluoropropanol, 1H,1H-heptafluorobutanol, 2-perfluorobutylethanol, 4,4,4-trifluorobutanol, 1H,1H,3H-tetrafluoropropanol, 1H,1H,5H-octafluoropropanol, 1H,1H,7H-dodecafluoroheptanol, 1H,1H,3H-hexafluorobutanol, 2, Examples include 2,3,3,3-pentafluoropropyl difluoromethyl ether, 2,2,3,3,3-pentafluoropropyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl ethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, hexafluoroisopropyl methyl ether, 1,1,3,3,3-pentafluoro-2-trifluoromethylpropyl methyl ether, 1,1,2,3,3,3-hexafluoropropyl methyl ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, and 2,2,3,4,4,4-hexafluorobutyl difluoromethyl ether.

Among these, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoroisopropanol, and 1,2,2,3,3,4,4-heptafluorocyclopentane are preferred, with 1,2,2,3,3,4,4-heptafluorocyclopentane being preferred because it has an excellent polymerization yield and is easy to obtain a high molecular weight product. The ratio of fluorine atoms to hydrogen atoms in the molecules of the precipitation polymerization solvent is preferably fluorine atoms:hydrogen atoms=1:9 to 9:1 in terms of the number of atoms, more preferably 1:9 to 7:3, and even more preferably 4:6 to 7:3, in terms of the excellent polymerization yield.

The precipitation polymerization solvent contains fluorine atoms and hydrogen atoms in the molecule, which is excellent in polymerization yield, and the content of hydrogen atoms in the solvent is preferably 1% by weight or more, more preferably 1.5% by weight or more, based on the weight of the solvent molecule. In addition, the content of hydrogen atoms in the solvent is preferably 1% by weight or more and 5% by weight or less, more preferably 1.5% by weight or more and 4% by weight or less, because it is excellent in polymerization yield and easy to obtain high molecular weight substances. In addition, the precipitation polymerization solvent does not contain chlorine atoms in the molecule, which is excellent in polymerization yield and easy to obtain high molecular weight substances.

The ratio of the monomer represented by general formula (3) to the precipitation polymerization solvent is preferably 1:99 to 50:50 by weight, more preferably 5:95 to 40:60, and even more preferably 5:95 to 30:70, since this provides excellent productivity and particles with excellent flow properties.

Examples of radical polymerization initiators for radical polymerization include organic peroxides such as benzoyl peroxide, lauryl peroxide, octanoyl peroxide, acetyl peroxide, di-tetr-butyl peroxide, tetr-butylcumyl peroxide, dicumyl peroxide, tetr-butyl peroxyacetate, perfluoro(di-tetr-butyl peroxide), bis(2,3,4,5,6-pentafluorobenzoyl) peroxide, tetr-butyl peroxybenzoate, and tetr-butyl perpivalate; and azo initiators such as 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-butyronitrile), 2,2'-azobisisobutyronitrile, dimethyl-2,2'-azobisisobutyrate, and 1,1'-azobis(cyclohexane-1-carbonitrile).

In the manufacturing method of the present invention, it is preferable that the monomer represented by general formula (3) is perfluoro(4-methyl-2-methylene-1,3-dioxolane) represented by general formula (5), and the residue unit represented by general formula (4) is a perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit represented by general formula (6).

The resin particles of the present invention are resin particles that do not easily expand during molding, so the weight loss when heated to 250°C is preferably 1% by weight or less, and more preferably 0.5% by weight or less. There is no particular limitation on the minimum weight loss when heated to 250°C, but it can be, for example, 0.001% by weight or more. The resin particles of the present invention are resin particles that do not easily expand during molding, so the amount of residual solvent contained in the resin is preferably 1% by weight or less, and more preferably 0.5% by weight or less. Here, the weight loss when heated to 250°C refers to the weight loss at 250°C when the temperature is raised from 40°C at 10°C/min under an air flow using TG-DTA, and is calculated by (1-(sample weight at 250°C)/(weighed sample weight)) x 100).

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

<Volume average particle size>
The volume average particle size (unit: μm) was measured using MT3000 manufactured by Microtrac and methanol as the dispersion medium.

<10% particle size>
The 10% particle size (unit: μm) was measured using MT3000 manufactured by Microtrac and methanol as the dispersion medium.

<90% particle size>
The 90% particle size (unit: μm) was measured using MT3000 manufactured by Microtrac and methanol as the dispersion medium.

<Liquidity>
The resin was rated as good (.largecircle.) when it was particulate, and as poor (.times.) when it was not particulate.

<Bulk density>
The resin particles were dropped and filled up to the 50 mL mark in the graduated cylinder without impacting the graduated cylinder. The weight (g) of the resin particles per 50 mL of this volume was measured. The weight of the resin particles was divided by the volume to calculate the bulk density (g/mL).

<Filling ability>
A bulk density of 0.2 g/mL or more was rated as good (◯), and a bulk density of less than 0.2 g/mL was rated as poor (×).

<Weight average molecular weight Mw>
The measurement was carried out using gel permeation chromatography equipped with a column TSKgel Super HZM-M manufactured by Tosoh Corporation and an RI detector. The standard sample was a standard polymethylmethacrylate (Agilent). The weight average molecular weight Mw in terms of polymethyl methacrylate was calculated from the elution times of the sample and the standard sample.

<250℃ heating weight loss>
Approximately 10 to 15 mg of sample was weighed into an aluminum sample pan (SSC000E030, Hitachi High-Tech Science Corporation), and the sample was analyzed under instrument air flow (160 mL) using a TG/DTA device (TG/DTA6200AST2, Hitachi High-Tech Science Corporation). The sample was heated from 40° C. to 300° C. at a rate of 10° C./min, and the weight loss at 250° C. (1-(sample weight at 250° C.)/(weighed sample weight))×100) was calculated. The weight loss at 100°C was calculated.

<Angle of repose>
A sample bottle was filled with 7 ml of resin powder, and a glass powder funnel (manufactured by AS ONE Corporation; upper aperture 50 mm, lower aperture 10 mm, total funnel length 100 mm, funnel foot height 40 mm) was fixed on a circular stand (made of glass) with a diameter of 4 cm so that the bottom end of the powder funnel was 4 cm above the circular stand. Using the funnel, the resin powder was dropped from the height of the upper end of the funnel, and the angle (°) of the slope of the mountain formed when it was piled up was measured with a protractor (for the comparative example, the resin powder was dropped without using a powder funnel due to poor fluidity of the resin powder).

Example 1: Production of perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles The inside of a 1 L SUS316 autoclave equipped with an anchor-type stirring blade, a nitrogen inlet tube, and a thermometer was replaced with nitrogen. 1.288 g (0.00305 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator, 150.0 g (0.615 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, and 1340 g of Asahiklin AE-3000 (manufactured by Asahi Glass Co., Ltd., 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, content of hydrogen atoms in the solvent molecule: 1.51 wt%, fluorine atoms: hydrogen atoms in the solvent molecule = 7:3 (number ratio)) as a precipitation polymerization solvent were added, and the mixture was kept at 55°C for 24 hours with stirring to carry out precipitation polymerization. After cooling to room temperature, the liquid containing the purified resin particles was filtered, washed with acetone, and vacuum dried to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles (Resin A) (yield: 56%). The shape, volume average particle size, 10% particle size, 90% particle size, bulk density, and angle of repose of the obtained resin particles are shown in Table 1. The obtained resin particles had excellent fluidity and filling properties. The weight average molecular weight Mw of the obtained Resin A was 4.4 x ¹⁰⁵ .

Comparative Example 1: Production of perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin In a 75 mL glass ampoule, 0.017 g (0.0000407 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator, 5.0 g (0.0205 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, and 8.2 g of hexafluorobenzene (content of hydrogen atoms in the solvent molecule: 0% by weight, fluorine atoms: hydrogen atoms in the solvent molecule = 10:0 (number ratio)) were placed as a polymerization solvent, and the mixture was repeatedly substituted with nitrogen and depressurized, and then sealed under reduced pressure. The ampoule was placed in a thermostatic bath at 55°C and held for 24 hours to carry out radical solution polymerization, resulting in a viscous liquid in which the resin was dissolved. After cooling to room temperature, the ampoule was opened, and the resin solution was diluted with 36 g of hexafluorobenzene to adjust the viscosity, to prepare a diluted resin solution. 1 L of chloroform was added to a beaker equipped with an anchor blade, and the diluted resin solution was added to the chloroform under stirring to precipitate the resin, which was then vacuum dried to obtain a perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin (resin D) (yield: 61%). The weight average molecular weight Mw of the obtained resin D was 3.5 x 10 ^5. The shape, bulk density, and angle of repose of the obtained resin are shown in Table 1. Since the resin was amorphous, the volume average particle size could not be measured. In the case of , the obtained resin had problems with fluidity and filling properties.

Example 2: Production of perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles The inside of a 1 L SUS316 autoclave equipped with an anchor-type stirring blade, a nitrogen inlet tube, and a thermometer was replaced with nitrogen. 0.346 g (0.000820 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator, 100.0 g (0.410 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, and 890 g of 2,2,2-trifluoroethanol (content of hydrogen atoms in the solvent molecule: 3.03 wt %, fluorine atoms: hydrogen atoms in the solvent molecule = 5:5 (number ratio)) as a precipitation polymerization solvent were added, and the mixture was maintained at 55°C for 24 hours with stirring. Precipitation polymerization was carried out by cooling to room temperature, filtering the liquid containing the purified resin particles, washing with acetone, and drying in vacuum to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles (resin B) (yield: 78%). The shape, volume average particle size, 10% particle size, 90% particle size, bulk density, and angle of repose of the obtained resin particles are shown in Table 1. The obtained resin particles had excellent fluidity and filling properties. The weight average molecular weight Mw of the obtained resin B was 1.1 x ¹⁰⁵ .

(Example 3) Production of perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles The inside of a 1 L SUS316 autoclave equipped with an anchor-type stirring blade, a nitrogen inlet tube and a thermometer was replaced with nitrogen. 0.519 g (0.00123 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator, 150.0 g (0.615 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, and 1150 g of chloroform as a precipitation polymerization solvent were added, and the mixture was stirred at 55°C for 24 hours to carry out precipitation polymerization. The mixture was cooled to room temperature, and the liquid containing the purified resin particles was filtered, washed with acetone, and vacuum dried to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles (resin C) (yield: 19%). The shape, volume average particle size, 10% particle size, 90% particle size, bulk density, and angle of repose of the obtained resin particles are shown in Table 1. The obtained resin particles had excellent fluidity and filling properties. The weight average molecular weight Mw of the obtained resin C was 7.0 x ¹⁰³ .

Example 4: Production of perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles The inside of a 1 L SUS316 autoclave equipped with an anchor-type stirring blade, a nitrogen inlet tube, and a thermometer was replaced with nitrogen. 1.038 g (0.00246 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator, 300.0 g (1.23 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, and 1200 g of Zeorola-H (manufactured by Zeon Corporation, 1,2,2,3,3,4,4-heptafluorocyclopentane, content of hydrogen atoms in the solvent molecule: 1.55 wt%, fluorine atoms: hydrogen atoms in the solvent molecule = 7:3 (number ratio)) as a precipitation polymerization solvent were added, and the mixture was kept at 55°C for 24 hours under stirring to carry out precipitation polymerization. After cooling to room temperature, the liquid containing the purified resin particles was filtered, washed with acetone, and vacuum dried to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles (Resin E) (yield: 86%). The shape, volume average particle size, 10% particle size, 90% particle size, bulk density, and angle of repose of the obtained resin particles are shown in Table 2. The obtained resin particles had excellent fluidity and filling properties. The weight average molecular weight Mw of the obtained Resin E was 4.9 x ¹⁰⁵ .

Example 5: Production of perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles The inside of a 1 L SUS316 autoclave equipped with an anchor-type stirring blade, a nitrogen inlet tube, and a thermometer was replaced with nitrogen. 0.519 g (0.00123 mol) of bis(2,3,4,5,6-pentafluorobenzoyl) peroxide as an initiator, 150.0 g (0.615 mol) of perfluoro(4-methyl-2-methylene-1,3-dioxolane) as a monomer, and 1,340 g of 1,1,1,3,3,3-hexafluoroisopropanol (content of hydrogen atoms in the solvent molecule: 1.82 wt%, fluorine atoms: hydrogen atoms in the solvent molecule = 6:4 (number ratio)) as a precipitation polymerization solvent were added, and the mixture was kept at 55°C for 24 hours with stirring to carry out precipitation polymerization. After cooling to room temperature, the liquid containing the purified resin particles was filtered, washed with acetone, and vacuum dried to obtain perfluoro(4-methyl-2-methylene-1,3-dioxolane) resin particles (Resin F) (yield: 59%). The shape, volume average particle size, 10% particle size, 90% particle size, bulk density, and angle of repose of the obtained resin particles are shown in Table 2. The obtained resin particles had excellent fluidity and filling properties. The weight average molecular weight Mw of the obtained Resin F was 7.9 x ¹⁰⁵ .

(Reference Example 1)
The resin particles obtained in Example 1 were immersed in 10 times the amount of each of the solvents at 50° C. for 5 hours, and the presence or absence of remaining resin particles was observed with the naked eye.

Residual resin particles were confirmed with the naked eye in the following organic solvents:
1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 2,2,2-trifluoroethanol, 1,1,1,3,3,3-hexafluoroisopropanol, 1,2,2,3,3,4,4-heptafluorocyclopentane, chloroform.

Then, the mixture was cooled to 25°C, filtered, and the resin particles were extracted by rinsing with the solvent. The resin particles were then washed twice with 10 times the amount of acetone and vacuum dried. The recovery rate was calculated from the dry weight, and in both cases the recovery rate was 90% or more. The filtrate obtained above was also distilled off, and the solid content in the filtrate was calculated. The solid content in the filtrate was less than 10% of the resin particles used. From the above results, it was confirmed that the weight loss rate of the resin weight was less than 10% by weight.

(Reference Example 2)
The resin particles obtained in Example 1 were immersed in 10 times the amount of each of the following solvents at 50° C. for 5 hours, and the presence or absence of remaining resin particles was observed with the naked eye.
The organic solvents in which no resin particles remained visible to the naked eye were as follows:
Hexafluorobenzene, CF ₃ CF ₂ CHCl ₂ (content of hydrogen atoms in the solvent molecule: 0.55% by weight, fluorine atoms:hydrogen atoms in the solvent molecule=8:2 (number ratio))

Visual observation at 50°C showed that all solutions were transparent with almost no turbidity. They were then cooled to 25°C, filtered, rinsed with the solvent, and vacuum-dried. The recovery rate was calculated from the weight increase of the filter, and all were less than 5% by weight. From the above results, it was confirmed that the weight loss rate of the resin after immersion in the solvent was 95% by weight or more.

The present invention provides fluororesin particles that have excellent fluidity and filling properties and a small amount of weight loss when heated, and a method for producing the fluororesin particles.

Claims (5)

The method includes a step of subjecting a mixture of a radical polymerization initiator, a monomer represented by the following general formula (3), and an organic solvent under polymerization conditions to obtain a resin containing a residue unit represented by general formula (4),
the organic solvent is a solvent in which at least the monomer is dissolved, but at least a part of the resin produced by polymerization is not dissolved, and the resin precipitates; and after resin particles having a weight average molecular weight Mw of 5×10 ⁴ to 70×10 ⁴ containing a residue unit represented by general formula (4) are immersed in an organic solvent in an amount 10 times (w/w) the amount of the resin particles at 50° C. for 5 hours or more, the remaining resin particles can be confirmed with the naked eye in the organic solvent ;
The resin produced by the polymerization precipitates as particles in an organic solvent, the resin particles containing a residue unit represented by general formula (4) and having a volume average particle size of 5 μm or more and 2000 μm or less (excluding the case where the organic solvent is 1,1,2-trichloro-1,2,2-trifluoroethane).
(In formula (3), Rf ₅ , Rf ₆ , Rf ₇ , and Rf ₈ each independently represent one of the group consisting of a fluorine atom, a linear perfluoroalkyl group having 1 to 7 carbon atoms, a branched perfluoroalkyl group having 3 to 7 carbon atoms, or a cyclic perfluoroalkyl group having 3 to 7 carbon atoms. The perfluoroalkyl group may have an etheric oxygen atom. Rf ₅ , Rf ₆ , Rf ₇ , and Rf ₈ may be bonded to each other to form a ring having 4 to 8 carbon atoms, and the ring may contain an etheric oxygen atom.)
(The definitions of Rf ₅ , Rf ₆ , Rf ₇ , and Rf ₈ in formula (4) are the same as those of Rf ₅ , Rf ₆ , Rf ₇ , and Rf ₈ in formula (3), respectively.) The method of claim 1, except when the resin is a copolymer containing 1 mol % or more of perhalo-2,2-dilower alkyl-1,3-dioxole (each alkyl group independently has 1 to 3 carbon atoms, and the halogen substituents are chlorine or fluorine, with the proviso that each alkyl group has at least one fluorine atom). 3. The method according to claim 1 or 2, wherein the organic solvent is an organic solvent in which resin particles having a weight average molecular weight Mw of 5 x ¹⁰ to 70 x ^10, which contains a residue unit represented by general formula (4), are immersed in an organic solvent in an amount 10 times (w/w) the amount of the resin particles at 50°C for 5 hours or more , the solution is cooled to 25°C, and the resin sample remaining in a solid state is recovered, and the weight loss rate of the resin sample is less than 20% by weight. The method according to any one of claims 1 to 3, wherein the monomer represented by general formula (3) is perfluoro(4-methyl-2-methylene-1,3-dioxolane) represented by general formula (5), and the residue unit represented by general formula (4) is a perfluoro(4-methyl-2-methylene-1,3-dioxolane) residue unit represented by general formula ( 6) .
The method according to claim 1 , wherein the resin particles have a 90% particle size of 1000 μm or less.