JP5402789B2 - Fluoropolymer aqueous dispersion - Google Patents

Description

The present invention relates to aqueous fluoropolymer dispersions.

Aqueous dispersions of fluoropolymers are used for applications such as impregnation and painting. A nonionic surfactant is added to the aqueous dispersion for the purpose of improving mechanical stability and storage stability and adjusting the viscosity.

Conventionally, studies on this nonionic surfactant have been made. For example, Patent Document 1 discloses a surfactant having a T-structure in which a hydrophobic group has a secondary alkyl group or a primary alkyl group having a side chain, and a hydrophilic group chain is bonded to the middle of the hydrophobic group. Is described. Reference 2 describes an isotridecyl ether surfactant having an oxypropylene group, which is made of isotridecyl having at least three branches and used as a foam-suppressing surfactant.

Patent Document 3 proposes a fluororesin aqueous dispersion composition containing an aliphatic polyoxyalkylene ether dispersant having a 50% decomposition temperature of 250 ° C. or higher.

Japanese Patent Laid-Open No. 11-152385 JP 2000-511578 A International Publication No. 03/106556 Pamphlet

Nonionic surfactants give mechanical and storage stability to aqueous dispersions, enable adjustment of the viscosity of aqueous dispersions, and improve the mixing of additives such as pigments and fillers. However, when an aqueous dispersion is applied to form a coating film and then dried or fired, there is a problem of generating odor.

On the other hand, for example, when a nonionic surfactant whose hydrophobic group is a butene trimer is selected, the odor is improved, but the mechanical stability of the aqueous dispersion is lowered.

The object of the present invention is to provide an aqueous fluoropolymer dispersion that is excellent in mechanical stability and storage stability, can suppress an increase in viscosity even at a high temperature, and is less likely to generate odor even during drying and firing, in view of the above situation. There is.

The present invention includes (A) a fluoropolymer, (B) an aqueous medium, and (C) a stabilizer, wherein the stabilizer (C) is a compound represented by the following general formula (1). An aqueous fluoropolymer dispersion.
R ¹ O— (A ¹ O) _m —H (1)
(In the formula, A ¹ O represents an oxyalkylene group having 2 to 4 carbon atoms. M represents an average number of added moles of the oxyalkylene group, and is an integer of 1 to 50. R ¹ has a carbon number. 14 to 20 and represents an alkyl group containing at least one of a tertiary carbon atom or a quaternary carbon atom.)

R ¹ is an alkyl group containing one or both of a tertiary carbon atom and a quaternary carbon atom, and the total of the tertiary carbon atom and the quaternary carbon atom is three or more. Is preferred.

R ¹ is preferably an alkyl group having 16 to 18 carbon atoms.

R ¹ is represented by the following formula (2)

It is preferable that it is an alkyl group represented by these.

The stabilizer (C) preferably has a cloud point of 40 to 85 ° C.

Fluoropolymer (A) is polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, polyvinylidene fluoride, ethylene / tetrafluoroethylene. It is preferably at least one polymer selected from the group consisting of a copolymer and an ethylene / chlorotetrafluoroethylene copolymer.

The solid content concentration of the fluoropolymer (A) is preferably 30 to 75% by mass.

It is preferable that 0.05-5.0 mass parts stabilizer (C) is included with respect to 100 mass parts of fluoropolymer (A).

Furthermore, it is preferable to include (D) a nonionic surfactant (excluding the stabilizer (C)).

The nonionic surfactant (D) is preferably a compound represented by the following general formula (4).
_{^{R 2 O- (A 2 O)}} n -H (4)
(In the formula, A ² O represents an oxyalkylene group having 2 to 18 carbon atoms. N represents an average number of added moles of the oxyalkylene group and is an integer of 1 to 50. R ² represents the number of carbon atoms. Represents a linear alkyl group having 14 to 20 carbon atoms or a linear or branched alkyl group having 8 to 13 carbon atoms.)

It is preferable that 1-20 mass parts nonionic surfactant (D) is included with respect to 100 mass parts of fluoropolymer (A).

The present invention is also a paint comprising the above-mentioned aqueous fluoropolymer dispersion.

The invention also relates to the use of the aqueous fluoropolymer dispersion described above as a coating.

Since the fluoropolymer aqueous dispersion of the present invention has the above-described configuration, it is excellent in mechanical stability and storage stability, can suppress an increase in viscosity even at high temperatures, and can reduce odor even during drying and firing. ing.

The present invention is described in detail below.

The aqueous fluoropolymer dispersion of the present invention comprises (A) a fluoropolymer, (B) an aqueous medium, and (C) a stabilizer. Stabilizer (C) is characterized by a specific molecular structure.

The stabilizer (C) is represented by the following general formula (1)
R ¹ O— (A ¹ O) _m —H (1)
It is a compound represented by these.

In Formula (1), R ¹ represents an alkyl group having 14 to 20 carbon atoms and containing at least one of a tertiary carbon atom and a quaternary carbon atom. It is the inventors of the present invention that the presence of tertiary carbon atoms or quaternary carbon atoms in the molecule and the presence of relatively long hydrophobic groups are greatly related to the improvement of the mechanical stability and storage stability of the aqueous dispersion. It was found by. The excellent characteristics of the aqueous dispersion of the present invention seem to result from the characteristic structure of the alkyl group represented by R ¹ in the molecular structure of the stabilizer (C). In particular, it was very surprising that the stabilizer (C) used in the present invention had improved mechanical stability and storage stability despite having a relatively long hydrophobic group.

If the number of carbon atoms of R ¹ in formula (1) is too large, the viscosity of the stabilizer (C) itself may increase so as to be inferior in handleability or inferior in miscibility when added to an aqueous medium. If the number of carbon atoms in R ¹ is too small, the mechanical stability and storage stability are poor. R ¹ is preferably a non-fluorinated alkyl group. R ¹ preferably has 16 to 18 carbon atoms, and more preferably 18 carbon atoms.

R ¹ in Formula (1) includes one or both of a tertiary carbon atom and a quaternary carbon atom, and the total of the tertiary carbon atom and the quaternary carbon atom is 3 or more. An alkyl group is preferred. The upper limit is not particularly limited, but may be 7 or less.

The R ^1, the following formula (2)

And an alkyl group represented by the following formula (3)

It is preferably at least one alkyl group selected from the group consisting of alkyl groups represented by the formula (2), more preferably an alkyl group represented by the formula (2).

In formula (1), A ¹ O represents an oxyalkylene group having 2 to 4 carbon atoms. A ¹ O in Formula (1) is more preferably an oxyalkylene group having 3 to 25 oxyethylene units and 0 to 5 oxypropylene units. M in Formula (1) represents the average addition mole number of an oxyalkylene group. M in Formula (1) is an integer of 1-50, More preferably, it is an integer of 5-20. A ¹ O is preferably a non-fluorinated oxyalkylene group.

The kind of oxyalkylene group, the number of units, and the average number of added moles are closely related to the cloud point of the stabilizer (C) described later, and in the present invention, these are selected so as to be in the cloud point range described later. Is preferred.

It is preferable that a stabilizer (C) has a cloud point of 40-85 degreeC. The cloud point is a temperature at which the aqueous solution starts to become cloudy when the temperature of the aqueous solution containing the stabilizer (C) is increased. The cloud point can be measured by dissolving the stabilizer (C) in water to a concentration of 1% as usual, or the stabilizer (C) is 25% butyl carbitol. It can be measured by dissolving in an aqueous solution to a concentration of 10%, or it can be measured by dissolving the stabilizer (C) in a 5% potassium sulfate aqueous solution to a concentration of 1%.

The stabilizer (C) is a cloud point measured by dissolving the stabilizer (C) in water to a concentration of 1%, and the stabilizer (C) in a 25% aqueous solution of butyl carbitol to a concentration of 10%. At least one cloud point of the cloud point measured by dissolving so as to be, and the cloud point measured by dissolving the stabilizer (C) in a 5% potassium sulfate aqueous solution so as to have a concentration of 1% Is more preferably in the range of 50 to 85 ° C.

The stabilizer (C) has a cloud point measured by dissolving the stabilizer (C) in water to a concentration of 1%, and the stabilizer (C) has a concentration of 10 in a 25% aqueous butyl carbitol solution. It is more preferable that at least one of the cloud points measured by dissolving so as to be in the range of 40 to 85 ° C. is in the range of 40 to 85 ° C. Within this range, the addition of a small amount improves the mechanical stability and also provides good storage stability. Furthermore, since the flowable temperature of the stabilizer itself is low, it is advantageous in terms of handling.

Further, the stabilizer (C) preferably has an HLB of 10-15. If the HLB is lower than 10, the mechanical stability improving effect which is the object of the present invention is not sufficient. Moreover, when HLB exceeds 15, there exists a tendency to reduce a storage stability. A more preferable HLB range is 12 to 14. Within this range, an aqueous dispersion excellent in mechanical stability, storage stability, and viscosity stability in a wider temperature range can be obtained.

The aqueous fluoropolymer dispersion of the present invention preferably contains 0.05 to 5.0 parts by mass of the stabilizer (C) with respect to 100 parts by mass of the fluoropolymer (A). If the addition amount is small, the effect of improving the mechanical stability which is the object of the present application is not sufficient. Moreover, when the addition amount exceeds this range, the storage stability tends to be impaired, and when the temperature is raised, the viscosity of the aqueous dispersion tends to increase. Furthermore, a preferable range is 0.1-1.0 mass part. Within this range, an aqueous dispersion having excellent mechanical stability, storage stability, and viscosity stability over a wide temperature range can be obtained.

Fluoropolymer (A) is polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, polyvinylidene fluoride, ethylene / tetrafluoroethylene. It is preferably at least one polymer selected from the group consisting of a copolymer and an ethylene / chlorotetrafluoroethylene copolymer, and more preferably polytetrafluoroethylene.

The fluoropolymer (A) is preferably particles having an average particle size of 0.05 to 0.50 μm. If the average particle size is less than 0.05 μm, the mechanical stability and storage stability of the aqueous dispersion may be inferior, and the viscosity of the system may be very high, resulting in poor handling. If the average particle diameter exceeds 0.50 μm, the stability of the aqueous dispersion may be extremely lowered. Moreover, when a coating film is formed from an aqueous dispersion, the smoothness of the coating film appearance may be reduced, or the adhesion may be reduced. A more preferable upper limit is 0.35 μm, and a more preferable lower limit is 0.10 μm. If it is 0.25 micrometer or more, when a coating material is prepared from aqueous dispersion liquid, the film thickness adjustment at the time of application is easy, and the coating excellent in especially thick coating property can be prepared.

The average particle diameter is determined by measuring the transmittance of 550 nm projection light with respect to the unit length of the fluoropolymer aqueous dispersion whose resin solid content concentration is adjusted to 0.22% by mass, and the fixed direction diameter in a transmission electron micrograph. Based on the calibration curve with the average particle diameter determined in the above, it is determined from the transmittance.

The mechanical stability is a property that hardly produces an aggregate that cannot be redispersed even when vibration or shearing force is applied by a pump, a stirring blade, or the like during liquid feeding or redispersion.

The production method of the fluoropolymer (A) is not particularly limited, but is obtained by emulsion polymerization in the presence of the fluorine-containing anionic surfactant (E) in that the production efficiency is high and stable production is possible. It is preferable that

In the aqueous fluoropolymer dispersion of the present invention, the solid content concentration of the fluoropolymer (A) is preferably 30 to 75% by mass, more preferably 40 to 65% by mass, and 50 to 65% by mass. More preferably.

The aqueous fluoropolymer dispersion of the present invention preferably further contains (D) a nonionic surfactant (excluding the stabilizer (C)). The nonionic surfactant is preferably a nonfluorinated nonionic surfactant.

The nonionic surfactant (D) is represented by the following general formula (4)
_{^{R 2 O- (A 2 O)}} n -H (4)
(In the formula, A ² O represents an oxyalkylene group having 2 to 18 carbon atoms. N represents an average number of added moles of the oxyalkylene group and is an integer of 1 to 50. R ² represents the number of carbon atoms. Represents a linear alkyl group having 14 to 20 carbon atoms or a linear or branched alkyl group having 8 to 13 carbon atoms.)
Furthermore, as R ² , a hydrocarbon group having 13 carbon atoms having a branched structure is preferable from the viewpoint of improving the stability of the aqueous dispersion, and butene 3 can be reduced in that an irritating odor can be reduced during the firing process. What consists of a monomer is preferable.

A ² O in Formula (4) is preferably an oxyalkylene group having 2 to 4 carbon atoms, and is an oxyalkylene group having 3 to 25 oxyethylene units and 0 to 5 oxypropylene units. Is more preferable.

Examples of the nonionic surfactant (D) include polyoxyethylene alkylphenol surfactants (for example, Triton X (trade name) manufactured by Union Carbide), and polyoxyethylene alkyl ether surfactants. Polyoxyethylene alkyl ether surfactants are preferred.

Examples of the polyoxyethylene alkyl ether surfactant include polyoxyethylene tridecyl ether, polyoxyethylene octyl ether, polyoxyethylene lauryl ether, polyoxyethylene stearyl ether and the like.

Such polyoxyethylene alkyl ether surfactants include Dispanol TOC (manufactured by NOF Corporation), Leocol TD-90 (manufactured by Lion Corporation), Genapol X080 (manufactured by Clariant Corporation), Nonion C-13 (NOF Corporation) Nonionic EH205.5 (manufactured by NOF Corporation), Emulgen 109P (manufactured by Kao Corporation), Leox WC-145 (manufactured by Lion Corporation), Rutensol TO-8 (manufactured by BASF Corporation), Neugen TDS-80 (Daiichi Kogyo) (Manufactured by Pharmaceutical Co., Ltd.), nonionic EAD-13 (manufactured by NOF Corporation), and nonionic EAD-15 (manufactured by NOF Corporation) (all are trade names).

The nonionic surfactant (D) can be used when the aqueous dispersion described later is phase-separated and concentrated. The aqueous dispersion of the present invention may contain the nonionic surfactant (D) used in the phase separation concentration. On the other hand, whether or not the phase separation and concentration can be performed using only the stabilizer (C) in the present invention is not necessarily important, but a stabilizing effect is exhibited even in a compound in which phase separation is impossible. When there is the above difference, it can be cited as one of the differences when the stabilizer (C) and the nonionic surfactant (D) are compared.

The aqueous fluoropolymer dispersion of the present invention preferably contains 1 to 20 parts by mass of a nonionic surfactant (D) with respect to 100 parts by mass of the fluoropolymer (A).

The content (N) of the nonionic surfactant (D) was obtained by taking about 1 g (Xg) of a sample in an aluminum cup having a diameter of 5 cm and heating it at 100 ° C. for 1 hour. The heating residue (Yg) thus obtained is calculated from the formula: N = [(Y−Z) / Z] × 100 (%) from the heating residue (Zg) heated at 300 ° C. for 1 hour.

The aqueous fluoropolymer dispersion of the present invention has the following steps:
(I) A fluoromonomer, an aqueous medium (B) and a fluorine-containing anionic surfactant (E) are charged into a reaction vessel,
(Ii) polymerization is initiated by adding a polymerization initiator to the reaction vessel;
(Iii) Continue the polymerization by adding additional monomer to the reaction vessel;
(Iv) terminating the polymerization by releasing the pressure in the reaction vessel;
(V-1) recovering an aqueous dispersion containing the fluoropolymer (A), the aqueous medium (B) and the fluorine-containing anionic surfactant (E),
(Vi) The stabilizer (C) can be suitably produced by a production method including adding the stabilizer (C) to the aqueous dispersion to obtain the aqueous dispersion of the present invention.

After recovering the aqueous dispersion, that is, after step (v-1), (v-2) adding the nonionic surfactant (D) to remove the fluorine-containing anionic surfactant (E) (V-3) It is also preferable to add and concentrate the nonionic surfactant (D). Particularly from the economical and environmental viewpoints, it is preferable to remove, recover and reuse the fluorine-containing anionic surfactant (E). Removal and concentration can be performed by a known method such as an ion exchange resin method, a phase separation concentration method, an ultrafiltration method, or an electric concentration method.
The aqueous fluoropolymer dispersion obtained by removing or concentrating preferably has a fluorine-containing anionic surfactant (E) content of less than 500 ppm based on the solid content mass of the fluoropolymer (A). Furthermore, it is preferable that it is 200 ppm or less, and it is more preferable that it is 100 ppm or less. The lower limit is not particularly limited, but may be 0.1 ppm or more.

As the monomer, it is preferable to use at least one monomer selected from the group consisting of tetrafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, chlorotrifluoroethylene, vinylidene fluoride, and ethylene. Other than these monomers, it can be selected according to the composition of the target fluoropolymer.

The aqueous fluoropolymer dispersion of the present invention contains ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1, Polyhydric alcohols such as 5-pentanediol, 2-butene-1,4-diol, glycerin, 2-ethyl-2-hydroxymethyl-1,3-propanediol, 1,2,6-hexanetriol, triethylene glycol May be included. The film-forming property is improved by including a polyhydric alcohol.

In this specification, the content of the fluorine-containing anionic surfactant (E) is determined by performing high-performance liquid chromatography (HPLC) after adding Soxhlet extraction by adding an equal amount of methanol to the fluoropolymer aqueous dispersion. It can obtain | require by performing on condition of this. In calculating the content of the fluorinated anionic surfactant, a calibration curve obtained by HPLC measurement of the fluorinated anionic surfactant aqueous solution with a known content under the above eluate and conditions is used.

(Measurement condition)
Column; ODS-120T (4.6φ × 250 mm, manufactured by Tosoh Corporation)
Developing solution: acetonitrile / 0.6 mass% perchloric acid aqueous solution = 1/1 (vol / vol%)
Sample volume: 20 μL
Flow rate: 1.0 ml / min Detection wavelength: UV 210 nm
Column temperature: 40 ° C

The fluorine-containing anionic surfactant (E) is a compound having a fluorine atom and exhibiting surface activity. Examples of the fluorine-containing anionic surfactant (E) include perfluorocarboxylic acid or a salt thereof, perfluorosulfonic acid or a salt thereof, and a fluoroether compound. Examples of the fluorocarboxylic acid include perfluoroalkyl carboxylic acids such as perfluorooctanoic acid.

As fluorine-containing anionic surfactant (E), general formula (5)
Rf ¹ -Y ¹ (5)
(In the formula, Rf ¹ represents a linear or branched fluoroalkyl group having 2 to 12 carbon atoms into which a divalent oxygen atom may be inserted, and Y ¹ represents —COOM ¹ , —SO ₃ M ² , Represents —SO ₂ NM ³ M ⁴ or —PO ₃ M ⁵ M ^{6. The} above M ¹ , M ² , M ³ , M ⁴ , M ⁵ and M ⁶ are the same or different and represent H or a monovalent cation. .)
The fluorine-containing anionic surfactant represented by these is preferable.
Examples of the monovalent cation include —Na, —K, —NH _{4 and the} like. Rf ¹ is more preferably a linear or branched fluoroalkyl group having 2 to 6 carbon atoms into which a divalent oxygen atom may be inserted.

The Y ^1, -COOH, -COONa, preferably -COOK or -COONH _4, -COONH ₄ is more preferable.

As fluorine-containing anionic surfactant (E), general formula (6)
_{CF 3 - (CF 2) n1} -Y 1 (6)
(Wherein, n1 represents an integer of 1 to 5, Y ¹ is the same. As above) fluorinated anionic surfactant represented by the general formula (7)
^{Rf 2 O-Rf 3 O-} Rf 4 -Y 1 (7)
(Wherein Rf ² represents a fluoroalkyl group having 1 to 3 carbon atoms, Rf ³ and Rf ⁴ each independently represents a linear or branched fluoroalkylene group having 1 to 3 carbon atoms, and Rf ² , Rf ³ And Rf ⁴ has a total of 6 or less carbon atoms, and Y ¹ is the same as above.

Examples of the fluorine-containing anionic surfactant represented by the general formula (6) include CF ₃ (CF ₂ ) ₄ COONH ₄ , CF ₃ (CF ₂ ) ₃ COONH ₄ , and CF ₃ (CF ₂ ) ₂ COONH _4. , CF ₃ (CF ₂ ) ₃ SO ₃ Na, CF ₃ (CF ₂ ) ₃ SO ₂ NH _{2 and the} like.

Examples of the fluorine-containing anionic surfactant represented by the general formula (7) include, for example, the general formula CF ₃ O—CF (CF ₃ ) CF ₂ O—CX ¹ (CF ₃ ) —Y ^1.
(Wherein X ¹ represents H or F, and Y ¹ is the same as above), a fluorine-containing anionic surfactant represented by the general formula CF ₃ O—CF ₂ CF ₂ CF ₂ O—CFX ¹ CF ₂ -Y ¹
(Wherein X ¹ represents H or F, and Y ¹ is the same as above), a fluorine-containing anionic surfactant represented by the general formula CF ₃ CF ₂ O—CF ₂ CF ₂ O—CFX ¹ − Y ¹
(Wherein, X ¹ represents H or F, and Y ¹ is the same as above), and the like.
One type of fluorine-containing anionic surfactant (E) may be used, or two or more types may be used in combination.

The aqueous fluoropolymer dispersion of the present invention can preferably contain an anionic surfactant for the purpose of adjusting the viscosity of the aqueous dispersion or for improving the miscibility of pigments, fillers and the like. The anionic surfactant can be appropriately added within a range where there is no problem in terms of economy and environment.

The aqueous fluoropolymer dispersion of the present invention comprises at least one surfactant selected from the group consisting of the above-mentioned fluorine-containing anionic surfactant (E) and non-fluorinated anionic surfactant (F). May be included. These surfactants can be added to the aqueous dispersion together with the stabilizer (C) in step (vi).

The total content of the fluorinated anionic surfactant (E) and the non-fluorinated anionic surfactant (F) is 0 to 0.5 mass relative to the solid content mass of the fluoropolymer (A). %, And more preferably 0.01 to 0.1% by mass. If it is more than this, the viscosity adjusting effect will be lost, and the mechanical stability and storage stability of the aqueous dispersion may be impaired.

Examples of the non-fluorinated anionic surfactant (F) include sulfosuccinic acid alkyl ester, sulfosuccinic acid alkyl ester salt, sulfosuccinic acid fluoroalkyl ester, sulfosuccinic acid fluoroalkyl ester salt, and pKa of less than 4 It is preferable that the surfactant is at least one surfactant selected from the group consisting of non-fluorinated anionic surfactants.

Examples of the sulfosuccinic acid alkyl ester and the sulfosuccinic acid alkyl ester salt include, for example, the following general formula (I):
^{_{R 11 -OCOCH (SO 3 Z 1}} ) CH 2 COO-R 12 (I)
(Wherein R ¹¹ and R ¹² are the same or different and each represents an alkyl group having 4 to 12 carbon atoms, and Z ¹ represents an alkali metal, an alkaline earth metal, or NH ₄ ). Is mentioned.

The sulfosuccinic acid fluoroalkyl ester and the sulfosuccinic acid fluoroalkyl ester salt include the following general formula (II):
_{^{Rf 11 -R 13 -OCOCH (SO 3}} Z 1) CH 2 COO-R 14 -Rf 12 (II)
(In the formula, Rf ¹¹ and Rf ¹² are the same or different and each represent a perfluoroalkyl group having 1 to 6 carbon atoms optionally having a hydrogen atom, and R ¹³ and R ¹⁴ are the same or different. And an alkylene group having 1 to 5 carbon atoms, and Z ¹ represents an alkali metal, an alkaline earth metal, or NH ₄ ).

Examples of R ¹¹ and R ¹² in the general formula (I) include n-butyl, iso-butyl, sec-butyl, n-pentyl, iso-pentyl, neopentyl, tert-pentyl, n-hexyl, and iso-hexyl. , Tert-hexyl, n-heptyl, iso-heptyl, tert-heptyl, n-octyl, iso-octyl, tert-octyl, n-nonyl, iso-nonyl, tert-nonyl, n-decynyl, 2-ethylhexyl, etc. A linear or branched alkyl group is mentioned. R ¹¹ and R ¹² are each preferably an alkyl group having 8 to 12 carbon atoms. In the general formula (II), Rf ¹¹ and Rf ¹² each preferably have 3 to 5 carbon atoms, and R ¹³ and R ¹⁴ each preferably have 1 to 2 carbon atoms. As Z ¹ in the general formulas (I) and (II), for example, Na, NH _{4 and the} like are preferable.

The non-fluorinated anionic surfactant (F) is preferably a sulfosuccinic acid alkyl ester represented by the general formula (I) or a salt thereof, and in the general formula (I), the R ¹¹ And R ¹² are the same or different and are preferably an alkyl group having 8 to 12 carbon atoms. Examples of the sulfosuccinic acid alkyl ester include di-n-octyl sulfosuccinic acid ester and di-2-ethylhexyl sulfosuccinic acid ester.

The non-fluorinated anionic surfactant (F) may be a non-fluorinated anionic surfactant having an acid group and a pKa of less than 4. The acid group is preferably at least one selected from the group consisting of a carboxyl group, a sulfonyl group, phosphoric acid and a salt thereof, and in particular, selected from the group consisting of a carboxyl group, a sulfonyl group and a salt thereof. It is preferable that it is at least one kind. In addition to the acid group, it may further have other groups such as a polyoxyalkylene group having 2 to 4 carbon atoms and an amino group. The amino group is not protonated.

The pKa is preferably 3 or less. In addition, as for said pKa, when an anionic surfactant dissociates multistep, the lowest value should just exist in this range among each value.

The non-fluorinated anionic surfactant having an acid group and a pKa of less than 4 is preferably a compound having a hydrocarbon as a main chain, for example, having 6 to 40 carbon atoms, preferably 8 to 8 carbon atoms. 20, more preferably those having a saturated or unsaturated aliphatic chain having 9 to 13 carbon atoms. The saturated or unsaturated aliphatic chain may be linear or branched, and may have a cyclic structure. The hydrocarbon may be aromatic or may have an aromatic group. The hydrocarbon may have a heteroatom such as oxygen, nitrogen and sulfur.

Non-fluorinated anionic surfactants having an acid group and a pKa of less than 4 include alkyl sulfonates, alkyl sulfates, alkylaryl sulfates and salts thereof; aliphatic (carboxylic) acids and salts thereof; alkyl phosphate esters Among them, those selected from the group consisting of sulfonic acids and carboxylic acids and salts thereof are preferred, and aliphatic carboxylic acids or salts thereof are preferred. As the aliphatic carboxylic acid or a salt thereof, for example, a saturated or unsaturated aliphatic carboxylic acid or a salt thereof having 9 to 13 carbon atoms, which may be substituted at the terminal H with —OH, is preferable. The carboxylic acid is preferably a monocarboxylic acid, and the monocarboxylic acid is preferably decanoic acid, undecanoic acid, undecenoic acid, lauric acid, or hydrododecanoic acid.

The aqueous fluoropolymer dispersion of the present invention contains an aqueous medium. As said aqueous medium, water may be used independently and it is good also as an aqueous mixed solvent used together with water-soluble compounds, such as water and alcohol.

If necessary, the aqueous fluoropolymer dispersion of the present invention may contain other resins as long as the characteristics of the present invention are not impaired.
The other resins are not particularly limited. For example, polyethylene oxide (dispersion stabilizer), polyethylene glycol (dispersion stabilizer), phenol resin, urea resin, epoxy resin, melamine resin, polyester resin, polyether resin, acrylic silicone. Examples thereof include resins, silicone resins, silicone polyester resins, polyurethane resins and the like.
The aqueous fluoropolymer dispersion of the present invention may further contain additives that are used in general aqueous fluoropolymer dispersions for the purpose of improving paintability and properties of the resulting coating film.

The additive is not particularly limited and can be selected according to the use of the resulting coated article. For example, a leveling agent, solid lubricant, wood powder, quartz sand, carbon black, diamond, tourmaline, germanium, alumina , Silicon nitride, fluorite, clay, talc, extender pigments, various fillers, conductive fillers, glittering materials, pigments, fillers, pigment dispersants, anti-settling agents, moisture absorbers, surface conditioners, thixotropic agents , Viscosity modifier, anti-gelling agent, UV absorber, light stabilizer, plasticizer, anti-coloring agent, anti-skinning agent, anti-scratch agent, anti-mold agent, anti-bacterial agent, antioxidant, anti-static agent , A silane coupling agent, an antifoaming agent, a desiccant, and a repellency inhibitor.

Examples of the bright material include mica, metal powder, glass beads, glass bubbles, glass flakes, and glass fibers. When the aqueous fluoropolymer dispersion of the present invention contains such a bright material, a coating film having an excellent appearance can be formed. The content of the glittering material is preferably 0.1 to 10.0% by mass with respect to the solid content of the aqueous fluoropolymer dispersion.

The metal powder is not particularly limited, and examples thereof include powders of simple metals such as aluminum, iron, tin, zinc, gold, silver, and copper; powders of alloys such as aluminum alloy and stainless steel. The shape of the metal powder is not particularly limited, and examples thereof include particles and flakes. The aqueous fluoropolymer dispersion of the present invention may be a clear paint not containing these coloring components.

Examples of the viscosity modifier include methyl cellulose, alumina sol, polyvinyl alcohol, carboxylated vinyl polymer and the like.

Examples of the antifoaming agent include toluene, xylene, nonpolar solvents such as hydrocarbons having 9 to 11 carbon atoms, and silicone oil.

Examples of the desiccant include cobalt oxide.

The aqueous fluoropolymer dispersion of the present invention can be suitably used as a coating, can be used as a top coating, and can also be used as an intermediate coating. It can also be used as a lining paint.

As the coating method, various conventional coating methods can be employed, and examples thereof include a dipping method, a spray method, a roll coating method, a doctor blade method, a spin flow coating method, and a curtain flow coating method.

The aqueous fluoropolymer dispersion of the present invention may be directly coated on a substrate, but in order to improve the adhesion, it is desirable to provide a primer layer and coat it thereon. Although it does not specifically limit as a base material, For example, various metals, enamel, glass, various ceramics can be employ | adopted, and in order to improve adhesiveness, it is preferable to roughen the surface by a sandblasting method etc.

The aqueous fluoropolymer dispersion applied to the substrate is then dried. The aqueous fluoropolymer dispersion of the present invention is characterized in that mud cracks do not occur in this drying stage. Drying may be performed under normal conditions, and varies depending on the boiling point of the polyhydric alcohol (c) to be used, but preferably reaches room temperature to 150 ° C., more preferably 80 to 150 ° C. for 5 to 20 minutes to reach touch drying. .

The dried coating film is fired (processed). The firing (processing) temperature and time vary depending on the type and melting temperature of the fluororesin, but are, for example, higher than the melting temperature of the fluororesin, usually at 360 to 415 ° C for 5 to 30 minutes.

In the case of providing a primer layer, a method of applying, drying and baking the fluoropolymer aqueous dispersion of the present invention after applying, drying and baking the primer (2-coat 2-bake method) may be used, or after applying and drying the primer. A method of applying and drying the aqueous fluoropolymer dispersion of the present invention and firing both at the same time (2-coat, 1-bake method) may be used, or the glittering material which is the aqueous fluoropolymer dispersion of the present invention after applying and drying the primer A method of coating and drying an intermediate coating material containing a coating material, and further applying and drying a top coating material, which is a clear coating material other than the aqueous fluoropolymer dispersion of the present invention, and baking these simultaneously (3-coat 1-bake) Act). In addition, after the primer application, coating with an intermediate coating material containing a glittering material and a top coating material that is a clear coating material, which are aqueous fluoropolymer dispersions of the present invention, may be sequentially performed.

The coated article exemplified below can be produced by coating the aqueous fluoropolymer dispersion of the present invention. Examples of the coated article include frying pans, grill pans, pressure cookers, other various pans, rice cookers, rice cookers, ovens, hot plates, baking molds, kitchen knives, gas tables, etc .; electric pots, ice trays Food industry containers such as kneading rolls, rolling rolls, conveyors, hoppers, etc .; rolls for office automation equipment [OA], belts for OA, separation nails for OA, paper rolls, calendar rolls for film production, etc. Industrial goods; Molds for molding polystyrene foam, molds, molds such as molds and molds for plywood / decorative board production; kitchen articles such as range hoods; frozen food production equipment such as conveyor belts; saws, files, Tools such as dies and cutters; Household items such as irons, scissors and knives; metal foils and electric wires; plain bearings such as food processing machines, packaging machines, and textile machines; Merah watches sliding part; pipes, valves, automobile parts, snow plow shovel such as bearings, plow, chute, ship bottom, boiler, industrial containers (particularly for semiconductor industry) and the like.

As the use of the aqueous fluoropolymer dispersion of the present invention, it is also impregnated by impregnating and drying a porous support such as a nonwoven fabric and a resin molded article, and preferably firing, on a substrate such as glass. After coating and drying, cast film made by immersing in water as needed, peeling off the substrate to obtain a thin film, and the like can be mentioned. Examples of these applications include aqueous dispersion paints, electrode binders Agents, water repellents for electrodes, and the like.

The aqueous fluoropolymer dispersion of the present invention is also preferably used as a processing aid. When used as a processing aid, mixing the fluoropolymer aqueous dispersion of the present invention with a host polymer, etc. improves the melt strength during the host polymer melt processing, and the mechanical strength, electrical properties, and difficulty of the resulting polymer. It is possible to improve the flammability, the dripping prevention property, and the slidability.

When the fluoropolymer (A) is polytetrafluoroethylene, the aqueous fluoropolymer dispersion of the present invention is also preferably used as a processing aid after being combined with a hot-melt processable fluororesin. Examples of the aqueous fluoropolymer dispersion of the present invention include JP-A-11-49912, JP-A-2003-24693, US Pat. No. 5,804,654, JP-A-11-29679, and JP-A-2003-2980. It is suitable as a raw material for PTFE described in the publication. The aqueous fluoropolymer dispersion of the present invention is not inferior to the processing aids described in the above publications.

When the fluoropolymer (A) is polytetrafluoroethylene, the aqueous fluoropolymer dispersion of the present invention is co-coagulated by mixing with an aqueous dispersion of a heat-melt processable fluororesin and coagulating it. It is also preferable. The co-coagulated powder is suitable as a processing aid. Examples of the heat-melt processable fluororesin include FEP, PFA, ETFE, and EFEP, among which FEP is preferable.

The aqueous fluoropolymer dispersion of the present invention is also preferably used as a dust control agent when the fluoropolymer (A) is polytetrafluoroethylene. The dust suppressing agent is mixed with a dusting substance, and the mixture is subjected to a compression-shearing action at a temperature of 20 to 200 ° C., thereby fibrillating polytetrafluoroethylene to suppress dust of the dusting substance. It can be used in a method, for example, a method disclosed in Japanese Patent No. 2827152, Japanese Patent No. 2538783 and the like. The dust suppression treatment agent is suitably used for dust suppression treatment in the fields of building materials, soil stabilization materials, solidification materials, fertilizers, landfill disposal of incinerated ash and harmful substances, explosion-proof fields, cosmetics fields, and the like.

The aqueous fluoropolymer dispersion of the present invention can be suitably used for, for example, the dust suppressing treatment composition described in International Publication No. 2007/004250, and the dust suppression described in International Publication No. 2007/000812. It can also be suitably used for a processing method.

When the fluoropolymer (A) is polytetrafluoroethylene, the aqueous fluoropolymer dispersion of the present invention is also preferably used as a raw material for obtaining polytetrafluoroethylene fibers by a dispersion spinning method (Dispersion Spinning method). The dispersion spinning method includes mixing the polytetrafluoroethylene aqueous dispersion and the matrix polymer aqueous dispersion, and extruding the mixture to form an intermediate fiber structure. The intermediate fiber structure Is a method of decomposing the matrix polymer and sintering polytetrafluoroethylene particles to obtain polytetrafluoroethylene fibers.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited only to these examples. Hereinafter, “%” and “part” represent mass% and mass part, respectively.

Measuring method (1) Average particle diameter The transmittance of 550 nm projection light with respect to the unit length of the fluoropolymer aqueous dispersion whose resin solid content concentration is adjusted to 0.22% by mass, and the constant direction diameter in the transmission electron micrograph. Based on the calibration curve with the average particle diameter determined by measurement, it was determined from the transmittance.

(2) Fluoropolymer concentration (P)
About 1 g (X) of the sample was taken in an aluminum cup having a diameter of 5 cm, dried at 100 ° C. for 1 hour, and further dried at 300 ° C. for 1 hour, based on the heating residue (Z): P = Z / X × 100 ( %).

(3) Concentration of fluorinated surfactant After adding Soxhlet extraction by adding an equal amount of methanol to the obtained aqueous dispersion, high performance liquid chromatography [HPLC] was carried out under the following conditions. In calculating the fluorine-containing surfactant concentration, a calibration curve obtained by HPLC measurement with a known concentration of the fluorine-containing surfactant at the above eluate and conditions was used.
(Measurement condition)
Column: ODS-120T (4.6φ × 250 mm, manufactured by Tosoh Corporation)
Developing solution: acetonitrile / 0.6 mass% perchloric acid aqueous solution = 1/1 (vol / vol%)
Sample volume: 20 μL
Flow rate: 1.0 ml / min Detection wavelength: UV 210 nm
Column temperature: 40 ° C

(4) Content of nonionic surfactant (N)
About 1 g (Xg) of the sample was put in an aluminum cup having a diameter of 5 cm, and the heating residue (Yg) heated at 100 ° C. for 1 hour, and the obtained heating residue (Yg) was further heated at 300 ° C. for 1 hour. The amount obtained by subtracting the stabilizer from the amount calculated from the formula: N = [(Y−Z) / X] × 100 (%) from the heating residue (Zg) was defined as the content of the nonionic surfactant.
The stabilizer was calculated based on the amount added during preparation.

(5) Viscosity Using a B-type rotational viscometer (manufactured by Tokyo Keiki Co., Ltd.), the viscosity at 25 ° C. or 35 ° C. was measured according to JIS K 6893.

(6) Mechanical stability 100 ml of fluoropolymer aqueous dispersion maintained at 35 ° C. is circulated for 20 minutes under the condition of 1500 ml / min with a diaphragm pump equipped with a vinyl chloride tube having an inner diameter of 8 mm and an outer diameter of 11 mm, and then 200 mesh. The mesh-up amount when filtered using a SUS net was measured as a ratio (mass%) to the fluoropolymer amount contained in the used fluoropolymer aqueous dispersion.

(7) A storage-stable fluoropolymer aqueous dispersion (500 ml) was placed in a plastic container and allowed to stand at 25 ° C. for 3 months or in a constant temperature room at 40 ° C. for 1 month. After standing, the mixture is gently stirred and filtered through a stainless steel 400 mesh, and the agglomerate remaining on the mesh is dried at 300 ° C. for 1 hour, and the ratio of the agglomerated content to the resin solid content is determined based on the original fluoropolymer aqueous dispersion. (Based on the fluoropolymer in the liquid) and expressed in 100 minutes. Those with poor storage stability generate a large amount of agglomerates.

Production Example 1
Nonionic surfactant in aqueous PTFE dispersion 1 (average particle size 274 nm, PTFE concentration: 22%, fluorine-containing anionic surfactant amount: 4280 ppm of PTFE) obtained in Example 8 of JP-A-2005-036002 agent _{(C 13 H 27 - (OE} ) n -OH, hydrophobic groups butene trimer, product name TDS80, Dai-ichi Kogyo Seiyaku Co., Ltd.) was added, the nonionic surfactant concentration relative PTFE100 parts by 10 A dispersion having a mass part was prepared. Subsequently, 250 ml of an OH-type anion exchange resin Amberjet AMJ4002 (trade name, manufactured by Rohm and Haas) was packed, and the above PTFE aqueous dispersion 1 was added to a column having a diameter of 20 mm adjusted to 40 ° C. with SV = 1 was passed through. Furthermore, a nonionic surfactant was added to the aqueous dispersion obtained by passing the solution so as to have a concentration of 20%, and the mixture was kept at 63 ° C. for 3 hours, and separated into the supernatant phase 1 and the concentrated phase 1 did. Concentrated phase 1 was recovered and used as PTFE aqueous dispersion 2.
The PTFE aqueous dispersion 2 has a fluoropolymer concentration (PC) of 69.3%, a nonionic surfactant concentration (NC) of 2.8 parts by mass with respect to 100 parts by mass of PTFE, and the fluorine-containing anionic surfactant amount is It was 1 ppm with respect to PTFE.

Example 1
14.4 g of TDS80 was added to 650 g of the PTFE aqueous dispersion 2 obtained in Production Example 1, 1.4 g of stabilizer S-1 shown in Table 1 was further added, and 82 g of water was further added, so that the PC was 60%. An aqueous PTFE dispersion was prepared and evaluated for viscosity, mechanical stability, and storage stability. The results are shown in Table 1.

Examples 2-6
In Example 1, except that the stabilizer shown in Table 1 was added, an aqueous PTFE dispersion was prepared in the same manner as in Example 1, and the viscosity, mechanical stability, and storage stability were evaluated.

Comparative Example 1
A PTFE aqueous dispersion was prepared in the same manner as in Example 1 except that the stabilizer was not added in Example 1, and the viscosity, mechanical stability, and storage stability were evaluated. The results are shown in Table 1.

The aqueous fluoropolymer dispersion of the present invention can be suitably used for coating, impregnation, cast film production, spinning, eutectoid plating and the like.

Claims (10)

A fluoropolymer comprising (A) a fluoropolymer, (B) an aqueous medium, and (C) a stabilizer, wherein the stabilizer (C) is a compound represented by the following general formula (1) Aqueous dispersion.
R ¹ O— (A ¹ O) _m —H (1)
(In the formula, A ¹ O represents an oxyalkylene group having 2 to 4 carbon atoms. M represents an average number of added moles of the oxyalkylene group and is an integer of 1 to 50. R ¹ represents the following formula ( 2)

It is an alkyl group represented by these. ) Stabilizer (C) is a fluoropolymer aqueous dispersion according to claim 1 Symbol placement cloud point is 40 to 85 ° C.. Fluoropolymer (A) is polytetrafluoroethylene, tetrafluoroethylene / hexafluoropropylene copolymer, tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer, polychlorotrifluoroethylene, polyvinylidene fluoride, ethylene / tetrafluoroethylene. The aqueous fluoropolymer dispersion according to claim 1 or 2, which is at least one polymer selected from the group consisting of a copolymer and an ethylene / chlorotetrafluoroethylene copolymer. The fluoropolymer aqueous dispersion according to claim 1, 2 or 3 , wherein the solid content concentration of the fluoropolymer (A) is from 30 to 75 mass%. Fluoropolymer (A) according to claim 1, 2, 3 or 4 aqueous fluoropolymer dispersion according containing 0.05 to 5.0 parts by weight of stabilizer, relative to 100 parts by weight (C). The aqueous fluoropolymer dispersion according to claim 1, 2, 3, 4, or 5 , further comprising (D) a nonionic surfactant (excluding the stabilizer (C)). The fluoropolymer aqueous dispersion according to claim 6, wherein the nonionic surfactant (D) is a compound represented by the following general formula (4).
_{^{R 2 O- (A 2 O)}} n -H (4)
(In the formula, A ² O represents an oxyalkylene group having 2 to 18 carbon atoms. N represents an average number of added moles of the oxyalkylene group and is an integer of 1 to 50. R ² represents the number of carbon atoms. Represents a linear alkyl group having 14 to 20 carbon atoms or a linear or branched alkyl group having 8 to 13 carbon atoms.) The aqueous fluoropolymer dispersion according to claim 6 or 7 , comprising 1 to 20 parts by mass of a nonionic surfactant (D) with respect to 100 parts by mass of the fluoropolymer (A). A paint comprising the aqueous fluoropolymer dispersion according to claim 1, 2, 3, 4, 5, 6, 7 or 8 . Use of the aqueous fluoropolymer dispersion according to claim 1, 2, 3, 4, 5, 6, 7 or 8 as a coating material.