JP3080449B2 - Metal-coated fluororesin powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal-coated fluororesin powder.

[0002]

2. Description of the Related Art Fluororesin powder has a number of excellent properties such as water repellency, chemical stability, thermal stability, low friction, and weather resistance. Used in a wide range of fields. Conventionally, various types of fluororesin powder are commercially available, for example, polytetrafluoroethylene (PTFB), ethylene-tetrafluoroethylene copolymer (ETFE), and tetrafluoroethylene-6-fluoropropylene Copolymer (FEP), ethylene-3-fluoroethylene-6-fluoropropylene copolymer (FEP), ethylene-3-fluoroethylene chloride copolymer (ECTFE), polyvinylidene fluoride (PVDF), tetrafluoroethylene -Perfluoroalkyl vinyl ether copolymer (PFA)
There is a powder of a fluororesin, etc., which is commercially available in the form of ground powder or a dispersion in which the powder is dispersed in an aqueous solution containing a surfactant. By the way, since such fluororesin powder has very high water repellency, it is very difficult to disperse it in water or an aqueous solution, and it is necessary to use a large amount of a surfactant. Problem. For this purpose, it has been proposed to coat the surface of a fluororesin powder with a thermosetting resin, metal, ceramics or a mixture thereof to make the surface hydrophilic (Japanese Patent Application Laid-Open No. 64-51454). However, with such a method, the powder surface is indeed hydrophilized and its wetting properties are improved, but there are drawbacks such as the excellent properties inherently possessed by the fluororesin cannot be fully utilized, and it is still satisfactory. Not something to do. For example, when the powder surface is coated with a thermosetting resin, the chemical stability and weather resistance of the fluororesin are sacrificed. When the metal is coated on the powder surface, the chemical stability and low friction property of the fluororesin are impaired. When coating ceramics on the powder surface, it is necessary to lower the curing temperature to 300 ° C or less, so that the properties of the ceramics cannot be fully utilized and the resulting powder surface has extremely poor chemical stability. Become. On the other hand, when the fluororesin powder is dispersed in an aqueous solution, a large amount of a surfactant of several percent or more is required, so that the resulting dispersion itself is contaminated with the surfactant, and its use is significantly limited. In addition, bubbles are very easy to form, and troubles caused by the foaming also occur. Furthermore, when attempting to apply metal plating to a fluororesin powder, the powder has extremely high water repellency, so it is very difficult to disperse the powder in a plating bath. Doing so requires the use of large amounts of surfactant and is not practical.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems found in the prior art, and provides excellent properties inherent to the fluororesin such as chemical stability, heat stability and low friction. Another object of the present invention is to make the fluororesin powder hydrophilic without impairing the weather resistance and to attach a metal to the surface thereof.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the fluororesin powder was coated with a film of a fluorine-containing compound having a hydrophilic group, and the coating layer was formed. When a metal is adhered through the metal powder, the metal-adhered fluororesin powder can be obtained without deteriorating the excellent properties inherent in the fluororesin, and the film formed on the powder surface has an adhesive property with the powder. The present invention was found to be very excellent, and the present invention was completed. That is, according to the present invention, there is provided a metal-adhered fluororesin powder characterized in that a metal is adhered to the surface of the fluororesin powder via a coating layer of a fluorine-containing compound having a hydrophilic group.

The fluororesin powder used in the present invention includes:
Conventionally known ones, for example, polytetrafluoroethylene, ethylene-tetrafluoroethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, ethylene-trifluorochloroethylene copolymer,
Examples thereof include polyvinylidene fluoride and a tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer. The average particle size of the fluororesin powder is usually
It is 0.1 to 100 μm, preferably 0.5 to 10 μm. In the present invention, first, a fluorine-containing compound having a hydrophilic group is attached to the surface of a fluororesin powder in a film form. The fluorine-containing compound having a hydrophilic group only needs to be in a liquid or solid state at room temperature, and includes a low molecular compound, an oligomer, a polymer, and the like. Further, these fluorine-containing compounds can exist in a cross-linked state on the surface of the powder particles. The fluorine-containing compound having a hydrophilic group to be attached to the powder surface is 1 to 1 with respect to the final product powder.
It is 10% by weight, preferably 2 to 6% by weight. As a method of forming a film by adhering and bonding a fluorine-containing compound having a hydrophilic group to the powder surface, a conventionally known method, for example,
In addition to chemical methods such as interfacial polymerization and interfacial reaction, phase separation from aqueous solutions, and physicochemical methods such as phase separation from organic solvents, air suspension coating, spray drying, etc. Is mentioned.

As the fluorine-containing compound having a hydrophilic group,
Hydrophobic part containing fluorine in the molecule, and those having a hydrophilic part having a hydrophilic group, those having some solubility in water or aqueous solution, preferably those which show substantially water insolubility Use is preferred. Examples of the hydrophilic group include a hydroxyl group, a carboxyl group, a sulfone group, a cyano group, a pyrrolidone group, an isocyanate group, an imidazole group, a phosphoric acid group, an N-substituted amide group, and an N-substituted group. And an amino group and a sulfonamide group. Further, an alkylene oxide such as ethylene oxide or propylene oxide may be added to the active hydrogen of the hydrophilic group.

The preferred fluorine-containing compound having a hydrophilic group used in the present invention is a fluorine-containing hydrophilic polymer. This can be obtained by copolymerizing a fluorine-containing ethylenically unsaturated monomer and a fluorine-containing hydrophilic group-containing vinyl monomer. Examples of the fluorine-containing monomer include tetrafluoroethylene, vinyl fluoride, vinylidene fluoride, monochlorotrifluoroethylene, dichlorodifluoroethylene, and hexafluoropropylene.

[0008] Preferred fluorine-containing monomers can be represented by the following general formula: CXY = CFZ (1) In the above formula, Z represents fluorine or hydrogen, and X and Y represent hydrogen, fluorine, chlorine and trifluoromethyl (—CF ₃ )
Selected from

Another preferred fluorine-containing monomer can be represented by the following general formula. In the above formula, R is hydrogen, fluorine, a methyl group, an ethyl group, a trifluoromethyl group (CF ₃ ) or pentafluoroethyl (C ₂ F ₅ ). Rf represents a perfluoroalkyl group having 4 to 21 carbon atoms.

On the other hand, as the hydrophilic group-containing monomer, the above-mentioned vinyl monomers having various hydrophilic groups and monomers obtained by adding an alkylene oxide, for example, ethylene oxide or propylene oxide, to the active hydrogen of the hydrophilic group are also preferable. is there. As in the case of vinyl acetate, those which give a hydrophilic group-containing copolymer by copolymerization followed by hydrolysis are also used. Specific examples of the hydrophilic monomer include vinyl alcohol, acrylic acid, methacrylic acid,
In addition to unsaturated carboxylic acids such as fumaric acid, maleic acid and itaconic acid, the following alkylene oxide adducts of acrylic acid and methacrylic acid can be mentioned.

[0011] In the above formula, R is hydrogen or a methyl group, and n and m are 1
Is an integer greater than or equal to. Each of the fluorinated monomer and the hydrophilic group-containing monomer may be one type or two or more types. Further, the fluorine-containing monomer and the hydrophilic group-containing monomer,
If necessary, another vinyl monomer, for example, an alkyl ester of acrylic acid or methacrylic acid, or an ester of acrylic acid or methacrylic acid with a polyhydric alcohol such as trimethylolpropane can be used in combination.

A copolymer of vinyl alcohol and a fluorine-containing monomer which is preferably used as a fluorine-containing hydrophilic polymer is obtained by saponifying a copolymer of vinyl acetate and a fluorine-containing monomer, and converting an acetate group contained in the copolymer into a hydroxyl group. Can be obtained by In this case, it is not always necessary to convert all of the acetate groups contained in the copolymer to hydroxyl groups, and the conversion of the acetate groups to hydroxyl groups may be performed to such an extent that the copolymer has hydrophilicity. The fluorine content of the fluorine-containing hydrophilic copolymer is based on weight,
Usually, it is 2% to 60%, preferably 10% to 60%, and more preferably 20% to 60%. If the fluorine content of the fluorine-containing hydrophilic copolymer is too high, the heat resistance is improved, but the hydrophilicity of the polymer is reduced. On the other hand, if the fluorine content is too low, the adhesiveness to the powder of the fluorine-containing hydrophilic copolymer decreases, and the heat resistance also decreases. In the fluorine-containing hydrophilic copolymer preferably used for making the powder hydrophilic, the hydrophilic group equivalent is generally 45 to 70.
0, preferably 60 to 500. When the hydrophilic group equivalent is less than 45, the solubility of the fluorinated hydrophilic copolymer becomes very large, and the copolymer is easily eluted from the powder with water, while when the hydrophilic group equivalent is larger than 700, the hydrophilicity becomes small. It becomes too much, and the hydrophilicity of the powder becomes insufficient.

Tables 1 and 2 show, for some copolymers, mol% of fluorine-containing monomer units, fluorine weight% (F-wt%) and hydrophilic group equivalent (Eq
-W). VOH is vinyl alcohol.

In the present specification, the hydrophilic group equivalent (Eq
-W) is the value obtained by dividing the molecular weight of the copolymer by the number of hydrophilic groups. The hydrophilic group equivalent shown below is calculated by the following equation. In the formula, A · x is a value obtained by multiplying the molecular weight of the fluorine-containing monomer by the number of moles x, while By · y is a value obtained by multiplying the molecular weight of the hydrophilic group-containing monomer by the number of moles y.

[0015]

[Table 1] Copolymer In the copolymer The molar ratio of in the copolymer Fluorine-containing monomer F-wt% Eq-W mol% of unit (CF ₂ = CF ₂ ) x / (VOH) y X = 1, Y = 40 2.4 4.2 45.5 1, 30 3.2 5.5 46.4 1, 20 4.8 7.9 48.0 1, 10 9.1 14.3 53 1, 4 20 27.5 68 1, 1 50 53.1 143 10, 1 91 72.8 1043 (CF ₂ = CFH) x / (VOH) y X = 1, Y = 40 2.4 2.1 44.6 1, 30 3.2 2.8 45.2 1, 20 4.8 4.1 46.2 1, 10 9.1 7.5 49 1, 4 20 − − 1, 1 50 33.6 107 10, 1 91 55.6 683 (CFH = CH ₂ ) x / (VOH) y X = 1, Y = 40 2.4 1.1 44.2 1, 30 3.2 1.4 45.6 1, 20 4.8 2.1 45.3 1, 10 9.1 4.0 47.6 1, 4 20 − − 1, 1 50 21.3 89 10, 1 91 37.8 503

[0016]

[Table 2] Copolymer In the copolymer The molar ratio of in the copolymer Fluorinated monomer F-wt% Eq-W Molar% of unit (CF ₂ = CFCl) x / (VOH) y X = 1, Y = 40 2.4 3.1 46.0 1 , 30 3.2 4.0 46.9 1, 20 4.8 5.8 48.9 1, 10 9.1 10.4 54.6 1, 4 20 − − 1, 1 50 35.8 159 10, 1 91 47.2 1208 (CF ₂ = CCl ₂ ) x / (VOH) y X = 1, Y = 40 2.4 2.0 46.6 1, 30 3.2 2.7 47.7 1, 20 4.8 3.8 50.0 1, 10 9.1 6.7 57 1, 4 20 − − 1, 1 50 20.8 183 10, 1 91 26.3 1442 (CF ₂ = CFCF ₃ ) x / (VOH) y X = 1, Y = 40 2.4 6.1 46.8 1, 30 3.2 7.9 48.0 1, 20 4.8 11.3 50.5 1, 10 9.1 19.6 58 1, 4 20 − − 1, 1 50 59.0 193 10, 1 91 73.9 1543

In order to adhere the fluorinated hydrophilic polymer to the powder surface, for example, a fluorinated hydrophilic copolymer is dissolved in an organic solvent such as alcohol, ketone, ester, amide or hydrocarbon, and The powder is immersed in the solution or the solution is sprayed on the powder surface and then dried. Alternatively, the solution of the fluoropolymer and the powder may be mixed, and the mixture may be freeze-dried by spray drying or ice-drying. Further, a monomer having a hydrophilic group and a fluorine-containing monomer may be polymerized on the powder surface. Thus, the fluorinated hydrophilic polymer adheres to the powder surface, and a powder that has been hydrophilized can be obtained. The amount of the fluorinated hydrophilic polymer adhered to the powder may be an amount sufficient to make the powder surface hydrophilic, and varies depending on the type of powder used, but usually the weight of the final product powder. 1 to 10% by weight, preferably 2 to 6% by weight.

The hydrophilicized fluororesin powder is impregnated with an organic solvent solution of a copolymer of a fluorine-containing monomer and a hydrophobic monomer such as vinyl acetate which can be converted into a hydrophilic group, and the powder is dried. Then, it can be produced by converting at least a part of the acetate group into a hydrophilic group.

The hydrophilic fluororesin powder obtained as described above has a structure in which a hydrophilic fluoropolymer is bonded to the surface in a film-like manner. This makes the surface of the powder hydrophilic. Elution of the polymer itself from the powder can be prevented by regulating the hydrophilic group equivalent of the hydrophilic fluoropolymer within an appropriate range and controlling the solubility of the polymer in water. The adhesive bonding force of the fluorine-containing hydrophilic copolymer to the fluororesin powder becomes strong by the action of fluorine atoms in the copolymer, and is maintained in a stable state for a long period of time.

The other fluorine-containing compound having a hydrophilic group preferably used in the present invention is a fluorine-containing surfactant.
Specific examples of this are shown below. _{RfCONHC 2 H 4 OC (C 2} H 4 O) nH (11) RfSO 2 NH 2 H 4 O (C 2 H 4 O) nH (12) RfC 2 H 4 OH (13) RfCOOH (14) RfC 2 H 4 N (CH ³ ) ² (15) In the above general formula, Rf is a perfluoro higher alkyl group, and has 8 or more carbon atoms, preferably 12 to 30 carbon atoms.
It is. N is an integer of 1 or more, preferably an integer of 2 to 5. These fluorinated surfactants, at room temperature,
It is liquid or solid. To attach the fluorinated surfactant to the powder surface, the fluorinated surfactant is dissolved in an organic solvent such as a halogenated hydrocarbon, ethyl acetate or acetone, and the powder is immersed in this solution. The solvent may be removed. The concentration of the fluorinated surfactant in the solution is 1 to 10% by weight, preferably 2 to 5% by weight.

The fluororesin powder coated with the fluorine-containing compound having a hydrophilic group obtained as described above has a hydrophilic surface and remarkably improved wettability. The superior properties it possesses are not compromised at all. This powder can be easily dispersed in water or an aqueous solution, and can be handled in the same manner as a conventional general hydrophilic powder.

Next, in the present invention, the fluororesin powder coated with the fluorine-containing compound having a hydrophilic group (hereinafter simply referred to as powder) is subjected to a metal adhesion treatment, for example, a chemical plating treatment. To deposit metal on the surface.
The chemical plating in this case may be performed according to a conventionally known method. That is, in the pretreatment step, a noble metal serving as a catalyst for chemical plating is attached to the powder surface.
As the noble metal, palladium, platinum, silver or the like is used, but palladium is preferable. As a method for attaching the noble metal, for example, a method in which the material is immersed in an aqueous solution of tin (II) chloride, washed with water, immersed in an aqueous solution of palladium chloride, and then washed with water can be adopted. Such pretreatment for chemical plating is a well-known technique.

Next, the powder which has been subjected to the pretreatment for chemical plating as described above is immersed in a chemical plating solution and subjected to chemical plating. The chemical plating solution generally contains a metal, a reducing agent, a complexing agent, a buffer, a stabilizer, and the like.
In this case, sodium hypophosphite, sodium borohydride, aminoborane, formalin, hydrazine, etc. are used as the reducing agent, and formic acid, acetic acid, succinic acid, citric acid, tartaric acid are used as complexing agents and buffers. , Malic acid, glycine, ethylenediamine, EDTA, triethanolamine, and sodium / potassium tartrate.

As the metal for plating, for example, gold, silver,
Platinum, rhodium, nickel, cobalt, tungsten,
Examples include various metals such as copper, zinc, and iron, and alloys thereof. When the metal of the alloy is deposited, a metal salt having a component composition corresponding to a desired alloy may be used as the metal salt to be added to the plating solution. In order to attach platinum or gold to the powder used in the present invention, or a metal formed of an alloy thereof or another metal that is difficult to form by chemical plating, cobalt, nickel,
It is preferable to attach a metal such as copper which can be easily formed by chemical plating (chemical reduction plating) in advance, and then perform chemical plating (chemical reduction plating, displacement plating, etc.) on the powder.

When platinum or an alloy containing platinum is adhered to a powder by a chemical plating method, chemical plating can be easily performed by using hydrazine hydrochloride as a reducing agent. Since the chemical plating solution containing platinum ions easily reduces platinum ions, it is difficult to selectively deposit platinum only on the object to be plated.
When hydrazine hydrochloride is used as the reducing agent, the stability of the plating solution is remarkably improved, and platinum can be selectively deposited only on the object to be plated. When hydrazine hydrochloride is used as the reducing agent, a platinum alloy, for example, a metal such as platinum-iridium or platinum-rhodium can be easily attached. A typical component composition of a chemical plating solution containing platinum ions is as follows. Chloroplatinic ^{acid: 3 × 1/10 3 ~7} × 1/10 3 mol /
1 Hydrazine hydrochloride: 0.1 to 0.3 mol / l pH: 3 to 4 Temperature: 30 ° C to 40 ° C

Further, as the chemical plating method used in the present invention, a composite plating method can be adopted. This composite plating method is a method of adhering a metal containing a fine powder such as a metal oxide, nitride or carbide, and uses a plating solution in which the fine powder is uniformly dispersed.

In the present invention, since a fluororesin powder coated with a fluorine-containing compound having a hydrophilic group is used as a raw material to be plated, a metal can be easily attached to the powder surface by a chemical plating method. Can be. The thickness of the metal layer formed on the powder surface by the chemical plating method is usually about 10 to 5 μm, and particularly 500 to 1 μm.
m. According to the present invention, the powder having the metal layer obtained as described above can be further subjected to chemical plating or electroplating, and a multilayer metal film can be formed on the powder surface. In the metal-adhered fluororesin powder of the present invention, the adhering metal is in any state other than the metal state, for example, oxide, sulfide, halide, nitride,
It can be in the form of a carbide or the like. Conventionally known reactions can be employed to convert the metal adhering to the powder into an oxide, sulfide, halide, nitride, carbide or the like.

[0028]

Next, the present invention will be described in more detail with reference to examples. Example 1 Polytetrafluoroethylene (PTFE) fine powder for lubrication (low molecular weight tetrafluoroethylene resin powder, manufactured by Daikin Industries, Ltd., Lubron L-2, particle diameter: 5 μm, bulk specific gravity: about 0.
35 g / cc) and 0.1 of a tetrafluoroethylene / vinyl alcohol copolymer (fluorine content: 27% by weight).
% Methyl alcohol solution with a resin solid content weight ratio of 10
The solution mixed at a ratio of 0: 0.5 was spray-dried in an atmosphere at 80 ° C. to obtain a fine powder whose particle surface was coated with a tetrafluoroethylene / vinyl alcohol copolymer. Next, this fine powder A was mixed with 2.5 mmol / l P
The resultant was placed in an aqueous d-colloid solution, stirred while applying ultrasonic waves, to uniformly adhere the Pd colloid to the surface of the fine powder A, and an activation treatment was performed. At this time, the amount of the Pd colloid was 0.03 mmol per 1 g of the fine powder A. After washing with water, it was put into a copper electroless plating bath and stirred. The composition of this copper plating bath was 0.015 mol of copper (II) sulfate pentahydrate.
/ L, sodium potassium tartrate tetrahydrate 0.04mo
1 / l, sodium hydroxide 0.12 mol / l, formaldehyde 0.4 mol / l. After plating, it was washed and dried to obtain a fine powder with copper plating. Particle size is about 6μ
m, the weight ratio of PTFE to Cu was about 4: 1.
This was further calcined in the air at 250 ° C. for 3 hours to obtain an ozone gas decomposition catalyst. This catalyst exhibited excellent performance of maintaining an ozone decomposition rate of 95% or more for 6 hours or more. Ozone gas used for sterilization, deodorization, and the like can be decomposed through the catalyst after use to prevent deterioration of the human body and environment.

Example 2 Fine powder A subjected to the hydrophilization treatment of Example 1 was placed in a solution containing 0.08 mol / l of stannous chloride and stirred to sensitize. After washing with water, 0.005 mol of PdCl ₂ is further added.
/ L and stirred to activate. This was placed in a silver electroless plating bath and stirred to perform silver plating. The plating bath was silver nitrate 0.07 mol / l, aqueous ammonia, and potassium sodium tartrate 0.2 mol / l. When the silver-plated powder was evaluated as a filler for a sterilizing filter, it exhibited sufficient sterilizing action, and even when used under high-pressure water for a long period of time, there was no peeling of the plated metal and sufficient adhesive strength. .

Example 3 The fine powder A subjected to the hydrophilization treatment of Example 1 was activated in the same manner as in Example 2, and was placed in a solder plating bath and agitated for plating. The composition of the solder plating bath is Na ₃ citrate · 2H ₂ O 0.34 mol
_{/ L, Na 2 EDTA · 2H} 2 O 0.08mol / l,
Na ₃ .H ₂ O 0.2 mol / l, SnCl ₂ .2H ₂ O
0.4 mol / l, PdCl ₂ 0.04 mol / l,
Ammonia water containing 0.04 mol / l of TiCl ₃ . Thus, a fine powder subjected to solder plating was obtained. Sufficient electric conduction can be achieved by using this as a bonding material when mounting electronic components such as ICs (bonding by CCB method) and chip components (chip capacitors, chip diodes, chip resistors, etc.) that are mounted face down on the board. And good joining with little deterioration of the joining part due to the temperature cycle was obtained. In this method, the electrode terminals of an IC chip or electronic component and the electrode terminals of a substrate are joined at 250 ° C. for 2 minutes using this solder plating powder. Only the solder melts, and the PTFE particles inside do not melt. Therefore, the contact between the surface of the electronic component and the substrate is prevented by the PTFE particles. In addition, the solder joint has a drum-like shape that is advantageous in terms of stress, and reliability has been improved.

Example 4 The fine powder A subjected to the hydrophilizing treatment of Example 1 was plated with Cu, and further, Ni was plated around the Cu plating layer to obtain a conductive powder. It had sufficient adhesion. The resistance value was a sufficiently low value of about 0.5Ω.

Example 5 Hard powder Ni was applied to the fine powder A subjected to the hydrophilic treatment of Example 1 to obtain a sliding material made of PTFE and Ni. Since the Ni portion and the PTFE portion were alternately present on the powder surface, a good sliding material utilizing the respective features was obtained.

[0033]

In the metal-adhered fluororesin powder of the present invention, the metal is adhered to the surface of the fluororesin powder via a coating layer of a fluorine-containing compound having a hydrophilic group formed in advance. The adhesion between the powder and the powder is very excellent, and the metal is evenly adhered to the irregularities on the powder surface. Furthermore, since the coating layer formed on the powder surface is a fluorine-containing compound, the characteristics of the fluororesin powder are not impaired. The metal-adhered fluororesin powder of the present invention can be used for electronic materials such as conductive powders and mechanical materials such as sliding materials. Furthermore, by changing the state of the metal adhering to the powder surface to an appropriate metal compound state such as an oxide, sulfide, or halide,
It can be used for various applications as a functional powder. For example, an oxide can be advantageously used as a catalyst by converting the attached metal to an oxide. Further, the fluororesin powder of the present invention can be easily dispersed in water or an aqueous solution, and can be used for applications such as pigments.

Claims (4)

(57) [Claims] 1. A metal-adhered fluororesin powder, wherein a metal is adhered to the surface of the fluororesin powder via a coating layer of a fluorine-containing compound having a hydrophilic group. 2. The powder according to claim 1, wherein said fluorine-containing compound is a fluorine-containing polymer. 3. The powder according to claim 1, wherein said fluorine-containing compound is a fluorine-containing surfactant. 4. The powder according to claim 1, wherein said metal is an oxide.