JPS62541A - Aqueous dispersion composition - Google Patents

Abstract

PURPOSE:To enable thick coating to be carried out and to smooth the surface of coating film, by using an aq. dispersion compsn. having specified physical properties comprising a copolymer of tetrafluoroethylene with a specified fluorovinyl ether. CONSTITUTION:A copolymer of tetrafluoroethylene with a fluorovinyl ether of the formula (wherein X is H, F; n is 0-7; m is 0-3), which has a fluorovinyl ether content of 1-10wt% is used. The title aq. dispersion compsn. contains said colloided copolymer particles having an average particle size of 0.3-1mum and a specified melt viscosity of 0.3-10.0X10<4> P as main component and is stabilized by an anionic or noninic surfactant. Pref. the copolymer is used in a quantity of 20-65% by weight based on that of the compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aqueous dispersion composition, and more particularly to an aqueous dispersion composition of a tetrafluoroethylene/fluorovinyl ether copolymer, in particular a method for coating a substrate with a non-stick property. Compositions suitable for application.

It is known to coat the surfaces of metals, ceramics, heat-resistant rubber, etc. with fluorocarbon polymers for various applications, and polytetrafluoroethylene (P
T F E), tetrafluoroethylene/hexafluoropropene copolymer (FEP), tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer (
PFA) etc. are used to take advantage of their properties such as non-adhesiveness, heat resistance, chemical resistance, and low coefficient of friction.

PTFE and FEP are commercially available as aqueous dispersion compositions, and are coated by spraying or dipping. Moreover, FEP and PFA are used in electrostatic powder coating, and are therefore commercially available as powders of 5 to 150 μm.

Examples of implementations of electrostatic powder coating include, for example, JP-A-55
As shown in No. 31494 and Japanese Patent Laid-open No. 58-24174, rolls of copying machines and the like are coated.

On the other hand, any of the PTFESFEPSPFAs can be prepared as an aqueous dispersion;
Examples of mixing an aqueous dispersion of EP or PFA and using it for coating are also known. (For example, Tokuko Sho 52-2153
No. 1, U.S. Pat. No. 4,252,859). However, there are almost no known examples of using a PFA aqueous dispersion alone for coating purposes.

PFA aqueous dispersion is disclosed in Japanese Patent Publication No. 48-20788, for example.
It is prepared by the method described in No. The aqueous dispersion prepared according to the method of this patent is usually subjected to melt processing after separating the polymer into pellets or powder, but as shown in Comparative Examples 1 to 3 below, When coating is performed using an aqueous dispersion composition, it is possible to coat only an extremely thin film, and if the film is coated thickly, so-called mud cracks occur. Moreover, the surface of the coating film is also rough.

The present invention aims to improve the above drawbacks of the PFA aqueous dispersion, and its gist is the general formula: % formula % (wherein, X is H or F, n is the number of O to 7, m is 0-3
is the number of ) A copolymer of fluorovinyl ether and tetrafluoroethylene represented by
lO'~10. Ox I O' voids, average particle size 0.
An aqueous copolymer resin dispersion composition containing colloidal copolymer particles of 3 to 1 μm as a main component and stabilized with an anionic or nonionic surfactant.

The composition of the present invention is composed of a colloidal aqueous dispersion of tetrafluoroethylene/fluorovinyl ether copolymer, and can be applied in thick coatings, resulting in a smooth coating surface. It is especially suitable for non-adhesive processing. Examples include fuser rolls for copying machines, rolls for food processing, trays, and cooking utensils.

The colloidal copolymer particles, which are a requirement of the present invention, have an average particle size of 0.3 to 1 μm and a specific melt viscosity (MV
) has a characteristic of 0.3 to 10.0×10′ voids.

Only with these characteristics can the objectives of the invention be achieved.

The composition of the present invention is characterized by thick coating processability and smoothness of the coating film, but the copolymer particles of the present invention are also larger than ever before as PFA, and this has a specific MV. , better thick coating processability and coating film smoothness are achieved.

When coating with the composition of the present invention, a coating film with a thickness of at least 25 μm or more (usually 35 μm or more) can be formed in one coating. Furthermore, the surface roughness is as small as 0.5 μm or less. The reality is that commercially available aqueous dispersion compositions of PTFE and FEP can only provide a coating film with a thickness of about 10 to 20 μm. With such a film thickness, for example, when processing a fuser roll for a copying machine, it is necessary to coat the film to a thickness that is the sum of the necessary film thickness and the amount of surface polishing after painting, but usually 25 μm or more is required. The film thickness is just insufficient. On the other hand, electrostatic coating using FEP or PFA powder results in a coating thickness exceeding 100 μm. but,
On the contrary, this is too thick, resulting in a large amount of cutting (resulting in loss of raw materials), which is uneconomical and requires a large number of man-hours.

When the surface roughness of the coating film formed by the composition of the present invention is small, it is often possible to put it into practical use without surface polishing. As a result of a detailed study of the physical properties of both particle size and MV, the inventor found that the MV is 0.3 to 10, OX I O' voids (preferably 0.4 to 5.0 xto' voids), and the average particle diameter is 0. The present inventors have found that a thickness of 0.3 to 1 μm (preferably 05 to 0.8 μm) is most suitable for the above purpose, and have completed the present invention.

Regarding MV, if it is too high than the above range, the surface roughness will be large even if the particle size is large, and mud cracks will be likely to occur. In this case as well, a large amount of the film must be removed, resulting in uneconomical problems, and the required film thickness cannot be obtained. Of course, if it is too low than the above range, the mechanical strength will be low and it will become brittle. Since the colloidally dispersed particles of the present invention are much larger than those commonly known, it is necessary to increase the viscosity of the composition to make it difficult to settle. Furthermore, it must have the property of being easy to redisperse even if it settles once. Therefore, anionic or nonionic surfactants or mixtures thereof are added to the composition.

Nonionic surfactants are typically produced by the reaction between ethylene oxide as a hydrophilic part and compounds such as propylene oxide, saturated and unsaturated aliphatic alcohols, and alkylphenols as hydrophobic parts. It is a thing. For example, oxyethylene, oxinobrobylene broth copolymer, 1-10(CtH40)a-(C3t(80)b-(C
2I-1,0)CH(moleculefftloooo ~4000
．． l8≦a+b+c≦85), 4 to 20), etc. are suitable. Examples of anionic surfactants include dialkyl sulfosuccinate, dodecylbenzenesulfonate,
Fatty acid soap etc. can be used. In addition, a water-soluble polymer such as sodium alginate or an inorganic salt may be added to increase the viscosity of the composition. Furthermore, in order to further improve film-forming properties, it is also possible to disperse and emulsify a water-insoluble organic solvent such as benzene, toluene, xylene, etc.

The amount of nonionic or anionic surfactant used as a stabilizer is suitably 3 to 20% by weight, preferably 4 to 10% by weight, based on the weight of the resin. If there is too much stabilizer, it will be difficult to volatilize during sintering and the coating performance will deteriorate. Furthermore, too much stabilizer and excessive thickener will make the painting process itself difficult. Typically, the viscosity of the compositions of the present invention will be between 50 and 1000 centivoise at 25°C, preferably between 100 and 1000 centivoise.
Preferably, it is adjusted to 400 centivoise.

Further, the amount of the copolymer resin mold in the composition is preferably 20 to 65% based on the total weight of the composition.

The composition of the present invention is first prepared by combining tetrafluoroethylene and XCF2(CF,)n(OCRCF, 1oOF=cF*
CF3 (in the formula, n and m have the same meanings as above),
Perform emulsion polymerization, then concentrate the obtained latex,
It is stabilized by adding a predetermined surfactant, and can be manufactured by further adding a thickener depending on the case.

In the emulsion copolymerization of the present invention, a so-called seed type method is adopted, and the final particle size is controlled by changing the amount of seeds. Moreover, MV can be controlled by the amount of chain transfer agent, the amount of initiator, reaction temperature, etc. The chain transfer agent can be an organic compound containing hydrogen and present in a substantially liquid state under the reaction conditions, such as methanol, ethanol, nochloromethane, trichloromethane, tetrachloromethane, and the initiator can be a water-soluble peroxide. and persulfates are preferred.

Hereinafter, specific embodiments of the present invention will be illustrated by Examples.

Example 1 First, a seed latex to be used for seed polymerization was synthesized by the method (1) (separately, a coating evaluation of the composition was performed as Comparative Example 1). Thereafter, seed polymerization is performed by the method (2).

(1) In a stainless steel autoclave with an internal volume of 6Q equipped with a temperature control jacket and an anchor stirrer, 2.9Q of deionized water, 400g of l-lichlorotrifluoroethane as a dispersion stabilizer, and ammonium perfluorooctanoate. 9,0 g, 2 mg of reagent grade methanol as a chain transfer agent, and the inside of the tank for deoxidation was flushed with nitrogen gas for 2 hours.
The tank was replaced twice with TFE gas, and then 70 g of perfluor (propyl vinyl ether XPPVE) was charged. The temperature was raised to 65°C while stirring, and TFE gas was injected until the pressure inside the tank reached 9.2 kgf/cm. Then, 100 mg of an aqueous solution containing 4.2 g of ammonium persulfate (A'PS) was added. Start the reaction.During the reaction, keep the pressure in the tank at 9.2 kgf/cm.
The reaction temperature is maintained at 65±1° C. by continuing to feed E gas.

After 4.7 hours, stirring is stopped and the autoclave is cooled to room temperature and vented to atmospheric pressure.

The copolymer concentration in the obtained latex was 20.6% by weight.
, copolymer average particle diameter is 0.18 μm, P in copolymer
PVE content is 3.2% by weight, MV of copolymer is 1.0X
It was lO'boys.

(2) After charging the same amount of deionized water, trichlorotrifluoroethane, and ammonium perfluorooctanoate into the same autoclave as in (1), add the amounts listed in Table 1 (l).
1 mg) of reagent grade methanol and the amount (250 g) of the latex synthesized in (Summer) as listed in Table 1 are charged, and after deoxidation, 70 g of PPVE is charged.

Thereafter, 4.2 g of APS is added and the reaction is carried out in exactly the same manner as in (1). The reaction temperature and reaction pressure are also the same.

The reaction time, latex properties, etc. are as shown in Table 1.

Next, after the reaction, the raw latex obtained in (2) is
Organic phase (trichlorotrifluoroethane and unreacted PP)
VE) is separated and transferred to a separate container, and 30 g of a nonionic surfactant aqueous solution containing 20% by weight of polyoxyethylene octylphenol ether (Nonion H8-208, manufactured by NOF Corporation) is mixed per 1Q of Tex produced. The mixture is kept at 30±1°C and allowed to stand still. After standing still for about 20 hours, the supernatant layer of the mixed liquid separated into a concentrated latex layer and a supernatant layer is removed to obtain a latex with a copolymer concentration of 60% or more. To further stabilize this concentrated latex, water and nonionic H9208 were added, copolymer concentration 50% by weight, nonionic surfactant 5% by weight (based on polymer weight).
Adjust so that

The prepared composition is subjected to coating and coating evaluation as described below. In addition, a portion of the latex immediately after polymerization is evaporated to dryness,
Wash with acetone, dry and powder. MV with this powder
A film with a thickness of about 0.05 mm is prepared by heat pressing at 350° C. for 15 minutes, and the perfluor(propyl vinyl ether) content in the copolymer is determined by infrared spectroscopy.

The crack limit thickness of this example is 26 to 30 μm,
The surface roughness was 0.40 μm. On the other hand, comparative example 1
The critical thickness was small and the surface roughness was rough (large). The effect of particle size is significant.

Examples 2-5 In Example 2, the same seed latex used in Example 1 was used to carry out seed polymerization. In Examples 3 to 5, seed polymerization was performed using part of the raw latex obtained in Example 1 as a seed (therefore, as a result, seed polymerization was performed twice). The amount of methanol and ammonium persulfate used are as listed in Table 1, and conditions other than those listed in Table 1 are as follows.
Everything is the same as in Example 1. As shown in Table 2, all had excellent coating film properties.

Example 6 A reaction was carried out in the same manner as in step (2) of Example 1, except that the latex produced in step (1) of Example 1 was used as a seed and the amount of PPVE charged was 150 g. Reaction time 5.
A latex with a polymer concentration of 19.0% by weight was obtained in 1 hour. Average particle size, MV, and P of the obtained copolymer
The PVE content and physical properties of the coating film are as shown in Table 1 and Table 2, respectively.

Example 7 Example! In the method of step (1), deionized water, trichlorotrifluoroethane, ammonium perfluorooctanoate, and PPVE are used in the same amounts, and as a chain transfer agent, reagent grade dichloromethane 6 is used instead of methanol.
6g was used. The polymerization temperature was 35°C, and the reaction was carried out by adding 50 ml of an aqueous solution containing 4.2 g of ammonium persulfate, followed by 50 ml of an aqueous solution containing 2.3 g of sodium sulfite.
12 was added to start. During the reaction, tetrafluoroethylene was supplied so as to keep the internal pressure at 9.2 kgf/cm', and the polymerization temperature was maintained at 35±1'C.

After 9.6 hours, the reaction was terminated in the same manner as in step (1) of Example 1, and the polymer concentration was 19.0% by weight and the average particle size was 0.
．． A latex of 18 μm was obtained, and the MV of the copolymer was
had 3.3×10′ voids and PPVE content of 2.7%.

Further, 250 g of this latex was used as a seed and charged into a 6Q autoclave with the same amount of deionized water, trichlorotrifluoroethane, ammonium barfluorooctanoate, and PPVE, and then 90 g of dichloromethane was added as a chain transfer agent, and the same amount as above was added. Seed polymerization was carried out by adding amounts of ammonium persulfate and sodium sulfite. Both the reaction pressure and reaction temperature were the same as in the synthesis of the seed latex.

After 14 hours, the polymer concentration of the latex after completion of the reaction was 18.7%, and the average particle size was 0.35 μm. The MV of the copolymer is 2. lX10'bois, PPVE content is 3.
It was 0% by weight.

The raw latex thus obtained was subjected to organic layer separation, concentration, stabilization, and adjustment in the same manner as in Example 1, and the coating and coating film were evaluated. Crack limit thickness is 30-35μm
, the surface roughness was 0.50 μm.

Comparative Examples 1 to 5 Comparative Example 1 is a composite of the seed latex of Example I, and Comparative Examples 2 to 3 are the same as the seed latex composition of Example I, and Comparative Examples 2 to 3 are obtained by not performing seed polymerization but by changing the amount of methanol in the method for producing the seed latex of Example 1. It has been changed.

In Comparative Example 4, the raw latex of Comparative Example 2 was used, and in Comparative Example 5, the raw latex of Comparative Example (2) was used to carry out seed polymerization under the conditions listed in Table 1 according to Example 1.

The physical properties of the coating film are shown in Table 2. In Comparative Example 4, even though the particle size was large, the MV was too high and the surface roughness was large. In Comparative Example 5, the crack limit film thickness and surface roughness are both good, but in this case, the film strength is low, probably due to the MV being too small, making it almost impractical. .

Comparative Example 6 The seed latex used in Example 7 (average particle size 0.18,
czm, MV3.3xlO'poise, PPVE content 2.
7% by weight) was separated, concentrated, stabilized, and adjusted in the same manner as in Example 1, and then painted and evaluated the coating film.

Crack limit thickness is 20-25μm1 Surface roughness is 0.8
It was 0 μm.

In addition, in Examples 2 to 6 and Comparative Examples 1 to 5, the organic layer separation, concentration, stabilization, and adjustment were performed as described in Example 1, and the coating and coating film evaluation were performed under the same conditions.

Specific melt viscosity〉 Using a Koka type flow tester manufactured by Shimadzu Corporation, 2.0 g of copolymer powder was loaded into a cylinder with an inner diameter of 11.3 mm.
After keeping the temperature at 380°C for 5 minutes, it was extruded through an orifice with an inner diameter of 2.1 mm and a length of 8 mm under a piston load of 7 kg, and at an extrusion speed of 87 minutes (87 minutes).
The value divided by 50 was determined as the specific melt viscosity (poise).

Average particle size〉 The latex immediately after completion of polymerization before concentration was photographed using a transmission electron microscope, and the directional length diameter of approximately 100 to 400 particles was measured. Fluorovinyl ether content> For perfluorinated (propyl vinyl ether) in the copolymer, the above film was analyzed by infrared spectroscopy to determine the ratio of the absorbance at 995 cm to the absorbance at 2360 cm, multiplied by 0.95. (Refer to JP-A-56-92943).

<Painting test> The prepared aqueous dispersion composition was applied to a width of 5 cm and a length of 40 cm.
, Spray coating on an aluminum laminated board (previously surface cleaned with acetone and deoiled) with a thickness of 1 mm. The nozzle diameter of the spray gun is 08~1゜1 mm, and the air pressure is about 3 kg/cm. At this time, the composition is sprayed onto each part of the aluminum plate so that the thickness after firing is 10~50 μm. The amount of spraying is changed appropriately.After spraying, preliminary drying is performed for 10 minutes in an infrared drying oven (approximately 100°C), followed by baking in an electric furnace controlled at 400°C for 20 minutes. Immediately after firing, remove from the furnace and allow to cool to room temperature.

<Evaluation of paint film> Measure the thickness of the paint film using a surface film thickness meter. Mud cracks are observed as the film thickness increases, but the maximum film thickness without mud cracks is defined as the crack limit thickness.

Surface roughness was measured using a universal surface profile measuring instrument (manufactured by Koita Research Institute Co., Ltd. 5).
E-3C). Since the surface roughness varies depending on the film thickness, the comparison will be made using a film with a film thickness of about 20 μm.

Procedural amendment (,e) May 24, 1986

Claims (1)

[Claims] 1. General formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, X is H or F, n is an integer from 0 to 7, and m is from 0 to
It is an integer of 3. ) A copolymer of fluorovinyl ether and tetrafluoroethylene represented by
10^4 to 10.0 x 10^4 poise, average particle size 0.
An aqueous copolymer resin dispersion composition containing colloidal copolymer particles of 3 to 1 μm as a main component and stabilized with an anionic or nonionic surfactant. 2. Fluorovinyl ether is C_3F_7OCF=C
The composition according to claim 1, which is F_2. 3. Average particle size is larger than 0.5 μm and specific melt viscosity is 0.
．． The composition according to claim 1, which has a molecular weight of 4 to 5.0 x 10^4 poise. 4. The composition according to claim 1, having an average particle size of 0.6 to 0.8 μm. 5. The composition according to claim 1 for non-adhesive coating.