JP3165114B2 - Polytetrafluoroethylene resin / silicone resin mixed paint and its coating film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tetrafluoroethylene resin-silicone resin-mixed coating material in which a tetrafluoroethylene resin (hereinafter referred to as "PTFE") powder is dispersed in a silicone binder, and a coating film thereof. The coating film is obtained by applying a coating material to an object to be coated, drying and curing the organic solvent after volatilization.

A coating film formed by using the coating material of the present invention has water repellency, so that it can be used by applying it to many articles that require water repellency, snow-resistance and ice-resistance. . Further, it can be used as a coating material and a repair material for articles requiring insulation to prevent water from entering. Examples of articles that require water repellency include rain gear such as umbrellas, and articles that require low snow and ice resistance, such as roofs, bridges, wireless communication antennas, and heat exchangers of buildings in heavy snow areas. Articles requiring insulation properties include cables and electronic circuit boards. Further, since the paint of the present invention has a property of hardly adhering to an object, it can be used also as an anti-paste paint.

[0003]

2. Description of the Related Art Conventional fluororesin paints are used in the fields of construction, automobiles and the like as paints having excellent weather resistance and stain resistance. These are one-component paints utilizing copolymers of fluoroolefins and various hydrocarbons.
None of them have high water repellency, and the contact angle of water of the formed coating film is about 80 °.

On the other hand, in a two-component paint mainly composed of ethylene tetrafluoride as a main component and mixed with a fluororesin binder such as vinylidene fluoride resin, the contact angle of water of the formed coating film is low. High water repellency of about 150 ° has been realized and is being put to practical use. However, in the case of a two-component paint in which such a fluororesin powder is mixed with a fluororesin binder, it is necessary to contain a large amount of expensive fluororesin powder in order to achieve a contact angle of 150 °. Also,
Although the initial water repellency is excellent, there is a problem in that the water repellency, the poor snow accretion, and the poor ice accretion are reduced by long-term water immersion.

FIG. 8 is a schematic cross-sectional view of a coating film formed using a conventional fluororesin binder and fluororesin powder. Binder 11 containing fluororesin powder 10 on substrate 9
Is applied, and the fluororesin powder 10
Has a structure with exposed head. In such a coating film, a decrease in water repellency due to long-term water immersion is observed. It is considered that the cause is that water gradually penetrates into the gap 12 formed between the fluororesin powder 10 and the binder 11, and then water does not escape from the gap, which causes a decrease in water repellency.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a coating film and a coating film of a mixed resin of a tetrafluoroethylene resin and a silicone resin, which solve the above-mentioned problems of the prior art. That is, the present invention provides a paint and a coating film which have high water repellency even without containing a large amount of fluororesin powder, have excellent snow-repelling properties, excellent ice-repelling properties, and which do not decrease in water repellency even by long-term water immersion. The purpose is to do so.

The inventors of the present invention have found that the deterioration of the water repellency with time is caused by a gap formed between the fluororesin powder and the binder due to a large surface free energy difference and poor wettability. That is, the inventors have found that the binder and the fluororesin powder on the surface of the coating film are caused by the deterioration of the binder and the fluororesin powder due to the intrusion and remaining of water into the gaps, and the present invention has been completed from the viewpoint of eliminating such causes.

[0008]

In order to solve the above-mentioned problems, the coating film of the present invention has a 1800 cm ^-1 carbonyl group present as a terminal group in an infrared absorption spectrum. A ratio of the peak intensity in the vicinity to the peak intensity in the vicinity of 500 cm ⁻¹ due to the C—F bond is 0.05 or less, a tetrafluoroethylene resin powder, a silicone resin binder, an alcohol, an aromatic, and an aliphatic. Or an organic solvent obtained by mixing them.

Also, the tetrafluoroethylene resin silicone of the present invention
Corn resin mixed coating film, in order to solve the above problems,
In the infrared absorption spectrum, the
1800cm which rubonyl group shows^-1Near peak intensity
500cm by CF bond ^-1For nearby peak intensities
Tetrafluoroethylene resin powder having a ratio of less than 0.05
And a silicone resin binder.
You.

The water repellency of ethylene tetrafluoride resin (hereinafter referred to as PTEF) powder can be increased by promoting the fluorination of terminal groups. The degree of fluorination of the terminal group of the PTFE powder is represented by the formula 1, as shown in Formula 1, in the infrared absorption spectrum of the PTFE powder, the peak intensity near 1800 cm ⁻¹ indicated by the carbonyl group present as the terminal group,
It can be evaluated by the ratio to the peak intensity around 500 cm ^-1 due to the CF bond.

Formula 1: Degree of fluorination of terminal group of PTFE powder = (1
800 cm ^-1 peak intensity in the vicinity of) / (500 cm ^-1 peak intensity in the vicinity) = peak ratio

The use of PTFE having partially or completely fluorinated terminal groups makes it possible to reduce the amount of PTFE powder required to obtain a contact angle of 150 °. Reducing the amount of expensive PTFE powder used is also effective in reducing paint costs.

Further, the present invention provides a silicone resin having a smaller surface free energy than a conventional fluororesin binder,
Polyorganosiloxane such as silicone rubber or a fluorosilicone resin in which a part thereof is fluorinated,
One type of polyfluorinated organosiloxane such as fluorosilicone rubber or a mixed resin containing two or more types is used as the silicone resin binder. Since the difference in surface free energy between the fluororesin powder and the binder is small, the coatability is good and the occurrence of gaps between the fluororesin powder and the binder can be reduced. On the other hand, no decrease in water repellency is observed.

As described above, the coating film formed by using the coating material of the present invention can suppress the generation of the gap which causes the deterioration of the water repellency with time, and the PTFE powder and the binder are less deteriorated. Can also prevent a decrease in water repellency.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the infrared absorption spectrum of the tetrafluoroethylene resin-silicone resin mixed paint of the present invention, 18
The peak intensity around 00 cm ^{-1 is} 50 due to the CF bond.
A tetrafluoroethylene resin powder having a ratio to a peak intensity near 0 cm ^-1 of 0.05 or less, a silicone resin binder, and an alcohol-based, aromatic-based, or aliphatic-based organic solvent or an organic solvent obtained by mixing them; It is characterized by including.

[0015] In the infrared absorption spectrum, the tetrafluoroethylene resin-silicone resin mixed coating film of the present invention has a carbonyl group present as a terminal group.
The peak intensity near 0 cm ^{-1 is} 500 due to the CF bond.
It is characterized by including a tetrafluoroethylene resin powder having a ratio to a peak intensity in the vicinity of cm ^-1 of 0.05 or less, and a silicone resin binder.

The chemical structure of PTFE is represented by the following chemical formula 1.

Embedded image [A1] —C ₂ F ₄ —C ₂ F ₄ —... —C ₂ F ₄ — [A2]

[0017] located at the ends of the long chain of tetrafluoroethylene [A1], [A2] is a terminal group, F, carbon atoms such as CF ₃ - ideal that occupied by fluorine-based molecules or groups In some cases, however, the hydrophilic group such as a carbonyl group may be occupied, and in such a case, the water repellency decreases. The fluorination of the terminal group is performed, for example, by vaporization and recrystallization in a fluorine atmosphere. In this process, the carbonyl group at the terminal group is replaced by fluorine, CF ₃ or the like. At the same time, the molecular weight of PTFE is reduced and the pulverization proceeds.

Further, effective configurations in the present invention are listed below. (1) The PTFE powder used as the water-repellent powder is PT
The molecular weight of FE is reduced to a molecular weight of 500 to 10000, and in the process, the terminal group is partially or completely fluorinated by contact reaction with a fluorinating agent.
PTFE powder of 1-2 μm is preferred. The degree of fluorination of the terminal group of the low-molecular-weight PTFE may be 0.05 or less in the infrared absorption spectrum, and more preferably 0.02 or less, in the peak ratio of Formula 1.
Low molecular weight PT having terminal groups partially or completely fluorinated
Since EF is used, if the content of PTFE is the same, the higher the degree of fluorination, the higher the water repellency.

(2) The binder is a polyorganosiloxane such as silicone resin or silicone rubber, or a fluorosilicone resin in which a part thereof is fluorinated;
Polyfluorinated organosiloxanes such as fluorosilicone rubber are suitable, and may be used alone or as a mixture thereof.

The silicone resin binder of the present invention and PTF
FIG. 9 shows a schematic diagram of a cross-sectional structure of a coating film formed using E powder. A silicone resin binder 14 containing PTFE powder 13 is applied on the substrate 9, and a PT
The FE powder 10 has a structure in which the head is exposed. However, since the difference in surface free energy between the PTFE powder and the binder is small, the wettability is good, and the generation of the gap between the PTFE powder and the binder can be reduced. Absent.

The surface free energy difference between the PTFE powder and the binder can be evaluated by the contact angle. The contact angle between the PTFE powder and water 115 is ^○, the contact angle with conventional polyvinylidene fluoride binder and water 90 ^○ Nevertheless compared, PTEF powder contact angle 110 ^○ between the silicone resin binder and water Is smaller than that of silicone resin binder,
It can be seen that the wettability with FE powder is good. When a silicone resin binder is used, the amount of PTFE powder required for obtaining high water repellency is smaller than that of a conventional fluororesin binder.

As the organic solvent, an alcohol-based solvent such as ethyl alcohol, n-heptane, and toluene, an aromatic-based solvent, an aliphatic-based solvent, or a mixed solvent thereof can be used.

Hereinafter, the present invention will be described specifically with reference to examples.

[0024]

EXAMPLES (Sample 1) As solid content, average molecular weight 500
0, PTFE powder having a high degree of fluorination up to the end group having a particle size of 0.88 μm (peak ratio = 0.01) is 45% by volume fraction, and polyorganosiloxane resin is 5% by volume fraction.
A two-component system of 5% was prepared, and this was mixed with n-heptane at a weight ratio of 35% using a ball mill to prepare a paint. This tetrafluoroethylene resin / silicone resin mixed paint was spray-coated on a slide glass to form a coating film, and a sample for confirming the effects of the present invention was produced.

(Sample 2) For comparison, PTFE powder having a not so high degree of fluorination up to the terminal group (peak ratio =
0.05) was used to prepare a coating material having the same mixed composition as that of Sample 1. The paint was spray-coated on a slide glass to form a coating film, and a sample was prepared. The type of the PTFE powder is different from that of the sample 1. Samples 1 and 2 fall within the scope of the present invention.

(Comparative Example 1) As a comparative example, a two-component system was prepared in which the same PTFE powder as that of Sample 1 was used in a volume fraction of 45%, and a vinylidene fluoride resin was used as a binder in a volume fraction of 55%. -A coating material was prepared by mixing at 35% by weight with respect to heptane using a ball mill. A slide glass was spray-coated with the mixed paint of the tetrafluoroethylene resin and the silicone resin to form a coating film, thereby preparing a sample. The type of the binder resin is different from that of the sample 1.

(Comparative Example 2) As a comparative example, a two-component system was prepared in which the same PTFE resin powder as in Sample 1 was used in a volume fraction of 80%, and a vinylidene fluoride resin was used as a binder in a volume fraction of 20%. The mixture was mixed at 35% by weight with respect to n-heptane using a ball mill to prepare a coating material. A slide glass was spray-coated with the mixed paint of the tetrafluoroethylene resin and the silicone resin to form a coating film, thereby preparing a sample. The type of the binder resin is different from that of the sample 1, and the content of expensive PTFE is large because the composition ratio is changed.

Table 1 summarizes the main components of the examples and comparative examples.

[Table 1] In the table, the degree of fluorination of the terminal group of the PTFE powder is obtained from the infrared absorption spectrum of the PTFE powder according to Equation 1.

FIG. 1A is a diagram showing an infrared absorption spectrum of ethylene tetrafluoride. The horizontal axis is the wave number of infrared rays, and the vertical axis is the intensity of infrared absorption. The values in the figure are the peak ratios obtained by calculating the degree of the fluorination of the terminal groups by Equation 1, and the figures show different peak ratios. The measurement results of three samples are shown. FIG. 1B is an enlarged view around a wave number of 1800 cm ⁻¹ . As the fluorination of the terminal group of the PTFE powder progresses, the carbonyl group existing as the terminal group is substituted and 18
This shows how the peak value near 00 cm ^-1 becomes smaller. The degree of fluorination of the PTFE powder of the sample 1 of the present example and the PTFE powders of the comparative examples 1 and 2 is 0.01 at the peak ratio, and the peak ratio of the sample 2 is 0.05 at the sample 2. The graph of ND in the figure is a measurement example when fluorination further progressed and reached the measurement limit.

FIG. 2 is a schematic diagram in which water droplets are dropped on a coating film. 1 is a substrate, 2 is a coating film, and 3 is a water droplet. Also,
The water repellency was comparatively evaluated from the measured value of the contact angle θ of the water droplet 3 on the coating film 2.

With respect to the coating properties of the examples and the comparative examples, the initial contact angle, the contact angle after 200 days of water immersion, and the shearing icing power were respectively defined as the initial water repellency, the water repellency after 200 days of immersion in water, and the initial hard-to-ice property. And shown in Table 2.

[Table 2]

First, the water repellency of the samples of this embodiment and the comparative example will be described below. The contact angle θ of water is best known as a measure of water repellency, and the larger the angle, the higher the water repellency. The water repellency was evaluated using a contact angle meter manufactured by Kyowa Interface Science Co., Ltd. Approximately 4 μl (4 × 10 ⁻⁹ m ³ ) of water droplets were dropped on the surfaces of the paints of this example and the comparative example, and the contact angle θ of water was measured. The measurement was performed at a room temperature of 23 ° C., and an average value of five measurement points was used. In sample 1, the contact angle of water was 152 °. The contact angle of Sample 2 was 124 °, that of Comparative Example 1 was 128 °, and that of Comparative Example 2 was 152 °. It can be said that Sample 1 and Comparative Example 2 have high water repellency.

FIG. 3 is a diagram showing the relationship between the content of PTFE powder in the coating film and the water repellency. The PTFE resin powder having a very high degree of fluorination up to the terminal group (sample 1) of the present example (shown by Δ, peak ratio 0.01) was used for the water-repellent powder, and the sample 2 of the terminal group The amount (vol.) Of the PTFE powder when a PTFE powder having a degree of fluorination up to
%) And the contact angle (deg) with water.

As can be seen from the drawing, sample 1 is the same as sample 2 at the same content.
It can be seen that higher water repellency can be obtained with a small amount by using a PTFE powder having a large contact angle and a high degree of fluorination up to the terminal group as the water repellent powder.

FIG. 4 shows the relationship between the amount of PTFE powder almost completely fluorinated up to the terminal group and the contact angle. For the sample of the coating film formed by applying the paint when the silicone resin as the sample 1 of the present example was used as the binder and for the comparison when the vinylidene fluoride resin was used as the binder, the PTFE in the coating film was measured. The relationship between the amount of powder (vol%) and the contact angle (deg) with water is shown. From this figure, it can be seen that when the same amount of PTFE powder is used, water repellency higher than that of a coating film formed using vinylidene fluoride resin is obtained by using a silicone resin as a binder, and a large amount of fluororesin powder can be fluorinated. It can be seen that a film equivalent to the water repellency of a coating film formed using a fluororesin paint mixed with vinylidene resin can be obtained. For example, to obtain a contact angle of 155 °, a coating film formed using vinylidene fluoride
While 0% or more of PTFE powder is required, in this example, 50% or more is sufficient, which indicates that the amount of expensive PTFE powder is suppressed and the cost of paint is reduced.

FIG. 5 shows the relationship between the days of water immersion and the contact angles of Samples 1 and 2 of this example and Comparative Examples 1 and 2. Samples 1 and 2 of the present example have a smaller decrease in water repellency with time than the samples of Comparative Examples 1 and 2 evaluated by the same method, and sample 1 maintains a high contact angle and has a long term It turns out that it has durability. Sample 2 has a lower initial contact angle than Comparative Example 1, but shows little decrease with time.

Next, in order to compare the ease with which ice adheres,
Ice was attached on the coating film at -15 ° C, and the icing shear force was measured using an icing force tester. FIG. 6 shows the configuration of the icing power tester. The icing power tester includes an ice 5 surrounded by a cylindrical Teflon ring 4 having a diameter of 32 mm adhered on the coating film 2.
Is pulled at a constant speed in a direction 7 parallel to the coating film using a stainless steel wire 6, and a load change is read by a load cell 8 until the ice is detached. The maximum load at which the ice 5 did not detach was defined as the icing shear force.

The icing shearing force was measured for Samples 1 and 2 in which a coating film was formed by spray coating the mixed coating of the tetrafluoroethylene resin and silicone resin of this example, and Comparative Examples 1 and 2 described above. The measured value was an average value of five points. The icing shear force of the coating film of Sample 1 was 112 gf / cm ² , and that of Sample 2 was 205 gf / cm ² .
gf / cm ² , whereas Comparative Example 1 had 552 g
f / cm ² , and that of Comparative Example 2 was 381 gf / cm ² . These results are shown in FIG. The icing shear force of the present example is smaller than that of the comparative example, and a remarkable improvement in characteristics is obtained as compared with a coating film using PTFE using a polyvinylidene fluoride resin as a binder.

In this embodiment, the case where a silicone resin is used for the binder has been described. However, even if other polyorganosiloxane such as silicone rubber or polyfluorinated organosiloxane such as fluorosilicone resin or fluorosilicone rubber is used, the binder can be used. Similar results can be expected because the surface free energy difference is small. In this example, the peak ratio of the PTFE powder was 0.01 to 0.0.
Although the case of 5 has been described, the peak ratio may be 0.05 or less, and the present invention is not limited to the above embodiments.

[0040]

As described above, according to the present invention, a coating film is formed by using a paint obtained by adding a tetrafluoroethylene resin powder having a terminal group partially or completely fluorinated to a silicone resin binder. Therefore, the amount of PTFE resin powder required to obtain high water repellency is smaller than in the conventional case. Further, since the difference in surface free energy between the fluororesin powder and the binder is small, the wettability is good, and the occurrence of gaps between the PTFE resin powder and the binder can be reduced, so that water can be prevented from entering the coating film. . For this reason,
Since there is little deterioration of the material, high water repellency is maintained for a long time. That is, even when the present invention is used outdoors where it is exposed to water, the water repellency does not decrease over a long period of time. In addition, the present invention has a small icing shearing force and is excellent in icing resistance.

[Brief description of the drawings]

FIGS. 1A and 1B show infrared absorption spectra of ethylene tetrafluoride. FIG. 1A shows a spectrum at a wave number of 500 to 4000 cm ⁻¹ , and FIG. 1B shows an enlarged view around a wave number of 1800 cm ⁻¹ . It is.

FIG. 2 is a schematic diagram in which water droplets are dropped on a coating film.

FIG. 3 is a diagram showing the relationship between the content of PTFE powder in a coating film and water repellency.

FIG. 4 is a diagram showing the relationship between the amount of PTFE powder added and the contact angle when a binder of the present invention and a conventional binder are used.

FIG. 5 is a diagram showing the relationship between the number of days of water immersion and the contact angle of Samples 1 and 2 of Examples and Comparative Examples 1 and 2.

FIG. 6 is a diagram showing a configuration of an icing power tester.

FIG. 7 is a view showing the shearing icing power of Samples 1 and 2 of Examples and Comparative Examples 1 and 2.

FIG. 8 is a schematic sectional view of a conventional coating film.

FIG. 9 is a schematic sectional view of a coating film of the present invention.

[Description of Signs] 1 substrate 2 coating film 3 water drop 4 Teflon ring 5 ice 6 stainless wire 7 direction parallel to coating film 8 load cell 9 substrate 10 fluororesin powder 11 fluororesin binder 12 gap 13 PTFE powder 14 silicone resin binder

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Tsukamoto 1-3-1 Gotenyama, Musashino City, Tokyo Inside NTT Advanced Technology Corporation (72) Inventor Hiroki Yonezawa Nishishinjuku, Shinjuku-ku, Tokyo Within 3-19-2 Nippon Telegraph and Telephone Corporation (72) Inventor Kenichi Takai Within 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Goro Yamauchi Shinjuku-ku, Tokyo Examiner, Nippon Telegraph and Telephone Corporation, Nishi Shinjuku 3-chome Masakatsu Kondo (56) References JP-A-8-3479 (JP, A) JP-A-6-122838 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C09D 127/18 C09D 183/04 CA (STN) CAOLD (STN) REGISTRY (STN)

Claims (4)

(57) [Claims] 1. In an infrared absorption spectrum, a ratio of a peak intensity near 1800 cm ^{−1 of} a carbonyl group existing as a terminal group to a peak intensity near 500 cm ⁻¹ due to CF bond is 0.05 or less. Ethyl tetrafluoride
Ren resin powder (however,
Excluding) , silicone resin binder, alcohol-based,
A mixed paint of an ethylene tetrafluoride resin and a silicone resin, comprising an aromatic solvent, an aliphatic solvent or an organic solvent obtained by mixing them. 2. The ethylene tetrafluoride resin according to claim 1, wherein the silicone resin binder is one of polyorganosiloxane or polyfluorinated organosiloxane, or a mixed resin containing two or more kinds. Silicone resin mixed paint. 3. In an infrared absorption spectrum, a ratio of a peak intensity near 1800 cm ^{−1 of} a carbonyl group existing as a terminal group to a peak intensity near 500 cm ⁻¹ due to CF bond is 0.05 or less. Ethyl tetrafluoride
Ren resin powder (however,
Excluding) and a silicone resin binder. 4. The ethylene tetrafluoride resin according to claim 3, wherein the silicone resin binder is one of polyorganosiloxane or polyfluorinated organosiloxane, or a mixed resin containing two or more kinds. Silicone resin mixed coating film.