JP3192071B2 - Method for producing water-repellent composite particles and water-repellent material using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a water-repellent composite particle and a water-repellent material using the same to form a water-repellent layer on a substrate surface.

[0002]

PRIOR ART Fluorine resin has excellent water repellency and waterproof,
It has been put to practical use in many fields for antifouling and the like. However, the most water-repellent PT among fluororesins
Even FE does not have a water-repellent effect enough to completely prevent water droplets from adhering to the surface, leaving water droplets on the surface and contaminating the surface with dust and the like adhering to the surface, thereby significantly reducing the water-repellent effect. There is such a problem.

[0003] In addition, since the higher the water repellency of the fluororesin, the lower the adhesiveness to other materials, it is very difficult to coat the surface of the base material. The durability is low. Conventionally PT
A method has been used in which one surface of a sheet such as FE is treated with metallic sodium to activate the surface and increase the adhesive strength, or a method in which the PTFE sheet surface is roughened by glow discharge or the like to increase the adhesive strength by an anchor effect. . However, in such a method, the processing is complicated, and P
It is difficult to handle a TFE sheet having a complicated shape.

[0004]

[Specific means for solving the problem]
In order to solve the problems of the prior art, low molecular weight P
Water-repellent composite particles in which TFE is coated on particles having higher mechanical strength than the low-molecular-weight PTFE.
On a primary particle having a higher mechanical strength than FE, a method for producing water-repellent composite particles characterized by being crushed and pulverized after coating with low-molecular-weight PTFE, and an adhesive layer on the surface of the base material, The low-molecular-weight PTFE is
A water-repellent material characterized by having a roughened surface made of water-repellent composite particles coated on particles having a higher mechanical strength than E has been previously proposed (JP-A-7-25106).
No. 0). A method for producing water-repellent composite particles in which PTFE is coated on particles having higher mechanical strength than PTFE is disclosed in JP-A-53-147541 and JP-A-4-358087.
And JP-A-7-90691. However, in all of these methods, the coating is performed by an electrostatic effect or an anchor effect due to unevenness of the particle surface, by mechanically mixing the particles with each other,
When these are used as a water-repellent material, the adhesion between the particles and the coated PTFE is important. In general, the adhesiveness of a coating to a substrate is better as the thickness of the coating is thinner, and it is difficult to control the thickness in the method for producing water-repellent particles as described above, and it is difficult to obtain water-repellent particles having good adhesion. .

[0005] The present inventors have made intensive studies in view of the above problems, and have reached the present invention. That is, the present invention provides a method for producing water-repellent composite particles, which comprises vapor-depositing low molecular weight PTFE capable of being vapor-deposited on primary particles having higher mechanical strength than low molecular weight PTFE, and forming an adhesive layer on the substrate surface. The present invention provides a water-repellent material having a rough surface formed of the water-repellent composite particles.

[0006] The surface of the substrate provided with the water-repellent composite particles according to the present invention has a small contact area between water droplets and the surface due to the effect of surface roughening. As a result, the adhesion of water droplets can be almost completely prevented. In addition, since particles having mechanical strength larger than that of PTFE are compounded, durability against external forces such as friction is significantly improved. Furthermore, since the particles are coated by a vapor deposition method that can easily obtain a relatively uniform thin film,
Water-repellent particles having high adhesiveness can be obtained, and there is no fear that the coating is peeled off by mixing, stirring, or the like when producing the water-repellent material.

In order to exhibit stronger water repellency or to impart transparency to the water repellent material, it is necessary to reduce the particle size of the water repellent particles to 1 μm or less. Is soft, and it is difficult to obtain particles of 1 μm or less by a general pulverization method because, for example, fusion occurs between particles. According to the present invention, 1
It is possible to easily obtain water-repellent fine particles of 1 μm or less by subjecting the fine particles of μm or less to the compounding in the present invention.

When the water-repellent composite particles are used, the particles float on the surface of the composition before the adhesive layer is completely cured due to the low surface energy of the water-repellent composite particles. By adding the particles, the particles penetrate into the adhesive layer, and sufficient adhesiveness can be obtained. Where PTFE
In the case of a single particle, since the particle has no strength, a rough surface cannot be maintained and the bite is insufficient, so that adhesion is not obtained and durability is also insufficient.

The low molecular weight PTF used in the present invention
As E, the average molecular weight obtained by the manufacturing method proposed by the present applicant (Japanese Patent Publication No. 1-49404) is 500.
の も の 15000, preferably 500-5000. Those having an average molecular weight of more than 15,000 are not preferred because the vapor pressure is low and it is difficult to deposit on particles, which is a feature of the present invention.

In the present invention, the high-strength water-repellent composite particles are
Particles used for forming are stronger than PTFE
Anything with a high degree may be used. For example, SiO_Two, Al
_TwoO _ThreeAnd other metallic materials such as Fe and Ni
Materials such as fillers, epoxy resins, and polycarbonate
Pigments, pigments and carbon materials for coating materials, CaF_Two
And the like. However, surface irregularities are large.
Threshold particles and porous particles have a stronger anchor effect
This is preferable because it can be expected and the adhesion becomes stronger. These grains
The particle size of the particles is preferably 0.01 μm or more and 1 mm or less.
In the case of a particle size of 1 mm or more, the composite particles are coated on the surface of the substrate.
When coated, water becomes spherical due to the water repellent effect
Water droplets between the particles make it difficult to fall from the surface
It is not preferable because it may occur.

In the present invention, low molecular weight PTFE is added to the particles.
There are various methods for vapor deposition, but the temperature and vapor density distribution of the particles, which are important factors in obtaining a uniform vapor-deposited film, can be relatively easily and uniformly controlled using a fluidized bed apparatus with a low molecular weight. A method of blowing PTFE vapor together with a carrier gas such as nitrogen is preferable.

The fluidized bed apparatus used in the present invention comprises:
A device such as that shown in FIG.
A lower heater 3 for vaporizing E, a tube wall heater 2 for controlling the temperature of the fluidized bed, a circulating pump 5 for changing the linear velocity of the fluidized bed, and a deposition film by controlling the deposition time. The thickness and the film formation state can be controlled. The lower heater temperature is related to the vaporization rate of the low molecular weight PTFE, and is preferably set in a temperature range of 100 ° C to 500 ° C. If the temperature is lower than this, the vapor pressure of the low molecular weight PTFE is too low, so that the vapor deposition is difficult,
On the other hand, when the temperature is high, decomposition of low molecular weight PTFE and the like occur, which is not preferable. Tube wall heater temperature is low molecular weight P
This is related to the film formation state of TFE, and is preferably set in a temperature range of 50 ° C. to 350 ° C. If the temperature is lower than this, low molecular weight PTFE will precipitate and powder on the tube wall intensely.
It is not preferable because E melts. Since the optimum set values of the lower heater temperature and the tube wall heater temperature depend on the molecular weight of the low molecular weight PTFE, the low molecular weight PTFE used
What is necessary is just to select suitably from said viewpoint according to the molecular weight of E.

The flow rate of the circulating pump is related to the flow state of the fluidized bed, and may be arbitrarily selected. However, for uniform deposition, the flow rate at which a stable flow state is obtained, that is, the linear velocity of the fluidized bed, Is preferably higher than the flow start speed and at a linear velocity that does not cause the transition to the high-speed fluidized bed.
The optimum set value of the circulating pump flow rate depends on the type and diameter of the particles used in the fluidized bed, and may be appropriately selected from the above viewpoints according to the particles used.

The material and shape of the substrate to be coated with the water-repellent composite particles of the present invention are not particularly limited, and any material that can be generally coated can be used. Further, the adhesive layer may be an epoxy resin, a urethane resin or the like used for general bonding or painting. The thickness of the adhesive layer is preferably not less than the radius of the composite particles to be used, and if it is less than that, sufficient adhesive strength cannot be obtained.

The water-repellent material obtained by forming a water-repellent layer on a substrate using the water-repellent composite particles obtained as described above exhibits remarkably higher water repellency than conventional ones, and almost completely prevents the attachment of water droplets. Can be prevented. Moreover, the adhesiveness to the substrate is excellent.

[0016]

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

Examples 1 to 16 and Comparative Examples 1 to 3 The water-repellent composite particles shown in Examples 1 to 7 in Table 1
It was prepared as follows. Fluid bed deposition apparatus 1 (φ25 × 500, SU
S), 5 g of low molecular weight PTFE6 having a molecular weight of 3000
And 50 g of particles 7 (hereinafter, referred to as a composite material) having higher mechanical strength than low molecular weight PTFE, and the tube wall heater 2 was set to 200 ° C. and the lower heater 3 was set to 350 ° C. and heated. Vapor deposition was performed for 30 minutes at a linear speed at which the composite material 7 was fluidized by the circulation pump 5 to obtain water-repellent composite particles. Among the composite materials, fine materials and low-molecular-weight PTFE precipitated in a powder form without being formed into a film are produced by cyclone 4
Collected at.

Next, a one-component epoxy resin (XNR3501 manufactured by Ciba-Geigy) is coated on a substrate (a glass substrate in Example 1, an Al substrate in Examples 2 to 5, and a Ni substrate in Examples 6 and 7). An excess amount of the water-repellent composite particles obtained by the above-mentioned method was uniformly sprayed so that the surface was completely covered. Before the resin layer is cured, a glass plate is overlaid on the surface, pressure is applied thereto, and the resin layer is completely cured at 150 ° C., and excess water-repellent particles on the surface are removed. Film). The water repellency of this water repellent material was evaluated by measuring a contact angle with respect to a water drop having a diameter of 2 mm and a falling angle representing the ease of dropping the water drop, and the durability was evaluated by a peel test using an adhesive tape.

In Comparative Example 1 in Table 1, a water-repellent material was formed in the same manner as in Examples 1 to 7 using only pure low-molecular-weight PTFE particles having a particle size of 1 μm and evaluated. Example 1
7 and Comparative Example 1, the contact angle was 1 for all materials.
Although it is as large as 60 °, there is a difference between the falling angle and the contact angle after the peeling test. It can be seen that Comparative Example 1 has a large falling angle and is easily deteriorated by the peeling test. That is, it is understood that Examples 1 to 7 are more excellent in water repellency and durability.

[0020]

[Table 1]

Examples 8 to 15 shown in Table 2 were carried out as follows. First, water-repellent composite particles were prepared in the same manner as in Examples 1 to 7. The water-repellent composite particles are mixed with an organic solvent (butyl acetate) at a ratio of 1: 1. Add one-part epoxy resin (Ciba Geigy: XNR35)
01) was added and mixed well to obtain a water-repellent resin.

Next, the prepared water-repellent resin is applied on a glass substrate, and the coated plate is dried at 150 ° C. to completely cure the resin layer. Next, the contact angle of the water-repellent material (coating film) thus obtained with respect to a water droplet having a diameter of 2 mm was measured.
The mechanical durability test of the surface of the water-repellent material was carried out by using a mechanical durability test apparatus as shown in FIG. 9 with a stirrer 11 at a load of about 500 g on the surface of the material.
After rotating 10,000 times, the contact angle with respect to a water drop having a diameter of 2 mm was measured again and compared with the contact angle before the test.

In Table 2, Comparative Example 2 shows a low molecular weight PTF
Only E, Comparative Example 3 evaluated a simple mixture of low molecular weight PTFE and zeolite as a water-repellent material (coating film) in the same manner as in Examples 8 to 15, respectively.

When the respective examples and comparative examples in Table 2 are compared,
It is apparent that the water-repellent composite particles of the present invention have superior mechanical durability. In Table 2, Example 16 is an evaluation of the test piece obtained in Example 1 by the same mechanical durability test as in Examples 8 to 15.

[0025]

[Table 2]

[0026]

According to the present invention, as described above, by using the water-repellent composite particles obtained by coating low-molecular-weight PTFE on particles having higher mechanical strength than the low-molecular-weight PTFE, water repellency and durability can be easily achieved. A water-repellent material having excellent properties can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing an example of a vapor deposition apparatus used for producing the water-repellent composite particles of the present invention.

FIG. 2 is a schematic view of a mechanical strength test device using a toothbrush.

[Explanation of symbols]

 1. Fluidized bed deposition equipment 2. Tube wall heater ３． Lower heater 4. Cyclone 5. Circulation pump 6. 6. Low molecular weight PTFE Composite material 8. Substrate 9. Brush 10. Platform scale 11. Stirrer

──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Keizo Kojima 5253 Oki Obe, Oji, Ube City, Yamaguchi Prefecture Inside the Chemical Research Laboratory (72) Inventor Yasushi Yasushi 5253 Oki Ube, Oji Ube City, Yamaguchi Prefecture, Central Glass (56) References JP-A-7-251060 (JP, A) JP-A-5-171410 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 14 / 00-14/58 C08J 3/00-3/28

Claims (2)

(57) [Claims] 1. An average particle size of 0.01 μm having a higher mechanical strength than a low molecular weight PTFE having a molecular weight of 500 to 15,000.
A method for producing water-repellent composite particles, comprising, when depositing the low-molecular-weight PTFE on primary particles of m to 1 mm, causing the primary particles to be in a fluid state and depositing the low-molecular-weight PTFE. 2. A water-repellent material, wherein a rough surface made of the water-repellent composite particles produced by the method according to claim 1 is formed on the surface of a base material via an adhesive layer.