JPH0625604A - Coating composition for weatherstrip - Google Patents

Abstract

PURPOSE:To obtain a coating compsn. which can form a dull coating film excellent in abrasion resistance on the surface of a weatherstrip substrate. CONSTITUTION:This compsn. comprises an organopolysiloxane having at least two silanol groups in the molecule, an organohydrogenpolysiloxane having at least three hydrogen atoms directly bonded to silicon atoms in the molecule, an organotin compd., and a spherical powder having a mean particle diameter of 50mum or lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weatherstrip coating composition, and more particularly to a weatherstrip coating composition useful for providing a dull and non-sticky coating.

[0002]

2. Description of the Related Art Conventionally, there is a method of coating a curable silicone rubber composition for the purpose of improving durability and weather resistance of cloth, synthetic leather, synthetic rubber and the like. For example, in the field of automobiles, sponge rubbers such as EPDM, CR, SBR and solid rubbers are generally used as synthetic rubber weather strips which are sealing materials for automobile window frames and door opening / closing portions. In particular, most weather strips for doors are made of EPDM sponge rubber. These weatherstrips generally have improved appearance, lubricity,
A coating treatment is applied for the purpose of preventing squeak noise and accelerating freezing of ice in cold regions. This coating agent
Silicone-based and urethane-based ones are used, and silicone-based coating agents are considered to be useful in terms of heat resistance and weather resistance.

[0003]

However, the conventional silicone-based coating materials have the drawback that when they are coated, they give a luster (gloss), and when the coating film is transparent, surface irregularities and defects of the weather strip emerge and are conspicuous. There is also a problem that the wear resistance is poor.

In addition, organic peroxide curing type silicone rubber, addition reaction curing silicone rubber of alkenyl group and SiH by platinum catalyst, and condensation curing using hydrolyzable polyfunctional silane or siloxane as a crosslinking agent. It is known that matting is performed by blending an inorganic or organic spherical powder with a type of silicone rubber or the like. However, considering the applicability as a coating material, the organic peroxide curing type has a problem in the curability of a thin film. Further, the platinum addition reaction curing type has a problem of platinum catalyst poison due to the base material to be coated, and some of the base materials may hinder the curing, so that its use is limited. Furthermore, there are two types of condensation curing types, one-component type and two-component type.The one-component type is surface tack free, but the curing of the interface of the adherend is slow, and the two-component type does not cure. Although it can be accelerated, it has drawbacks that surface tack remains and the hardness of the rubber coating increases due to heating, resulting in poor durability. At present, a method of adding an inorganic filler such as silica, diatomaceous earth, or calcium carbonate is known to eliminate the gloss of the coating surface.
There is a problem that the addition of a large amount of inorganic filler significantly reduces the wear resistance of the coating film.

Therefore, the present invention effectively solves the above-mentioned problems and is capable of effectively forming a coating film, which is not particularly glossy and has excellent wear resistance, on the surface of a weather strip base material. An object is to provide a condensation-curable silicone-based coating composition.

[0006]

According to the present invention, (A) an organopolysiloxane having at least two silanol groups in one molecule (B) at least a hydrogen atom bonded to a silicon atom in one molecule. Provided is a coating composition for a weather strip, which comprises 3 or more organohydrogenpolysiloxane (C) organotin compound (D) spherical powder having an average particle size of 50 μm or less.

(A) Organopolysiloxane The component (A) used in the present invention is a main component polymer constituting the composition of the present invention, and is an organopolysiloxane containing at least two silanol groups in one molecule. Siloxane is not particularly limited in its molecular structure, but is preferably represented by the following general formula.

[Chemical 1] Here, R may be the same or different and is a monovalent substituted or unsubstituted hydrocarbon group, and n is a positive integer.

In the above general formula, R is specifically an alkyl group such as a methyl group, an ethyl group and a propyl group, an aryl group such as a phenyl group, an alkenyl group such as a vinyl group and an allyl group, and these groups. Examples thereof include groups in which some or all of the hydrogen atoms of the group have been replaced with halogen atoms and the like, such as trifluoropropyl group. In addition, a part of R may be a hydroxyl group if it is particularly required in terms of characteristics. In the present invention, it is preferable that all R's are a methyl group or a methyl group and a phenyl group. Further, n is preferably a value such that the viscosity of the organopolysiloxane at 25 ° C. is 300 cSt or more. Generally, the viscosity of the organopolysiloxane is 300 cS
If it is lower than t, the coating film may be too hard to cope with the deformation of the substrate. Furthermore, if the viscosity is too high, the workability will be poor and handling will be inconvenient, so in this case,
If appropriate, a suitable solvent can be used as a diluent. These organopolysiloxanes may be used in combination of two or more kinds as long as the viscosity is within the above range.

(B) Organohydrogenpolysiloxane The component (B) of the present invention, the organohydrogenpolysiloxane, acts as a cross-linking agent, and is added to the component (A) in the presence of the organotin compound described below. By carrying out a dehydrogenative condensation reaction with the silanol group of (3), a three-dimensional network-like cured product is formed and a coating film having practically necessary physical strength is formed. This organohydrogenpolysiloxane needs to have three or more hydrogen atoms bonded to Si atoms in one molecule in order to form a three-dimensional network-like cured product, but its molecular structure is not particularly limited. However, the shape may be any of linear, annular, branched, and three-dimensional. On the other hand, as the organic group bonded to the Si atom, an alkyl group such as a methyl group, an ethyl group and a propyl group, an aryl group such as a phenyl group, and at least a part of hydrogen atoms of these groups are substituted with a halogen atom or the like. A group, such as a trifluoropropyl group, can be mentioned. Preferably, the substituents other than hydrogen are all methyl groups, or a methyl group and a phenyl group. As such an organohydrogenpolysiloxane, one having a viscosity at 25 ° C. of 300 cSt or less is preferably used. Viscosity
When it is 300 cSt or more, the compatibility with the component (A) decreases,
The dehydrogenative condensation reaction may be insufficient.

These organohydrogenpolysiloxanes can be used alone or in combination of two or more, but the amount used is not particularly limited,
Generally, it is preferable that the amount is in the range of 1 to 50 parts by weight per 100 parts by weight of the component (A). If the amount is less than 1 part by weight, curing will be insufficient and it will be difficult to obtain a coating film having the required film strength. On the other hand, if it is used in an amount of more than 50 parts by weight, the resulting coating film becomes brittle or excessive Si—H bonds remain, which causes changes in physical properties over time.

(C) Organotin Compound The component (C) used in the present invention is for accelerating the dehydrogenative crosslinking reaction of the components (A) and (B). Specific examples of the organic tin compound include the following.

[Chemical 2] In the present invention, what is particularly preferably used is (C ₄ H ₉ ) ₂ Sn (OOCC ₁₁ H ₂₃ ) ₂ , (C ₄ H ₉ )
₂ Sn (OOCCH ₃ ) ₂ .

In the present invention, the blending amount of this component is (A) and (2) because of the dehydrogenative crosslinking reaction of the components (1) and (2).
As the amount of metal per 100 parts by weight of the total amount of component (B), 0.5
It is preferably in the range of -30 parts by weight, especially 0.6-25 parts by weight. If the amount added is too small, the function as a curing catalyst will not be fully exhibited, and the curing time will be long, while if it is too large, crosslinking will be rapid and workability will be reduced.

(D) Spherical powder In the present invention, the gloss (gloss) of the surface of the cured product obtained from the composition of the present invention is eliminated, and at the same time, the tackiness of the surface is reduced, and the cured product is In order to impart abrasion resistance to, spherical powders having an average particle size of 50 μm or less, preferably 20 μm or less are used. When the average particle size exceeds 50 μm, the mechanical strength of the obtained coating film (cured film) is impaired, and the coating film has poor abrasion resistance, for example. Furthermore, powders with an extremely fine average particle size
Since the production is difficult and no further effect can be obtained, the average particle size of the powder is 0.1 μm or more, especially 0.2 μm.
It is preferably m or more.

Here, the spherical powder refers to a spherical or substantially spherical shape whose shape is independent of each other, and as a guide, particles having a difference between the lateral diameter and the longitudinal diameter of the particles within ± 40%. In the present invention, the particle shape is preferably substantially spherical.

The material of the spherical powder is arbitrary as long as the average particle diameter is within the above range, and various inorganic powders such as metal oxides, polyester resins such as polyethylene terephthalate and polycarbonate, nylon and the like can be used. Polyamide resin, polyolefin resin such as polypropylene and polyethylene, plastic powder such as polyacetal resin and fluororesin can be used.
Most preferably used in the present invention is when the softening temperature is
Polymethylsilsesquioxane and metal oxides with a temperature of 150 ° C or higher. The above polymethylsilsesquioxane is
For example, methyltrialkoxysilane, orthoalkyl silicate or a partial hydrolyzate thereof is hydrolyzed and condensed in an aqueous solution containing an alkaline earth metal hydroxide or an alkali metal carbonate, or in an aqueous solution of amine or ammonia. It is obtained by hydrolyzing and condensing with (JP-A-63-77940 and JP-A-63-103812).
No., JP-A-63-295637). Further, this polymethylsilsesquioxane may contain an organic group such as a vinyl group, for example, the surface-modified poly (polysiloxane) disclosed in JP-A-63-101857 and JP-A-02-163127. Methylsilsesquioxane and the like can also be used. The spherical powder of metal oxide can be obtained, for example, by blowing oxygen into vapor of silicon and aluminum at high temperature (see JP-A-62-260712 and JP-A-63-74911).

In the coating composition of the present invention, a low-viscosity product, especially when a solvent as described below is included,
As (D), it is more preferable to use polymethylsilsesquioxane than a metal oxide such as alumina powder having a large specific gravity.
It is extremely advantageous because it does not cause separation or sedimentation.

The above-mentioned spherical powder is 20 to 1000 parts by weight, particularly 30 to 900 parts by weight, per 100 parts by weight of the total amount of the components (A) and (B).
It is preferably used in an amount of parts by weight. If it is less than 20 parts by weight, the desired effect is not exhibited, and if it is blended in an amount of more than 1000 parts by weight, the composition becomes hard and the workability of the coating is impaired, and the component (A) and the component (B Since the binder strength due to) is reduced, the mechanical strength of the cured coating is reduced.

Other Compounding Agents The composition of the present invention may contain various additives, fillers and the like known per se within a range that does not impair the object of the present invention. For example, fumed silica, precipitated silica, and hydrophobized products thereof are used as a reinforcing filler and an anti-settling agent. Various silicone resins and organic resins can also be used as the reinforcing filler. Of course, non-reinforcing fillers, extenders, heat-conducting fillers and the like can also be added. These fillers may be used alone,
You may mix 2 or more types. In addition, inorganic pigments, organic pigments, colorants such as organic dyes, cerium oxide, zinc carbonate,
It is also possible to add heat resistance and flame retardancy improvers such as manganese carbonate, benzotriazole, and platinum compounds.
Additives such as UV absorbers are also optionally used. Further, in order to adjust the physical properties of the cured product obtained from the composition of the present invention, trimethoxysilane, vinyltrimethoxysilane, triethoxysilane, vinyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, tetra (n Various silanes such as -propoxy) silane or partial hydrolysates thereof may be appropriately added. Also,
In order to improve the adhesion with the coating substrate, γ-
Glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ-
Aminopropyltriethoxysilane, N-benzyl-γ
It is also possible to add a sila coupling agent such as -aminopropyltrimethoxysilane or γ-mercaptopropyltrimethoxysilane and a partial hydrolyzate thereof. Also, γ-glycidoxypropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-benzyl-γ-amino. Propyltriethoxysilane or γ
Reaction products with mercaptopropyltrimethoxysilane and their partial hydrolysates can also be added. These are used alone or in combination of two or more. Further, nonfunctional silicone oil or nonfunctional silicone raw rubber may be added for the purpose of imparting lubricity to the surface of the coating film.

Coating Composition The coating composition of the present invention is easily prepared by uniformly mixing the above-mentioned components, but usually it is
The mixture of the components (A), (B) and (D) and the component (C) are separated and stored, and both are mixed at the time of use. Formation of a coating film using this composition can be performed, for example, by using (A),
The mixture of the components (B) and (D), if necessary, toluene,
Xylene, cyclohexane, n-hexane, n-heptane, industrial gasoline, solvent naphtha, mineral spirits, kerosene, isoparaffin, petroleum benzine,
Properly dilute using an organic solvent for organopolysiloxanes such as 1,1,1-trichloroethane and trichloroethylene, and dilute the component (C), which is a curing catalyst, with toluene, xylene, etc. in this diluted solution. After mixing, the composition is applied to a target substrate, and is cured at room temperature or by heat curing. Heat curing is usually performed at a temperature of 60 to 250 ° C for 30 seconds to
It takes about 30 minutes. The coating composition of the present invention forms a cured film having no luster or tackiness and excellent wear resistance, and therefore glass, ceramics, metals, plastics,
It is used as a coating agent for various base materials such as synthetic rubber and synthetic leather, and can be suitably used particularly as a coating agent for weather strips for automobiles.

[0020]

The present invention will be described in the following examples. In addition, all "parts" in each example represent "parts by weight", and the viscosity is 25
It is the measured value of ° C. Examples 1 and 2 100 parts of dimethylpolysiloxane (viscosity: 1000 cSt) in which both ends of the molecular chain were blocked with hydroxyl groups, specific surface area 120
20 parts of m ² / g of hydrophobic silica were mixed and kneaded with a blade-type stirrer for 1 hour. This mixture was passed through a triple roll three times to prepare a silicone base (a). On the other hand, 50 parts of the above-mentioned dimethylpolysiloxane blocked with hydroxyl groups at both ends and 50 parts of carbon black were mixed and further passed through a three-roll twice to obtain a black paste. Next, 30 parts of dimethylpolysiloxane crude rubber (viscosity: 3 million cSt) having both ends blocked with trimethylsilyl groups was dissolved in 950 parts of toluene. To 980 parts of this raw rubber solution, 6 parts of the silicone base (a), 5 parts of the black paste, and a particle size of 0.3 μm
Spherical powder consisting of m methylsilsesquisiloxane 60
Parts were added and mixed with stirring. Furthermore, γ-mercaptopropyltrimethoxysilane 1 was added to the obtained dispersion liquid.
And the following formula:

[Chemical 3] 1.5 parts of an organohydrogenpolysiloxane having a viscosity of 30 cSt represented by the following was added and mixed with stirring. to this,
20 parts by weight of 20% by weight toluene solution of (C ₄ H ₉ ) ₂ Sn (OOCC ₁₁ H ₂₃ ) ₂ was added and mixed to obtain a toluene dilution of the coating composition (coating solution) (Example 1). Further, in the above, a toluene dilution of the coating composition (coating liquid) was obtained in the same manner as above except that the compounding amount of the spherical powder was changed to 30 parts (Example 2).

Each coating solution prepared in Example 1 and Example 2 was applied to EPDM solid rubber sheet pieces in an amount of 10 to 20 μm.
It was applied so as to have a thickness of m 3 and heat-cured at 100 ° C. for 10 minutes. Measurement of glossiness of the obtained cured film,
The tackiness and wear resistance were evaluated, and the results are shown in Table 1. The glossiness is IG-310, a gloss meter manufactured by HORIBA, Ltd.
Was used under the conditions of an incident angle of 60 ° and a light receiving angle of 60 °.
The abrasion resistance was evaluated by the number of times of friction when the cured coating was peeled off by repeatedly rubbing with a cotton cloth.

Comparative Examples 1 and 2 A coating solution was prepared in the same manner as in Example 1 except that the spherical powder of methylsilsesquioxane was not used, and a cured coating was similarly formed. Was measured (Comparative Example 1). Also, instead of the spherical powder used in Example 1, diatomaceous earth (average particle size 10 μm)
A coating solution was prepared in the same manner except that 60 parts was used, and a cured coating was formed in the same manner, and the glossiness of the coating was measured (Comparative Example 2). The results are shown in Table 1.

[0023]

[Table 1]

Examples 3 and 4 50 parts of dimethylpolysiloxane (viscosity: 10,000 cSt) having both ends blocked by hydroxysilyl groups (viscosity: 10,000 cSt), 25 parts of hydrophobic silica having a specific surface area of 180 m ² / g, hexamethyldisilazane 1 Parts were mixed and kneaded by heating using a heating kneader. After cooling, 50 parts of the same dimethylpolysiloxane as above was further added and mixed to obtain a silicone base (II).
Was prepared. This base (b) 125 parts, black red iron 60
Parts, and 140 parts of spherical powder consisting of methylsilsesquioxane having a particle diameter of 1.2 μm were added and mixed with stirring. further,
To this mixture, 2 parts of γ-glycidoxypropyltrimethoxysilane and the following formula:

[Chemical 4] 20 parts of an organohydrogenpolysiloxane having a viscosity of 50 cSt represented by the following was added and mixed with stirring. It was then diluted with 500 g of toluene. Add (C _{4
H 9) 2 Sn (OOCCH 3} ) 20 wt% solution 30 parts of _2,
Was added and mixed to obtain a coating liquid (Example 3). Further, in the above, a coating liquid was obtained in the same manner as described above except that the compounding amount of the spherical powder was 70 parts (Example 4). Next, each coating solution is applied to the EPDM rubber sheet to a thickness of 10 to 20 μm, and the coating solution is applied at 200 ° C for 30 minutes.
It was heat-cured for 2 seconds. The glossiness of the obtained cured film was measured. The results are shown in Table 2.

Comparative Examples 3 and 4 A coating solution was prepared in the same manner as in Example 3 except that the spherical powder of methylsilsesquioxane was not used, and a cured coating was formed. The measurement etc. were performed (Comparative example 3). Also, instead of the spherical powder used in Example 3, diatomaceous earth (average particle size 10 μm) 140
A coating liquid was prepared in the same manner except that the parts were used, and a cured coating was formed in the same manner, and the glossiness of the coating was measured (Comparative Example 4). The results are shown in Table 2.

[0026]

[Table 2]

Comparative Examples 5 and 6 125 parts of the silicone base (ii) used in Example 3, 60 parts of black red iron oxide, 140 parts of spherical powder made of methylsilsesquioxane having a particle diameter of 1.2 μm were added and mixed, and further mixed. , 2.0 parts of ethyl polysilicate and 0.6 part of dibutyltin dilaurate were mixed with 500 parts of toluene to obtain a coating liquid. This coating liquid was used in Comparative Example 3,
In the same manner as in Example 4, the state of the cured film of the one coated on the EPDM rubber sheet and cured at room temperature for 24 hours (Comparative Example 5) and the one cured at 200 ° C. for 30 seconds (Comparative Example 6) was examined. The results are shown in Table 3 together with the results of Example 3. It can be seen that the hydrolyzable siloxane type cures very slowly and is inferior in abrasion resistance.

[0028]

[Table 3]

Examples 5 and 6 In place of the methylsilsesquioxane spherical powder used in Example 1, 60 parts (Example 5) and 30 parts of spherical silica (average particle size 30 μm, manufactured by Micron Corporation) were used. A coating solution was prepared in the same manner as in Example 1 except that the parts (Example 6) were blended, and a cured film was similarly formed,
The glossiness of the film was measured. The results are shown in Table 4.

[0030]

[Table 4]

[0031]

According to the present invention, it is possible to form a coating film having no gloss and excellent abrasion resistance on the surface of a weather strip base material.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takehide Okami 1 Hitomi, Osamu, Matsuida-cho, Usui-gun, Gunma 10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory

Claims (1)

[Claims] 1. (A) Organopolysiloxane containing at least two silanol groups per molecule (B) Organohydrogenpolysiloxane containing at least three hydrogen atoms bonded to silicon atoms per molecule. (C) Organotin compound (D) A coating composition for a weather strip, which comprises a spherical powder having an average particle diameter of 50 μm or less.