JPH06293782A - Coating composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition containing a condensate obtained by the cohydrolysis of a perfluoroalkyl silicate and a tetraalkyl silicate and giving a coating film having low-surface energy and high hardness and exhibiting moldreleasability and water repellency. CONSTITUTION:This composition contains a condensate obtained by the cohydrolysis of (A) a perfluoroalkyl silicate having >=3C perfluoroalkyl group (preferably trifluoropropyltrimethoxysilane, etc.) and (B) a tetraalkyl silicate having 1-4C alkyl (e.g. tetramethyl silicate) or its partially hydrolyzed oligomer. The cohydrolysis of the components A and B is preferably carried out by using 2-5mol of the component A based on 1mol of the component B in the presence of an acid catalyst such as hydrochloric acid. The reaction is usually carried out in the presence of a solvent dissolving the component A, the component B and water (e.g. THF). The component B is preferably a partially hydrolyzed alkoxysilicate oligomer from the viewpoint of the hardness, durability, etc., of the coating film.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a coating composition containing a silicate oligomer having a perfluoroalkyl group. More specifically, it relates to a coating composition having a low surface energy, releasability and water repellency, and capable of obtaining a coating film having high hardness.

[0002]

2. Description of the Related Art Conventionally, various coating compositions have been put to practical use, which form a film on the surface of a base material and impart properties such as releasability and water repellency. For example, fluororesins and the like are typical, but as a drawback, it has been pointed out that the adhesiveness to the base material is low. As a material for solving the drawback, a material containing a perfluoroalkyl group-containing polysiloxane is attracting attention because it has high adhesiveness to inorganic materials such as metals and glass and organic materials such as synthetic resins. For example, the following formulas of the compounds synthesized from perfluoroalkyl alcohol and alkyl silicate _{(Rf-C a H 2a -O} ) n -Si- (OR) 4-n (Rf
Is a perfluoroalkyl group, and a and n are each 1 to 10
And integers of 1 to 4) and the like have been proposed (Japanese Patent Laid-Open No. 22372/1990).

However, when such a perfluoroalkyl silicate is used alone to form a film, the perfluoroalkyl group tends to collect on the surface of the film. Therefore, it is difficult to form a coating film having a hard surface. Also,
When cured, the adhesion to the substrate may not be sufficient and durability may become a problem. Further, as a method for producing a high-molecular weight perfluoroalkyl group-containing polysiloxane, there is also a method in which the end of a liquid organopolysiloxane is silanolized and reacted with a perfluoroalkyl silicate (JP-A-2-97529). However, such a polymer having a high molecular weight is not suitable for a coating having high adhesiveness.

Further, when the perfluoroalkyl silicate and the tetraalkyl silicate oligomer are simply mixed, it is difficult to obtain a uniform film because they do not dissolve each other.

[0005]

An object of the present invention is to provide a coating composition having a low surface energy, having releasability and water repellency, and having high hardness and high adhesion to a substrate. It is a thing.

[0006]

Means for Solving the Problems As a result of intensive studies for the above purpose, it was found that the object can be achieved by co-hydrolyzing a specific perfluoroalkyl silicate and an alkyl silicate, and the present invention is achieved. Arrived That is, the gist of the present invention is to provide a perfluoroalkyl silicate containing a perfluoroalkyl group having 3 or more carbon atoms and a tetraalkyl silicate containing an alkyl group having 1 to 4 carbon atoms or a partially hydrolyzed oligomer thereof. A coating composition comprising a condensate obtained by cohydrolysis.

The present invention will be described in detail below. The perfluoroalkyl silicate containing a perfluoroalkyl group having 3 or more carbon atoms used in the present invention is not particularly limited as long as it contains a hydrolyzable alkoxy group. As the more preferable one, one represented by the following general formula (I) can be used.

[0008]

[Chemical 2]

(Wherein R ¹ is an alkyl group having 1 to 4 carbon atoms, R ² is a perfluoroalkyl group having 3 to 25 carbon atoms,
R ³ is an alkyl group having 1 to 4 carbon atoms, m is 1 to 3 and n is 0.
The following compounds may be mentioned as specific examples of the compound represented by the general formula (I).

Trifluoropropyltrimethoxysilane, tetrafluorobutyltrimethoxysilane, heptafluoropentyltrimethoxysilane, nonafluorohexyltrimethoxysilane, undecafluoroheptyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, pentadecafluoro Nonyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane,
Trimethoxysilanes such as nonadecafluoroundecyltrimethoxysilane, trifluoropropyltriethoxysilane, tetrafluorobutyltriethoxysilane,
Heptafluoropentyltriethoxysilane, nonafluorohexyltriethoxysilane, undecafluoroheptyltriethoxysilane, tridecafluorooctyltriethoxysilane, pentadecafluorononyltriethoxysilane, heptadecafluorodecyltriethoxysilane, nonadecafluoroun Triethoxysilanes such as decyltriethoxysilane, trifluoropropylmethyldimethoxysilane, tetrafluorobutylmethyldimethoxysilane, heptafluoropentylmethyldimethoxysilane, nonafluorohexylmethyldimethoxysilane, undecafluoroheptylmethyldimethoxysilane,
Examples thereof include methoxysilanes such as tridecafluorooctylmethyldimethoxysilane, pentadecafluorononylmethyldimethoxysilane, heptadecafluorodecylmethyldimethoxysilane, and nonadecafluoroundecylmethyldimethoxysilane.

The tetraalkyl silicate used in the present invention is a compound represented by the following general formula (II):

Embedded image Si (OR ⁴ ) ₄ (II) (wherein R is an alkyl group having 1 to 4 carbon atoms), and more specifically, tetramethyl silicate, tetraethyl silicate, tetrapropyl silicate , Tetrabutyl silicate and the like.

As the partially hydrolyzed alkyl silicate oligomer, the above-mentioned tetraalkyl silicate can be produced by a known hydrolysis method, and 30 to 80%, preferably 40 to 60%, and more preferably all alkoxy groups are contained. An oligomer obtained by reacting about 50% with water and condensation is used. As the co-hydrolysis in the present invention, a method in which a tetraalkyl silicate or a partial hydrolyzate thereof and a perfluoroalkyl silicate are coexistent in a solvent to simultaneously hydrolyze both, and a perfluoroalkyl silicate is first hydrolyzed to a terminal To a silanol group, and then tetraalkyl silicate or a partial hydrolyzate thereof is added, and a dealcoholization reaction is performed to condense the polymer to a high molecular weight.

In the latter case, unreacted perfluoroalkyl silicate remains unless at least equimolar water is used with respect to the perfluoroalkyl silicate. On the other hand, if more than twice the number of alkoxy group equivalents of perfluoroalkyl silicate is used in water, the tetraalkyl silicate or its partial hydrolyzate added later will be further hydrolyzed, and the entire gel will be formed. It is not preferable because it also has properties. That is, it is preferable to use water in an amount of more than the number of moles of perfluoroalkyl silicate and less than twice the number of alkoxy group equivalents of perfluoroalkyl silicate.

Further, if a large amount of tetraalkyl silicate or a partial hydrolyzate thereof added in the subsequent stage is used, there is little possibility of gelation during the reaction, so the minimum amount of perfluoroalkyl silicate required for the required physical properties should be used. Is preferred. As a result, there is an advantage that the amount of expensive perfluoroalkyl silicate can be reduced. The use ratio of perfluoroalkyl silicate and tetraalkyl silicate or a partial hydrolyzate thereof is not particularly limited. However, usually, for the above reason, it is preferable to select the amount of the perfluoroalkyl silicate with respect to the tetraalkyl silicate or the partial hydrolyzate thereof in the range of 0.1 to 20 times by mole, particularly 2 to 5 times by mole. If it is less than this range, the releasability and water repellency are low, and if it is more than this range, problems may occur in adhesiveness and hardness.

This hydrolysis is usually carried out in the presence of a solvent. The solvent is not particularly limited as long as it is a solvent that dissolves water and perfluoroalkyl silicate, tetraalkyl silicate or a partial hydrolyzate thereof,
Specific examples of the solvent include tetrahydrofuran, acetone, dioxane, methanol, ethanol, isopropyl alcohol, butanol and the like.

When alcohol is used as the solvent, the terminal group of tetraalkyl silicate or its partial hydrolyzate, the terminal group of perfluoroalkyl silicate, etc. may be substituted with the alkyl group of the alcohol component used in the solvent. It is also possible to control the physical properties of the coating composition of the present application by such a method. The amount of the solvent added can be selected from the range where the concentration of the non-volatile components in the reaction system is generally 2 to 90% by weight. If the concentration of non-volatile components in the reaction system is too high, insoluble components may occur in the system during hydrolysis, which is not preferable. In such a case, the resulting coating composition may also be separated into two phases, so it is preferable to use a relatively large amount of solvent and to minimize the non-volatile components.

The reaction can be carried out without a catalyst, but it is preferably used when the reaction time and the degree of polymerization are taken into consideration. As the catalyst, acids such as hydrochloric acid, phosphoric acid, sulfuric acid, nitric acid, paratoluenesulfonic acid, acetic acid are easily converted into linear polysiloxanes, so that a coating composition having a relatively low viscosity can be obtained, and gelation during the reaction, etc. Since it is unlikely to occur, it is preferably used.

In order to improve the storage stability of the coating composition or to control the reaction rate in a wide range, it is preferable that no catalyst remains in the composition, and therefore hydrochloric acid and nitric acid are particularly preferable. The hydrolysis temperature and time cannot be unconditionally specified because they differ depending on the type of alkoxy group of the silicate compound. For example, when the alkoxy group is a methoxy group, the hydrolysis time is about 2 to 60 minutes at 20 ° C., but when the alkoxy group is an ethoxy group or a butoxy group, it is necessary to carry out the hydrolysis for a longer time or at a higher temperature. is there.

After completion of the hydrolysis, tetraalkoxysilicate or a partial hydrolyzate thereof is added and the solvent is removed. In the process of removing the solvent, a silanol group and an alkoxy group react with each other to form a high molecular weight oligomer. Not tetraalkoxy silicate, but one obtained by partially hydrolyzing the silicate in advance to increase the molecular weight, that is, increasing the density of alkoxy groups having reactivity with the base material of mineral substances such as glass and stone in one molecule. When a partially hydrolyzed alkoxy silicate oligomer is used, the perfluoroalkyl group concentrates on the surface of the film, so that the crosslink density of the film can be increased without changing the performance of releasability and water repellency. It is particularly preferable because it is a film having high hardness, durability, and excellent adhesion to a substrate.

[0020]

EXAMPLES Next, the present invention will be described more specifically based on examples, but the present invention is not limited to the following examples without departing from the gist thereof. Here, the molecular weight is a molecular weight measured by GPC and converted into polystyrene size.

Example 1 21.8 g (0.1 mol, 3,3,3-trifluoropropyltrimethoxysilane)
0.3 equivalent) was dissolved in 20.0 g of methanol, 3.6 g of a 0.35 wt% hydrochloric acid aqueous solution was added to the obtained solution, and the mixture was allowed to stand at 20 ° C. for 10 minutes for hydrolysis.

Next, a partial hydrolyzate of tetramethoxysilane (“M-51” manufactured by Mitsubishi Kasei: 50%) was added to the reaction solution.
45.0 g of a hydrolyzed product, which is an oligomer mixture having a molecular weight of 250 to 3000) and refluxed for 2 hours,
When the temperature is raised to 130 ° C and methanol is allowed to flow out,
A colorless and transparent silicate oligomer was obtained. When the molecular weight of the oligomer is measured by GPC, the molecular weight is about 300-
It is a mixture of 4000 oligomers, each peak is different from the raw material, and the peak area distribution is also different, and it can be confirmed that the partial hydrolyzate of 3,3,3-trifluoropropyltrimethoxysilane and tetramethoxysilane has reacted. It was

[Example 2] 56.8 g (0.1 mol, 0.3 equivalent) of heptadecafluorodecyltrimethoxysilane was dissolved in 200 g of methanol, and the resulting solution was dissolved in a 0.35 wt% hydrochloric acid aqueous solution. 4 g was added, and the mixture was allowed to stand at 20 ° C. for 10 minutes for hydrolysis. Then, a partial hydrolyzate of tetramethoxysilane (“M-5
1 ") was added and refluxed for 2 hours, and then 1
When the temperature was raised to 30 ° C. and methanol was allowed to flow out, a colorless and transparent silicate oligomer was obtained.

When the molecular weight of the oligomer was measured by GPC, it was an oligomer mixture having a molecular weight of about 300 to 10,000, and it was confirmed that a partial hydrolyzate of heptadecafluorodecyltritrimethoxysilane and tetramethoxysilane reacted.

[Example 3] 56.8 g (0.1 mol, 0.3 equivalent) of heptadecafluorodecyltrimethoxysilane was dissolved in 200 g of methanol, and 5.4 g of pure water was added to the resulting solution. It was left for 30 minutes for hydrolysis. Next, 200 g of a partial hydrolyzate of tetramethoxysilane (“M-51”) was added to the above reaction solution, refluxed for 2 hours, then heated to 130 ° C. and methanol was flown out to obtain a colorless transparent silicate oligomer. .

When the molecular weight of the obtained oligomer was measured by GPC, it was confirmed that it was an oligomer mixture having a molecular weight of about 300 to 10,000 and that heptadecafluorodecyltrimethoxysilane and the partial hydrolyzate were reacted.

Example 4 2 g of the fluorine-containing silicate oligomer obtained in Example 2 and 0.2 g of dibutyltin dilaurate are dissolved in 10 g of methanol. When this liquid was applied onto a glass plate and dried, a transparent hard film was obtained. On the other hand, 2 g of the raw materials heptadecafluorodecyltrimethoxysilane and 0.2 g of dibutyltin dilaurate were added to 10 g.
Similarly, the liquid dissolved in the above methanol was applied onto a glass plate and dried to obtain a porous soft film.

Example 5 2 g of the fluorine-containing silicate oligomer obtained in Example 2 and 0.2 g of dibutyltin dilaurate are dissolved in 100 g of methanol. A sample is prepared by applying this solution on a glass plate by a dipping method and drying it (A). On the other hand, a solution prepared by dissolving 2 g of the raw material heptadecafluorodecyltrimethoxysilane and 0.2 g of dibutyltin dilaurate in 100 g of methanol is similarly coated and dried on a glass plate by the dipping method (B). When the contact angle of these samples with distilled water was measured using an automatic contact angle measuring device manufactured by Kyowa Interface Science Co., Ltd., the following results were obtained.

[0029]

[Table 1] Unpainted glass plate 43.3 ° Oligomer coated glass plate (A) 95.4 ° Heptadecafluorodecyltrimethoxysilane coated plate (B) 93.5 ° From these results, fluorine was added by oligomerization. It was confirmed that there was almost no difference in performance even though the amount decreased.

[0030]

According to the present invention, excellent releasability and water repellency,
A coating composition that produces a coating film with high hardness can be obtained.

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI Technical display location C09K 3/18 104 8318-4H C10M 105/76 9159-4H // C10N 40:36

Claims (3)

[Claims] 1. A co-hydrolysis of a perfluoroalkyl silicate containing a perfluoroalkyl group having 3 or more carbon atoms and a tetraalkyl silicate containing an alkyl group having 1 to 4 carbon atoms or a partially hydrolyzed oligomer thereof. A coating composition comprising a condensate obtained by the above. 2. The coating composition according to claim 1, wherein the perfluoroalkyl silicate is a compound represented by the following general formula (I). [Chemical 1] (In the formula, R ¹ is an alkyl group having 1 to 4 carbon atoms, R ² is a perfluoroalkyl group having 3 to 25 carbon atoms, and R ³ is 1 carbon atom.
To 4 alkyl groups, m is 1 to 3, n is an integer of 0 to 2, and m + n ≦ 3). 3. A perfluoroalkyl silicate represented by the general formula (I) is hydrolyzed in a solvent to convert a terminal group into silanol, and then a tetraalkyl silicate having an alkyl group having 1 to 4 carbon atoms or The coating composition according to claim 1 or 2, which is co-hydrolyzed with a partial hydrolyzate thereof.