JPS6217624B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is a one-component organopolysiloxane composition that has excellent storage stability under sealed conditions, and when exposed to the atmosphere after being applied to various substrates, quickly cures at room temperature to form a cured coating film with excellent physical properties. It is related to. Conventionally, various types of so-called room-temperature-curing organopolysiloxane compositions have been developed, which are stable when sealed in the absence of moisture, but when exposed to the atmosphere, react with moisture in the air and harden at room temperature to form a film. One-component compositions are known, and in particular, one-component compositions include dealcoholization, acetoxylation, oximeation, and acetonation types based on their curing mechanism. Among these, examples of oxime-free compositions include (1) those in which the molecular chain end is an oxime group;

A composition consisting of an organopolysiloxane blocked by [Formula] and an amino group-containing silane compound (see Japanese Patent Publication No. 16547/1983) or
(2) A composition comprising a paint resin containing a Si--OH bond and an organosilicon compound having at least two oxime groups in one molecule (see JP-A-52-101234) has been proposed. However, since the composition (1) above uses an amino group-containing silane compound as a reaction promoter, it has the disadvantage that the resulting cured film is difficult to obtain sufficiently satisfactory electrical properties. On the other hand, although the cured film obtained from the composition (2) has excellent electrical properties, this composition has the disadvantage that the curing speed is relatively slow and curing takes a long time. The present invention aims to provide a novel room-temperature curable organopolysiloxane composition which eliminates the conventional disadvantages and disadvantages as described above, and which comprises (a) at least hydroxyl groups bonded to silicon atoms;
Organopolysiloxane containing 0.05% by weight, (b) having at least two oxime groups in one molecule directly bonded to a silicon atom, having the formula (In the formula, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group, R ² and R ³ are hydrogen atoms or substituted or unsubstituted monovalent hydrocarbon groups, a and b
0≦a≦3 and 0<b≦3, respectively); and (iii) an organoaluminum compound. The composition of the present invention comprising the above-mentioned components (a) to (c) can be stored stably for a long period of time under sealed conditions in the absence of moisture. It has the feature of quickly curing under the action of moisture and forming a cured film with excellent electrical properties. Hereinafter, the composition of the present invention will be explained in detail. First, the organopolysiloxane as component (a) constituting the composition of the present invention has at least 0.05% by weight of hydroxyl groups bonded to silicon atoms in its molecule.
There are no particular restrictions except that it must be included. The reason why it is essential that the amount of hydroxyl groups is 0.05% by weight or more is that if it is less than the above range, the curing speed at room temperature will be slow and the surface will still feel sticky even after a long period of time. This is because even if a cured film is obtained, this film easily deteriorates, swells, and dissolves when it comes into contact with solvents. The organopolysiloxane has an alkoxy group bonded to a silicon atom (〓Si-OR ⁴ ,
R ⁴ ; alkyl group such as methyl group and ethyl group), allyl group (〓Si-R ⁵ , R ⁵ ; allyl group such as vinyl group),
Acyloxy group (

[Formula] R ⁶ ; hydrogen atom or monovalent hydrocarbon group) or hydrogen atom (〓
_There is no problem even if it contains reactive atoms or groups such as Si-H), and _the molecular structure is R ₂ SiO units, RSiO _1.5 units, R ₃ SiO _0.5 units (R is may optionally contain monovalent hydrocarbon groups) or SiO ₂ units. Generally, when trying to form _{a hard film, an organopolysiloxane with a high content of monoorganosiloxane units (RSiO 1.5 units} ) and a high amount of hydroxyl groups bonded to silicon atoms is used as component (a). On the other hand, when trying to form a flexible film with rubber elasticity, a linear organopolysiloxane with a large number of diorganosiloxane units (R ₂ SiO units) and silanol groups at both ends is used. This is desirable. In the present invention, this component (a) is 50%
It is desirable to use a toluene solution with a viscosity of 2.0 cS or more at 25°C. This is because films obtained using organopolysiloxanes having a viscosity of less than 2.0 cS have poor mechanical strength (brittleness) and lack reliability. In addition, this component (a) may be modified with synthetic resins such as alkyd resins, polyester resins, polyether resins, epoxy resins, acrylic resins, or phenolic resins, as long as it contains 0.05% by weight or more of hydroxyl groups bonded to silicon atoms. Modified polysiloxane resins can also be used. Next, the organosilicon compound as component (b) used in the present invention has an oxime group (

A formula having at least two functional groups represented by [Formula] (R ² and R ³ are the same as above) In the above formula, R ¹ represents a substituted or unsubstituted monovalent hydrocarbon group, which includes alkyl groups such as methyl, ethyl, propyl, butyl, groups, alkenyl groups such as vinyl groups and allyl groups, phenyl groups,
Examples include aryl groups such as tolyl groups, and groups in which the hydrogen atoms of these groups are partially substituted with halogen atoms, amino groups, cyano groups, etc. Further, R ² and R ³ are selected from a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, and examples of the monovalent hydrocarbon group include substantially the same groups as those exemplified for R ¹ above. . a and b are each as described above,
When the organosilicon compound represents silane, a
and b are 1, 2 or 3, respectively, and a+
b is 4. In addition, when it represents siloxane, a and b are each positive numbers, and a+
b<4 (preferably a+b=3). In addition, when the organosilicon compound contains two or more R ¹ in one molecule, these R ¹ do not necessarily have to be the same, and may be different kinds, and R ² in the oxime group It goes without saying that R 3 and R ³ may also be of different types. Such oxime group-containing organosilicon compounds include silane (a+b=4) and siloxane (a+
b<4), and examples of the oxime group-containing silane include methyltrichlorosilane, dimethyldichlorosilane, trimethylmonochlorosilane, ethyltrichlorosilane, diethyldichlorosilane, phenyltrichlorosilane, diphenyldichlorosilane, and phenylmethyl. Chlorosilanes such as dichlorosilane, diphenylmethylmonochlorosilane, vinyltrichlorosilane, vinylmethyldichlorosilane and oximes such as acetoxime, methylethylketoxime, butyraldoxime, methylbutylketoxime,
Examples include various silane compounds obtained by dehydrochlorination reaction in the presence of a hydrochloric acid scavenger such as pyridine, and oxime group-containing siloxanes obtained by partial hydrolysis of oxime group-containing silanes obtained by the above-mentioned method. Various types of products obtained by doing this are exemplified. Specific examples of the oxime group-containing silane or siloxane are as follows. However, in the following description, Me represents a methyl group, Et represents an ethyl group, i-Pr represents an iso-propyl group, n-Pr represents an n-propyl group, Bu represents a butyl group, Ph represents a phenyl group, Vi each represents a vinyl group. The amount of component (b) to be used is preferably such that at least one mole of oxime groups in component (b) is provided per mole of silanol groups in component (a). There is no particular restriction on the upper limit of component (B), but for example, component (A) has 5% by weight or more of silanol groups, and component (B) has b=3 in the general formula.
oxime group per mole of silanol group in the case of
When mixed at a ratio of 0.5 to 1 mole, gelation reaction is likely to occur even under sealed conditions at room temperature, and conversely, if component (B) is too large, the strength of the final film will be poor. Therefore, it is generally considered to be about 5 moles. Next, the organoaluminum compound as component (c) used in the present invention causes a deoxime reaction between component (a) and component (b) due to the action of moisture to newly generate siloxane bonds. It acts as a co-catalyst for In general, siloxanes whose molecular chain ends are blocked with oxime groups undergo a hydrolysis reaction under the action of moisture to produce siloxane bonds, but this reaction takes a relatively long time, so industrially it is difficult to promote the reaction in some way. Component (c) in the composition of the present invention plays this role. Specifically, the organic aluminum compounds as component (iii) include (MeO-) ₃ Al, (EtO-) ₃ Al, (n-PrO-)
Aluminum alcoholate such as Al, obtained by reacting aluminum alcoholate with acetoacetate or dialkyl malonate, etc. aluminum chelate compounds, aluminum salts such as naphthenic acid, stearic acid, octylic acid or benzoic acid, known as aluminum soap;

【formula】

Examples include organic acid salts of aluminum oxide such as [Formula], and aluminum acetylacetonate [Al(C ₅ H ₇ O) ₂ ]. It has been reported that a cured product can be obtained by blending an aluminum compound, specifically an aluminum-modified phenolic resin, into an organopolysiloxane resin and heat-treating this at a temperature of 100°C for 15 minutes (West German Patent No. 951889). (see specification), but
This method involves curing by heating, and is essentially different from the method of the present invention in which the oxime group acts as a hydrolysis accelerator at room temperature. The amount of component (c) used is 0.1 to 15% by weight, preferably 0.5 to 15% by weight, based on the total amount of components (a) and (b).
The content is preferably in the range of 10% by weight. This is because when the amount used is less than 0.1% by weight, the promoter effect is small;
On the other hand, even if 15% by weight or more is added, no significant effect can be obtained due to the use of this large amount, and it becomes economically disadvantageous. The composition according to the present invention can be prepared by conventionally known methods, such as
When mixing components (a) and (b), an inert organic solvent may be used as necessary, and if toluene or xylene is used, it can be directly mixed with (b)
The ingredients may be added and mixed by stirring at room temperature or under heating, and an inert organic solvent such as toluene or xylene may be further added for the purpose of adjusting the viscosity. Note that if water is present in these mixed systems, there is a risk of gelation, so it is desirable to remove as much water as possible (preferably 0.5% by weight or less) before mixing. In addition, when mixing component (iii) at room temperature, if it is added alone, the concentration will be high in some areas and the mixture will become non-uniform and it will take a long time to dissolve. It is preferable to add it afterwards. Note that organic dyes, organic or inorganic pigments, thickeners, and the like may be added to the composition of the present invention within a range that does not impede the above-mentioned purpose. In particular, when applying the composition to electrical or electronic parts, an inorganic filler such as pure SiO ₂ or Al ₂ O ₃ is used to improve the electrical properties, heat resistance, water resistance, etc. inherent to organopolysiloxane. It is necessary to consider so as not to impede the features of Furthermore, when applied to painting general large equipment, outdoor buildings, etc., a thixotropic agent may be added to improve the painting work. Furthermore, in order to impart water repellency to cement or clay products such as concrete, mortar, and bricks, or composite building materials such as asbestos board and gypsum board, the above-mentioned method is used to improve the impregnability of these products. It is best to avoid adding fillers, pigments, etc. as much as possible, use a solvent as much as possible to lower the viscosity, and use it as a transparent solution. Next, examples of the present invention will be given. Example Experiment 1 First, an organopolysiloxane composition was prepared as follows. Composition (product of the present invention) consisting of _{18 mol% MeSiO 1.5 units} , _{50 mol% PhSiO 1.5 units} , 27 mol% Me ₂ SiO units and 5 mol% Ph ₂ SiO units, Me/Si = 0.72, Ph /Si=0.60,
100 g of methylphenylpolysiloxane (as solid content) with a hydroxyl group content of 3.2 parts by weight and a 50% toluene solution having a viscosity of 25 cS at 25°C;

[Formula] After mixing and dissolving 56.6g in 100g of toluene, add 78.3 g of a 10% toluene solution was added and stirred vigorously for 1 hour. Composition (product of the present invention) Consists of _{45 mol% MeSiO 1.5 units} and 55 mol% Me ₂ SiO units, Ph/Si = 1.55, hydroxyl group content 1.7
100g (solid content) of methylpolysiloxane with a methoxy group content of 2.1% by weight and a viscosity of 42cS at 25°C in a 50% toluene solution;

After dissolving 60.0 g of the formula in 100 g of toluene, 16 g of a 10% toluene solution of aluminum octylate was added thereto, and the mixture was vigorously stirred for about 1 hour. Composition (product of the present invention _{) PhSiO 1.5 units} 56 mol%, Me ₂ SiO units 34 mol%
and Ph ₂ SiO units, Me/Si=0.68,
Ph/Si=0.76, hydroxyl group content is 1.1% by weight, 50%
100 g of silicone alkyd resin (alkyd resin content 30%) modified with siloxane whose viscosity at 25°C in toluene solution is 88 cS and

[Formula] After dissolving 16.5g in 100g of toluene, add

[Formula] 7.0g dissolved in 28g of toluene was added and mixed uniformly. Composition (product of the present invention) MeSiO _{1.5 units 5} mol% _, PhSiO _0.5 units 5 mol%, Me ₂ SiO units 75 mol% and ViSiO _1.5 units 15
Consisting of mol%, Me/Si=1.55, Ph/Si=
0.05, Vi/Si=0.15, hydroxyl group content 0.4% by weight,
100g (solid content) of methylvinylphenylsiloxane whose viscosity at 25℃ is 11cS in 50% toluene solution. After mixing and dissolving 10.2g, add 10% of the same aluminum compound used in the above composition.
11 g of toluene solution was added and mixed uniformly. Composition (Comparative) A composition having the same composition as above except that no aluminum compound was used was treated in the same manner. Experiment 2 The composition ~ obtained above was applied to a mild steel plate and left in a room at 25°C.The physical properties of the film after standing were examined and the results are shown in the table below.

【table】

Claims (1)

[Scope of Claims] 1 (a) an organopolysiloxane containing at least 0.05% by weight of hydroxyl groups bonded to silicon atoms; (b) having at least two oxime groups in one molecule directly bonded to silicon atoms; formula (In the formula, R ¹ is a substituted or unsubstituted monovalent hydrocarbon group, R ² and R ³ are hydrogen atoms or substituted or unsubstituted monovalent hydrocarbon groups, a and b
an oxime group-containing organosilicon compound represented by 0≦a≦3 and 0<b≦3, respectively; and (c) an organoaluminum compound.