JPH0410506B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a room-temperature-curable organopolysiloxane composition, and particularly to a room-temperature-curable organopolysiloxane composition that allows a coating to be easily applied to the surface of a silicone rubber after being cured at room temperature. Conventionally, organopolysiloxanes whose molecular chain ends are capped with hydroxyl groups are reacted with an amide group-containing organosilicon compound and/or an aminoxy group-containing organosilicon compound as a curing agent, and the entire composition is converted into a rubber-like elastic material at room temperature. Methods for curing are known. This composition uses a bifunctional compound and a trifunctional or higher polyfunctional compound as a curing agent, and by changing the ratio, it can be made from a low modulus/high elongation to a high modulus/low elongation. Physical properties can be changed over a wide range. In particular, low modulus and high elongation type compositions are widely used as architectural sealants due to the excellent weather resistance and fatigue resistance of organopolysiloxanes. However, one major drawback of these silicone sealants is that they cannot be painted (applying or adhering paint, the same applies hereinafter) to the surface of the cured silicone rubber. This drawback has limited the use of silicone sealants despite their excellent properties. As a result of intensive research into improving the paintability of silicone sealants, which is a major drawback of silicone sealants, the present inventors have developed a room-temperature-curable organopolysiloxane composition that allows paint to be applied well to silicone rubber surfaces after room-temperature curing. He came to invent this. That is, the present invention comprises: (A) 100 parts by weight of a linear diorganopolysiloxane having a viscosity of 20 to 1,000,000 centipoise at 25°C and whose molecular chain ends are blocked with hydroxyl groups; (B) functional groups in one molecule; 0.5 to 30 parts by weight of an organosilicon compound having two or more amide groups and/or aminoxy groups (C) General formula ⁽ In ^the formula ^, 0.05 to 15 parts by weight of dialkoxysilane or its partially hydrolyzed condensate (representing an unsubstituted monovalent hydrocarbon group) (D) 20 to 300 parts by weight of finely powdered calcium carbonate Paint after curing at room temperature The present invention relates to organopolysiloxane compositions that can be used. Component (A) used in the present invention serves as a base material of the present composition, and has the general formula HO[ _-R2SiO ] _-oH (wherein R is the same or different substituted or unsubstituted is a monovalent hydrocarbon group, and n is such that the viscosity of the organopolysiloxane composition is 20 to 20 at 25°C.
α,ω-dihydroxy-organopolysiloxanes with a value of 1,000,000 centipoise) are used. R is an alkyl group such as a methyl group, ethyl group, propyl group, or octyl group; an alkenyl group such as a vinyl group or an allyl group;
Aryl groups such as phenyl group, tolyl group, etc.
Examples include halogenated hydrocarbon groups such as chloromethyl group, cyanoethyl group, and 3.3.3-trifluoropropyl group. From the viewpoint of appropriate viscosity balance, it is preferable that 70% or more of R be methyl groups, and more preferably all of R be methyl groups. If the viscosity of the organopolysiloxane is less than 20 centipoise, it will not be possible to impart good physical properties to the rubber-like elastomer after curing, especially flexibility and high elongation. Also,
When it is larger than 1,000,000 centipoise, the viscosity of the composition becomes high, and workability during construction becomes extremely poor. Therefore, a range of 20 to 1,000,000 centipoise is chosen, more preferably a range of 200 to 200,000 centipoise. The organosilicon compound of component (B) used in the present invention is a curing agent for crosslinking and curing by reacting with the hydroxyl group of the organopolysiloxane of component (A) in the presence of moisture at room temperature. , it is necessary that one molecule contains two or more amide groups and/or aminoxy groups. If component (A) is an organopolysiloxane with a linear chain partially branched and three or more hydroxyl groups per molecule, the number of functional groups per molecule of component (B) must be It is possible to crosslink and cure only two or a combination of two and three or more. As such an amide group-containing organosilicon compound, dimethylbis(N-methylacetamide)
Silane, dimethylbis(N-ethylacetamide)silane, methylvinylbis(N-methylacetamide)silane, methylvinylbis(N-butylacetamide)silane, methyltris(N-phenylacetamide)silane, vinyltris(N-phenylacetamide)silane,
-ethylacetamido)silane, tetrakis(N
-Amidosilanes such as methylacetamido)silane, amidosiloxanes such as

Amidocyclosiloxanes such as [Formula] are exemplified. As aminoxy group-containing organosilicon compounds,
diphenylbis(diethylaminoxy)silane,
Methyltris(diethylaminoxy)silane,

[Formula] Aminoxysilanes such as Si [ON (C ₂ H ₅ ) ₂ ] ₄ , Aminoxysiloxanes such as Examples include aminoxycyclosiloxanes such as. Organosilicon compounds containing both an amide group and an aminoxy group in one molecule can also be used, but
It is not normally used due to the difficulty of synthesis and cost. As the curing agent of component (B), one or more kinds of amide group-containing organosilicon compounds may be used, or one or more kinds of aminoxy group-containing organosilicon compounds may be used. Two types of organosilicon compounds having different functional groups may be used in combination. In order for the curing agent of component (B) to crosslink and harden by reacting with the linear diorganopolysiloxane usually preferably used as component (A) and endblocked with hydroxyl groups at both ends, it is necessary to have an average of 2 in the molecule. The number of amide groups or aminoxy groups must be contained. average 2
This is because a sufficient hardened film cannot be formed on the surface if the amount is less than 1. Of course, the present invention can contain 3 or 4 amide groups or aminoxy groups in one molecule.
Although this includes cases where a curing agent containing more than one amide group or aminoxy group is used as a curing agent, it usually includes one containing two amide groups or aminoxy groups in one molecule, and one containing three or more amide groups or aminoxy groups in one molecule. Mix and use as appropriate. There is no particular limitation on how the functional numbers of the amide group and the functional number of the aminoxy group are combined, but it is necessary to achieve low modulus and high elongation, or to improve storage stability when packaged in one package. It is preferable to use the one with higher reaction activity as the bifunctional component in view of the properties and the like. In general, an amide group-containing organosilicon compound has higher reactivity than an aminoxy group-containing organosilicon compound, so for example, when using an amide group-containing organosilicon compound as a bifunctional component, It is preferable to use an amide group-containing organosilicon compound or an aminoxy group-containing organosilicon compound as a component, and when an aminoxy group-containing organosilicon compound is used as a bifunctional component, an aminoxy group-containing component is used as a trifunctional or more functional component. Preference is given to using organosilicon-containing compounds. If the amount of component (B) added is too small, curing will be insufficient and storage stability will deteriorate when packaged in one package.If it is too large, the curing speed will be slow, which may be economically disadvantageous. Therefore, the amount is in the range of 0.5 to 30 parts by weight, preferably 1 to 20 parts by weight, based on 100 parts by weight of the organopolysiloxane (A). The dialkoxysilane or its partially hydrolyzed condensate as component (C) used in the present invention is an important component for imparting paintability to the silicone rubber surface after room temperature curing of the composition, which is the object of the present invention. It is an ingredient. If component (C) is not added, paint cannot be applied or adhered to the surface of the cured rubber-like elastic body, but if component (C) is added, various paints can be applied and adhered extremely easily. . Furthermore, the reason why component (C) is limited to dialkoxysilane or its partially hydrolyzed condensate is that, for example, when a trialkoxysilane compound is used, the paintability of the paint is inferior to that of dialkoxysilane, and The surface tackiness of the cured composition is too high, and the fluidity of the uncured composition is too high, resulting in poor workability.Also, even if a certain composition is used, the strength of the silicone rubber may change after curing. This is because it is large and difficult to control. (C) component is the general formula

It is a dialkoxysilane represented by the formula or a partially hydrolyzed condensate thereof. X is a monovalent group selected from the group consisting of a substituted or unsubstituted mercapto group, an amino group, an acryloxy group, and an epoxy group. Substitution here means, for example, in the case of an amino group

[Formula] Group

[Formula] includes groups, etc., and in the case of an acryloxy group, it means that a methacryloxy group is included. R ¹ is a divalent organic group, which includes methylene group, ethylene group, propylene group, butylene group, chloroethylene group, fluoroethylene group, phenylene group, -CH ₂ OCH ₂ CH ₂ CH ₂ - group, - CH ₂ CH ₂ OCH ₂ CH ₂
basis,

[Spreadability test]

The present composition and the composition of the comparative example were cured into a sheet-like elastic body with a thickness of 2.5 mm, and a paint was applied to a 5 cm square area of the surface (one coat with a brush).
Judging by how well the paint repels. If it can be applied evenly, it is rated as ○, if it can be applied to 50 to 90% of the entire area, it is △, and when it is less than 40%, it is marked as ×. [Adhesiveness Test] After conducting the coating property test, if the paint is repellent, apply 2 to 3 coats to cover the entire surface as much as possible. After confirming that the paint was sufficiently cured, 18 mm wide cellophane tape was pasted on the paint film and peeled off to check for peeling of the paint film. ○ when the coating film and cured sheet adhere well; × when peeling off with little resistance;
Anything in between is marked △. Example 1 α, ω with a viscosity of 6000 centipoise at 25°C
30 parts of light calcium carbonate and 40 parts of light calcium carbonate were added to 100 parts of -dihydroxy-dimethylpolysiloxane and mixed until uniform. 100 parts of this base mixture, 1.5 parts, as 1.5 parts and component (C)

1 part and 2 parts of [Formula] were respectively added and mixed until uniform. Using this composition, a 2.5 mm thick sheet was prepared and left to stand at room temperature for one week to harden into a rubber-like elastic body.
A spreadability test and an adhesion test were conducted on this product. Also, using the same composition, JIS-
An H-type joint specified in A7558 (adherent glass, using Primer D manufactured by Toray Silicone Co., Ltd.) was prepared, and after being left at room temperature for two weeks, a tensile test was conducted. On the other hand, as a comparative example, component (C) from the above composition was

A composition excluding only [Formula] was prepared, and the thickness was
Create a 2.5mm sheet and H-type joint,
Spreadability tests, adhesion tests and tensile tests were conducted. These results are shown in Table 1.

[Table] Example 2 Component (C) used in Example 1 The same composition as in Example 1 was prepared, except that the organosilicon compounds shown in Table 2 were used instead, and the same tests as in Example 1 were conducted. The results are shown in Table 1. For convenience, the comparative example used in Example 1 is also listed.

[Table] Example 3 α, ω with a viscosity of 9000 centipoise at 25°C
-Dihydroxy-dimethylpolysiloxane (100 parts) was uniformly mixed with 40 parts of light calcium carbonate and 50 parts of heavy calcium carbonate. 100 parts of this base mixture,

2.7 parts of [formula],

A composition was prepared by uniformly mixing 0.3 parts of [Formula] and the organosilicon compounds shown in Table 3 as component (C). Using this composition, Example 1
I conducted a similar test. In addition, as a comparative example
The same test was conducted for a composition in which only component (C) was not added. The results of these tests are shown in Table 3.

[Table] Example 4 α with a viscosity of 12000 centipoise at 25°C,
ω-dihydroxy-dimethylpolysiloxane 100
30 parts of light calcium carbonate and 70 parts of heavy calcium carbonate were mixed until uniform. To 100 parts of this base mixture, 4 parts of dimethylbis(N-ethylacetamido)silane,

0.5 part of [formula], and

One part of formula was added and mixed until homogeneous. When 2.5 mm thick elastomer sheets made using this composition were subjected to a coating test and an adhesion test, the results were as follows: Paint A, Paint B, and Paint C (same as above).
Both were successfully applied and bonded.

Claims (1)

[Claims] 1 (A) A linear diorganopolysiloxane having a viscosity at 25°C of 20 to 1,000,000 centipoise and whose molecular chain ends are blocked with hydroxyl groups.
100 parts by weight (B) Organosilicon compound having two or more amide groups and/or aminoxy groups as functional groups in one molecule 0.5 to 30 parts by weight (C) General formula ⁽ In ^the formula ^, 0.05 to 15 parts by weight of dialkoxysilane or its partially hydrolyzed condensate (representing an unsubstituted monovalent hydrocarbon group) (D) 20 to 300 parts by weight of finely powdered calcium carbonate Paint after curing at room temperature Organopolysiloxane compositions that make it possible.