JPH0764944B2 - Expandable polysiloxane composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel foamable polysiloxane composition, and more particularly to a room temperature curable foamed polysiloxane composition having improved foaming ratio and foam control property.

<Prior Art> Regarding the method of obtaining a silicone rubber foam at room temperature, as disclosed in JP-B-45-12675,
There are those in which some foaming agent is added when obtaining a normal room-temperature-curable silicone rubber elastic body, and those in which the curing mechanism itself of the room-temperature-curable silicone rubber composition has foamability. Of these, the latter method is known to be a dehydrogenation reaction between an organosilicon compound having a hydrogen atom directly bonded to a silicon atom and an organosilicon compound having a hydroxyl group directly bonded to a silicon atom, and dehydration is also known. Various catalysts are known for accelerating the elementary reaction.

For example, in JP-B-33-9297 and JP-B-44-8755, quaternary ammonium salts, carboxylates of heavy metals and alkali metal alkoxides are used, and in JP-B-45-9794, hydroxyamine compounds and silicon atoms are used. An organosilicon compound having an aminoxy group directly bonded is disclosed in JP-A-51-46.
Japanese Patent No. 352 discloses a platinum compound as a dehydrogenation reaction catalyst. However, in each of these cases, the expansion ratio is low, and the foam controllability of the cells is inferior, which is disadvantageous when trying to obtain effective heat insulation efficiency. Further, as disclosed in JP-A-59-45330, when the expansion ratio is improved by using α, ω-dihydroxyorganopolysiloxane having a low degree of polymerization, the cured silicone rubber foam is It has the drawback of low tensile strength.

<< Problems to be Solved by the Invention >> Therefore, an object of the present invention is to eliminate the above-mentioned drawbacks, and to provide a room-temperature-curable foamed polysiloxane composition which is excellent in expansion ratio, foam controllability of cells, and tensile strength. Especially.

The above object of the present invention "means for solving the problem" in, A. general formula HO - surface tension represented by ^{- (SiR 1 R 2 O-)} L -H is 22dyn
100 parts by weight of α, ω-dihydroxyorganopolysiloxane at e / cm · 25 ° C or higher, B. General formula R ₃ SiO-(-SiR ³ R ⁴ O-) _M -(-SiR ⁵ (OH) O-) _N -Organopolyhydroxypolysiloxane represented by SiR ₃ 0.01
To 50 parts by weight, C. A polyorganohydrogensiloxane having at least two units represented by the general formula R ⁶ _a H _b SiO 2 _{(4- (a + b)) / 2} in one molecule is used per mole of A + B + D silanol groups. An amount such that the SiH group is in the range of 0.5 to 30 moles, D. represented by the general formula (R ⁷ ₃ SiO _1/2 ) _X (R ⁸ SiO _3/2 ) _Y (SiO ₂ ) _Z , and hydroxy in the copolymer. An organosiloxane copolymer characterized by containing a silyl bond (0.01 to 1) mol / 100 g 0 to 100 parts by weight and platinum or a platinum-based compound which promotes the dehydrogenation reaction of the EA, B and D components and the C component, This is achieved by the expandable polysiloxane composition containing 0.1 to 200 ppm of platinum metal as an essential component based on the total weight of the components A + B + C.

In the above-mentioned general formula of the component A used in the present invention, in the formula, R ¹ and R ² are different or the same substituted or unsubstituted 1
Valent hydrocarbon group, l is an integer from 20 to 3,000 HOSiR ¹ R
Represented by ² O _L -H. The α, ω-dihydroxyorganopolysiloxane as the component A has a degree of polymerization of 20 to 3, because it imparts mechanical strength to the polysiloxane foam after curing.
Must be in the 000 range. When l is less than 20, the elongation of the polysiloxane foam after curing is not sufficient, and l is
If it exceeds 3,000, it is not preferable for handling work. The preferred range of 1 is 300 to 2,000.

Specific examples of R ¹ and R ² include, for example, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, an alkyl group such as a hexyl group, a vinyl group, an alkenyl such as an allyl group, and the like.
Aryl group such as phenyl group and naphthyl group, benzyl group,
An aralkyl group such as 2-phenylethyl group, or a chloromethyl group obtained by substituting a part or all of hydrogen atoms of these groups with a halogen atom, a 3,3,3 trifluoro group or the like, usually having 1 to 10 carbon atoms. , Preferably an unsubstituted or substituted monovalent hydrocarbon group having 1 to 8 carbon atoms, R ¹ and
R ² may be the same or different.

In particular, from the viewpoint of easy availability and surface tension, it is preferable that 5 to 20% of R ¹ is a phenyl group and R ² is a methyl group.

In the general formula of component B, R, R ³ , R ⁴ and R ⁵ are the same or different substituted or unsubstituted monovalent hydrocarbon groups as those of R ¹ and R ² described above,
From the viewpoint of easy availability and viscosity of the composition, R, R ³ , R ⁴ , R ⁵
It is preferred that all of the above are methyl groups or phenyl groups.

Further, M is an integer of 2 to 20 and N is an integer of 3 to 20, respectively, and it is particularly preferable that both M and N are in the range of 10 to 20. If N is less than 3, the expansion ratio is low, and the room temperature-curable foamable orisiloxane composition excellent in expansion ratio, which is the object of the present invention, cannot be obtained. On the other hand, if N exceeds 20, or M is less than 2, In that case, the production is difficult, and when M exceeds 20, the foamability of the composition deteriorates.

The amount of component B added is 0.01 to 100 parts by weight, preferably 20 to 60 parts by weight, based on 100 parts by weight of component A. If the amount of the component B added is less than 0.01 parts by weight, the expansion ratio will be low, and the room temperature-curable expandable polysiloxane foam excellent in expansion ratio, which is the object of the present invention, cannot be obtained. Further, if it exceeds 100 parts by weight, the mechanical strength of the polysiloxane foam is not sufficient.

The component C used in the present invention is a component which has a hydrogen atom directly bonded to a silicon atom and which produces a hydrogen gas by a dehydrogenation reaction with an organosilicon compound having a hydroxyl group directly bonded to the silicon atom and crosslinks. . The component C is _a polyorganohydrogensiloxane having at least two units represented by the general formula R ⁶ _a H _b SiO 2 _{(4- (a + b)) / 2} in one molecule. R ⁶ is a monovalent hydrocarbon group similar to R ¹ and R ² described above, and specific examples thereof include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group and the like having 1 to 1 carbon atoms. Alkyl group of 6, aryl group such as phenyl group and naphthyl group, chloromethyl group, 3,
Examples thereof include unsubstituted or substituted monovalent hydrocarbon groups having usually 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms, such as 3,3 trifluoro group. Each R ⁶ may be the same or different. From the viewpoint of easy availability, it is particularly desirable that R ⁶ is a methyl group or a phenyl group.

The hydrogen atom directly bonded to the silicon atom may be less than the molecule or may be in the side chain, and the constituent unit other than the unit represented by the above formula in the C component may be RSiO _3/2 , R ₂ Si.
O, R ₃ SiO _1/2 , and SiO ₂ (wherein R has the same meaning as described above), and the shape of the molecule may be chain, ring, or branched, but one molecule The number of silicon atoms in it is 30
It is preferably 0 or less. The component C is used in an amount of 0.5 to 30 moles, preferably 2 to 20 moles, of SiH groups per mole of A + B + D silanol groups.

If the amount is less than 0.5 mol, a room-temperature-curable foamable polysiloxane composition excellent in foaming ratio and bubble controllability cannot be provided. If it exceeds 30 mol, the polysiloxane foam will not provide sufficient mechanical strength (in the formula, R ⁶ is a monovalent hydrocarbon group, a is a number selected from 0, 1, 2 and b is 0, 1, 2,
A number selected from 3 is shown, and a + b is a number selected from 1, 2 and 3. ).

The component D organosiloxane copolymer used in the present invention is to impart excellent tensile strength and foam control to the room temperature curable foamable polysiloxane composition of the present invention. That is, since this organosiloxane copolymer has a hydroxysilane bond in the molecule, it undergoes a dehydrogenation reaction with the C component to crosslink while generating hydrogen gas, thereby giving the polysiloxane composition excellent mechanical strength. be able to.

In the above general formula showing the D component, R ⁷ and R ⁸ are respectively
The same as R ¹ and R ^{2 but} usually an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 8 carbon atoms,
R ⁸ may contain an alkenyl group such as a vinyl group, an allyl group or a butenyl group.

Further, X is an integer of 10 to 50, Y is 0 to 20, and Z is an integer of 20 to 100.

The hydroxysilane bond contained in one molecule of the above-mentioned organosiloxane copolymer in the present invention is (0.01 to 1) mol / 100 g, and particularly preferably in the range of (0.01 to 0.2) mol / 100 g. When the hydroxysilane bond is less than 0.01 mol / 100 g, sufficient cross-linking cannot be performed, and therefore the polysiloxane composition cannot be provided with excellent mechanical strength, and when it is 1 mol / 100 g or more, a sufficient expansion ratio can be obtained. Can not.

The E component used in the present invention is platinum or a platinum-based compound that accelerates the dehydrogenation reaction of the A, B and D components and the C component, and examples thereof include platinum metal, chloroplatinic acid, a complex of platinum and an olefinic compound, platinum. And a vinyl group-containing silane or siloxane complex, platinum phosphite complex, and the like. Among these, chloroplatinic acid and a complex of platinum and an olefinic compound are particularly preferable from the viewpoint that the stability of the composition before curing and a proper foaming rate can be provided. The E component is platinum metal based on the total weight of the A + B + C + D components.
The amount used is in the range of 0.1 to 200 ppm, preferably 1 to 50 ppm. If it is less than 0.1 ppm, the dehydrogenation reaction becomes slow and 200 ppm
If it exceeds, it will be economically disadvantageous.

The novel expandable polysiloxane composition of the present invention includes, as long as the object of the present invention is not impaired, a polyorganosiloxane having both ends or one end blocked with a triorganosilyl group as a diluent, or a vinyl group-containing silane or Siloxane can be added if desired. Further, other fillers, pigments, heat resistance improvers, flame retardants, and other additives can be used in combination.

<< Effects of the Invention >> The cured product obtained from the expandable polysiloxane composition of the present invention is superior to conventional ones in terms of foaming ratio and foam-regulating property and is excellent in tensile strength. Most suitable for the application.

<Examples> The present invention will be described in more detail below with reference to Examples, but the present invention is not limited thereto.

Example 1. The surface tension at 25 ° C is 24.1 dyne / cm, and the average structural formula is And the viscosity at 25 ° C is 20,000cs, α, ω −
Dihydroxy organopolysiloxane: (A-1), it is represented by average structural formula _{(CH 3) 3 SiOSi (CH} 3) 2 O 5 SiCH 3 (OH) O 10 -Si (CH 3) 3, a viscosity at 25 ° C. a 150cs organopolysiloxane hydroxy polysiloxane: (B-1), average structural formula _{(CH 3) 3 SiOSiCH 3 (} H) O 38 -Si (CH 3) polyorganohydrogensiloxane represented by _3: (C-1) , An organosiloxane copolymer represented by the average structural formula ((CH ₃ ) ₃ SiO _1/2 ) ₃₀ (CH ₃ SiO _3/2 ) ₈ (SiO ₂ ) ₄₀ (O _1/2 H) ₂ : (D-1 )
And isopropyl alcohol solution containing 2% chloroplatinic acid:
(E-1) was mixed at the compounding ratio shown in Table 1 to obtain a foamable polysiloxane composition.

When the obtained composition was cured by a known method,
Both the expansion ratio and the foam-controlling property were extremely good.

Example 2 A foamable polysiloxane composition was obtained in the same manner as in Example 1 except that (D-1) was not used. When this composition was cured in the same manner as in Example 1, as is apparent from Table 1, the foamability and foam-controlling property were good as in Example 1.

Comparative Example 1. Instead of (A-1) used in Example 1, the surface tension at 25 ° C. was 20 dyne / cm, and the average structural formula HO-
Represented by _{(-Si (CH 3) 2 O-} ) 600 -H, a viscosity at 25 ° C. is 20,000cs α, effervescent ω- other using dihydroxy organopolysiloxane in the same manner as in Example 1 A polysiloxane composition was obtained. When the obtained composition was cured in the same manner as in Example 1, as shown in Table 1, only those having a low expansion ratio and inferior foam-controlling property were obtained.

Comparative Example 2. Instead of the component (A-1) used in Example 2, the surface tension at 25 ° C. was 20 dyne / cm, and the average structural formula HO was obtained.
_{- (- Si (CH 3)} 2 O-) represented by ₆₀₀ -H, alpha viscosity at 25 ° C. is 20,000cs, ω- except for using dihydroxy organopolysiloxane in the same manner as in Example 2 foam A polysiloxane composition was obtained. When the obtained composition was cured in the same manner as in Example 1, as shown in Table 1, only those having a low expansion ratio and inferior foam-controlling property were obtained.

Claims (2)

[Claims] 1. A. General formula HOSiR ¹ R ² O _L —H, which has a surface tension at 25 ° C. of 22 dyne / cm or more,
100 parts by weight of ω-dihydroxyorganopolysiloxane (wherein R ¹ and R ² are different or the same type of substituted or unsubstituted monovalent hydrocarbon groups, and l is an integer of 20 to 3,000), B. General formula _{^{R 3 SiO-SiR 3 R 4}} O M SiR 5 (OH) organopolysiloxane hydroxy polysiloxane 0.01 represented by _O N -SiR ₃
To 100 parts by weight (wherein R, R ³ , R ⁴ and R ⁵ are monovalent hydrocarbon groups excluding different or the same substituted or unsubstituted aliphatic unsaturated hydrocarbon groups, M is 2 to 20, N represents an integer of 3 to 20), C. A polyorganohydrogensiloxane having at least two units represented by the general formula R ⁶ _a H _b SiO _{(4- (a + b)) / 2} in one molecule is A + B + D. In an amount of 0.5 to 30 moles of SiH group per mole of silanol group (in the formula, R ⁶ is a monovalent hydrocarbon group excluding aliphatic unsaturated hydrocarbon group, a is 0, 1 or 2) , B is 0, 1, 2,
3), where a + b is a number selected from 1, 2, 3), D. General formula (R ⁷ ₃ SiO _1/2 ) _X (R ⁸ SiO _3/2 ) _Y (SiO ₂ ) _Z And 100 to 100 parts by weight of an organosiloxane copolymer characterized by containing a hydroxysilyl bond (0.01 to 1) mol / 100 g in the copolymer (wherein R ⁷ is a heterogeneous or the same kind of substituted or unsubstituted). Monovalent hydrocarbon groups excluding aliphatic unsaturated hydrocarbon groups, R ⁸ is a heterogeneous or the same kind of substituted or unsubstituted monovalent hydrocarbon group, X is 10 to 50, Y is 0 to 20, Z Is an integer of 20 to 100), and platinum or a platinum-based compound that promotes the dehydrogenation reaction of the EA, B and D components and the C component requires 0.1 to 200 ppm as platinum metal with respect to the total weight of the A + B + C components. A foamable polysiloxane composition as a component. 2. A foam obtained by foaming and curing the composition according to claim 1.