JPS6343934A - Room temperature-curable organosiloxane composition for forming foam - Google Patents

Abstract

PURPOSE:To obtain the title composition which has a uniform foam-stabilizing property and can give a tough foam, by mixing a diorganopolysiloxane of a specified composition with an organohydrogensiloxane and a silane or a siloxane at a specified weight ratio. CONSTITUTION:100pts.wt. diorganopolysiloxane (A) both of whose terminals are blocked with hydroxyl groups (e.g., alpha-omega-dihydroxydimethylpolysiloxane) is mixed with an organo-hydrogensiloxane (B) of formula I (wherein R<1> is a monovalent hydrocarbon group, b is 0, 1 or 2, c is 1-3 and b+c=1-3), e.g., formula II, in an amount to provide 0.5-10mol of Si-bonded hydrogen atoms per mol of the hydroxyl groups of component A, and 0.01-5pts.wt. silane or siloxane (C) having at least one group of formula III (wherein R<2> is a monovalent hydrocarbon group) in the molecule (e.g., formula IV) to obtain the title composition suitable as a base for, e.g., a material for packaging electronic components.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a room-temperature curable organosiloxane composition for forming a foam, particularly a novel foaming method for forming an organosiloxane foam by a dehydrogenation reaction of an organosiloxane. The present invention relates to a room temperature curable organosiloxane composition for body formation.

(Prior art) Regarding organosiloxane compositions for obtaining silicone rubber foams, there is a method of adding a blowing agent to a room-temperature curable organosiloxane composition (see Japanese Patent Publication No. 12675/1983), A method is known in which an organosilicon compound having a hydrogen atom (SiH group) is subjected to a dehydrogenation reaction with an organosilicon compound having a hydroxyl group (=SiOH group) bonded to a silicon atom. A method using a quaternary ammonium salt, a heavy metal carboxylate, or an alkali metal alkoxide as a catalyst for elementary reactions has been proposed (Japanese Patent Publication No. 33-9297).

(See Special Publication No. 47-8755).

Furthermore, methods for producing silicone rubber foams using hydroxyamine compounds and organosilicon compounds containing aminoxy groups bonded to silicon atoms are also known (Japanese Patent Publication No. 57-9497, Japanese Patent Publication No. 45-11). ,839
, Japanese Patent Publication No. 59-45,329, Japanese Patent Publication No. 57-180,
No. 641-180,642, JP-A-58-57,461
(see Japanese Patent Publication No. 1987-46,352, Japanese Patent Publication No. 59-1982), and methods using platinum as a catalyst are also known.
-45.330)).

However, quaternary ammonium salts as dehydrogenation reaction catalysts,
Methods using heavy metal carboxylates and alkali metal alkoxides, as well as methods using hydroxyamine compounds and organosilicon compounds containing aminoxy groups bonded to silicon atoms, all have odors that create a bad working environment. Furthermore, these catalysts can cause cranking of silicone foams at high temperatures, and they also have the disadvantage of being corrosive to metals.

When a platinum catalyst is used, there is a disadvantage that the platinum catalyst is poisoned by ion-containing compounds, phosphorus-containing compounds, or nitrogen-containing compounds in the presence of these compounds and loses its catalytic effect, making it impossible to obtain a foam.

(Structure of the Invention) The present invention relates to a room-temperature curable organosiloxane composition for forming a foam that solves the above-mentioned disadvantages. Parts by weight, B) General formula R'H5iO Rainbow C (wherein R1 is an unsubstituted or substituted monovalent hydrocarbon group.

b is 0.1 or 2, C is 1.2 or 3, b+C is 1
．． 2 or 3), the hydroxyl group 1 in the above component A)
Hydrogen atoms bonded to silicon atoms (=SiH
C) an organohydrodiene siloxane of the general formula (R"N)2C=N-(
R3 is characterized by comprising 0.01 to 5 parts by weight of a silane or siloxane containing at least one group represented by a hydrogen atom or an unsubstituted or substituted monovalent hydrocarbon group in one molecule. It is.

That is, the present inventors have the disadvantages described above.

As a result of various studies on the production method of silicone rubber foam by a dehydrogenation reaction without any drawbacks, we found that a mixture of diorganopolysiloxane and organohydrodienesiloxane in which both ends of the molecular chain are blocked with hydroxyl groups is expressed by the above general formula. When a silane or siloxane containing a guanidyl group is blended, it acts effectively as a catalyst for dehydrogenation between diorganosiloxane and organohydrodiene siloxane, and this composition undergoes a dehydrogenation crosslinking reaction at room temperature, so it can be easily Silicone rubber foam can be obtained, and the guanidyl group-containing silane and siloxane are odorless and corrosive, and siloxane does not crack even at high temperatures, so it can be used safely without deteriorating the working environment. They discovered that it was possible to obtain an organosiloxane foam with excellent properties, and completed the present invention by conducting research on the types and amounts of each ingredient used in the knee.

The diorganopolysiloxane as component A) constituting the composition of the present invention is considered to be the main ingredient of this composition, and is represented by the average composition formula RS x Oa-, where R is a methyl group, Alkyl groups such as ethyl group, propyl group, butyl group, 2-ethylbutyl group, octyl group, cycloalkyl group such as cyclohexyl group, cyclopentyl group, alkenyl group such as vinyl group, hexenyl group, phenyl group, tolyl group, xylyl group , aryl groups such as naphthyl and diphenyl groups, and aralkyl groups such as benzyl and phenylethyl groups.

or a chloromethyl group, trifluoropropyl group, 2-cyanoethyl group, 3-cyanopropyl group, etc. in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with a halogen atom, a cyano group, etc. the same or different unsubstituted or substituted monovalent hydrocarbon groups, a is 1
．． It is said that both ends of the 5-molecular chain are blocked with hydroxyl groups, and the cured product obtained from the composition of the present invention exhibits good rubber elasticity and has excellent mechanical strength. In order to do this, the viscosity at 25°C is 25c.
S or higher is required.

If necessary, this product may be mixed with diorganopolysiloxane whose molecular chain ends are blocked with groups other than hydroxyl groups, such as trimethylsilyl groups; It is preferable that the amount is equal to or less than that of the diorganopolysiloxane.

In addition, the organohydrodiene siloxane (B) component constituting the composition of the present invention is for crosslinking the above-mentioned A) component. This is to generate hydrogen gas by reacting with the hydrogen gas and form a foam using this hydrogen gas. This compound has the same monovalent hydrocarbon group as R described above, preferably an alkyl group having 1 to 6 carbon atoms, and more preferably a methyl group, where b is 0.1 or 2, and C is 1. .2 or 3. b + c is assumed to be 1.2 or 3, but the water 'M atom bonded to the silicon atom in this organohydrodiene siloxane may be at the end of the molecular chain or by a side chain; It may be linear, cyclic, or branched.

The amount of this organohydrodiene siloxane is determined per mole of hydroxyl group in component A).
If the amount of (group) is less than 0.5 mole, the composition will have poor foaming properties, and if it is more than 10 moles, it will not harden into a rubber, and even if it does become a rubber, it will have poor foam regulating properties, and if it becomes a rubber, the composition will have poor foaming properties. Since it is uniform and has weak mechanical properties, it is 0.5~
The amount should be in the range of 10 moles, but the preferred range is 2 to 7 moles.

Next, component C) in the composition of the present invention serves as a catalyst for promoting the dehydrogenation crosslinking reaction between component A) and component B) described above, and is composed of the general formula (R''N), C =
It is represented by N-, and R2 is a silane or siloxane having at least one hydrogen atom or the same monovalent hydrocarbon group as R1 mentioned above in one molecule. This silane or siloxane may have the above group bonded to the silicon atom through any group, but generally it is bonded to the silicon atom through an alkenyl group or an oxyalkylene group. This is often the following formula: % Me I Me Me 2N C=NC,H,SL(O8iMe,).

Me2N M e 2 N Me, N C=NC, HGSiMe.

Me 2N (where Me is a methyl group, Et is an ethyl group, Pr is a propyl group, and pH is a phenyl group) is exemplified, but among these, the formula % is used due to ease of synthesis. It is preferable to use an organosilane represented by the formula (%).

The blending amount of this C) component is 100% of the above-mentioned A) component.
If it is less than 0.01 part by weight, it is too small and the catalyst ability is insufficient and the desired organosiloxane elastomer form cannot be obtained.If it is more than 5 parts by weight, the reaction becomes too fast and workability is impaired. 0.01 as it may make the object look bad and discolor the object, which is also economically disadvantageous.
5 parts by weight is required, with the preferred range being 0.1 to 2 parts by weight.

The composition of the present invention can be obtained by uniformly mixing predetermined amounts of the above-mentioned components A), B), and C),
If necessary, a filler may be mixed therein, and this filler is finely powdered silica.

Silica airgel, precipitated silica, diatomaceous earth, iron oxide,
Metal oxides such as zinc oxide and titanium oxide, or those whose surfaces have been treated with silane, metal carbonates such as calcium carbonate, magnesium carbonate, and zinc carbonate, asbestos, glass wool, carbon black, fine mica powder, fused silica powder, Examples include synthetic resin powders such as polystyrene, polyvinyl chloride, and polypropylene.

In addition, the composition of the present invention obtained in this manner may optionally be added with a thixotropy imparting agent such as polyethylene glycol and its derivatives, a pigment, a dye, an antioxidant, an antioxidant, an antistatic agent, an antimony oxide, and a chloride. It is optional to add flame retardants such as paraffin, thermal conductivity improvers such as boron nitride, aluminum oxide, etc., and these include adhesion imparting agents, amino groups, epoxy groups, thiol groups, etc. Various conventionally known additives such as so-called carbon functional silane and platinum compounds may be mixed.

The composition of the present invention described above is cured into a rubber-like elastic body by the reaction between the hydroxyl group in component A) and the =SiH group in component B) in the presence of component C) when left at room temperature. During the reaction, hydrogen gas is generated by the decomposition of the aS i H group, and this is occluded in the rubber-like elastic body, so the cured rubber-like elastic body obtained here is a closed-cell type that occludes this hydrogen gas. C obtained as a foam but used here
) The ingredients have no odor or corrosivity, giving the advantage that the desired silicone rubber foam can be obtained easily and in a good working environment, and the siloxane will not crack even at high temperatures. A foam with excellent physical properties can be obtained.

The silicone rubber foam obtained in this way has a foaming ratio of 1.5 to 3.5 and has uniform foam regulating properties, so it is lightweight and strong with excellent low-temperature flexibility. It is made of organopolysiloxane and has excellent heat resistance and flame retardancy, so it is useful as a covering material for electronic parts, a shock absorber, a gasket, a penetration sealing material, etc.

Next, examples of the present invention will be given, in which parts are parts by weight and viscosity is measured at 25°C.

Examples 1 to 11, Comparative Examples 1 to 2 Viscosity 5,000 cS with both molecular chain ends blocked with hydroxyl groups
α,ω-dihydroxydimethylpolysiloxane 400
to 200 parts of α,ω-dihydroxydimethylpolysiloxane with a viscosity of 50 cS and an average particle size of 0.0 as a filler.
400 parts of 8m of calcium carbonate were added and mixed uniformly with a stirrer to prepare a base compound (■).

Next, 100 parts of this base compound was added with organohydrodiene siloxane C of the type and amount shown in Table 1.
Component B] and organosilane containing a tetramethylguanidyl group (Component C) were added and mixed uniformly, poured into a cylindrical container made of polypropylene with a bottom area of 20 alf, and heated at 23°C at 50% When left in an RH atmosphere for 24 hours, an organosiloxane foam was obtained, and when the hardness, expansion ratio, and foam regulating properties of this foam were examined, the results shown in Table 1 were obtained.

For comparison, the molar ratio of the E S i H groups in the organohydrodiene siloxane to the hydroxyl groups in the above α,ω-dihydroxydimethylpolysiloxane was set to 0.
．． When a similar test was conducted on the material designated as No. 45.14.06, it did not turn into rubber and a foam could not be obtained in this case.

Examples 12-20, Comparative Examples 3-4 Both ends of the molecular chain are blocked with hydroxyl groups and the viscosity is 20°000
cS α,ω-dihydroxydimethylpolysiloxane 5
00 parts and 300 parts of α,ω-dihydroxydimethylpolysiloxane having a viscosity of 50 cS, 100 parts of dimethylpolysiloxane in which both ends of one molecular chain are blocked with trimethylsilyl groups, and 100 parts of fumed silica as a filler were added, and the mixture was homogenized with a stirrer. A base compound ■ was prepared by mixing the above.

Next, to 100 parts of this base compound were added the organohydrodiene siloxane component CB) and the organosilane or siloxane component CC) containing a tetramethylguanidyl group in the types and amounts shown in Table 2, and the components were uniformly added. When mixed and poured into an 8-base polypropylene cylinder with a base area of 20 cd and left in an atmosphere of 23°C and 60% RH for 24 hours, an organosiloxane foam having physical properties as listed in Table 2 was obtained. Obtained.

For comparison, the molar ratio of the Mi-SiH group in the organohydrodiene siloxane to the hydroxyl group in the above α,ω-dihydroxydimethylpolysiloxane was 0.46.
．． When processed in the same manner as above except that 12.4 was set,
In this case, rubberization did not occur, and the desired foam could not be obtained.

Claims (1)

[Claims] 1. A) 100 parts by weight of a diorganopolysiloxane whose molecular chain ends are blocked with hydroxyl groups, B) General formula▲There are mathematical formulas, chemical formulas, tables, etc.▼ (Here, R^1 is unsubstituted or substituted monovalent hydrocarbon group, b
is 0, 1 or 2, c is 1, 2 or 3, b+c is 1,
2 or 3), an organohydrodiene siloxane in an amount that provides 0.5 to 10 moles of silicon-bonded hydrogen atoms (≡SiH group) per mole of hydroxyl group in the component A), C) General Formula (R^2_2N)_2C=N- (here, R^2 is a hydrogen atom, unsubstituted or substituted 1
At least one group represented by (hydrocarbon group) in one molecule
1. A room-temperature-curable organosiloxane composition for forming a foam, comprising 0.01 to 5 parts by weight of a silane or siloxane.