JPS6366258A - Rubbery substance - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] The present invention relates to curable silicone rubber compositions.

In particular, the present invention relates to self-bonding, enveloped, room temperature vulcanizable (RTV) compositions comprising a diorganosiloxane polymer, a highly functional polysiloxane, a filler, a crosslinking agent, and a crosslinking catalyst. Heat stabilizers may also be included.

N1tzsche and Wick U.S. Pat. No. 30651
94-r7-12- is (1) a linear organosiloxane polymer containing a terminal hydroxyl group, (2) a polyfunctional organosilicone crosslinking agent, and (
3) Essentially anhydrous mixtures of metal salts, thylates, organometallic compounds, acids or bases that act as crosslinking catalysts. Such compositions are particularly useful because they vulcanize or harden to a rubbery solid when exposed to moisture, and can be maintained in a single container for an extended period of time, such as sealed in a caulking tube and ready for use. The user can then apply the material and cure it by contacting with water or steam. Such compositions are useful in sealants, electrical insulation, coatings, dental cements, caulking compounds, expansion joints, gaskets, cushioning materials, adhesives, and many other forms.

Further technical background regarding single-pack room temperature vulcanizable silicone compositions can be found in Brunθr, U.S. Pat. No. 3,035,016 and Oeyzeriat, U.S. Pat. Moisture curable compositions are treated as single packaged compositions which cure with the release of acid and which curing is facilitated by various agents such as organic derivatives of tin. Also of interest is U.S. Patent No. 51 for Br0Wh et al.
No. 61614, in which a silanol-terminated diorganopolysiloxane and a crosslinking agent are reacted in advance and a crosslinking catalyst is combined with the r,co
U.S. Pat. No. 3,383,355 to Oper deals with the preparation of alkoxy-terminated linear siloxane polymers using neutral finely divided solid catalysts such as Fuller's earth, and U.S. Pat. Using an end-capped diorganopolysiloxane and a metal-containing curing catalyst with boron nitride, Coo
U.S. Pat. No. 3,542,901 to Per et al. discloses a linear siloxane having a di- or trifunctional end-capping unit and a chemically non-functional, inert end-capping unit at one end and a di- or trifunctional end-capping unit at the other end. A mixture of seven linear siloxanes with terminal end-capping units is used and includes a catalyst and a crosslinking agent. Also related is U.S. Pat. No. 31,225 to Br0Wh et al.
No. 22, in which an organopolysiloxane intermediate alloyed with condensable cellosorboxylic groups is combined with a catalyst, and U.S. Pat. In US Pat. No. 6,175,993 to Weye-Berg, an organopolysiloxane intermediate end-capped with an alkoxylated silicon carbon group is combined with a catalyst. S
mlth and Hamilton U.S. Patent No. 5689
No. 454 and No. 5779986, Weyenberg
U.S. Pat. No. 3,294,739 and No. 5,354,067, and U.S. Pat. No. 5,719,655 to 01ark et al. also disclose single-pack compositions.

Also relevant is U.S. Pat. No. 5,382,205, in which the packaging system disclosed is moisture curable and further includes mono-, di- and trialkyl polysiloxanes, the latter fluid being an adhesion promoter and processing aid. It is functioning as.

Special types of compositions are known that provide high temperature resistance to sealants, but these have limited use as gasket materials in the automotive industry where odor and corrosion pose problems. be.

For example, compositions containing silanol-terminated polydimethylsiloxane, methyltriacetoxysilane, fumed silica fillers, and dibutyltin dilaurate are currently used in most applications, but they release acetic acid upon curing, making them completely unsuitable in some applications. I'm not satisfied with anything.

This curing by-product causes the unpleasant odor and corrosion mentioned above.

Currently used compositions also tend to have a relatively high degree of adhesion at low temperatures, making them ideal for use in oil pans, for example, even when dismantling new car engines before they are put into service. It is difficult to repair without damaging things like the valve cover.

It has now become possible to provide a low-corrosive, fast-curing, one-component RTV composition that exhibits excellent oil resistance after moisture curing and, in particular, exhibits high-temperature resistance properties with heat stabilizers. The composition also has low adhesion at room temperature and improved adhesion at elevated temperatures, which provides a good seal, such as when an automobile engine equipped with a gasket made from the composition of the invention is started. It can be achieved. The compositions are useful in a variety of conventional applications, particularly as gasket layers between components having metal surfaces.

The fluid compositions provided by the present invention are stable under substantially anhydrous conditions and harden in the presence of moisture to form a self-bonding, heat-stable, elastic material resistant to hot hydrocarbon oils. (a) (wherein P and R1 are each individually hydrocarbyl,
An organic group with 8 carbon atoms selected from halohydrocarbyl and lower alkyl cyanide, where n is about 10 to 15
100 parts by weight of a silanol chain-terminated polydiorganosiloxane having an average number of
i) 25 to 60 mol% of monoalkylsiloxy units, siloxy units, or mixtures thereof, (ii) 1 to 6 mol% of realkylsiloxy units, and (lii) 34 to 74 mol% of dialkylsiloxy units, with silicon bonds. Fluid polysiloxane 2-2 containing about 0.1-2% by weight of water-waxing groups
0 parts by weight, (C) finely divided silica filler 10~
100 parts by weight, (d) formula % formula %) (wherein R has the same meaning as defined from R and R1 above, and R3 is the number of carbon atoms selected from hydrocarboyl and) 10 hydrocarboyl 3 to 10 parts by weight of a crosslinking silane represented by (6 to 30 organic groups, m having a value of 0 or 1), and (e) an organic tin salt of an organic acid having 2 to 3 carbon atoms; Curing catalyst which is tin salt 0.01
~10 parts by weight.

In a preferred aspect of the invention, the composition also includes (f) from 1 to 10 parts by weight of a finely divided iron oxide thermal stabilizer. These embodiments are particularly useful at operating temperatures of 140°C and above.

According to another preferred aspect of the invention, there is provided a method for preparing a rubbery material, which method comprises preparing a composition as defined above under substantially anhydrous threading; It consists of exposing something to moisture until it hardens into a rubbery substance. According to another aspect of the invention, at least a portion of the surface of each of the first few pieces having a metal surface is brought into close proximity to another surface, and a gasket layer of the composition as defined above is interposed therebetween. An article of manufacture is provided, as well as a method of making such a gasketed article of manufacture. In preferred embodiments of this aspect, the composition also includes an iron oxide thermal stabilizer.

To prepare the room temperature vulcanizable (RTV) compositions of the present invention, one or more of the silanol chain-terminated polyorganosiloxanes of the above formula, iron oxide, a silica filler, a crosslinked silane compound, and a silanol-reactive tin salt are used. Mix in your fist. The base compound (excluding crosslinkers, adhesion promoters and catalysts if present) is usually compounded at elevated temperatures to remove moisture and facilitate wetting of the filler. Since silanes tend to hydrolyze when in contact with moisture, care is taken to exclude moisture during the addition of silanes to silanol chain-terminated polydiorganoborisiloxanes. Similarly, mixtures of silanes, silanol-reactive tin salt catalysts, silanol chain-terminated polydiorganosiloxanes, and highly functional siloxane fluids may be stored for extended periods of time prior to conversion to a cured, solid, elastomeric silicone rubber state. Care should be taken to maintain substantially anhydrous conditions. On the other hand, when it is desired to cure the mixture immediately, it is sufficient to mix and leave the mixture in the shape to be cured, and there is no need to take particular precautions in advance.

As long as the ratios of ingredients specified above are used, a wide range of ingredient selection is possible in preparing the compositions of the present invention. These can be found in many documents such as US Pat. No. 3,779,986,
No. 3065194, No. 2294739, No. 3334
No. 067, No. 3382205, and No. 3708467
listed in the number.

Silanol chain-terminated polyorganosiloxane component (a)
is the formula (wherein R and R1 have 2 carbon atoms selected from hydrocarbyl, halohydrocarbyl, and cyano-lower alkyl)
Up to 0 and preferably up to 8 organic groups, where n is generally a number from about 10 to 15,000, preferably from 100 to about 5,000, more preferably from 300 to 1,500.

Silanol chain-stopped polydiorganosiloxanes are well known in the art and include compositions containing a variety of R and subgroups. For example, the R group may be methyl (the Bl group may be phenyl and/or betacyanoethyl). Additionally, within the definition of polydiorganosiloxane useful in this invention are various types of diorganosiloxane units: polymer,
For example, silanol-linked and terminated copolymers comprising dimethylsiloxane units, diphenylsiloxane units, and methylphenylsiloxane units, or copolymers comprising, for example, dimethylsiloxane units, methylphenylsiloxane units, and methylvinylsiloxane units are included. Preferably, at least 50% of the R and R1 groups of the silanol chain-terminated polydiorganosiloxane are alkyl groups, such as methyl groups.

In the above formula, R and R may be any of the groups exemplified in the above patents, for example.

The silanol chain-terminated polydiorganosiloxanes used in the practice of this invention can range from low viscosity, low viscosity fluids to viscous gums depending on the value of n and the nature of the particular organic groups represented by R and RIK. .

The viscosity of component (a) is, for example, 50 to 10,000 at 25°C.
．． It may vary widely over a range of 000 cps.

Preferably, 1. ODD~200,000ap
e range, most preferably about 2,000 to 30
,000 cps.

The highly functional polysiloxane component (b) is (1)+
A mixture of -yl alkyl chlorosilane, CII) dialkyldichlorosilane and (lii) alkyl trichlorosilane, silicon tetrachloride or a mixture thereof in an appropriate molar ratio is placed in toluene and water and these are simultaneously subjected to hydrolysis. . The mixture is then heated to, eg, about 60° C., for a sufficient time, eg, 3 hours, to ensure completion of the reaction. Separate the oil phase and then carbonate or bicarbonate) +
Neutralize by washing with an aqueous solution of Jum. Filter to remove insoluble matter, e.g.
When devolatilized by heating to 40° C., component (b) remains as a residue. For economic reasons, the silicon-bonded hydroxyl content is maintained below 0.6% by weight to minimize the viscosity of the final composition and to maintain a minimum concentration of crosslinking agent.

1% of the product in the presence of about 1%
This is done by heating to 10°C. The water resulting from the silanol condensation can be conveniently removed, for example, by azeotropic distillation with toluene. After removing toluene by distillation,
The product is filtered prior to use. US Pat. No. 3,382,205 to Beers illustrates this. Component (b) generally comprises from 2 to 20 parts by weight per 100 parts of component (a) and preferably from about 5 to 15 parts by weight per 100 parts by weight of the composition.

Preferably, component (b) has a temperature of 50 to 300 Qp8 at 25°C.
It has a viscosity in the range of . Also, preferably component (1))
At least 50% of the alkyl substituents are methyl and the fluid contains 0.2-0.6% by weight of silanol.
included. Particularly preferably, the monoalkylsiloxy units, siloxy units or hybrid units of such units are about 35 to
It accounts for 45 mol% and contains 3 to 5 trialkylsiloxy units.
dialkylsiloxy units account for 45-67 mol%, and the silanol content is about 0.2-0.
It is 5% by weight.

Silica component (C) is known in the art as a filler for silicone compositions. Component (C) is in finely divided form and is preferably of the type known as fumed silica. Preferably the surface area should be about 200 square meters/f. Preferred forms include LuQae US Pat. No. 2,958,009, Liah
U.S. Pat. No. 500,485 to Ten and Walter
9 and Sm1th, US Pat. No. 3,635,743. Silica filler (c) is component (a) 100
Generally used in amounts of 10 to 100 parts by weight, preferably 15 to about 40 parts by weight, preferably 20 to 30 parts by weight per 100 parts by weight of the composition.

In the silane crosslinking agent (d) of the formula % formula %), the meaning of - is the same as defined for R and Fl individually above, and P is a corrosive substance with an odor during the curing reaction. The number of carbon atoms should be between 6 and 3o to eliminate the formation of by-products.

C 5t (oc+o(cH2)4c 3Si)3Si(Of:
! 0(CE[2)40BI)4C几(OH2)60H2
5i (000 (OB 2 people C) 3073 (O-) * 8
1 (000 (OH2) 40 speed) 3 NaC speed C horse 51 (o
co(c sp)40 sp)3CjIlr3Bi(OOOOOH
(OzEs)C(jk)011J*Cfal(oc Kano○
)3 These silanes are well known in the machinery industry, and are used, for example, in Beer.
No. 3,382,205.

For the crosslinking agent (eL), m preferably has a value of 1, and preferred silanes are methyltris(2-ethylhexanoxy)silane and methyltris(benzoxy)silane. The silane is generally used in an amount of 3 to 10 parts by weight, preferably 5 to 7 parts by weight per 100 parts by weight of component (a).

As for the silanol-reactive tin catalyst component (θ), generally any organic tin salt or tin salt of an organic acid can be used, but the former is preferred. A carbon content of 2 to 6 in the organic acid provides the best combination of cure speed and final properties. The organic content of the organotin salt has, for example, 2 to 6 carbon atoms.
or two alkyl groups, for example monobutyl or dipyl, and the organic acid group can have a number of carbon atoms of 2 to 6. Examples of these are tin hexanoate, dibutyltin hexanoate, diptytin diacetate, dibutyltin adipate, diptytin diglobionate, diptytin dibutyrate, motuptyltin triacetate, and the like. These are commercially available or can be manufactured by those skilled in the art. Preferred is dibutyltin diacetate.

The catalyst is generally 0.0 parts by weight of component (a).
It is present in an amount of 1 to 10.0 parts by weight, preferably 0.02 to 5.0 parts by weight. It is particularly preferred that the catalyst be used in an amount of about 0.05 to about 0.15 parts by weight per 100 parts by weight of the total composition.

The optional iron oxide thermal stabilizer component (f) is a conventionally used and widely available commercial product in finely divided form for use as a filler in plastic compositions.

It is preferred that the pH of the iron oxide be in the range 6.0 to 7.5 to achieve maximum thermal stability and storage aging stability.

The amount used is 1 o of component (a).

It ranges from 1 to 10 parts by weight, preferably from 3 to 6 parts by weight, based on 100 parts by weight of the total composition.

In a preferred embodiment, the compositions of the invention also optionally contain an adhesion promoter at a concentration of 0.000 parts per 100 parts of component (a).
2 to 2 parts may be included. These are generally nitrogen-containing compounds, such as a group of accelerators of the formula, where G is
M is a divalent group selected from alkylenearylene, alkylene, cycloxyene, and such divalent groups substituted with NOA; RlO is a group having up to 8 carbon atoms selected from hydrocarbyl or halohydrocarbyl;
is a radical of the type defined for BIG and is cyano-lower alkyl and 5b is 0-3.

These adhesion promoters are covered by Berger's US patent! 3
No. 517001. Preferred such promoters are 1,5,5-) lis-trimethoxysilylpropylisocyanate and bis-1,3-trimethoxysilylpropylisocyanurate, of which the former is most preferred.

Although any conventional adhesion promoter can be used, particular mention is made of the adhesion promoter known as glycidoxyprobyltrimethoxysilane.

Additional conventional ingredients such as flame retardants, stabilizers, pigments, etc. may also be included.

The compositions of the invention are stable in the absence of moisture. As a result, the composition can be stored for extended periods of time without being affected by harmful forces. During this storage time, do any noticeable changes occur in the physical properties of the room temperature vulcanizable composition? This is particularly advantageous commercially, as compositions can be prepared to have a given consistency and setting time without significantly altering either the consistency or the setting time during storage. Storage stability is one of the characteristics that makes the compositions of the present invention useful in a packaged system.

Compositions prepared by mixing the catalyst and silane with the silanol chain-terminated polydiorganosiloxane and other ingredients under anhydrous conditions may be further modified by simply placing the composition at the desired location and exposing it to air. It can be used in many sealing, caulking, and sealing applications by exposure to moisture present and curing. Such exposure results in the formation of a crust on the compositions of the invention within a relatively short period of time, e.g. 10 minutes to about 8 hours, even after previous storage for many months, and at room temperature e.g. 18-25°C. It will harden to a rubbery state within a few hours to a few days.

When the compositions of the present invention include tri- and/or tetrafunctional siloxane fluids, silane crosslinkers, and tin catalysts as components other than the silanol-terminated polydiorganosiloxane, these additional components can be added in any desired manner. . However, for ease of manufacture, it is often most convenient to form a base formulation of all ingredients other than the silane, tin catalyst, and adhesion promoter, if present, and then to form this base formulation. For example, 50 to 100 to remove moisture from
The silane, tin catalyst and optional adhesion promoter are then added just prior to packaging in a container protected from moisture.

The compositions of the present invention are particularly suited for caulking and sealing applications where excellent adhesion to a variety of substrates is important. For example, it is useful in domestic and industrial caulking and sealing in buildings, factories, automobiles, etc., where the substrate is, for example, masonry, glass, plastic, metal, wood, etc.

The compositions of the present invention have little or no tendency to corrode sensitive substrates such as metals such as copper and brass. The composition has an excellent application speed and is easily adapted to be applied with conventional caulking tools under standard conditions.

The following examples are illustrative only and should not be construed as limiting the invention. The terms M, D, T and Q are art-recognized designations, respectively, where M = jl functional organosiloxa 7 units? 3]) &S10UD = difunctional organosiloxane unit Rz8102/2 T = king-functional organosiloxane unit R8103/2 Q = tetrafunctional organosiloxane unit 5i04/2 Example 1 A base containing the following components: Prepare the compound (
Iron oxide at pH 6, Q ~ 7.5 (parts by weight).

Methyltris-2-ethylhexanoxysilane; cross-bridged 6 dibutyltin diacetate 0.06 100 parts of the base compound were mixed with the catalyst mixture in the absence of air and atmospheric moisture and packaged in a 3 oz. metal container. Enter. A test sheet was then prepared at a temperature of 77±2 below, 5
Cure for 3 days at 0±5% relative humidity. The following test results are obtained.

Shore A hardness 42 Tensile strength psi 500 Elongation % 380 Comparative Example A A base compound is prepared containing the following ingredients (parts by weight):

Iron oxide A catalyst mixture is prepared comprising up to 6 components (parts by weight).

Methyltris(2-ethylhexoxy)silane Dibutyltin 6 diacetate (catalyst) 0.06 Base compound 100 in the absence of air and atmospheric moisture
parts with the catalyst mixture. This anhydrous material is cured and tested as in Example 1. Obtain the following test results.

Shore A Hardness 43 Tensile Strength psi 630 Elongation % 370 The hardened specimens of Example 1 and Comparative Example A were suspended in 300 below 5W-50 motor oil for various times to determine their relative resistance to hot hydrocarbon oil. 1 Hardness, tensile strength, elongation and volume swelling were measured. The results are shown in the table below.

Oil immersion resistance characteristics for 72 hours Example 1 Comparative example A Shore A Hardness 16 18 Tensile
psi 100 140 elongation %
300 320 Volume swelling %
37 42168 hours Example 1 Comparative Example A Shore A Hardness 19 18 Tensile
psi 190 190 elongation %
520 520 Volume swelling %
57 43336 hours Example 1 Comparative Example A Shore A Hardness 17 12 Tensile
psi 200 70 elongation %
3!10 240 Volume swelling %
36 4°504 hours Example 1 Comparative Example A Shore A Hardness 17 9 Tensile
1) 81 175 40 elongation %
300 250 Volume swelling %
36 40 The composition of Example 1 is more resistant to reversion than the composition of Comparative Example. This illustrates the advantages of the high functionality (T-containing) component of the compositions of the present invention.

Example 2 The procedure of Example 1 is repeated using 1.3.5-tris-trimethoxysilylpropyl isocyanurate over the adhesion promoter. The properties of the cured product were as follows.

Shore A Hardness 46 Tensile strength 9 days 1 620 Elongation % 40 Other modifications are also possible. For example, iron oxide thermal stabilizers can be omitted. Instead of methyltris(2-ethylhexoxy)silane, methyltris(benzoxy)silane can be used as a crosslinking agent. However, instead of the M, D, and T fluids used in Example 1, M, D, and T fluids having substantially lower T concentrations were used.
If T-fluid is used, the oil resistance will be poor.

Comparative Example B A basic compound with the following composition was prepared pH 6,0-
6 parts of 7,5 iron oxide The same catalyst mixture as used in Example 1 was introduced into the base compound described above in exactly the same percentage composition in the absence of moisture.

The following room temperature test results were obtained.

Shore A Hardness 35 Tensile psi 600 Elongation % 420 To determine relative resistance to hot hydrocarbon oil, hardened blocks were suspended in 5W-30 oil at 300°C. After 72 hours of equipment under these environmental conditions, the hardness, tensile strength,
Elongation and volumetric swelling were measured. The tensile strength was low and the test was discontinued. The data presented below clearly demonstrate the benefits of the high T content oil used in Example 1. The results are shown below.

Shore A Hardness 9 Tensile Strength pθ1 40 Elongation % 240 Swelling % 66 in 5W-30 for 72 hours at 300° C. Distributing a coating of the composition of Example 1 on the surface of the first piece;
a surface of the second piece is brought into close proximity to the surface of the first piece to form a young German bridge with a composition between the pieces to form a gasket between the two corrosion-susceptible metal workpieces; . This structure is exposed to a humid atmosphere of about 75°C until a strong bond is formed and the composition cures to a rubbery state without releasing any substantial amounts of corrosive or odorous substances. .

Other modifications and variations of the present invention are possible in light of the above teachings. It is therefore understood that changes may be made to the specific embodiments of the invention without departing from the scope of the invention.

Claims (1)

[Claims] 1. Formula (a) ▲ Numerical formulas, chemical formulas, tables, etc. n is an organic group up to about 10 to 15,00
100 parts by weight of a silanol chain-terminated polydiorganosiloxane (with an average number of 0), (b) highly trifunctional, tetrafunctional, or mixtures thereof; A mixture of 25~
60 mol%, (ii) 1 to 6 trialkylsiloxy units
mol% and (iii) dialkylsiloxy units 34-7
4 mole percent of silicon-bonded hydroxyl groups from about 0.1 to about 2
2 to 20 parts by weight of a fluid polysiloxane containing % by weight;
(c) 10-100 parts by weight of finely divided silica filler, (d) formula R^2_mSi(OR^3)_4_-_m, where R^2 is defined from R and R^1 above. having the same meaning, R^3 is an organic group having 6 to 30 carbon atoms selected from hydrocarboyl and halohydrocarboyl, and m has a value of 0 or 1). Substantially anhydrous conditions comprising 3 to 10 parts by weight of a certain silane and (e) 0.01 to 10 parts by weight of a curing catalyst consisting of an organotin or tin salt of an organic acid having 2 to 6 carbon atoms. A fluid composition is prepared under substantially anhydrous conditions that is stable and cures in the presence of moisture to a self-bonding, thermally stable, elastic solid that is resistant to hot hydrocarbon oils and then A method for preparing a rubbery material comprising exposing the composition to moisture until it hardens into a rubbery material. 2. The method according to claim 1, wherein the composition further contains 1 to 10 parts by weight of a finely divided iron oxide thermal stabilizer as component (f). 3. Formula (a) ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, R and R^1 are each an organic group with up to 8 carbon atoms selected from hydrocarbyl, halohydrocarbyl, and cyano lower alkyl. , n is approximately 10-15,00
100 parts by weight of a silanol chain-terminated polydiorganosiloxane (with an average number of 0), (b) highly trifunctional, tetrafunctional, or mixtures thereof; A mixture of 25~
60 mol%, (ii) 1 to 6 trialkylsiloxy units
mol% and (iii) dialkylsiloxy units 34-7
4 mole percent of silicon-bonded hydroxyl groups from about 0.1 to about 2
2 to 20 parts by weight of a fluid polysiloxane containing % by weight;
(c) 10-100 parts by weight of finely divided silica filler, (d) formula R^2_mSi(OR^3)_4_-_m, where R^2 is defined from R and R^1 above. having the same meaning, R^3 is an organic group having 6 to 30 carbon atoms selected from hydrocarboyl and halohydrocarboyl, and m has a value of 0 or 1). A highly thermally stable rubber comprising 3 to 10 parts by weight of a certain silane and (e) 0.01 to 10 parts by weight of a curing catalyst consisting of an organic tin salt or a tin salt of an organic acid having 2 to 6 carbon atoms. Manufacture of a plurality of metal-faced strips in which a gasket layer of a moisture-cured composition of high quality is inserted between at least some of the surface portions of each strip and in close proximity to other surface portions. Goods. 4. Finely divided iron oxide thermal stabilizer 1-1 in the composition
4. The article of manufacture of claim 3, further comprising 0 parts by weight. 5. (i) preparing a piece with a plurality of metal surfaces; (ii)
applying a layer of a moisture-curable gasket-forming composition to at least a portion of at least one of the metal surfaces; (iii)
(i
v) step (i) until the gasket layer hardens into a rubbery material;
ii) A method for manufacturing an article comprising the step of exposing the article to moisture, wherein the moisture-curable gasket composition is (
a) Formulas ▲ Numerical formulas, chemical formulas, tables, etc. Approximately 10-15,00
100 parts by weight of a silanol chain-terminated polydiorganosiloxane (with an average number of 0), (b) highly trifunctional, tetrafunctional, or mixtures thereof; A mixture of 25~
60 mol%, (ii) 1 to 6 trialkylsiloxy units
mol% and (iii) dialkylsiloxy units 34-7
4 mole percent of silicon-bonded hydroxyl groups from about 0.1 to about 2
2 to 20 parts by weight of a fluid polysiloxane containing % by weight;
(c) 10-100 parts by weight of finely divided silica filler, (d) formula R^2_mSi(OR^3)_4_-_m, where R^2 is defined from R and R^1 above. having the same meaning, R^3 is an organic group having 6 to 30 carbon atoms selected from hydrocarboyl and halohydrocarboyl, and m has a value of 0 or 1). A method for producing an article as described above, comprising 3 to 10 parts by weight of a certain silane, and (e) 0.01 to 10 parts by weight of a curing catalyst consisting of an organotin or tin salt of a fatty acid having 2 to 6 carbon atoms. 6. Also included in the composition is a finely divided iron oxide thermal stabilizer 1
6. The method of claim 5, wherein up to 10 parts by weight are included.