KR940011191B1 - Method of producing a silicone water-based elastomeric foam - Google Patents

Abstract

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Description

Method for producing silicone water-based elastic foam

The present invention relates to a process for preparing a silicone aqueous emulsion. The emulsion can be cured to an elastomer by removing the components at room temperature immediately after mixing.

Nelson's Canadian Patent No. 862,183, issued January 26, 1971, teaches a method of treating silicone emulsions and glass fibers. The aqueous dispersion in this patent is essentially a liquid hydroxyl endblocked dimethylsiloxane polymer, the general formula RnSiR ' _4-n , wherein R is a hydrocarbon or substituted hydrocarbon radical, and R' is hydrolyzable except for halogen atoms. Radicals, n is 0 or 1) and a silane and siloxane condensation catalyst.

Berridge, US Pat. No. 2,843,555, issued July 15, 1958, teaches compositions of metal salts of hydroxyl terminated polydiorganosiloxanes, alkyl silicates and organic carboxylic acids. Hydrolyzable or hydrolyzable alkyl silicates are represented by the following general formula:

Wherein R 'may be OR. After mixing, the product begins to cure immediately and fully cures within 1 to 2 hours.

US Patent No. 3,355,406 to Cekada, issued November 28, 1967, teaches silicone rubber latex reinforced with silsesquioxane. In Example 18 of this patent, hydroxyl-terminated polydimethylsiloxane polymers, phenylsilsesquioxanes, ethyl orthosilicates, and dibutyltindilaurate are described. It is said that depositing this latex on a surface forms a fairly strong silicone rubber film. It is also mentioned that the present invention provides a stable latex upon storage.

Huebner and Meadowd, US Pat. No. 3,706,695, issued December 19, 1972, teaches a method for preparing an emulsion that provides a thermally stable conductive silicone rubber when water is removed. According to this method, hydroxyl-terminated foryldiorganosiloxanes or polydiorganocyclosiloxanes are emulsified and polymerized, followed by addition of carbon black, metal salts of carboxylic acids, and silanes of the general formula RSi (OR ') ₃ . The emulsion is maintained as a two-package system for long term storage.

Fujiki's Japanese Patent Laid-Open Publication No. 53-130752, published November 15, 1978, contains 100 parts by weight of hydroxyl-terminated polydiorganosiloxane, at least three silicon-bonded valences per molecule. Aqueous emulsions comprising 0.5 to 30 parts by weight of silane containing a decomposable group, a curing catalyst, an emulsifier, and water are taught. This composition is taught to have excellent storage stability at room temperature and to have properties that can be converted to an elastomer when dried at room temperature. Examples of curing catalysts are metal salts of organic acids such as tin salts. However, this document does not teach the use of fillers.

US Pat. No. 4,221,688 to Johnson et al., Issued September 9, 1980, discloses a pH 9 having a dispersed phase of anionically stabilized hydroxylated polydiorganosiloxane and colloidal silica and a continuous phase of water. To 11.5 silicone emulsions are taught. The emulsion is stored for a period of time (five months) before the water is removed, and then the water is removed at ambient conditions to form an elastic product. Adding organotin compounds reduces the required shelf life to several days. However, compositions such as Johnson do not form an elastomer when water is removed immediately after mixing the components.

Sam U.S. Patent No. 4,244,849, issued January 31, 1981, teaches an aqueous silicone emulsion that provides an elastic product after removal of water. Emulsions taught in this patent include an anionic stabilized dispersed silicone phase which is a graft copolymer of a continuous aqueous phase and hydroxyl endblocked polydiorganosiloxane and an alkali metal silicate. Organic tin compounds can be used to accelerate the formation of graft copolymers. The Sam system does not use colloidal silica as an essential ingredient.

In laboratory tests, silanes with three hydrolyzable groups are used in compositions containing liquid hydroxyl terminated polydimethylsiloxanes, fillers, and dibutyltindilaurate catalysts, which are used immediately after preparation of the mixture. Even when dried, it did not cure when water was removed. Similar mixtures did not cure when the silane used was a partially hydrolyzed silane such as ethylpolysilicate.

Bengtson, US Patent No. 3,830,760, issued August 20, 1984, features the formation of a mixture of a polymer or polymer precursor that can be cured upon contact with the atmosphere and a polymer soluble inert blowing agent under pressure. A method for producing a foamable composition is described. The wide range of polymers described in this patent include silicones. Examples of this patent show polyurethanes that are mixed and then transferred to an aerosol container. Independent foam foams are prepared by dispersing the components from the vessel to obtain foam and then curing by exposure to the atmosphere.

United States Patent Application No. 665,224, filed by Gravier and Kalinowski on October 26, 1984, and assigned to the same assignee as the present application, disperses the air throughout the emulsion and then removes the water. The use of fibers in silicone emulsions for stabilizing the foam formed by obtaining bubble foams is described.

US Patent Application No. 665,233, filed on October 26, 1984 by Bauman, Lee, and Rabe to the same assignee as the present application, discloses a silicone emulsion and aerosol propellant under excess atmospheric pressure. , And compositions comprising any lauryl alcohol and any fibers are described. When released to atmospheric pressure at 25 [deg.] C., upon removal of water, bubbles are formed which form the elastic foam of the continuous bubbles.

The method provides a method for producing a silicone elastomer. Combining the components results in an emulsion, which can be used to immediately form a coating on a substrate or as a caulking material that hardens into an elastomer upon removal of water. In the process, (A) anionically stabilized hydroxyl terminated polydiorganosiloxane, (B) dialkyltindicarboxylate, (C) present as an emulsion of particles dispersed in water (pH 9 or higher) Alkylorthosilicates of the general formula Si (OR ′) ₄ , wherein R ′ is a lower alkyl radical having 1 to 4 carbon atoms, (D) colloidal silica and optionally (E) additional water and (F) fibers and Combine lauryl alcohol. This emulsion contains a sufficient amount of components, ie 100 parts by weight of component (A), 0.1 to 2.0 parts by weight of component (B), 1 to 10 parts by weight of component (C), 0 to 100 parts by weight of component (D), optional ingredients (E), and optionally 1 to 10 parts by weight of fiber (F) or 0.2 to 1.5 parts by weight of lauryl alcohol (F) such that components (A) and (B) are mixed only when component (C) is present It is prepared by mixing under conditions.

The emulsions of the present invention have an extended shelf life because the ingredients are combined just prior to use. They are stored in two-part emulsions and are convenient to combine before use. The emulsion formed by mixing the two parts can be used immediately after mixing. The reaction time before mixing is not critical, but is essential in some systems. For example, emulsions of anionically stabilized hydroxylated polydiorganosiloxanes and colloidal silica can be aged for several days before the emulsion produces a cured elastomer upon water removal, even in the presence of organotin compounds. need.

In case the process of the invention comprises any step of adding microfibers or lauryl alcohol, or mixtures thereof, the mixture is mixed and immediately followed by a two-part emulsion which can foam up mechanically or by aerosol means. Can be stored as By removing water from the foam, a continuous bubble, elastic foam is produced.

(A) 2- (perfluoroalkyl) having a weight average molecular weight of 50,000 or more and an organic radical having less than 7 carbon atoms per radical or a monovalent carbon atom radical having less than 7 carbon atoms per radical 100 parts by weight of an anionically stabilized, hydroxyl terminated polydiorganosiloxane, which is an ethyl radical and is present as an emulsion of dispersed particles in water having a pH of at least 9; (B) 0.1 to 2.0 parts by weight of dialkyl tin dicarboxylate; (C) 1 to 10 parts by weight of alkylorthosilicate of formula Si (OR ′) ₄ , wherein R ′ is a lower alkyl radical having 1 to 4 carbon atoms; (D) 0 to 100 parts by weight of colloidal silica, and optionally (E) additional water and (F) a ratio of length to diameter of at least 10: 1, having a diameter of 1 to 10 μm and a length of 30 μm to 10 mm The components comprising 1 to 10 parts by weight of fiber or 0.2 to 1.5 parts by weight of lauryl alcohol, or mixtures thereof are mixed under conditions such that (A) and (B) are mixed only when (C) is present, Preparing an emulsion of dispersed components in water that can be used immediately without maturation; And then removing the water to obtain the silicone elastomer, thereby providing a method for producing the silicone elastomer.

Conventional methods for preparing aqueous silicone emulsions that, when dried, produce elastomers include anionically stabilized hydroxylated polydiorganosiloxanes and colloidal silica. This emulsion must be aged, for example, for 5 months after the emulsion has dried before the elastomer is formed. If this emulsion also contains an organotin compound as a catalyst, the aging period is shortened by several days, for example three days or more. The properties of the elastomer formed by drying are also a function of the emulsion age. As the emulsion ages, in particular its elongation falls. The variability of the elongation of the elastomer due to the age of the emulsion in use prohibits the use of the emulsion in applications requiring a particular elongation.

The two-part emulsions prepared by the process of the present invention do not undergo a change in properties upon storage aging. This emulsion can be formulated to yield an elastomer having a given range of properties. The two parts can then be stored mature without any effect. If the two parts are mixed together and the emulsion dried, the resulting elastomer will have the physical properties in which it is formulated. An additional benefit is the ability of the emulsion to be used immediately after mixing, without having to wait. The mixed emulsion has a pot life of several days after mixing before exhibiting a change in properties. The emulsion will then have a somewhat increased viscosity compared to its viscosity just after mixing.

It also describes a method for producing a silicone continuous bubble, an elastic foam from a two-part emulsion. This method essentially consists of (1) mixing the I and II parts to produce an emulsion of the components dispersed in water, (2) immediately forming a foam of the mixture, and (3) immediately removing the water from the foam. To obtain a foam. In this embodiment, the first part consists essentially of (A) 100 parts by weight, (D) 1 to 10 parts by weight and (F) a ratio of length to diameter of at least 10: 1, with a diameter of 1 to 10 μm and a length 1 to 10 parts by weight of fiber having a thickness of 30 μm to 10 mm or 0.2 to 1.5 parts by weight of lauryl alcohol, or a mixture thereof. The second part consists essentially of (B) 0.1 to 2.0 parts by weight, (C) 1 to 10 parts by weight, and (D) 15 to 35 parts by weight.

Anionically stabilized, hydroxyl terminated polydiorganosiloxane emulsions used in the present invention are known materials. This hydroxyl terminated polydiorganosiloxane (A) can be emulsified and is an anionically stabilized polymer that gives elasticity to the product obtained after removing water from the emulsion. Tensile strength and elongation at break improve as the weight average molecular weight (Mw) increases, and appropriate tensile strength and elongation at break are obtained at 50,000 Mw or more. Those of the maximum weight average molecular weight can be emulsified and will give elasticity to the product obtained after removing water from the emulsion. Those having a weight average molecular weight of about 1,000,000 or less relative to the hydroxyl terminated polydiorganosiloxane are used in the present invention. Preferred Mw of the hydroxyl terminated polydiorganosiloxane is in the range of 200,000 to 700,000.

The organic radicals of hydroxyl terminated polydiorganosiloxanes are monovalent carbon atom radicals containing less than 7 carbon atoms per radical, and 3,3,3-trifluoropropyl and 2- (perfluorobutyl) 2- (perfluoroalkyl) ethyl radical, including ethyl. This hydroxyl terminated polydiorganosiloxane contains preferably organic radicals in which at least 50% is methyl. The hydroxyl terminated polydiorganosiloxane is a nearly linear polymer containing two organic groups per silicon atom and may contain trace amounts of monoorganosiloxane or triorganooxyoxy units present as impurities in the manufacturing process. have. Preferred are hydroxyl terminated polydimethyl-siloxanes of hydroxyl terminated polydiorganosiloxanes.

Preferred anionically stabilized, hydroxyl-terminated polydiorganosiloxanes are prepared by the anionic emulsion polymerization process described in US Pat. No. 3,294,725 to Findlay et al., Issued 12 December 27, 1966. This patent describes the polymerization process, the components used, and the hydroxyl terminated polydiorganosiloxanes obtained in the emulsion. Another method for preparing anionically stabilized, hydroxyl-terminated polydiorganosiloxanes is described in US Pat. No. 2,891,920 to Hyde et al., Issued June 23, 1959, which is incorporated herein by reference. Also described are hydroxyl terminated polydiorganosiloxanes, the components used, and methods for their preparation. These methods and others are known in the art. The hydroxyl terminated polydiorganosiloxanes used in the present invention are those that are anionic stabilized. For the purposes of the present invention, "anionic stabilized" means that the hydroxyl terminated polydiorganosiloxane is stabilized by an anionic surfactant in the emulsion. This silicone emulsion is in the form of an oil-in-water emulsion, ie the polydiorganosiloxane is present in the dispersed phase of the particles in the water of the continuous phase.

Component (B) is dialkyl tin dicarboxylate. This dialkyl tin dicarboxylate is a commercial item. Preferred dialkyltindicarboxylates include dibutyltindiacetate, dibutyltindilaurate, and dioctyltindilaurate, with dibutyltindilaurate being most preferred. Dialkyltindicarboxylates can be used on their own or made into an emulsion. Suitable emulsions are known methods of preparing oil-in-water emulsions, which are prepared by emulsifying 50% by weight of dialkintindicarboxylate with water using about 10% by weight sodium alkylarylpolyether sulfonate as emulsifier.

Component (C) is alkylorthosilicate. Alkyl orthosilicates of general formula Si (OR ') ₄ are commercially available products. R 'is a lower alkyl radical having 1 to 4 carbon atoms (eg, methyl, ethyl, propyl, isopropyl and butyl). Preferred radicals are ethyl and n-propyl. The silicates used in the present invention are not polymeric materials such as ethylpolysilicates which have not been found useful in the present invention. Materials such as methyltrimethoxysilane and phenyltrimethoxysilane have also been found to be not useful because emulsions made from these materials did not cure after removal of water.

Component (D) is colloidal silica. Finely ground colloidal silica may be dispersed in a polydiorganosiloxane emulsion. Common forms of colloidal silica are commercially available as dispersions in water of colloidal silica, as anhydrous powders of fumed or precipitated silica, and as amorphous silica known as diatomaceous earth. Sodium stabilized, commercially available colloidal silica sol of pH 10 or more is preferable. These are sols of colloidal silica having a surface area of about 150 m ² / g to about 750 m ² / g and a solids content of about 15% to 50% in water. This colloidal silica acts as a reinforcement to provide improved physical properties.

The process of the present invention produces silicone elastomers by removing water from the emulsion resulting from combining components (A), (B) and (C) with any of the components (D) in the amounts mentioned above. When combining the components, the polydiorganosiloxane (A) is mixed with the dialkytin dicarboxylate (B) only when the alkylorthosilicate (C) is present. Immediately after mixing (A), (B) and (C), an elastic body can be formed by removal of water. Water can only be removed at room temperature by exposing the mixture layer of (A), (B) and (C) to the atmosphere and evaporating the water. The time taken for the removal of water depends on the thickness of the emulsion layer. Evaporation rates can be increased by raising the temperature or by decreasing the pressure or relative humidity of the atmosphere to which the emulsion is exposed. The elastic bodies obtained from the components (A), (B) and (C) are relatively weak because they do not contain reinforcing materials. The addition of colloidal silica (D) improves the physical properties of the elastomer, particularly its tensile strength and elongation.

The method of the present invention can be conveniently carried out by combining the components into two parts, namely the first part and the second part and storing them in a two-part system. Subsequently, the first part and the second part are combined. By combining the first part and the second part according to the method of the present invention, the polydiorganosiloxane (A) and the di Alkyltindicarboxylates (B) should be stored in separate parts The other components used in the latex, (C) and (D), may be stored in combination with any one or both of parts I and II. .

Preferred mixtures include the first part consisting essentially of (A) and the second part consisting essentially of components (B), (C) and (D); Part I consisting essentially of components (A) and (C) and part II consisting essentially of components (B) and (D); Part I consisting essentially of components (A) and (D) and part II consisting essentially of components (B) and (C); And a first part consisting essentially of components (A), (C) and (D) and a second part consisting essentially of component (B). The most preferred mixtures are mixtures consisting essentially of components (A) and (C), with the first part consisting essentially of components (B) and (D), and the first part consisting essentially of components (A) and A mixture consisting of (D) and the second part consisting essentially of components (B) and (C).

The amount of components used in the first part and the second part, and the amount of the first part and the second part mixed together by the method of the present invention are within the exact range of the components present in the latex produced by the method. It is the amount to be possible. This amount is based on 100 parts by weight of hydroxyl terminated polydiorganosiloxane (A). The amount of dialkyl tin dicarboxylate (B) can be varied from 0.1 to 2.0 parts by weight, preferably from 0.25 to 0.75 parts by weight. The amount of colloidal silica (D) can be varied from 0 to 100 parts by weight, preferably 1 to 50 parts by weight, most preferably 5 to 50 parts by weight. Higher amounts of colloidal silica tend to provide a high degree of hardness, high tensile strength and low elongation to the elastomers produced. The amount of alkylorthosilicate (C) can be varied from 1 to 10 parts by weight. Preferred amounts are 2 to 6 parts by weight when the free radicals are ethyl or propyl.

Another preferred method of the present invention is in the form of an oil-in-water emulsion having a pH of 9 or more, 100 parts by weight of anionically stabilized hydroxyl end-blocked polydiorganosiloxane, ethyl orthosilicate, having a weight average molecular weight of 200,000 or more. Or 2 to 6 parts by weight of n-propylorthosilicate and a thickening agent to provide the first part. The second portion is produced at a pH of 10 or more by mixing 0.25 to 0.75 parts by weight of dibutyl tin dilaurate and 5 to 50 parts by weight of colloidal silica in the form of an aqueous dispersion of sodium stabilized colloidal silica. The first and second parts are stored separately until ready for use and then combined to form a reinforced silicone elastic latex. Use of a thickening agent sufficient for the first part provides a latex having a viscosity of at least 25 Pa.s at 25 ° C. The solids content of the emulsion used should be chosen such that the latex preferably has a solids content of at least 45% by weight.

In the case of mixing the components together, the resulting latex will form a silicone elastomer by removal of water. The properties of the elastomer can be transformed into parts I or II, or mixtures thereof, with other ingredients added to the emulsion, provided that the additives contain water from the latex produced by mixing the ingredients according to the method of the present invention. It should be such that it does not adversely affect the usefulness of the resulting elastomer. Additives include additional emulsifiers and any water, quartz powder or other fillers such as calcium carbonate, thermal stability additives such as iron oxide, pigments, and thickening agents. Fillers can be used to reduce the cost per unit of elastic product or to produce emulsions useful as caulking materials. Thickening agents are useful for elevating the operating viscosity of silicone emulsions to provide materials that can be used to coat a substrate with a membrane of an elastomeric product. Suitable thickeners are commercially available and should be selected with regard to their stability and usefulness at pH 10 and above. Useful thickening agents include cellulose derivatives, alkali salts of polyacrylates and polymethyl acrylates, sodium and ammonium salts of carboxylate copolymers, and colloidal clays. Preferred thickeners are the sodium salts of polyacrylates. Emulsifiers and water can be used to aid in the emulsification and mixing of the components. For example, dialkyl tin dicarboxylates are preferably used as emulsions. Preferred colloidal silica is a colloidal silica sol in water, and anhydrous powder of colloidal silica may be dispersed in water.

The silicone latex produced by the process of the present invention may contain a wide range of concentrations of the components necessary to make useful products. Low solids emulsions can be used to impart water repellent properties to substrates such as fabrics or paper by coating and drying the substrate. Latex with a solids content of, for example, at least 45% by weight can be used to provide a thicker elastomeric membrane in coating applications such as roofing coatings. When thick coatings such as roof coverings are desired, it is preferred that the latex viscosity is at least 25 Pa · s at 25 ° C. Lattes with a solid content of at least about 45% by weight and a viscosity of at least about 25 Pa.s form a continuous dry film free of cracks when applied to substrates with a wet thickness close to 1.5 mm. Latex with a solids content and viscosity lower than the values mentioned above tends to crack after drying when applied at this thickness. Latexes having a high solids content and a viscosity high enough to produce a paste-like material are useful as coking materials. This solids content is a percentage of the non-volatiles remaining in 2 g of the emulsion sample after heating for 1 hour at 150 ° C. in an air circulating oven. This sample is placed in an aluminum foil dish 60 mm in diameter and 15 mm deep.

Embodiments of the present invention can be used to make continuous foam, elastic silicone foams. The foamable composition is prepared by mixing the first and second parts, immediately forming a foam of the mixture, and then immediately removing the water from the foam to produce a continuous bubble, elastic silicone foam. A preferred first part is essentially 100 parts by weight of component (A) (mentioned hydroxyl-terminated polydiorganosiloxane), 1 to 10 parts by weight of component (D) (colloidal silica sol mentioned above), and Component (F) (0.2 to 1.5 parts by weight of fiber or lauryl alcohol or mixtures thereof). The preferred second part consists essentially of 0.1 to 2.0 parts by weight of component (B) (dialkyltindicarboxylate mentioned above), 1 to 10 parts by weight of component (C) (alkylorthosilicate mentioned above), and component (D ) (Colloidal silica mentioned above) 15 to 30 parts by weight.

Fibers or lauryl alcohol, or mixtures thereof, are used to reinforce the walls of bubbles formed when the foam is formed so that the foam is stable, ie the foam is not broken. The fibers used are fibers which are not adversely affected by aqueous emulsions. This fiber is more successfully dispersed in the emulsion when the average diameter is less than 10 mu m and the length is less than 10 mm, preferably when the diameter is less than 5 mu m and the length is less than 8 mm. The smaller fiber diameter and the shorter the length, the easier the dispersion. Glass fibers having a diameter of about 3 μm and an average length of about 4 mm are preferred. The minimum diameter of the useful fibers is about 1 μm and the minimum length of the useful fibers is about 20 μm. Conductive foams can be obtained by using graphite fibers and graphite fibers coated with metals such as nickel. The preferred range of fiber is 4 to 8 parts by weight per 100 parts by weight of component (A).

These fibers reinforce the walls of the bubbles as their bubbles form, acting as foam stabilizers. The reinforced bubble walls are not destroyed when the foam is dried, so that the foam is formed by drying the stabilized foam. This fiber also acts as a reinforcement in the foam bubble walls, making the foam harder and stronger than in the absence of fibers.

Lauryl alcohol has also been found to thicken the mixture of the first and second parts and to stabilize the resulting foam. This lauryl alcohol produces smaller bubbles and softer foams. It has been found that lauryl alcohol is unique in its ability to produce homogeneous small-bubble bubbles. Mixtures of fibers and lauryl alcohol can be used to produce the foams. Preferred mixing is 4 to 8 parts by weight of fiber and 0.5 to 1.0 part by weight of lauryl alcohol, based on 100 parts by weight of component (A).

The mixture of the first and second parts may be foamed by stirring in the air by mechanical means such as metal stirring, or by foaming air or other gas through the mixture and bubbling. This foam may be produced using known, conventional machines used to produce mechanical foam.

The mixture of the first part and the second part may be formed into a foam by placing the mixture in an aerosol container and then adding an aerosol propellant into the mixture under excess atmospheric pressure. 1 to 25 parts by weight of an aerosol propellant selected from the group consisting of isobutane, propane, dichlorodifluoromethane, trichlorofluoromethane, and mixtures thereof is added to the mixture and mixed. Release of the mixture from the vessel into the space under atmospheric pressure results in foaming due to the expansion of the aerosol propellant in the mixture. Due to the presence of component (F) the foam is stable. The water is then removed from the stable foam to form a continuous bubble, elastic silicone foam. This method does not require a maturation period. The mixture may be prepared immediately and then used to foam and immediately dried to form a foam.

An aerosol propellant may be added to the first portion of the first aerosol vessel and the second portion of the second aerosol vessel. The two can be stored in this form and then optionally combined to produce a foam. The mixture of the first aerosol container and the second aerosol container are combined and mixed in the third container under excess atmospheric pressure. After mixing, the combined mixture is immediately released into the space under atmospheric pressure to form a stable foam. Removing water from the foam creates a foam.

The foam also pumps the components of the first part into the first aerosol container and then mixes the components in each container and then pumps the mixed components into the third container when continuously mixing the first and second components. As in the case of can be generated in a continuous method. The rate of incorporation into the vessel and the rate of release are adjusted to maintain the ratio of the aforementioned components. The mixture from the third vessel is continuously released into the space at atmospheric pressure, forming a continuously stable foam. Water is continuously removed from the foam to form a foam.

The stable foam produced by the method in this embodiment can be removed by any suitable method, for example by drying at room temperature, drying at elevated temperature, drying in a microwave, or by freezing the foam and then thawing it at room temperature. Water can be removed by drying. The method of removing water is not very important because the composition used to create the foam is stable enough to hold itself when the water is removed.

The process of embodiments of the present invention produces a continuous bubble, elastic silicone foam having good thermal stability and weather resistance compared to organic foams. This foam is useful as an insulating buffer material, a lightweight electrode agent, and a lightweight encapsulant. If conductive fibers are used, the foam can be used as an electrical connector or a pressure switch, in particular when carbon black is added to the formulation.

The following examples are for the purpose of illustrating the invention in detail, and are not intended to limit the scope of the invention as described in the claims. All parts are parts by weight.

Example 1

A two-part silicone elastic emulsion system is prepared.

Part I is an emulsion polymerized with hydroxyl terminated polydimethylsiloxanes having a weight average molecular weight of about 325,000. The emulsion is prepared by mixing 54 parts of water, 100 parts of low molecular weight linear hydroxyl terminated polydimethylsiloxane, and 4 parts of a surfactant consisting of 30% sodium lauryl sulfate. The mixture is homogenized, then mixed with 1 part of dodecyl benzene sulfonic acid and polymerized. After polymerization, the emulsion is made basic by mixing 0.5 parts of 50% aqueous diethylamine. The pH of the emulsion is approximately 10 and its solids content is about 63% by weight.

The second part is prepared by mixing 5 parts of ethyl orthosilicate and 0.5 part of dibutyl tin dilaurate.

Subsequently, the first part and the second part are mixed to prepare an emulsion which can be cured at room temperature immediately after preparation of the preparation. Immediately after mixing, the resulting emulsion is degassed and poured into a chase to produce a 1.5 mm thick wet sample. After 7 days at 77 ° F and 50% relative humidity, the sample is cured and dried, and the elastic film is subjected to physical properties according to ASTM D412 for break tensile and elongation at break and ASTM D624 die B for tear strength. Test for. Unreinforced elastomers that do not contain colloidal silica have a tensile strength of 0.25 MPa, an elongation of 253%, and a tear strength of 1.75 kN / M.

Example 2

A two-part silicone elastomer emulsion system containing a reinforcing filler is prepared.

The mixture (part I) was 100 parts of a dispersion of colloidal silica in water containing 15% by weight of colloidal silica in a beaker with an air motor, 2 parts of diethylamine, and the polydimethylsil of Example 1 Prepared by mixing 172 parts of oxane emulsion and 0.3 part of a silicone antifoam emulsion containing 30% by weight of active ingredient. The pH of this mixture is at least 10. The mixture (part II) is prepared by mixing 5 parts of n-propyl orthosilicate and 0.5 parts of dibutyl tin dilaurate.

Subsequently, the first part and the second part are combined and mixed evenly. This mixture is degassed and then a test sample is formed as in Example 1. This test sample is formed within 1 hour of initial mixing of Part I and Part II. Curing and testing as in Example 1 showed that the tensile strength was 1.43 MPa, the elongation was 225%, and the tear strength was 11.7 KN / m.

Example 3

Different crosslinkers are evaluated.

As a final step, part I was prepared as in Example 2 except adding 9 parts of an emulsion of an acrylic thickener containing 30% by weight of solids.

Part II is prepared by mixing 5 parts of the crosslinker described in Table I with 0.5 parts of dibutyltin dilaurate. Subsequently, the first and second portions are mixed, degassed, a test sample is made, cured and tested as in Example 1. The results are shown in Table I.

From this result, the present invention shows that only the crosslinking agent

It can be seen that it is properly cured only in the case of alkyl orthosilicates.

Example 4

A series of two-part emulsions are prepared by varying the amount and form of alkylorthosilicate crosslinkers and the amount of dibutyltindilaurate catalyst.

The first part is prepared as in Example 3.

The second part is prepared by mixing the silicate in the form and amount described in Table II below with the amounts of the catalysts mentioned. Comparative Examples are prepared using alkylpolysilicates.

Subsequently, the first and second parts are mixed, degassed, a test sample is made, and then cured and tested as in Example 1. The results are shown in Table II. The minimum amount of catalyst required to cure depends on the alkylorthosilicate used.

Example 5

Comparative compositions are prepared to demonstrate the need for alkylorthosilicates.

A composition is prepared as in part I of Example 2. 0.5 part of a dibutyl tin dilaurate catalyst is added to this composition. The properties of the sample of the catalyzed composition are tested as in Example 1, before the catalyzed composition is aged for the time described below before the test sample is prepared, before the sample is prepared. The results showed that the composition did not produce curable product until the composition had aged for at least 5 days. Optimal properties are not achieved until at least 9 days after catalysis prior to preparation before aging.

Example 6

The shelf life of the two-part composition is evaluated.

Two first parts were prepared by mixing 172 parts of the polydimethylsiloxane emulsion of Example 1, 10 parts of the thickener of Example 3, and 3 or 5 parts of n-propylorthosilicate to obtain a homogeneous emulsion.

Two parts II are prepared by mixing 100 parts of the colloidal silica emulsion (15 parts of silica) of Example 2 with 0.25 parts or 0.5 parts of dibutyl tin dilaurate.

A portion of the two first parts is mixed with two second parts to prepare the n-propylorthosilicate and dibutyltindilaurate moieties shown in Table III below. Samples are prepared as in Example 1 using the four mixtures. Samples were tested as in Example 1 and the results are shown in Table III.

The remainder of the emulsion is aged for 6 months in a sealed container at 23 ° C. These are then mixed together, made into test samples and tested as above. The results are shown in Table III.

Example 7

A series of compositions are prepared to evaluate the utility of various colloidal silica emulsions.

Three different colloidal silica emulsions are used in two different amounts each to produce six first parts. Colloidal silica A is a sol containing 15% by weight of colloidal silica in water having a surface area of about 750 m ² / g. Colloidal silica B is similar except that it contains 30% by weight of colloidal silica having a surface area of about 375 m ² / g. Colloidal silica C is similar, except that the specific surface area is containing from about 150m ² / g colloidal silica 50% by weight.

Each of the six emulsions is prepared by mixing the colloidal silica solution in the amounts shown in Table IV, two parts of diethylamine, 172 parts of the polydimethylsiloxane emulsion of Example 1, and 0.5 parts of the antifoaming agent of Example 2. Each pH is above 10.

Four n-parts are prepared by mixing together n-propylorthosilicate and dibutyltindilaurate in the amounts described in Table IV.

Each of the first parts is then mixed with each of the second parts as described in Table IV to give a total of 24 mixtures. The viscosity of each mixture was measured at room temperature and listed in Table IV. Each mixture is then made into a test sample, dried, cured and then tested as in Example 1. The results are shown in Table IV.

The quality of the film obtained upon curing was observed and judged, and the results are shown in Tables IV to 1-10. Grade 1 means that the membrane is severely shrinked and cracked into a large open gap. A rating of 5 means severe check cracking. Grade 10 is crack free. It can be seen that the mixture with the highest viscosity and solids content forms the best film. Mixtures with a solids content of about 55% or less and a viscosity of about 25 Pa · s or less do not produce a film free of cracks. Physical property values given for cracked membranes are obtained by carefully cutting the specimens so that they contain minimal grooves. Viscosity is the most important of these variables to obtain a good membrane after emulsion drying and curing.

Example 8

Prepare two-part compositions useful for making foams.

The first part comprises 13.67 g of the colloidal silica dispersion (15 wt% silica) of Example 2, 3.0 g of a 50 wt% solution of diethylamine, and the emulsion polymerized hydroxyl terminated polydimethyl siloxane (polymer of Example 1) 58 wt.%), 290.19 g, diameter of about 2.6 to 3.8 μm, length less than 8 mm, average length of about 4 mm, 9.08 g of glass fiber, 1.51 g of lauryl alcohol and 3.07 g of 30% by weight solution of acrylic thickener were mixed together. Manufacture. The solids content of this composition is about 58% by weight.

The second part consists of 8.51 g of n-propyl orthosilicate, 1.06 g of a 50% by weight solution of dibutyl tin dilaurate, 192.1 g of a colloidal silica dispersion in part I of the above, and disodium N-octadecylsulfosucciniamate A 35 wt% solution is prepared by mixing 8.58 g and 6 g of the acrylic thickener solution of the first part.

The first and second parts are combined in the mixer and mixed until uniform. 75 g are collected and placed in an aerosol container to operate the valve. 6 ml of isobutane propellant is added to the vessel and shaken to mix the propellant and the emulsion. The remaining portion of the emulsion is mechanically foamed by rapid mixing for 10 minutes until sufficient air is agitated into the mixture in a mixer (Kitchen-type mixer with a vertical vigator) to foam. The foam is then transferred to a paper cup and cured by removing water. The first cup is dried at room temperature. The second cup is frozen for 24 hours at 0 ° F and then dried for 4 days at 70 ° F. The third cup is placed in a low heat microwave for 15 minutes.

When the emulsion in the aerosol container is released into three cups, bubbles form. The three foamed cups are cured in the same manner as mentioned above for the mechanically generated foam.

Each cup of cured foam contains continuous bubbles, elastic foam. Samples of this foam are cut and weighed to measure density. The results are shown in Table V.

Table IV

Density, kg / m ³

If a similar composition is prepared without the use of fiberglass and lauryl alcohol so that it can be cured by stabilizing the foam, the foam breaks during curing at room temperature and no foam is obtained.

TABLE I

Comparative Example

TABLE II

Comparative Example

TABLE III

Table IV

Claims (4)

Before use, two-part (A) monovalent hydrocarbon radicals having a weight average molecular weight of about 50,000 and organic radicals containing less than 7 carbon atoms per radical or less than 7 carbon atoms per radical 100 parts by weight of anionic stabilized hydroxyl terminated polydiorganosiloxane, which is a roalkyl) ethyl radical and is present as an emulsion of dispersed particles in water having a pH of 9 or more, (D) 1 to 10 weights of colloidal silica Parts and (F) 1 to 10 parts by weight of fibers having a diameter of 1 to 10 µm and a length of 30 to 100 mm, a lauryl alcohol of 0.2 to 1.5 parts by weight, or a ratio of length to diameter of at least 10: 1 Part I consisting essentially of the mixture and 0.1 to 2.0 parts by weight of (B) dialkyltindicarboxylate, (C) the general formula Si (OR ') ₄ [wherein R' is a lower alkyl radical having 1 to 4 carbon atoms Alkyl orthosilicate 1 10 parts by weight of the component and (D) 15 to 35 parts by weight of colloidal silica, comprising the components stored as the second part, the first part and the second part of the mixture to prepare a dispersion of the components in water (1 ); Immediately forming a bubble of the mixture (2); And (3) preparing the foam by immediately removing water from the foam. The method of claim 1 wherein the foam is formed by mechanical agitation. The process according to claim 1, wherein component (D) is present as a colloidal silica dispersion in water having a pH of at least 7 and a solids content of 10 to 60% by weight. A cured silicone elastic foam produced from the method of claim 1.