CA2098897A1 - Device for protecting and connecting electrical circuits - Google Patents
Device for protecting and connecting electrical circuitsInfo
- Publication number
- CA2098897A1 CA2098897A1 CA 2098897 CA2098897A CA2098897A1 CA 2098897 A1 CA2098897 A1 CA 2098897A1 CA 2098897 CA2098897 CA 2098897 CA 2098897 A CA2098897 A CA 2098897A CA 2098897 A1 CA2098897 A1 CA 2098897A1
- Authority
- CA
- Canada
- Prior art keywords
- water
- mixture
- alkali
- fibers
- sio2
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02G—INSTALLATION OF ELECTRIC CABLES OR LINES, OR OF COMBINED OPTICAL AND ELECTRIC CABLES OR LINES
- H02G15/00—Cable fittings
- H02G15/003—Filling materials, e.g. solid or fluid insulation
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
- C04B28/24—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing alkyl, ammonium or metal silicates; containing silica sols
- C04B28/26—Silicates of the alkali metals
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/28—Protection against damage caused by moisture, corrosion, chemical attack or weather
- H01B7/282—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable
- H01B7/285—Preventing penetration of fluid, e.g. water or humidity, into conductor or cable by completely or partially filling interstices in the cable
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B7/00—Insulated conductors or cables characterised by their form
- H01B7/17—Protection against damage caused by external factors, e.g. sheaths or armouring
- H01B7/29—Protection against damage caused by extremes of temperature or by flame
- H01B7/292—Protection against damage caused by extremes of temperature or by flame using material resistant to heat
-
- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2111/00—Mortars, concrete or artificial stone or mixtures to prepare them, characterised by specific function, property or use
- C04B2111/90—Electrical properties
- C04B2111/92—Electrically insulating materials
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/91—Use of waste materials as fillers for mortars or concrete
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Ceramic Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Structural Engineering (AREA)
- Organic Chemistry (AREA)
- Compositions Of Macromolecular Compounds (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Sealing Material Composition (AREA)
- Connector Housings Or Holding Contact Members (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A device for protecting and connecting electrical circuits has a housing which includes at least one opening for receiving at least one cable with electrical lines and at least one additional opening enabling the production of fixed or detachable connections to connection or control lines via the electrical lines. The housing is filled with an insulating sealing and embedding compound. To ensure a high resistance to temperature and accordingly protection against short-circuiting even at extremely high temperatures, while maintaining a high insulating resistance, the sealing and embedding compound has a binder matrix having as chief constituent a hardened mixture of finely particulate SiO2 and at least partially water-soluble silicates.
A device for protecting and connecting electrical circuits has a housing which includes at least one opening for receiving at least one cable with electrical lines and at least one additional opening enabling the production of fixed or detachable connections to connection or control lines via the electrical lines. The housing is filled with an insulating sealing and embedding compound. To ensure a high resistance to temperature and accordingly protection against short-circuiting even at extremely high temperatures, while maintaining a high insulating resistance, the sealing and embedding compound has a binder matrix having as chief constituent a hardened mixture of finely particulate SiO2 and at least partially water-soluble silicates.
Description
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BACKGROUND OF THE INVENTION
1. Fi~l~ of ~he Invention The present invention relates to a device for protecting or connecting electrical circuits with a housing which lncludes at least one opening for receiving at least one cable including electrical lines and at least one additional opaning enabling the production of fixed or detachable connections to connection or control lines via the electrical lines, and which is filled with an insulating sealing or embedding compound.
BACKGROUND OF THE INVENTION
1. Fi~l~ of ~he Invention The present invention relates to a device for protecting or connecting electrical circuits with a housing which lncludes at least one opening for receiving at least one cable including electrical lines and at least one additional opaning enabling the production of fixed or detachable connections to connection or control lines via the electrical lines, and which is filled with an insulating sealing or embedding compound.
2. Description of the Related Art A disadvantage in known devices of this type, which can ~ be cable sealing devices, cable branch or splice boxes, cable end distributors or cable sleeves, and particularly plug-in connectors, consists in the fact that they can only withstand higher temperatures to a limited extent. The sealing and embedding compound is impaired under the influence of high temperatures such as those occurring in nuclear power stations and particularly in fires. The compound can dissolve and in extreme cases can even be liquefied or gasified. The insulating capacity of the compound is destroyed relatively quickly under the influence of extreme heat that to which devices may be subjected.
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It should be mentioned that the use of organically based duromer backbone polymers as binder matrices for insulating materials is preferred in the modern electric and electronics ~ndustrv. These duromer materials are preferably produced ~rom epoxy resins and polyurethane resins, amino plastics and/or phenol plastics. Recently, hybrid systems, e.g. with isocyanurates, polyimides and other nitrogen-containing polvmers, have also become known especially for improving long-term temperature resistance. Epoxy resins continue to be considered particularly reliable insulating materials, since they have made possible modern solutions in electrical ; engineering, among others, in electronic and electromagnetic structural component parts because of their favorable processing properties and work material characteristics. "
Despite the excellent properties of duromer tool resins, particularly epoxy resins, they are not capable of providing solutions to a number of problems involved in sealing and ;
embedding because their organic binder matrices have no long-term resistance to increased temperatures and in some instances exhibit considerable shrinkage in spite of their high proportion of inorganic fillers. Although binder matrices with higher glass transition temperatures which can temporarily withstand temperatures of up to approximately 360~C have been developed with the recently known hybrid systems, e.~ based on epoxy resins and isocyanurates, their long-term temperature resistance is still limited to roughly 250 to 300~C.
Thus, with respect to binder matrices having a high insulating resistance in addition to a long-term resistance to temperatures, there still exists a gap in the temperature range between 300C and 1500C.
In order to fill this gap, commercial endeavors aimed at developing such insulating materials with a high temperature resistance on an inorganic basis. Aluminum oxide, silicon dioxide, and aluminum silicates were among the raw materials employed. Nevertheless, a suitable sealing and embedding compound could not be produced because of the lack of knowledge concerning the structure`of the binder matrix.
However, other essential factors also had a negative influence on the final characteristics. Among these factors were:
- impurities in the filler material which e.g. impaired electrical characteristics;
:~, - uneven grain distribution in the binding agents and filler materials leading to disruptions in the spatial binder matrix structures and a deterioration of mechanic,l characteristics:
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- very slow hardening processes (up to 30 days at room temperature) with "more easily water-soluble" binder ' constituents, additional crystallization during the hardening process, and development of large crystals so that a homogeneous, resistant binder matrix could not be developed;
- air-drying sealing and embedding compounds produced, as a rule, from water glasses with quartz filler and aluminum oxide filler materials can generally only be hardened at temperatures up to a maximum of 60C in the presence of circulating air, since higher temperatures during initial hardening - due to the increased steam pressure of the water - lead to damage and formation of cracks, etc. in the compound so that it is not possible to seal large spaces or embed in thick layers with these compounds.
However, chemically binding, inorganic sealing and embadding compounds are also known which are generally based on phosphates and alXali silicates. The hardening reactions proceed either in acidic medium as condensation reactions or as precipitation reactions by adjusting a determined ion concentration. However, acidic condensation reactions lead, among other things, to corrosion phenomena in relation to metallic work materials, as is the case e.g. with zirconium-magnesium phosphates. Thus, on the whole, inhomogeneous ~;-.:
' binder matrices with fluctuating high-temperature resistance and insulating resistance are obtained.
But also there remains much to be desired of the resistance to water, water steam, alkalis and many others.
As a result of these and other characteristics, the inorganic sealing and embedding compounds known from the prior art have many weaknesses and can only be used economically and technically within a very limited spectrum of applications in spite of a possible static temperature resistance of around 1000C. Often, they are only used at all because the market offers no alternative possibilities.
However, since the demand for sealing and embedding compounds which, after hardening, form a binder matrix which is resistant to high temperatures and has a high insulating resistance continues to increase in hi-tech electrical and electronic technology for technical as wPll as economic reasons, alternative, economical innovations must be developed.
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' 8UMMARY OF THE INVEN~ION
TherePore, the primary object of the present invention is thexe~ore to further develop the device of the above-desaribed type in such a way that it is capable of withstanding high temperatures with a sealing and embedding compound based on inorganic binder matrices with high insulating resistance and long life. This is because the cable insulating and wire insulating materials are destroyed at the required high temperature loads (750C, 3 h, and 1000C, 10 min). Such temperatures reduce the insulation to a kind of ash with a very high proportion of glass fibers. But this ash disintegrates under the slightest mechanical load. For this reason, it is important that the sealing compound protect the individual wires located in the cable connection region against mechanical stresses so as to ensure the operability of the plug-in connection. In so doing, it must be taken into account that the devices, e.g. plug-in connectors, must conform to Ex II d type explosion protection class.
Regulations governing the layout of electrical components state that parts intended for use may have no "noxious 20 spaces". In this type of application, "noxious spaces" are defined as spaces in which e.g. gases or mixtures of dust and air could collect and result in destruction if ignited.
In accordance with the present invention, for ensuring a high resistance to temperature and accordingly protection against short-circuiting also at extremely high temperatures, but with a high insulating resistance the sealing and embedding compound has a binder matrix having as chief constituent a hardened mixture of a) ~ln~ly particulate SiO2 and b) at least partially water-soluble silicates.
When the silicate-containing binder matrix is built from a threa-dimensional lattice structure, it ensures outstanding mechanical stability of the sealing and embedding compound, on the one hand, and an extremely high resistance to temperature 10 with a high insulating resistance, on the other hand.
? Further, the additives, e.g. filler materials, can be fibers which are taken up in the binder matrix so as to be distributed in a finely-dispersed manner.
Devices according to the invention with a compound based on a silicate-containing binder matrix also allow long-term resistance to temperatures of more than 1000C. Resistance tQ
temperatures of up to 1500C can be observed. Another ; ;
advantage is that the binder matrix is not flammable.
Moreover, the binding agent has a high resistance to solvents, -20 grease, oils, fuels of all types as well as to strong caustic materials and acids. In addition to the extremely great hardness of the binder matrix, a high flexural strength, e.g.
up to 30 MPa, a high compressive strength, e.g. up to 90 MPa, - -.
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a high module of elasticity, and high vibration damping can be observed.
Further, the binder matrix has a very low thermal expansion coef~icient (approximately 4 to 9 x 10-6Kl).
Further, extremely low shrinkage and creep characteristics have been demonstrated which are substantially lower than in ~ynthetic resin-bonded sealing and embedding compounds.
Further, a very high dimensional stability under alternating temperature loads has been established. Also, the binder matrix is friendly to the environment so that there are no disposal-related problems.
Advantages with respect to manufacture consist in the possibility of low processing temperatures between 10 and lOO-C, and in that processing is possible without protective gases or solvents. The only solvent required is water for forming a paste; part of the water can be built into the matrix during the cross-linkage reaction and part of the water escapes during subsequent after-hardening processes. The ;
starting compound can be cast, extruded, injection molded and pressed so that all conventional processing techniques can be employed. The hardening process itself, which is reinforced by thermal energy, can be carried out without pressing pressures, i.e. no costly apparatuses are needed for producing the se~ling and embedding compound~.
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DE~CRIP~ION OF THE PREFERRED EMBODIMENTS
In a ~urther development of the invention, the binder matrlx is produced from the aforementioned mixture of ~inely p~rtlculate SiO2 and at least partia~ly water-soluble silicates, which mixture is hardened at increased temperature.
This mixture results in a uniformly constructed binder matrix which is branched three-dimensionally by polycondensation and ensures an outstanding quality and durabilit~ of the sealing and embedding compound. Another advantage of this step consists in that the starting materials have a very good wetting ratio, i.e. the additives which are to be incorporated in the binder matrix, as appropriate, are built into the binder matrix in a uniform manner.
- Suitable reactive constituents in the production of the binder matrix according to the invention are amorphous sio2, possibly Al203, and the undissolved sio2, if any, of the amorphous water-containing silicic acid. Mixtures of ;~
amorphous sio2 and Al203 are particularly preferred. The weight ratio of sio2 to Al203 can range from 5 - 98 percent by weight sio2 to 95 - 2 percent by weight Sio2, preferably 5 - 80 percent by weight to 95 - 20 percent by weight.
SiO2 is preferably present in amorphous, particularly anhydrous form. This form is also preferred for the finely particulate mixture of sio2 and Al203, although the Al203 can be partly in the form of crystals, for example. The SiO2 can also 25 originate from the amorphous, water-containing silicic acid. -'`, ' .
The finely particulate individual constituents and/or mlxtures have a particle size S 50 ~m, preferably ~ 40 ~m, particularly S 10 ~m. The smaller the particle si~es, the denser and more ~t~bl~ the binder matrix according to the invention.
Surprisingly, it has been found that the use of biogenic silicic acids is indicated for the formation of specific binder matrices according to the present invention, particularly to achieve high resistance to temperatures and to achieve dimensional stability. The biogenic silicic acids possess amorphous structures and are associated with tridymite and/or cristobalite with respect to their mineralogical compositions. The biogenic, amorphous silicic acids are obtained from carbonated rice husks among others. They have sintering points of approximately 1500C and melting points of 15 approximately 1600~C. The grain sizes are S 5 mm, preferably S 3 mm, in particular < 2 mm. The SiO2 contents are 2 90%, particularly 2 95%. In the sealing and embedding compounds according to the invention, they have dual functions, ~ predominantly as binders and/or "reinforcing filler materials".
The oxides can contain impurities such as iron, sodium, potassium, calcium, and so forth. Insofar as the heavy-metal impurities are ~ 0.5% and are embedded in the binder matrix in a dispersed manner, they often do not change the insulating resistance. The ratio of oxide components, i.e. sio2 and/or Al2O3, to the water-soluble silicates is 80 to 20 : 5 to 60, 11 '', : ' " ' '~ ~ . ' ' . ' . , particularly in a quantitative range of 15 percent by weight ~n relation to the total mixture of the two components. Dusts from ~igh-temperature smelting processes, filter dust, ~l~ctrostatic filter ash from high-temperature nuclear reactors, and calcinated, powdered bauxite are particularly su~table reactive components.
For binder matrices with a particularly high insulating resistance of 2 1o6n, particularly 2 1o8n~ the use of aluminum silicate, particularly dehydrated aluminum silicate, is 10 preferred according to the invention. The aluminum silicate ``
may be a kaolinite as Al2O3 2SiO2 H2O and meta-kaolinite `
(dehydrated kaolinite) as Al2O3 2SiO2. The transitional states can also be used. Meta-kaolinites are preferred since they possess a greater reactivity.
` 15 As was surprisingly discovered when using hydraulic binder media such as those described in the following, a minimum content of meta-kaolinite is required in order to ~` impart a greater stability to the hardened compound.
Such additives are particularly advantageous in reactive -components which bond hydraulically in the presence of the existing polycondensating components, so that hybrid systems ` are formed. They include the clinker phases from concrete production, e.g. alite (C3S), tricalcium aluminate (C3A), wherein C = calcium oxide, S = silicon dioxide, and A =
aluminum oxide, as well as high-alumina cement, anhydrides, gypsum, anhydrous alkaline earth, and magnesium oxide.
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Alkali silicates or ammonium silicates which can be usedalone or in mixtures are particularly suitable as water-~oluble sil~cates which act as hardeners for the oxides of sio2 and A1203. They generally include a surplus of free alkali and/or ammonium. The molar ratio of alkali or ammonium to silicon oxide is generally between 1.0 and 5 moles, preferably between 1.5 and 4 moles sio2 per mole of alkali or ammonium.
Potassium water glass and/or ammonium water glass are particularly preferred since they impart particularly good, homogeneous physical characteristics to the structure-forming matrix and bind the necessary additives in a very favorable manner. The alkali silicates or ammonium silicates can also be preparations in àqueous form.
- ~he formation components of silicates, i.e. the corresponding oxides or hydroxides of the alkali or ammonium and amorphous, water-containing silicic acids in the form of dispersed powder, can also be contained in a particularly advantageous manner instead of silicates. This step has the ~
advantage that these precursors of the silicates have good -storage properties as solids and can be mixed with water to form a paste prior to processing. Thus, according to the invention, reactive single-component systems are obtained, which are particularly simple to manage.
In a particularly advantageous manner, salts of fluorosilicic acid can also be used as hardeners, either alone . . ~ ,,-. . ~ . . -or in combination with the aforementioned alkali siliaates.
These include compounds of the general formula MI2 I siF6]
wherein MI - univalent metal.
Alkali fluorosilicates and alkaline earth fluorosilicates such as sodium, barium hexafluorosilicates, are mentioned by way of example. Organic fluorosilicates are also suitable e.g. bis-(methylammonium)fluorosilicate, bis-~dibutylammonium)-fluorosilicate, dianilinium fluorosilicate.
The binder matrix according to the invention is formed by `
a hydraulic and/or polycondensation`process. Not only can one-component and two-component sealing and embedding compound systems be produced by way of these hardening mechanisms, but the binding parameters can also be varied within relatively "
broad limits. These parameters include the so-called pot life, hardening temperatures, green strength, and final -strength.
Since the water in the polycondensating substances according to the invention, which form the binder matrix, only serves as a vehiale or wetting agent, it can be used in hybrid systems for activating the hydraulically binding substances forming the binder matrix so as to achieve a faster green strength.
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. ' ' ~: '' " ', The following are particularly suitable additives for binding in the binder matrix according to the invention:
- filler materi~ls wollastonite, mica, inorganic sulfates such as barium ~ul~ate, inorganic carbonates such as calcium carbonate, inorganic oxides such as silicon dioxide (quartz powders) or the like.
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Strengthening agents in the form of fibers can be added if necessary for certain uses.
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~ 10 Ex~mples of inorganic fibers are:
: glass fibers, carbon fibers, rock wool, aluminum silicate fibers and aluminum oxide fibers, ceramic fibers, silicon carbide fibers, etc. insofar as they do not lower the insulating resistance.
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~xamples of organic ~ibers:
phenol fibers, aramide fibers and the like.
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Porous structures are often required for diverse uses of ` sealing and embedding compounds to take over sound-damping and thermal-insulating functions and/or to reduce the inherent weight. For this reason, a further development of the present invention provides to produce self-supporting structural foams `` by adding expanding agents and/or propellants prior to or .
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during the binding process. According to the invention, par~icularly suitable expanding agents and/or propellants include peroxide compounds such as hydrogen peroxide, persul~ates, perborates, percarbonates, organic peroxides such as dibenzoyl peroxide or compounds which form gases or expand in contact with water, e.g. carbides, aluminum powder, metal hydrides, hydrazine derivatives, semicarbazides or the like.
Foams can also be produced during the pot life phase by introducing gases such as air, nitrogen, and carbon dioxide.
These can be open-cell or closed-cell foams so that a wide range of applications is covered. But foam-like structures can also be developed in the binder matrix according to the invention by adding so-called micro~cavities, such as hollow micro-glass spheres.
It is also possible to produce pore structures by adding powder or fibrous materials as pore-forming materials which evaporate, melt or shrink when hardening.
Moreover, additional filler materials such as pigment, dyes, thixotropic agents or other additives for regulating rheological characteristics, wetting or the like can be added to the sealing and embedding compounds according to the invention for use in devices of the type mentioned in the beginning. ~ ;
In order to maintain a low water content or binder/water ratio when forming a ~aste with the homogeneous starting components and/or to adjust lower viscosities for casting, : :`
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in~ection molding or extrusion, it has surprisingly been found that known green-mortar additives for liquefying and/or pla~ticizing can be added to the mixing water, to the liquid h~rdener and/or to the pasty compound. Such additives include lignosulfonates, melamine formaldehyde condensate sulfonates, naphthalene formaldehyde condensate sulfonates, tensides, abietic acid derivatives, and certain hydrolyzed proteins.
The additives generally amount to 5% with reference to the binder weight.
In order to stabilize a high insulating resistance during and/or in the use of the compounds according to the invention any existing hygroscopicity can be eliminated by furnishing hydrophobicity. Nonpolar organic compounds, metallo-organic, silico-organic and inorganic compounds are suitable for providing hydrophobicity. The water-repelling agents most often used include salts of aluminum and zirconium, complex chromium salts, silanes, silicones, and perfluorinated organic compounds insofar as no conductivity can develop under conditions of relative humidity. Silanes and/or silicones are particulàrly preferred, since they can be at least partially - integrated in the binder matrix as compounds of the same family.
But hydrophobicity can also be achieved by increasing the concentrations of alkaline earth cations in the compound compositions or by means of subsequent impregnation with alkaline earth oxides or the like. Calcium compounds which, i~
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, among other things, react with the still reactive silicates to form insoluble calcium silicates are particularly effective and ~conomical.
Ac¢ording to the invention, the intimate, homogeneous mixture o the starting components sio2 and water-containing siliaates and the necessary additives with water is mixed to form a paste until a deformable consistency is achieved or the starting components are first processed with water and the `~
necessary additives are then added while forming a flowable, pasty consistency, and the compound is then hardened after deformation as required. The hardening compounds can also be applied on a carrier material of metallic, inorganic or organic work materials and then harden. Such carrier materials can be steel, iron, wood, stone, concrete, plastics such as duroplastics or thermoplastics, or the like.
When producing the compact compound for insulation, the compound can be degassed by vacuum beforehand. But gas can also be removed from the pre-formed cast articles or in coatings by shaking or evacuation.
The water or an aqueous, alXaline medium can be used e.g.
in amounts of 5 to 70 percent by weight, preferably 20 to 50 percent by weight, in relation to the total dry compound.
The compounds which are mixed with water to form a paste can be processed by casting, extrusion, injection molding and pressing~
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In the production of compact sealing and embedding compounds the hardening time is approximately 1 to 2 hours at ~5'C, wherein an exothermic polycondensation is used. This i5 ~ollowed by after-drying at 20 to 50C until a constant weight is achieved so as to expel the residual retained water.
If the sealing and emb~dding compounds are to be used at higher temperatures, they are heated by stages to temperatures of +80C to 1500C, wherein an after-hardening can be observed. Generally, for high- temperature applications it is necessary to heat in stages beyond the operating temperatures in order to achieve a good resistance to temperature and a good dimensional stability.
In the absence of additional energy resources for hardening and for forming the binder matrix according to the invention, as is the case e.g. in on-site assembly, the hardening reactions can also be carried out at temperatures >
10C, particularly 15 to 30C, by adding so-called hardening accelerators. Suitable hardening accelerators are anhydrous ; alkaline earth oxides such as quick lime, aluminum phosphates and the above-mentioned clinker phases, high-alumina cements, anhydrides, gypsum and possibly metal hydrides, as has been discovered according to the invention, insofar as they cause a reaction heat of 2 500 joules/g when in contact and/or in solution with water.
In the production of porous sealing and embedding compounds, the compounds harden at 20C in a maximum time of 2 :: :
hours or at 50C in approximately 1 hour. After-hardening can be effected at ~50 to +100C. If the porous sealing and embedding compounds are likewise provided for use at high temperatures, a stepwise heating to temperatures up to 1100C
is also e~fected.
The sealing and embedding compounds can also be furnished with hydrophobicity if required. Silanes, polydimethoxy sllanes or the like are suitable for this purpose.
Because of the low processing temperatures, the inorganic agents according to the invention, provide an extremely wide range of variations for production of the binder matrix, one reason being that all of the additives mentioned above, as well as other additives, can be integrated into the structural matrix in a simple manner. .
On the basis of the binder matrix according to the invention, the person skilled in the art is provided with a binding, inorganically based sealing and embedding compound intended for devices for protecting and connecting electrical circuits which is distinguished by the following advantages and advances, among others:
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- ease of processing - environmental and ecological friendliness `
- uncritical mixture ratios of the 2-component systems ~ . , - adjustable pot life and binding times - ability to process also at temperatures below 0C
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- binding in the presence of water - non-combustibility - extremely economical in comparison to sealing and embedding compounds based on organic polymers.
The properties of the set sealing and embedding compounds include:
- fast green strength and final strength, e.g. 30 minutes - non-combustibility, i.e. no development of flue gases - resistance to solvents, weak and strong alkalis, and sulfuric acid - surface hardness according to Mohs adjustable to 3 to 8 - volume weight in compact compounds: 1600 - 3500 kg/m3 in foam compounds : 200 - 1000 kg/m3 - flexural strength: adjustable between 10 - 40 MPa - compressive strength: adjustable between 20 - 100 MPa - E-module: 10,000 - 50,000 MPa - linear thermal expansion: 1 to 8 x 10-6/k-- high degree of vibration damping - lower creep behavior in comparison to organic sealing and embedding compounds - thermal dimensional stability - high resistance to ageing - high insulating resistance of > lOo M n.
In the device according to the invention for protecting and connecting electrical circuits, it follows from the above that the cavities between the electrical elements and between the device walls are filled with an insulating, inorganic ~aliny and embedding compound which can be processed in the presence of water without the water participating in the hardening reactions. Thus, the mixing water is only a vehicle as suspending agent and/or dispersing agent for transforming the solid components of the compound according to the invention into a processible, liquid aggregate state. The mixing water is to be removed from the hardened cast articles - usually by evaporation - after polycondensation (hardening).
While the rheological properties of the sealing and embedding aompounds according to the aforementioned compositions are sufficient in simpler construction of the device to achieve cast articles which are free of bubbles, it is considerably more difficult to cast complicated or angular housing constructions to cast cavities so as to be free of bubbles. Although the rheology of the compounds is partially improved by increasing the content of mixing water, this makes sealing and hardening more costly and time-consuming and does not provide a clean technical solution.
In a further development of the invention, the ; rheological processing characteristics of the sealing and embedding compounds which are mixed with water can be improved in a surprising manner with respect to viscosity, flow ' ~. '.
behavior and pouring behavior, etc., possibly accompanied by a ~imultaneous reduction in the mixing water requirement, by add~ng rheology-improving additives to the sealing and embedding compound which are based on alkali phosphates and/or ~lkali alkyl siliconates and their derivatives which take effect when mixed with water.
The backbone binding agents mentioned in the beginning include finely particulate sio2 and/or Al203 and originate from different sources. These are amorphous inorganic substances with a particle size of 100 um.
The further improved backbone binding agents belong to ~.~
the inorganic compounds whose practical applications rely to a great extent on their rheological characteristics which, amo;ng other things, are related to the following:
- the layer structure - the plate-shaped and/or spherical configuration - the negative charges - the variable structure at the particle edges - the cation and anion exchange capacity, and ~0 - the capacity to form different aggregates, suspensions and colloidal dispersions in aqueous systems.
Although the rheological behavior of suspensions or dispersions of the backbone binding agents according to the invention can be described in qualitative terms, they have so ~ . . : ,: , .
far successfully resisted any mathematical treatment.
Surprisingly, it has been found that the alkaline earth ions, preferably Ca~ ions, have a decisive influence on rheological characteristics when the backbone binding agents according to the invention are mixed with water, particularly in the case of m-kaoline. They influence the peptization and accordingly determina the required amount of mixing water for achieving low viscosities and good flow and pouring properties.
Surprisingly, it has now been found that thinner . .
suspensions and dispersions of the backbone binding agents according to the invention and water are obtained when alkali ions, e.g. Na~ ions, are added to the mixing water. A pH of 7.0 is particularly advantageous so that the positive edge charges and edge (+)/ surface (-) contacts are prevented.
Water glasses etc., which are present according to the invention in any case, are used for peptization.
However, the supply of or increased concentration (pH) of alkali ions is not sufficient in itself for increased ` liquefaction, since the negative edge charge density is not increased simultaneously. Surprisingly, it has been found that alkali phosphates and/or alkali alkyl siliconates ::
according to the invention are suitable for enhancing the peptization and increasing the edge charge density so as to ;
achieve thinner-liquid sealing and embedding compounds. The alkali alkyl siliconates set in the presence of C02, among others, to form the polyalkyl silicic acids according to the invention, since the latter impart additional hydrophobic characteristics to the hardened compounds.
These additives of alkali phosphates and/or alkali alkyl silioonates according to the invention not only liquefy the ~ealing and embedding compounds, but also simultaneously reduce the requirement of mixing water without thereby changing the improved rheological properties.
The following alkali phosphates, alkali alkyl siliconates and their derivatives, as well as mixtures thereof, are suitable as additives according to the present invention which improve the rheological properties.
According to the invention, the alkali phosphates are meta-phosphates, ortho-phosphates and/or polyphosphates. The : sodium phosphates and/or potassium phosphates, particularly the sodium polyphosphates and potassium polyphosphates, are particularly preferred.
; ~he alkali alkyl siliconates contain an alkyl group with : 1 to 11 carbon atoms, wherein the sodium alkyl siliconates and/or potassium alkyl siliconates whose alkyl group is a methyl group, ethyl group, propyl and/or butyl group are preferred.
Mixtures of both groups of additives are particularly preferred because - alkali phosphates bring about the higher li~uefaction capacity and - by way of hardening, the alkali alkyl siliconates form . ~ .
`~ 25 ~.. . . , ~ , -. ;. , polyalkyl silicic acids which make the hardened compounds hydrophobic.
All additives are soluble in water at a pH of 7Ø
The added quantities of the additives according to the invention can fluctuate within a wide range. The amounts of these additives contained in the sealing and embedding compounds mentioned in the beginning are determined by the liquefaction capacity relative to the compound compositions and by the required hydrophobicity in the hardened compounds.
In general, the added amounts in relation to the total solids content of a compound according to the invention are - 10.0 m-%, particularly 5.0 m-~, for alkali phosphates and - 50.0 m-%, particularly 25.0 m-~, for alkali alkyl siliconates.
If the additives are in liquid form, they are added to the hardener, insofar as the latter is a liquid water glass.
In all other applications, the additives are mixed in with the -~
backbone binding agents homogeneously.
After the addition of mixing water, the sealing and embedding compounds which are modified by these additives are stable, pumpable, thin-liquid suspensions or dispersions having a relatively high solids conten~.
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~ ~ $ ~ ~ t ~ , The additives also convert the polyvalent cations present in the mixing water, e.g. MgZ', CaZ~, Al3+, into water-soluble complexes so as to prevent, in addition, a flocculent and rapid precipitation of backbone binder particles. This lengthens the processing time since the sealing and embedding compound formulation remains homogeneous for a longer time.
The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.
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It should be mentioned that the use of organically based duromer backbone polymers as binder matrices for insulating materials is preferred in the modern electric and electronics ~ndustrv. These duromer materials are preferably produced ~rom epoxy resins and polyurethane resins, amino plastics and/or phenol plastics. Recently, hybrid systems, e.g. with isocyanurates, polyimides and other nitrogen-containing polvmers, have also become known especially for improving long-term temperature resistance. Epoxy resins continue to be considered particularly reliable insulating materials, since they have made possible modern solutions in electrical ; engineering, among others, in electronic and electromagnetic structural component parts because of their favorable processing properties and work material characteristics. "
Despite the excellent properties of duromer tool resins, particularly epoxy resins, they are not capable of providing solutions to a number of problems involved in sealing and ;
embedding because their organic binder matrices have no long-term resistance to increased temperatures and in some instances exhibit considerable shrinkage in spite of their high proportion of inorganic fillers. Although binder matrices with higher glass transition temperatures which can temporarily withstand temperatures of up to approximately 360~C have been developed with the recently known hybrid systems, e.~ based on epoxy resins and isocyanurates, their long-term temperature resistance is still limited to roughly 250 to 300~C.
Thus, with respect to binder matrices having a high insulating resistance in addition to a long-term resistance to temperatures, there still exists a gap in the temperature range between 300C and 1500C.
In order to fill this gap, commercial endeavors aimed at developing such insulating materials with a high temperature resistance on an inorganic basis. Aluminum oxide, silicon dioxide, and aluminum silicates were among the raw materials employed. Nevertheless, a suitable sealing and embedding compound could not be produced because of the lack of knowledge concerning the structure`of the binder matrix.
However, other essential factors also had a negative influence on the final characteristics. Among these factors were:
- impurities in the filler material which e.g. impaired electrical characteristics;
:~, - uneven grain distribution in the binding agents and filler materials leading to disruptions in the spatial binder matrix structures and a deterioration of mechanic,l characteristics:
':
:
- very slow hardening processes (up to 30 days at room temperature) with "more easily water-soluble" binder ' constituents, additional crystallization during the hardening process, and development of large crystals so that a homogeneous, resistant binder matrix could not be developed;
- air-drying sealing and embedding compounds produced, as a rule, from water glasses with quartz filler and aluminum oxide filler materials can generally only be hardened at temperatures up to a maximum of 60C in the presence of circulating air, since higher temperatures during initial hardening - due to the increased steam pressure of the water - lead to damage and formation of cracks, etc. in the compound so that it is not possible to seal large spaces or embed in thick layers with these compounds.
However, chemically binding, inorganic sealing and embadding compounds are also known which are generally based on phosphates and alXali silicates. The hardening reactions proceed either in acidic medium as condensation reactions or as precipitation reactions by adjusting a determined ion concentration. However, acidic condensation reactions lead, among other things, to corrosion phenomena in relation to metallic work materials, as is the case e.g. with zirconium-magnesium phosphates. Thus, on the whole, inhomogeneous ~;-.:
' binder matrices with fluctuating high-temperature resistance and insulating resistance are obtained.
But also there remains much to be desired of the resistance to water, water steam, alkalis and many others.
As a result of these and other characteristics, the inorganic sealing and embedding compounds known from the prior art have many weaknesses and can only be used economically and technically within a very limited spectrum of applications in spite of a possible static temperature resistance of around 1000C. Often, they are only used at all because the market offers no alternative possibilities.
However, since the demand for sealing and embedding compounds which, after hardening, form a binder matrix which is resistant to high temperatures and has a high insulating resistance continues to increase in hi-tech electrical and electronic technology for technical as wPll as economic reasons, alternative, economical innovations must be developed.
,~
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' 8UMMARY OF THE INVEN~ION
TherePore, the primary object of the present invention is thexe~ore to further develop the device of the above-desaribed type in such a way that it is capable of withstanding high temperatures with a sealing and embedding compound based on inorganic binder matrices with high insulating resistance and long life. This is because the cable insulating and wire insulating materials are destroyed at the required high temperature loads (750C, 3 h, and 1000C, 10 min). Such temperatures reduce the insulation to a kind of ash with a very high proportion of glass fibers. But this ash disintegrates under the slightest mechanical load. For this reason, it is important that the sealing compound protect the individual wires located in the cable connection region against mechanical stresses so as to ensure the operability of the plug-in connection. In so doing, it must be taken into account that the devices, e.g. plug-in connectors, must conform to Ex II d type explosion protection class.
Regulations governing the layout of electrical components state that parts intended for use may have no "noxious 20 spaces". In this type of application, "noxious spaces" are defined as spaces in which e.g. gases or mixtures of dust and air could collect and result in destruction if ignited.
In accordance with the present invention, for ensuring a high resistance to temperature and accordingly protection against short-circuiting also at extremely high temperatures, but with a high insulating resistance the sealing and embedding compound has a binder matrix having as chief constituent a hardened mixture of a) ~ln~ly particulate SiO2 and b) at least partially water-soluble silicates.
When the silicate-containing binder matrix is built from a threa-dimensional lattice structure, it ensures outstanding mechanical stability of the sealing and embedding compound, on the one hand, and an extremely high resistance to temperature 10 with a high insulating resistance, on the other hand.
? Further, the additives, e.g. filler materials, can be fibers which are taken up in the binder matrix so as to be distributed in a finely-dispersed manner.
Devices according to the invention with a compound based on a silicate-containing binder matrix also allow long-term resistance to temperatures of more than 1000C. Resistance tQ
temperatures of up to 1500C can be observed. Another ; ;
advantage is that the binder matrix is not flammable.
Moreover, the binding agent has a high resistance to solvents, -20 grease, oils, fuels of all types as well as to strong caustic materials and acids. In addition to the extremely great hardness of the binder matrix, a high flexural strength, e.g.
up to 30 MPa, a high compressive strength, e.g. up to 90 MPa, - -.
...
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a high module of elasticity, and high vibration damping can be observed.
Further, the binder matrix has a very low thermal expansion coef~icient (approximately 4 to 9 x 10-6Kl).
Further, extremely low shrinkage and creep characteristics have been demonstrated which are substantially lower than in ~ynthetic resin-bonded sealing and embedding compounds.
Further, a very high dimensional stability under alternating temperature loads has been established. Also, the binder matrix is friendly to the environment so that there are no disposal-related problems.
Advantages with respect to manufacture consist in the possibility of low processing temperatures between 10 and lOO-C, and in that processing is possible without protective gases or solvents. The only solvent required is water for forming a paste; part of the water can be built into the matrix during the cross-linkage reaction and part of the water escapes during subsequent after-hardening processes. The ;
starting compound can be cast, extruded, injection molded and pressed so that all conventional processing techniques can be employed. The hardening process itself, which is reinforced by thermal energy, can be carried out without pressing pressures, i.e. no costly apparatuses are needed for producing the se~ling and embedding compound~.
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DE~CRIP~ION OF THE PREFERRED EMBODIMENTS
In a ~urther development of the invention, the binder matrlx is produced from the aforementioned mixture of ~inely p~rtlculate SiO2 and at least partia~ly water-soluble silicates, which mixture is hardened at increased temperature.
This mixture results in a uniformly constructed binder matrix which is branched three-dimensionally by polycondensation and ensures an outstanding quality and durabilit~ of the sealing and embedding compound. Another advantage of this step consists in that the starting materials have a very good wetting ratio, i.e. the additives which are to be incorporated in the binder matrix, as appropriate, are built into the binder matrix in a uniform manner.
- Suitable reactive constituents in the production of the binder matrix according to the invention are amorphous sio2, possibly Al203, and the undissolved sio2, if any, of the amorphous water-containing silicic acid. Mixtures of ;~
amorphous sio2 and Al203 are particularly preferred. The weight ratio of sio2 to Al203 can range from 5 - 98 percent by weight sio2 to 95 - 2 percent by weight Sio2, preferably 5 - 80 percent by weight to 95 - 20 percent by weight.
SiO2 is preferably present in amorphous, particularly anhydrous form. This form is also preferred for the finely particulate mixture of sio2 and Al203, although the Al203 can be partly in the form of crystals, for example. The SiO2 can also 25 originate from the amorphous, water-containing silicic acid. -'`, ' .
The finely particulate individual constituents and/or mlxtures have a particle size S 50 ~m, preferably ~ 40 ~m, particularly S 10 ~m. The smaller the particle si~es, the denser and more ~t~bl~ the binder matrix according to the invention.
Surprisingly, it has been found that the use of biogenic silicic acids is indicated for the formation of specific binder matrices according to the present invention, particularly to achieve high resistance to temperatures and to achieve dimensional stability. The biogenic silicic acids possess amorphous structures and are associated with tridymite and/or cristobalite with respect to their mineralogical compositions. The biogenic, amorphous silicic acids are obtained from carbonated rice husks among others. They have sintering points of approximately 1500C and melting points of 15 approximately 1600~C. The grain sizes are S 5 mm, preferably S 3 mm, in particular < 2 mm. The SiO2 contents are 2 90%, particularly 2 95%. In the sealing and embedding compounds according to the invention, they have dual functions, ~ predominantly as binders and/or "reinforcing filler materials".
The oxides can contain impurities such as iron, sodium, potassium, calcium, and so forth. Insofar as the heavy-metal impurities are ~ 0.5% and are embedded in the binder matrix in a dispersed manner, they often do not change the insulating resistance. The ratio of oxide components, i.e. sio2 and/or Al2O3, to the water-soluble silicates is 80 to 20 : 5 to 60, 11 '', : ' " ' '~ ~ . ' ' . ' . , particularly in a quantitative range of 15 percent by weight ~n relation to the total mixture of the two components. Dusts from ~igh-temperature smelting processes, filter dust, ~l~ctrostatic filter ash from high-temperature nuclear reactors, and calcinated, powdered bauxite are particularly su~table reactive components.
For binder matrices with a particularly high insulating resistance of 2 1o6n, particularly 2 1o8n~ the use of aluminum silicate, particularly dehydrated aluminum silicate, is 10 preferred according to the invention. The aluminum silicate ``
may be a kaolinite as Al2O3 2SiO2 H2O and meta-kaolinite `
(dehydrated kaolinite) as Al2O3 2SiO2. The transitional states can also be used. Meta-kaolinites are preferred since they possess a greater reactivity.
` 15 As was surprisingly discovered when using hydraulic binder media such as those described in the following, a minimum content of meta-kaolinite is required in order to ~` impart a greater stability to the hardened compound.
Such additives are particularly advantageous in reactive -components which bond hydraulically in the presence of the existing polycondensating components, so that hybrid systems ` are formed. They include the clinker phases from concrete production, e.g. alite (C3S), tricalcium aluminate (C3A), wherein C = calcium oxide, S = silicon dioxide, and A =
aluminum oxide, as well as high-alumina cement, anhydrides, gypsum, anhydrous alkaline earth, and magnesium oxide.
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Alkali silicates or ammonium silicates which can be usedalone or in mixtures are particularly suitable as water-~oluble sil~cates which act as hardeners for the oxides of sio2 and A1203. They generally include a surplus of free alkali and/or ammonium. The molar ratio of alkali or ammonium to silicon oxide is generally between 1.0 and 5 moles, preferably between 1.5 and 4 moles sio2 per mole of alkali or ammonium.
Potassium water glass and/or ammonium water glass are particularly preferred since they impart particularly good, homogeneous physical characteristics to the structure-forming matrix and bind the necessary additives in a very favorable manner. The alkali silicates or ammonium silicates can also be preparations in àqueous form.
- ~he formation components of silicates, i.e. the corresponding oxides or hydroxides of the alkali or ammonium and amorphous, water-containing silicic acids in the form of dispersed powder, can also be contained in a particularly advantageous manner instead of silicates. This step has the ~
advantage that these precursors of the silicates have good -storage properties as solids and can be mixed with water to form a paste prior to processing. Thus, according to the invention, reactive single-component systems are obtained, which are particularly simple to manage.
In a particularly advantageous manner, salts of fluorosilicic acid can also be used as hardeners, either alone . . ~ ,,-. . ~ . . -or in combination with the aforementioned alkali siliaates.
These include compounds of the general formula MI2 I siF6]
wherein MI - univalent metal.
Alkali fluorosilicates and alkaline earth fluorosilicates such as sodium, barium hexafluorosilicates, are mentioned by way of example. Organic fluorosilicates are also suitable e.g. bis-(methylammonium)fluorosilicate, bis-~dibutylammonium)-fluorosilicate, dianilinium fluorosilicate.
The binder matrix according to the invention is formed by `
a hydraulic and/or polycondensation`process. Not only can one-component and two-component sealing and embedding compound systems be produced by way of these hardening mechanisms, but the binding parameters can also be varied within relatively "
broad limits. These parameters include the so-called pot life, hardening temperatures, green strength, and final -strength.
Since the water in the polycondensating substances according to the invention, which form the binder matrix, only serves as a vehiale or wetting agent, it can be used in hybrid systems for activating the hydraulically binding substances forming the binder matrix so as to achieve a faster green strength.
.
. ' ' ~: '' " ', The following are particularly suitable additives for binding in the binder matrix according to the invention:
- filler materi~ls wollastonite, mica, inorganic sulfates such as barium ~ul~ate, inorganic carbonates such as calcium carbonate, inorganic oxides such as silicon dioxide (quartz powders) or the like.
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Strengthening agents in the form of fibers can be added if necessary for certain uses.
..
~ 10 Ex~mples of inorganic fibers are:
: glass fibers, carbon fibers, rock wool, aluminum silicate fibers and aluminum oxide fibers, ceramic fibers, silicon carbide fibers, etc. insofar as they do not lower the insulating resistance.
.
~xamples of organic ~ibers:
phenol fibers, aramide fibers and the like.
. ' , . '.
Porous structures are often required for diverse uses of ` sealing and embedding compounds to take over sound-damping and thermal-insulating functions and/or to reduce the inherent weight. For this reason, a further development of the present invention provides to produce self-supporting structural foams `` by adding expanding agents and/or propellants prior to or .
-7 :
during the binding process. According to the invention, par~icularly suitable expanding agents and/or propellants include peroxide compounds such as hydrogen peroxide, persul~ates, perborates, percarbonates, organic peroxides such as dibenzoyl peroxide or compounds which form gases or expand in contact with water, e.g. carbides, aluminum powder, metal hydrides, hydrazine derivatives, semicarbazides or the like.
Foams can also be produced during the pot life phase by introducing gases such as air, nitrogen, and carbon dioxide.
These can be open-cell or closed-cell foams so that a wide range of applications is covered. But foam-like structures can also be developed in the binder matrix according to the invention by adding so-called micro~cavities, such as hollow micro-glass spheres.
It is also possible to produce pore structures by adding powder or fibrous materials as pore-forming materials which evaporate, melt or shrink when hardening.
Moreover, additional filler materials such as pigment, dyes, thixotropic agents or other additives for regulating rheological characteristics, wetting or the like can be added to the sealing and embedding compounds according to the invention for use in devices of the type mentioned in the beginning. ~ ;
In order to maintain a low water content or binder/water ratio when forming a ~aste with the homogeneous starting components and/or to adjust lower viscosities for casting, : :`
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in~ection molding or extrusion, it has surprisingly been found that known green-mortar additives for liquefying and/or pla~ticizing can be added to the mixing water, to the liquid h~rdener and/or to the pasty compound. Such additives include lignosulfonates, melamine formaldehyde condensate sulfonates, naphthalene formaldehyde condensate sulfonates, tensides, abietic acid derivatives, and certain hydrolyzed proteins.
The additives generally amount to 5% with reference to the binder weight.
In order to stabilize a high insulating resistance during and/or in the use of the compounds according to the invention any existing hygroscopicity can be eliminated by furnishing hydrophobicity. Nonpolar organic compounds, metallo-organic, silico-organic and inorganic compounds are suitable for providing hydrophobicity. The water-repelling agents most often used include salts of aluminum and zirconium, complex chromium salts, silanes, silicones, and perfluorinated organic compounds insofar as no conductivity can develop under conditions of relative humidity. Silanes and/or silicones are particulàrly preferred, since they can be at least partially - integrated in the binder matrix as compounds of the same family.
But hydrophobicity can also be achieved by increasing the concentrations of alkaline earth cations in the compound compositions or by means of subsequent impregnation with alkaline earth oxides or the like. Calcium compounds which, i~
~ 17 ~, : ., , ., , : .
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, among other things, react with the still reactive silicates to form insoluble calcium silicates are particularly effective and ~conomical.
Ac¢ording to the invention, the intimate, homogeneous mixture o the starting components sio2 and water-containing siliaates and the necessary additives with water is mixed to form a paste until a deformable consistency is achieved or the starting components are first processed with water and the `~
necessary additives are then added while forming a flowable, pasty consistency, and the compound is then hardened after deformation as required. The hardening compounds can also be applied on a carrier material of metallic, inorganic or organic work materials and then harden. Such carrier materials can be steel, iron, wood, stone, concrete, plastics such as duroplastics or thermoplastics, or the like.
When producing the compact compound for insulation, the compound can be degassed by vacuum beforehand. But gas can also be removed from the pre-formed cast articles or in coatings by shaking or evacuation.
The water or an aqueous, alXaline medium can be used e.g.
in amounts of 5 to 70 percent by weight, preferably 20 to 50 percent by weight, in relation to the total dry compound.
The compounds which are mixed with water to form a paste can be processed by casting, extrusion, injection molding and pressing~
. .
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In the production of compact sealing and embedding compounds the hardening time is approximately 1 to 2 hours at ~5'C, wherein an exothermic polycondensation is used. This i5 ~ollowed by after-drying at 20 to 50C until a constant weight is achieved so as to expel the residual retained water.
If the sealing and emb~dding compounds are to be used at higher temperatures, they are heated by stages to temperatures of +80C to 1500C, wherein an after-hardening can be observed. Generally, for high- temperature applications it is necessary to heat in stages beyond the operating temperatures in order to achieve a good resistance to temperature and a good dimensional stability.
In the absence of additional energy resources for hardening and for forming the binder matrix according to the invention, as is the case e.g. in on-site assembly, the hardening reactions can also be carried out at temperatures >
10C, particularly 15 to 30C, by adding so-called hardening accelerators. Suitable hardening accelerators are anhydrous ; alkaline earth oxides such as quick lime, aluminum phosphates and the above-mentioned clinker phases, high-alumina cements, anhydrides, gypsum and possibly metal hydrides, as has been discovered according to the invention, insofar as they cause a reaction heat of 2 500 joules/g when in contact and/or in solution with water.
In the production of porous sealing and embedding compounds, the compounds harden at 20C in a maximum time of 2 :: :
hours or at 50C in approximately 1 hour. After-hardening can be effected at ~50 to +100C. If the porous sealing and embedding compounds are likewise provided for use at high temperatures, a stepwise heating to temperatures up to 1100C
is also e~fected.
The sealing and embedding compounds can also be furnished with hydrophobicity if required. Silanes, polydimethoxy sllanes or the like are suitable for this purpose.
Because of the low processing temperatures, the inorganic agents according to the invention, provide an extremely wide range of variations for production of the binder matrix, one reason being that all of the additives mentioned above, as well as other additives, can be integrated into the structural matrix in a simple manner. .
On the basis of the binder matrix according to the invention, the person skilled in the art is provided with a binding, inorganically based sealing and embedding compound intended for devices for protecting and connecting electrical circuits which is distinguished by the following advantages and advances, among others:
., .
- ease of processing - environmental and ecological friendliness `
- uncritical mixture ratios of the 2-component systems ~ . , - adjustable pot life and binding times - ability to process also at temperatures below 0C
..
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.
- binding in the presence of water - non-combustibility - extremely economical in comparison to sealing and embedding compounds based on organic polymers.
The properties of the set sealing and embedding compounds include:
- fast green strength and final strength, e.g. 30 minutes - non-combustibility, i.e. no development of flue gases - resistance to solvents, weak and strong alkalis, and sulfuric acid - surface hardness according to Mohs adjustable to 3 to 8 - volume weight in compact compounds: 1600 - 3500 kg/m3 in foam compounds : 200 - 1000 kg/m3 - flexural strength: adjustable between 10 - 40 MPa - compressive strength: adjustable between 20 - 100 MPa - E-module: 10,000 - 50,000 MPa - linear thermal expansion: 1 to 8 x 10-6/k-- high degree of vibration damping - lower creep behavior in comparison to organic sealing and embedding compounds - thermal dimensional stability - high resistance to ageing - high insulating resistance of > lOo M n.
In the device according to the invention for protecting and connecting electrical circuits, it follows from the above that the cavities between the electrical elements and between the device walls are filled with an insulating, inorganic ~aliny and embedding compound which can be processed in the presence of water without the water participating in the hardening reactions. Thus, the mixing water is only a vehicle as suspending agent and/or dispersing agent for transforming the solid components of the compound according to the invention into a processible, liquid aggregate state. The mixing water is to be removed from the hardened cast articles - usually by evaporation - after polycondensation (hardening).
While the rheological properties of the sealing and embedding aompounds according to the aforementioned compositions are sufficient in simpler construction of the device to achieve cast articles which are free of bubbles, it is considerably more difficult to cast complicated or angular housing constructions to cast cavities so as to be free of bubbles. Although the rheology of the compounds is partially improved by increasing the content of mixing water, this makes sealing and hardening more costly and time-consuming and does not provide a clean technical solution.
In a further development of the invention, the ; rheological processing characteristics of the sealing and embedding compounds which are mixed with water can be improved in a surprising manner with respect to viscosity, flow ' ~. '.
behavior and pouring behavior, etc., possibly accompanied by a ~imultaneous reduction in the mixing water requirement, by add~ng rheology-improving additives to the sealing and embedding compound which are based on alkali phosphates and/or ~lkali alkyl siliconates and their derivatives which take effect when mixed with water.
The backbone binding agents mentioned in the beginning include finely particulate sio2 and/or Al203 and originate from different sources. These are amorphous inorganic substances with a particle size of 100 um.
The further improved backbone binding agents belong to ~.~
the inorganic compounds whose practical applications rely to a great extent on their rheological characteristics which, amo;ng other things, are related to the following:
- the layer structure - the plate-shaped and/or spherical configuration - the negative charges - the variable structure at the particle edges - the cation and anion exchange capacity, and ~0 - the capacity to form different aggregates, suspensions and colloidal dispersions in aqueous systems.
Although the rheological behavior of suspensions or dispersions of the backbone binding agents according to the invention can be described in qualitative terms, they have so ~ . . : ,: , .
far successfully resisted any mathematical treatment.
Surprisingly, it has been found that the alkaline earth ions, preferably Ca~ ions, have a decisive influence on rheological characteristics when the backbone binding agents according to the invention are mixed with water, particularly in the case of m-kaoline. They influence the peptization and accordingly determina the required amount of mixing water for achieving low viscosities and good flow and pouring properties.
Surprisingly, it has now been found that thinner . .
suspensions and dispersions of the backbone binding agents according to the invention and water are obtained when alkali ions, e.g. Na~ ions, are added to the mixing water. A pH of 7.0 is particularly advantageous so that the positive edge charges and edge (+)/ surface (-) contacts are prevented.
Water glasses etc., which are present according to the invention in any case, are used for peptization.
However, the supply of or increased concentration (pH) of alkali ions is not sufficient in itself for increased ` liquefaction, since the negative edge charge density is not increased simultaneously. Surprisingly, it has been found that alkali phosphates and/or alkali alkyl siliconates ::
according to the invention are suitable for enhancing the peptization and increasing the edge charge density so as to ;
achieve thinner-liquid sealing and embedding compounds. The alkali alkyl siliconates set in the presence of C02, among others, to form the polyalkyl silicic acids according to the invention, since the latter impart additional hydrophobic characteristics to the hardened compounds.
These additives of alkali phosphates and/or alkali alkyl silioonates according to the invention not only liquefy the ~ealing and embedding compounds, but also simultaneously reduce the requirement of mixing water without thereby changing the improved rheological properties.
The following alkali phosphates, alkali alkyl siliconates and their derivatives, as well as mixtures thereof, are suitable as additives according to the present invention which improve the rheological properties.
According to the invention, the alkali phosphates are meta-phosphates, ortho-phosphates and/or polyphosphates. The : sodium phosphates and/or potassium phosphates, particularly the sodium polyphosphates and potassium polyphosphates, are particularly preferred.
; ~he alkali alkyl siliconates contain an alkyl group with : 1 to 11 carbon atoms, wherein the sodium alkyl siliconates and/or potassium alkyl siliconates whose alkyl group is a methyl group, ethyl group, propyl and/or butyl group are preferred.
Mixtures of both groups of additives are particularly preferred because - alkali phosphates bring about the higher li~uefaction capacity and - by way of hardening, the alkali alkyl siliconates form . ~ .
`~ 25 ~.. . . , ~ , -. ;. , polyalkyl silicic acids which make the hardened compounds hydrophobic.
All additives are soluble in water at a pH of 7Ø
The added quantities of the additives according to the invention can fluctuate within a wide range. The amounts of these additives contained in the sealing and embedding compounds mentioned in the beginning are determined by the liquefaction capacity relative to the compound compositions and by the required hydrophobicity in the hardened compounds.
In general, the added amounts in relation to the total solids content of a compound according to the invention are - 10.0 m-%, particularly 5.0 m-~, for alkali phosphates and - 50.0 m-%, particularly 25.0 m-~, for alkali alkyl siliconates.
If the additives are in liquid form, they are added to the hardener, insofar as the latter is a liquid water glass.
In all other applications, the additives are mixed in with the -~
backbone binding agents homogeneously.
After the addition of mixing water, the sealing and embedding compounds which are modified by these additives are stable, pumpable, thin-liquid suspensions or dispersions having a relatively high solids conten~.
` ` ' :
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~ ~ $ ~ ~ t ~ , The additives also convert the polyvalent cations present in the mixing water, e.g. MgZ', CaZ~, Al3+, into water-soluble complexes so as to prevent, in addition, a flocculent and rapid precipitation of backbone binder particles. This lengthens the processing time since the sealing and embedding compound formulation remains homogeneous for a longer time.
The invention is not limited by the embodiments described above which are presented as examples only but can be modified in various ways within the scope of protection defined by the appended patent claims.
",
Claims (43)
1. A device for protecting or for connecting electrical circuits, the device including a housing having at least one opening for receiving at least one cable comprising electrical lines and at least one additional opening enabling the production of fixed or detachable connections to connection or control lines via the electrical lines, the housing being filled with an insulating sealing and embedding compound, wherein, for ensuring a high resistance to temperature and protection against short-circuiting even at extremely high temperaturesand with a high insulating resistance, the sealing and embedding compound has a binder matrix comprising as chief constituent a hardened mixture of the components a) finely particulate SiO2, and b) at least partially water-soluble silicates
2. The device according to claim 1, wherein the ratio of components a) : b) is 80 to 20 : 5 to 60.
3. The device according to claim 1, wherein component a) of the mixture is a mixture of finely particulate SiO2 and Al2O3.
4. The device according to claim 3, wherein the weight ratio of SiO2 : Al2O3 is 5 - 98 percent by weight SiO2 : 95 - 2 percent by weight Al2O3.
5. The device according to claim 4, wherein the weight ratio of SiO2 : Al2O3 is 5 - 80 percent by weight SiO2 : 95 - 20 percent by weight Al2O3.
6. The device according to claim 1, wherein component a) contains dusts selected from the group consisting of dusts from high-temperature smelting processes, filter dusts, electrostatic filter ash from high-temperature nuclear reactors, and calcinated bauxites.
7. The device according to claim 1, wherein component a) comprises dehydrated aluminum silicates.
8. The device according to claim 1, wherein component a) of the mixture contains at least partially insoluble SiO2 from amorphous, water containing silicic acids in the form of dispersed powder.
9. The device according to claim 1, wherein component a) of the mixture contains at least one of anhydrous oxides of the elements of the second principle group of the periodic system and clinker phases from cement production.
10. The device according to claim 9, wherein the mixture contains alite and tricalcium aluminate.
11. The device according to claim 1, wherein the partially water-soluble silicates in component b) are alkali silicates or ammonium silicates.
12. The device according to claim 1, wherein the at least partially water-soluble silicates of component b) are provided in the form of alkali precursors or ammonium precursors.
13. The device according to claim 12, wherein the at least partially water-soluble silicates of components b) are provided in the form of solid alkali hydroxide in amorphous, water-containing silicic acid in the form of dispersed powder.
14. The device according to claim 11, wherein the molar ratio of alkali or ammonium to silicon oxide is between 1 and 5 moles SiO2 per mole of alkali or ammonium.
15. The device according to claim 14, wherein the molar ratio of alkali or ammonium to silicon oxide is between 1.2 and 4 moles SiO2 per mole of alkali or ammonium.
16. The device according to claim 1, wherein, in addition to components a) and b), the sealing and embedding compound contains a component c) comprising salts of fluorosilicic acid organic fluorosilicates in the hardening mixture.
17. The device according to claim 16, wherein the added component c) consists at least partially, of the salts of fluorosilicic acid of the general formula MI2 SiF6, wherein MI is a univalent metal.
18. The device according to claim 1, comprising inorganic, silico-organic and organic filler materials which are free of or low in heavy metals as additives.
19. The device according to claim 18, wherein the inorganic filler materials are selected from the group consisting of silica sand, quartz powder, wollastonite, mica, talc, barium sulfate, and calcium sulfate.
20. The device according to claim 18, wherein the silico-organic filler materials are inert, polymeric silicon compounds which are free of heavy metals.
21. The device according to claim 18, wherein the organic filler materials are polycondensates from the group consisting of duromers containing phenol resin, melamine resin, urea resin, polyimide resin.
22. The device according to claim 18, wherein the additives are micro-cavities with densities of 1.0 g/cm3 and particle sizes of 5,000 um.
23. The device according to claim 1, wherein inorganic or organic fibers are contained as additives in the compound and are selected from the group consisting of glass fibers, rock wool, aluminum silicate fibers and aluminum oxide fibers, ceramic fibers, silicon carbide fibers, polyamide fibers, polyacrylnitrile fibers, polyester fibers, phenol fibers, aramide fibers, cotton, cellulose fibers.
24. The device according to claim 23, wherein the additives consitute 1 to 95 percent by weight of the compound.
25. The device according to claim 1, comprising foam-forming components which release gases when coming into contact with water.
26. The device according to claim 1, wherein the compound is selected such that the hardening causes an accelerating bonding and a reaction heat of 500 joules/g when in contact or in solution with water and is from the group of anhydrous oxides of the elements of the second principle group of the periodic system, clinker phases, aluminum phosphates and the group of metal hydrides.
27. The device according to claim 26, wherein the clinker phases are alite C3S and tricalcium aluminate C3A.
28. The device according to claim 1, further comprising characterized in that lignosulfonates, melamine aldehyde condensate sulfonates, naphthalene aldehyde condensate sulfonates, tensides, abietic acid derivatives, and hydrolyzed proteins are provided for reducing the binder/water ratio, for liquefying and/or plasticizing.
29. A process for producing a device for protecting or for connecting electrical circuits, the device including a housing, the process comprising filling the housing with an insulating ceiling and embedding compound, producing the compound by forming an intimate homogenous mixture of the components a) finely particulate SiO2, and b) at least partially water-soluble silicates, mixing the components a) and b) with water to form a paste until a pourable or deformable consistency is reached, processing the mixture and finally hardening the mixture.
30. The process according to claim 29, further comprising adding to the mixture salts of flurosilicic acid or organic flurosilicates.
31. The process according to claim 29, comprising hardening the mixture at temperatures between 10°C and 120°C.
32. The process according to claim 31, comprising hardening the mixture at temperatures between 50°C and 120°C.
33. The process according to claim 31, comprising after-baking the hardened compounds in stages to temperatures above operating temperature.
34. The process according to claim 31, comprising adding water-repelling agents to the mixture forming the compound in order to stabilize a high insulating resistance.
35. The process according to claim 34, comprising using organic, metallo-organic, silico-organic and inorganic compounds for providing hydrophobicity.
36. The process according to claim 35, wherein salts of aluminum and zirconium, complex chromium salts, silanes, silicones, and perfluorinated organic compounds are used as water-repelling agents.
37. The process according to claim 34, comprising increasing concentrations of alkaline earth cations in the compositions.
38. The process according to claim 34, comprising impregnating the mixture with alkaline earth oxides.
39. The device according to claim 1, wherein the mixture further comprises alkali phosphates or alkali alkyl siliconates for improving and modifying a) the processing rheology in the presence of water and b) hydrophobicity after hardening.
40. The device according to claim 39, wherein the alkali phosphates are meta-phosphates, ortho-phosphates or polyphosphates.
41. The device according to claim 40, wherein the alkali phosphates are sodium salts and potassium salts of meta-phospates, ortho-phosphates or polyphosphates.
42. The device according to claim 39, wherein the alkali alkyl siliconates contain an alkyl group with 1 to 11 carbon atoms and in particular are sodium salts and potassium salts.
43. The device according to claim 39, wherein the alkali alkyl siliconates are sodium salts and potassium salts.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DEP4220317.1 | 1992-06-22 | ||
| DE19924220317 DE4220317A1 (en) | 1992-06-22 | 1992-06-22 | Device for protecting or connecting electrical circuits |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2098897A1 true CA2098897A1 (en) | 1993-12-23 |
Family
ID=6461505
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2098897 Abandoned CA2098897A1 (en) | 1992-06-22 | 1993-06-21 | Device for protecting and connecting electrical circuits |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0575839A3 (en) |
| JP (1) | JPH0714633A (en) |
| CA (1) | CA2098897A1 (en) |
| DE (1) | DE4220317A1 (en) |
| FI (1) | FI932890A (en) |
| NO (1) | NO932139L (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107325561A (en) * | 2017-07-11 | 2017-11-07 | 芜湖市宝艺游乐科技设备有限公司 | It is a kind of can porcelain polyimide fiber silicon rubber composite material and preparation method thereof |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE102004006563A1 (en) * | 2004-02-10 | 2005-09-01 | Aksys Gmbh | Inorganic-organic hybrid foam, is formed by mixing inorganic reactive components, a hardener, a foaming agent, a silicon compound and a tenside, followed by hardening |
| DE102009029942A1 (en) * | 2009-06-19 | 2010-12-30 | Günther Spelsberg GmbH & Co. KG | Fire protection clamp |
| DE102018216355A1 (en) * | 2018-09-25 | 2020-03-26 | Robert Bosch Gmbh | NTC resistance module |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5919905B2 (en) * | 1980-03-07 | 1984-05-09 | 品川白煉瓦株式会社 | Fireproof insulation board |
| JPS60238369A (en) * | 1984-05-11 | 1985-11-27 | Kimio Ishimaki | Method of forming protecting film on mold |
| JPS60239370A (en) * | 1984-05-11 | 1985-11-28 | 石巻 貴美雄 | Manufacture of refractory heat-insulating castable |
| DE4009998A1 (en) * | 1990-03-28 | 1991-10-02 | Hilti Ag | MASSES USED IN THE PRESENCE OF WATER, THEIR USE AND METHOD FOR THE PRODUCTION OF FORM BODIES FROM SUCH MASSES |
-
1992
- 1992-06-22 DE DE19924220317 patent/DE4220317A1/en not_active Withdrawn
-
1993
- 1993-06-11 EP EP19930109407 patent/EP0575839A3/en not_active Withdrawn
- 1993-06-11 NO NO932139A patent/NO932139L/en unknown
- 1993-06-21 CA CA 2098897 patent/CA2098897A1/en not_active Abandoned
- 1993-06-22 JP JP19157693A patent/JPH0714633A/en active Pending
- 1993-06-22 FI FI932890A patent/FI932890A/en not_active Application Discontinuation
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107325561A (en) * | 2017-07-11 | 2017-11-07 | 芜湖市宝艺游乐科技设备有限公司 | It is a kind of can porcelain polyimide fiber silicon rubber composite material and preparation method thereof |
Also Published As
| Publication number | Publication date |
|---|---|
| DE4220317A1 (en) | 1993-12-23 |
| JPH0714633A (en) | 1995-01-17 |
| FI932890A0 (en) | 1993-06-22 |
| NO932139L (en) | 1993-12-23 |
| EP0575839A3 (en) | 1994-05-25 |
| NO932139D0 (en) | 1993-06-11 |
| FI932890A (en) | 1993-12-23 |
| EP0575839A2 (en) | 1993-12-29 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |