MXPA97002306A

MXPA97002306A - Silicon sealant material that exhibits high tens relaxation

Info

Publication number: MXPA97002306A
Application number: MXPA/A/1997/002306A
Authority: MX
Inventors: Chiotis Achilles; Wojtowicz Janusz
Original assignee: Raychem Corporation
Priority date: 1994-09-30
Filing date: 1997-03-26
Publication date: 1997-06-01

Abstract

The present invention relates to a sealant composition comprising: divinyl-terminated dimethylsiloxane having a viscosity of about 10,000 to about 500,000 centistokes, a non-reactive polydimethylsiloxane diluent having a viscosity of about 250 to 2,000 centistokes, a platinum catalyst in an amount of 3 to 20 parts per million and 0 to approximately 250 parts per million of inhibitor and a multifunctional interleaver in the amount of from about 0.6 to about 0.65%; the final composition also includes a filling in an amount of 10% to 20% of the composition and has a hardness of about 6 to 20 grams, a tack of about 17 to 35 grams and a tension relaxation of about 45% to 9 grams.

Description

SILICON SEALANT MATERIAL THAT EXHIBITS HIGH TENSION RELAXATION Technical Field of the Invention This invention relates to gel sealant materials. More specifically this invention relates to a gel sealant material having a high stress relieving which allows it to effectively seal two wires that enter the rear end of a double wire connector. BACKGROUND OF THE INVENTION The permanent sealing of wires at the rear end of the connector can be achieved with epoxies or other fast curing adhesives. However, differences in the thermal expansion properties of the adhesive and the jacket of the wire can cause ruptures or fractures in the capillary line, which would allow moisture to enter the connector and cause corrosion. Sealing wires that enter a connector where re-entry is necessary, creates additional problems. You can use mastics or fats but these are dirty and / or flow at higher temperatures. The effective seal wherein the re-entry is a requirement or is convenient, can be achieved by the use of gel sealant materials as described in the U.S. Patents. 4,600,261; 4,680,233; 4,777,063 and 5,079,300. All of these preceding patents are fully incorporated herein by reference for all purposes. These gel sealants are interlaced polymer solids extended with a non-reactive fluid extender. Alternatively, the gels can be an interlaced system which includes an excess of a reactive fluid such as the vinyl group material so that it acts as an extender. as exemplified by "Sylgard 527®" and taught in U.S. Patent 3,020,260, the disclosure of which is incorporated herein by reference for all purposes. The gel maiepal is a substantially dilute system that exhibits flow in an unstable state. is discussed by Ferry, a polymer gel is then an interlaced solution this or not interlaced by chemical bonds or cpstalites or some other kind of bonding The absence of steady state flow is the key definition of solid-like properties while it is necessary Substantial dilution to give the relatively low modulus of gels Solid nature is achieved by an microscopically continuous network structure formed in the material generally through the entanglement of the polymer chains through some kind of binding or the creation of domains of associated substituents of various branched chains of the polymer The crosslinking can be both physical and chemical while the entanglement sites are maintained under the conditions of use of the gel LOS gels produced by mixing styrene-styrene-ethylene-styrene-styrene (SEBS) and styrene-ethylene-propylene-styrene (SEPS) etc copolymers and paraffinic oils are comprised of styrenic microspheres of glass interconnected by an extended elastomer phase of fluid. Stretched domains separated by microphases serve as the junction points in the systems SEBS and SEPS gels are examples of thermoplastic systems While, the sihcon gels of the present invention are examples of thermosetting gels. This class of gels are chemically entangled by the use of a multifunctional interlacing agent. Although the silicone gels described in the patents and pamphlets referred to above have shown that they effectively seal a wide variety of articles, they often arise. difficulties when it comes to sealing two thin wires generally in the caliber found in automotive connectors where the wires are located in close proximity such as in the rear end of a connector Therefore, it would be highly convenient to have the benefits and ease of use of a gel sealant material with preferred sealing characteristics for use with double or multiple wires, for example, in an automotive connector where the wire gauges are between 18 gauge wire and 26 gauge. Compendium of the invention The invention provides the convenient aspects mentioned above as well as many other obvious advantages for the ordinarian with ordinary experience. More specifically, has discovered that a silicone gel having a strain relief greater than about 50%, provides an effective gel sealer for dual or multiple wire applications, for example, at the rear end of automotive connectors. In particular, the gel sealant material could also have a Voland hardness of about 6 grams to about 20 grams, a tackiness of about 17 grams to about 35 grams, and a tension relieving greater than 45% and approaching 95%. Additionally, the invention provides a connector having a plurality of wires that enter thereto and are sealed with the composition of the invention. The design of the connector could exert an initial pressure on the gel greater than about 0.35 kg / cm2, preferably greater than about 1.05 kg / cm2, and more preferably Die greater than about 1.75 kg / cm2. DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred gel sealant material for sealing narrow double or multiple wires that enter the rear end of a connector such as an automotive connector is an organopolysiloxane composition. The appropriate tension relieving properties can be achieved, at least, by two ways, namely the addition of fillers such as zinc oxide (ZnO) or filler material similar to a "Raychem" gel known as T-894. . The filler material is present in an amount of more than 5% but less than about 20% and preferably from 7.5 to 15% and more preferably from 10 to 13%. It was quite unexpected that a material having the desired stress relieving properties, but similar properties in terms of hardness and tackiness to non-filling materials, could be achieved by the use of an additive. Other suitable fillers added could be barium oxide, AI (OH) 3, T02 and other similar oxides. A preferred scale of Voland hardness is from about 6 grams to about 20 grams, a pergajosity of about 17 grams to about 35 grams. Additionally, the elongation of the gel is greater than about 200% and preferably greater than about 400%, more preferably greater than about 750%. More generally, the greater the elongation without sacrificing the relaxation of tension and other properties, the better. Alternatively, properly tensioned material can be made without fillers by adjusting the starting components. The elongation is measured according to the procedures of ASTM D638. Voland's hardness, stress relieving and stickiness, are measured using a Voland-Stevens textural analyzer model LFRA or similar machines that have a 5,000 gram load cell, a 5 gram driver and a 6.35 mm ball probe as is described in the EUA patent 5,079,300, the description of which is hereby fully incorporated by reference for all purposes. For example, by measuring the hardness of a gel, a vile 20 ml glass scintillation with about 10 grams is preferred, but 13 grams of gel placed in the Stevens-Voland texture analyzer and the stainless steel probe ball are preferred. It is forced into the gel at the speed of 0.2 mm per second, a penetration distance of about 4.0 mm. The hardness e Voland of the gel, is the force in grams required to force the ball probe at that speed to penetrate or deform the surface of the gel specified for 4.0 mm. Higher numbers mean harder gels. The stickiness and tension relaxation are read in the voltage curve generated by the recorder. When the recorder is on, automatically traces the force against the time curve experienced by the load cell. The withdrawal penetration speed is 2.0 mm / sec with a graph speed of 5 cm / sec. Stickiness is the amount of force in grams that resists in the probe as it is pulled out of the gel. The units of force depend on the setting in selected millivolts. A setting of 2 millivolts corresponds to 100 grams in full scale. 5 miiivolts is 250 grams full scale and so on. The width of the graph is 25 cm. The force units are determined by dividing the calibration weight in the appropriate V setting for 25 cm. For example, if the recorder is calibrated in full scale of 100 grams, multiply the value measured in centimeters by a factor of 4, ie (100 g / 25 cm) to determine hardness while measuring the tension tack and relaxation of the paper of the graph.

With respect to the global distance of the movement of the distance of 4 mm, it is measured from the moment in which the probe feels 5 g of force applied to it (5 g operating point). If a softer gel is tested, the probe can penetrate the gel to the initial depth of approximately 2 mm before it detects 5 grams. Once the driving point is reached, a distance of 4 mm is measured. As you can see, the total depth of? It can be different than 4 mm. Stress relaxation is the ratio of the initial force (F,) (also known as maximum force (H)) resisting the probe to a preset depth of penetration minus the strength of the probe force (Ff) after 1 min (also known as equilibrium force (L)) divided by F ,. More specifically, the percentage stress relaxation is equal to (F, -Ff) / F,) x100 where F, and Ff are gm read in the graph in cm and where the tack T is equal to T? XFactor for T ? equal to mm, read on the graph as a time factor, eg, 4 g / cm at 2 mV, 10 g / cm at 5 mV and 20 g / cm at 10 mV. In other words, tension relaxation is the ratio of the initial force minus the force after one minute on the initial force. It is a measure of the ability of the gel in essence to relax any induced compression placed on the gel by the initial installation of the wires and / or material test. More specifically, the hardness is equal to the maximum force recorded by the probe. The stickiness is the adhesive force between the gel and the probe when it is removed The tension relaxation is a ratio of the difference between the maximum force (H) and the equilibrium force (L) after sixty seconds at the maximum force ((HL) / H) x100% The high stress relaxation gel is generally manufactured by a two-part precursor system of part A, which comprises approximately 72% of 1,000 centistokes of polydimethylsiloxane fluid material as a diluent / extender of approximately 020 % of finished tetrafunctional vinyl parts with about 0200% inhibitor of platinum vimlo-terminated pohdimethylsiloxane complex catalyst and about 27 5% of a non-reactive divinyl-terminated PDMS of 170KCS Part B is about 72% of a material similar to the first part in Part A Approximately 0 1% of an interleaver finished with tetrafunctional hydride and approximately 275% of PDMS polymer of div 170 KCS inilo The suitable materials are available from places such as "Dow", "GE", "Union Carbide", "Hulls", "Nusil", etc. The vimlos and catalysts preferred with "CAT-50", "PC075" , "Ply 7520", "TRV 633" These parts are then mixed so that the final composition is from about 7 5% to about 20% ZnO with the remainder being the combination of parts A and B and preferably about 10%. to 13% ZnO with the remainder being silicone Alternatively, the material of high stress relaxation can be achieved through direct adjustment of the initial materials in the absence of filler This is a particularly preferred solution since the filler is not always mixed uniformly throughout the material, thus giving a variation of properties while a material in the absence of filler is more apt to have uniform properties through it The components of a directly mixed matepai, will use a dil finished with pol? (d? met? l? loxane) -tpmethylsiloxy in the amount of about 30 to 70% by weight The diluent preferably has a viscosity of between 25 to 2,000 centistokes The active vimio group is a pol? (d? metiloxane) loxane terminated with divimlo having a viscosity of about 10,000 to about 500,000 centistokes and is present in the amount of about 70 to about 30% by weight Approximately 3 to 20 parts / million of catalyst are used of platinum and depending on the healing regimen, an inhibitor of 0 to 250 parts, and multifunctional interleaver of approximately 0.6% to approximately 065% is used to provide a gel having a hardness of 6-20 g, tackiness of 17-35 g, and stress relieving of 45-95%. preferably, the non-filler material is a divinyl-terminated pol? (d? met? loxane) having a viscosity of about 50 to 175 mil centistokes and is present at about 30 to 70 wt.% in a diluent of approx. 40 to 1000 centistokes, is present from 70 to 30% by weight The platinum catalyst is from about 5 to 15 ppm with an inhibitor of about 50 to 100 ppm and tetrafunctional interlaced in the amount of about 062% to 0 (33% for provide a gel having a hardness of 7-16 g, tackiness of 20 to 35 g, and tension relaxation of 50-80% A particularly preferred composition is about 45% of pol? (d? met? l? loxane) terminated with divinyl having viscosity of about 7 2,000 to approximately 90,000, a diluent finished with pol? (D? Met? L? Loxane) tpmet?! S? Lox? having a viscosity of about 45 to about 55 centistokes and present in an amount of about 55%, about 03% by weight of platinum catalyst, about 06% by weight of crosslinker and an inhibitor of about 0 15% by weight. Particularly preferred material produces a gel having a hardness between about 8 and 12 grams with a tack of 25 to 30 grams while exhibiting a stress relieving of 65 to 75%. The CD compositions of the invention are used by mixing parts A and B together and filling the back end of the connector and allowing the articles to cure After using thin gauge wires such as automotive wires having a gauge between about 14 and 28, they are inserted through the gel on the back of the connector and sealed effectively in the same In the absence of a material of high tension relaxation, it is a problem and sealed between the wires that they touch or almost touch each other, due to what are known as covering or triangulation leak paths that occur in the interface between the wires. An example of a particularly suitable connector appropriately modified to seal double wires in close proximity is described in the "SEALING MEMBER" patent of E.U.A. No. 08 / 221,728 filed on April 1, 1994, the description of which is fully incorporated in the present reference for all purposes. The most preferred configuration is a gel layer of about 3.0 to about 6.0 mm thick sandwiched between two layers of crosslinked polyurethane of approximately 1.5 mm thickness. The polyurethane layers serve to facilitate the handling of the sealing gel. This structure can seal wires with many different insulation sleeves such as polyethylene, PVC, "Kynar®", polyester and the like. The initial closing pressures of at least 0.35 kg / cm2, preferably 1.05 kg / cm2, and more preferably 1.75 kg / cm ", ensure an adequate seal of wires.Therefore, the high tension relaxation allows the gel The assumption assumes the seal and retains the contact with the wires in the connector.The intention will be illustrated particularly by the following examples of the modality.

EXAMPLES T-894 is a two-part polyorganosiloxane gel material. 100 gram portions of part A and part B were mixed. Part A comprises about 72.4 grams of a 100-fold polydimethylsiloxane fluid, 0.1 grams of a tetrafunctional hydride terminated crosslinker, and about 27.5 grams of a polydimethylsiloxane terminated with Divinil of 170 KCS. Part B includes substantially similar amounts of diluent and divinyl fluid without the hydride interleaver, but also includes about 0.02 grams of tetrafunctional vinyl terminated inhibitor and 0.1 gram of platinum / vinyl terminated polydimethylsiloxane catalyst complex.

These materials were mixed in equal parts together with the ZnO and blue color and placed on the back of an automotive connector was allowed to cure The formulations of Examples 1-6 were tested on an automotive wire connector of 10 18 gauge shapes The materials of Examples 3, 5 and 6, effectively sealed the connector through a thermocyclic series ranging from -40 ° C to + 125 ° C followed by an emersion of water, while the low-tension release formulations of Examples 1, 2 and 4 failed the tests This example was based on the percentage by weight Approximately 45% by weight of a divinylc "RTV633" 90 kCS divinylc pohdimethylsiloxane was mixed with about 55% by weight of a diluent finished with (pol? d? met? s? loxane) tr? met? l? lox? 50 centistokes "Amersil L45", approximately 0029% by weight of divinyltetramethylsiloxane platinum catalyst "PC75", approximately 063% by weight tetrafunctional hydride terminated "UCT-1915" and approximately 0-15% by weight of inhibitor 1, 3,5,7-tetravinylmethylcyclotetrasiloxane "T2160" The material had a hardness of about 8 to 12 grams, a stickiness of 25 to 35 grams and a stress relieving in the order of about 65 to about 75%. The composition provided a material Effective Sealing for a Multi-Wire Connector While the invention has been described with respect to the particularly preferred embodiments, modifications that would be obvious to someone with ordinary experience in the field such as formulations are contemplated within the scope of the invention. alternatives to achieve the properties of hardness, tackiness and relaxation of tension desired.

Claims

CLAIMS 1 A sealant composition comprising divinyl-terminated dimethylsiloxane having a viscosity of about 10,000 about 500,000 centistokes, a non-reactive pohdimethylsiloxane diluent having a viscosity of about 250 to 2,000 centistokes, a platinum catalyst in an amount of 3 to 20 parts per million and from 0 to about 250 parts per million of inhibitor and a multifunctional crosslinker in the amount of about 06% to about 065% so that the final composition has a hardness of about 6 to 20 grams, a tack of about 17 to 35 grams and a strain relief of about 45% to 90% 2 The composition according to claim 1, wherein the diviminated-terminated polydimethylsiloxane has a viscosity of about 50,000 to about 175,000 centistokes, the diluent is about 40 to 1,000 centistokes, the platinum catalyst is The present invention has a composition of about 5 to 15 ppm, and the composition further includes about 50 to 200 ppm of inhibitor and crosslinker. The composition according to claim 2, wherein the diluent is a fluid terminated with (pol? d? l5-oxoan) tr? met? lox ?, the catalyst is a platinum of divinyltetrarnetildisiloxane containing catalyst and the inhibitor is 1, 3,4,7-tetrav? n? ltetramet? lc? clotetras? loxane and tetrafunctional interleaver in an amount of about 063% so that the gel has a hardness of about 8 to 12 grams, a tack of 25 to 35 grams with a tension relax of about 65 to 75% 4. the composition according to claim 1, including a filler in an amount of about 10% to about 20% of the composition The composition according to claim 3, wherein the composition is cured in a multi-wire connector 6 An automotive connector comprising a p rear part in which multiple wires and a front portion capable of coupling with a connector enter, the rear end portion of the connector containing an effective sealing amount of a polyorganosiloxane silicone gel having a hardness of about 6 to 20 grams, a tack of about 17 to 35 grams and a tension relaxation of about 45% to 95% The connector according to claim 5, wherein the tension relaxation is greater than 50% The connector according to claim 5, in wherein the gel includes from about 10% to about 20% of the filler 9 The connector according to claim 7, wherein the gel is a layer of about 3 to about 6 mm in thickness sandwiched between lattice layers of about 1.5 mm. 10. The connector according to claim 8, wherein the gel is a layer of about 3 to about 6 mm thick walled in between grid layers of about 1.5 mm.