RU2748798C1 - Composite polymer material for sealing radio-electronic products - Google Patents

Abstract

FIELD: polymer composite materials.SUBSTANCE: invention relates to the field of polymer composite materials for sealing radio-electronic products, electronic products, communication technology, electrical products and systems. The invention relates to polymer composite material consisting of low molecular weight siloxane rubber, silicone oligomer, ethyl silicate. A mixture of silicon oxide selected from powdered quartz and cristobalite, aluminum hydroxide fractions of 2-5 mcm and 5-20 microns and wollastonite fractions of 3-5 mcm, optionally aluminosilicates represented by fine fractions of 2-5 mcm, optionally finely dispersed aluminum oxide fractions of 2-5 mcm is used as filler. The binder mixture consists of silicone rubber, ethyl silicate and silicone oligomer and is with the specified filler in a mass ratio, pts. wt.: binder: total weight of the filler - 100:(100-130). Cold curing catalysts based on organotin compounds and/or based on amines in amounts of 2-5 pts.wt. are used as a hardener per 100 pts. wt. of the binder.EFFECT: composite polymer material according to the invention provides an expansion of the technological possibilities of application when sealing complex small-sized articles, including small parts on their surfaces.1 cl, 3 tbl

Description

The invention relates to the field of polymer composite materials for sealing radio-electronic products, electronic products, communications technology, electrical products and systems. Composite polymer materials contain low molecular weight silicone rubbers, silicone oligomers and fine fillers as a base. First of all, these are oxides, hydroxides, carbides, nitrides of metals and non-metals. The mass ratio of the components that make up the claimed polymer composite material is: low molecular weight siloxane rubber - 100 wt. hours, fine fillers, including silicon dioxide - 150-300 mass. including, polymethylsiloxanes and ethylsilicates. The composite material according to the invention has the required degree of thermal conductivity with a sufficient level of technological and operational characteristics. This makes it possible to ensure reliable sealing of parts by the claimed composite polymer material of products and systems in the indicated fields of technology.

Requirements for electrical and mechanical properties are imposed on electrical insulating composite materials in combination with technological properties, such as low initial viscosity, a sufficient level of viability, rate of complete curing, as well as thermal conductivity in operating temperature ranges, which prevents overheating of sealed products and their failure. ...

Composite materials based on silicone elastomers have the most universal combination of such properties in terms of their composition and target application technology. They are fully described in literary, documentary and patent sources. The reference literature contains information about domestic and foreign sealants and compounds based on silicone rubbers, different in physical characteristics and molecular weight. Such information is posted in the sources: Encyclopedia of Polymers, T. 1. M .: Soviet Encyclopedia, 1972 (p. 783-784, p. 1011-1015, p. 1076-1082), as well as the Chemical Encyclopedia, T.l. M .: Soviet encyclopedia, 1988, p. 534-537; Chemical encyclopedia T. 2. (p. 438-439, p. 509-516).

A number of domestic and foreign materials for electrical insulation and high-voltage sealing are known, including a domestic material based on dimethylsiloxane rubber, an inorganic filler structured with tetraethoxysilane (USSR AS No. 128461). This material is cured with tin salts. Also known is a silicone-based potting composition containing kaolin and white carbon, cured with a mixture of ethyl silicate and tin octoate (USSR inventor's certificate No. 496293). These materials, with a satisfactory strength of vulcanizates, do not meet the technological requirements either in terms of the initial working viscosity, or in terms of curing rates and the time to achieve the required performance properties.

Known potting composition (USSR AS No. 730762) with satisfactory fluidity and adjustable thixotropy period, which is achieved by selecting the composition of fillers and allows, if necessary, to increase the poured layers of the composition in thickness. However, the significant initial viscosity of the composition prevents the defect-free filling of products with complex surface relief, containing internal channels. Similar technological disadvantages are inherent in some domestic sealants based on silicone rubbers (USSR AS No. 126175, USSR AS No. 905740), as well as their foreign counterparts (for example, Japanese application No. 58-157860).

Known domestic compositions, compounds and sealants are given in and.with. USSR No. 507607, and.with. USSR No. 731780, and.with. USSR No. 1623995, RF patent No. 2010820, RF patent No. 2028361, RF patent No. 2052475, RF patent No. 2105778, RF patent No. 2307758. Similar materials of foreign origin are known. With all the variety of these materials, their basis is liquid silicone rubbers with terminal silanol groups (domestic rubbers SKTN A, SKTN B, SKTN V, SKTN G, SKTNF, SKTNF-A, SKTNF-B, and their foreign analogues), as well as fillers, hardeners and plasticizers.

The main disadvantages of most of the known materials are often not always a sufficient and stable level of basic characteristics, as well as practical difficulties arising from the regulation of the curing rates in the conditions of technological application. The fillers included in their compositions, for example, titanium dioxide, are scarce and have a significant cost. On the other hand, the use of widespread and more commercially available fillers in some cases does not provide the necessary strength properties of vulcanizates of materials. A number of the above materials are not resistant to acidic reagents (for example, compositions containing calcium and magnesium carbonates), and their vulcanizates do not have the required level of physical, mechanical and dielectric properties.

Currently, there is a growing interest in autonomous power supplies for use in various branches of technology, including power supplies for special applications. They must remain operational in various conditions as part of complex functioning systems. Requirements for reliability and miniaturization are highlighted. Reliability requirements relate to both the initial and intermediate characteristics of the materials used for sealing, and their properties achieved at the end of the curing process. The correct technical solution associated with the choice of sealing material will overcome the problem of ensuring reliable performance with its required resource.

Known composite material (RF patent No. 2502772), close to the claimed. It contains as a base low molecular weight silicone rubber SKTN, as a hardener a mixture of tetraethoxysilane or its derivatives with an organotin catalyst, and the content of tetraethoxysilane or its derivatives reaches 20% of the total mass of the composite material. A certain tensile strength of the vulcanizate is achieved in combination with the filling properties of the composite material. However, the material with a low initial viscosity has low values of physical and mechanical characteristics in the cured state and is not suitable for solving a number of problems. At the same time, a significant excess of silane derivatives in the bulk does not provide it with the required stability of a number of operational properties, while the possibility of separating these products from the bulk of the vulcanizate at elevated temperatures remains.

Known compound KTK-1 (TU 2252-037-89021704-2013), used for filling products of radio and electrical equipment, consisting of low molecular weight silicone rubber, hardener and heat-conducting filler. With a value of the thermal conductivity coefficient of not more than 1.1 W / m * K, the compound demonstrates tensile strength at values of 0.6 MPa, as well as a relative elongation at break of not more than 30%. Thus, with a sufficiently high thermal conductivity, the compound is significantly inferior in its physical and mechanical characteristics to most composite silicone materials used today to solve sealing problems. This significantly limits the intended use of this compound.

There are also known analogues of the KTK-1 compound, a Russian manufacturer, produced by the STEP enterprise (St. Petersburg). They have similar characteristics, but, unfortunately, in terms of their cost characteristics, they are commercially available to a limited extent, which is the reason for their insufficient widespread use in technical fields.

An extensive group of heat-conducting materials for sealing is known, produced by the company "NOMAKON" (Belarus) according to TU RB 100009933.004-2001. In particular, these are compounds 1L-1.00; 1L-1.50; 1L-2.50 with a sufficiently high level of dielectric properties. The basis of the compounds consists of silicone binders (liquid rubbers), as well as finely dispersed heat-conducting fillers. However, the thermal conductivity of these compounds does not exceed the level of values of 0.60 W / m * K. In some cases, this may not be sufficient to ensure the reliable operation of those technical devices that emit significant amounts of excess heat.

The known composition and method of obtaining a sealing composition for products operating in conditions of high air humidity at high supply voltages. Information about the composition is given in the description of the RF patent No. 2472833. The sealing composition has the following composition: a compound based on low molecular weight silicone rubber in an amount of 100 wt. hours, polymethylsiloxane (PMS-50) with a kinematic viscosity of 10-350 mm ² / s - in the amount of 10-50 wt. hours, silicon dioxide with a specific surface of 50 to 300 m ² / s - in the amount of 10-40 wt. h. This allows you to provide the required mechanical characteristics and stability of electrical insulation properties in conditions of high humidity and high supply voltages. The result is achieved due to the claimed composition and the method of its preparation, including the removal of moisture when the base is heated, as well as the gradual degassing of a mixture of silicon dioxide with polymethylsiloxane. The disadvantage of this technical solution is the low thermal conductivity of the composition. With its high specific surface area, silicon dioxide cannot be introduced into the composition of the composition in the required amounts without significant deterioration of the technological properties of the sealing composition, in particular, without reducing its minimum required fluidity.

Known filled polymer composite material (RF patent No. 2686910), including low molecular weight siloxane rubber (100 wt. H.) And fine silica (400-580 wt. H.) As a filler, as well as polymethylsiloxane and ethyl silicate (total amount 25- 55 pbw). The main function of this material is to ensure high thermal conductivity of the material, 1.15-1.45 W / m ° K, with sufficiently high physical, mechanical and dielectric characteristics. The maximum filling of the polymeric binder with a heat-conducting filler causes a significant density and, more importantly, a significant initial viscosity of the composite material. This makes it almost impossible to use this material for sealing small in size and complex in profile parts and components that make up critical parts and assemblies (for example, electricity meters, computer and signaling devices). This requires materials with a significantly higher fluidity, which would allow reliable sealing of products, taking into account their small dimensions, the features of their complex profiles, the presence of narrow structural channels and recesses on the surfaces of products. At the same time, the filled polymer composite material according to RF patent No. 2686910 is in many respects similar to the claimed composite material in composition and properties, therefore, it is adopted as a prototype for the present invention.

The objective of the invention is to create a composite polymer material, which provides an expansion of the technological possibilities of application when sealing complex small-sized products, including small parts on their surfaces.

The solution to the problem is that, in contrast to the known filled polymer composite material, including low molecular weight siloxane rubber, polymethylsiloxane, ethyl silicate and finely dispersed silicon dioxide, the claimed composite material additionally contains finely dispersed aluminum hydroxide, finely dispersed wollastonite aluminosilicates, optionally finely dispersed aluminum oxides fine fractions, cold curing catalysts based on organotin compounds and / or based on amines.

The problem is solved due to the fact that a mixture of silicon oxide selected from ground pulverized quartz, cristobalite, aluminum hydroxide of fractions 2-5 microns and 5-20 microns and wollastonite fractions 3-5 microns, optionally aluminosilicates, represented by fine fractions 2 -5 microns, optionally finely dispersed aluminum oxide fractions 2-5 microns, and the binder mixture consists of silicone rubber and silicone oligomer, and is with the specified filler in a mass ratio, wt. h .: binder: total weight of the filler - 100: (100-130). As a hardener, catalysts are used in amounts of 2-5 wt. hours per 100 mass. h. binder.

Information about the components that make up the composite polymer material is given in Table 1.

Information on the quantitative and qualitative composition of the composite polymer material is given in Table 2.

Information on the main characteristics of the properties of the composite polymer material is given in Table 3.

The following are specific examples of obtaining a filled polymer composite material.

Example 1

100 g of SKTN brand A rubber is placed in a mixing container, 20 g of silicone oligomer PMS-50, 5 g of ethyl silicate ES-32 are added to this container and thoroughly mixed with rubber for 2-3 minutes. 50 g of ground pulverized quartz of grade B, 10 g of wollastonite, 40 g of aluminum hydroxide with a particle size of 2-5 microns, 30 g of aluminum hydroxide with a particle size of 5-20 microns, stirring occasionally. Mix and hold until the main amount of air inclusions comes out of the mixture volume. The mixture is transferred into a sealed container and kept closed for at least 24 hours. Immediately before use, 6 g of catalyst K-68 are added to the resulting filled polymer composite material and again thoroughly mixed.

Example 2

100 g of SKTN brand A rubber is placed in a mixing container, 20 g of silicone oligomer PMS-50, 5 g of ethyl silicate ES-40 are added to this container and thoroughly mixed with rubber for 2-3 minutes. 30 g of ground pulverized quartz of grade B, 10 g of cristobalite, 12 wollastonite, 6 g of Super series kaolin, 45 g of aluminum hydroxide with a particle size of 2-5 microns, 50 g of aluminum hydroxide with a particle size of 5-20 microns, periodically stirring. Mix and hold until the main amount of air inclusions comes out of the mixture volume. The mixture is transferred into a sealed container and kept closed for at least 24 hours. Immediately before use, 6 g of catalyst K-21 are added to the resulting filled polymer composite material and thoroughly mixed again.

Example 3

100 g of SKTN brand A rubber is placed in a mixing container, 15 g of silicone oligomer PMS-50, 10 g of ethyl silicate ES-40 are added to this container and thoroughly mixed with rubber for 2-3 minutes. 40 g of ground pulverized quartz of grade B, 8 g of wollastonite, 12 g of Super series kaolin, 30 g of aluminum hydroxide with a particle size of 2-5 microns, 55 g of aluminum hydroxide with a particle size of 5-20 microns, periodically stirring / Stir and hold until the main amount of air inclusions is released from the volume of the mixture. The mixture is transferred into a sealed container and kept closed for at least 24 hours. 6.5 g of catalyst K-68 is added to the resulting filled polymer composite immediately before use and again thoroughly mixed.

Example 4

100 g of SKTN brand A rubber is placed in a mixing container, 20 g of silicone oligomer PMS-20, 8 g of ethyl silicate ES-40 are added to this container and thoroughly mixed with rubber for 2-3 minutes. 50 g of ground pulverized quartz of grade B, 10 g of wollastonite, 4 g of kaolin of the "Standard" series, 5 g of cristobalite, 33 g of aluminum hydroxide with a particle size of 2-5 microns, 40 g of aluminum hydroxide with a particle size of 5-20 microns, are introduced into the resulting mixture. stirring occasionally. Mix and hold until the main amount of air inclusions comes out of the mixture volume. The mixture is transferred into a sealed container and kept closed for at least 24 hours. 4.5 g of catalyst K-21 is added to the resulting filled polymer composite immediately before use and again thoroughly mixed.

Example 5

100 g of SKTN grade A rubber is placed in a mixing container, 25 g of silicone oligomer PMS-50, 7 g of ethyl silicate ES-32 are added to this container and thoroughly mixed with rubber for 2-3 minutes. 55 g of ground pulverized quartz of grade B, 6 g of wollastonite, 10 g of Super series kaolin, 35 g of aluminum hydroxide with a particle size of 2-5 microns, 50 g of aluminum hydroxide with a particle size of 5-20 microns, stirring occasionally. Mix and hold until the main amount of air inclusions comes out of the mixture volume. The mixture is transferred into a sealed container and kept closed for at least 24 hours. Immediately before use, 5 g of catalyst K-68 is added to the resulting filled polymer composite material and thoroughly mixed again.

Example 6

100 g of SKTN brand A rubber is placed in a mixing container, 30 g of silicone oligomer PMS-20, 6 g of ethyl silicate ES-32 are added to this container and thoroughly mixed with rubber for 2-3 minutes. 30 g of ground pulverized quartz of grade B, 12 g of wollastonite, 15 g of cristobalite, 35 g of aluminum hydroxide with a particle size of 2-5 microns, 50 g of aluminum hydroxide with a particle size of 5-20 microns, stirring occasionally. Mix and hold until the main amount of air inclusions comes out of the mixture volume. The mixture is transferred into a sealed container and kept closed for at least 24 hours. Immediately before use, 6 g of catalyst K-68 are added to the resulting filled polymer composite material and again thoroughly mixed.

Example 7

100 g of SKTN grade A rubber is placed in a mixing vessel, 16 g of PMS-50 silicone oligomer, 10 g of ES-32 ethyl silicate are added to this vessel and thoroughly mixed with rubber for 2-3 minutes. 30 g of ground pulverized quartz of grade B, 10 g of wollastonite, 8 g of kaolin of the "Standard" series, 10 g of cristobalite, 40 g of aluminum hydroxide with a particle size of 2-5 microns, 38 g of aluminum hydroxide with a particle size of 5-20 microns, are introduced into the resulting mixture. stirring occasionally. Mix and hold until the main amount of air inclusions comes out of the mixture volume. The mixture is transferred into a sealed container and kept closed for at least 24 hours. Immediately before use, 5 g of catalyst K-68 is added to the resulting filled polymer composite material and thoroughly mixed again.

Example 8

100 g of SKTN brand A rubber is placed in a mixing container, 25 g of silicone oligomer PMS-50, 8 g of ethyl silicate ES-32 are added to this container and thoroughly mixed with rubber for 2-3 minutes. 30 g of ground pulverized quartz of grade B, 15 g of wollastonite, 10 g of cristobalite, 35 g of aluminum hydroxide with a particle size of 2-5 microns, 50 g of aluminum hydroxide with a particle size of 5-20 microns, stirring occasionally. Mix and hold until the main amount of air inclusions comes out of the mixture volume. The mixture is transferred into a sealed container and kept closed for at least 24 hours. Immediately before use, 5 g of catalyst K-21 is added to the resulting filled polymer composite material and thoroughly mixed again.

Example 9

100 g of SKTN brand A rubber is placed in a mixing container, 30 g of silicone oligomer PMS-50, 4 g of ethyl silicate ES-32 are added to this container and thoroughly mixed with rubber for 2-3 minutes. 60 g of ground pulverized quartz of grade B, 12 g of wollastonite, 20 g of cristobalite, 30 g of aluminum hydroxide with a particle size of 2-5 microns, 40 g of aluminum hydroxide with a particle size of 5-20 microns, stirring occasionally. Mix and hold until the main amount of air inclusions comes out of the mixture volume. The mixture is transferred into a sealed container and kept closed for at least 24 hours. Immediately before use, 6 g of catalyst K-21 are added to the resulting filled polymer composite material and thoroughly mixed again.

When considering the relationship between the qualitative and quantitative composition of the claimed polymer composite material, the following conclusions can be made with sufficient certainty.

The combination of low-molecular-weight silicone rubber with a silicone oligomer and ethyl silicate provides a combination of heat resistance, thermal stability and frost resistance of vulcanizates of a polymer composite material with its initial technological properties. In this case, the silicone oligomer performs both a structure-forming function and an active diluent of the polymer matrix material. The performance of the vulcanizate is enhanced by the isotropy of the composite material. At the same time, the fluidity of the composite material is improved, which is necessary for its application on the surface of the product, as well as its elasticity after polymerization.

Although it is known that the introduction of ethyl silicate and its derivatives into composites leads to a partial decrease in the elasticity of the vulcanizates of composite materials, this factor is compensated by an increase in the strength characteristics during the course of the polymerization and vulcanization processes.

The total content of the liquid constituents of the material components makes it possible to provide the required technological properties for the introduction of finely dispersed fillers into its composition in the amounts indicated in the formulations of the claimed material. When the content of the filler is in amounts less than the specified, the required thermal conductivity of the materials is not provided, and when the content of the fillers is in amounts exceeding the specified limits, it is not possible to provide the technological properties of the material necessary for solving the main problem of the invention. This is due to the fact that a significant initial viscosity does not allow for defect-free sealing by applying products to complexly shaped surfaces.

As a low molecular weight silicone rubber in the composition of a polymer composite material, rubbers with a molecular weight in the range from 20,000 to 50,000 are used. The use of rubbers with a molecular weight of less than 20,000 does not provide the required strength of the composite material after its polymerization. The use of rubbers with a molecular weight of more than 50,000, due to their significant viscosity, leads, after the introduction of the necessary amounts of heat-conducting fillers into its volume, to a deterioration in the technological properties of the composite material.

Thus, the problem of the invention, which is to create a composite polymer material with expanded technological and operational capabilities for use in sealing complex small-sized products, including small parts on surfaces, can be considered solved.

Claims (2)

1. Composite polymer material for sealing radio electronic products, including low molecular weight siloxane rubber, silicone oligomer, ethyl silicate and fine silica, characterized in that it additionally contains fine aluminum hydroxide, fine wollastonite, optionally finely dispersed aluminosilicates, optional fine aluminosilicates, optionally cold curing based on organotin compounds and / or based on amines, and a mixture of silicon oxide selected from ground pulverized quartz and cristobalite, aluminum hydroxide of fractions 2-5 microns and 5-20 microns, wollastonite fractions 3-5 microns is used as a filler, optionally aluminosilicates represented by fine fractions of 2-5 microns, optionally finely dispersed aluminum oxide fractions of 2-5 microns, and the binder consists of siloxane rubber, ethyl silicate and a silicone oligomer, catalysts are used as a hardener in amounts of 2-5 wt.h. per 100 wt.h. binder. 2. Composite polymer material for sealing electronic products according to claim 1, characterized in that the binder is with the filler in a weight ratio, parts by weight: binder: total weight of the filler is 100: (100-130).