RU2720195C2 - Heat-conducting compound - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to polymer composite materials intended for high-voltage sealing of articles and systems of technical purpose, operating in modes requiring efficient removal of excess heat energy during operation. Heat-conducting compound consists of two components: polymer-containing base (component A) and hardening mixture (component B), in weight ratio: per 100 pts. wt component A is from 3 pts. wt up to 12 pts. wt component B. Component A is a mixture of low-molecular weight silicone rubber with molecular weight 15,000–55,000 standard units with silicone oligomer, with fine aluminum hydroxide, optionally, silicon oxide, and component B is a mixture of ethyl silicate and organotin salt, selected from tin octoate and tin diethyldacapralate, and optionally a silicone oligomer, and optionally polyethylene polyamine.

EFFECT: invention increases compatibility of processing properties – relatively low viscosity, filling properties, high viability, with heat conductivity, dielectric and physical and mechanical properties.

1 cl, 6 tbl

Description

Thermally conductive compound

The invention relates to the field of polymer composite materials intended for high-voltage sealing of products and systems for technical purposes, operating in modes requiring the efficient removal of excess thermal energy during operation.

Various composite polymeric materials are known for high-voltage sealing and for the removal of heat generated during the operation of technical devices, sealants, compounds and adhesives, compositions of these materials and methods for their intended use. They are widely used in electronic equipment (IET), electrical and radio electronic equipment (CEA) in communications, in special technical products for various purposes.

Known heat-conducting and electrically conductive material (RF patent No. 2200170), containing particles of a carbon material with a polypropylene coating, but not possessing the properties of a dielectric. Its use in sealing and gluing is associated with significant technological problems.

Known electrical insulation composition with heat-conducting properties based on epoxy resins, hardener and fillers: aluminum oxide and boron nitride (ed. St. USSR No. 643978). The main obstacle to the use of this composition is a very large initial viscosity, which determines its low actual suitability for most tasks.

Heat-conducting pastes, greases, foils with a coating filling the surface irregularities (paraffins, waxes), fiberglass-based materials filled with silicone rubber manufactured by Berquist, as well as other innovative heat-dispersing polymer composites are known. (“Power Electronics” No. 2, 2008, pp. 118-123, “Power Electronics” No. 3, 2012, pp. 48-52). Their common disadvantages include: foreign origin of components, limited technological capabilities for use, non-compliance with a number of operational requirements for domestic sealing facilities, as well as high prices.

A number of domestic silicone sealants and compounds with a low level of thermal conductivity are known. Among them, mention should be made of compounds Silagerm-2112 of brands A, B, C, Silagerm-2142, Silagerm-2108, Silagerm-2111, Silagerm-21 14, and a number of its traditional analogues, for example, sealant Vixint U-4-21. However, these materials have thermal conductivity values in the range of 0.5-0.7 W / (m⋅K) and are intended, first of all, for high-voltage sealing.

Various foreign heat-conducting composite materials with dielectric properties are known. These include, in particular, Dow Corning 9184 sealant with a thermal conductivity of 0.84 W / (m⋅K), Sylgard 160 sealant with a thermal conductivity of 0.62 W / (m⋅K), compound Q3-3600 with a thermal conductivity of 0 , 77 W / (m⋅K), compound SE4445 and a number of others. Heat-conducting pastes are also known, for example, Dow Corning 340, with a thermal conductivity of 0.68 W / (m⋅K), Dow Corning SC 102 with a thermal conductivity of 0.85 W / (m⋅K) and others. The disadvantages of these materials are not always a high level of thermal conductivity and, which is especially significant, foreign origin. A number of sealants and compounds of foreign origin based on silicone, polyurethane, epoxy and other polymer binders are also known, some of which have found practical application in domestic technology. These include, in particular, epoxy materials ER2188, ER2138, polyurethane compounds UR5604 and UR5633 (manufactured in Great Britain) and silicone compounds SC2003 and SC2001. However, most of these materials have thermal conductivity values significantly lower than 1.0 W / (m⋅K) with fairly ordinary performance and technological properties. This fact further confirms the relevance of the tasks associated with the search and development of heat-conducting sealants and compounds for their production in Russia in order to meet the needs of domestic equipment and technology in various fields of application, including areas of special equipment.

Known compounds of the KPTD-1/1 group, manufactured by NOMACON according to TU RB 100009933.004-2001. These include compounds 1 L-1.00; 1 L-1.50; 1L-2.50 with good dielectric properties, but with a thermal conductivity of not higher than 0.50 W / (m⋅K). For many cases of targeted use, this level is not sufficient. In addition, the absence of a whole series of information on the physicomechanical characteristics may lead to the assumption of their insufficiently high values. Compounds KPTD-1/1, classified as "heavy", have a slightly better thermal conductivity, namely, compounds 1T-5.50; 1T-8.50; 1T-12.5. In this case, it is possible to achieve a thermal conductivity level of not more than 1.00 W / (m⋅K) due to a significant increase in viscosity. At the same time, the parameters determining the manufacturability of the compounds are significantly deteriorating. Due to the lack of fully cited data, it is difficult to judge the strength and elasticity of the vulcanizates of the considered compounds. These compounds, like most materials manufactured by NOMACON according to the documentation of the Republic of Belarus, are characterized by significant retail prices.

Known domestic compound KTK-1 (TU 2252-037-89021704-2013) for the manufacture of products of radio and electrical equipment, which is obtained by mixing two components at room temperature. When the thermal conductivity coefficient is 1.1 W / (m⋅K), the compound in the cured state exhibits a tensile strength of not more than 0.6 MPa and an elongation at break of not more than 30%. Thus, with a sufficient level of thermal conductivity, it is significantly inferior in strength and elasticity to most known silicone compounds. The same applies to other compounds of the CPC group manufactured by the STEP enterprise (St. Petersburg, Russia). Its counterpart KTK-2 (TU 2252-019-50050552-2016) has slightly better parameters than KTK-1 - its strength reaches 1.2 MPa at almost the same thermal conductivity as KTK-1. At the same time, one cannot but note the rather high retail prices for these compounds, which also confirms the feasibility of further development of new compounds and sealants with increased thermal conductivity.

Known electrical insulation composition (ed. St. USSR No. 1078470) based on epoxy Dianov resin containing silicon or silicon carbide as a filler. The main disadvantage of the composition is the need to use elevated application temperatures. Other disadvantages are technical problems associated with the removal of the hardened composition from the flooded electrical components (for example, chokes) due to technological errors and the need for repeated application operations.

The specified electrical insulation composition with thermal conductivity properties based on domestic constituent components is closest in a number of leading parameters to the claimed heat-conducting compound and is selected as a prototype of the present invention.

The objective of the present invention is to provide a heat-conducting compound designed to remove excess heat from printing units of working products and electronic systems, electronic equipment and communications equipment, as well as for their high-voltage sealing, in which the necessary level of determining technological characteristics (relatively low viscosity) must be combined , casting properties, high viability), thermal conductivity, dielectric and physico-mechanical properties.

The technical result consists in the fact that the heat-conducting compound based on silicone elastomers and silicone oligomers is a multicomponent heterogeneous system filled with finely divided particle agglomerates having different structures, heat-conducting properties, dielectric and mechanical properties with certain quantitative ratios between the components, as well as their technological features connections.

1. The technical result is achieved in that the heat-conducting compound is an electrical insulating composition, characterized in that it contains silicone rubber as a polymer binder and finely divided fillers, and consists of two components: component A (polymer-containing base of the heat-conducting compound) and component B (curing system), characterized in that the components are connected in mass ratios: per 100 parts by weight component A from 3 parts by weight up to 12 parts by weight component B, and component A is a mixture of low molecular weight silicone rubber with a molecular weight of 15,000-55,000 cu with a silicone oligomer, with aluminum hydroxide, aluminum nitride, not necessarily silicon oxide in the following ratio of constituent ingredients, parts by weight:

low molecular weight silicone rubber selected

from SKTN grade A, SKTN grade B and SKTNF grade A 100 silicone oligomer selected from PMS-20, PMS-50 and PMS-100 20-50 aluminum hydroxide particle size 1-20 microns 200-300 silica particle size 0.2-2 microns 0-80 aluminum nitride 30-60

and component B is a mixture of ethyl silicate and an organotin salt selected from tin octoate and tin diethyl dicaprylate, not necessarily a silicone oligomer, not necessarily polyethylene polyamine in the following ratio of ingredients, wt.h:

ethyl silicate selected from ES-32 and ES-40 100 the catalyst is an organotin salt, selected from tin octoate or tin diethyl dicaprylate 10-30 silicone oligomer selected from PMS-50 0-40 polyethylene polyamine 0-5

The composition of the inventive heat-conducting compound includes components from table 1.

Table 2 shows the composition of component A of the heat-conducting compound.

Table 3 shows the composition of component B of the heat-conducting compound.

Table 4 shows the composition of the heat-conducting compound.

Table 5 shows the data on the main characteristics of the heat-conducting compound.

Table 6 shows the comparative characteristics of the heat-conducting compound, its prototype and analogues.

The following are specific examples of the preparation of component A and component B of the heat-conducting compound, as well as examples of the preparation of the inventive heat-conducting compound. The compositions of component A No. 1-4 (Table 2), component B No. 5-8 (Table 3) and the heat-conducting compound No. 9-12 (Table 4) correspond to examples of their preparation with identical numbers.

Example 1

Preparation of component A of a heat-conducting compound. Weigh 100 g of SKTN rubber of grade A in a container for mixing components. Place 20 g of PMS-20 silicone oligomer in a container and mix it thoroughly with rubber for 2-3 minutes. 40 g of aluminum nitride is added to the resulting mixture with stirring and maintained until the main amount of air inclusions leaves the volume of the mixture. Then, aluminum hydroxide in an amount of 200 g, and also powdered silica grade B grade in an amount of 40 g are added to the resulting suspension in parts, periodically mixing, Component A is transferred to a closed container and stored in a closed form until it is brought into contact with component B, but not less than 24 hours

Example 2

Preparation of component A of a heat-conducting compound. Weigh 100 g of SKTN rubber of grade A in a container for mixing components. Place 50 g of PMS-100 silicone oligomer in a container and mix thoroughly with rubber for 2-3 minutes. 60 g of aluminum nitride are added to the resulting mixture with stirring and maintained until the main amount of air inclusions leaves the mixture volume. Then, 280 g of aluminum hydroxide is added to the resulting suspension in portions, periodically mixing, Component A is transferred to a resealable container and stored in a closed form until it is brought into contact with component B, but for at least 24 hours.

Example 3

Preparation of component A of a heat-conducting compound. Weigh 100 g of SKTNF grade A rubber in a container for mixing the components. Place 50 g of PMS-50 silicone oligomer in a container and mix it thoroughly with rubber for 2-3 minutes. 50 g of aluminum nitride is added to the resulting mixture with stirring and maintained until the main amount of air inclusions leaves the volume of the mixture. Then, aluminum hydroxide in an amount of 300 g, as well as powdered silica grade B grade in an amount of 80 g, is introduced into the resulting suspension in parts, periodically mixing, Component A is transferred to a closed container and stored closed until it is brought into contact with component B, but not less than 24 hours

Example 4

Preparation of component A of a heat-conducting compound. Weigh 100 g of SKTN rubber of grade B in a container for mixing components. 25 g of PMS-20 silicone oligomer is placed in a container and mix thoroughly with rubber for 2-3 minutes. 30 g of aluminum nitride is added to the resulting mixture with stirring and kept until the main amount of air inclusions leaves the mixture volume. Then, aluminum hydroxide in an amount of 290 g, as well as ground quartz powdered grade B in an amount of 30 g, is introduced into the resulting suspension in parts, periodically mixing, Component A is transferred to a closed container and stored in a closed form until it is brought into contact with component B, but not less than 24 hours

Example 5

Preparation of component B of a heat-conducting compound. 100 g of ethyl silicate-40 are weighed in a container for mixing the components. Add 10 g of tin octoate and mix thoroughly. The resulting component B is transferred to a resealable container and stored until it comes into contact with component A.

Example 6

Preparation of component B of a heat-conducting compound. 100 g of ethyl silicate-40 are weighed in a container for mixing the components. Add 18 g of tin diethyl dicaprylate and mix thoroughly. Add 50 g of PMS-50 silicone oligomer and mix again. The resulting component B is transferred to a resealable container and stored until it comes into contact with component A.

Example 7

Preparation of component B of a heat-conducting compound. 100 g of ethyl silicate-32 are weighed in a container for mixing the components. Add 12 g of tin octoate and mix thoroughly. Add 50 g of the silicone oligomer PMS-50, 2 g of polyethylene polyamine and mix again. The resulting component B is transferred to a resealable container and stored until it comes into contact with component A.

Example 8

Preparation of component B of a heat-conducting compound. 100 g of ethyl silicate-40 are weighed in a container for mixing the components. Add 30 g of tin diethyldicaprylate and mix thoroughly. Add 30 g of PMS-50 silicone oligomer and mix again. The resulting component B is transferred to a resealable container and stored until it comes into contact with component A.

Example 9

Preparation of a heat-conducting compound. To prepare the compound, 100 g of component A, composition 1 (table 2) is added to the technological tank. Add 10 g of component B, composition 1 (table. 3). The components are thoroughly mixed for 2-3 minutes, and the finished compound is transferred for technological use.

Example 10

Preparation of a heat-conducting compound. To prepare the compound, 100 g of component A, composition 4 (table 2) is added to the technological tank. Add 3 g of component B, composition 3 (table. 3). The components are thoroughly mixed for 2-3 minutes, and the finished compound is transferred for technological use.

Example 11

Preparation of a heat-conducting compound. To prepare the compound, 100 g of component A, composition 2, are added to the technological tank (Table 2). Add 4 g of component B, composition 2 (table. 3). The components are thoroughly mixed for 2-3 minutes, and the finished compound is transferred for technological use.

Example 12

Preparation of a heat-conducting compound. To prepare the compound, 100 g of component A, composition 7, is added to the technological capacity (Table 2). Add 9 g of component B, composition 4 (table. 3). The components are thoroughly mixed for 2-3 minutes, and the finished compound is transferred for technological use.

When developing a heat-conducting compound, it is necessary to fulfill several agreed requirements, namely:

- the heat-conducting properties of the compound should not be lower than that of analog materials and the material adopted as a prototype;

- the technological application of the compound must be ensured, that is, a combination of the optimal level of viscous-flowing properties, viability and time of complete rejection;

- the necessary level of physicomechanical and dielectric properties of the claimed heat-conducting compound must be maintained.

From the presented description, the data in the tables and examples it follows that, taking into account the specified requirements, a choice was made of compatible components and quantitative ratios of ingredients in each of the two parts of the compound for sealing (component A and component B). Optimum compliance with the basic requirements is achieved by the fact that the heat-conducting compound based on silicone rubber, fillers, plasticizers and the curing system consists of two parts. The basis - component A, consists of a mixture of low molecular weight silicone rubber, silicone oligomer, fillers: finely divided aluminum hydroxide, silicon oxide and aluminum nitride. Component B, introduced into contact with component A, is a curing system comprising ethyl silicate, an organotin salt and optionally a silicone oligomer and polyethylene polyamine.

The development of a dielectric heat-conducting compound with an increased level of heat conductivity is based on the factors of physical and chemical compatibility of the ingredients used, with their quantitative limits, as part of the basis of the heat-conducting compound (component A). The determining role is also played by the quantitative relations of component A with component B. As a result, it is possible to obtain vulcanizates of a heat-conducting compound with the necessary and sufficient level of basic characteristics.

The use of the low molecular weight rubbers SKTN and SKTNF as the initial polymer base makes it possible to provide a combination of thermal stability and frost resistance of vulcanizates of a heat-conducting compound while maintaining its elasticity over a wide temperature range. When using rubbers of molecular weight with a value of less than 15,000, it is not possible to achieve the required strength of the vulcanizates of the heat-conducting compound. When rubbers are used with a molecular weight of more than 55,000 due to a significant increase in the viscosity of the system, it is not possible to introduce the required quantities of heat-conducting and structuring fillers. The use of low molecular weight silicone rubber selected from SKTN grade A, SKTN grade B, SKTNF grade A, allows for the thermal stability of the heat-conducting compound and its resistance to low temperatures in a wide range of operating conditions for electronic equipment and electronic equipment, as well as the optimal degree of fullness the polymer matrix of component A with heat-conducting fillers. The mass ratio of the ingredients of component A allows you to maintain its viscous flow properties in a wide range of technological conditions.

The choice of aluminum hydroxide, aluminum nitride and silicon oxide as fillers is determined by their significant thermal conductivity in combination with a sufficient degree of physicomechanical properties of vulcanizates of the heat-conducting compound. This is achieved through a combination of reinforcing and structural properties of the fillers used. Silicone oligomers act as active diluents, which reduces the initial viscosity of the compound to the extent necessary, as well as the functions of plasticizers that affect the elasticity of vulcanizates. The use of silicone oligomers in amounts less than those indicated is not effective. The use in amounts greater than those indicated may adversely affect the heat resistance of the compound and lead to their partial release from the vulcanizate volume of the heat-conducting compound during prolonged heating. The use of aluminum hydroxide, aluminum nitride and silicon oxide (in particular silica powder dust grade B) in amounts less than those described in the description for component A is not effective from the standpoint of maintaining the required level of thermal conductivity and physico-mechanical properties. The use in quantities greater than those indicated can lead to an undesirable increase in the viscosity of the heat-conducting compound and to the preservation of air inclusions in its volume after curing. In turn, this could lead to the loss of the required manufacturability of the compound. The combination of the component parts of component A and component B in the presented range of ratios makes it possible to achieve the required curing efficiency of the heat-conducting compound and its insignificant initial viscosity at the required pot life. When the quantitative ratio of component A and component B is more than 100: 3, the required fluidity of the heat-conducting compound and its optimal level of technological properties cannot be achieved. With a quantitative ratio of component A and component B less than 100: 12, although sufficient fluidity is achieved, it is not possible to provide either the necessary viability or the necessary elasticity of the vulcanizates of the heat-conducting compound.

The above arguments, subject to the data of tables and examples, suggest that the properties of the components of the claimed heat-conducting compound and the limits of their content in the composition of the compound, as well as their quantitative ratios in the prepared components are optimal. This makes it possible to combine the required level of thermal conductivity with other technological and operational characteristics. Analysis of the data on the inventive heat-conducting compound and the achieved quantitative characteristics allows us to consider the technical problem of the invention solved.

The applicant asks to consider the submitted application "Heat-conducting compound" for the issue of a patent of the Russian Federation for an invention.

Claims (4)

A heat-conducting compound, characterized in that it contains silicone rubber as a polymer binder and finely dispersed fillers, and consists of two components: component A is the polymer-containing base of the heat-conducting compound and component B is a curing system, while the components are combined in mass ratios: 100 wt. h component A from 3 parts by weight up to 12 parts by weight component B, and component A is a mixture of low molecular weight silicone rubber with a molecular weight of 15,000-55,000 cu with a silicone oligomer, with aluminum hydroxide, aluminum nitride and optionally silicon oxide in the following ratio of constituent ingredients, parts by weight: low molecular weight silicone rubber selected from SKTN grade A, SKTN grade B and SKTNF grade A 100 silicone oligomer selected from PMS-20, PMS-50 and PMS-100 20-50 aluminum hydroxide particle size 1-20 microns 200-300 silica particle size 0.2-2 microns 0-80 aluminum nitride 30-60, and component B is a mixture of ethyl silicate and an organotin salt selected from tin octoate and tin diethyl dicaprylate, not necessarily a silicone oligomer, not necessarily polyethylene polyamine in the following ratio of constituent ingredients, parts by weight: ethyl silicate selected from ES-32 and ES-40 100 the catalyst is an organotin salt, selected from tin octoate or tin diethyl dicaprylate 10-30 silicone oligomer selected from PMS-50 0-40 polyethylene polyamine 0-5