RU2493186C1 - Polymer composition for absorbing high-frequency energy - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: polymer composition contains low-molecular weight dimethylsiloxane rubber STKN as a base, a cold curing catalyst K-68, radio carbonyl iron P-10 as absorbing filler, additionally a solution of high-molecular weight rubber SKT in liquid polymethylsiloxane and tetraethoxysilane or derivatives thereof, as well as polyethylene polyamine as a curing rate controller. When producing the polymer composition, carbonyl iron is first bound with low-molecular weight rubber SKTN in a mixture with derivatives of tetraethoxysilane and liquid polymethylsiloxane (component A). The mixture (component A) is held for at least 24 hours. The rubber SKT is bound with another portion of the liquid polymethylsiloxane and tetraethoxysilane derivatives (component B) and also held for 24 hours. Component A and component B are mixed with each other immediately before adding the catalyst. The amount of catalyst K-68 or mixture thereof with polyethylene polyamine determines the overall rate of cure and controlled time of loss of fluidity of the composition.

EFFECT: obtaining a polymer composition with absorbent properties with small layer thickness, having sufficient strength and elasticity of the vulcanisate in a wide temperature range, shorter curing time and enabling control of the rate of cure.

2 cl, 4 tbl, 5 ex

Description

The invention relates to the field of radio engineering materials, in particular to polymer compositions intended for absorption of radiation. The results of the invention can be particularly applied in the absorption of spurious emissions in closed sealed volumes of microwave devices. Various polymer compositions are known for volumetric absorbers of high-frequency energy (OST 107.460007.006-92). These materials as the main binder contain epoxy resins, hardeners and accelerators, and carbonyl radio engineering iron as the absorbing dispersion. However, this group of materials is not absorbent in the required range of operating temperatures and does not withstand prolonged exposure to high humidity. The ability of materials to absorb does not provide sufficient attenuation of the microwave signal wave. The same disadvantages are inherent in compositions based on polyurethane and carbonyl radio engineering iron (OST 107.460007.006-92). Although the composition based on polyurethane with carbonyl radio engineering iron is superior to epoxy compositions in a number of physical and mechanical parameters, it is not resistant to salt fog. Known compositional compositions based on silicone elastomers, cured by platinum systems, and filled with carbonyl radio engineering iron powder, a mixture of ferrite materials or metal-coated glass balls (US patent No. 4173018, US patent No. 5764181).

The disadvantages of these materials are both large weight and fragility, and considerable cost.

Known domestic composite material for the absorption of high-frequency energy (RF patent 2294347). The composition includes synthetic rubber, low molecular weight dimethylsiloxane SKTN, a cold curing catalyst and an alsifer absorbing filler in an amount of up to 85 parts by weight 15-25 parts by weight rubber. The disadvantage of the material is the complex technology for the manufacture of alsifer powder and its preparation for introduction into the composition. In addition, this material has insufficient absorption properties with a small thickness of the absorbing layer. These disadvantages are partially eliminated in the technical solution of the invention (RF patent No. 2349615). The polymer composition, consisting of low molecular weight SKTN, a cold curing catalyst and an absorbent filler, as the latter contains radio engineering carbonyl iron in the following ratio of components, parts by weight:

Synthetic low molecular weight rubber dimethylsiloxane SKTN 15-25 Cold cure catalyst 0.6-1.0 Iron carbonyl radio engineering brand R-10 78-83

Patent for the invention of the Russian Federation No. 2349615 dated November 6, 2007 was adopted as a prototype. The disadvantages of this composition, adopted as a prototype, include low mechanical strength, long curing time and a significant mass of radio carbonyl iron. Carbonyl iron does not belong to active fillers, and even a marginal increase in its content in the composition, the excess of which leads to a critical loss of technological properties with loss of fluidity, does not provide the necessary strength of the absorbing coating under thermal and mechanical loads. The manufacture of a polymer composition by simple mixing of the components and curing them at room temperature is inevitably associated with a significant delamination in thickness and a noticeable subsidence of carbonyl iron during the curing of the rubber SKTN. Another negative consequence is the curing time associated with a small amount of K-68 catalyst relative to the amount of SCTH rubber. In this case, the technological effectiveness of coating deposition and its quality suffers when the outer coating layer is not only depleted in absorbent filler, but also inferior to the inner layers in physical and mechanical properties. Such unevenness of the composition during the curing process and upon its completion inevitably affects both strength and absorbing properties. As viscosity increases with curing of the composition to air inclusions exiting the interface, the rubber filler becomes difficult to leave the volume of the composition. In the process of loss of fluidity with subsequent vulcanization, they are inevitably fixed in the volume of the vulcanizate - this leads not only to a decrease in the homogeneity of the composition and uniformity of the physical and mechanical properties in the volume of the vulcanizate, but also to a deterioration in the quality of absorption with the loss of possible absorption parameters.

The technical task of the invention is to obtain a polymer composition with absorbing properties at a small layer thickness, which would have sufficient strength and elasticity of the vulcanizate in a wide temperature range, as well as a reduced curing time and an adjustable curing rate. The solution of this problem is achieved by the fact that the polymer composition containing SKTN dimethylsiloxane rubber, K-68 cold curing catalyst, and carbonyl iron as an absorbing filler, additionally contains a solution of SKT high molecular weight rubber in polyalkylsiloxane and tetraethoxysilane (TPP) or its derivatives, as well as polyethylene polyamine as a regulator of the curing rate in the following ratio of components, parts by weight:

Rubber low molecular weight dimethylsiloxane SKTN 13-20 SKT rubber 2-3 Tetraethoxysilane or its derivatives selected from ethyl silicate-40 and ethyl silicate-32 2-3 Iron carbonyl radio engineering R-10 78-90 Catalyst for cold curing K-68 1.0-1.5 Polyethylene polyamine up to 1.0 Polymethylsiloxane fluid selected from PMS-50 and PMS-100 2-3

When analyzing the composition of the claimed composition should indicate that when the content of SCTN less than 13 wt.h. the required initial fluidity is not provided. When the content of SKTN in excess of 20 parts by weight, the corresponding content of radio engineering iron does not provide effective absorption of radio frequency energy. The necessary and sufficient combination of strength properties and the initial working viscosity is achieved when the content of SKT from 2 to 3 parts by weight The amount of tetraethoxysilane or its derivatives in the range of 2-3 mass.h. is sufficient for dilution of SKT without negatively affecting the vulcanizate elasticity of the composition. On the other hand, a real increase in strength properties is achieved. The presence in the composition of 2-3 wt.h. PMS is necessary and sufficient to improve the elasticity of the vulcanizate and at the same time accelerated homogenization of rubber SKT. The total content of the components within the specified limits practically does not make any difference in the ratio of the polymer base - absorbing filler in comparison with that for the prototype. The required level of absorption by high-frequency energy is retained. Selected for the composition of the content of the catalyst K-68 or its mixture with PEPA can provide a fairly quick and uniform cure of the claimed composition. In this case, a noticeable precipitation of the filler during the curing process does not occur. The reaction of PEPA with tetraethoxysilane or ethyl silicate becomes an additional factor controlling the cure rate.

Another technical task is to develop a method for producing a composition that eliminates the release of a significant amount of air bubbles from the surface of carbonyl iron particles. The technical problem associated with the method is solved in that the carbonyl iron is pre-combined with low molecular weight rubber SKTN in a mixture with derivatives of tetraethoxysilane and polymethylsiloxane. The mixture (hereinafter - component A) is incubated for 24 hours. In this case, almost all air inclusions leave the volume of the composition and by the time of curing the possibility of separation of air inclusions is minimized.

Another feature of the method is the preliminary dissolution of rubber SKT in polyalkylsiloxane and tetraethoxysilane derivatives. The mixture (hereinafter referred to as component B) is kept in a separate container until the component components are completely distributed in each other. Component A and component B are mixed with each other just before the introduction of the catalyst. Polyethylene polyamine is pre-mixed with K-68 catalyst, and its amount determines the total curing rate due to the reaction of interaction with tetraethoxysilane or ethyl silicate.

The composition of the inventive polymer composite material includes the following components:

Dimethylsiloxane rubber SKTN TU 2294-002-00152000-96, GOST 13835-73 Tetraethoxysilane TU 2435-419-05763441-2003 Ethyl silicate-32 GOST 26371-84 Ethyl silicate-40 GOST 263 71-84 Catalyst for cold curing K-68 TU 38.303-04-05-90 Polyethylene polyamine TU 2413-357-00203447-99 Polymethylsiloxane liquid GOST 13032-77 Iron carbonyl radio engineering brands R-10 GOST 136110-79

Table 1 shows the overall composition of the polymer composition according to the invention.

Table 2 shows the composition of component A of the polymer composition. Table 3 shows the composition of component B of the polymer composition. Table 4 shows the properties of the polymer composition in comparison with the properties of the material of the prototype.

The method of obtaining the inventive polymer composite material is illustrated by the following examples:

Example 1

Get component A. For this, in a separate container mix 13 g of rubber SKTN and 1 g of ethyl silicate-40 for at least 5 minutes. 78 g of carbonyl iron powder are added to the mixture and the components are mixed until the composition is uniformly visually determined. The mixture is stored in a mixing tank for at least 24 hours.

Get component B. For this, 2 g of SKT rubber are added to the container, 1.5 g of ethyl silicate-40, and 2 g of PMS-50 are added. Mix the components until a homogeneous composition is achieved and leave in the container for at least 24 hours. After exposure in a separate container, the obtained components are mixed: component a and component B in the mixing tank of one of the components. Stirring is carried out for 10 minutes. Then, 1 g of K-68 catalyst is added with stirring. After 2 minutes, the composition is applied to the surface with a layer of the required thickness.

Example 2

Get component A. For this, in a separate container mix 20 g of rubber SKTN and 1 g of ethyl silicate-32 for at least 5 minutes. 90 g of carbonyl iron powder are added to the mixture and the components are mixed until the composition is uniformly visually determined. The mixture is stored in a mixing tank for at least 24 hours.

Get component B. For this, 2.5 g of SKT rubber are added to the container, 2 g of ethyl silicate-32, and 2 g of PMS-100 are added. Mix the components until a homogeneous composition is achieved and leave in the container for at least 24 hours. After exposure in a separate container, the obtained components are mixed: component a and component B in the mixing tank of one of the components. Stirring is carried out for 10 minutes. Then, with stirring, add 1.5 g of the catalyst K-68 and PEPA 1 g. After 2 minutes, the composition is applied to the surface with a layer of the required thickness.

Example 3

Get component A. For this, in a separate container mix 18 g of rubber SKTN, 1 g of ethyl silicate-32 and 0.5 g of PMS-50 for at least 5 minutes. 87 g of carbonyl iron powder are added to the mixture and the components are mixed until the composition is uniformly visually determined. The mixture is stored in a mixing tank for at least 24 hours.

Get component B. For this, 2 g of rubber SKT, add 1.5 g of ethyl silicate-32, and 1.5 g of PMS-100. Mix the components until a homogeneous composition is achieved and leave in the container for at least 24 hours. After exposure in a separate container, the obtained components are mixed: component a and component B in the mixing tank of one of the components. Stirring is carried out for 10 minutes.

Then, 1.4 g of K-68 catalyst and PEPA 0.7 g are added with stirring. After 2 minutes, the composition is applied to the surface with a layer of the required thickness.

Example 4

Get component A. For this, in a separate container mix 16 g of rubber SKTN and 1 g of PMS-50 for at least 5 minutes. 80 g of carbonyl iron powder are added to the mixture and the components are mixed until the composition is visually uniform. The mixture is stored in a mixing tank for at least 24 hours.

Get component B. For this, 2.5 g of SKT rubber are added to the container, 2 g of ethyl silicate-40, and 2 g of PMS-50 are added. Mix the components until a homogeneous composition is achieved and leave in the container for at least 24 hours. After exposure in a separate container, the obtained components are mixed: component A and component B in the mixing tank of one of the components. Stirring is carried out for 10 minutes. Then, 1.5 g of K-68 catalyst and PEPA 1 g are added with stirring. After 2 minutes, the composition is applied to the surface with a layer of the required thickness.

Example 5

Get component A. For this, in a separate container mix 17 g of rubber SKTN and 1 g of ethyl silicate-40 for at least 5 minutes. 85 g of carbonyl iron powder are added to the mixture and the components are mixed until the composition is uniformly visually determined. The mixture is stored in a mixing tank for at least 24 hours.

Get component B. To do this, add 3 g of rubber SKT, add 2 g of ethyl silicate-40, and 2.5 g of PMS-50. Mix the components until a homogeneous composition is achieved and leave in the container for at least 24 hours. After exposure in a separate container, the obtained components are mixed: component A and component B in the mixing tank of one of the components. Stirring is carried out for 10 minutes. Then, 1.2 g of K-68 catalyst is added with stirring. After 2 minutes, the composition is applied to the surface with a layer of the required thickness.

From the description of the present application for the invention in terms of composition and method, the materials given in the tables of composition and its properties, as well as examples of the production method, it follows that the technical problems formulated in this application have been solved.

A polymer composition based on silicone rubbers has been developed to absorb high-frequency energy with a small thickness of the deposited layer with the necessary strength and elasticity of the vulcanizate in a wide temperature range. The resulting composition surpasses the composition of known analogues, as well as the composition of the prototype in terms of strength and elasticity of the vulcanizate, resistance to prolonged exposure to moisture and salt fog. In addition, it is possible to achieve acceleration of the curing of the composition at the optimum time of viscosity set. This prevents noticeable subsidence of the filler and the heterogeneity of the vulcanizate in composition.

Preparation of composite material in the form of pre-prepared components: component A and component B, connected immediately before applying the catalyst. In particular, viscous reinforcing rubber SKT is introduced into the mixture in the form of a solution in liquid silicon-containing components. Exposure of component a and component B for at least 24 hours allows almost all air inclusions to leave the volume of component A, and for component B to achieve homogenization of the composition.

Declare the composition of the composition obtained using the developed and proposed method in the pilot production of ZAO Integrated Technical Service. Made the adjustment of several variants of the compositions within the claimed limits, in relation to specific application problems. The composition and method have been tested and applied with a positive result in current practical developments.

The applicant asks to consider the materials presented for the grant of a patent of the Russian Federation for an invention.

Claims (2)

1. A polymer composition for absorbing high-frequency energy containing low molecular weight dimethylsiloxane SKTN rubber as a base, radioactive carbon iron and a cold curing catalyst K-68 as an absorbing filler, characterized in that it further comprises a solution of high molecular weight SKT rubber in polymethylsiloxane and tetraethoxysilane or its derivatives, as well as polyethylene polyamine as a regulator of the curing rate in the following ratio of components, parts by weight:
Rubber low molecular weight dimethylsiloxane SKTN 13-20 SKT rubber 2-3 Tetraethoxysilane or its derivatives selected from ethyl silicate-40 and ethyl silicate-32 2-3 Iron carbonyl radio engineering R-10 78-90 Catalyst for cold curing K-68 1.0-1.5 Polyethylene polyamine Up to 1.0 Polymethylsiloxane fluid selected from PMS-50 and PMS-100 2-3 2. The method for producing the composition according to claim 1, which consists in the fact that the carbonyl iron radio engineering is pre-combined with rubber with low molecular weight dimethylsiloxane SKTN, part of a polymethylsiloxane liquid, part of tetraethoxysilane or its derivatives in component A, is maintained after mixing for at least 24 hours, and SKT rubber combined with part of the liquid polymethylsiloxane, part of tetraethoxysilane or its derivatives in component B, maintained after mixing to a homogeneous state for at least 24 hours, and then mixed with the component And, add K-68 catalyst or its mixture with polyethylene polyamine followed by curing.