RU2603790C2 - Composition for production of semi-finished product of press material and method of making semi-finished product - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to polymer compositions based on phenol-formaldehyde resin, butadiene-nitrile rubber in butyl acetate, powdered and fibrous fillers for production of semi-finished product of press material for general industrial purposes. Composition contains following components, pts.wt: resol type phenol-formaldehyde resin (Resol 300) in form of a solution with concentration (65±5)% per dry residue in alcohol - 35.0÷65.0; butadiene-nitrile rubber in form of a solution with concentration of 11 %÷16 % per dry residue in butyl acetate or acetone - 5.0÷10.5; magnesium oxide - 2.0÷3.0; zinc oxide - 1.0÷2.0; boric acid - 0.3÷0.4; sulphur - 1.0÷2.0; captax in form of a suspension in butyl acetate in ratio of 1 pts.wt of captax to 5 pts.wt butyl acetate - 1.0÷2.0; calcium stearate or zinc stearate in form of a slurry (suspension) in ratio 1 part stearate to 5 parts alcohol in an amount of 1 % of weight of dry residue of impregnating compound - 0.4÷0.5; fibrous filler - 50.0÷70.0. Method of making semi-finished product based thereon includes making an impregnating compound, preparation of fillers, their impregnation, drying semi-finished product and moulding samples therefrom.

EFFECT: technical result is stabilisation of physical and processing properties of moulding material, higher quality of impregnation, uniform distribution of all ingredients in volume of press material, improved fluidity of material during pressing of complex shape articles.

11 cl, 2 tbl, 6 ex

Description

The invention relates to polymer compositions based on phenolic-formaldehyde resin, nitrile butadiene-carboxyl-containing rubber, and powdered and fibrous fillers for the manufacture of semi-finished pressing materials for general industrial use and to a method for their manufacture.

A known polymer composition (see SU, Copyright certificate No. 896030, C08L 61/10, 1982) containing as a binder a mixture of novolac phenol-formaldehyde resin, phenol-formaldehyde resole or aniline-formaldehyde resin, nitrile rubber, stearin and glass fiber as a filler, in the following ratio of components in mass parts:

Phenol-formaldehyde resin novolac type 5.0 ÷ 12.0 Resol-type phenol-formaldehyde resin or aniline formaldehyde resin 25 ÷ 40 Nitrile rubber 5 ÷ 12.5 Stearin 1 ÷ 2 Fiberglass rest

The disadvantage of this composition is the complexity of the technological process of processing into the product due to the lack of solvents.

Also known is a composition for the manufacture of flame retardant coatings (see RU, Patent No. 2037504, C08L 61 / 10,1995), including an inorganic filler and a polymer matrix based on phenol-formaldehyde resin, in the following ratio of components in mass parts:

Phenol-formaldehyde resin novolac type 79 ÷ 120 Utropin technical 7 ÷ 15 Azoisobutyronitrile 15 ÷ 30 Ground marshalite 280 ÷ 385 Asbestos chrysotile short-fiber 25 ÷ 45 Acrylonitrile Rubber 30 ÷ 70 Calcium stearate 1 ÷ 2 Sodium Alkyl Sulfonate 0.01 ÷ 1.0.

The disadvantages of the known composition are low strength, low processability.

The closest analogue of the known technical solutions to the claimed composition for the manufacture of a semi-finished product, taken as a prototype, is a composition for the manufacture of a semi-finished composition (see RU, Patent No. 2219203, C08L 61/10 2003) containing phenol-formaldehyde resin of the resol type, divinyl nitrile carboxyl-containing rubber, mercapto -benzothiazole, chrysotile asbestos, cotton fibers, burnt magnesia, zinc oxide, sulfur, boric acid, in the following ratio of components in mass parts:

Resol-type phenol-formaldehyde resin 14 ÷ 47 Divinyl nitrile carboxyl rubber 2.5 ÷ 20 Mercaptobenzthiazole 0.05 ÷ 0.62 Asbestos chrysotile 35 ÷ 65 Cotton fiber 7 ÷ 20 Burnt magnesia 0.08 ÷ 0.5 Zinc oxide 0.05 ÷ 0.62 Boric acid 0,02 ÷ 0,075 Sulfur 0.04 ÷ 0.32

A known method of manufacturing a semi-finished pressing material (see RU Patent No. 21114880, C08L 61 / 10,1998), including the simultaneous grinding and mixing of dry components intended to obtain an impregnating composition by rolling, subsequent dissolution of the crushed and mixed components in a solvent with obtaining an impregnating solution, impregnating the obtained impregnating solution of fibrous and powdery fillers in a paddle mixer, drying the impregnated mass on baking sheets or on a conveyor belt at a rate ture 50-70 ° C for 1-2.5 hours to obtain a semifinished product.

The disadvantages of this method are the significant heterogeneity and dispersion of the density of the manufactured semi-finished product, as well as its lack of fluidity when pressing products from the semi-finished product.

An object of the invention is to improve the quality of the impregnation, the uniform distribution of all ingredients in the volume of the semi-finished pressing material, improving the fluidity of the material when pressing products of complex shapes.

The problem is solved due to the fact that the proposed composition for the manufacture of semi-finished pressing material containing phenol-formaldehyde resin of the resol type in the form of a solution in alcohol, rubber in the form of a solution in butyl acetate, magnesium oxide, zinc oxide, boric acid, sulfur and a fibrous filler, as which use carbon and / or silica yarns characterized in that it contains nitrile butadiene rubber in the form of a solution in butyl acetate and also additionally contains captax in the form of sus a suspension in butyl acetate at a ratio of 1 mass part of coptax to 5 mass parts of butyl acetate, calcium stearate or zinc stearate in the form of a suspension in alcohol in a ratio of 1 to 5 based on 1% by weight of dry impregnating composition, with the following ratio of components in mass parts:

Resol-type phenol-formaldehyde resin in the form of solution concentration (65 ± 5)% of solids in alcohol 35.0 ÷ 65.0 Nitrile butadiene rubber in the form of a solution concentration of 11% ÷ 16% on a dry residue in butyl acetate 5.0 ÷ 10.5 Magnesium oxide 2.0 ÷ 3.0 Zinc oxide 1,0 ÷ 2,0 Boric acid 0.3 ÷ 3.4 Sulfur 1,0 ÷ 2,0 Kaptax in the form of a suspension in butyl acetate at the ratio of 1 mass part of coptax to 5 mass parts of butyl acetate 1,0 ÷ 2,0 Calcium stearate or zinc stearate in suspension (suspension) in the ratio of 1 part of stearate to 5 parts alcohol at the rate of 1% by weight of solids impregnating composition 0.4 ÷ 0.5 Fiberfill 50.0 ÷ 70.0

As a fibrous filler, the composition contains silica filaments, or carbon filaments, or a mixture of silica and carbon filaments in mass parts of 25.0 ÷ 35.0 each.

To speed up the process of polycondensation, the composition for the manufacture of a semi-finished pressing material may additionally contain 0.4 ÷ 0.5 mass. including phosphoronitrile anilide.

The presence of solvents, polymer compounds, and fillers with different compositions makes it possible to activate the appearance of adsorption centers on the surface of fillers and to optimize the adsorption bond of polymers with the surface of fillers.

The proposed composition for the manufacture of semi-finished pressing material with the stated ratio of the components allows to produce a pressing material with stable physical technological properties, to ensure the processing of the semi-finished product into a product by both direct pressing and injection molding. If necessary, an accelerated curing mode, increase labor productivity in the processing of semi-finished products, phosphonitrile anilide (FNA) can be introduced into the composition for the manufacture of semi-finished products. In addition, the impregnation of reinforcing fibrous fillers with an impregnating composition containing several chemical solvents ensures their high-quality impregnation with the appearance on the surface of adsorption centers that enhance the wettability of the fillers and thereby increase the stability of physical properties in the semi-finished product and in the product based on it.

Introduction to the composition for the manufacture of semi-finished nitrile butadiene rubber, calcium stearate or zinc stearate, silica or carbon filaments or a mixture thereof as fibrous fillers allows, depending on operating conditions, to obtain a composition with optimal technological and technical characteristics. In designs exploited at high heat and gas-dynamic flows, to ensure the efficiency of the proposed composition, carbon filaments with a moisture content of not more than 1%, a linear density of 100 or 200, or 400 tex, operable at a temperature of 3500 ° C and silica were selected as fiber reinforcing fillers fibers with a diameter of about 6 microns, a linear density of 200 tex, operable at temperatures up to 1300 ° C, heat treated at a temperature of (600-650) ° C for 30 minutes, or at a temperature of (400-450) ° C, for 6- 7 o'clock, to ensure the technological process of processing fibrous fillers, they are pre-cut into segments with a length of 40 ± 10 mm The introduction of silica or carbon filaments or a mixture thereof also makes it possible to obtain high performance properties depending on operational requirements, in particular during short-term high-temperature gas-dynamic or aerodynamic action due to the thermal resistance of carbon fibers (up to a temperature of 3500 ° C) and due to the low thermal conductivity of silica fibers and high viscosity melt of silicon oxide can increase the life of the product.

The problem is also solved in a method of manufacturing a semi-finished pressing material, which includes the following steps:

- preparation of an impregnating composition in which

a) carry out the formation of a composition for an impregnating composition based on nitrile butadiene rubber by rolling it on cold rollers in two stages, on one of which plasticization of a rubber sample is carried out, during which boric acid is introduced into the rubber sample, and heating on a roller is carried out on the other plasticized weighed rubber with the introduction of sulfur, magnesium oxide, zinc oxide;

b) the rolled composition is dissolved in butyl acetate using a mixer, followed by the introduction of Captax in suspension in butyl acetate into the solution;

C) mix the resulting solution of a composition based on nitrile butadiene rubber dissolved in butyl acetate with a varnish solution of phenol formaldehyde resin in ethanol in a mixer;

- preparation of a fibrous filler, in which the silica and / or carbon filaments are cut into lengths of 40 ± 10 mm and, if a mixture of silica and carbon filaments is used as filler, the chopped filaments are mixed in the mixer;

- impregnation of the fibrous filler with an impregnating composition, in which the prepared fibrous filler is loaded into the mixer, after which the impregnating composition is poured into it, which is pre-poured into a measuring device from the supply tank, and immediately before draining, calcium stearate or zinc stearate in the form of a suspension is added (suspend) in alcohol and carry out mixing;

- drying the impregnated fibrous filler, in which it is discharged from the mixer onto baking sheets or a conveyor belt with a thickness of up to 15 mm and dried at a temperature of not more than 90 ° C, and additionally after drying the semi-finished product is calibrated to a size of not more than 50 ÷ 100 mm by passing through a tear device.

Examples of carrying out the invention

The invention is illustrated by examples of specific performance, in which as starting components use:

Phenol-formaldehyde resin, for example, in the form of varnish LBS-8 Resol-300 according to GOST 901-78;

Rubber nitrile butadiene brand SKN-26-1.25, with a hardness of Defo 400-1000 according to GOST V-52-66;

Magnesium oxide (burnt magnesia) GOST 844-41;

Zinc oxide (zinc white) GOST 202-62;

Boric acid GOST 9656-61; Sulfur GOST 127-58;

Kaptax GOST 739-41;

TU6-09-044-75 calcium stearate or TU6-09-3567-75 zinc stearate;

Ethyl alcohol GOST 18300-72;

Butyl acetate GOST 8981-59;

Acetone GOST 2603-79;

Silica thread grade K11S6-180 according to TU6-02-513-87;

Carbon thread Ural GOST 28005-88 or Ural LO TU 6-06-31-442-85;

Phosphonitrile anilide TU-2637-031-82006400-2010.

EXAMPLE No. 1

Preparation of the impregnating composition

At the stage of preparation of the impregnating composition, preliminary mixing of parts of the starting components (without solvents) is carried out by rolling, dissolving the rolled composition in butyl acetate and then mixing the solution of rolled components in the mixer with a solution of phenol-formaldehyde resin.

The mixing of parts of the initial components of the impregnating composition is carried out by rolling on cold rollers as follows. Plasticization of the rubber weighed on the rollers is carried out, with a gap of 2–3 mm, followed by a decrease in the gap to 0.5 mm. In the process of plasticization, boric acid is introduced into the rubber, in accordance with the formulation. At the end of the plasticization process, the sample is removed from the rollers, the rollers are cooled and then the mass is heated by rolling with a gap of 1 ÷ 1.5 mm for 1 ÷ 2 minutes. In a mixture heated to a temperature of not more than 60 ° C, a portion of sulfur, magnesium oxide, zinc oxide is introduced sequentially.

Then, the obtained rolled composition is dissolved in butyl acetate in the mixer at a rotation speed of the mixer blades of 20 ÷ 60 rpm until the rubber mixture is completely dissolved. The amount of solvent is taken from the calculation of the solution on a dry residue concentration of 11% ÷ 16%.

Upon completion of the dissolution of the rubber composition, a weighed portion of Captax is introduced into it in the form of a suspension in butyl acetate in a ratio of 1 part Captax to 5 parts of butyl acetate. The resulting composition is a homogeneous liquid without clumps of undissolved rubber and impurities. The resulting mixture should correspond in terms of solids equal to 11 ÷ 16%.

Then, an alcoholic varnish solution of phenol-formaldehyde resin is introduced into the impregnation composition in accordance with the recipe.

The varnish is used in the form of a solution in ethanol, the amount of which is taken from the calculation of obtaining a solution with a solids concentration of 63% ± 5%.

The rubber composition is mixed with the varnish solution of phenol-formaldehyde resin in a mixer at a temperature of 18 ÷ 35 ° C, at a rotation speed of the stirrer blades of not more than 60 rpm. In the impregnating composition, after complete mixing of the components, the concentration of the binder is determined by the dry residue.

Fiber Filler Preparation Step

Silica filament of glass No. 11 with a nominal filament diameter of 6 μm and a linear density of 200 tex is cut on a cutting machine into segments of 10–40 mm. When using non-heat-treated silica yarn, it is subjected to heat treatment at a temperature of 600 ÷ 650 ° C for 30 minutes or at a temperature of 400 ÷ 450 ° C for 6 ÷ 7 hours.

Carbon filament with a linear density of 100, or 200, or 400 tex is cut into pieces 10–40 mm long. When the moisture content of the carbon fiber is more than 1%, it is dried at a temperature of 100 ÷ 160 ° C for 1.0 ÷ 1.5 hours.

To obtain a mixture based on silica and carbon filaments, prepared and cut filaments by weight in accordance with the recipe are placed in portions in a mixer and mixed for 10-15 minutes until a homogeneous mass is obtained.

The stage of manufacturing the pressing material

At the stage of manufacturing the pressing material, the fibrous filler is impregnated with an impregnating composition; drying the impregnated filler and calibrating the dried material.

The impregnation of the fibrous filler (silica or carbon filaments, or a mixture thereof) is carried out in a horizontal or vertical mixer, or in a mixer of the Deja type.

First, the amount of silica filaments or carbon filaments, or a mixture of silica and carbon filaments, is loaded into the mixer. Then, the impregnating composition (binder) is poured into the measuring unit from the supply tank in the amount necessary for one batch, based on the calculation of 40 ± 5% of the impregnation composition deposit on the dry residue. Immediately before draining the impregnating composition from the measuring unit, calcium stearate or zinc stearate is introduced into it in the form of a suspension (suspension) in alcohol in a ratio of 1: 5 at the rate of 1% by weight of the dry impregnating composition. The mixture is stirred for 1-3 minutes and poured into a mixer with threads. The mixer is closed and the threads or a mixture of threads are impregnated by stirring for 10 ÷ 20 minutes. If necessary, during the impregnation process, the mixer can be stopped to remove from the blades the adhering mass of the impregnated fibrous filler.

At the end of the impregnation, the material is unloaded from the mixer and laid out on a baking sheet or transport tape with a layer up to 15 mm thick and dried in a stream of heated air to a temperature of no higher than 90 ° C and to a volatile content of not more than 3%.

The obtained semi-finished product of the pressing material is pieces of material in the form of entangled carbon, silica fibers or a mixture thereof, connected by an impregnating composition. To improve manufacturability, the resulting semi-finished product is passed through a grinding device, through which the semi-finished product is calibrated to a size of not more than 100 mm.

Tests of the obtained prefabricated pressing material

Preforms are made from semi-finished products by direct pressing according to the following technology.

In the pre-heated to a temperature of 165 ± 5 ° C. The mold is loaded with a sample of the semi-finished product. The form is closed at a specific pressure of at least 200 kg / cm ² . After holding for 1 ÷ 2 min, prepress is performed by depressurizing to zero. After prepressing, the preform is molded at a temperature of 165 ± 5 ° C and a pressure of at least 200 kg / cm ² with a holding time of 5 ÷ 7 min per 1 mm of the thickness of the preform being formed.

The test results showed high adaptability. Molded blanks exactly repeat the shape, have a clean, glossy surface, without bloating, under-molding and other defects.

Compositions for the manufacture of semi-finished pressing material used in the examples and prototype are shown in table No. 1.

The semi-finished products obtained in examples No. 2, 3, 4, 5, 6, are made according to the technology described in example No. 1.

In examples No. 1-2, carbon filaments are used as filler, in example No. 3 - silica threads, in examples No. 4, 5, 6 - a mixture of silica threads and carbon threads.

In examples No. 4, 5 and 6, phenolic resin is used in the form of a finished LBS-8 varnish solution prepared in accordance with GOST 901-78. Instead of zinc stearate, calcium stearate is used as a release agent.

In examples No. 5 and 6, phosphonitrile anilide is used as an accelerator of the polycondensation process. In these examples, the exposure time during molding at a temperature of (165 ± 5) ° C and a pressure of at least 200 kg / cm ² ranged from 2 ÷ 3 min per 1 mm of thickness. The test results showed that the introduction of phosphonitrile lanide reduces the molding process by the exposure time by 2 times with a slight increase in stiffness. So, the tensile strength slightly increased, and the elongation decreased by 15 ÷ 25%.

Using the proposed composition and method allows to reduce the manufacturing cycle of blanks, to stabilize physical and mechanical properties. Moreover, in products with increased requirements for erosion resistance, it is advisable to recommend a formulation using only carbon filaments. In products that are subject to increased requirements for thermal insulation and high requirements for erosion resistance, it is possible to apply formulations using only silica yarns.

In products requiring moderate heat conductivity and a reduced linear rate of destruction, a composition in which a mixture of silica and carbon filaments is used is recommended.

Claims (11)

1. The composition for the manufacture of semi-finished pressing material containing phenol-formaldehyde resin of the resol type, rubber, magnesium oxide, zinc oxide, boric acid, sulfur and a fibrous filler, which are carbon or silica filaments, characterized in that it contains phenol-formaldehyde resin in the form of a solution in alcohol, nitrile butadiene rubber in the form of a solution in butyl acetate, and also additionally contains captax in the form of a suspension in butyl acetate at a ratio of 1 mass part of captax to 5 mass m parts of butyl acetate, calcium stearate or zinc stearate, with the following component ratio, wt. hours:
Phenol formaldehyde resin rezol type (Resol 300) in the form of a solution concentration (65 ± 5)% of solids in alcohol 35.0 ÷ 65.0 Nitrile butadiene rubber in the form of a solution concentration of 11% ÷ 16% by dry residue in butyl acetate or acetone 5.0 ÷ 10.5 Magnesium oxide 2.0 ÷ 3.0 Zinc oxide 1,0 ÷ 2,0 Boric acid 0.3 ÷ 0.4 Sulfur 1,0 ÷ 2,0 Kaptax in the form of a suspension in butyl acetate at the ratio of 1 mass part of captax to 5 mass parts of butyl acetate 1,0 ÷ 2,0 Calcium stearate or zinc stearate in suspension (suspension) in the ratio of 1 part of stearate to 5 parts alcohol at the rate of 1% by weight of solids impregnating composition 0.4 ÷ 0.5 Fiberfill 50.0 ÷ 70.0 2. The composition according to p. 1, characterized in that as a fibrous filler it contains a mixture of silica and carbon filaments in mass parts of 25.0 ÷ 35.0 each. 3. The composition according to p. 1, characterized in that it additionally contains phosphonitrile anilide in an amount of 0.4 ÷ 0.5 mass. hours 4. A method of manufacturing a semi-finished pressing material according to any one of paragraphs. 1-3, including the following steps:
- preparation of an impregnating composition in which
but. carry out the formation of a composition for an impregnating composition based on nitrile butadiene rubber by rolling on cold rollers in two stages, on one of which plasticization of the rubber sample is carried out, starting heating up with a gap of 2 ÷ 3 mm and then reducing it to 0.5 mm, in the process which boric acid is introduced into the rubber sample, and on the other - heating on the rollers of the plasticized rubber sample with a gap of 1 ÷ 1.5 mm for 1 ÷ 2 minutes to a temperature of not more than 60 ° С with the introduction of sulfur, magnesium oxide, oxide zinc;
b. dissolve the rolled composition in butyl acetate using a mixer at a rotational speed of the blades of 20-60 rpm until it is completely dissolved, followed by the introduction of captax in the form of a suspension in butyl acetate in a ratio of 1 mass. including Captax and up to 5 mass. including butyl acetate;
at. mixing the resulting solution of a composition based on nitrile butadiene rubber with a varnish solution of phenol-formaldehyde resin in a mixer at a temperature of 15 ÷ 35 ° C and a blade rotation speed of not more than 60 rpm;
- preparation of a fibrous filler, in which thread is cut into pieces with a length of 10 ÷ 40 mm;
- impregnation of the fibrous filler with an impregnating composition, in which the prepared fibrous filler is loaded into the mixer, after which the impregnating composition is poured into it, which is previously poured into a measuring device from a supply tank, and immediately before draining, calcium stearate or zinc stearate in the form of a suspension is added to the impregnation composition in alcohol in a ratio of 1: 5 at the rate of 1% by weight of the dry impregnating composition, and mixing is carried out for 10 ÷ 20 min;
- drying the impregnated fibrous filler, in which it is discharged from the mixer onto baking sheets or a conveyor belt with a thickness of up to 15 mm and dried at a temperature of not more than 90 ° C until the content of volatile components in the resulting pressed semi-finished product is not more than 3%, and additionally, after drying, the semi-finished product is calibrated to sizes not exceeding 100 mm by passing through a grinding device,
however, all components of the manufactured composition are taken in an amount corresponding to the recipe. 5. The method according to p. 4, characterized in that use phenol-formaldehyde resin in the form of a ready-made varnish solution in ethanol. 6. The method according to p. 4, characterized in that the obtained impregnating composition is diluted with acetone or alcohol-acetone in a ratio of 1: 1 to a solvent concentration of 68 ÷ 79%. 7. The method according to p. 4, characterized in that silica filaments are used as a fibrous filler. 8. The method according to p. 4, characterized in that when using non-heat-treated silica yarns they are additionally subjected to heat treatment at a temperature of 600 ÷ 650 ° C for 30 minutes or at a temperature of 400 ÷ 450 ° C for 6 ÷ 7 hours. 9. The method according to p. 4, characterized in that the carbon filament is used as the fibrous filler. 10. The method according to p. 9, characterized in that at a moisture content of carbon filaments of more than 1%, they are dried at a temperature of 100 ÷ 160 ° C for 1.0 ÷ 1.5 hours. 11. The method according to p. 2, characterized in that a mixture of silica and carbon filaments is used as a fibrous filler, for which the prepared silica and carbon filaments are placed in a mixer and mixed for 10-15 minutes until a homogeneous mass is obtained.