RU2332432C1 - Thermally-hardened composition for impregnation and hermetisation of porous products and method of impregnation and hermetisation with its use - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to impregnation and hermetisation of porous products with thermally hardened compositions based on (meth)acrylic monomers. Claimed is thermally hardened composition for impregnation and hermetisation of porous products, containing (in mass fraction): 100 (meth)acrylic monomer, 0.1-0.5 nitronitrile, 0.01-0.04 hydrohynone, 0.004-0.03 disodium salt of ethylendiaminetetraacetic acid, 0.001-0.03 2,2,6,6-tetramethyl-4-oxopiperidin-1-oxyl and 0.5-5.0 non-ionogenic emulsifying agent. Method of impregnation and hermetisation of porous products includes their vacuum processing with further impregnation under vacuum and atmospheric pressure with abovementioned composition and hardening at temperature ≥90°C. Thermally-hardened composition has higher serviceability and allows to increase productivity of impregnation and hermetisation method essentially.

EFFECT: increasing productivity of method of impregnation and hermetisation of porous products by means of thermally-hardened compositions.

2 cl, 1 tbl, 15 ex

Description

The invention relates to the field of impregnation and sealing of porous products with thermosetting compositions based on (meth) acrylic monomers and, above all, to the field of vacuum impregnation of porous castings from various metals, powder metallurgy products, welds.

In many areas of technology, parts from various metals and their alloys obtained by casting or powder metallurgy are traditionally used.

However, even with advanced technologies for their manufacture, they have pores, microcracks, which leads to leakage of products, lower strength and, consequently, to unreliability and short life.

An effective, economically viable way to restore the mechanical properties of such castings and their sealing is to impregnate with liquid compositions, which under certain conditions are cured in casting defects and thus seal and harden parts.

Among the variety of impregnating compositions, radical curable compositions based on (meth) acrylic monomers and oligomers occupy a special place. This is due to their low viscosity and ease of penetration into the smallest gaps, the ability to control adhesive and cohesive strength, high curing speed, ability to rinse with water, stability during storage and in the conditions of use.

The most commonly used method in the industry is vacuum impregnation. Parts are evacuated in an autoclave to free pores from the air. Then, the impregnating composition is fed into the autoclave under vacuum, after a certain time the vacuum is vented by air and the impregnation is carried out at atmospheric or elevated pressure. After impregnation, excess sealant drains, and its residues on the surface are washed off with water. The impregnated product is immersed in a container where, under the action of hot water, the impregnated composition is cured and the products are sealed. The most optimal curing temperature is 90-98 ° C, at which there is no intensive evaporation of water due to boiling and at the same time, high curing rates are achieved.

An important property that determines the suitability of the composition for impregnation and sealing is the time before gelation begins at the curing temperature. The optimal gelation time should be 3-8 minutes at a temperature of 90 ° C. If the time before gelation begins is more than 8 minutes, the composition due to thermal expansion flows out of the pores before it has time to harden. In this case, the product is not sealed. If the time before gelation is less than 3 minutes, then the composition is unstable, its premature spontaneous polymerization during impregnation or storage is possible.

The performance of the impregnating composition is determined by the number of cycles of impregnation of porous products while maintaining the time before gelation within 3-8 minutes at a temperature of 90 ° C.

The impregnating composition must withstand at least 100 cycles of impregnation, including degreasing of the products, placing them in the impregnating composition, followed by evacuation and exposure to atmospheric or high pressure. The impregnating composition, while retaining its properties for 100 cycles or more, is operable with intensive use in production for 1 month or more.

The authors of the invention had the task of improving the performance of the impregnating composition, increasing its stability during prolonged contact with metals and increasing the productivity of the method of impregnation and sealing of porous products.

In the study of the prior art, the following published compositions for impregnation of porous products and methods of impregnation using them were identified.

Thus, a known composition for the impregnation of porous products, mainly for vacuum impregnation of metal castings according to US patent No. 4147821, 41B 41/63, 1979, containing, wt.%:

monofunctional (meth) acrylic monomer 60-98 polyfunctional monomer 2-40 free radical initiator 0.1-5 inhibitor 0.01-2 emulsifier to 10

Butyl acrylate, 2-ethylhexyl acrylate, hydroxyethyl methacrylate, stearyl methacrylate are proposed as a monofunctional monomer.

Of the multifunctional monomers, allyl methacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, trimethylolpropane trimethacrylate are used. The initiator of polymerization is peroxide compounds (benzoyl peroxide, tert-butyl perbenzoate, etc.), as well as azobis (isobutyronitrile). The inhibitor is hydroquinone, benzoquinone, methylene blue.

In this patent, porous articles are impregnated with the above composition under vacuum at 5-20 mmHg. for 5-10 minutes, then increase the pressure to atmospheric and solidify at a temperature of 80-90 ° C with mostly hot water for 10-15 minutes.

The description of the patent shows positive results for testing impregnated and cured steel and brass parts for tightness with a pressure of ~ 5.6 kg / cm ² . However, the performance of this composition was not high. The composition prepared according to this patent after 12 cycles of impregnation spontaneously polymerized.

Also known is an impregnating composition for porous metal products, for example, from aluminum (German application No. 4311387, C09D 4/00, 1974). It contains, wt.%:

hydroxyethyl methacrylate 50-80 higher alcohol methacrylate (2-ethylhexyl, lauryl, dodecyl) 10-40 triethylene glycol dimethacrylate 5 initiator-2,2'azobisisobutyronitrile 0.1 emulsifier (polyoxyethylene alkyl phenol) 10 inhibitor (hydroquinone monomethyl ether, ionol) 0.025 (250 p.p.m)

The impregnation method according to the application of Germany includes evacuation of products and impregnation with a composition at 1-3 mbar (0.7-2.1 mm Hg) for 5 minutes and curing in hot water at a temperature of 90 ° C for 10-12 minutes .

The disadvantage of this composition is the instability of the polymerization properties during impregnation cycles. After 6 cycles of impregnation, the composition is polymerized, which indicates its low performance.

Also known is a composition for impregnating products of powder metallurgy and porous casting (RF patent No. 1135175, C09K 3/10, 1995), containing, by weight:

polyethylene glycol dimethacrylate or its mixture with octyl methacrylate in the ratio (3-4): 1 one hundred 4,4'-azo-bis (4,4'-cyan) pentanoic acid 0.1-0.2 surface-active substance 0.5-2 inhibitor (hydroquinone, ionol) 0.005-0.03

The method of impregnation and sealing includes the exposure of porous products in the specified composition for 15 minutes at 2 mm Hg and for 15 minutes at atmospheric pressure, followed by curing at 80-90 ° C in hot water for 15-30 minutes.

The specified composition has a time until gelation at 80 ° C ~ 10 min. In addition, the 4,4'-azo-bis (4,4'-cyan) -pentanoic acid initiator (4a4c) used in this composition is an organic acid. And since aqueous solutions with an alkaline reaction, for example, based on sodium polyphosphate, are used to degrease parts, the impregnation of such parts results in a gradual neutralization of 4-4c and a decrease in the concentration of initiator in the composition. In industrial conditions, when a large number of parts are impregnated, the polymerization activity of the composition decreases. The time before gelation begins increases until complete decontamination, which reduces the productivity of the process or makes it impossible.

The closest in technical essence to the claimed composition for impregnation and sealing of porous products and the method of impregnation with its use are the composition and method of impregnation according to US patent No. 4416921, C08F 2/00, 1983 - prototype. This patent protects a thermoset composition for impregnating porous articles containing azonitrile, a polymerizable acrylic monomer, substituted sterically hindered phenol (phenolic antioxidant), a metal ion complexing agent.

The composition may further comprise an anionic or nonionic surfactant. As the azonitrile, 2,2'-azobis (isobutyronitrile) is preferably used. Substituted phenol is selected from the group of 2,6-ditretbutyl-para-cresol and 2,5-di-tert-butylhydroquinone. As a complexing agent of metal ions, 1,2-bis (2'-pyridylmethyleneamino) ethane, 1,2-bis (6-methyl-2-pyridylmethyleneamino) ethane, a derivative of polycarboxylated alkylenediamines, for example, ethylenediaminetetraacetic acid tetrasodium salt, etc. are used.

The method of impregnation of porous products with the specified composition includes the stage of vacuum impregnation at a pressure of 25 mm Hg for 2-10 minutes and impregnation at atmospheric pressure, followed by curing at 80-100 ° C for 1-15 minutes in water.

The time to gelation of such a composition at 82 ° C is 4 minutes, the time of complete cure is 5 minutes. It has high storage stability and maintains curing speed during long exposure. However, the reproduction of the patent showed that the composition does not withstand prolonged contact with metals. It withstands only 20 cycles of impregnation, which is insufficient for its industrial use.

The aim of the invention is to improve the health of the thermoset composition for impregnation and sealing of porous products and increase the productivity of the method of impregnation and sealing of porous products.

To increase the operability, a thermoset composition for impregnation and sealing of porous products containing (meth) acrylic monomer, azonitrile, ethylene diamine tetraacetic acid salt, nonionic emulsifier and phenolic antioxidant contains hydroquinone as phenolic antioxidant and 2 additional ethylene diamine di tetraacetic acid salt , 2,6,6-tetramethyl-4-oxopiperidin-1-oxyl in the following ratio of components of the composition, parts by weight:

(meth) acrylic monomer one hundred azonitrile 0.1-0.5 hydroquinone 0.01-0.04 disodium salt of ethylenediaminetetraacetic acid 0.004-0.03 2,2,6,6-tetramethyl-4-oxo-piperidin-1-oxyl 0.001-0.03 nonionic emulsifier 0.5-5.0

To increase productivity in the method of impregnation and sealing of porous products, including vacuum treatment, impregnation under vacuum, and then at atmospheric or elevated pressure with a thermoset composition based on a (meth) acrylic monomer and curing at a temperature of ≥90 ° C, porous articles are impregnated with the proposed thermoset composition, above.

The (meth) acrylic monomer used was (poly) ethylene glycol dimethacrylates — ethylene glycol dimethacrylate (DMEG), triethylene glycol dimethacrylate (TGM-3), polyethylene glycol dimethacrylate (TGM-13), and mixtures thereof with mono (meth) acrylate acrylate-octate-octyl acrylates ethylene glycol methacrylate (MEG), propylene glycol methacrylate (PGM), methoxyethylene glycol methacrylate (MDEM), decyl methacrylate (DMAK).

Azonitriles were used as the initiator, for example, 2,2'-azobis (isobutyronitrile) (ADN), 2,2'-azobis (2,4-dimethylvaleronitrile) (ADMVN), 2,2'-azobis (2-methylbutyronitrile) (AMBN )

Monoalkylphenyl ethers of polyethylene glycol (OP-7, OP-10) and polyoxyethylene glycol ethers of synthetic primary higher alcohols (ALM-10, ACSE-12) were used as a nonionic emulsifier.

The following are specific examples illustrating the essence of the invention.

Example No. 1

In a glass reactor at room temperature, 80 parts by weight were mixed. TGM-4, 20 parts by weight MDEM, 0.3 parts by weight ADMVN, 0.018 parts by weight hydroquinone, 0.01 wt.h. disodium salt of ethylenediaminotetraacetic acid (trilon B), 0.03 wt.h. 2,2,6,6-tetramethyl-4-oxo-piperidin-1-oxyl (nitroxyl-1) and 5 parts by weight OP-10.

The time to gelation (the appearance of polymer clots) of the composition, determined in a tube thermostatted at (90 ± 1) ° С, filled with the composition to a height of 3-3.5 cm, was 5 min.

The vacuum impregnation cycle was carried out as follows.

A sample made of aluminum casting was dipped in a 5% aqueous solution of sodium polyphosphate at 70 ° C, kept for 3-5 min, and then dried. A defatted sample was placed in an autoclave, evacuated for 5 min at 10–20 mm Hg, the autoclave was filled in a vacuum with an impregnating composition, and impregnated under the same vacuum for 7 minutes. The pressure was increased to atmospheric and held for 5 minutes. The surface of the parts was washed from the remains of the composition with water at 20-40 ° C, then the parts were placed in a tank with hot (90 ° C) water and held for 15-30 minutes. Sealant hardened.

The performance of the composition was determined by the number of impregnation cycles, during which the time before gelation was within the acceptable range.

The test results of the composition are shown in the table.

Examples No. 2-7 (according to the invention)

The impregnation method and test methods according to example No. 1. The composition and test results are shown in the table.

Example No. 8 (according to the invention)

The impregnation method according to example No. 1, only the impregnation is carried out at a pressure of 5 atm. Test methods for example No. 1. The composition and test results are shown in the table.

Examples No. 9-15 (for comparison)

The impregnation method and test methods according to example No. 1. The composition and test results are shown in the table.

Table
The composition and properties of the thermoset composition No pp The composition of the thermoset composition Time before gelation Components parts by weight source after 100 cycles of impregnation one 2 3 four 5 one TGM-4 80 5 6 MDEM twenty ADMVN 0.3 OP-10 5 hydroquinone 0.018 Trilon B 0.01 nitroxyl-1 0,03 2. DMEG 90 7 7 DMAK 10 ADN 0.15 ACSE 0.5 hydroquinone 0.04 Trilon B 0.008 nitroxyl-1 0.01 3. TGM-3 twenty four 5 MEG 75 OMAC 5 ADN 0.1 ALM-10 3 hydroquinone 0.02 Trilon B 0,03 nitroxyl-1 0.02 four. TGM-13 fifty 3 5 IPY fifty AMBN 0.5 OP-7 2 hydroquinone 0.015 Trilon B 0.02 nitroxyl-1 0.001 5. TGM-3 97 7 6 MEG 3 ADN 0.25 OP-10 one hydroquinone 0.01 Trilon B 0.015 nitroxyl-1 0,022

Table continuation

one 2 3 four 5 6 TGM-3 10 6 8 IPY 60 MDEM thirty AMBN 0.4 ALM-10 3,5 hydroquinone 0,03 Trilon B 0.004 nitroxyl-1 0.015 7. TGM-3 one hundred 3 3 ADN 0.12 OP-7 4,5 hydroquinone 0,025 Trilon B 0.007 nitroxyl-1 0.005 8. TGM-3 one hundred 5 6 ADN 0.25 OP-7 3 hydroquinone 0.02 Trilon B 0.01 nitroxyl-1 0.01 For comparison 9 (prototype) TGM-3 99,759 3 the composition polymerized after 20 cycles ADN 0.2 2,6-ditretbutyl-4-methylphenol 0.04 Trilon B 0.001 OP-7 3.0 10 TGM-3 10.0 0.5 the composition polymerized after 10 cycles ADN 0.25 OP-7 3 hydroquinone 0.02 Trilon B 0.01 eleven TGM-3 one hundred 2 the composition polymerized after 50 cycles ADN 0.25 OP-7 3 Trilon B 0.01 nitroxyl-1 0.01

Table continuation

one 2 3 four 5 12 TGM-3 one hundred one the composition polymerized after 30 cycles ADN 0.25 OP-7 3 hydroquinone 0.02 nitroxyl-1 0.01 13 TGM-3 one hundred four the composition polymerized after 70 cycles ADN 0.25 OP-7 3 2,6-ditretbutyl-4-methylphenol 0.02 Trilon B 0.01 nitroxyl-1 0.01 fourteen TGM-3 one hundred 5 the composition polymerized after 30 cycles ADN 0.25 OP-7 3 hydroquinone 0.02 γ-bipyridyl 0.01 nitroxyl-1 0.01 fifteen TGM-3 one hundred 3 the composition polymerized after 15 cycles ADN 0.25 OP-7 3 hydroquinone 0.02 Trilon B 0.01 2,2,6,6-tetramethyl-4-hydroxy-piperidin-1-oxyl 0.01

The table shows that the claimed composition of the thermoset composition containing (meth) acrylic monomer, nonionic emulsifier, azonitrile, hydroquinone, disodium salt of ethylenediaminetetraacetic acid and 2,2,6,6-tetramethyl-4-oxo-piperidine-1-oxyl, allows you to achieve the optimal time before gelation, which is 3-8 minutes and allows you to maintain the performance of the composition up to 100 cycles of vacuum impregnation, which is much higher than the prototype, the operability of which is 20 cycles of impregnation (see examples №1-8 versus №9).

The data in the table also show (see examples No. 10-12) that the use of binary systems hydroquinone - trilon B, trilon B - nitroxyl-1 and hydroquinone - nitroxyl-1 leads to premature polymerization of the compositions during impregnation cycles.

When replacing hydroquinone with other hydroxyl-containing antioxidants, for example 2,6-ditretbutyl-4-methylphenol, the composition polymerizes after 70 cycles of impregnation (see example No. 13).

When replacing Trilon B with other complexones, for example, γ-bipyridyl, the composition polymerizes after 30 cycles of impregnation (see example No. 14).

When replacing nitroxyl-1 with other aminoxyl radicals, for example 2,2,6,6-tetramethyl-4-hydroxy-piperidin-1-oxyl, the composition also polymerizes prematurely (see example No. 15).

All of the above suggests that the use of a ternary mixture of hydroquinone, trilon B and nitroxyl-1 in the indicated amounts as a stabilizer of the composition made it possible to obtain an unexpected synergistic effect in increasing the performance of the composition, which turned out to be higher than expected.

In compositions containing hydroquinone, disodium salt of ethylenediamine-tetraacetic acid and 2,2,6,6-tetramethyl-4-oxo-piperidin-1-oxyl in amounts less than the declared 0.01 wt.h. 0.004 parts by weight and 0.001 parts by weight accordingly, the time before gelation begins is less than 3 minutes and, when impregnation cycles are carried out, they polymerize prematurely.

In compositions containing hydroquinone, disodium salt of ethylenediamine-tetraacetic acid and 2,2,6,6-tetramethyl-4-oxo-piperidin-1-oxyl in quantities greater than 0.04 parts by weight, 0.03 parts by weight . and 0.03 parts by weight accordingly, the time before gelation begins is more than 15 minutes, which makes their use non-technological.

The limits of application of the azo initiator are limited: the upper limit - a porous polymer is formed that does not have the necessary operational properties (the tightness of the impregnated products is broken); the lower limit is the time before the polymerization of compositions increases to 20 minutes or more, which makes their use low-tech.

The limits of use of nonionic emulsifiers are limited:

- upper limit - during the cycles of impregnation a large amount of foam is formed, the resulting polymer is loose, does not have the necessary physical and mechanical properties;

- lower limit - the composition is not washed off from the surface of the parts.

The use in the method of impregnation and sealing of porous products of the claimed composition can significantly improve the performance of the method of impregnation and sealing. The specified impregnating composition can withstand 100 and more cycles of impregnation with the preservation of time before gelation. In the conditions of the existing production, this allows to increase the time until the impregnating composition is replaced with a newly prepared composition without compromising the quality of impregnation and sealing of molded products.

Claims (2)

1. A thermoset composition for impregnating and sealing porous products containing (meth) acrylic monomer, azonitrile, ethylenediaminetetraacetic acid salt, nonionic emulsifier and phenolic antioxidant, characterized in that it contains hydroquinone as a phenolic antioxidant, and salt of ethylene diamine tetraacetic acid ethylenediaminetetraacetic acid and additionally 2,2,6,6-tetramethyl-4-oxo-piperidin-1-oxyl in the following ratio of components of the composition, parts by weight: (meth) acrylic monomer one hundred azonitrile 0.1-0.5 hydroquinone 0.01-0.04 disodium salt of ethylenediaminetetraacetic acid 0.004-0.03 2,2,6,6-tetramethyl-4-oxo-piperidin-1-oxyl 0.001-0.03 nonionic emulsifier 0.5-5.0 2. The method of impregnation and sealing of porous products by evacuating them, followed by impregnation under vacuum and atmospheric or elevated pressure with a thermoset composition based on a (meth) acrylic monomer and curing at a temperature of ≥90 ° C, characterized in that the porous articles are impregnated with a thermoset composition according to claim .one.