RU2479422C2 - Polymerisation-impregnation solution for wood modification - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to woodworking, particularly, to wood impregnation. Proposed solution comprises antiseptic and dire retardant dissolved in water, namely, alkaline solution of acetone formaldehyde resin (APR) and ammonium fluorosilicate. Said solution contains Al(OH)₃ nanoparticles or solution "Fiberline 489" at the following ratio of components in wt %: APR - 20.0-22.0, alkali - 0.6-1.1, ammonium fluorosilicate - 2.0-3.0, Al(OH)₃ or "Fiberline 489" - 0.2-0.3, water making the rest.

EFFECT: improved hardwood properties.

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Description

The invention relates to the woodworking industry and the construction industry, and, in particular, to the impregnation of wood.

The polymerization-impregnating solution contains antiseptics and flame retardants dissolved in water. New is that the composition contains an aqueous-alkaline solution of acetone-formaldehyde resin (ACF), ammonium silicofluoride and free phenol scavengers - Al (OH) ₃ nanoparticles or Fiberline 489 solution in the following ratio, wt.%:

ADC 20.0-22.0 Alkali 0.6-1.1 Ammonium silicofluoride 2.0-3.0 Al (OH) ₃ or “Fiberline 489” 0.2-0.3 Water rest

The method of introducing a polymerization-impregnating solution into wood fibers for volumetric modification of wood, which consists in preliminary technological preparation of a polymerization-impregnating solution by sequentially dissolving all the components of the impregnating composition of the solution until it is completely dissolved in hot water at a temperature of 50-60 ° C.

The polymerization-impregnating solution is pumped into the capillaries of previously dried wood by creating a hydraulic pressure of 8-10 MPa in a vacuum pressure chamber and incubating for 2-3 hours. Create a vacuum of 0.8 MPa in a vacuum chamber and incubated for 0.5-1.0 hours. They restore the pressure in the chamber to atmospheric. Prepared wood on pallets is transferred, for example, to a microwave tunnel dryer. The polymerization of the impregnating solution is carried out for 120-300 minutes at a temperature of 75-88 ° C.

Description of the invention

The present invention relates to the field of wood impregnation and can be used in the woodworking and construction industries.

Known solution based on the patent described in [1], for the modification of wood, which after processing acquires increased fire retardant properties and pot life.

In a known polymerization-impregnating solution containing an antiseptic and a flame retardant dissolved in water, the ratio of the components of the impregnating composition is, wt.%:

Phenol alcohols - 25-35

Diammonium phosphate - 9-10

Ammonium Sulphate - 6-7

Urea - 12-20

Ammonia - 2.3-2.7

Water - the rest

The impregnating solution is applied to the surface to be protected with a brush or spray gun until it stops absorbing or dipping. Multiple processing, at least 2-3 steps, with intermediate exposure, forced convective drying is possible. An impregnating solution is prepared at the workplace by sequentially dissolving the components in hot water at a temperature of 50-60 ° C.

In this polymerization-impregnating solution, phenol alcohols, polymerizing in wood during storage and heating, improve its physical and mechanical properties and reduce combustibility. Diammonium phosphate has a fire retardant effect on wood, and urea and ammonia, increasing the pH of the impregnating solution to 8.0-8.50, contribute to the combination of phenol alcohols with diammonium phosphate and are additional flame retardants.

The known composition of the polymerization-impregnating solution has limited use and only in the conditions of an industrial enterprise, since the impregnation of semi-finished products and wood materials is carried out with subsequent curing at a four-step temperature increase with exposure for 9 hours. The result is a fire-resistant wood-polymer material from which the products are made. Wood impregnation is almost superficial.

In addition, the production of fire-resistant materials is classified as hazardous to the health of workers due to the action of phenol on the nervous system of people, causing acute chronic poisoning when exceeding the maximum permissible concentration. The content of phenol vapor in the air of the working area of industrial premises, according to GOST 12.1005-88, should not exceed 0.3 mg / m ³ .

As a prototype of the proposed method of wood modification, taking into account the task and the technical result achieved by solving it - improving the properties of hardwood with a different material structure, the technical solution described in the patent [2] was selected.

In a known polymerization-impregnating solution containing an antiseptic and a flame retardant dissolved in water, the ratio of the components of the impregnating composition is, wt.%:

Phenol alcohols 10-30 Latex 5-15 Urea formaldehyde resin 5-85

The introduction of a significant amount of urea-formaldehyde resin having reactive groups leads to the formation of a more perfect structure of the wood-polymer composite. Since highly polar phenol alcohols penetrate the cell wall of wood, longer rubber molecules fill the cavities of large capillaries, and the urea-formaldehyde polymer, which easily binds to rubber and phenol alcohols, is located throughout the wood capillary system. The deformability of such a three-dimensional polymer network is ensured mainly by rubber molecules bonded to phenol-formaldehyde and urea-formaldehyde polymers.

Obtaining modified wood using a known method is carried out according to the following technology.

KF-90 urea-formaldehyde resin with a hardener (0.25% ammonium chloride) is poured into the container, then a pre-prepared mixture of brand B phenol alcohols (TU-05-1164-81) and stabilized styrene butadiene latex SKS-65P is added. Latex stabilization is carried out with a 10% solution of the emulsifier OP-7. The composition is mixed in a mixer until a uniform light color appears.

To analyze the parameters of the known method of wood modification, samples of birch were taken with dimensions of 10 × 10 × 150 mm (the last dimension along the fibers) with a density of 620 kg / m ³ .

The impregnation was carried out according to the recommended regime: preliminary evacuation for 20 min (vacuum depth 0.005 MPa); pouring of the impregnating solution and exposure of the samples for 2 hours at a pressure of 1.2 MPa. The impregnated samples were dried at 80-90 ° C for 16-18 hours and were subjected to heat treatment for 4-6 hours at 110-120 ° C to cure the modifiers.

As the test results showed, the yield of finished products from 1 m ^{3 of} billets according to the proposed technology amounted to 45-50%.

The production of building materials from modified wood according to technology in accordance with [2] belongs to the category of workers hazardous to health due to the action of phenol on the nervous system of people, causing acute chronic poisoning when exceeding the maximum permissible concentration.

The technical problem addressed by the proposed polymerization impregnation solution for volumetric modification of wood is to expand the technological capabilities of using hardwood by volumetric modification of the wood structure, which contributes to the production of environmentally safe modification of wood with high physicomechanical properties for their subsequent economical use in production of various products.

The polymerization-impregnating solution contains antiseptics and flame retardants dissolved in water. New is that the composition contains an aqueous-alkaline solution of acetone-pharmoldehyde resin (ACF), ammonium silicofluoride and free phenol absorbers - Al (OH) ₃ nanoparticles or Fiberline 489 solution in the following ratio, wt.%:

ADC 20.0-22.0 Alkali 0.6-1.1 Ammonium silicofluoride 2.0-3.0 Al (OH) ₃ or “Fiberline 489” 0.2-0.3 Water rest

To achieve this goal, a polymerization-impregnating solution for volumetric modification of wood is prepared in the following sequence: all components are dissolved sequentially until completely dissolved in hot water, the temperature of which is 50-60 ° C.

The technology for producing modified wood is as follows: the bars are cut to the specified dimensions, given the desired shape, the workpieces are laid on pallets and then fed to a vacuum chamber, where drying is carried out. The wood fibers expand and conditions are created for the free movement of moisture along the wood fibers. Free moisture evaporates both from the surface of the wood and from the internal volume through the wood fibers. During drying, the automatic control system constantly discharges moisture from the vacuum chamber. Wood is dried to a moisture content of 3%. Water removed from the wood is removed from the chamber through shutoff valves. The internal fibers of the wood under the influence of temperature are expanded, the pressure difference inside the fibers and outside, these technological methods contribute to a more complete removal of water and moisture from the capillaries. A polymerization-impregnating solution of the wood structure modifier is fed into the vacuum chamber in an amount that ensures complete immersion of the wood and filling the chamber, a hydraulic pressure of 8-10 MPa is created for 2-3 hours, due to which the impregnation solution penetrates into the prepared wood capillaries. Then a vacuum of 0.8 MPa is created and exposure is carried out for 0.5-1.0 hours. Under the influence of vacuum, an impregnating solution is pumped into the capillaries of the wood.

The pressure in the vacuum chamber is restored to atmospheric. Due to the pressure difference (low inside the processed material and atmospheric in the chamber), the modifying composition completely penetrates the wood capillaries.

Prepared wood on pallets is transported, for example, into a microwave tunnel dryer. Drying time 2-5 hours at a temperature of 75-88 ° C, where further drying and polymerization takes place. This technological sequence provides an increase in the yield of defect-free wood up to 70-90%. Wood does not crack and does not warp.

The reduction of volumetric stresses, the improvement of contact interactions between wood fibers, during the implementation of a given modification mode, is provided by the temperature of the polymerization process, which does not exceed 95 ° C, and internal stresses do not exceed the limit values of the mechanical strength of wood fibers. The cooling process is carried out in air outside the microwave dryer.

As a result of the technological methods and modes described above, the modified wood sample has a high density that is significantly higher in magnitude than the density of the original wood sample, while the density of the sample is stable in volume. At full processing depth, microcracks are removed from the surface layer of the wood billet formed as a result of traditional technological exposure, the physicomechanical properties of wood and fire safety are increased.

The stabilization mechanism of modified wood: when the polymerization-impregnating solution is heated to 88 ° C in a slightly alkaline medium, the polymer resin polycondensates to form linear macromolecules. The reaction of cellulose with ACF in a polymerization-impregnating solution proceeds with the formation of esters. ACP resin also interacts with lignin. Lignins are amorphous macromolecular compounds of aromatic nature built from phenylpropane units. The natural polymer is reinforced with an impregnating composition with the formation of a new wood property. Physico-mechanical characteristics of natural wood and prototype are presented in table 1.

Table 1 Comparative characteristics of natural wood and prototype Breed Characteristic Density, g / cm ³ End hardness, MPa Bending Strength, MPa Compressive strength, MPa Abrasion wear, mm Moisture absorption in 24 hours in water,% Birch 0.63 44 85 fifty 0.5-0.6 70-80 Birch (prototype) 0.75 61 120 70 0.3-0.4 5-8 Aspen 0.47 28 75 36 1,2 70-95 Modified Aspen (prototype) 0.77 65 110 61 0.7 7-10 Oak 0.65 34 98 64 0.7-0.9 70-80 Modified Oak (prototype) 0.82 70 135 80 0.42-0.5 7-9

Physico-mechanical characteristics of natural wood and the claimed subject matter are presented in table 2.

table 2 Comparative characteristics of natural and modified wood Breed Characteristic Density, g / cm ³ End hardness, MPa Bending Strength, MPa Compressive strength, MPa Abrasion wear, mm Dehumidifier
24 hours in water,% Birch 0.63 44 85 fifty 0.5-0.6 70-80 Birch 0.9 one hundred 180 90 0.21 3-6 (proposed) modified Aspen 0.47 28 75 36 1,2 70-95 Aspen (Offered) 0.9 one hundred 140 one hundred 0.35 3-6 modified Oak 0.65 34 98 64 0.7-0.9 70-80 Oak (offered) 0.89 120 166 110 0.15-0.3 2.4-4.0 modified

The introduction of an Al (OH) ₃ nanoparticle or Fiberline 489 solution into the polymerization-impregnating solution promotes the absorption of free phenols, which makes it possible to classify this polymer-modified wood as a hazard category 4. An analysis of the results showed that the best results were obtained when the wood was impregnated with the ADC modifier according to the proposed technology for all tested wood species. The compressive strength along natural wood fibers corresponds to birch 50 MPa, aspen 36 MPa, oak 64 MPa, the strength of birch wood after impregnation and polymerization is 100-130 MPa, aspen 100-120 MPa and oak 110-126 MPa.

The strength of oak modified by the proposed technology increased by 38% compared with the modification of the prototype and by 72% compared with the control. Aspen, modified by the proposed technology, increased compressive strength compared with the modification of the prototype by 64% and compared with natural wood by 177%.

Birch, modified by the proposed technology, increased compressive strength compared to the modification of the prototype by 29%, and compared with natural wood by 80%.

The moisture absorption in water of modified wood in 24 hours does not exceed 2-8% for all the studied species of wood compared with 70-80% moisture absorption of natural wood.

Literature

1. Patent: 2147028; Class (s) of patent: C09K 21/04, C09D 5/16, B27K 3/52, B05D 7/06; Application Number: 99106231/04; Application submission date: 04/06/1999; Date of publication: 03/27/2000.

2. A.S. USSR 2065355; MKI B27K 3/34, B27K 3/50, 1996;

Patent: 2065355; Class (s) of patent: B27K 3/34, B27K 3/50;

Application Number: 5055017/04; Application submission date: 05/22/1992;

Date of publication: 08.20.1996.

Claims (1)

A polymerization-impregnating solution containing an antiseptic and a flame retardant dissolved in water, characterized in that the composition contains an aqueous-alkaline solution of acetone formaldehyde resin (ACP), ammonium silicofluoride and free phenol absorbers — Al (OH) ₃ nanoparticles or Fiberline 489 solution in the following the ratio of components, wt.%:
ADC 20.0-22.0 Alkali 0.6-1.1 Ammonium silicofluoride 2.0-3.0 Al (OH) ₃ or “Fiberline 489” 0.2-0.3 Water Rest