CN102152356A - Method for preparing densified woods through silica sol - Google Patents

Abstract

The invention relates to a method for preparing reinforced wood with silica sol, in particular to a preparation technology for impregnating wood with silica sol. Its steps are, the selection of silica sol raw materials, the deployment of silica sol, and impregnation enhancement: vacuumize the impregnation treatment tank for the first time, then inject the silica sol impregnation treatment liquid, and perform pressure treatment. The applied pressure is 0.8 MPa ~ 1.5 MPa Pa, then carry out a second vacuum treatment, and finally take out the impregnated wood; then carry out health preservation, graded drying; finally take out the reinforced modified wood. Therefore, due to the low price and high stability of silica sol, the cost of wood products is reduced, and the particle size of silica particles in silica sol is small, and the performance of the composite wood prepared by entering the wood is uniform, and the mechanical properties of the wood cell wall are obvious. Improvement greatly improves the strength and hardness of wood products.

Description

Method for preparing reinforced wood with silica sol

technical field

The invention relates to a method for preparing reinforced wood with silica sol, in particular to a preparation technology for impregnating wood with silica sol.

Background technique

At present, the output value of China's furniture and flooring industry ranks first in the world, and the high-end furniture and flooring industry mainly uses solid wood as raw materials, and these raw materials are mostly wood with high strength and good dimensional stability. As people's demand for solid wood increases, the availability of high-strength wood for consumption is gradually decreasing. In recent years, the timber resources supplied by our country are mainly plantation timbers. The materials of these timbers are poor, their strength is low, and their strengths vary greatly, so it is difficult to directly use them for solid wood processing. For this reason, in recent years, the method of impregnation treatment is often used to improve the wood material, improve its strength, hardness and shrinkage resistance.

Impregnation treatment refers to the process of injecting impregnation hydraulic pressure into the wood, and then curing the treatment liquid by heating and depositing it in the wood. Such as Chinese patent ZL200810013225.5 "Technical method of synthetic resin impregnated wood modification", Chinese patent ZL201010214843.3 "Technical method of synthetic resin impregnated wood modified" and US patent USD4031276 "Phenolic resin impregnated to prepare reinforced wood" (Preparation of densified wood impregnated with phenolic resins).

The dipping treatment liquids in the above methods are all synthetic resins or modified synthetic resins (phenolic resins). After impregnation treatment and drying and curing, most of the synthetic resin is deposited and filled in the cell cavity of the wood, and only a small amount enters the cell wall of the wood. Wood is a porous, layered, anisotropic heterogeneous natural polymer composite material. Its ultrastructure is a cell wall composed of layers of different thicknesses. The performance of the cell wall is the main factor determining the performance of wood. . Therefore, the improvement of wood strength and dimensional stability by the treatment method of physically filling the cell cavity with synthetic resin is limited. In addition, since the diameter of the pores on the wood cell wall is 1-50 nanometers, the impregnated synthetic resin can rarely enter the wall layer of the wood cell wall to achieve the effect of overall infiltration of the wood, which may easily cause problems such as uneven product performance. Furthermore, the strength and hardness of the synthetic resin itself that enters the wood cell cavity are 3.1GPa and 0.1GPa, which are far lower than the strength and hardness of the untreated wood cell wall. Therefore, even if a small amount of synthetic resin enters the wood cell wall, the wood The effect of strength and hardness is also not obvious.

Contents of the invention

The purpose of this invention is to provide a kind of method that prepares reinforced wood with silica sol, mainly replace conventional synthetic resin or modified synthetic resin (phenolic resin) with silica sol as impregnating treatment liquid, and carry out impregnating strengthening treatment, make a large amount of The silica sol is deposited in the parietal layer of the wood's cell walls.

The purpose of the present invention is achieved like this:

A method for preparing reinforced wood with silica sol, the steps of which are:

1) Selection of silica sol raw materials: select silica sol with a pH (hydrogen ion concentration index) value of 8 to 11, a density of 1.15 to 1.35 g/cm ³ , a silica content of 10% to 35%, and a particle size of silica sol Alkaline silica sol with a diameter concentrated between 5 and 40 nanometers;

2) Silica sol preparation: prepare the silica sol with hydrochloric acid, adjust the pH value of the silica sol to 6.5-7.5, and obtain the silica sol impregnation treatment solution;

3) Impregnation enhancement: put wood with a moisture content of 8% to 30% into the impregnation tank, and vacuumize the impregnation tank for the first time for 10 to 30 minutes, and the vacuum degree is -0.080 MPa to -0.095 MPa, Then inject the silica sol impregnation treatment liquid, carry out pressure treatment, apply pressure at 0.8 MPa ~ 1.5 MPa, keep for 30 ~ 60 minutes, then release the pressure, return the silica sol treatment liquid in the pressure impregnation tank to the solution storage tank Middle; carry out the second vacuum treatment, the vacuum degree is -0.080 MPa ~ -0.095 MPa, and the treatment time is 5 ~ 20 minutes; finally take out the impregnated wood;

4) Health preservation: put the impregnated wood at room temperature for more than 24 hours, and place wooden spacers between the layers;

5) Graded drying: Put the cured wood into the oven, place spacers between the wood; first force convection drying at 30°C for 3-6 hours, then raise the temperature to 80°C, and force convection drying for 1-6 hours hours, then the temperature is raised to 100-105° C., forced convection drying is performed for 3-6 hours, and finally the reinforced modified wood is taken out.

Selection of the silica sol raw material: select commercially available alkaline silica sol, the pH value of the silica sol is 8, the density is 1.21g/cm ³ , the silica content is 25%, and the particle size of the silica sol is concentrated Between 8 and 20nm.

The preparation of the silica sol: the pH value of the silica sol is 7.22.

The impregnation enhancement treatment: put the artificial forest fir wood with a moisture content of 15% into the impregnation treatment tank, and vacuumize the impregnation treatment tank for 10 minutes, and the vacuum degree is -0.095 MPa.

The graded drying: the cured wood was forced convection dried at 30°C for 5 hours, then heated to 80°C, forced convection dried for 4 hours, then heated to 103°C, forced convected dried for 5 hours.

The beneficial effect of the object of the present invention is: because silica sol is cheap, and stability is extremely high, wood product cost reduces, and the particle size of the silica particle in silica sol is smaller, and the performance of the composite wood that enters wood preparation is even, The mechanical properties of wood cell walls are significantly improved, which greatly improves the strength and hardness of wood products.

Detailed ways

The present invention will be further described below in conjunction with typical embodiments.

Silica sol of the present invention prepares the method for strengthening wood, and its steps are as follows:

1) Selection of silica sol raw materials: select commercially available alkaline silica sol, the pH value of the silica sol is about 8, the density is about 1.21g/cm ³ , the silicon dioxide content is about 25%, and the silica sol The particle size is concentrated between 8 and 20nm, and the particle size distribution is uniform. Then, the silica sol was filtered with a strainer to remove possible suspended impurities in the commercially available silica sol. Select a commercially available silica sol with a pH of 8-11, a density of 1.15-1.35g/cm ³ , a silica SiO ₂ content of 10%-35%, and a SiO ₂ particle size concentrated between 5-40 nanometers Silica sol as raw material.

Silica sol is a colloidal solution in which silica particles are uniformly dispersed in water. Compared with synthetic resins, silica sol has higher physical and mechanical properties, and is often used as a reinforcing treatment agent and wear-resistant treatment agent; at the same time, silica sol has a larger specific surface area, generally 250-300m ² /g, with Larger adsorption, easy to infiltrate wood through capillary action, and form a stable chemical bond with the chemical composition of wood cell wall; Pores, deposited in the parietal layer of the wood's cell walls. In addition, silica sol is a colorless, odorless, and transparent colloidal solution. Compared with synthetic resins, there is no harmful and toxic substances such as formaldehyde, and it is cheap and easy to obtain.

2) Silica sol formulation: at room temperature, add hydrochloric acid into the container containing the silica sol under the stirring of an electric mixer to obtain a solution with a pH value of 7.22. This solution is the impregnation solution for preparing reinforced composite wood.

3) Impregnation enhancement treatment: put the artificial forest fir wood with a specification of 500 mm × 80 mm × 20 mm and a moisture content of 15% into the impregnation tank, close the tank door, turn on the vacuum pump, and when the vacuum reaches the target pressure, Vacuum the treatment liquid into the treatment tank, and vacuum the impregnation tank for 10 minutes with a vacuum degree of -0.095 MPa to extract the air in the wood cell cavity so that the wood is easily soaked by the treatment liquid and reduce the pressure during pressure relief. The treatment liquid recoils out, leaving more of the treatment liquid in the wood.

Then turn off the vacuum pump and carry out the pressure treatment. The applied pressure is 1.0 MPa and kept for 40 minutes, so that the treatment liquid is deeply pressed into the wood, and the wood no longer absorbs the treatment liquid. If the vacuum pump is turned off before the impregnation of the wood reaches saturation, the air remaining in the impregnation tank will be compressed to the upper part of the impregnation tank, and then when the treatment solution is continued to be added, the gas will be filled into the wood on the upper part of the treatment tank The space that is evacuated during vacuuming allows this part of the wood to absorb a small amount of treatment liquid, resulting in uneven results for the same batch of treated wood.

Then the pressure is released, and the treatment solution in the pressure infusion tank is returned in the solution storage tank; the vacuum pump is connected again, and the vacuum treatment is carried out for the second time, and the vacuum degree is -0.095 MPa, and the treatment time is 5 minutes; finally, the vacuum is released , open the tank door, and take out the impregnated wet material.

4) Health preservation: place the impregnated wet fir wood at room temperature for 24 hours, and place wooden spacers between the layers.

5) Graded drying: Put the cured wood into the oven, place spacers between the wood; firstly dry it by forced convection at 30°C for 5 hours; then raise the temperature to 80°C, and dry it by forced convection for 4 hours; then raise the temperature to 103 ℃, forced convection drying for 5 hours; finally stop drying, open the oven, and take out the reinforced modified wood.

The mean value of the flexural strength of the Chinese fir composite wood strengthened and modified by the present invention is 87.70MPa, the mean value of the flexural modulus of elasticity is 12.41GPa, and the hardness of the end surface, the string surface and the radial surface are respectively increased by 34.62%, 49.15% and 53.45%.

The present invention has the following advantages:

1. The present invention has simple process and low cost. Because the raw material of the impregnation treatment liquid selected in the present invention is alkaline silica sol, its advantages are low price, easy to obtain, and high stability, and the storage period is about 1 year. Using silica sol as a raw material greatly reduces the manufacturing cost .

2. The appearance of alkaline silica sol is light blue, odorless, non-toxic, and can be uniformly and stably dispersed in water, so the composite wood after strengthening treatment does not change the original color and texture of wood; it is different from conventional synthetic Compared with resin impregnation, there is no pollution such as free formaldehyde.

3. The particle size of silica particles in silica sol is small and evenly distributed, and the particle size of SiO ₂ is concentrated between 5 and 40 nanometers. Therefore, the silica sol particles can enter the cell wall layer of wood and chemically combine with the cell wall material. The performance of the prepared composite wood is uniform, and the mechanical properties of the cell wall have been significantly improved.

Claims (5)

1. one kind prepares the method for reinforced timber with Ludox, it is characterized in that its step is:

1) choosing of raw materials of silica sol: choosing Ludox pH value is 8～11, and density is 1.15～1.35g/cm ³, dioxide-containing silica is 10%～35%, and the particle diameter of silica concentrates on the alkaline silica sol between 5～40 nanometers;

2) Ludox allotment: Ludox is allocated with hydrochloric acid, Ludox pH value is adjusted to 6.5～7.5, obtain Ludox impregnation process liquid;

3) dipping strengthens: with moisture content is that 8%～30% timber is put into the impregnation process jar, vacuumized for the first time 10～30 minutes to the impregnation process jar, vacuum is-0.080 MPa～-0.095 MPa, inject Ludox impregnation process liquid then, the processing of exerting pressure, to exert pressure be 0.8 MPa～1.5 MPas, kept 30～60 minutes, pressure relief turns back to the Ludox treatment fluid in the pressure immersion can in the solution storage tank then; Carry out the application of vacuum second time again, vacuum is-0.080 MPa～-0.095 MPa, and the processing time is 5～20 minutes; Take out timber at last through impregnation process;

4) health: the timber after the above-mentioned impregnation process is put under the room temperature condition stacks more than 24 hours, interlayer is placed wooden parting bead;

5) classification drying: the timber after the health is put into baking oven, between this timber, place parting bead; Earlier forced convertion drying 3～6 hours under 30 ℃ temperature is warming up to 80 ℃ again, and forced convertion drying 1～6 hour is warming up to 100～105 ℃ then, and forced convertion drying 3～6 hours is taken out at last and strengthened improved wood.

2. according to claim 1ly a kind ofly prepare the method for reinforced timber with Ludox, it is characterized in that: the choosing of described raw materials of silica sol: select commercially available alkaline silica sol for use, the pH value of this Ludox is 8, and density is 1.21g/cm ³, dioxide-containing silica is 25%, the particle diameter of silica dioxide granule concentrates between 8～20nm.

3. according to claim 1ly a kind ofly prepare the method for reinforced timber with Ludox, it is characterized in that: described Ludox allotment: Ludox pH value is 7.22.

4. a kind of method for preparing reinforced timber with Ludox according to claim 1, it is characterized in that: described dipping strengthens to be handled: with moisture content is that 15% artificial forest wood of Cunninghamia lanceolata is put into the impregnation process jar, vacuumized 10 minutes to the impregnation process jar, vacuum is-0.095 MPa.

5. a kind of method for preparing reinforced timber with Ludox according to claim 1, it is characterized in that: described classification drying: with dry 5 hours of the forced convertion under 30 ℃ temperature of the timber after the health, be warming up to 80 ℃ again, dry 4 hours of forced convertion, be warming up to 103 ℃ then, dry 5 hours of forced convertion.