A resin impregnation densification and strengthening process for fast-growing wood

Abstract

A resin impregnation and densification enhancement process for fast-growing wood. Through resin impregnation, the present invention can effectively increase the density of fast-growing wood. Research shows that as the concentration of phenolic resin in the impregnation solution increases, the density of fast-growing poplar wood first rises and then falls. Moreover, when used in combination with an appropriate amount of melamine resin at the optimal concentration of phenolic resin, the enhancement effect can be further improved.

Description

Technical Field

[0001] The present invention relates to the field of fast-growing wood, and particularly to a resin impregnation densification and strengthening process for fast-growing wood. Background Art

[0002] The gradual reduction of global natural forest resources and the increasing emphasis on ecological environment protection in various countries have made the utilization of plantation wood an important way to solve the contradiction between the growing demand for wood and the relative shortage of resources. Artificial fast-growing wood refers to tree species with fast growth, early maturity, and short felling periods. Common fast-growing woods in China include Robinia pseudoacacia cv. Hongsen, Poplar, Eucalyptus, Willow, etc. However, the proportion of juvenile wood in fast-growing wood is relatively high, and its strength is low, which limits the application scenarios of fast-growing wood. In order to expand the application range of fast-growing wood and improve its utilization value, the densification treatment of fast-growing wood has become a major topic in the field of wood research. Summary of the Invention

[0003] Aiming at the problems existing in the prior art, the purpose of the present invention is to provide a resin impregnation densification and strengthening process for fast-growing wood, which has a significant effect on enhancing the density of fast-growing wood.

[0004] A resin impregnation densification and strengthening process for fast-growing wood includes the following steps:

[0005] Put the fast-growing wood into a vacuum treatment tank, evacuate to 0.005 MPa - 0.01 MPa, inject phenolic resin with a concentration of 8 wt% - 21.2 wt% into the vacuum treatment tank, pressurize to 1.2 MPa - 1.5 MPa, impregnate for 120 min - 150 min, and take out the fast-growing poplar; place the poplar on a hot press, preheat at 145 °C - 150 °C for 30 s - 1 min, then carry out hot pressing at 180 °C - 185 °C, the hot pressing pressure is 12 MPa - 15 MPa, the hot pressing speed is 0.6 mm / s - 0.8 mm / s, the compression ratio is 20% - 22%, and keep warm for 30 min - 35 min after hot pressing to obtain densified and strengthened fast-growing wood.

[0006] Preferably, the size of the fast-growing wood is 400 mm * 80 mm * 20 mm.

[0007] Preferably, the wood is fast-growing poplar.

[0008] Preferably, the hot pressing pressure is 15 MPa.

[0009] Preferably, the hot pressing temperature is 185 °C.

[0010] Preferably, the heat preservation time is 35 min.

[0011] Preferably, the concentration of the phenolic resin is 21.2 wt%.

[0012] Preferably, the impregnation time is 120 min.

[0013] Preferably, the preheating time is 1 min.

[0014] Through resin impregnation, the present invention can effectively increase the density of fast-growing wood. Research shows that as the concentration of phenolic resin in the impregnation solution increases, the density of fast-growing poplar wood first increases and then decreases. Moreover, at the optimal concentration of phenolic resin, the use of an appropriate amount of melamine resin can further enhance the strengthening effect. Detailed implementation mode

[0015] The technical effects of the present invention are verified through specific examples below, but the implementation modes of the present invention are not limited thereto.

[0016] The preparation method of the phenolic resin in the present invention is as follows: Take 1 mol of phenol, 1.8 mol of formaldehyde and 50 g of ethanol and place them in a reaction vessel, stir magnetically for 30 min to mix them evenly, add NaOH with a mass fraction of 25% (the total mass of NaOH is 2.5% of the mass of phenol), and react at 95 °C for 3 h to obtain a liquid phenolic resin. When the phenolic resin is used, it needs to be dissolved in anhydrous ethanol.

[0017] The preparation method of the melamine resin in the present invention is as follows: Weigh 80 g of melamine and 45 g of formaldehyde solution and place them in a three-necked flask, add 100 g of water, stir magnetically to mix evenly, then heat up to 68 °C, continue to stir magnetically for 90 min, and continuously adjust the pH of the system to about 8.5 during this period to obtain a hydroxymethyl monomer solution; Weigh 160 g of p-aminobenzenesulfonic acid and dissolve it in 200 g of water, adjust its pH to about 5.5 to obtain a sulfonic acid compound solution, then slowly add the hydroxymethyl monomer solution dropwise to the sulfonic acid compound solution, and continue to stir for 60 min to obtain a prepolymer solution; Weigh 10 g of glycerol triglycidyl ether and add it to the prepolymer solution, and continue to stir for 90 min to obtain a melamine resin. When the melamine resin is used, it needs to be dissolved in water.

[0018] Example 1

[0019] Put fast-growing poplar wood with dimensions of 400 mm * 80 mm * 20 mm into a vacuum treatment tank, evacuate to 0.01 MPa, inject phenolic resin with a concentration of 8 wt% into the vacuum treatment tank, pressurize to 1.2 MPa, impregnate for 150 min and take out the fast-growing poplar wood; Place the poplar wood on a hot press, preheat it at 150 °C for 1 min, then perform hot pressing at 185 °C, the hot pressing pressure is 15 MPa, the hot pressing speed is 0.8 mm / s, the compression ratio is 22%, and keep it warm for 30 min after hot pressing to obtain dense and strengthened fast-growing poplar wood.

[0020] Example 2

[0021] Put fast-growing poplar wood with dimensions of 400mm * 80mm * 20mm into a vacuum treatment tank, evacuate to 0.01MPa, inject phenolic resin with a concentration of 12wt% into the vacuum treatment tank, pressurize to 1.2MPa, impregnate for 150min and then take out the fast-growing poplar wood; place the poplar wood on a hot press, preheat at 150°C for 1min, then perform hot pressing at 185°C, the hot pressing pressure is 15MPa, the hot pressing speed is 0.8mm / s, the compression ratio is 22%, and keep warm for 30min after hot pressing to obtain dense and strengthened fast-growing poplar wood.

[0022] Example 3

[0023] Put fast-growing poplar wood with dimensions of 400mm * 80mm * 20mm into a vacuum treatment tank, evacuate to 0.01MPa, inject phenolic resin with a concentration of 15wt% into the vacuum treatment tank, pressurize to 1.2MPa, impregnate for 150min and then take out the fast-growing poplar wood; place the poplar wood on a hot press, preheat at 150°C for 1min, then perform hot pressing at 185°C, the hot pressing pressure is 15MPa, the hot pressing speed is 0.8mm / s, the compression ratio is 22%, and keep warm for 30min after hot pressing to obtain dense and strengthened fast-growing poplar wood.

[0024] Example 4

[0025] Put fast-growing poplar wood with dimensions of 400mm * 80mm * 20mm into a vacuum treatment tank, evacuate to 0.01MPa, inject phenolic resin with a concentration of 21.2wt% into the vacuum treatment tank, pressurize to 1.2MPa, impregnate for 150min and then take out the fast-growing poplar wood; place the poplar wood on a hot press, preheat at 150°C for 1min, then perform hot pressing at 185°C, the hot pressing pressure is 15MPa, the hot pressing speed is 0.8mm / s, the compression ratio is 22%, and keep warm for 30min after hot pressing to obtain dense and strengthened fast-growing poplar wood.

[0026] Example 5

[0027] Put fast-growing poplar wood with dimensions of 400mm * 80mm * 20mm into a vacuum treatment tank, evacuate to 0.01MPa, inject an equal volume of phenolic resin with a concentration of 21.2wt% and melamine resin with a concentration of 5.1wt% into the vacuum treatment tank, pressurize to 1.2MPa, impregnate for 150min and then take out the fast-growing poplar wood; place the poplar wood on a hot press, preheat at 150°C for 1min, then perform hot pressing at 185°C, the hot pressing pressure is 15MPa, the hot pressing speed is 0.8mm / s, the compression ratio is 22%, and keep warm for 30min after hot pressing to obtain dense and strengthened fast-growing poplar wood.

[0028] Example 6

[0029] Put fast-growing poplar wood with dimensions of 400 mm * 80 mm * 20 mm into a vacuum treatment tank, evacuate to 0.01 MPa, inject an equal volume of phenolic resin with a concentration of 21.2 wt% and melamine resin with a concentration of 15 wt% into the vacuum treatment tank, pressurize to 1.2 MPa, impregnate for 150 min, and then take out the fast-growing poplar wood; place the poplar wood on a hot press, preheat at 150 °C for 1 min, then perform hot pressing at 185 °C, the hot pressing pressure is 15 MPa, the hot pressing speed is 0.8 mm / s, the compression ratio is 22%, and keep warm for 30 min after hot pressing to obtain dense and strengthened fast-growing poplar wood.

[0030] Comparative Example 1

[0031] Put fast-growing poplar wood with dimensions of 400 mm * 80 mm * 20 mm into a vacuum treatment tank, evacuate to 0.01 MPa, inject phenolic resin with a concentration of 40 wt% into the vacuum treatment tank, pressurize to 1.2 MPa, impregnate for 150 min, and then take out the fast-growing poplar wood; place the poplar wood on a hot press, preheat at 150 °C for 1 min, then perform hot pressing at 185 °C, the hot pressing pressure is 15 MPa, the hot pressing speed is 0.8 mm / s, the compression ratio is 22%, and keep warm for 30 min after hot pressing to obtain dense and strengthened fast-growing poplar wood.

[0032] Next, we detected the density of the samples in Examples 1-6 and Comparative Example 1. The specific method is as follows:

[0033] Cut 5 thin slices with a thickness of 3 mm in the middle of each sample, and use fast-growing poplar wood without resin impregnation treatment as the blank group. Detect the density with an X-ray diffractometer, and calculate the density of the sample according to the following formula:

[0034] d = (1 / (u·t)) · ln(I0 / I)

[0035] In the formula: I0 represents the initial intensity of the X-ray; I represents the intensity of the X-ray during testing; t represents the thickness of the sample, and u represents the absorption coefficient (a constant related to the X-ray wavelength and the type of substance. In this experiment, u = 6.935).

[0036] The test results are shown in Table 1:

[0037] Table 1

[0038]

[0039]

[0040] As can be seen from Table 1, through resin impregnation, the density of fast-growing poplar wood can be effectively increased. Among them, as the concentration of phenolic resin in the impregnation solution increases, the density of poplar wood shows a trend of first increasing and then decreasing. Moreover, at the optimal concentration of phenolic resin, when used in combination with an appropriate amount of melamine resin, the strengthening effect can be further improved.

[0041] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A resin impregnation densification and strengthening process for fast-growing wood, characterized in that, The described densification and strengthening process includes the following steps: Put the fast-growing wood into a vacuum treatment tank, evacuate to 0.005 MPa - 0.01 MPa, inject phenolic resin with a concentration of 21.2 wt% into the vacuum treatment tank, pressurize to 1.2 MPa - 1.5 MPa, impregnate for 120 min - 150 min, and then take out the fast-growing wood; Place the fast-growing wood on a hot press, preheat at 145 °C - 150 °C for 30 s - 1 min, and then perform hot pressing at 180 °C - 185 °C. The hot pressing pressure is 12 MPa - 15 MPa, the hot pressing speed is 0.6 mm / s - 0.8 mm / s, the compression ratio is 20% - 22%, and keep warm for 30 min - 35 min after hot pressing to obtain densified and strengthened fast-growing wood. The wood is fast-growing poplar; The preparation method of the phenolic resin is as follows: Take 1 mol of phenol, 1.8 mol of formaldehyde and 50 g of ethanol and place them in a reaction vessel, stir magnetically for 30 min to mix evenly, add NaOH with a mass fraction of 25%, where the total mass of NaOH is 2.5% of the mass of phenol, and react at 95 °C for 3 h to obtain liquid phenolic resin.

2. A compaction enhancement process as described in claim 1, characterized in that, The size of the fast-growing wood is 400 mm * 80 mm * 20 mm.

3. A densification and strengthening process as described in claim 1, characterized in that, The hot pressing pressure is 15 MPa.

4. A densification enhancement process as described in claim 1, characterized in that, The hot pressing temperature is 185 °C.

5. A densification enhancement process as described in claim 1, characterized in that, The heat preservation time is 35 min.

6. A compaction enhancement process as described in claim 1, characterized in that, The impregnation time is 120 min.

7. A compaction enhancement process as described in claim 1, characterized in that, The preheating time is 1 min.

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