Method for densifying wood/bamboo by combining hot pressing with steam injection and densified wood/bamboo

Abstract

The invention discloses a method for densifying wood/bamboo by combining hot pressing with steam injection. The method comprises the following steps: additionally mounting high-pressure-resistant high-temperature-resistant air permeable plates on upper and lower press plates of a hot press machine provided with steam injection holes, wherein the smooth surfaces of the air permeable plates faces out and get in contact with to-be-pressed wood/bamboo; heating the upper and lower press plates to 160-220 DEG C, and keeping the temperature of the upper and lower press plates in the follow-up steps; putting the wood/bamboo of which the water content is 8-30% on the lower press plate of the hot press machine; quickly closing the upper and lower press plates; stopping the closing process when the upper press plate gets in contact with the to-be-pressed wood/bamboo and applying certain pressure to the to-be-pressed wood/bamboo, and enabling the injection of high-pressure steam; slowly closing the above upper and lower press plates, and continuing the steam injection at the same time; stopping the closing process when the to-be-pressed wood/bamboo is pressed to reach the thickness as required, remaining in place, and continuing the steam injection at the same time; and stopping the steam injection and enabling the air sucking function of small holes in the upper and lower press plates, so that extra water and extract gas can be discharged.

Description

technical field [0001] The invention relates to the field of material preparation, in particular to a method for densifying wood / bamboo by hot pressing combined with a steam spraying method and densifying wood / bamboo. Background technique [0002] In the wood product industry, high-strength wood raw materials have always been pursued by people, but high-strength wood raw materials are always limited in natural resources and expensive. Therefore, wood scientists try to increase the density of wood through the process of wood densification, and turn low-density, resource-rich and cheap low-density wood into high-density, high-strength wood. There are many reports of wood densification in historical literature (Fang et al. 2011, 2012a, 2012b, 2012c; Boonstra and Blomberg 2007; Fukuta et al. ; Inoue et al.1993b; Inoue et al.2008; Ito et al.1998b; Kamke 2006; Kollmann 1936; Kollmann et al.1975; Navi and Heger2004; Seborg et al.1945). There are also many patents on wood densifica...

AI Technical Summary

Problems solved by technology

[0003] 1) The natural characteristics of wood cannot be guaranteed;

[0004] 2) Affect the recycling or natural degradation of wood, causing pollution to the environment;

[0005] 3) Higher cost

[0007] 1) The process is complicated and takes a long time;

[0008] 2) At present, the methods in several laboratories mainly engaged in wood densification in the world are mostly limited to small-sized test materials;

[0009] 3) Dimensional springback caused by mechanical densification of wood;

[0010] 4) Some use high-temperature treatment (190-230 degrees Celsius) and long enough time to reduce dimensional rebound. High-temperature and long-term treatment will damage the mechanical properties of wood, especially the surface of wood, often causing partial carbonization, or causing deep color and Colors vary widely, often making compressed wood unusable at all

[0011] 5) The use of high-temperature steam can alleviate some of the problems mentioned in 4) above, but because the wood is under the high pressure of the hot-pressed iron plate, it is difficult for the steam to act evenly (or even impossible) on the pressure surface of the pressed wood, especially when the wood is pressed When the pressure surface is large

[0012] 6) Some hot presses have steam injection holes on the hot iron plate (my previous experiment) which can alleviate some of the problems mentioned in 5) above, but the steam still cannot be evenly distributed to the surface of the pressed wood, and the wood is in the Under high pressure, it will protrude into the spray hole, causing many bumps on the surface of the compressed wood

Bamboo has high mechanical strength, and its elastic modulus per unit density is comparable to that of steel. However, the density and mechanical strength of bamboo in the transverse direction (from bamboo green to bamboo yellow) and vertical direction (from the base of the standing bamboo to the tip) The difference is very large, which leads to the high degree of non-uniformity of density and mechanical strength inside the composite engineering board made of raw bamboo, which cannot be compared with steel, which greatly restricts the utilization of raw bamboo

In addition, due to the arc shape of the bamboo wall, a large amount of bamboo raw materials are wasted in order to obtain regular bamboo strips during the processing of bamboo chips.

Although ordinary recombined bamboo can obtain high-density and relatively uniform boards, this type of product requires a large amount of sizing, which is extremely environmentally friendly

Images