CN105666612A - Flame-retardant thermal modification wood and preparation method thereof - Google Patents

Abstract

The invention relates to flame-retardant thermal modification wood and a preparation method thereof. The preparation method comprises the step that after being subjected to immersion treatment, the wood is subjected to heat treatment. According to the flame-retardant thermal modification wood and the preparation method thereof, the flame-retardant thermal modification wood is prepared by combining the wood high-temperature heat treatment with the wood flame-retardant technology; the dual characteristics that the wood is subjected to high-temperature heat treatment and flame retarding are achieved at the same time; the flame-retardant thermal modification wood has the good surface decorative performance, dimensional stability and the like, and the excellent flame-retardant property is also achieved; the combustion heat release rate and smoke production are substantially decreased, and the fireproof safety of processed wood products is greatly increased.

Description

A kind of flame-retardant thermally modified wood and its preparation method

technical field

The invention relates to heat-treated wood and a preparation method thereof, in particular to flame-retardant heat-treated wood and its preparation, and belongs to the technical field of wood heat modification treatment.

Background technique

Existing studies have shown that high-temperature heat treatment of wood is generally carried out under protective gases such as vacuum or water vapor, nitrogen, etc., and the temperature is raised to between 160-260 °C, and the physical and chemical reactions of wood are caused by heat to improve its performance. The holding time is usually 2-10 hours, and some processing times even reach more than 10 hours. High-temperature heat treatment can endow wood with excellent dimensional stability, biological durability, corrosion resistance, safety, and environmental protection. Heat-treated materials are widely used in furniture, indoor and outdoor architectural decoration and structures, wooden escalators, park facilities, and internal facilities of steam rooms, etc. Due to the high temperature and long treatment time of wood heat treatment, the degree of degradation of hemicellulose is large, and the acid products further destroy the structure of cellulose, so that the degree of polymerization of cellulose decreases, and finally the physical strength of the treated wood is reduced by about 10%-30%. The hardness and wear resistance are reduced; in addition, due to the flammability of wood, the high-temperature heat treatment process cannot solve its flammability, and there is a fire safety hazard in the direct application of high-temperature heat-treated materials. GB50016 "Code for Fire Protection in Architectural Design" and GB20286 "Requirements and Labeling of Flame Retardant Products and Components in Public Places" have been promulgated and implemented, which clearly stipulate that architectural design and products in public places must use environmentally friendly and safe flame retardant materials. Therefore, heat-treated wood needs further flame-retardant treatment to ensure the safety of its products.

my country's high-temperature heat treatment technology for wood mainly focuses on improving the dimensional stability and corrosion resistance of wood. For example, the Chinese patent application with the publication number CN101623887A discloses "a wood treatment method and wood prepared by the method". The method comprises sequentially performing decompression treatment, preheating treatment, high temperature pressurization treatment and humidity adjustment treatment on the wood placed in the container. During the wood treatment process, a high equilibrium moisture content is maintained, and the prepared wood overcomes drying defects such as cracking and shrinkage. The proportion of cracking, hygroscopicity, and water absorption performance of the treated wood are greatly reduced, and the weather resistance and corrosion resistance are improved. Carbonized wood"SB/T10508-2008 standard. The treatment method uses water vapor as a medium, and has the characteristics of short treatment time and small heat loss. The method of the invention saves energy and has low wood treatment cost.

The Chinese patent application whose publication number is CN104400866A discloses a "production and processing method of paulownia wood homogeneous carbonized wood", which specifically consists of sawing, degreasing, drying, dampening, stacking, entering the kiln, heating, carbonization, cooling, A total of eleven processes are completed after leaving the kiln. The degreasing treatment lays a solid foundation for homogeneous carbonization. When entering the kiln, the wood is covered with kaolin to completely isolate the air. To achieve a uniform carbonization effect. The degree of carbonization of Paulownia is uniform, and the color, hygroscopicity and various mechanical properties show the same good characteristics, which improves the application value and economic benefits of the product.

my country's wood flame retardant technology mainly focuses on improving the performance of wood flame retardants. For example, the Chinese patent application with the publication number CN104210002A discloses "a composite flame retardant, its preparation method and its use", which discloses a composite Flame retardants, including polysilicate aluminum dihydrogen phosphate solution and nitrogen phosphorus flame retardant solution, respectively prepare polysilicate aluminum dihydrogen phosphate solution and nitrogen phosphorus flame retardant solution, and then mix the two to obtain the compound Flame retardants have obvious flame retardant and smoke suppression effects. The Chinese patent application with the publication number CN103722600A discloses "a wood modifier and its preparation method". The wood modifier includes the following components in parts by weight: 20-200 parts of phosphoric acid; 20-100 parts of urea; 1.0 parts; 5-20 parts of tetrakis hydroxymethyl phosphorus sulfate; 2-15 parts of aluminum tripolyphosphate; 0.1-2.5 parts of dioctyl sulfosuccinate sodium salt; 40-200 parts of water. The wood modifier not only has remarkable flame retardant effect, but also has good dimensional stability function. When the weight gain rate of treated wood is about 20%, the oxygen index can reach more than 50%, and the dimensional stability ASE can reach more than 35%. The wood flame retardant provided by the invention has a simple preparation method and low cost, and is suitable for popularization and use. There are very few studies on high-temperature heat treatment and flame-retardant treatment. For example, the Chinese patent application with the publication number CN204357064U discloses "a carbonized flame-retardant solid wood composite floor", and proposes a carbonized flame-retardant solid wood composite floor. , a flame retardant carbonized surface layer, a first flame retardant reinforced layer, a carbonized core layer, a second flame retardant reinforced layer, a carbonized bottom layer and a back primer layer are superimposed in sequence. The carbonized surface layer improves the aesthetics of the floor, the sequentially superimposed carbonized material structure improves the dimensional stability of the floor, and the addition of the flame-retardant reinforced structure layer makes up for the strength loss caused by the carbonization treatment.

At present, no related patents have been found on the process method combining flame retardancy and high temperature heat treatment and the wood prepared by this method.

Contents of the invention

The object of the present invention is to provide a kind of flame-retardant heat-modified wood and its preparation method in view of the technical problems existing in the above existing high-temperature heat-treated wood, fire-resistant wood and its preparation process. In the present invention, the fire retardant is first used to impregnate the wood, and then the high-temperature heat treatment is carried out, so as to obtain the high-temperature heat-treated wood with good flame-retardant performance. The flame-retardant effect is strong; the dimensional stability of the wood is high, and the decrease in the surface hardness is small; and the surface color of the flame-retardant heat-modified wood tends to be brown, and has good color decoration performance.

In order to achieve the object of the present invention, one aspect of the present invention provides a method for preparing flame-retardant thermally modified wood, which includes heat-treating the impregnated wood.

Wherein, the heat treatment temperature is 130-160°C, preferably 140-150°C; the heat treatment time is 20-50min, preferably 20-40min, more preferably 30min.

In particular, the impregnation treatment includes soaking the wood sequentially under reduced pressure and normal pressure.

Wherein, the immersion under reduced pressure is vacuum immersion treatment; the immersion under normal pressure is normal pressure immersion treatment.

In particular, the vacuum degree during the vacuum impregnation treatment is <0MPa, preferably -0.01～-0.1MPa, more preferably -0.05～-0.1MPa; the vacuum impregnation treatment time is 15-45min, preferably 20-40min, further It is preferably 30 minutes; the relative pressure during the atmospheric pressure impregnation treatment is 0 MPa; the time of the atmospheric pressure impregnation treatment is 15-45 minutes, preferably 20-40 minutes, more preferably 30 minutes.

Wherein, the impregnation treatment is firstly soaking the wood in the flame retardant solution, and then soaking under reduced pressure and normal pressure successively.

In particular, the flame retardant in the flame retardant solution is a nitrogen-phosphorus flame retardant or a modified nitrogen-phosphorus flame retardant, preferably a modified nitrogen-phosphorus flame retardant, more preferably polysilicate aluminum dihydrogen phosphate Modified nitrogen and phosphorus flame retardant.

In particular, the mass percent concentration of the flame retardant solution is 5-15%, preferably 10%.

Another aspect of the present invention provides a method for preparing flame-retardant thermally modified wood, comprising the following steps:

1) Soak the wood in a flame retardant solution, and perform vacuum impregnation treatment under reduced pressure to obtain vacuum impregnated wood;

2) continue to soak the vacuum-impregnated wood in the flame retardant solution, and perform normal-pressure impregnation treatment under normal pressure to obtain normal-pressure impregnated wood;

3) Drying the atmospheric pressure impregnated wood to obtain flame retardant impregnated wood;

4) Heat treatment of flame retardant impregnated wood.

Wherein, the flame retardant solution described in step 1) is nitrogen phosphorus flame retardant solution or modified nitrogen phosphorus flame retardant solution, preferably modified nitrogen phosphorus flame retardant solution, more preferably polysilicate aluminum dihydrogen phosphate Modified nitrogen and phosphorus flame retardant solution.

In particular, the nitrogen-phosphorus flame retardant is a BL environment-friendly flame retardant; the modified nitrogen-phosphorus flame retardant is a modified BL environment-friendly flame retardant, that is, the BL environment-friendly flame retardant is modified by polysilicate aluminum dihydrogen phosphate.

In particular, the BL environment-friendly flame retardant is a nitrogen-phosphorus flame retardant developed by Beijing Forestry University.

Wherein, the mass percent concentration of the flame retardant solution is 5-15%, preferably 10%.

In particular, the nitrogen-phosphorus flame retardant or modified nitrogen-phosphorus flame retardant is mixed with water, stirred, and dissolved uniformly to obtain the flame retardant solution, wherein the preparation percentage concentration of the flame retardant solution is 5- 15%, preferably 10%.

Wherein, the nitrogen-phosphorus flame retardant is prepared according to the following steps:

A) Prepare raw materials according to the following proportions by weight:

Phosphoric acid (85% concentration) 7-11

Urea 3.5-4.5

Catalyst 0.025-0.035

Among them, the catalyst includes the following raw materials in parts by weight: tin chloride 0.8-1.2, copper sulfate 1.5-2.5, sodium chloride 0.8-1.2, ferric chloride 0.8-1.2, aluminum sulfate 0.8-1.2, boric acid 0.8-1.2, Zinc chloride 1.5-2.5, grind it evenly and mix;

B) Add phosphoric acid in the reaction kettle, stir and heat while stirring, so that the temperature rises to 50-60°C;

C) adding urea, stirring the mixture of phosphoric acid and urea, so that the material is distributed and heated evenly;

D) When the temperature rises to 90-120°C, add a catalyst to the reactor and continue heating;

E) After raising the temperature to 130-150°C, when the volume of the reactant increases to 2-2.5 times of the original volume, stop heating;

F) Pour out the product in the reaction kettle, wait for it to cool and solidify, and obtain.

In particular, the stirring speed is controlled at 50-70 rpm.

Wherein, the modified nitrogen-phosphorus flame retardant is prepared according to the following steps:

1) Preparation of polysilicate aluminum dihydrogen phosphate solution

1A) adding aluminum dihydrogen phosphate into water, stirring, and dissolving evenly to prepare an aluminum dihydrogen phosphate solution, wherein the mass percentage concentration of the aluminum dihydrogen phosphate solution is 15-25%;

1B) adding the silicate into water, stirring, and dissolving evenly to prepare a silicate solution, wherein the mass percent concentration of the silicate solution is 1-5%;

1C) Slowly pour the silicate solution into the aluminum dihydrogen phosphate solution, stir and let it stand to obtain a polysilicate aluminum dihydrogen phosphate solution, wherein the mass ratio of the silicate solution to the aluminum dihydrogen phosphate solution is 100: 40-117.

2) Preparation of nitrogen and phosphorus flame retardant

2A) Prepare raw materials according to the following proportions by weight:

Phosphoric acid (85% concentration) 7-11

Urea 3.5-4.5

Catalyst 0.025-0.035

Among them, the catalyst includes the following raw materials in parts by weight: tin chloride 0.8-1.2, copper sulfate 1.5-2.5, sodium chloride 0.8-1.2, ferric chloride 0.8-1.2, aluminum sulfate 0.8-1.2, boric acid 0.8-1.2, Zinc chloride 1.5-2.5, grind it evenly and mix;

2B) Add phosphoric acid into the reaction kettle, stir and heat while stirring, so that the temperature rises to 50-60°C;

2C) adding urea, stirring the mixture of phosphoric acid and urea, so that the material is distributed and heated evenly;

2D) When the temperature rises to 90-120°C, add a catalyst to the reaction kettle and continue heating;

2E) After raising the temperature to 130-150°C, when the volume of the reactant increases to 2-2.5 times of the original volume, stop heating;

2F) Pour out the product in the reactor, and wait for it to cool and solidify to obtain the nitrogen-phosphorus flame retardant.

3) Preparation of modified nitrogen and phosphorus flame retardants

3A) adding the nitrogen-phosphorus flame retardant into water, mixing it evenly with water, and preparing a nitrogen-phosphorus flame retardant solution, wherein the mass percentage concentration of the nitrogen-phosphorus flame retardant solution is 25-35%;

3B) Slowly pour the polysilicate aluminum dihydrogen phosphate solution into the nitrogen and phosphorus flame retardant solution, stir and let it stand to obtain a modified nitrogen and phosphorus flame retardant, wherein the weight of the polysilicate aluminum dihydrogen phosphate solution is equal to the nitrogen and phosphorus flame retardant solution. The weight ratio of the flame retardant solution is 20-50:100.

Especially, the mass percent concentration of aluminum dihydrogen phosphate solution described in step 1A) is preferably 20%; The mass percent concentration of silicate solution described in step 1B) is preferably 3%; Described silicate selects silicic acid Sodium, potassium silicate or lithium silicate; The ratio of the mass of silicate solution and aluminum dihydrogen phosphate solution described in step 1C) is preferably 100:50; The quality of nitrogen phosphorus flame retardant solution described in step 3A) The percentage concentration is preferably 30%; the weight ratio of the polysilicate aluminum dihydrogen phosphate solution to the nitrogen phosphorus flame retardant solution in step 3B) is preferably 25:100.

Wherein, step 1) in the vacuum impregnation process described in the vacuum <0MPa, preferably -0.01 ~ -0.1MPa, more preferably -0.05 ~ -0.1MPa; vacuum impregnation treatment time is 15-45min, preferably 20- 40min, more preferably 30min.

In particular, the vacuum degree during the vacuum impregnation treatment is preferably -0.05 MPa; the vacuum impregnation treatment time is 15-45 minutes, preferably 20-40 minutes, more preferably 30 minutes.

Wherein, the relative pressure during the atmospheric pressure impregnation treatment described in step 2) is 0 MPa; the time of the atmospheric pressure impregnation treatment is 15-45min, preferably 20-40min, more preferably 30min.

In particular, the flame retardant in step 2) is selected from nitrogen-phosphorus flame retardants or modified nitrogen-phosphorus flame retardants, preferably modified nitrogen-phosphorus flame retardants, more preferably polysilicate aluminum dihydrogen phosphate modified nitrogen Phosphorus flame retardant.

Wherein, the drying treatment temperature in step 3) is 100-103°C, preferably 103°C; the drying time is ≥6h; the moisture content of the flame-retardant impregnated wood is ≤15%, preferably 7-15%, more preferably 10%.

In particular, step 3A) is also included: place the impregnated wood at room temperature for 5-10 days (days), and then carry out the drying treatment; preferably place it for 7 days before carrying out the drying treatment.

Wherein, the temperature of wood heat treatment in step 4) is 130-160°C, preferably 140-150°C; the heat treatment time is 20-50min, preferably 20-40min, more preferably 30min.

In particular, the heat treatment of wood in step 4) is to raise the temperature of wood to 130-160°C at a heating rate of 5-20°C/min, and keep it at 130-160°C for 20-50min, preferably 20-40min, more preferably 30min.

In particular, the wood heat treatment is to raise the temperature of the wood to 130-160°C at a heating rate of 10-15°C/min, and keep it at 130-160°C for 20-50min, preferably 20-40min , more preferably 30min.

In particular, the wood heat treatment is to raise the temperature of the wood to 140-150°C at a heating rate of 10-15°C/min, and keep the temperature at 140-150°C for 20-40min, preferably 30min.

In particular, it also includes performing humidity conditioning treatment on the heat-treated wood so that the moisture content of the heat-treated wood reaches 8-12%, preferably 10%.

In particular, the heat-treated wood is placed in a constant temperature and humidity chamber, so that the moisture content of the heat-treated wood reaches 8-12%, preferably 10%.

Another aspect of the present invention provides a modified wood prepared according to the above treatment method.

Compared with the existing thermally modified wood and its preparation method, the present invention has the following advantages:

1. The method of the present invention adopts flame-retardant impregnation treatment on wood, low-temperature drying of flame-retardant treated materials, and high-temperature heat treatment of flame-retardant treated materials to prepare flame-retardant thermally modified wood, which has dual characteristics of high-temperature heat treatment and flame-retardant wood: both Good surface decoration, dimensional stability, etc., and excellent flame retardant properties, the rate of combustion heat release and smoke production are greatly reduced, greatly increasing the fire safety of treated materials;

2. The present invention carries out flame retardant impregnation treatment on wood under vacuum negative pressure state, the drug loading of flame retardant in wood is higher than 30kg/m ³ , and the flame retardant performance is good; the hygroscopic expansion rate is low, and the radial hygroscopic expansion rate is low less than 1.5%; the hygroscopic expansion rate in the chord direction is less than 1.5%; the hygroscopic expansion rate in the volume is lower than 3.1%; the anti-swelling coefficient is high, and the radial anti-swelling coefficient is greater than 21.8%; High dimensional stability.

3. The preparation method of the flame-retardant thermally modified wood of the present invention is simple, and has obvious advantages in reducing production costs and energy saving and environmental protection compared with traditional heat treatment processes: nitrogen-phosphorus flame retardants are used as catalysts, which can be used at lower temperatures , Promote dehydration and carbonization of wood in a short time, reduce processing energy consumption, and shorten production time. The target temperature of heat treatment is reduced from 160°C-260°C to 140-150°C, and the holding time is shortened from 2-10h to about 30min.

4. The method for preparing flame-retardant thermally modified wood of the present invention utilizes the principle of flame retardant to promote cellulose pyrolysis and carbonization at high temperature (≥130°C), and catalyzes wood dehydration in the high-temperature heat treatment process to accelerate the high-temperature carbonization process of wood and reduce The target temperature of wood carbonization shortens the holding time of high-temperature heat treatment to achieve the purpose of reducing energy consumption; the introduction of flame retardants in the method of the present invention not only endows the wood with good flame-retardant properties after flame-retardant thermal modification, but also makes the wood have good dimensional stability Sex, beautiful chroma, has excellent color decoration performance.

5. The lightness L* of the flame-retardant thermally modified wood of the present invention decreases, the chromaticity index a* of the red-green axis and the chromaticity index b* of the yellow-blue axis increase, the surface color tends to be brown, the color can be adjusted, and the decorative performance is improved .

6. When the flame-retardant heat-modified wood of the present invention is burned, the peak value of the low-temperature heat release rate is 48.45% lower than that of ordinary high-temperature heat-treated materials, and the initial combustion degree is greatly reduced, which can effectively slow down the spread of fire; The total heat release rate is reduced by 36.6%, and the overall combustion degree is significantly reduced; the flame retardant is redistributed during the heat treatment process, the degree of agglomeration and crystallization of the flame retardant is reduced, and the distribution of the flame retardant is more uniform; and the chemical combination between the flame retardant and wood occurs , the anti-loss effect is enhanced, which is conducive to the preservation of the flame retardant in wood, and the flame retardant effect is long-lasting, and the unreacted low-molecular compounds with strong hygroscopicity contained in the nitrogen-phosphorus flame retardant, such as urea, etc. Decompose and improve the shortcomings of the hygroscopicity of nitrogen and phosphorus flame retardant treated materials.

Description of drawings

Fig. 1 is the heat release rate HRR curve figure of the heat-treated wood and raw material test piece prepared by the embodiment of the present invention 2-4, comparative example 1-4;

Fig. 2 is the TSR curve diagram of the total smoke release amount of the heat-treated wood and raw material test pieces prepared by Examples 2-4 of the present invention and Comparative Examples 1-4;

Fig. 3 is the scanning electron microscope picture of the flame-retardant thermally modified wood prepared in Example 2 of the present invention;

Fig. 4 is a scanning electron micrograph of thermally modified wood prepared in Comparative Example 4 of the present invention.

detailed description

Although the present invention has been described in detail above, the present invention is not limited thereto, and those skilled in the art can make modifications according to the principle of the present invention, therefore, all various modifications carried out according to the principle of the present invention should be understood as falling within the scope of the present invention. protection scope of the present invention.

The wood treated by the present invention can be natural forest wood or plantation fast-growing wood. In the embodiment of the present invention, fast-growing poplar (Poplus.app) is taken as an example to describe the preparation process of the modified wood of the present invention. The fast-growing poplar is collected in Qilai Forest Farm, Sichuan, with an average air-dry density of 355kg/m ³ , a moisture content of 7%, and a density of 0.4g/cm ³ ; Radial) wood blocks shall be sawed according to the national standard GB1928-2009.

Except for fast-growing poplar, other woods in the embodiments of the present invention are suitable for the present invention such as eucalyptus, Chinese fir, pine and the like.

Aluminum dihydrogen phosphate (chemically pure), phosphoric acid (concentration 85%, chemically pure), urea (content 99%, chemically pure), tin chloride (chemically pure), copper sulfate (chemically pure), sodium chloride (chemically pure ), ferric chloride (chemically pure), aluminum sulfate (chemically pure), boric acid (chemically pure), zinc chloride (chemically pure), sodium silicate (chemically pure), all purchased from Beijing Chemical Reagent Company.

Embodiment 1 prepares modified nitrogen phosphorus flame retardant

1. Preparation of polysilicate aluminum dihydrogen phosphate solution

1A) Add aluminum dihydrogen phosphate powder into water, stir, dissolve evenly, and make aluminum dihydrogen phosphate solution, wherein, the mass percentage concentration of aluminum dihydrogen phosphate solution is 20%, that is, every 100g of aluminum dihydrogen phosphate is dissolved in 400g of aluminum dihydrogen phosphate in water;

1B) adding sodium silicate into water, stirring, and dissolving evenly to prepare a silicate solution, wherein the mass percentage concentration of the sodium silicate solution is 3%, that is, every 3g of sodium silicate is dissolved in 97g of water;

In the present invention, the concentration of the aluminum dihydrogen phosphate solution is except 20%, and the aluminum dihydrogen phosphate solution with a concentration of 15-25% is applicable to the present invention; the concentration of the silicate solution is except 3%, and the concentration is 1-5% silicate solution is applicable to the present invention; in the process of preparing the silicate solution, besides sodium silicate, potassium silicate and lithium silicate can also be selected.

1C) Slowly pour the silicate solution with a mass percentage concentration of 3% into the aluminum dihydrogen phosphate solution with a mass percentage concentration of 20%, stir and let it stand to obtain a polysilicate aluminum dihydrogen phosphate solution, wherein the silicate The mass ratio of the solution to the aluminum dihydrogen phosphate solution is 100:50.

In the embodiment of the present invention, the mass ratio of silicate solution to aluminum dihydrogen phosphate solution is 100:50 as an example for illustration. During the preparation of polysilicate aluminum dihydrogen phosphate solution, the silicate solution and aluminum dihydrogen phosphate Except for the mass ratio of the solution of 100:50, the mass ratio of the sodium silicate solution to the aluminum dihydrogen phosphate solution of 100:40-117 is applicable to the present invention.

2. Preparation of nitrogen and phosphorus flame retardants

2A) Prepare raw materials according to the following weight ratio:

Phosphoric acid (concentration is 85%) 750g

Urea (content 99%) 400g

Catalyst 3g

Among them, the catalyst is a light yellow-green powder prepared by the Environmental Protection Flame Retardant Technology Center of the School of Materials Science and Technology, Beijing Forestry University. The weight ratio of raw materials is: tin chloride 1.2, copper sulfate 1.5, sodium chloride 0.8, iron chloride 1.2 , aluminum sulfate 1.2, boric acid 1.2, zinc chloride 2.5, grind them evenly and mix them;

The nitrogen-phosphorus flame retardant prepared in the present invention is prepared according to the invention patent (invention name: a flame retardant and its preparation method; patent number: 200710122243.2). The flame retardants prepared by the invention patent (patent number: 200710122243.2) are applicable to the present invention.

2B) Add the raw material phosphoric acid into the reactor (the reactor is equipped with a stirrer, a thermometer, a pressure gauge and a condenser) under stirring, and heat while stirring until the temperature of the material phosphoric acid in the reactor rises to 60°C Add urea, continue heating while stirring, so that the temperature of the mixed material rises to 110°C, add the catalyst, continue heating while stirring, and react the mixture until the temperature of the reaction mixture reaches 130°C, observe the reaction phenomenon while heating, As the temperature rises, the light green liquid gradually turns into a milky white viscous substance, the foam increases sharply, the temperature rises faster, the volume of the material expands rapidly, and a large amount of gas is discharged from the condenser tube, mainly ammonia and water vapor, absorbed by water When the volume of the reactants in the reactor increases to twice the original volume, stop heating and continue to stir. The materials in the reactor react violently by their own heat release, and the temperature continues to rise. When the reaction becomes stable, the temperature will no longer rise. , when the temperature begins to drop, it indicates that the reaction is complete, wherein the control stirring speed is 70 revolutions/minute;

2C) Pour out the milky white viscous matter in the reaction kettle, place it in a fume hood, cool and solidify after 30-60 minutes, and then pulverize it with a pulverizer to obtain powdery nitrogen-phosphorus flame retardant powder.

3. Preparation of modified nitrogen and phosphorus flame retardants

3A) Add the nitrogen-phosphorus flame retardant powder into water, mix it evenly with water, and prepare a nitrogen-phosphorus flame retardant solution, wherein the mass percentage concentration of the nitrogen-phosphorus flame retardant solution is 30%, that is, every 300g of nitrogen-phosphorus flame retardant The powder is dissolved in 700g of water, and the nitrogen-phosphorus flame retardant solution with a mass percentage concentration of 30% is prepared;

In the embodiment of the present invention, except that the concentration of the nitrogen-phosphorus flame retardant solution is 30%, the nitrogen-phosphorus flame retardant solution with a concentration of 25-35% is suitable for the present invention.

3B) Slowly pour the polysilicate aluminum dihydrogen phosphate solution prepared in step 1 into the nitrogen-phosphorus flame retardant solution with a concentration of 30% by mass, stir and let it stand to obtain a modified nitrogen-phosphorus flame retardant, wherein the polysilicon The ratio of the weight of the acid aluminum dihydrogen phosphate solution to the weight of the nitrogen and phosphorus flame retardant solution is 25:100.

The ratio of the weight of the polysilicate aluminum dihydrogen phosphate solution to the weight of the nitrogen and phosphorus flame retardant solution in the process of preparing the modified nitrogen-phosphorus flame retardant in the embodiment of the present invention is 25:100, and the other weight is 20-50:100 All ratios are applicable to the present invention.

Embodiment 2 prepares flame-retardant thermally modified wood

1. Preparation of modified flame retardant solution

Dissolve the modified nitrogen-phosphorus flame retardant prepared in Example 1 in water, stir and dissolve evenly to obtain a modified flame retardant solution, the mass percentage concentration of the modified flame retardant solution is 10%, that is, every 10g of modified nitrogen-phosphorus Flame retardant solution in 90g of water, ready.

In the embodiment of the present invention, the mass percent concentration of the flame retardant solution is 10% for illustration. Other flame retardant solutions with a mass percent concentration of 5-15% are applicable to the present invention.

In addition to the modified nitrogen-phosphorus flame retardant, the flame retardant used for the dipping treatment in the present invention is also suitable for the present invention. The nitrogen-phosphorus flame retardant powder prepared in step 2 of Example 1 is dissolved in water to prepare a nitrogen-phosphorus flame retardant solution with a mass percentage concentration of 5-15%, which is used for impregnating wood.

2. Dipping treatment

2-1) Vacuum impregnation treatment

Pour the flame retardant solution into the impregnation tank equipped with fast-growing poplar, soak the wood completely, and connect the vacuum pump; turn on the vacuum pump for vacuum treatment, so that the vacuum degree in the tank is reduced and maintained at -0.05MPa. Carry out vacuum impregnation treatment to wood under pressure state, make vacuum impregnation wood, wherein, the volume ratio of wood and flame retardant solution is 1:3, and treatment time is 30min;

2-2) Atmospheric pressure impregnation treatment

Turn off the vacuum pump, open the vacuum pressurized tank, so that the pressure in the tank returns to normal pressure (1 standard atmospheric pressure, that is, 0.1MPa), continue to soak the wood in the flame retardant solution, and perform normal pressure impregnation treatment to obtain normal pressure impregnated wood. , wherein the atmospheric pressure immersion treatment time is 30min.

3. Drying treatment

Place the impregnated wood under normal pressure at room temperature (15-30°C) for 7 days, then place it in a drying oven, and dry it at 103°C for more than 6 hours to obtain a fire-retardant impregnated wood, wherein the water content of the fire-retardant impregnated wood is 10% (moisture content≤15% are applicable to the present invention).

In the embodiment of the present invention, 7 days of storage at room temperature is taken as an example for illustration, and wood storage of 5-10 days is applicable to the present invention.

4. Thermal modification treatment

4-1) Put the flame-retardant impregnated wood in a high-temperature heat treatment test box (Shanghai Yiheng Technology Co., Ltd., PXR-9), heat up, and raise the temperature to 150°C at a heating rate of 15°C/min. Keep at 150°C for 30 minutes, and carry out high-temperature thermal modification treatment;

Among them: water vapor is used as the protective gas (water is placed in the test chamber, and as the temperature in the chamber rises, the water volatilizes to generate water vapor, which plays the role of protecting the protective gas. In addition to placing water in the test chamber to generate water vapor, Water vapor, nitrogen and other protective gases can also be passed into the box).

4-2) After heat preservation treatment for 30 minutes, stop heating, and take it out after the wood temperature drops to room temperature (15-30°C);

4-3) The wood is placed in a constant temperature and humidity test box, and the humidity is adjusted to adjust the moisture content of the wood to 10%, so as to obtain a flame-retardant heat-modified wood.

The prepared thermally modified wood was scanned by electron microscope to observe the distribution of flame retardant inside the wood, as shown in Figure 3 of electron microscope scan.

It can be seen from Figure 3 that the flame retardant distribution inside the wood: after thermal modification, the flame retardant adheres to the wood cell wall in the form of a thin layer, which is almost in surface contact with the inside of the wood, with a large coverage area, and no obvious exposed area of the wood cell wall. The fuel has no obvious particle crystallization. It has been illustrated that the flame retardant impregnated wood of the present invention can change the existence mode of the flame retardant in the wood through thermal modification treatment: the flame retardant is changed from particle crystal suspension or agglomerated filling into a layered combination form, greatly increasing the flame retardant and The binding force between wood cell walls promotes the formation of chemical bonds between the two. Thus, the binding force between the flame retardant and wood and the anti-loss performance are increased. At the same time, the uniform distribution of the flame retardant in the wood cell wall can fully exert the flame retardant effect during combustion, and improve the flame retardant effect of the treated wood.

Example 3 Preparation of flame retardant thermally modified wood

1. Preparation of modified flame retardant solution

Dissolve the modified nitrogen-phosphorus flame retardant prepared in Example 1 in water, stir and dissolve evenly to obtain a modified flame retardant solution, the mass percentage concentration of the modified flame retardant solution is 5%, that is, every 5g of modified nitrogen-phosphorus Fire retardant solution in 95g of water, to get.

2. Dipping treatment

2-1) Vacuum impregnation treatment

Pour the flame retardant solution into the impregnation tank equipped with fast-growing poplar, soak the wood completely, and connect the vacuum pump; turn on the vacuum pump for vacuum treatment, so that the vacuum degree in the tank is reduced and maintained at -0.09MPa. Carry out vacuum impregnation treatment to wood under pressure state, make vacuum impregnation wood, wherein, the volume ratio of wood and flame retardant solution is 1:3, and treatment time is 20min;

2-2) Atmospheric pressure impregnation treatment

Turn off the vacuum pump, open the vacuum pressurized tank, so that the pressure in the tank returns to normal pressure (1 standard atmospheric pressure, that is, 0.1MPa), continue to soak the wood in the flame retardant solution, and perform normal pressure impregnation treatment to obtain normal pressure impregnated wood. , wherein the atmospheric pressure immersion treatment time is 40min.

3. Drying treatment

Place the impregnated wood under normal pressure at room temperature (15-30°C) for 7 days, then place it in a drying oven, and dry it at 103°C for more than 6 hours to obtain a flame-retardant impregnated wood, wherein the water content of the fire-retardant impregnated wood is 7% .

4. Thermal modification treatment

4-1) Put the flame-retardant impregnated wood in a high-temperature heat treatment test box, heat up, and raise the temperature to 140°C at a heating rate of 20°C/min, and keep it at 140°C for 20 minutes to perform high-temperature heat reform. sexual manipulation;

Among them: water vapor is used as the protective gas (water is placed in the test chamber, and as the temperature in the chamber rises, the water volatilizes to generate water vapor, which plays the role of protecting the protective gas. In addition to placing water in the test chamber to generate water vapor, Water vapor, nitrogen and other protective gases can also be passed into the box).

4-2) After heat preservation treatment for 20 minutes, stop heating, and take it out after the wood temperature drops to room temperature (15-30°C);

4-3) The wood is placed in a constant temperature and humidity test box, and the humidity is adjusted to adjust the moisture content of the wood to 10%, so as to obtain a flame-retardant heat-modified wood.

Embodiment 4 prepares flame-retardant thermally modified wood

1. Preparation of modified flame retardant solution

Dissolve the modified nitrogen-phosphorus flame retardant prepared in Example 1 in water, stir and dissolve evenly to obtain a modified flame retardant solution, the mass percentage concentration of the modified flame retardant solution is 15%, that is, every 15g of modified nitrogen-phosphorus Flame retardant solution in 85g of water, ready.

2. Dipping treatment

2-1) Vacuum impregnation treatment

Pour the flame retardant solution into the impregnation tank equipped with fast-growing poplar, soak the wood completely, and connect the vacuum pump; turn on the vacuum pump for vacuum treatment, so that the vacuum degree in the tank is reduced and maintained at -0.03MPa. Carry out vacuum impregnation treatment to wood under pressure state, make vacuum impregnation wood, wherein, the volume ratio of wood and flame retardant solution is 1:3, and treatment time is 40min;

2-2) Atmospheric pressure impregnation treatment

Turn off the vacuum pump, open the vacuum pressurized tank, so that the pressure in the tank returns to normal pressure (1 standard atmospheric pressure, that is, 0.1MPa), continue to soak the wood in the flame retardant solution, and perform normal pressure impregnation treatment to obtain normal pressure impregnated wood. , wherein the atmospheric pressure immersion treatment time is 20min.

3. Drying treatment

Place the impregnated wood under normal pressure at room temperature (15-30°C) for 7 days, then place it in a drying oven, and dry it at 103°C for more than 6 hours to obtain a flame-retardant impregnated wood, wherein the water content of the fire-retardant impregnated wood is 15% .

4. Thermal modification treatment

4-1) Put the flame-retardant impregnated wood in the high-temperature heat treatment test box, heat up the temperature, raise the temperature to 130°C at a heating rate of 10°C/min, keep it at 130°C for 40 minutes, and carry out high-temperature heat reform. sexual manipulation;

Among them: water vapor is used as the protective gas (water is placed in the test chamber, and as the temperature in the chamber rises, the water volatilizes to generate water vapor, which plays the role of protecting the protective gas. In addition to placing water in the test chamber to generate water vapor, Water vapor, nitrogen and other protective gases can also be passed into the box).

4-2) After heat preservation treatment for 50 minutes, stop heating, and take it out after the wood temperature drops to room temperature (15-30°C);

4-3) The wood is placed in a constant temperature and humidity test box, and the humidity is adjusted to adjust the moisture content of the wood to 12%, so as to obtain a flame-retardant heat-modified wood.

Comparative example 1

1. Drying treatment The same wood as in Example 2 was directly placed in a drying oven, and dried at 103° C. for 6 hours until the water content of the wood was 10%.

2. Thermal modification treatment

Except that the thermal modification treatment temperature is 220° C. and the heat preservation time is 120 min, the rest is the same as the thermal modification treatment in Example 2.

Comparative example 2

1. Dipping treatment

Except using distilled water instead of flame retardant solution, all the other are identical with the dipping treatment of embodiment 2;

2. Drying treatment

Same as the steps and processing conditions of the drying treatment of embodiment 2;

3. Thermal modification treatment

The steps and treatment conditions of the thermal modification treatment in Example 2 are the same.

Comparative example 3

1. Dipping treatment

Except using distilled water instead of flame retardant solution, all the other are identical with the dipping treatment of embodiment 2;

2. Drying treatment

Same as the steps and processing conditions of the drying treatment of embodiment 2;

3. Thermal modification treatment

Except that the thermal modification treatment temperature is 200° C. and the heat preservation time is 120 min, the rest are the same as the thermal modification treatment in Example 2.

Comparative example 4

Except that no thermal modification treatment is carried out, the rest are the same as in Example 2.

The prepared wood was scanned with an electron microscope to observe the distribution of flame retardants inside the wood. The electron microscope scan picture is shown in Figure 4.

It can be seen from Figure 4 that most of the flame retardant is suspended on the surface of the wood cell wall in the form of particles inside the wood, and the contact area between the flame retardant and the wood surface is small. Except for the flame retardant particles, most of the wood cell wall is exposed. It shows that the distribution uniformity and combination of flame retardants in the wood cell wall are poor, and they are easy to be lost during use, thus losing or reducing the flame retardant performance.

Test Example 1 Drug Loading Test

1. Weigh and record the mass (M ₀ , g) and volume (v, m ³ ) of the raw materials (fast-growing poplar) in Examples 2-4 and Comparative Examples 1-4 before dipping treatment.

2. Wipe off the residual liquid on the surface of the impregnated wood in Examples 2-4 and Comparative Examples 1-4, and immediately weigh and record the mass (M ₁ , g) of the impregnated wood.

3. Calculate the wood drug loading rate according to formula (1), and the measurement results are as shown in Table 1,

Drug loading=(M ₁ -M ₀ )c/v×100%(1)

Among them: M ₁ —the mass of the sample after immersion, in grams (kg); M ₀ —the mass of the sample before immersion, in grams (kg). c—solution mass fraction, %; v—sample volume, m ³ .

Test example 2 Wood swelling test

According to GB/T1934.2-2009 "Wood Swelling Test Method", put the thermally modified wood and raw material samples prepared in Example 2-4 and Comparative Example 1-4 into the oven, and heat up to 60°C And keep it at 60°C for 4 hours; then, according to the national standard "Method for Determination of Moisture Content of Wood (GB/T1931-2009)", the wood samples were dried and weighed respectively, and the wood samples were measured at the center of each opposite surface of the sample. The radial, chord and length along the grain (l ₀ ) of the sample is completely dry, with an accuracy of 0.001 mm; then, the sample is moisture-absorbed to 0.001 mm at a temperature of 20±2°C and a relative humidity of 65±3%. Dimensional stability. During the moisture absorption process, use 2-3 samples to measure the change of the chord dimension of the wood every 6 hours. When the difference between the two measurement results does not exceed 0.2mm, the dimension is considered to be stable; the final test The moisture absorption equilibrium size (l _w ) of all samples is accurate to 0.001 mm.

When the sample is completely dry to moisture absorption equilibrium, the linear wet expansion rate in the radial or chord direction is calculated according to formula (2), with an accuracy of 0.1%.

a _w = (l _w -l ₀ )/l ₀ ×100% (2)

In the formula:

a _w — linear wet expansion rate in the radial or chord direction of the sample from completely dry to moisture absorption equilibrium, %;

l _w —the radial or chord length of the sample when it absorbs moisture in balance, the unit is millimeter (mm)%;

l ₀ —the radial or chord length of the sample when it is completely dry, the unit is millimeter (mm)%;

When the sample is completely dry to moisture absorption balance, the volumetric swelling rate is calculated according to formula (3), accurate to 0.1%.

S=(v _w -v ₀ )/v ₀ ×100% (3)

In the formula:

S—volume swelling rate of the sample from completely dry to moisture absorption equilibrium, %;

v _w - the volume of the sample at moisture absorption equilibrium, the unit is cubic millimeter (mm ³ )%;

v ₀ —the volume of the sample when it is completely dry, the unit is cubic millimeter (mm ³ )%;

When the sample is completely dry to moisture absorption balance, the radial or chord anti-swelling coefficient is calculated according to formula (4), accurate to 0.1%.

ASE＝(S _C -S _T )/S _C ×100％(4)

In the formula:

ASE—anti-swelling coefficient, %;

S _C — volume swelling rate of untreated material (ie raw material), %;

S _T — volumetric swelling rate of the treated material, %;

The results of the wood swelling test are shown in Table 1.

Table 1 The drug loading and hygroscopic expansion rate test results of heat-treated wood

It can be known from Table 1 that:

1. The flame-retardant thermally modified wood prepared in the embodiment of the present invention has a high drug loading capacity, reaching more than 35kg/ ^m3 , and the flame retardant content in the prepared wood reaches the standard of not less than 30kg/ ^m3 , and the flame-retardant performance of wood it is good.

2. The hygroscopic expansion rate of the flame-retardant thermally modified wood prepared in the embodiment of the present invention is reduced, and the anti-wet expansion coefficients in the radial direction and the chord direction are respectively more than 21% and 37%, and the radial hygroscopic expansion rate is lower than 1.5-%. The hygroscopic expansion rate is lower than 1.7%, indicating that the high-temperature thermal modification treatment obviously improves the dimensional stability of the pre-treated wood and reduces the hygroscopicity of the wood.

3. Compared with the traditional heat treatment (comparative example 1, 220°C treatment for 120 min) of the flame-retardant heat-modified wood prepared in the embodiment of the present invention, the heat-treatment temperature is significantly reduced, and the heat-treatment time is significantly shortened, which can significantly reduce the flame-retardant heat-modified wood. production cost.

The flame-retardant thermally modified wood prepared by the method of the present invention can achieve the effect of improving the dimensional stability of the wood at a lower temperature (140-150°C) and a shorter time (20-40min), and the dimensional stability can be improved to the same or equal Higher than the effect of traditional heat-treated wood.

4. Compared with the flame-retardant heat-modified wood prepared by the embodiment of the present invention and the low-temperature heat treatment according to the present invention (comparative example 2, 150° C. for 30 min) after the water impregnation treatment, the chemical composition in the wood changes weakly during the treatment process, which is close to the surface. The water-based groups such as -OH do not decrease significantly, and the dimensional stability of the modified wood does not improve compared with the material, and the hygroscopic expansion rate (radial, chord, volume) is the same as that of the original material; the coefficient of moisture expansion resistance (radial, chord to) are all 0;

Compared with high-temperature heat treatment after water immersion treatment (comparative example 3, 200 ° C treatment for 120 minutes), the dimensional stability of wood has been improved to a certain extent, and the radial anti-swelling coefficient reaches 15.8%; the chord anti-swelling coefficient reaches 37 %.

In the process of preparing flame-retardant thermally modified wood by the method of the present invention, the modified nitrogen-phosphorus flame retardant catalyzes the dehydration and carbonization of wood hemicellulose in a short time (20-40 min) at a relatively low temperature (130-150 ° C), so that the hydrophilic The reduction of water groups such as -OH and the formation of chemical bonds between flame retardants and wood reduce the moisture absorption of wood and improve dimensional stability. Reached more than 37%, the maximum reached 51.9%.

5. Compared with the flame-retardant thermally modified wood prepared in the embodiment of the present invention and only carrying out the flame-retardant impregnation treatment (comparative example 4), since the flame retardant and the wood are mainly combined in the form of physical filling, the nitrogen-phosphorus flame retardant It contains unreacted urea and a large number of hydrophilic groups such as _-NH2 , etc. The hygroscopicity of the treated material is higher than that of the material, and the dimensional stability is reduced. The radial and tangential anti-swelling coefficients are all negative;

During the thermal modification process of the flame-retardant thermally modified wood prepared in the embodiment of the present invention, the flame retardant in the agglomerated state redistributes in a high-temperature and high-humidity environment, forms a chemical bond with the wood fiber and catalyzes the carbonization of the wood to remove -OH, Both the flame retardant and the hydrophilic components in the wood were reduced, and the dimensional stability of the flame-retardant heat-modified wood was improved.

Test Example 3 Wood surface color difference test

1. Take the thermally modified poplar and raw materials prepared in Examples 2-4 and Comparative Examples 1-4 respectively as test pieces, with a size of 50mm×50mm×20mm;

2. According to the color evaluation, use the color measurement method stipulated by the International Commission on Luminescence and Illumination (CIE), that is, the CIE standard chromaticity system to determine the three basic indicators of wood (L*, a* and b* values) to accurately determine the color of heat-treated wood Quantitative characterization, and analysis of the overall color difference (ΔE*) and visual physical parameters according to the experimental results; three points were taken from both sides of the sample in the chord direction and radial direction for measurement, and the average value was taken as the final measurement value.

The three main basic indicators L*, a*, b* of the CIE (L*a*b*) standard chromaticity characterization system, among which

L*: lightness, a completely white object is regarded as 100, and a completely black object is regarded as 0;

a*: Red-green axis chromaticity index, the larger the positive value, the more red the color is, and the larger the negative value, the more green;

b*: Yellow-blue axis chromaticity index, the larger the positive value, the more yellow the color is, and the larger the negative value, the more blue.

The color difference ΔE* and saturation C* are deduced from the changes of these three basic indicators according to the formulas (5) and (6).

ΔE*＝(△L* ² +△a* ² +△b* ² ) ^l/2 (5)

C*＝(a* ² +b* ² ) ^l/2 (6)

In the formula:

a*—red-green axis chromaticity index value;

b*—the chromaticity index value of the yellow-blue axis;

ΔL*—Lightness change value;

Δa*—the change value of chromaticity index of red-green axis;

Δb*—the change value of the chromaticity index of the yellow-blue axis;

The color and visual physical parameters of the heat-treated wood were measured with a TC-PIIG automatic color difference meter (Beijing Optical Instrument Factory), and the average values of the measurement results are shown in Table 2.

Test example 4 wood surface hardness test

The thermally modified wood and raw materials prepared in Examples 2-4 and Comparative Examples 1-4 were respectively taken as test pieces with a size of 50mm×50mm×20mm; the surface hardness of the test pieces was tested with a Shore hardness tester TH210.

Press vertically into the surface of the sample under the action of the test force. When the surface of the presser foot is completely attached to the surface of the sample, the tip of the indenter has a certain protruding length L relative to the plane of the presser foot. The Shore hardness HD (HD=100-L) is characterized by the L value. The larger the L value, the lower the Shore hardness, and vice versa. The measurement results are shown in Table 2.

Surface hardness and color of table 2 comparative example and embodiment specimen

Numbering Surface hardness L* a* b* ΔE* C* Example 2 51.14 52.06 11.26 22.45 33.65 25.12 Example 3 51.36 53.94 10.35 24.44 29.45 26.54 Example 4 53.74 45.725 10.09 21.06 41.9 23.3513 --> Comparative example 1 42.26 47.18 9.87 20.8 36 23.02 Comparative example 2 51.07 82.43 3.45 18.38 4.99 18.7 Comparative example 3 47.72 62.27 9.04 24.69 24.09 26.29 Comparative example 4 53.41 82.43 3.44 18.39 2.76 18.71 material 51.49 86.2 2.35 15.31 - 15.49

It can be seen from Table 2:

1. The thermally modified wood prepared in Comparative Example 1 and Comparative Example 3 was treated at 200°C and 220°C for 120 minutes respectively, and the surface color decreased compared with the lightness value L* of the material, and the chromaticity index a* of the red-green axis and the yellow-blue axis The chromaticity index value b* increases, the saturation C* increases from 15.49 to 23.02-26.29, the increase rate reaches 32%-41%, and the wood surface decoration is improved; the heat-modified wood in Comparative Example 2 is treated at 150 °C for 30 minutes, There is no obvious change in the surface color of the wood, and the surface decoration effect of the modified wood cannot be increased; the wood prepared in Comparative Example 4 is only treated with flame-retardant impregnation, and the chromaticity parameters have no obvious change, and the surface decoration effect of the modified wood cannot be increased.

2. The flame-retardant thermally modified wood prepared by the method of the present invention can also achieve color brightness due to the decomposition of ammonium polyphosphate and ammonium phosphate with a low degree of polymerization in the flame retardant at 130-150°C to produce phosphoric acid and other catalytic wood fiber dehydration Decrease, and the red-green axis chromaticity index value a*, yellow-blue axis chromaticity index value b* increases, the saturation C* increases by about 38% compared with the material; the red-green axis chromaticity index a*, yellow-blue axis chromaticity index value b* increases The axial chromaticity index value b* is larger, the saturation is larger, and the material color tends to be more brown, which is closer to the color of some precious woods, which shows that the specimen treated by the embodiment of the present invention can have better color decoration performance.

3. The surface hardness of the heat-treated wood prepared in Comparative Example 1 and Comparative Example 3 decreased by more than 7.32% compared with the material, indicating that the treatment in a high-temperature and high-humidity environment will lead to a decline in the surface properties of the wood, which will further affect the later surface processing and application of the treated wood. However, the flame-retardant heat-modified wood prepared by the method of the present invention has no decrease in surface hardness compared with the material.

Test Example 6 Flame Retardancy Test

Take respectively the heat-treated wood prepared in Examples 2-4 and Comparative Example 1-4 and the poplar wood as the raw material (the size is 100mm × 100mm × 20mm), according to ISO5660-1:2002 "Response to fire experiment heat release, smoke Yield and mass loss rate Part 1: Heat release rate (cone calorimeter method) "The method specified in "FTT0242 cone calorimeter is used for flame retardant test.

Before the test, according to ISO554, the flame-retardant poplar specimens were cured at a temperature of 23±2°C and a relative humidity of 50±5% until the quality was constant (the moisture content was 9%). When the difference between the mass of the sample does not exceed 0.1% of the mass of the sample or 0.1g (whichever is the largest value) in the two weighings separated by 24h, it is considered to have reached a constant mass.

The flame retardant performance measurement results of heat-treated wood are shown in Table 3; the heat release rate HRR curves of heat-treated wood and raw materials prepared in Examples 2-4 and Comparative Examples 1-4 are shown in Figure 1; smoke release performance measurement results As shown in Table 4; the total smoke release TSR curves of the heat-treated wood and raw materials prepared in Examples 2-4 and Comparative Examples 1-4 are shown in Figure 2.

Table 3 Flame retardant performance test results of heat-treated wood specimens

Note: HRR in the table represents the average heat release rate, PHRR1 represents the peak heat release at low temperature, PHRR2 represents the peak heat release at high temperature, TPHRR1 represents the time at which the peak heat release at low temperature occurs, TPHRR2 represents the time at which the peak heat release at high temperature occurs, and THR represents the total heat of combustion The amount released, RM means the residual amount of charcoal in combustion.

It can be seen from Table 3 that,

1. Compared with the heat-treated wood and materials prepared by the comparison example, the flame-retardant thermally modified wood prepared by the method of the present invention has a significantly lower total heat release rate HRR and a total heat release amount THR, an increase in residual charcoal amount RM, and a significantly enhanced flame-retardant effect .

2. The flame retardant thermally modified wood prepared by the method of the present invention is compared with the thermally modified wood without flame retardant composition, the total heat release rate HRR and the total heat release amount THR are significantly reduced, the residual carbon amount RM is increased, and the flame retardant effect Significantly enhanced, where:

A) The total heat release rate HRR is about 60% lower, the total heat release THR is about 55% lower, and the residual charcoal amount RM is about 92% higher, indicating that the flame-retardant thermally modified wood prepared by the present invention is compared with general high-temperature heat-treated wood. The flame retardant performance is greatly improved;

B) The peak heat release rate PHRR ₁ decreased by about 66%, and PHRR ₂ decreased by about 54%, indicating that the burning intensity of flame-retardant thermally modified wood decreased significantly; the time of the peak heat release rate TPHRR ₁ and TPHRR ₂ increased by about 7s- 16s, 79s-135s, indicating that the flame-retardant thermally modified wood is delayed in the violent combustion stage, and the combustion safety performance is improved. Once a fire occurs, the combustion of flame-retardant thermally modified wood can provide valuable time for personnel evacuation and firefighting work;

3. Compared with the fire-retardant thermally modified wood prepared by the method of the present invention, the total heat release rate HRR and the total heat release amount THR are increased by 23% and 22%, respectively, compared with the wood prepared by the flame-retardant impregnation treatment, which shows that it is different from ordinary flame-retardant wood. Compared with wood treatment, thermal modification treatment can further improve the flame retardant performance of wood. The reason may be that on the one hand, the flame retardant chemically reacts with wood during the thermal modification process, and is more uniform in the interior of the wood. On the other hand, The flame retardant catalyzes the dehydration and carbonization of wood during the thermal modification process. Once a fire occurs, the time for the flame-retardant thermally modified wood to block the charcoal layer is shortened, and the exothermic reaction of wood combustion is weakened (as shown in Figure 1);

4. Compared with the material, the flame-retardant heat-modified wood prepared by the method of the present invention has a total heat release rate HRR reduced by 54-62%, a total heat release amount THR reduced by 25-46%, and a residual charcoal amount RM increased by 53-72%; The peak heat release rate decreases, and the intensity of combustion decreases significantly, especially the time TPHRR ₂ of the peak heat release rate increases by 125-170s, indicating that the most intense stage of combustion is delayed and the overall flame retardancy is improved.

Table 4 Comparison results of smoke release of heat-treated wood specimens

Note: COY represents the average carbon monoxide release, CO2Y represents the average carbon dioxide release, TSP represents the total smoke production, and SEA(600) represents the average specific extinction area within 600 seconds of combustion. The amount of smoke produced by consuming a unit mass of material under experimental conditions.

It can be seen from Table 4:

1. Due to the effect of flame retardant, the flame-retardant heat-modified wood prepared by the inventive method increases the insufficient degree of wood combustion, and the average _CO release decreases, and the incomplete combustion of wood produces more CO. However, in the fire, except CO and other toxic The gas poses a threat to the safety of personnel. Combustion smoke and solid particles can easily hinder breathing, block sight, and hinder the evacuation of trapped people, which is another major hidden danger in fire safety.

2. In the flame-retardant thermally modified wood prepared by the method of the present invention, since the flame retardant promotes wood pyrolysis to the direction of charcoal formation, it is beneficial to reduce the amount of smoke released, and the total smoke output of the combustion is greatly reduced.

3. As can be seen from Fig. 2 (the TSR curve of the total smoke release of wood burning), the flame-retardant thermally modified wood prepared by the method of the present invention has a smoke release that is significantly lower than that of the reference example during the entire combustion process, which increases the amount of smoke produced by the material. Combustion safety.

4. SEA (600s) represents the amount of smoke produced by consuming a unit mass of material at the initial stage of combustion (600s) under the experimental conditions. The flame-retardant heat-modified wood prepared by the embodiment of the present invention has a significant increase compared with the control example and the material. improve.

In summary, the wood prepared by the combination of flame retardancy and high-temperature steam heat treatment of the present invention not only has good material color and dimensional stability, but also has flame retardancy and smoke suppression performance, which improves the safety of the material in use.

Claims (10)

1. A preparation method for flame-retardant thermally modified wood, characterized in that it includes heat-treating the impregnated wood. 2. The preparation method according to claim 1, characterized in that, the dipping treatment comprises soaking wood under reduced pressure and normal pressure sequentially. 3. the preparation method as claimed in claim 1 or 2, is characterized in that, the vacuum degree of described decompression state＜0MPa. 4. The preparation method according to claim 1 or 2, characterized in that, the temperature of the heat treatment is 130-160°C. 5. A preparation method for flame-retardant thermally modified wood, characterized in that, comprising the steps carried out in the following order: 1) Soak the wood in a flame retardant solution, and perform vacuum impregnation treatment under reduced pressure to obtain vacuum impregnated wood; 2) continue to soak the vacuum-impregnated wood in the flame retardant solution, and perform normal-pressure impregnation treatment under normal pressure to obtain normal-pressure impregnated wood; 3) Drying the atmospheric pressure impregnated wood to obtain flame retardant impregnated wood; 4) Heat treatment of flame retardant impregnated wood. 6. The preparation method according to claim 5, wherein the flame retardant in step 1) is selected from nitrogen-phosphorus flame retardants and modified nitrogen-phosphorus flame retardants. 7. the preparation method as claimed in claim 5 or 6 is characterized in that, step 1) in the vacuum impregnation process described in vacuum <0MPa. 8. The preparation method according to claim 5 or 6, characterized in that the temperature of the wood heat treatment in step 4) is 130-160°C. 9. The preparation method according to claim 5 or 6, characterized in that, the thermal modification of wood in step 4) is to raise the temperature of wood to 130-160 °C at a heating rate of 5-20 °C/min. °C, keep at 130-160 °C for 20-50 min, preferably 30 min. 10. A flame-retardant heat-modified wood, characterized in that it is prepared according to any one of claims 1-9.