JP7101562B2 - Manufacturing method of non-combustible wood fiber board - Google Patents

Description

The present invention relates to a method for producing a non-combustible wood fiber board.

As a method for imparting nonflammability to wood materials such as solid wood and plywood, the wood materials are immersed in an aqueous solution (hereinafter referred to as "non-combustible solution") in which a water-soluble non-combustible agent is dissolved in water in the following Patent Document 1. A method of impregnating by repeating depressurization and pressurization several times is known.

Japanese Unexamined Patent Publication No. 2-270547 Japanese Unexamined Patent Publication No. 2000-037710

However, as is well known in the art, wood fiber boards such as MDF have a high-density hard layer on the front and back surfaces. Therefore, even if a wood fiber board is impregnated with a non-combustible solution by a conventional method, the front and back surfaces thereof. It is hardly impregnated from the hard layer. When the wood fiber board is impregnated with the non-combustible solution, the non-combustible solution enters from the low density part (intermediate layer located between the hard layers on the front and back) exposed at the end of the wood, and gradually impregnates toward the center in the longitudinal direction of the board. Therefore, in order for the non-combustible solution to be uniformly distributed over the entire wood fiber board (from the end of the wood to the center in the longitudinal direction), an impregnation treatment for several days is required, and the production efficiency becomes very poor. In addition, the non-combustible performance improves in proportion to the content of the non-combustible agent, and in order to contain more non-combustible agent, the number of impregnation treatments under reduced pressure must be increased, resulting in deformation such as swelling of the wood fiber board. There is a risk of damage such as cracking.

That is, it is difficult to impart sufficient non-combustibility (quasi-non-combustible or higher non-combustible performance stipulated in the technical standards of the Building Standards Act Enforcement Ordinance) to the wood fiber board only by impregnating it with a non-combustible solution as in the conventional technique. be. As a result of repeated studies and tests on imparting sufficient noncombustibility to the wood fiber board by a method other than impregnation, the present inventor used two types of non-combustible agents, a water-insoluble non-combustible agent and a water-soluble non-combustible agent, and made wood. A mixture obtained by mixing a water-insoluble incombustible agent with an adhesive into fibers is hot-press molded into a wood fiber board, and then the wood fiber board is immersed in an aqueous solution of the water-soluble incombustible agent to obtain the water-soluble incombustible agent. It has been found that a wood fiber board having semi-incombustible or higher non-combustible performance can be obtained by impregnating with a sufficient amount of non-combustible agent, and the present invention has been completed.

Therefore, the problem to be solved by the present invention is to provide a novel method capable of efficiently producing a non-combustible wood fiber board, and more specifically, to cause molding defects, deformation and breakage. It is an object of the present invention to provide a novel method capable of efficiently producing a wood fiber board having improved non-combustible performance by uniformly adhering a sufficient amount of a non-combustible agent over the entire wood fiber board.

In order to solve this problem, the invention according to claim 1 of the present application comprises a first step of hot-press molding a mixture of wood fibers mixed with an adhesive and a water-insoluble non-combustible agent to form a wood fiber board. It is a method for producing a non-combustible wood fiber board, which comprises sequentially performing a second step of immersing the wood fiber board obtained in one step in an aqueous solution of a water-soluble non-combustible agent and impregnating the wood fiber board.

The invention according to claim 2 of the present application is the method for producing a non-combustible wood fiber board according to claim 1, wherein a part of the entire amount of the adhesive required for molding is sprayed on the wood fiber in the first step. A step of adhering Step C to obtain a mixture of wood fiber, adhesive and water-insoluble non-combustible agent by spraying the rest of the entire amount of adhesive required for molding, and heat pressure molding of the mixture obtained in step C to make a wood fiber board. It is characterized in that the steps D for producing the above are sequentially performed.

In the invention according to claim 3 of the present application, in the method for producing a non-combustible wood fiber board according to claim 2, the required amount of 10 to 90% by weight of the adhesive is sprayed in the step A, and the required amount is described in the step C. It is characterized by spraying an amount of 90-10% by weight of the adhesive.

In the invention according to claim 4 of the present application, in the method for producing a non-combustible wood fiber board according to claim 2 or 3, in the step A, an adhesive of 3% or more with respect to the absolute dry weight of the wood fiber is sprayed, and the above-mentioned The step C is characterized in that an adhesive of 3% or more with respect to the absolute dry weight of the wood fiber is sprayed.

According to the present invention, in view of the fact that it was difficult to obtain a wood fiber board having sufficient non-combustible performance by a method of simply impregnating with a non-combustible solution, an adhesive and a water-insoluble non-combustible agent were mixed with the wood fiber. The first step of thermally forming the mixture into a wood fiber board and the second step of immersing the wood fiber board obtained in the first step in an aqueous solution of a water-soluble non-combustible agent and impregnating the mixture are sequentially performed. Manufactures wood fiber boards. According to the present invention, the wood fiber board contains a sufficient amount of non-combustible agent to exhibit semi-incombustible or higher non-combustible performance, and causes damage or deformation in both the first step and the second step. It is possible to manufacture a wood fiber board without making it.

That is, according to the present invention, the total amount of the non-combustible agent contained in the wood fiber board is mixed and impregnated separately in the first step and the second step. The amount of non-combustible chemicals mixed or impregnated in each step can be small. When a mixture obtained by mixing a large amount of non-combustible chemicals is hot-press molded, the non-combustible chemicals that cannot be sufficiently adhered to the wood fibers are hot-press molded while floating, resulting in molding defects such as punctures and cracks. In addition, if a large amount of non-combustible chemical is impregnated, a long-time impregnation treatment is required as described above, and the wood fiber board may be deformed such as swelling or damaged such as cracks. According to the invention, since the amount of the non-combustible agent used in each step is relatively small, these disadvantages and disadvantages do not occur.

In addition, since a water-insoluble non-combustible agent is used in the first step, even when the wood fiber board obtained in the first step absorbs moisture, the non-combustible agent dissolves on the surface of the wood fiber board with the moisture. It does not reduce the appearance, surface smoothness, or nonflammability. Further, when the incombustible agent is impregnated into the aqueous solution of the incombustible agent in the second step, the incombustible agent mixed in the first step does not dissolve and the incombustibility is not lowered.

In one preferred embodiment of the present invention, in the first step, a method of spraying the adhesive required for molding in two stages and mixing a water-insoluble incombustible agent between them is adopted. That is, by spraying a part of the total amount of the adhesive required for molding, preferably 10 to 90% by weight, onto the wood fiber (step A), the adhesive can be evenly and uniformly adhered to the wood fiber. By mixing the entire amount of the water-insoluble non-combustible agent with the obtained adhesive-attached wood fiber (step B), the water-insoluble non-combustible agent can be evenly and evenly adhered to the wood fiber via the adhesive. By spraying the balance of the total amount required for molding, preferably 90 to 10% by weight of the adhesive (step C), a mixture obtained by uniformly mixing the wood fiber, the adhesive and the water-insoluble incombustible agent is obtained. Therefore, by hot-press molding this mixture (step D), it is possible to produce a wood fiber board in which the non-combustible agent is evenly and evenly distributed. That is, even a long wood fiber board can be a wood fiber board having substantially uniform non-combustible performance in the length direction.

Further, according to the embodiment of the present invention, the entire amount of the adhesive required for molding into the wood fiber board is not added at once, but is added in two stages. Therefore, from the test results described later. As is also clear, it is necessary to efficiently produce wood fiber boards with improved non-combustibility by uniformly adhering non-combustible chemicals to the entire wood fiber board without causing molding defects, deformation or breakage. Can be done.

In the above embodiment, in step A, 3% or more of the adhesive is sprayed on the absolute dry weight of the wood fiber, and in step B, 3% or more of the adhesive is sprayed on the absolute dry weight of the wood fiber. Is preferable, and this makes it possible to more reliably realize the above-mentioned effect.

It is explanatory drawing which shows the 1st process of the manufacturing method of the non-combustible wood fiber board by this invention. It is explanatory drawing which shows the 2nd process performed following the 1st process. 6 is a photomicrograph (magnification: 150 times) showing the state of adhesion of the adhesive to the wood fiber after step C in Example 2 (Example 4). It is a micrograph (magnification: 300 times) which shows the same part as FIG. 3 by magnifying further.

The present invention has a first step and a first step of forming a wood fiber board by hot-press molding a mixture of wood fibers mixed with an adhesive and a water-insoluble non-combustible agent (hereinafter referred to as "non-combustible powder"). A method for producing a non-combustible wood fiber board, which comprises sequentially performing a second step of immersing the wood fiber board obtained in the above step in an aqueous solution of a water-soluble non-combustible agent (hereinafter referred to as "non-combustible solution") and impregnating the wood fiber board. Yes, in one preferred embodiment, the first step sprays a portion of the total amount of adhesive required for molding, preferably 10-90% by weight of the required amount, onto the wood fiber to turn the adhesive into wood fiber. The step A of adhering, and the step B of mixing a predetermined amount of non-combustible powder necessary for imparting non-combustibility to the mixture obtained in step A and adhering the non-combustible powder to the wood fiber via an adhesive. The mixture obtained in step B is sprayed with the balance of the total amount of the adhesive required for molding into a wood fiber board, preferably 90 to 10% by weight of the required amount, to consist of the wood fiber, the adhesive and the non-combustible powder. Step C for obtaining the mixture and step D for producing a wood fiber board by hot-press forming the mixture obtained in step C are sequentially performed.

Explaining with reference to FIGS. 1 and 2, a wood fiber 10 is prepared (a), and the wood fiber 10 is put into a blender 11 and stirred (b), while the adhesive 13a is first sprayed from the spray 12 (c). Then, the non-combustible powder 15 is mixed from the chemical charging device 14 (d). Since the adhesive 13a has already adhered to the wood fiber 10 at this point, the wood fiber in FIG. 1 (d) is designated by the reference numeral 10a to indicate this, and the wood fiber 10 before attachment (FIG. 1). It is shown by a thicker line than (a) and (b)) (the same applies to the wood fibers 10b and 10c shown in FIGS. 1 (e) and later).

Next, the adhesive 13b is secondarily sprayed from the spray 16 (which may be the same as the spray 12) to the wood fiber 10b to which the primary spray adhesive 13a and the non-combustible powder 15 are attached (e), and the primary spray is performed. A mixture having the wood fiber 10c to which the spray adhesive 13a, the non-combustible powder 15 and the secondary spray adhesive 13b is attached is obtained (f). In FIGS. 1 (b) to 1 (d), the arrows indicate that the wood fibers 10 and 10a are agitated. By heat-pressing the mixture (f) thus obtained between the upper and lower heating plates 17 and 18 (g), a wood fiber plate 19 whose non-combustible performance is enhanced by the non-combustible powder 15 is obtained (h).

The steps shown in FIGS. 1 (a) to 1 (h) correspond to the first step, of which FIG. 1 (c) corresponds to the step A and FIG. 1 (d) corresponds to the step B. 1 (e) corresponds to the step C, and FIG. 1 (g) corresponds to the step D.

Next, the wood fiber plate 19 is placed in the vacuum pressure impregnator 21 and immersed in the noncombustible solution 20, and the vacuum pressurization is repeated to impregnate the noncombustible solution 20 (i). By drying after this impregnation treatment, a non-combustible wood fiber board 22 whose incombustibility is enhanced by two kinds of non-combustible agents, a water-insoluble non-combustible agent and a water-soluble non-combustible agent, is finally obtained (j). The step shown in FIG. 2 (i) corresponds to the second step, and the non-combustible wood fiber board 22 is manufactured through the first step and the second step.

As the wood fiber 10, wood fiber obtained by steaming and defibrating coniferous or broadleaf wood can be used, and wood fiber derived from construction waste or pallet waste, plant fiber such as pulp, hemp, and flax, etc. can be used. It may be. Examples of the adhesives 13a and 13b sprayed in FIGS. 1 (c) and 1 (e) include a urea resin adhesive, a melamine resin adhesive, a urea-melamine cocondensate resin adhesive, a phenol resin adhesive, or MDI ( Diphenylmethane diisocyanate), TDI (Torrenizing isocyanate), MDI prepolymer, TDI prepolymer and other isocyanate resin adhesives can be used.

As the water-insoluble incombustible agent 15 mixed in FIG. 1 (d), a metal hydroxide-based incombustible agent (aluminum hydroxide, magnesium hydroxide, etc.) known as a water-insoluble incombustible agent can be used, and water-soluble. A non-combustible agent (phosphoric acid-based, boric acid-based, halogen-based, etc.) may be modified to be water-insoluble by water-insolubilizing the surface. Examples of the water-soluble non-combustible agent used in FIG. 2 (i) include phosphoric acid-based non-combustible agents such as phosphoric acid and ammonium phosphate, and boric acid-based non-combustible agents such as boric acid, sodium borate, and sodium polyborate. Halogen-based non-combustible agents such as ammonium bromide, calcium chloride, and antimony chloride can be used.

Examples of the present invention will be described below with reference to comparative examples. In Test 1, in the first step (FIG. 1), 926 g of wood fiber (using wood fiber obtained from broad-leaved wood waste wood of a plurality of tree species) was added to 926 g of wood fiber (wood fiber) in an absolute dry weight, and 274 g (wood fiber) was required for molding. (Approximately 30% of the absolute dry weight of wood fiber) and 303 g (approximately 33% of the absolute dry weight of wood fiber) of non-combustible powder 15 (aluminum hydroxide). The mixture obtained by mixing) was hot-press molded.

More specifically, for the first step, 50% of the required amount of the adhesive 13a is sprayed while stirring the wood fiber 10 in the blender 11 (FIG. 1 (c), step A), and the non-combustible powder is sprayed thereto. The body 15 is mixed (FIG. 1 (d), step B), and then the required amount of the remaining amount (50%) of the adhesive 13b is sprayed (FIG. 1 (e), step C) to obtain the mixture 10c (FIG. 1 (e), step C). FIG. 1 (f)), the mixture 10c was placed in a cube-shaped (300 × 300 × 300 mm) cylinder and pressed to shape the mixture, and then the cylinder was removed to obtain a thickness of 30 to 80 × 300. It was decided to sandwich the front and back of the mixture 10c of × 300 mm between the heating plates 17 and 18, and heat-press form the mixture under the conditions of a temperature of 180 ° C., a surface pressure of 46 kg / cm ² , and a heat pressure time of 8 minutes (FIG. 1 (g), step. D). As a result, a wood fiber board 19 having a thickness of 14 mm was manufactured (FIG. 1 (h)). As shown in FIG. 1, steps A to C were carried out in the blender 11.

In the second step, the wood fiber plate 19 is immersed in a non-combustible solution 20 (using a solution having a concentration of sodium polyborate of 23%) in a vacuum pressure impregnator 21, and the pressure is reduced (pressure reduction 50 mmHg, pressure reduction time 2 hours). ) And pressurization (pressurization degree 9 MPa, pressurization time 24 hours) to impregnate the incombustible solution 20, then take out from the depressurized pressurizing impregnator 21 and dry in a dryer (temperature 80 ° C., 72). Time) to obtain the final wood fiber board 22.

In Examples 1 and 2, the first step and the second step are carried out as described above, and the incombustible wood fiber board whose incombustibility is enhanced by two kinds of incombustible agents, a water-insoluble incombustible agent and a water-soluble incombustible agent. 22 was obtained (FIG. 2 (j)). In Example 1, 132 g of a water-soluble non-combustible agent is contained by immersing in a non-combustible solution 20 in the second step and impregnating the solution, and in Example 2, the impregnating solution is performed by immersing in the non-combustible solution 20 in the second step. Thereby, 105 g of the water-soluble non-combustible agent was contained.

On the other hand, in Comparative Example 1, the first step was the same as in Examples 1 and 2 except that 463 g of non-combustible powder 15 was mixed, which was larger than the non-combustible powder 15 (303 g) used in Examples 1 and 2 in the first step. The process was carried out, but the second step was not carried out. Further, in Comparative Example 2, the content (132 g, 105 g) of Examples 1 and 2 was changed by changing the impregnation treatment conditions while immersing in the same non-combustible solution 20 as the non-combustible solution 20 used in Examples 1 and 2 in the second step. ) The second step was carried out in the same manner as in Examples 1 and 2 except that 189 g of the water-soluble non-combustible agent was contained, but the non-combustible powder was not mixed in the first step and was required for molding. The entire amount of the adhesive was sprayed in the first spraying step (step A). This Comparative Example 2 corresponds to the above-mentioned prior art (Patent Document 1).

As a result of evaluating Examples 1 and 2 and Comparative Examples 1 and 2 thus obtained, the moldability when the wood fiber board was molded in the first step and the nonflammable performance of the wood fiber board obtained after the second step were evaluated. Is shown in Table 1. In addition, according to Article 2, Item 9 of the Building Standards Act, it is required to meet the requirements for obtaining non-combustibility certification in the heat generation test (heating a 10 cm x 10 cm test piece at 50 kW / m ² ) in accordance with ISO5600-1. In the heat generation test, the non-combustible performance was evaluated for 20 minutes for non-combustible materials, 10 minutes for semi-non-combustible materials, 5 minutes for flame-retardant materials, and (1) total calorific value of 8 MJ / m ² or less. It is said that it is necessary to meet the three requirements of (2) no cracks and holes penetrating to the back surface, and (3) the heat generation rate does not exceed 200 kW / m ² continuously for 10 seconds or more. Therefore, a test was conducted in light of this standard to evaluate whether the nonflammable performance was "flame retardant", "quasi-nonflammable" or "nonflammable". As for the total calorific value, the subsequent measurement was stopped when the total calorific value exceeded 8 MJ / m ² .

As shown in Table 1, in Examples 1 and 2, the wood fiber plate 22 (FIG. 1 (j)) formed in the first step did not show any damage such as cracks or holes, and showed good formability. On the other hand, in Comparative Example 1, molding was defective. The reason for this is that the non-combustible powder was added in an excessive amount to the wood fiber and the adhesive, so that the non-combustible powder could not sufficiently adhere to the wood fiber via the adhesive and was simply dispersed. It is presumed that molding defects (so-called punctures) occurred during thermal pressure.

Further, in Examples 1 and 2, by performing the second step on the wood fiber plate 22 formed in the first step, semi-incombustible non-combustible agents are used for two types of non-combustible agents, a water-insoluble incombustible agent and a water-soluble incombustible agent. A non-combustible wood fiber plate 22 having performance was obtained, but in Comparative Example 1 in which the second step was not carried out, not only molding defects occurred as described above, but also non-combustible performance and flame retardancy were not satisfied. Met. Further, even in Comparative Example 2 impregnated with the non-combustible solution only in the second step, although it was immersed in the non-combustible solution 20 so as to contain a larger amount of the water-soluble non-combustible agent than in Examples 1 and 2, it was flame-retardant. It was limited to non-combustible performance and did not reach semi-non-combustible non-combustible performance. The reason for this is that, as described above in relation to the prior art, the impregnation treatment for the wood fiber board takes a long time, so the impregnation treatment conditions adopted in this test (2 hours of decompression and 24 hours of pressurization). It is presumed that this was insufficient to impregnate a large amount of the non-combustible solution 20, and as a result, sufficient non-combustible performance could not be obtained. Further, by immersing in an excessive amount of the non-combustible solution 20, cracks and peeling were observed in the wood fiber board after impregnation.

From the test results and considerations described above, in order to obtain a wood fiber board having semi-incombustible or higher non-combustible performance without impairing moldability, a mixture mixed with a water-insoluble non-combustible agent (non-combustible powder) is used. It was confirmed that it is indispensable to sequentially carry out the first step of thermal pressure molding and the second step of impregnating the wood fiber plate obtained by this with an aqueous solution (non-combustible solution) of a water-soluble non-combustible agent.

In Test 1, the amount of the adhesive sprayed in the first spray (step A) and the second spray (step C) in the first step was set to 50% of the total amount (274 g). Next, these adhesives were used. Test 2 was performed with various spray amounts. That is, in Examples 3 to 5, in step A, a part of the amount of adhesive required for molding (90%, 50%, 10% with respect to the total amount) was sprayed while stirring the wood fiber, and the non-combustible powder was used. After the body mixing step B, in step C, the balance of the required amount of adhesive (10%, 50%, 90% with respect to the total amount) while stirring the wood fiber after mixing the adhesive and the non-combustible powder. Was sprayed to obtain a mixture. In Comparative Example 3, the entire required amount of adhesive was sprayed in step A (without step C), and in Comparative Example 4, the entire required amount of adhesive was sprayed in step C. (No step A). Example 4 is the same as Example 2 of Test 1. The same wood fibers, adhesives, non-combustible powders, etc. as in Test 1 were used.

The mixture of each Example and Comparative Example thus obtained was hot-press molded under the above conditions, and the presence or absence of molding defects was evaluated. Table 2 shows the mixing conditions of the wood fibers, the adhesive and the non-combustible powder in Examples 3 to 5 and Comparative Examples 3 and 4 in Test 2 and the presence or absence of molding defects by visual observation.

As shown in Table 2, molding defects did not occur in Examples 3 to 5 in which the required amount of the adhesive was sprayed in two stages of step A and step C, but the total amount of the required amount of the adhesive was once applied. In Comparative Examples 3 and 4 sprayed on the above, molding was defective. The reason for this can be thought of as follows.

The purpose of spraying the adhesive in step A is to adhere the adhesive evenly and evenly over the entire wood fiber, and by doing so, the incombustible powder mixed in the subsequent step B is passed through the adhesive. It can be evenly and evenly adhered to wood fibers.

On the other hand, in Comparative Example 2 in which the step A was not carried out, even if the non-combustible powder was added in the step B, the powdery non-combustible powder did not sufficiently adhere to the wood fiber to which the adhesive was not adhered. It is just a distributed state. Therefore, even if the required amount of the adhesive is sprayed in the step C, the non-combustible powder floats up, causing molding defects (so-called puncture) at the time of heat pressure. Further, when the bottom of the blender was observed after performing step B in which the non-combustible powder was mixed, the non-combustible powder did not fall to the bottom in any of Examples 3 to 5, whereas in Comparative Example 4, the blender was observed. It was confirmed that a large amount of non-combustible powder had fallen to the bottom of the. This means that even if molding is possible, a sufficient amount of non-combustible powder cannot be mixed into the wood fiber board, and the effect of improving non-combustible performance is insufficient.

The spraying of the adhesive in the step C is for applying the adhesive to the surface of the non-combustible powder adhered to the wood fiber through the steps A and B, and to make up for the shortage of the adhesive sprayed in the step A. This is done to apply the adhesive required for molding to the wood fiber board. According to Examples 3 to 5, a state in which the non-combustible powder is evenly and evenly adhered to the wood fiber via the adhesive is obtained through the steps A and B, and therefore the remaining amount is adhered in the step C. By spraying the agent, a mixture in which the non-combustible powder and the adhesive are evenly mixed with the wood fiber is obtained, and the moldability is improved. 3 and 4 are micrographs showing the state of Example 2 (Example 4) after step C, and the adhesive (which looks like granules) is evenly and evenly adhered to the entire wood fiber. You can see that.

On the other hand, in Comparative Example 1 in which the entire amount of the adhesive required for molding was sprayed in the step A, an excessive amount of the adhesive adheres to the wood fiber with respect to the amount of the incombustible powder. When the non-combustible powder is charged in the step B, the non-combustible powder adheres to the adhesive in some places and hardens, so that the non-combustible powder adheres evenly and uniformly to the wood fiber cannot be obtained. In addition, since the adhesive is not applied to the surface of the non-combustible powder adhering to the wood fibers, it becomes impossible to form a state in which the non-combustible powder is entangled between the wood fibers and adheres to each other, resulting in poor molding when hot pressure is applied. (Cracks, peeling, etc.) occur, and even if molding is possible, it is not possible to manufacture a wood fiber board having uniform non-combustible performance especially in the length direction.

Next, Test 3 was conducted in order to confirm a suitable range between the amount of the adhesive sprayed in the step A and the amount of the adhesive sprayed in the step C. In Test 3, the amount of the adhesive sprayed in the step A was fixed at 27 g (about 3% with respect to the absolute dry weight of the wood fiber), while the amount of the adhesive sprayed in the step C was 27 g, 57 g, 84 g and 108 g (about 3% with respect to the absolute dry weight of the wood fiber). Except for changing to 4 ways of about 3%, about 6%, about 9% and about 12%, respectively, with respect to the absolute dry weight of the wood fiber, it was carried out under the same conditions as in Test 2 and there was no molding defect. Was visually observed. Table 3 shows these conditions and results.

As described above, the purpose of spraying the adhesive in step A is to adhere the adhesive evenly and evenly over the entire wood fiber, and the adhesive is 3% or more of the absolute dry weight of the wood fiber. By spraying, the adhesive adheres evenly and evenly to the wood fibers, so that the entire amount of the incombustible powder mixed in the next step B can be adhered to the wood fibers via the adhesive, resulting in molding defects. It is possible to produce a wood fiber board having uniform non-combustible performance without causing the above. When the bottom of the blender was observed after performing step B in which the non-combustible powder was mixed, in each of Examples 6 to 9, the non-combustible powder hardly fell to the bottom. This indicates that the entire amount of the incombustible powder mixed in the step B adhered to the wood fiber via the adhesive sprayed in the step A. In Test 3, the spray amount of the adhesive in step A was fixed at 3%, but it was demonstrated in Examples 6 to 9 in which the spray amount was set to 3%, so that more molding defects were observed. It is clear that the same effect is exhibited as the amount of spray.

Considering the results of Comparative Example 4 (Table 2) in which step A was omitted (that is, the amount of adhesive sprayed in step A was 0), the amount of adhesive sprayed in step A was less than 3%. The adhesive could not be evenly and evenly adhered to the wood fibers, and some of the non-combustible powder mixed in step B could not adhere to the wood fibers and soared up by stirring or dropped to the bottom of the blender. Therefore, molding defects such as so-called punctures are likely to occur, and even if molding is possible, it becomes difficult to manufacture a wood fiber board having uniform non-combustible performance as a whole.

As described above, one purpose of spraying the adhesive in the step C is to apply the adhesive to the surface of the non-combustible powder adhered to the wood fiber through the steps A and B, and from this viewpoint, the adhesive is applied. It was demonstrated from the results in Table 3 that it is preferable to use a spray amount of 3% or more with respect to the absolute dry weight of the wood fiber.

Considering the results of Comparative Example 3 (Table 2) in which step C is omitted (that is, the amount of adhesive sprayed in step C is 0), the amount of adhesive sprayed in step C is less than 3%. Even if the non-combustible powder can be evenly and uniformly adhered to the wood fiber through the steps A and B, the adhesive cannot be adhered to the surface of all the non-combustible powder in the step C, and the non-combustible powder cannot be adhered. Since the powder cannot form a state in which the wood fibers are entangled with each other and adhered to each other, it causes molding defects such as cracks and peeling.

Another purpose of the amount of the adhesive sprayed in the step C is to make up for the shortage of the adhesive sprayed in the step A and to apply the adhesive necessary for molding into the wood fiber board, so that the amount is 3%. In addition, the total amount with the spray amount of the adhesive in the step A is set to be the required molding amount, and this total amount is 6 to 35% with respect to the absolute dry weight of the wood fiber. Is preferable. Within this range, it is possible to manufacture a wood fiber board having non-combustible performance without causing molding defects. If the total amount of the adhesive is less than 6%, it becomes difficult for the adhesive to spread over the entire wood fiber, and a portion where the wood fiber is not adhered to each other is generated, which may cause molding failure. If the total amount of the adhesive exceeds 35%, the amount of water contained in the adhesive becomes excessive, and it takes a long time to cure the adhesive at the time of thermal pressure, resulting in a decrease in production efficiency. In addition, the moisture contained in the adhesive becomes high temperature and high pressure at the time of hot pressure, becomes steam in the compressed wood fiber and expands, and molding defects such as cracks and peeling are likely to occur.

From the test results and discussion described above, the spray amount of the adhesive in step A is 3 to 32% with respect to the absolute dry weight of the wood fiber, and the spray amount of the adhesive in step C is the absolute dry weight of the wood fiber. It is considered that 32 to 3% is a preferable range.

Although the present invention has been described in detail above based on the illustrated embodiment, the present invention is not limited to this, and is variously modified or modified within the scope of the invention interpreted based on the description of the claims. It is feasible. In FIG. 1, steps A (c), B (d) and C (e) are performed in the same blender 11, but different blenders may be used and the wood fiber 10 or the wood fiber 10 is adhered to the same. These steps may be performed while the wood fibers 10a and 10b to which the agent and the like are attached are blown by a duct or the like.

10 Wood fiber 10a Wood fiber with adhesive (part) 10b Wood fiber with adhesive (part) and non-combustible powder 10c Wood fiber with adhesive (total amount) and wood fiber with non-combustible powder 11 Blender 12 Spray 13a Total amount of adhesive required for molding 13b Total amount of adhesive required for molding 14 Chemical injection device 15 Powdery water-insoluble non-combustible agent 16 Spray 17 Upper heat plate 18 Lower heat plate 19 Water-insoluble non-combustible agent Wood fiber board containing (non-combustible powder) 20 An aqueous solution of a water-soluble non-combustible agent (non-combustible solution)
21 Pressure-reduced pressure impregnator 22 Wood fiber board containing water-insoluble non-combustible agent and water-soluble non-combustible agent

Claims (4)

The first step of hot-press molding a mixture of wood fibers mixed with an adhesive and a water-insoluble non-combustible agent to form a wood fiber board, and the wood fiber board obtained by the first step are immersed in an aqueous solution of a water-soluble non-combustible agent. A method for producing a non-combustible wood fiber board, which comprises sequentially performing a second step of impregnation. In the first step, a water-insoluble incombustible agent is mixed with the step A in which a part of the entire amount of the adhesive required for molding is sprayed on the wood fiber to adhere the adhesive to the wood fiber, and the mixture obtained in the step A is mixed. In step B, where the water-insoluble non-combustible agent is attached to the wood fiber via an adhesive, and the mixture obtained in step B, the balance of the entire amount of the adhesive required for molding is sprayed on the wood fiber, the adhesive, and the water-insoluble non-combustible. The non-combustible wood fiber according to claim 1, wherein a step C for obtaining a mixture composed of a chemical and a step D for producing a wood fiber board by hot-press molding the mixture obtained in the step C are sequentially performed. How to make a board. The second aspect of claim 2, wherein the step A sprays the required amount of the adhesive in an amount of 10 to 90% by weight, and the step C sprays the required amount of the adhesive in an amount of 90 to 10% by weight. Manufacturing method of non-combustible wood fiber board. The step A is characterized by spraying an adhesive of 3% or more with respect to the absolute dry weight of the wood fiber, and the step C is characterized by spraying an adhesive of 3% or more with respect to the absolute dry weight of the wood fiber. , The method for producing a non-combustible wood fiber board according to claim 2 or 3.

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