JP2013151111A - Method for manufacturing fiberboard - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a fiberboard, configured to prevent rupture of the fiberboard, and to effectively manufacture the fiberboard at a high yield.SOLUTION: In a fiberboard manufacturing method of kneading lignocellulose fiber and an adhesive and heating/pressurizing it, a forming pressure Pin an initial stage of heating/pressurizing operation is made higher, for a predetermined time, than a forming pressure Pin subsequent heating/pressurizing operation. It is preferable that tis 5-100 seconds, Pis 3-10 Mpa, and P-Pis 7-90 Mpa.

Description

  The present invention relates to a method for producing a fiberboard by kneading lignocellulosic fibers and an adhesive and heating and pressing them.

  Patent Documents 1 to 4 and the like describe a method of kneading lignocellulosic fibers such as bagasse and kenaf and an adhesive, and heating and pressing to produce a fiberboard.

  In Patent Documents 1 to 3, in the process of heating and pressurizing the fiber kneaded with the adhesive, the pressure is constant throughout the heating and pressurizing process. In Patent Document 4, after over-pressing in the initial stage of the heating and pressurizing process, the hot platen is immediately raised to return to a predetermined molding pressure, and heated and pressed for a predetermined time with this molding pressure to obtain a fiber having a high surface hardness. The production of plates is described.

JP-A-11-333986 JP 2000-263519 A JP 2002-69417 A JP-A-6-339904

  When kneading the lignocellulose fiber and adhesive and making it into a mat shape and heating and pressing it to produce a fiberboard, if the molding pressure applied during heating and pressing is constant, the effect of moisture remaining in the mat After heating and pressurizing with a heating and pressurizing apparatus, the fiberboard may burst as soon as the mold is opened and the applied pressure is lost. By increasing the molding pressure, this rupture phenomenon can be prevented and the surface properties of the resulting fiberboard can be improved. However, if the molding pressure is increased through the heating and pressing process, the resulting fiberboard has a high density. It will be a thing.

  If the molding pressure is set to the normal molding pressure and the heating and pressing time is lengthened significantly, it is surmised that the moisture is sufficiently removed in the heating and pressing process, and the bursting phenomenon is prevented. The production efficiency of the plate is lowered and the production cost is increased. Although it is conceivable to increase the temperature at the time of heating and pressurization in order to sufficiently remove moisture in the heating and pressing step, the adhesive is thermally decomposed and the strength of the fiberboard is lowered.

  An object of the present invention is to provide a fiberboard manufacturing method that can prevent the fiberboard from being ruptured due to such moisture and can efficiently manufacture a fiberboard having an appropriate density at a high yield. .

Method for producing a fiber board of the present invention, after kneading the lignocellulosic fibers and adhesive, a process for the preparation of heat under pressure fiberboard, the molding pressure P ₁ for a predetermined time early in the heating and pressing, then is characterized in that a high molding pressure than molding pressure P ₂ of the heating and pressing. Preferably, the molding pressure _{P 2} is _3~10MPa, P 1 -P ₂ is 7～90MPa. The predetermined time is preferably 5 to 100 seconds.

  Bagasse is preferred as the lignocellulose fiber.

  In the fiberboard manufacturing method of the present invention, a molding pressure higher than the molding pressure at the time of steady heating and pressurization is applied for a predetermined time at the initial stage of the step of heating and pressurizing the mat-like material of lignocellulose fiber to which an adhesive is adhered. . As a result, heat is sufficiently transferred from the hot press board to the center part in the thickness direction of the mat-like material being heated and pressed (hereinafter, simply referred to as “center part”), and the adhesive in the center part is also sufficiently sufficient. And the strength at the center of the fiberboard becomes high. For this reason, when a fiber board is taken out from between hot press boards, it is prevented that a fiber board bursts, and the manufacture yield of a fiber board becomes high. Moreover, since the burst of the fiberboard obtained even if it does not make time of a heating-pressing process longer than usual is prevented, manufacturing efficiency improves. Furthermore, by heating and pressing the mat-like material at a high molding pressure for a predetermined time only at the initial stage of heating and pressing, the surface properties of the fiber board are improved and the density of the fiber board is prevented from becoming excessively high. Is done.

It is a molding pressure chart of the heating-pressing process of the manufacturing method of the fiber board of this invention. It is a shaping | molding pressure chart of the heating-pressing process of the manufacturing method of the conventional fiber board.

  Hereinafter, the present invention will be described in more detail.

  In the fiberboard manufacturing method of the present invention, lignocellulosic fibers and an adhesive are kneaded to form a mat-like material, and then heated and pressurized.

  The lignocellulose fiber is not particularly limited as long as its main components are cellulose, hemicellulose and lignin, and examples thereof include fibers obtained from palm, hemp, sugar cane, kenaf, bamboo, rice and the like. The present invention is particularly suitable when bagasse obtained from sugar cane is used, but is not limited thereto. The length of lignocellulose fiber is preferably about 2 to 30 mm, particularly about 3 to 20 mm, but is not limited thereto. In addition, a relatively long lignocellulose fiber may be distributed at the center of the mat-like material, and a relatively short lignocellulose fiber may be distributed on the surface layer side, or the fiber lengths as a whole may be equal. .

  As the adhesive, various thermosetting resins such as urea resin, melamine resin, urea melamine resin, phenol resin, resorcinol resin, epoxy resin, urethane resin, furfural resin, isocyanate resin are used. can do. As the adhesive, F ☆☆☆☆ (F Forster) is particularly preferable because it is less harmful to the human body.

  The amount of the adhesive added to the fiber is preferably about 2 to 40 parts by weight, particularly about 5 to 30 parts by weight, based on 100 parts by weight of the fiber, as the solid weight of the adhesive.

  In order to knead the adhesive and the fiber, it is preferable to stir and knead the aqueous solution or dispersion of the adhesive while spraying on the fiber, but also by a method using a mixer, a mixer, a stirrer, a kneader or the like. Good.

  The moisture content of the fiber when the adhesive is added to the fiber is preferably 30% or less, particularly about 2 to 15% by weight.

  In the present invention, additives such as a water repellent, an antifungal agent, a curing agent, a mold release agent, an antiseptic, and an anti-anticide may be added to the fiber in addition to the adhesive.

  It is possible to predry the fiber to which an adhesive or an additive is added if necessary at a temperature of 200 ° C. or less, for example, about 30 to 120 ° C., and adjust the water content to about 3 to 30% by weight, particularly about 5 to 20% by weight. preferable. After the fibers to which adhesives and the like have been attached in this way are accumulated to a predetermined thickness, the mat is preferably pre-pressed to form a pre-formed mat-like material, which is sandwiched by a hot press machine and heated and pressed to obtain a fiber board. And

In the present invention, the molding pressure is increased for a predetermined time at the initial stage of the heating and pressurization, and then the steady molding pressure is obtained. Examples of this time-dependent change pattern of the molding pressure are shown in FIGS. In FIG. 1A, a high molding pressure P ₁ is set for a predetermined time t _{1 at} the initial stage of heating and pressurization, and then a steady molding pressure P ₂ is applied.

In FIG. 1B, as in FIG. 1A, the high molding pressure P ₁ is set for a predetermined time t _{1 at} the initial stage of heating and pressurization, and then the steady molding pressure P ₂ is set. increased to the manner molding pressure P _3, it has a thickness of fiberboard so as to conform to the set value at high accuracy.

The total heating and pressing time t is preferably 30 to 500 seconds, particularly about 100 to 300 seconds, and the initial predetermined time t ₁ is preferably 5 to 100 seconds, particularly 5 to 40 seconds. For FIG. 1 (b), the slightly heated pressing time _{t 2} at high molding pressure is 2 to 100 seconds of the end, particularly about 5 to 60 seconds are preferred.

If t ₁ is shorter than 5 seconds, easily fibreboard ruptures when removed fiberboard from hot press platen. If t ₁ is longer than 100 seconds, there is a tendency that the peel strength of the fiberboard is reduced. The reason for this is not necessarily clear, but when heated and pressed for a long time at a high molding pressure, the fibers in the center of the compressed mat-like material in the thickness direction are firmly bound to the fibers on the surface layer side, and the molding pressure is reduced. Go to the surface layer side portion of the fibers in the vicinity of said center portion of the mat-like material when reduced to P ₂ is associated with the fibers of the surface layer side, or reduces the density of the mat Jobutsu central structural It is inferred that this is due to the partial generation of a low-strength portion that is fragile.

Molding pressure _{P 2} of the aforementioned constant is preferably about 3~100MPa particularly 4-8 MPa. Predetermined molding pressure _{P 1} of the initial above is preferably 7~90MPa particularly 15~70MPa higher than the steady molding pressure _{P 2.}

Final molding pressure _{P 3} in FIG. 1 (b) is preferably 2~50MPa particularly 5~40MPa higher than _{P 2.}

Incidentally, FIG. 1 (a), (b), the after heating and pressurization at molding pressure P ₁ initially, but immediately the molding pressure P _2, the molding pressure between P ₁ and P ₂ in this way it may be molding pressure P ₂ from the holding time required to. Although the temperature of the heating and pressing step depends on the type of the adhesive, it is usually preferably from 170 to 230 ° C, particularly from 180 to 220 ° C, particularly from about 190 to 220 ° C.

  Note that this temperature may be constant throughout the entire heating and pressurizing process, or may be changed within the above-mentioned preferred range.

  The fiberboard produced as described above is then cut into an appropriate size as necessary, and subjected to a finishing treatment such as a sanding treatment to obtain a fiberboard product.

  Hereinafter, examples and comparative examples will be described.

Experiment No. 1-11
As a fiber raw material, sugarcane squeezed bagasse (one having been defibrated to an average length of 7 mm) was dried to a moisture content of about 7%. A dispersion (solid content concentration: 60% by weight) in which urea melamine-based resin was dispersed in water as an adhesive was added by an air spray gun at a rate of 12 parts by weight as solids to 100 parts by weight of fibers. Further, 1.5 parts by weight of an emulsion wax as a water repellent was added to 100 parts by weight of the fiber, and 2 parts by weight of a curing agent (ammonium chloride) was added to 100 parts by weight of the adhesive. Thereafter, the additives were uniformly dispersed throughout the fiber by kneading.

Then, after drying at 100 ° C. so that the water content becomes 7%, this adhesive-added bagasse fiber is supplied to the forming process, spread and matted, and then in the preliminary pressing process. The mat was pressure clamped. A pre-pressed forming mat (300 mm × 300 mm × 80 mm) was heated and pressed in accordance with the pattern of FIG. Note that. No. No. ₁ was not subjected to the initial heating and pressurization at the molding pressure P1, and was heated and pressed in the pattern shown in FIG. The overall heating and pressing time t, initial heating and pressing time t ₁ , molding pressures P ₁ and P _2, and heating temperature T are as follows.

t = 210 seconds t ₁ = 0 to 100 seconds (as shown in Table 1)
P ₁ = 4 MPa
P ₂ = 1.6 MPa
T = 200 ° C

  The presence or absence of rupture when the heated and pressurized product was taken out from between the hot press panels and the peel strength according to JIS K 5908 were measured. The results are shown in Table 1.

No. in Table 1 As 5-10, by the t ₁ and 5 seconds or more, rupture of fiber board is prevented. However, t ₁ is the peel strength drops longer than 40 seconds. In addition, No. The thickness of the fiberboard produced by 3-10 was 13 mm.

Experiment No. 12-16
Except that the holding time t ₁ at the time of initial heating and pressurization was fixed at t ₁ = 5 seconds and the temperature T was T = 160, 180, 190, 220 or 240 ° C., the above experiment No. The experiment was conducted as the same as 3. The results are shown in Table 2.

  As shown in Table 2, when the temperature T at the time of heating and pressing is 160 ° C., the peel strength is insufficient. When temperature T becomes 190 degreeC or more, it is guessed that a furfural will generate | occur | produce from bagasse fiber, it will carry out a hardening reaction with a urea melamine adhesive, and an intensity | strength will improve. However, when the temperature T is 240 ° C. or higher, the adhesive is decomposed and the peel strength is reduced. In addition, No. The thickness of the fiberboard produced by 12-16 was 13 mm.

Experiment No. 17
Experiment No. 6 was the same except that the pressure pattern was as shown in FIG. Note that t ₂ = 20 seconds and P ₃ = 16 MPa. As a result, a fiber board having a thickness of 13 mm was obtained.

Claims (5)

In the method of manufacturing a fiberboard by kneading lignocellulose fibers and an adhesive and then heating and pressurizing, the molding pressure P ₁ is applied over a predetermined time at the initial stage of heating and pressurization, and the molding pressure P ₂ of the subsequent heating and pressurization is used. A method for producing a fiberboard, characterized by having a high molding pressure. According to claim 1, wherein a molding pressure _{P 2} is 3～10MPa, method for producing a fiberboard, which comprises a 7~90MPa difference _P 1 -P ₂ and the molding pressure _{P 1} and _{P 2.}   The method for manufacturing a fiberboard according to claim 1 or 2, wherein the predetermined time is 5 to 100 seconds.   The method for producing a fiberboard according to any one of claims 1 to 3, wherein the lignocellulose fiber is bagasse.   5. The method of manufacturing a fiber board according to claim 1, wherein the thickness of the fiber board is adjusted by increasing the molding pressure in the final step of the heating and pressurizing process.

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