CN1654180A - A method for manufacturing glue-free fiberboard by closed hot pressing process - Google Patents

Abstract

The present invention is sealed hot pressing technological process of producing no-glue fiber board with wood, bamboo or herbaceous plant as material, and solves the technological problems of lowering hot press pressure and expanding the product thickness and density range. The technological process includes the steps of: separating the material into wet fiber and applying paraffin emulsion; drying and spreading; pre-pressing; sealed and heated pressing the board blank inside sealing frame in a hot press to form the no-glue fiber board. The hot pressing step consists of hydrolysis section, air exhausting section and plasticizing section, and the sealing frame is heat resistant and airtight and in the shape of formed board.

Description

A method for manufacturing glue-free fiberboard by closed hot pressing process

technical field

The invention relates to the field of producing glue-free fiberboards using wood (bamboo) or herbaceous plants as raw materials, in particular to a method for manufacturing glue-free fiberboards by a closed hot pressing process.

Background technique

Chinese patent document CN1108988A discloses "a production method of dry-process glue-free hard fiberboard", which separates and dries plant raw materials, forms them under the condition of not applying synthetic resin, and hot-presses them to obtain a wood-based panel. From the examples of this patent, this technology is only suitable for the manufacture of dry-process adhesive-free hard fiberboard (the board density is basically greater than 1.0g/cm ³ ), and cannot be used in the production of dry-process adhesive-free medium density fiberboard (The density of medium density fiberboard ranges from 0.45 to 0.88 g/cm ³ ). The standard adopted by this technology is the national standard "Hard Fiberboard" (GB12626.2-90). This standard does not involve indicators such as plane tensile strength, water absorption thickness expansion rate, elastic modulus, etc., so it is impossible to fully understand the relevant physical properties of the product. mechanical properties. According to the national standard "Hard Fiberboard" (GB12626.2-90), the maximum nominal size of the hard fiberboard thickness is 5 mm, and the maximum thickness listed in the production example described in the patent specification is 5.7 mm. Therefore, using this technology to produce glue-free boards, the specifications of the products are relatively limited. In addition, in the hot pressing process of this patented technology, the preferred value of high pressure is 5-5.4MPa, and 5.4-6.3MPa is used in the production example. If the heat press is used for a long time under such a high heat pressure, it is easy to cause problems such as deformation of the pressure plate and leakage of the hydraulic oil circuit system, thereby shortening the service life of the heat press. The board forming mechanism of this technology, from the process point of view, relies on high temperature and high pressure to make the fibers form boards mainly in the form of physical combination (such as van der Waals force). This patented technology has not yet been applied to actual production due to the existence of some of the above-mentioned deficiencies.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for manufacturing glue-free fiberboard with low hot pressing pressure and wide range of product thickness and density.

The method for manufacturing the glue-free fiberboard by the airtight hot pressing process of the present invention is characterized in that:

1) Fiber separation, adding water repellent: separating the plant material into wet fibers, and applying a water repellant paraffin emulsion of 0.5 to 1.5% of the absolute dry fiber mass of the raw material, preferably 0.8 to 1.0%;

2) Drying and paving: heat and dry the wet fibers to a moisture content of 14-22%, preferably 16-18%, and pave the fibers according to the conventional production process of medium density fiberboard;

3) Pre-pressing: pre-pressing the dried and paved fibers according to the conventional process of medium density fiberboard production to obtain a shaped slab;

4) Airtight hot pressing: the formed slab is placed on a hot press equipped with an airtight frame for hot pressing to obtain a glue-free fiberboard; the hot pressing process is composed of a hydrolysis section, an exhaust section, and a plasticizing section, wherein the hydrolysis section , Exhaust section, and plasticizing section have the same hot-pressing temperature, all of which are 170-220°C; hot-pressing pressure, hydrolysis section and plasticizing section are 2.0-3.5MPa, and the middle exhaust section is 0.5-1.0MPa; hot-pressing time , the hydrolysis section is 10-20 s/mm, the exhaust section and the plasticizing section are 10-15 s/mm; the closed frame is a high-temperature-resistant, air-tight material closed frame, and the shape of the frame is compatible with the formed slab. The final thickness of the frame is consistent with the thickness gauge.

Preferably, the hot-pressing temperature is 200-210°C; the hot-pressing pressure is 2.5-3.5 MPa in the hydrolysis section and the plasticizing section, 0.5-0.8 MPa in the middle exhaust section, and the hot-pressing time is 35-40 s/mm .

The hot-pressing time of each stage is different according to the change of other conditions, so as to optimize the process of each stage of airtight hot-pressing and save energy. The total time of hot pressing is 30-45 s/mm, preferably 35-40 s/mm.

Studies have shown that the closed hot pressing process consists of a hydrolysis section, an exhaust section, and a plasticizing section. In the hydrolysis section, after the hot press is closed, the slab is in the airtight chamber formed by the upper and lower hot pressing plates and the airtight frame. Due to the high moisture content of the slab and the close contact with the upper and lower hot pressing plates at high temperature, the moisture in the slab is quickly vaporized to form high-pressure water vapor. Some hemicelluloses that make up the board plant fibers are hydrolyzed into monosaccharides in high-pressure steam, and some lignin in plant fibers are degraded and hydrolyzed into low-molecular-weight lignin and lignin products after high-pressure steam treatment. If apply inorganic acid catalyst (at this time, the moisture content of the dried fiber is controlled at 10-12% after the drying process and before the pre-press molding, the catalyst (solute) addition amount is 0.2-1.5% of the absolute dry mass of the raw material, preferably 0.3-0.6%, the final moisture content of the fiber is 14-22%, and the preferred moisture content is 16-18%). Under the action of the catalyst, the degradation and hydrolysis speed of hemicellulose and lignin will be faster, which is beneficial to shorten the hot pressing cycle. After the completion of the hydrolysis section, the pressure is reduced and enters the exhaust section for exhaust, and after the exhaust is completed, the pressure is increased and enters the plasticizing section. In the plasticizing section, under hot pressing, the monosaccharide is heated to remove the combined water of three water molecules in the monosaccharide, which becomes furfural; furfural reacts with low molecular weight lignin and lignin products to form a phenol-based synthetic adhesive, and Bonded to form glueless fiberboard.

The airtight frame is resistant to high temperature and airtight, and the material can be metal, wood, paper products (such as cardboard, laminated paper), etc.; the thickness of the frame depends on the material. The flexible strip (such as paper products, wood veneers, etc.) that functions as a seal under pressure has the same final thickness as the thickness gauge after hot pressing, which replaces the function of the thickness gauge accordingly. The thickness of the non-metallic material, the original thickness (can be obtained through experiments) is slightly higher than the thickness gauge, and the final thickness after hot pressing is consistent with the thickness gauge.

The invention has the advantages of small equipment technological innovation, good effect, low hot pressing pressure, and can produce products with thicker thickness and lower density.

Description of drawings

Fig. 1 is a schematic diagram of the hot pressing curve of the method of the present invention.

Detailed ways

The technical solutions of the present invention will be further specifically described below through examples.

Embodiment 1: In this example, the method for manufacturing glue-free high-density fiberboard with a closed hot pressing process is:

Using wood as raw material, glue-free high-density fiberboard is produced on the existing medium-density fiberboard production line.

1) Fiber separation, adding waterproofing agent: Chip the wood on a chipper, perform fiber separation according to the production process of MDF, and apply paraffin waterproofing agent, the amount of which is 0.8% of the dry fiber mass.

2) Drying and paving: the hot-milled fibers are dried by pipeline air-flow drying method, and the moisture content is controlled at 18%;

3) Pre-pressing: the process is the same as that in the existing medium density fiberboard production.

4) Airtight hot pressing: send the pre-pressed slab into the airtight frame (rectangular shape made of steel with a thickness of 6.0mm and a rectangular cross-sectional shape, the airtight frame is fixed on the upper hot pressing plate, and the airtight frame below Paste the flexible strip of paper products to perform hot pressing on the hot press in the closed state of the hot press), and the hot pressing process is composed of a hydrolysis section, an exhaust section, and a plasticizing section (see Figure 1). The pressure in the hydrolysis section and the plasticizing section are 3.5 MPa, the pressure in the exhaust section is 0.8 MPa; the hot pressing temperature is 200 ° C; the hot pressing time is 2.0 minutes for the hydrolysis section, 1.0 minutes for the exhaust section, and 1.0 minutes for the plasticizing section The time is 1.0 points.

5) Trimming and sanding: The hot-pressed raw board is cut vertically and horizontally and sanded (the thickness of the raw board is 6.1mm), and then inspection and grading are carried out and the finished product is put into storage.

The thickness of the product is 6mm, the density is 1.03g/cm ³ , the static bending strength is 54.55MPa, the elastic modulus is 4280MPa, the plane tensile strength is 0.68MPa, and the water absorption thickness expansion rate is 13.5%.

The performance of the product meets the physical and mechanical performance index standard of indoor type board stipulated in the medium density fiberboard standard (GB/T11718-1999).

Embodiment 1～12 and 13～24, see table 1 and table 2 to list respectively under different production process conditions, the physical mechanics of wood (bamboo) wood glue-free high-density fiberboard and wood (bamboo) wood glue-free medium-density fiberboard The performance list shows that its product performance has reached the physical and mechanical performance index standard of indoor type board stipulated in the medium density fiberboard standard (GB/T11718-1999).

Examples 25-34, 35-45 and 46-48, see Table 3, Table 4 and Table 5 respectively list the physical and mechanical properties of rice straw glue-free high-density fiberboard and wheat straw glue-free high-density fiberboard under different production process conditions A list and a list of physical and mechanical properties of wheat straw glue-free high-density fiberboard with H ₂ SO ₄ as a catalyst, and its product performance meets the physical and mechanical performance index standard of indoor type panels stipulated in the medium density fiberboard standard (GB/T11718-1999).

Table 1 List of physical and mechanical properties of wood (bamboo) wood (bamboo) glue-free high-density fiberboard under different production process conditions

Example raw material HCL applied amount/% Plate thickness/mm Fiber moisture content% Amount of paraffin applied/%                                                Physical and mechanical properties temperature/℃ Pressure/MPa time/min Density/g.cm ³ Static Bending Strength/MPa Elastic modulus/MPa Plane tensile strength/MPa Water absorption thickness swelling rate/% 1 wood 0 6 18 0.8 200 3.5-0.8-3.5 2.0-1.0-1.0 1.03 54.5 4280 0.68 13.5 2 wood 0 6 14 0.5 170 3.5-0.5-3.5 2.0-1.0-1.5 1.05 35.5 3745 0.56 20.5 3 wood 0 6 16 1.0 190 3.0-0.5-3.0 2.0-1.0-1.0 1.03 52.3 4216 0.66 12.1 4 wood 0 6 twenty two 1.5 210 2.0-0.5-2.0 1.5-1.5-1.0 1.03 39.6 3864 0.58 12.2 5 wood 0 6 19 0.9 220 2.5-1.0-2.5 1.5-1.25-1.25 1.04 53.2 4195 0.62 11.2 6 wood 0.4 9 18 0.8 200 3.5-0.5-3.5 2.5-2.0-1.5 1.12 56.5 4612 0.70 13.8 7 wood 0.5 9 18 0.8 200 3.5-0.5-3.5 1.75-2.0-1.5 1.09 58.5 4812 0.72 13.5 8 wood 0.6 9 18 0.8 200 3.5-0.5-3.5 1.5-2.0-1.5 1.10 49.5 4325 0.68 13.6 9 wood 0.8 9 18 0.8 200 3.5-0.5-3.5 1.5-2.0-1.5 1.12 45.2 4028 0.57 12.1 10 wood 1.0 9 18 0.8 200 3.5-0.5-3.5 1.5-2.0-1.5 1.13 35.2 3872 0.55 10.2 11 wood 0.5 12 18 0.8 200 3.5-0.5-3.5 3.5-2.0-2.5 1.10 58.2 4632 0.56 11.5 12 Bamboo 0.5 12 18 0.8 200 3.5-0.5-3.5 3.5-2.0-2.5 1.12 60.5 4895 0.57 11.2

Remarks: The water content of the test piece in the table is 4-13%. The hot pressing pressure value successively represents the pressure of the hydrolysis section, the exhaust section pressure, and the plasticizing section pressure; the hot pressing time value successively indicates the hydrolysis section time, exhaust section time, plasticizing time.

Table 2 List of physical and mechanical properties of wood (bamboo) wood (bamboo) glue-free MDF under different production process conditions

Example raw material HCL applied amount/% Plate thickness/mm Fiber moisture content% Amount of paraffin applied/%                                                                 Physical and Mechanical Properties temperature/℃ Pressure/MPa time/min Density/g.cm ³ Static Bending Strength/MPa Elastic modulus/MPa Plane tensile strength/MPa Water absorption thickness swelling rate/% 13 wood 0 6 14 0.5 170 3.5-0.5-3.5 2.0-1.0-1.5 0.85 23.5 2750 0.55 18.6 14 wood 0 6 16 1.0 190 3.0-0.5-3.0 1.5-1.5-1.0 0.86 28.2 2800 0.56 12.3 15 wood 0 6 18 0.8 200 3.5-0.8-3.5 2.0-1.0-1.0 0.85 30.3 3210 0.58 14.2 16 wood 0 6 twenty two 1.5 210 2.0-0.5-2.0 1.5-1.5-1.0 0.85 23.6 2756 0.55 12.8 17 wood 0 6 19 0.9 220 2.5-1.0-2.5 1.5-1.25-1.25 0.87 30.0 2980 0.57 12.5 18 wood 0.4 9 18 0.8 200 3.5 0.5-3.5 2.5-2.0-1.5 0.86 30.5 2900 0.56 14.5 19 wood 0.5 9 18 0.8 200 3.5-0.5-3.5 1.75-2.0-1.5 0.87 32.6 3050 0.57 13.9 20 wood 0.6 9 18 0.8 200 3.5-0.5-3.5 1.5-2.0-1.5 0.85 28.8 2850 0.56 13.6 twenty one wood 0.8 9 18 0.8 200 3.5-0.5-3.5 1.5-2.0-1.5 0.86 25.2 2765 0.55 12.9 twenty two wood 1.0 9 18 0.8 200 3.5-0.5-3.5 1.5-2.0-1.5 0.85 23.5 2750 0.55 12.2 twenty three wood 0.5 12 18 0.8 200 3.5-0.5-3.5 3.5-2.0-2.5 0.87 29.7 3120 0.59 13.5 twenty four Bamboo 0.5 12 18 0.8 200 3.5-0.5-3.5 3.5-2.0-2.5 0.88 35.6 3269 0.66 14.2

Remarks: The moisture content of the test piece in the table is 4-13%. The hot pressing pressure value successively indicates the pressure of hydrolysis section, exhaust section pressure and plasticizing section pressure; the hot pressing time value successively indicates the time of hydrolysis section, exhaust section time, plasticizing time.

Table 3 List of physical and mechanical properties of straw-free high-density fiberboard under different production process conditions

Example raw material HCL application amount/ Plate thickness/mm Fiber moisture content% Amount of paraffin applied/%                                                     Physical and Mechanical Properties temperature/℃ Pressure/MPa time/min Density/g.cm ³ Static Bending Strength/MPa Elastic modulus/MPa Plane tensile strength/MPa Water absorption thickness swelling rate/% 25 straw 0 6 14 0.5 170 3.5-0.5-3.5 2.0-1.0-1.5 0.85 23.5 2750 0.55 20.6 26 straw 0 6 16 1.0 190 3.0-0.5-3.0 1.5-1.5-1.0 0.86 28.2 2800 0.56 12.3 27 straw 0 6 18 0.8 200 3.5-0.8-3.5 2.0-1.0-1.0 0.85 30.3 3210 0.58 14.2 28 straw 0 6 twenty two 1.5 210 2.0-0.5-2.0 1.5-1.5-1.0 0.85 23.6 2756 0.55 12.8

29 straw 0 6 19 0.9 220 2.5-1.0-2.5 1.5-1.25-1.25 0.87 30.0 2980 0.57 12.5 30 straw 0.4 6 18 0.8 200 3.5-0.5-3.5 1.5-1.0-1.5 0.86 32.5 3325 0.62 13.6 31 straw 0.5 6 18 0.8 200 3.0-0.5-3.0 1.5-1.0-1.5 0.88 34.6 3460 0.65 12.5 32 straw 0.6 6 18 0.8 200 3.5-0.8-3.5 1.5-1.0-1.5 0.85 34.5 3280 0.57 12.0 33 straw 0.8 6 18 0.8 200 2.5-1.0-2.5 1.5-1.0-1.5 0.85 29.2 2900 0.56 10.2 34 straw 1.0 6 18 0.8 200 2.0-0.5-2.0 1.5-1.0-1.5 0.87 25.6 2750 0.55 12.1

Remarks: The moisture content of the test piece in the table is 4-13%, and the hot pressing pressure value successively represents the pressure of hydrolysis section, exhaust section pressure, and plasticizing section pressure; the hot pressing time value successively indicates the time of hydrolysis section, exhaust section time, plasticizing time.

Table 4 List of physical and mechanical properties of wheat straw glue-free high-density fiberboard under different production process conditions

Example raw material HCL application amount/% Plate thickness/mm Fiber moisture content% Amount of paraffin applied/%                                                             Physical and Mechanical Properties temperature/℃ Pressure/MPa time/min Density/g.cm ³ Static Bending Strength/MPa Elastic modulus/MPa Plane tensile strength/MPa Water absorption thickness swelling rate/% 35 wheat straw 0 6 14 0.5 170 3.5-0.5-3.5 2.0-1.0-1.5 0.88 28.6 2930 0.56 22.5 36 wheat straw 0 6 16 1.0 190 3.0-0.5-3.0 1.5-1.5-1.0 0.86 30.2 3200 0.58 12.6 37 wheat straw 0 6 18 0.8 200 3.5-0.8-3.5 2.0-1.0-1.0 0.86 32.4 3280 0.58 14.5 38 wheat straw 0 6 twenty two 1.5 210 2.0-0.5-2.0 1.5-1.5-1.0 0.87 26.6 2736 0.55 11.6 39 wheat straw 0 6 19 0.9 220 2.5-1.0-2.5 1.5-1.25-1.25 0.87 25.0 2880 0.56 12.5 40 wheat straw 0.4 6 18 0.8 200 3.5-0.5-3.5 1.5-1.0-1.5 0.86 33.2 3216 0.60 13.9 41 wheat straw 0.5 6 18 0.8 200 3.0-0.5-3.0 1.5-1.0-1.5 0.85 35.3 3356 0.62 12.8 42 wheat straw 0.6 6 18 0.8 200 3.5-0.8-3.5 1.5-1.0-1.5 0.87 30.2 3189 0.58 12.5 43 wheat straw 0.8 6 18 0.8 200 2.5-1.0-2.5 1.5-1.0-1.5 0.86 27.6 3023 0.56 11.5 44 wheat straw 1.0 6 18 0.8 200 2.0-0.5-2.0 1.5-1.0-1.5 0.88 24.8 2800 0.57 10.6 45 wheat straw 1.5 6 18 0.8 200 2.0-0.5-2.0 1.0-1.0-1.0 0.87 25.8 2908 0.58 10.8

Remarks: The water content of the test piece in the table is 4-13%. The hot pressing pressure value successively represents the pressure of the hydrolysis section, the exhaust section pressure, and the plasticizing section pressure; the hot pressing time value successively indicates the hydrolysis section time, exhaust section time, plasticizing time.

Table 5 list of physical and mechanical properties of wheat straw glue-free high-density fiberboard with H ₂ SO ₄ as catalyst

Example raw material Amount of sulfuric acid applied/% Plate thickness/mm Fiber moisture content%  Amount of paraffin applied/%                                                               Physical and Mechanical Properties temperature/℃ Pressure/MPa time/min Density/g.cm ³ Static Bending Strength/MPa Elastic modulus/MPa Plane tensile strength/Mpa  Water absorption thickness expansion rate/% 46 wheat straw 0.2 6 18 0.8 200 2.5-1.0-2.5 1.5-1.0-1.5 0.88 23.5 2795 0.55 13. 47 wheat straw 0.3 6 18 0.8 200 2.0-0.5-2.0 1.5-1.0-1.5 0.86 25.8 2900 0.58 11.5 48 wheat straw 0.5 6 18 0.8 200 2.0-0.5-2.0 1.0-1.0-1.0 0.87 25.5 2908 0.57 11.2

Remarks: The water content of the test piece in the table is 4-13%. The hot pressing pressure value successively represents the pressure of the hydrolysis section, the exhaust section pressure, and the plasticizing section pressure; the hot pressing time value successively indicates the hydrolysis section time, exhaust section time, plasticizing time.

Claims (10)

1, a kind of method of manufacturing glue-less fiber board by leak-free type hot pressing technology is characterized in that:

1) fiber separation, add waterproofing agent: plant material is separated into wet fiber, and apply raw material bone dry fiber quality 0.5～1.5% the amount the waterproofing agent paraffin wax emulsions;

2) dry, mat formation: the wet fiber heat drying to moisture content 14～22%, and is mated formation fiber by the common process of medium density fibre board (MDF) production;

3) precompressed: drying, the fiber of mating formation are produced the common process precompressed by medium density fibre board (MDF) get shaping slab;

4) airtight hot pressing: shaping slab is placed on carries out hot pressing on the hot press that airtight frame is housed and get non-glue fibre board; Described hot pressing is made up of hydrolysis section, steam discharge section, fluxing zone, and wherein the hot pressing temperature of hydrolysis section, steam discharge section, fluxing zone is identical, is 170～220 ℃; Hot pressing pressure, hydrolysis section and fluxing zone are 2.0～3.5MPa, and the intermediate exhaust section is 0.5～1.0MPa; Hot pressing time, hydrolysis section are 10～20s/mm, and exhaust section and fluxing zone are 10～15s/mm; Described airtight frame is a sealing frame high temperature resistant, airtight material, and the shape and the shaping slab of frame adapt, and the final thickness of frame is consistent with finger gauge.

2, the method for manufacturing non-glue fibre board according to claim 1 is characterized in that adding behind the drying process concentration and is 15～25% inorganic acid as catalyst, and the catalyst addition is 0.2～1.5% of a raw material over dry quality.

3, the method for manufacturing non-glue fibre board according to claim 2 is characterized in that described inorganic acid (solute) addition is 0.3～0.6% of a raw material over dry quality.

4,, it is characterized in that described waterproofing agent paraffin wax emulsions applied amount is 0.8～1.0% of a raw material over dry quality according to the method for claim 1 or 2 or 3 described manufacturing non-glue fibre boards.

5,, it is characterized in that described mat moisture content is 16～18% according to the method for claim 1 or 2 or 3 described manufacturing non-glue fibre boards.

6, the method for manufacturing non-glue fibre board according to claim 4 is characterized in that described mat moisture content is 16～18%.

7, according to the method for claim 1 or 2 or 3 described manufacturing non-glue fibre boards, it is characterized in that described hot pressing temperature is 200～210 ℃, hot pressing pressure, hydrolysis section and fluxing zone are 2.5～3.5MPa, the intermediate exhaust section is 0.5～0.8MPa, and hot pressing time is 35～40s/mm.

8, the method for manufacturing non-glue fibre board according to claim 4, it is characterized in that described hot pressing temperature is 200～210 ℃, hot pressing pressure, hydrolysis section and fluxing zone are 2.5～3.5MPa, the intermediate exhaust section is 0.5～0.8MPa, and hot pressing time is 35～40s/mm.

9, the method for manufacturing non-glue fibre board according to claim 5, it is characterized in that described hot pressing temperature is 200～210 ℃, hot pressing pressure, hydrolysis section and fluxing zone are 2.5～3.5MPa, the intermediate exhaust section is 0.5～0.8MPa, and hot pressing time is 35～40s/mm.

10, the method for manufacturing non-glue fibre board according to claim 6, it is characterized in that described hot pressing temperature is 200～210 ℃, hot pressing pressure, hydrolysis section and fluxing zone are 2.5～3.5MPa, the intermediate exhaust section is 0.5～0.8MPa, and hot pressing time is 35～40s/mm.

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