The purpose of this invention is to provide a kind of hot-press method of producing composite plant fiber-cement board, do not need slab to be vacuumized and lead to CO
2Gas uses the ordinary hot press, just the hardening of cement time in the composite plant fiber-cement board of compacting can be shortened to about tens minutes, thereby reduces found the factory investment and product cost.Simultaneously can suppress thinner sheet material, the thinlyyest reach 4 millimeters, and can guarantee the thickness uniformity coefficient of product.
Technical scheme of the present invention is: a kind of hot-pressing production process of composite plant fiber-cement board, with the vegetable fibre is strongthener, with cement particularly silicate cement be tackiness agent, its processing step comprises the Mechanical Crushing of plant material and screening process, and to the making sheet raw material that mixes mat formation, hot pressing and aftertreatment, it is characterized in that
(1) composition of making sheet raw material and consumption are as follows:
A, vegetable fibre, its oven dry weight account for 15~30% of the vegetable fibre production board oven dry weight made;
B, calcium oxide or calcium hydroxide account for 4~10% of the vegetable fibre production board oven dry weight made;
C, calcium chloride or magnesium chloride, account for add 30~60% of calcium oxide or calcium hydroxide weight;
D, lime carbonate or sodium bicarbonate account for 7~13% of the vegetable fibre production board oven dry weight made;
E, water glass account for 4~10% of the vegetable fibre production board oven dry weight made;
F, Sodium Silicofluoride account for 10~15% of water glass weight;
G, cement account for 50~66% of the vegetable fibre production board oven dry weight made;
Water is as adding composition, and its add-on is 20~40% of the vegetable fibre production board oven dry weight made;
(2) mixing of making sheet raw material is finished by three stirrings, adds vegetable fibre, water, calcium oxide or calcium hydroxide, calcium chloride or magnesium chloride, lime carbonate or sodium bicarbonate, Sodium Silicofluoride when stirring for the first time in stirrer and stirs jointly 3~7 minutes; Add water glass when stirring for the second time, restir 2~6 minutes, wait the thick liquid that generated with the vegetable fibre parcel evenly after, stir for the third time; Before stirring for the third time, add an amount of cement, stirred through 4~6 minutes, even with the mixing of materials of preceding twice stirring;
(3) processing parameter during hot pressing is as follows:
Hot pressing temperature is 90~125 ℃;
Pressure is 2.0~3.5MPa;
Hot pressing time is determined by following experimental formula:
T=160 (t-80)
-1+ μ [α
-1+ (β+γ)
-1]+0.5 (δ+η-29)+ξ, in the formula,
T is a hot pressing time, minute being unit;
T is a temperature on the heating platen, value between 90~125 ℃;
μ is a vegetable fibre kind adjustment factor, and value between 21~30 is minute being unit;
α is the percentage ratio that lime carbonate or sodium bicarbonate account for the production board oven dry weight, is zero dimension;
β is the per-cent that calcium chloride or magnesium chloride account for the production board oven dry weight, is zero dimension;
γ is the per-cent that calcium oxide or calcium hydroxide account for the production board oven dry weight, is zero dimension;
δ is the per-cent that the water yield of adding accounts for the production board oven dry weight, is zero dimension;
η has considered that Total Water that the vegetable fibre moisture percentage calculates later on accounts for the per-cent of production board oven dry weight, is zero dimension;
ξ is the sheet metal thickness adjustment factor, and minute to be unit, when production board thickness was 4~8 millimeters, the ξ value was-1; When production board thickness was 9~18 millimeters, the ξ value was that the millimeter of production board actual (real) thickness subtracts 9; When production board thickness was 19~30 millimeters, the ξ value was 10;
(4) composite plant fiber-cement board after the hot pressing being placed on temperature is that 15~30 ℃, relative humidity are to carry out in 50~70% the environment after humidification handled 5~7 days, saws the limit again, the normal temperature maintenance is handled.
Advantage of the present invention is: shortened the setting time of cement composite board greatly than long period method, thereby saved a large amount of moulds, anchor clamps, backing plate and kiln, saved investment, shortened Production Flow Chart, reduced cost, improved quality product; Compare with external hot-press method,, simplify production process, prevent the pollution of the environment, reduce product cost guaranteeing to save a large amount of facility investments under the product quality premise.
Below the inventive method is elaborated.The inventive method can adopt yearly plant or perennial plant to make sheet material as plant fiber material, and yearly plant comprises: hemp stalk, cotton stalk, cornstalk, corn cob, sunflower stalk, sunflower plate, Sunflower shell, cigarette stalk, straw, reed, cogongrass stalk, bagasse, melon seedling, straw, rice husk, Pericarppium arachidis hypogaeae, hards, paddy stalk, sorghum stalk, beans stalk, kapok bits, Exocarpium cocois (Cocos nucifera L); Perennial plant comprises the industrial wood waste of arbor, shrub, branch material, bamboo and above-mentioned plant.In the fragmentation of vegetable fibre, screen, mat formation, in the processing step such as aftertreatment, the present invention has adopted and the essentially identical method of CN92104363.5 patent, for example adopts " parcel is theoretical " to solve the anti-coagulating action problem of vegetable fibre extract to cement.By vegetable fibre is mixed stirring with calcium oxide, calcium chloride and water, the thick liquid that calcium oxide and calcium chloride water are generated, soak into the parcel vegetable fibre, stop up the cell vestibule of vegetable fibre, make the anti-coagulating action composition in the vegetable fibre be difficult to separate out and reduce activity, thereby suppress the anticoagulation of vegetable fibre.At this, the above-mentioned identical processing step and the mechanism of inhibition vegetable fibre anticoagulation are repeated no more.
Creativeness of the present invention mainly has been to solve a difficult problem that shortens the time that thes cement solidifies in the vegetable fibre composition board pressing process, and the main points of head it off are following three key problem in technology: the one, and the prescription of optimization making sheet raw material; The 2nd, grasp appropriate hot pressing time; The 3rd, carry out humidification after the hot pressing and handle.Be illustrated respectively below.
First key problem in technology is to increase new constituent in the making sheet raw material, the first, in the making sheet raw material, add an amount of lime carbonate or sodium bicarbonate, mix with other making sheet raw materials, its consumption is 7~13% of the vegetable fibre production board oven dry weight made, adds when stirring for the first time.The second, in the making sheet raw material, add an amount of water glass and Sodium Silicofluoride, the reason of immediate response caking during owing to water glass and calcium chloride water mixing, water glass can not add when stirring for the first time, must when stirring for the second time, add separately, add cement and then become stirring for the third time, like this, the process that the mixing of making sheet raw material is become stir for three times.The time of stirring is 3~7 minutes for the first time, and the time of stirring is 2~6 minutes for the second time, and the time of Jiao Baning is 4~6 minutes for the third time.Sodium Silicofluoride is the stiffening agent of water glass, and it can accelerate the setting rate of water glass, and it can add with other raw materials when stirring for the first time.The effect of the new constituent that increases is when slab hot pressing, to be blended in lime carbonate or sodium bicarbonate decomposes in the raw material, generation CO
2Gas.Because lime carbonate or sodium bicarbonate mix with other making sheet raw materials, make the CO of generation
2Gas can fully contact with the cement in the making sheet raw material uniformly, because CO
2Gas can solidify cement rapidly to the charing effect of cement.Simultaneously, the water glass of adding also solidifies rapidly under the effect of Sodium Silicofluoride, has further increased the first intensity of slab, makes slab reach the intensity that satisfies demoulding requirement very soon, realizes short period production.
Second key problem in technology is accurately to grasp hot pressing time.In short period was produced, determining of hot pressing time was one of key issue that influences quality product.Hot pressing time is long, and the moisture in the slab in the cement is dried, and is difficult to carry out aquation again, and sheet material does not have intensity; Hot pressing time is too short, and slab does not reach intensity just, can not the demoulding unload plate.The factor that influences hot pressing time is a lot, through experiment, can adopt following experimental formula to calculate suitable hot pressing time:
T=160 (t-80)
-1+ μ [α
-1+ (β+γ)
-1]+0.5 (δ+η-29)+ξ, in the formula,
T is a hot pressing time, minute being unit; T is the medial temperature on the last lower hot pressing board, value between 90~125 ℃; μ is a vegetable fibre kind adjustment factor, and value between 21~30 is minute being unit; α is the percentage ratio that lime carbonate or sodium bicarbonate account for the production board oven dry weight, is zero dimension; β is the per-cent that calcium chloride or magnesium chloride account for the production board oven dry weight, is zero dimension; γ is that calcium oxide or calcium hydroxide account for production board oven dry weight per-cent, is zero dimension; δ is the per-cent that the water yield of adding accounts for the production board oven dry weight, is zero dimension; η has considered that Total Water that the vegetable fibre moisture percentage calculates later on accounts for the per-cent of production board oven dry weight, is zero dimension; ξ is the sheet metal thickness adjustment factor, and minute to be unit, when the finished product plate thickness was 4~8 millimeters, value was-1; When production board thickness was 9~18 millimeters, value was that the millimeter of production board actual (real) thickness subtracts 9; When production board thickness was 19~30 millimeters, value was 10.Production board thickness is called extraordinary thickness when being 19~30 millimeters, when suppressing this class sheet material, because slab is very thick, when hot pressing temperature during in lower bound, hot pressing time may prolong, the longest reaching about 30 minutes.Following table provides the hot pressing time calculated examples of 8 embodiment, and the numbering of each embodiment is general to other forms of this paper in the table, and for example the example 1 in each table all refers to embodiment 1, and the rest may be inferred by analogy for it.
Table 1 hot pressing time reckoner
| | Example 1 | Example 2 | Example 3 | Example 4 | Example 5 | Example 6 | Example 7 | Example 8 |
| T | 12 | 11 | 12 | 9 | 12 | 20 | 7.5 | 33 |
| t | 120 | 118 | 120 | 115 | 120 | 100 | 125 | 90 |
| μ | 30 | 21 | 30 | 26 | 29 | 22 | 22 | 30 |
| α | 9.2 | 6.7 | 11.2 | 13 | 11.4 | 9.45 | 9 | 9.4 |
| β | 6.6 | 5 | 5.8 | 6.6 | 5.8 | 6.7 | 3.5 | 6 |
| γ | 7.2 | 6.8 | 8 | 9.5 | 8.1 | 7.6 | 6.3 | 7 |
| δ | 29 | 29 | 30 | 31.4 | 29.2 | 27 | 28 | 29 |
| η | 3 | 1 | 2 | 1 | 3 | 1 | 1 | 3 |
| ξ | 1 | 1 | 1 | -1 | 1 | 9 | -1 | 10 |
Can adopt the hot pressing machinery of general production wood-based plate during hot pressing, hot pressing temperature is 90~125 ℃, and pressure is 2.0~3.5Mpa.
The 3rd key problem in technology is to carry out humidification after the hot pressing immediately to handle.It is that 15~30 ℃, relative humidity are to stack 5~7 days in 50~70% the environment that composite plant fiber-cement board after the hot pressing is placed on temperature.Because in hot pressed tens minutes, though the cement in the slab can reach demoulding transportation, the desired intensity just in saw limit, not fully aquation and sclerosis as yet.For improving the later strength of sheet material, must make cement that the process of abundant aquation is arranged.It is exactly in order to reach this purpose that humidification is handled.
Because the present invention has adopted above-mentioned three technology key, uses common thermocompressor, for example produces the equipment of shaving board and fiberboard, also can adopt the short period method to produce plant fiber composite plate.For some outmoded shaving board production units, transform a little, also can produce qualified vegetable fibre composition board, this has just saved facility investment greatly, has reduced product cost.
In order further to improve the performance of sheet material, when the making sheet raw material that mixes is mated formation into slab, can cover and/or in the middle of slab, add reinforcement materials such as glass fibre or its fabric, cotton fibriia or its fabric, non-woven fabrics, wire netting, tinsel, wire, fine steel rib in the upper and lower surface of slab, carry out hot pressing then.