CN109777138B - Method for preparing fireproof flame-retardant, ultra-light and high-strength paper pulp foam by adopting wood fiber raw material - Google Patents
Method for preparing fireproof flame-retardant, ultra-light and high-strength paper pulp foam by adopting wood fiber raw material Download PDFInfo
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Abstract
The invention provides a formula and a preparation method of fireproof flame-retardant, ultra-light and high-strength paper pulp foam. The formula is as follows: the composition comprises the following components in parts by weight: 100 parts of natural wood fiber raw material and 0.5-10 parts of fireproof crosslinking auxiliary agent; 1-20 parts of inorganic filler and 0-20 parts of chitosan; 0.5-10 parts by weight of foaming agent; a plurality of parts by weight of water; wherein the natural wood fiber raw material has a weight fraction of 0.5-5wt% in water. The method comprises the following steps: adding the mechanically crushed natural wood fiber raw material into the fireproof crosslinking auxiliary agent solution, and carrying out crosslinking reaction under the conditions of heating and stirring; continuously adding inorganic filler and proper amount of chitosan, and continuously stirring until the reaction is finished; then adding a foaming agent, and mechanically stirring for foaming; removing excessive water and foam, drying and forming to obtain the paper pulp foam. According to the invention, the paper pulp foam prepared by compounding the auxiliary agent and the beneficial interaction among different components has excellent performance, and has wide industrialization prospect and expected economic benefit.
Description
Technical Field
The invention belongs to the field of materials, relates to the field of green fiber materials and environment-friendly materials, and particularly relates to a paper pulp foam with ultra-light weight, high elasticity, fire resistance and water resistance and a preparation method thereof.
Background
Foam is a lightweight, highly porous material that can meet certain performance criteria. In recent years, porous foam materials have gradually become a hot spot for research on new materials due to their characteristics of ultra-light weight, permeability, high porosity, high contactable surface area, and the like. At present, polymer foams are mainly prepared from non-degradable petroleum-based materials, and pose threats to resources and environment, so that the development and utilization of renewable resources to replace traditional fossil resources is a necessary trend. Cellulose is a natural high molecular compound abundant in the earth, and is mainly present in the cell walls of higher plants. The cellulose has the advantages of wide source, no toxicity, good biocompatibility, biodegradability and the like, and the surface of the cellulose contains a large amount of hydroxyl groups, so the cellulose is easy to modify and can be used for preparing multifunctional materials. Cellulose can replace expensive and non-biodegradable synthetic materials (such as polyurethane), and is called a new generation material with great potential.
At present, there are two main types of methods for preparing light and high-porosity porous materials by using cellulose: (1) dissolving natural fiber materials to form homogeneous liquid and gel, and capturing gas in the homogeneous liquid through surface tension to form approximately spherical bubbles; then carrying out curing molding and drying under a specific environment to obtain the solid foam. However, to obtain a homogeneous cellulose solution, relatively expensive cellulose solvents are generally required; however, cellulose solvents are generally difficult to recover, and even if they can be recovered, they are extremely expensive. (2) Dispersing nano cellulose in liquid, forming gel by means of cross-linking, solvent displacement and the like, and finally obtaining the porous product by freeze drying/casting or supercritical carbon dioxide drying. These porous materials are broadly referred to as cellulosic foams, and those having nanoscale voids therein may also be referred to as aerogels. Obtaining uniform nano-cellulose dispersion, the first step is to prepare nano-cellulose, usually by TEMPO oxidation, high pressure homogenization or acid hydrolysis or by dissolving natural wood fiber raw material at low temperature and then regenerating; the chemical reagents used in the process are expensive, the production cost is high, and the environment is damaged to a certain extent.
In order to solve the above problems, researchers have been working on developing more environmentally friendly and low cost processes for preparing cellulose foams. The invention patent CN103131038A discloses a preparation method of a lignocellulose foam material. The preparation method mainly comprises the following steps: (1) smashing lignocellulose to obtain 20-200-mesh wood flour; (2) adding wood powder into water, grinding and dispersing for 30 min-48 h to obtain a lignocellulose water dispersion; (3) and (3) carrying out freeze drying treatment on the lignocellulose aqueous dispersion to obtain the lignocellulose foam material. The preparation method is simple, the raw materials are low in price, and the preparation cost is reduced; and is pure green and environment-friendly. The invention patent application CN107915860A discloses a preparation method of a nano-cellulose microporous foam material. The invention patent application firstly utilizes concentrated sulfuric acid to hydrolyze microcrystalline cellulose, prepares nano cellulose by ultrasonic centrifugation, then obtains PLA/NCC composite foam material with uniform cells by a supercritical drying method after compounding and foaming with polylactic acid (PLA). The preparation method is simple and easy to operate, and raw materials are saved. Freeze drying and supercritical drying are conventional methods for preparing porous materials. Wherein the frozen product is dehydrated through sublimation, and the network state and density of the aerogel can be adjusted by changing the freeze-drying condition and the medium. The principle of supercritical drying is that in a supercritical state, a gas-liquid interface does not exist, namely, capillary action does not exist, so that the gel cannot shrink and the structure cannot be damaged, and finally, the material filled with gas and having a nano-pore structure is obtained. However, both methods have the problems of long experimental period, high equipment production cost and complex process, and are difficult to realize large-scale production.
In summary, the foam preparation process still has many problems restricting the scale production and application thereof, such as: in the drying process, the foam generates a large cavity, so that the performance of the foam is influenced, the treatment process is long in period and not green, chemicals are expensive and difficult to recover, the preparation cost is high, and the like. In addition, the pulp foam prepared by the traditional method has poor strength, fire resistance and heat insulation performance, and is not easy to commercialize. To perform the modification, a complicated, costly or environmentally unfriendly subsequent treatment is required. Therefore, there is a need to develop an efficient, sustainable, low-cost and environmentally friendly process for preparing high performance pulp foams, which process according to the present invention just meets these urgent needs.
Disclosure of Invention
Aiming at the problems in the foam preparation in the prior art, the invention provides a preparation method of fireproof flame-retardant, ultra-light and high-strength paper pulp foam. The method of the invention not only has simple process and low cost, but also does not relate to expensive chemical reagents and processing equipment; in addition, the invention utilizes the compounding of the auxiliary agent and the beneficial interaction among different components, and the prepared paper pulp foam has excellent performance, wide industrialization prospect and expectable economic benefit.
The technical scheme of the invention is as follows: the method for preparing the fireproof flame-retardant ultra-light high-strength paper pulp foam by adopting the wood fiber raw material comprises the following steps:
(1) according to the weight ratio of 1 (20-200), adding the mechanically crushed natural wood fiber raw material into the fireproof crosslinking auxiliary agent solution, and carrying out crosslinking reaction under the conditions of heating and stirring to obtain the pulp fiber suspension. The fireproof crosslinking auxiliary agent is borate, boric acid or metaboric acid, and the borate is sodium tetraborate decahydrate, sodium metaborate, sodium polyborate, potassium tetraborate or potassium metaborate; the concentration of the fire-proof auxiliary agent solution is 0.1-0.6M. The temperature of the crosslinking reaction is 35-60 ℃, the reaction time is 0.5-6 h, and the stirring speed is 100-2000 rpm. The boron element is an element for healthy growth of plants, and the mechanical toughness of the plants can be obviously increased in the presence of a very small amount of boron element. In addition, the boron-containing compound is a green and environment-friendly flame retardant.
Wherein the natural wood fiber raw material is one or a mixture of several of commercial paper pulp, waste paper, straw agricultural wastes, cotton and cotton linters; the commercial paper pulp is bleached softwood pulp, bleached hardwood pulp, dissolving pulp or unbleached paper pulp.
(2) And (3) keeping the temperature unchanged, adding an inorganic filler and a proper amount of chitosan into the pulp fiber suspension obtained in the step (1), and continuously stirring until the reaction is finished to obtain a uniform pulp fiber mixed material. The inorganic filler is one or more of nano silicon dioxide, montmorillonite, fly ash, sepiolite, expanded perlite and hollow glass beads; the dosage of the inorganic filler is 1-20wt% of the natural wood fiber raw material. The dosage of the chitosan is 1-20wt% of the natural wood fiber raw material. The stirring speed is 100-2000 rpm, and the stirring time is 0.5-6 h. The pulp foam prepared by adding the chitosan has better strength and water resistance, and can be stably and non-collapsibly in water. The inorganic filler is added, so that the heat transfer can be retarded, the heat conductivity of the paper pulp foam is greatly reduced, and the compression strength is improved by more than 3 times of the original compression strength. The reason is that the sodium borate and the chitosan can play roles of crosslinking, retention aid and reinforcement, so that more inorganic filler can be retained by means of charge action, covalent bond linkage and the like, and the bonding force between the inorganic filler and the fiber is increased.
(3) Adding a foaming agent into the pulp fiber mixed material obtained in the step (2), and mechanically stirring for foaming; excess water and foam are then removed to yield a separated pulp foam. The foaming agent is one or more of sodium dodecyl sulfate, octylamine, decylamine, sodium dodecyl p-toluenesulfonate and fatty alcohol-polyoxyethylene ether sodium sulfate; the amount of the foaming agent is 0.5-10wt% of the natural wood fiber raw material.
(4) And (4) drying and forming the paper pulp foam obtained in the step (3) to obtain the fireproof and waterproof paper pulp foam. The drying and forming method is to carry out vacuum drying or direct drying after natural air drying for 2-10 h. The temperature of the vacuum drying is 30-60 ℃, and the time of the vacuum drying is 1-8 h; the direct drying temperature is 25-90 ℃, and the direct drying time is 10-24 h.
The formula for preparing the fireproof flame-retardant ultra-light high-strength paper pulp foam by adopting the wood fiber raw material comprises the following components in parts by weight: 100 parts of crushed natural wood fiber raw material and 0.5-10 parts of fireproof crosslinking auxiliary agent; 1-20 parts of inorganic filler and 0-20 parts of chitosan; 0.5-10 parts by weight of foaming agent; a plurality of parts by weight of water; wherein the natural wood fiber raw material has a weight fraction of 0.5-5wt% in water. The natural wood fiber raw material is one or a mixture of several of commercial paper pulp, waste paper, straw agricultural wastes, cotton and cotton linters; the commercial paper pulp is bleached softwood pulp, bleached hardwood pulp, dissolving pulp or unbleached paper pulp. The fireproof crosslinking auxiliary agent is borate, boric acid or metaboric acid, and the borate is sodium tetraborate decahydrate, sodium metaborate, sodium polyborate, potassium tetraborate or potassium metaborate; the inorganic filler is one or more of nano silicon dioxide, montmorillonite, fly ash, sepiolite, expanded perlite and hollow glass beads; the foaming agent is one or more of sodium dodecyl sulfate, octylamine, decylamine, sodium dodecyl p-toluenesulfonate and fatty alcohol-polyoxyethylene ether sodium sulfate.
The fireproof flame-retardant ultra-light high-strength pulp foam is applied to be used as a heat-insulating material for outdoor buildings and interior decoration. The heat-insulating material has the performances of fire prevention, water resistance, sound absorption/sound insulation.
The invention has the following advantages and beneficial effects:
1. the preparation method provided by the invention utilizes the synergistic crosslinking effect of boron ions, cellulose and chitosan, so that the mechanical and fireproof performances of the product are improved, the retention rates of the inorganic filler and the natural fiber are effectively increased, and the production efficiency of the product is improved; meanwhile, the increase of the inorganic filler reduces the expansion with heat and the contraction with cold of the foam material, improves the dimensional stability of the foam, and further can improve the reliability and the service life of the final paper pulp foam.
2. The preparation method provided by the invention adopts cheap natural wood fiber as a raw material, and simultaneously realizes the purposes of chemical crosslinking and foaming of cellulose by using a one-pot method; not only the raw materials are wide in source, renewable and low in price; and the preparation process is simple, the temperature is low, the preparation can be carried out under normal pressure, the energy consumption is low, the requirement on equipment is low, and therefore the feasibility of industrial production is greatly improved.
3. The preparation method has the advantages that the cost of the used chemicals is low, the generated waste liquid can be recycled, the whole process is sustainable, and the method is environment-friendly; further promoting the market prospect.
4. The density of the pulp foam prepared by the invention is as low as 20 mg/cm3(ii) a After 30 times of compression, the foam shape still maintains certain physical strength and original shape, and the maximum compression strength is up to 500 KPa; the limited oxygen index is as high as 39, the thermal conductivity coefficient is as low as 15 mW/(m.K), the self-extinguishing property is realized, and the fireproof performance is excellent.
Drawings
FIG. 1 is a schematic representation of the pulp foam prepared in example 1 of the present invention on top of dandelion.
FIG. 2 is a view showing a state after combustion of the pulp foam produced in comparative example 2.
FIG. 3 is a diagram showing a state after combustion of pulp foam prepared in example 2 of the present invention.
FIG. 4 is a diagram showing a state after combustion of pulp foam prepared in example 5 of the present invention.
FIG. 5 is a stress-strain graph of the pulp foam prepared in example 4 of the present invention.
FIG. 6 is a graph showing the steady state in water of the pulp foam prepared in example 5 of the present invention.
FIG. 7 is a photograph of an infrared thermal image of the bottom end of a pulp foam prepared in example 4 of the present invention after heating.
FIG. 8 is a graph showing an infrared thermal image of the bottom end of the pulp foam obtained in comparative example 2 after heating.
Detailed Description
The present invention will be further described with reference to the following examples.
The following examples are given by way of illustration of embodiments of the invention and are not to be construed as limiting the invention, and it will be understood by those skilled in the art that modifications and extensions may be made without departing from the spirit and scope of the invention.
Example 1: the method comprises the following steps of preparing paper pulp foam by using a commercial bleached softwood pulp board as a raw material:
(1) scattering a bleached softwood pulp board by using a grinder, then placing 3 g of scattered raw materials into a reaction container, adding 197 mL of 0.1M sodium tetraborate decahydrate solution, stirring for 2h at 35 ℃, and adjusting the stirring speed to 100 rpm; then adding 10wt% of inorganic filler sepiolite (relative to the natural fiber raw material) and 20wt% of chitosan (relative to the natural fiber raw material), and continuously stirring for 0.5h at the stirring speed of 1000 rpm; finally adding 5wt% (relative to the natural fiber raw material) of foaming agent sodium dodecyl sulfate, continuously stirring for 2h at the stirring speed of 2000 rpm, and cooling to room temperature after the reaction is finished.
(2) And removing redundant foam and liquid in a vacuum filtration mode, drying the obtained paper pulp foam for 2 hours at ambient temperature, and then drying the paper pulp foam for 14 hours in an oven at the temperature of 60 ℃ for forming to obtain the paper pulp foam.
The pulp foam had a density of 20 mg/cm3(ii) a The compression strength is 280.1 KPa, and after 30 times of compression, the original height is kept at 85%; the thermal conductivity coefficient is 35 mW/(m.K); the limiting oxygen index was 28. The pulp foam can be placed on top of dandelion (fig. 1), visually illustrating its low density, ultra light character.
Example 2: the method comprises the following steps of preparing paper pulp foam by using a commercial bleached hardwood pulp board as a raw material:
(1) mechanically dispersing bleached hardwood pulp board with a crusher, placing 3 g of the raw materials into a reaction kettle, adding 197 mL of 0.1M sodium polyborate solution, reacting at 45 ℃ for 1h, and adjusting the stirring speed to 2000 rpm; then adding 1wt% of inorganic filler nano silica (relative to the natural fiber raw material) and 5wt% of chitosan (relative to the natural fiber raw material), and continuing stirring for 1h at the stirring speed of 1500 rpm. Finally, 0.5wt% (relative to the natural fiber raw material) of octylamine serving as a foaming agent is added and stirring is continued for 2 hours at the stirring speed of 1000 rpm, and the mixture is cooled to room temperature after the reaction is finished.
(2) And removing excessive foam and liquid by means of vacuum filtration. The obtained pulp foam was dried at ambient temperature for 4h and then dried at 30 ℃ under vacuum for 8h for forming to obtain pulp foam.
The pulp foam had a density of 20.5 mg/cm3(ii) a The compression strength is 398.5 KPa, and after 30 times of compression, the original height is kept at 88%; the thermal conductivity is 25.7 mW/(m.K), and the limiting oxygen index is 33.
Example 3: the method is characterized in that the waste newspaper is used as a raw material to prepare paper pulp foam, and the method comprises the following steps:
(1) waste newspaper was scattered by a pulverizer, and then 3 g of the above raw materials were put in a reaction vessel, and 397 mL of 0.1M sodium tetraborate decahydrate solution was added. Then stirring and reacting for 0.5h at 90 ℃, adjusting the stirring speed to 1000 rpm, then adding 20wt percent of inorganic filler nano zeolite (relative to the waste paper raw material) and 15wt percent of chitosan (relative to the waste paper raw material), and continuing stirring for 3h, wherein the stirring speed is 1200 rpm. Finally adding 10wt% (relative to the waste paper raw material) of dodecyl sodium p-toluenesulfonate serving as a foaming agent, continuously stirring for 0.5h at the stirring speed of 1500 rpm, and cooling to room temperature after the reaction is finished.
(2) And removing excessive foam and liquid by means of vacuum filtration. The obtained pulp foam is dried for 4h at ambient temperature and then dried for 24h under natural conditions at 25 ℃ for forming to obtain the pulp foam.
The pulp foam had a density of 19 mg/cm3(ii) a The compression strength is 387.2KPa, and after 30 times of compression, the original height is kept to be 90%; the thermal conductivity is 18.7 mW/(m.K), and the limiting oxygen index is 31.
Example 4: the method is characterized in that the pulp foam is prepared by using commercial bleached wheat straw pulp as a raw material according to the following steps:
(1) the wheat straw pulp is broken up by a crusher, 3 g of broken-up raw materials are placed in a reaction vessel, 197 mL0.1M sodium tetraborate decahydrate solution is added, and then the mixture is stirred and reacted for 5 hours at the temperature of 60 ℃, and the stirring speed is adjusted to be 500 rpm. Then adding 5wt% of inorganic filler nano montmorillonite (relative to the natural fiber raw material) and 20wt% of chitosan (relative to the natural fiber raw material), and continuing stirring for 2h at the stirring speed of 800 rpm. Finally adding 7wt% (relative to the natural fiber raw material) of foaming agent sodium dodecyl sulfate, continuously stirring for 1h at the stirring speed of 800 rpm, and cooling to room temperature after the reaction is finished.
(2) And removing excessive foam and liquid by means of vacuum filtration. The obtained pulp foam is dried for 2h at ambient temperature and then dried for 20 h in an oven at 45 ℃ for forming to obtain the pulp foam.
The pulp foam had a density of 20.1 mg/cm3(ii) a The compression strength can reach 500.0 KPa (figure 5), and after 30 times of compression, the original height is kept to 83%; the thermal conductivity is 20.6 mW/(m.K), and the limiting oxygen index is 36. Fig. 7 is an infrared thermal image of the pulp foam prepared in this example. As can be seen in FIG. 7, the sample is placed at 70oAfter 3 hours on the C heating plate, the temperature at the top of the sample was only 15%oC, and the temperature of the middle end of the sample is only about 18 deg.CoAnd C, the heat insulation performance is good. The compressive strength of the material can reach 500 kPa
Example 5: preparing pulp foam by using cotton as a raw material, and comprising the following steps of:
(1) pulverizing cotton to 2-10 mm length with a pulverizer, placing 3 g of the above raw materials in a reaction container, and adding 197 mL of 0.2M metaboric acid solution; the reaction was then stirred at 90 ℃ for 1.5 h, with the stirring speed being adjusted to 800 rpm. Then adding 15wt% of inorganic filler nano montmorillonite (relative to the natural fiber raw material) and 8wt% of chitosan (relative to the natural fiber raw material), and continuing stirring for 0.5h at the stirring speed of 500 rpm. And finally, adding 3 wt% (relative to the natural fiber raw material) of a foaming agent fatty alcohol-polyoxyethylene ether sodium sulfate, continuously stirring for 4 hours at the stirring speed of 500 rpm, and cooling to room temperature after the reaction is finished.
(2) And removing excessive foam and liquid by means of vacuum filtration. The obtained pulp foam is dried for 4h at ambient temperature and then dried for 6h in an oven at 90 ℃ for molding to obtain the pulp foam.
The pulp foam had a density of 19.7 mg/cm3(ii) a The compression strength is 335.1 KPa, and after 30 times of compression, the original height is maintained at 78%; the thermal conductivity is 24.8 mW/(m.K), and the limiting oxygen index is 35. The pulp foam material is soaked in water and can maintain the original foam form (figure 6); in the event of ignition, self-extinguishing phenomena occur and the flame extinguishesThe original physical form can be maintained after the extinction (figure 4).
Example 6: pulp foam was prepared from unbleached hardwood pulp board according to the following steps:
(1) scattering a commercial softwood pulp board by using a grinder, then putting 3 g of the raw materials into a reaction container, and adding 197 ml of 0.4M potassium tetraborate solution; then, the mixture was stirred at 75 ℃ for 3 hours, and the stirring speed was adjusted to 1500 rpm. Then adding 8wt% (relative to the natural wood fiber raw material) of inorganic filler fly ash and 10wt% (relative to the natural wood fiber raw material) of chitosan, and continuing stirring for 4 hours at a stirring speed of 2000 rpm. And finally adding 8wt% of foaming agent sodium dodecyl sulfate (relative to the natural fiber raw material), continuously stirring for 6 hours at the stirring speed of 500 rpm, and cooling to room temperature after the reaction is finished.
(2) And removing excessive foam and liquid by means of vacuum filtration. The obtained pulp foam was dried at ambient temperature for 10h and then dried at 60 ℃ under vacuum for 1h for molding to obtain pulp foam.
The pulp foam had a density of 20.3 mg/cm3(ii) a The compression strength is 365.3 KPa, and after 30 times of compression, the original height is kept to be 87%; the thermal conductivity was 32.3 mW/(m.K) and the limiting oxygen index was 28.
Example 7: pulp foam was prepared from commercial softwood pulp according to the following steps:
(1) breaking up the pulp board by a crusher, putting 3 g of needle-leaved wood pulp board into a reaction container, and adding 597 mL of 0.6M sodium tetraborate decahydrate solution; the reaction was then stirred at 60 ℃ for 4h, the stirring speed being adjusted to 1200 rpm. Then adding 20wt% of inorganic filler nano montmorillonite (relative to natural fiber raw materials), and continuing stirring for 6 hours at the stirring speed of 100 rpm. And finally, adding 2 wt% (relative to the natural fiber raw material) of octylamine serving as a foaming agent, continuously stirring for 2 hours, adjusting the stirring speed to 1000 rpm, and cooling to room temperature after the reaction is finished.
(2) And removing excessive foam and liquid by means of vacuum filtration. The obtained pulp foam was dried at ambient temperature for 6h and then dried at 45 ℃ under vacuum for 3h for forming to obtain pulp foam.
The pulp foam had a density of 21 mg/cm3(ii) a The compression strength is 180.6 KPa, and after 30 times of compression, the original height is kept at 80 percent; the thermal conductivity is 30.6 mW/(m.K), and the limiting oxygen index is 29.
Comparative example 1: preparing pulp foam by using cotton as a raw material, and comprising the following steps of:
(1) pulverizing cotton to 2-10 mm length with a pulverizer, placing 3 g of the above raw materials in a reaction container without adding sodium borate and chitosan, stirring at 90 deg.C for 1.5 h, and adjusting stirring speed to 800 rpm. Then adding 15wt% of inorganic filler nano montmorillonite (relative to natural fiber raw materials), and continuing stirring for 0.5h, wherein the stirring speed is 500 rpm. And finally, adding 3 wt% (relative to the natural fiber raw material) of a foaming agent fatty alcohol-polyoxyethylene ether sodium sulfate, continuously stirring for 4 hours at the stirring speed of 500 rpm, and cooling to room temperature after the reaction is finished.
(2) And removing excessive foam and liquid by means of vacuum filtration. The obtained pulp foam is dried for 4h at ambient temperature and then dried for 6h in an oven at 90 ℃ for molding to obtain the pulp foam.
The compressive strength of the pulp foam was 72.8 KPa; after 30 times of compression, the original height can be kept only by 42.5 percent; the thermal conductivity is 52.8 mW/(m.K), and the limiting oxygen index is 29. As compared with the pulp foam prepared in example 5 (compressive strength of 335.1 KPa, which maintains 78% of the original height after 30 times of compression; thermal conductivity of 24.8 mW/(m.K), limiting oxygen index of 35), it was found that the compressive strength of the pulp foam was greatly reduced and the thermal conductivity was greatly increased. This is because the pulp foam fibers without the addition of sodium tetraborate and chitosan lack effective interaction with each other and also cause a large amount of inorganic filler loss during the suction filtration process, resulting in a large decrease in compressive strength and elasticity.
Comparative example 2: the method is characterized in that the pulp foam is prepared by using commercial bleached wheat straw pulp as a raw material according to the following steps:
(1) the pulp board is broken up by a crusher, 3 g of wheat straw is placed in a reaction vessel, 197 ml of 0.1M sodium tetraborate decahydrate solution is added, and then the mixture is stirred and reacted for 5 hours at the temperature of 60 ℃, and the stirring speed is adjusted to be 500 rpm. Then, no inorganic filler is added, 20wt% of chitosan (relative to the natural wood fiber raw material) is directly added, and the stirring is continued for 2 hours at the stirring speed of 800 rpm. Finally adding 7wt% (relative to the natural wood fiber raw material) of foaming agent sodium dodecyl sulfate, continuously stirring for 1h at the stirring speed of 800 rpm, and cooling to room temperature after the reaction is finished.
(2) And removing excessive foam and liquid by means of vacuum filtration. The obtained pulp foam is dried for 2h at ambient temperature and then dried for 20 h in an oven at 45 ℃ for forming to obtain the pulp foam.
The compressive strength of the pulp foam is 132.0 KPa, and after 30 times of compression, the original height of the pulp foam is kept to be 82.1 percent; the thermal conductivity coefficient is 60.6 mW/(m.K), and the limiting oxygen index is 36. Compared with example 4 (compression strength is 500.0 KPa, after 30 times of compression, the original height is kept 83 percent, the thermal conductivity is 20.6 mW/(m.K), and the limiting oxygen index is 36) which is relatively similar to the preparation process, no inorganic filler is added, the elasticity of the product is not greatly changed, but the compression strength is obviously reduced, and the thermal conductivity is greatly increased.
Fig. 8 is an infrared thermal image of the sample prepared in this example. As can be seen from fig. 8, the top temperature of the sample was 18 ℃ and the middle temperature was 23 ℃ under the condition that the bottom heating plate temperature was 70 ℃ for three hours. It is noted that the samples prepared in this comparative example still have some thermal insulation properties, but the thermal insulation properties are somewhat reduced compared to the samples with inorganic filler added (compared to fig. 7 of example 4).
Comparative example 3: preparing common paper pulp foam by using cotton as a raw material according to the following steps:
(1) pulverizing cotton to 2-10 mm length with a pulverizer, placing 3 g of the above raw materials in a reaction container without adding sodium borate and chitosan, stirring at 90 deg.C for 1.5 h, and adjusting stirring speed to 800 rpm. Then adding 3 wt% (relative to the natural fiber raw material) of a foaming agent of fatty alcohol-polyoxyethylene ether sodium sulfate, continuously stirring for 4 hours at the stirring speed of 500 rpm, and cooling to room temperature after the reaction is finished.
(2) And removing excessive foam and liquid by means of vacuum filtration. The obtained pulp foam is dried for 4h at ambient temperature and then dried for 6h in an oven at 90 ℃ for molding to obtain the pulp foam.
The pulp foam had a strength of only 1.3KPa, and rapidly collapsed in water to change its original pulp form. In addition, in the ignited state, the foam burns rapidly to become ash, and the original foam form cannot be maintained.
As can be seen from the above, the density of the pulp foam of the present invention is as low as 20 mg/cm3(ii) a After 30 times of compression, the foam shape still maintains certain physical strength and original shape, and the maximum compression strength is up to 500 KPa; the limited oxygen index is as high as 39, the thermal conductivity coefficient is as low as 15 mW/(m.K), the self-extinguishing property is realized, and the fireproof performance is excellent. The reason is that the invention utilizes the synergistic crosslinking effect of boron ions, cellulose and chitosan, not only improves the mechanical and fireproof performance of the product, but also effectively increases the retention rate of inorganic filler and natural fiber, thereby reducing the expansion with heat and the contraction with cold of the foam material and improving the dimensional stability of the foam material.
Claims (10)
1. A method for preparing fireproof flame-retardant, ultra-light high-strength paper pulp foam by adopting wood fiber raw materials; the method is characterized in that: the method comprises the following steps:
(1) adding the mechanically crushed natural wood fiber raw material into a fireproof crosslinking auxiliary agent solution according to the weight ratio of 1 (20-200), and carrying out crosslinking reaction under the conditions of heating and stirring to obtain a paper pulp fiber suspension; the fireproof crosslinking auxiliary agent is borate, boric acid or metaboric acid, and the concentration of the fireproof crosslinking auxiliary agent solution is 0.1-0.6M;
(2) keeping the temperature unchanged, adding an inorganic filler and a proper amount of chitosan into the pulp fiber suspension obtained in the step (1), and continuously stirring until the reaction is finished to obtain a uniform pulp fiber mixed material; the using amount of the inorganic filler is 1-20wt% of the natural wood fiber raw material; the dosage of the chitosan is 0-20wt% of the natural wood fiber raw material;
(3) adding a foaming agent into the pulp fiber mixed material obtained in the step (2), and mechanically stirring for foaming; then removing excessive water and foam to obtain separated paper pulp foam;
(4) and (4) drying and forming the paper pulp foam obtained in the step (3) to obtain the fireproof and waterproof paper pulp foam.
2. The method for preparing the fireproof, flame-retardant, ultra-light and high-strength pulp foam by adopting the wood fiber raw material according to claim 1, is characterized in that: the borate in the step (1) is sodium tetraborate decahydrate, sodium metaborate, sodium polyborate, potassium tetraborate or potassium metaborate; the inorganic filler in the step (2) is one or more of nano silicon dioxide, montmorillonite, fly ash, sepiolite, expanded perlite and hollow glass beads.
3. The method for preparing the fireproof, flame-retardant, ultra-light and high-strength pulp foam by adopting the wood fiber raw material according to claim 2, is characterized in that: the temperature of the crosslinking reaction in the step (1) is 35-90 ℃, the reaction time is 0.5-6 h, and the stirring speed is 100-2000 rpm.
4. The method for preparing the fireproof, flame-retardant, ultra-light and high-strength pulp foam by adopting the wood fiber raw material according to claim 2, is characterized in that: the stirring speed in the step (2) is 100-2000 rpm, and the stirring time is 0.5-6 h.
5. The method for preparing the fireproof, flame-retardant, ultra-light and high-strength pulp foam by adopting the wood fiber raw material according to claim 2, is characterized in that: the foaming agent in the step (3) is one or more of sodium dodecyl sulfate, octylamine, decylamine, sodium dodecyl p-toluenesulfonate and sodium fatty alcohol-polyoxyethylene ether sulfate; the amount of the foaming agent is 0.5-10wt% of the natural wood fiber raw material; the stirring speed is 100-2000 rpm, and the stirring time is 0.5-6 h.
6. The method for preparing the fireproof, flame-retardant, ultra-light and high-strength pulp foam by adopting the wood fiber raw material according to claim 2, is characterized in that: the drying and forming method in the step (4) is to carry out vacuum drying or direct drying after natural air drying for 2-10 h; the temperature of the vacuum drying is 30-60 ℃, and the time of the vacuum drying is 1-8 h; the direct drying temperature is 25-90 ℃, and the direct drying time is 10-24 h.
7. The method for preparing the fireproof flame-retardant, ultra-light and high-strength pulp foam by adopting the wood fiber raw material according to any one of claims 1 to 6, wherein the method comprises the following steps: the natural wood fiber raw material in the step (1) is one or a mixture of several of commodity paper pulp, waste paper, straw agricultural wastes, cotton and cotton linters; the commercial paper pulp is bleached softwood pulp, bleached hardwood pulp, dissolving pulp or unbleached paper pulp; and (4) the method for removing the water and the foam in the step (3) is vacuum filtration.
8. A fire-retardant, ultra-light, high-strength pulp foam prepared by the method of any one of claims 1 to 7, characterized in that: the composition comprises the following components in parts by weight: 100 parts of crushed natural wood fiber raw material, 0.5-10 parts of fireproof crosslinking auxiliary agent, 1-20 parts of inorganic filler and 0-20 parts of chitosan; 0.5-10 parts by weight of foaming agent; a plurality of parts by weight of water; wherein the natural wood fiber raw material has a weight fraction of 0.5-5wt% in water; the fireproof crosslinking auxiliary agent is borate, boric acid or metaboric acid, and the borate is sodium tetraborate decahydrate, sodium metaborate, sodium polyborate, potassium tetraborate or potassium metaborate.
9. The fire resistant, fire retardant, ultra light weight, high strength pulp foam of claim 8, wherein: the natural wood fiber raw material is one or a mixture of more of commercial paper pulp, waste paper, straw agricultural wastes, cotton and cotton linters, and the commercial paper pulp is bleached softwood pulp, bleached hardwood pulp, dissolving pulp or unbleached paper pulp; the inorganic filler is one or more of nano silicon dioxide, montmorillonite, fly ash, sepiolite, expanded perlite and hollow glass beads; the foaming agent is one or more of sodium dodecyl sulfate, octylamine, decylamine, sodium dodecyl p-toluenesulfonate and sodium fatty alcohol-polyoxyethylene ether sulfate.
10. Use of a fire retardant, ultra light weight, high strength pulp foam according to claim 8 or 9, characterized in that: the material is used as a heat insulation material for outdoor buildings and indoor decorations; the heat-insulating material has fireproof, waterproof and sound-absorbing properties.
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| CN114230868A (en) * | 2022-01-14 | 2022-03-25 | 宋金华 | Light heat-insulating flame-retardant composite natural polymer foam material and preparation method and application thereof |
| CN116063730B (en) * | 2023-02-22 | 2023-08-11 | 国际竹藤中心 | Natural flame-retardant bamboo pulp foam material and preparation method and application thereof |
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