A polyvinyl alcohol fiber reinforced cement board and its manufacturing method

Abstract

The present invention belongs to the technical field of wall materials and relates to a polyvinyl alcohol fiber-reinforced cement board and a manufacturing method thereof. The present invention aims to solve the problems of complex manufacturing process and poor weather resistance of existing fiber-reinforced cement boards. The present invention prepares the first PVA fiber through copolymerization reaction and surface modification, and mixes it with the first cement raw material to obtain a reinforced outer layer; prepares the second PVA fiber through crosslinking modification, and crosslinks and cures it with the second cement raw material on the surface of the reinforced outer layer to obtain a fiber-modified intermediate layer; mixes PVA resin with a foaming agent and a reinforcing agent, and foams on the surface of the fiber-modified intermediate layer to obtain a foamed inner layer; the reinforced outer layer, the fiber-modified intermediate layer, and the foamed inner layer are sequentially combined to form a polyvinyl alcohol fiber-reinforced cement board. The fiber-reinforced cement board prepared by the present invention has high strength and high toughness, and also has various composite functions such as sound insulation, heat insulation, and flame retardancy.

Description

Technical Field

[0001] The present invention belongs to the technical field of wall materials and relates to a polyvinyl alcohol fiber-reinforced cement board and a manufacturing method thereof. Background Art

[0002] As a traditional material in the construction field, cement materials have been widely used due to their good performance. With the development of the construction industry, the performance requirements for cement are also increasing day by day. The strength and functionality of traditional cement materials can no longer meet the current diverse needs of cement. Therefore, various composite cement materials or reinforced cement materials have emerged. Among them, fiber-reinforced cement, as an important branch of composite cement materials, has characteristics such as high strength and high toughness, and has attracted more and more attention.

[0003] Compared with traditional cement materials, fiber-reinforced cement materials have higher strength and lower density, and can endow the materials with various special functions according to the different characteristics of the fibers, greatly expanding the application scope of cement materials. In recent years, many progress has been made in the related research fields of fiber cement materials.

[0004] For example, Chinese Patent CN115403337B proposes a negative carbon fiber cement board and a preparation method thereof. By preparing a fiber suspension, mixing it with additives to prepare a slab, and obtaining the negative carbon fiber cement board through dehydration, curing and other treatments, it can avoid phenomena such as delamination of the cement board, and has low energy consumption and good preparation effect. The problem of this invention is that the functionality of a single-layer cement board is relatively single. Chinese Patent CN114230263B proposes a fiber cement board and a preparation method thereof. By mixing modified nano-hollow microspheres, cement glue, reinforcing fibers and other materials, a super-hydrophobic fiber cement board is prepared, which has significant fireproof and flame-retardant properties under the condition of good mechanical properties. The problem of this invention is that the preparation process has strict requirements for reaction conditions, and it is difficult to ensure process stability. Chinese Patent CN112390597B proposes a preparation method of a composite plant fiber cement board, and modifies plant straw fibers, fly ash fibers, etc., improving the mechanical properties of the fiber cement board. The problem of this invention is that the bonding strength between plant fibers and cement will gradually weaken, and it is difficult to obtain high weather resistance.

[0005] Currently, the complex manufacturing process and poor weather resistance of existing fiber-reinforced cement boards are still important problems faced by the industry.

[0006] Therefore, a polyvinyl alcohol fiber-reinforced cement board and a manufacturing method thereof are proposed. Summary of the Invention

[0007] The object of the present invention is to provide a polyvinyl alcohol fiber reinforced cement board and a manufacturing method thereof. The present invention prepares the first PVA fiber through copolymerization reaction and surface modification, and mixes it with the first cement raw material to prepare a reinforced outer layer; prepares the second PVA fiber through crosslinking modification, and crosslinks and cures it with the second cement raw material on the surface of the reinforced outer layer to prepare a fiber modified intermediate layer; mixes PVA resin with a foaming agent and a reinforcing agent, and performs foaming treatment on the surface of the fiber modified intermediate layer to obtain a foamed inner layer; the reinforced outer layer, the fiber modified intermediate layer and the foamed inner layer form a polyvinyl alcohol fiber reinforced cement board in sequence.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A manufacturing method of a polyvinyl alcohol fiber reinforced cement board, comprising the following steps:

[0010] Copolymerization reaction and surface modification to prepare the first PVA fiber:

[0011] Dissolve 100 parts of vinyl alcohol, 30 parts of vinyl chloride and 2 parts of dioctyl phthalate in tetrahydrofuran under a pressure of 5 atm, add 1 part of azobisisobutyronitrile, then raise the temperature to 60 - 80 °C and stir and react at a speed of 200 rpm for 4 - 5 h. After the solution is extruded through a spinneret, copolymer fibers are obtained, and after washing with ethanol, the first PVA precursor is obtained; heat the first PVA precursor to 120 °C and keep it for 3 h, and cool it to 25 °C to obtain the first PVA fiber.

[0012] Preliminarily mix the first PVA fiber and the first cement raw material, and perform curing treatment in a mold to obtain a reinforced outer layer.

[0013] Crosslinking modification to prepare the second PVA fiber:

[0014] Soak 100 parts of PVA fiber in water, and perform swelling treatment at 40 °C for 2 h to obtain swollen PVA fiber; put 100 parts of swollen PVA fiber into a 4 wt% glutaraldehyde solution, adjust the pH to 3 - 4, stir at 60 °C at a speed of 300 rpm for 3.5 h, wash and dry to obtain the second PVA fiber.

[0015] Stir and mix the second PVA fiber and the second cement raw material, and perform crosslinking and curing on the surface of the reinforced outer layer to obtain a fiber modified intermediate layer.

[0016] Mix PVA resin with a reinforcing agent and a foaming agent, and perform foaming treatment on the surface of the fiber modified intermediate layer to obtain a foamed inner layer.

[0017] The reinforced outer layer, the fiber modified intermediate layer and the foamed inner layer form a polyvinyl alcohol fiber reinforced cement board in sequence.

[0018] Preferably, the first cement raw material includes: high alumina cement, sulfoaluminate cement and triphenyl phosphate; wherein, the addition ratio of high alumina cement, sulfoaluminate cement and triphenyl phosphate is 30:70:1.

[0019] Preferably, the second cement raw material includes: portland cement, sulfoaluminate cement and polyethylene glycol; wherein, the addition ratio of portland cement, sulfoaluminate cement and polyethylene glycol is 60:40:5; wherein, the average molecular weight of polyethylene glycol is 2000; the specific surface area of the second cement raw material is 450 - 550m 2 / kg.

[0020] Preferably, the process of curing treatment is: mixing 3 - 5 parts of the first PVA fiber with 100 parts of the first cement raw material evenly at a water - cement ratio of 0.4, pouring at 25°C, and curing for 7 days to obtain the reinforced outer layer.

[0021] Preferably, the process of cross - linking curing is: mixing 4 - 7 parts of the second PVA fiber with 100 parts of the second cement raw material and 2 parts of 5wt% borax aqueous solution, pouring at a water - cement ratio of 0.45 on the surface of the reinforced outer layer, with a pouring temperature of 25°C, and curing for 7 days to obtain the fiber - modified intermediate layer.

[0022] Preferably, the degree of polymerization of the PVA fiber is 1800 - 2000, and the degree of alcoholysis is 98% - 99%; the degree of polymerization of the PVA resin is 200 - 300, and the degree of alcoholysis is 85 - 90%; the reinforcing agent includes silica and polypropylene fiber; the foaming agent is sodium dodecyl benzene sulfonate.

[0023] Preferably, the process of foaming treatment is: dissolving 100 parts of PVA resin and 2 parts of foaming agent in 300 parts of water, adding 25 parts of polypropylene fiber and 5 parts of nano - silica, heating to 50°C and stirring at a speed of 1500rpm for 30min, then pouring on the surface of the fiber - modified intermediate layer, drying at 50°C for 12h, and then cooling to 25°C and drying for 48h to obtain the foamed inner layer.

[0024] A polyvinyl alcohol fiber - reinforced cement board, comprising a reinforced outer layer, a fiber - modified intermediate layer and a foamed inner layer; wherein, the thickness of the reinforced outer layer is 5mm, the thickness of the fiber - modified intermediate layer is 6mm, and the thickness of the foamed inner layer is 6mm.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] 1. The first PVA fiber prepared by copolymerization reaction and surface modification is cured with the first cement raw material containing high-alumina cement, sulfoaluminate cement and triphenyl phosphate to obtain a reinforced outer layer. Through the copolymerization reaction of vinyl alcohol and vinyl chloride, the flame retardancy and mechanical strength of the first PVA fiber are enhanced, and the fire resistance and flame retardancy of the reinforced outer layer are greatly improved by the synergistic effect with triphenyl phosphate. At the same time, the rapid hardening property of high-alumina cement enables the first PVA fiber to be quickly cured after being mixed with the first cement raw material. The surface-modified PVA fiber effectively forms a hardening network with the cement, improving the mechanical strength and weather resistance of the reinforced outer layer.

[0027] 2. The second PVA fiber modified by crosslinking is crosslinked and cured with the second cement raw material containing polyethylene glycol under the action of an aqueous borax solution to prepare a fiber-modified intermediate layer. A higher content of the modified PVA fiber can play a role in bridging and strengthening the cement matrix. At the same time, the modified second PVA fiber can form a crosslinking network with portland cement under the action of borax, avoiding the problem of the gradual decrease in the bonding strength between the fiber and the cement, and having significant anti-aging properties on the premise of ensuring the toughness of the fiber-modified intermediate layer.

[0028] 3. The second PVA fiber and the second cement raw material are crosslinked and cured on the surface of the reinforced outer layer after 7 days of curing. Without affecting the basic structure and performance of the reinforced outer layer, a partially crosslinked fiber-cement network is formed between the reinforced outer layer and the fiber-modified intermediate layer, organically connecting the two different reinforced cement boards, effectively improving the problem of easy separation of the adhesive bonding between the multi-layer composite cement boards, reducing the process difficulty, and not emitting polluting gases. At the same time, the organic combination of the two-layer structure can enhance the functional composite and synergistic effect of the two-layer structure, ensuring that the reinforced cement board has both high toughness, high strength, and high weather resistance.

[0029] 4. The PVA resin, reinforcing agent, and foaming agent are foamed on the surface of the fiber-modified intermediate layer to directly prepare a foamed inner layer, reducing the structural weight of the composite cement board. At the same time, the in-situ foaming process enables the foamed inner layer to fully fill the small depressions and holes on the surface of the fiber-modified intermediate layer, forming a flat filling layer, improving the cushioning and shock absorption as well as heat insulation properties of the foamed inner layer, and not requiring additional adhesives, effectively improving its mechanical strength.

[0030] 5. By arranging the fiber-modified intermediate layer between the reinforced outer layer and the foamed inner layer, the reinforced cement board prepared by the present invention has a relatively low preparation process difficulty on the premise of having functions such as flame retardancy, high strength, high toughness, sound insulation and heat insulation. Due to its high PVA content and being prepared by cross-linking and curing, the fiber-modified intermediate layer has good compatibility with both the organic structure of the foamed inner layer and the inorganic structure of the reinforced outer layer, can effectively integrate the functions of the two, and significantly improve the anti-aging property of the reinforced cement board, enabling it to have a longer service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic structural diagram of the polyvinyl alcohol fiber-reinforced cement board in the present invention.

[0032] In the figure, 1, reinforced outer layer; 2, fiber-modified intermediate layer; 3, foamed inner layer. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The technical solutions of the present invention will be clearly and completely described below through some examples and experimental examples. Obviously, the described examples are only a part of the examples of the present invention, rather than all the examples. All other examples obtained by those of ordinary skill in the art based on the examples of the present invention without making creative efforts belong to the scope of protection of the present invention.

[0034] Referring to Figure 1 the shown structural schematic diagram, the present invention provides a polyvinyl alcohol fiber-reinforced cement board and its manufacturing method, and the technical solutions are as follows:

[0035] Example 1

[0036] 100 parts of vinyl alcohol, 30 parts of vinyl chloride and 2 parts of dioctyl phthalate are dissolved in tetrahydrofuran under a pressure of 5 atm. After adding 1 part of azobisisobutyronitrile, the temperature is raised to 60 °C and stirred at a speed of 200 rpm for 4 h. The solution is extruded through a spinneret to obtain copolymer fibers, which are washed with ethanol to obtain the first PVA precursor; the first PVA precursor is heated to 120 °C and maintained for 3 h, and then cooled to 25 °C to obtain the first PVA fiber.

[0037] 3 parts of the first PVA fiber are mixed evenly with 100 parts of the first cement raw material at a water-cement ratio of 0.4, and poured at 25 °C. After curing for 7 days, the reinforced outer layer 1 is obtained.

[0038] The first cement raw material includes: high-alumina cement, sulphoaluminate cement and triphenyl phosphate; among them, the addition ratio of high-alumina cement, sulphoaluminate cement and triphenyl phosphate is 30:70:1.

[0039] Soak 100 parts of PVA fibers in water, and after swelling treatment at 40 °C for 2 h, swollen PVA fibers are obtained; put 100 parts of swollen PVA fibers into a 4 wt% glutaraldehyde solution, adjust the pH to 3, stir at 60 °C at a speed of 300 rpm for 3.5 h, and after washing and drying, the second PVA fibers are obtained. Among them, the degree of polymerization of the PVA fibers is 1800, and the degree of alcoholysis is 98%.

[0040] Mix 4 parts of the second PVA fibers with 100 parts of the second cement raw material and 2 parts of a 5 wt% borax aqueous solution, and pour them onto the surface of the enhanced outer layer 1 at a water-cement ratio of 0.45. The pouring temperature is 25 °C, and after curing for 7 days, the fiber-modified intermediate layer 2 is obtained.

[0041] The second cement raw material includes: Portland cement, sulfoaluminate cement and polyethylene glycol; among them, the addition ratio of Portland cement, sulfoaluminate cement and polyethylene glycol is 60:40:5; among them, the average molecular weight of polyethylene glycol is 2000; the specific surface area of the second cement raw material is 450 m 2 / kg.

[0042] Dissolve 100 parts of PVA resin and 2 parts of sodium dodecylbenzenesulfonate in 300 parts of water, add 25 parts of polypropylene fibers and 5 parts of nano-silica, heat up to 50 °C and stir at a speed of 1500 rpm for 30 min, then pour it onto the surface of the fiber-modified intermediate layer 2. After drying at 50 °C for 12 h, cool down to 25 °C and dry for 48 h to obtain the foamed inner layer 3.

[0043] Among them, the degree of polymerization of the PVA resin is 200, and the degree of alcoholysis is 85%; the degree of polymerization of the polypropylene fibers is 1500; the average particle size of the nano-silica is 50 nm, and the PDI is 0.1.

[0044] Examples 2-10 are different from Example 1 in process parameters, and other process steps are the same. The relevant parameters are summarized in Tables 1 and 2.

[0045] Examples 11-20 are different from Example 1 in process parameters, and sodium lauryl polyoxyethylene ether sulfate is used as the foaming agent. Other process steps are the same. The relevant parameters are summarized in Tables 1 and 2.

[0046] Table 1 Process parameter changes in Examples 1-20 (I)

[0047]

[0048] Table 2 Process parameter changes in Examples 1-20 (II)

[0049]

[0050] Comparative Example 1

[0051] Different from Example 1, PVA fibers with a degree of polymerization of 1800 and a degree of alcoholysis of 98% were used to replace the first PVA fibers for the curing treatment, and other process parameters were the same.

[0052] Comparative Example 2

[0053] Different from Example 1, PVA fibers with a degree of polymerization of 1800 and a degree of alcoholysis of 98% after surface modification were used to replace the first PVA fibers for the curing treatment, and other process parameters were the same.

[0054] Comparative Example 3

[0055] Different from Example 1, the first PVA fibers were not subjected to surface modification treatment, and other process parameters were the same.

[0056] Comparative Example 4

[0057] Different from Example 1, triphenyl phosphate was not added to the first cement raw material, and other process parameters were the same.

[0058] Comparative Example 5

[0059] Different from Example 1, high alumina cement was not added to the first cement raw material, and an equal amount of sulphoaluminate cement was used instead, and other process parameters were the same.

[0060] Comparative Example 6

[0061] Different from Example 5, the borax aqueous solution was not added, and other process parameters were the same.

[0062] Comparative Example 7

[0063] Different from Example 5, the crosslinking modification of the second PVA fibers was not carried out, and other process parameters were the same.

[0064] Comparative Example 8

[0065] Different from Example 5, polyethylene glycol was not added to the second cement raw material, and other process parameters were the same.

[0066] Comparative Example 9

[0067] Different from Example 5, the addition amount of the second PVA fibers was changed to 2 parts, and other process parameters were the same.

[0068] Comparative Example 10

[0069] Different from Example 10, the curing time of the enhanced outer layer 1 was changed to 3 days, and other process parameters were the same.

[0070] Comparative Example 11

[0071] Different from Example 10, the curing time of the enhanced outer layer 1 was changed to 14 days, and other process parameters were the same.

[0072] Comparative Example 12

[0073] Different from Example 10, the enhanced outer layer 1 and the fiber-modified intermediate layer 2 were prepared separately and bonded with polyurethane adhesive, and other process parameters were the same.

[0074] Comparative Example 13

[0075] Different from Example 11, nano-silica was not added to the reinforcing agent, and other process parameters were the same.

[0076] Comparative Example 14

[0077] Different from Example 11, polypropylene fiber was not added to the reinforcing agent, and other process parameters were the same.

[0078] Comparative Example 15

[0079] Different from Example 11, the foamed inner layer 3 was prepared separately and bonded to the surface of the fiber-modified intermediate layer 2 with polyurethane adhesive, and other process parameters were the same.

[0080] Comparative Example 16

[0081] Different from Example 15, the fiber-modified intermediate layer 2 was removed, and the foamed inner layer 3 was directly prepared on the surface of the enhanced outer layer 1, and other process parameters were the same.

[0082] Comparative Example 17

[0083] Different from Example 15, the enhanced outer layer 1 was placed between the fiber-modified intermediate layer 2 and the foamed inner layer 3, and other process parameters were the same.

[0084] Comparative Example 18

[0085] Different from Example 15, the foamed inner layer 3 was placed between the fiber-modified intermediate layer 2 and the enhanced outer layer 1, and other process parameters were the same.

[0086] Experimental Example 1

[0087] Take the polyvinyl alcohol fiber-reinforced cement boards prepared in Examples 1-4 and Comparative Examples 1-5, cut them into pieces of 50 cm × 50 cm, heat the surface of the enhanced outer layer 1 with a high-temperature spray gun, adjust the flame temperature to 1000 °C, and the heating time is 5 min. Record the temperature on the side of the foamed inner layer 3 of the polyvinyl alcohol fiber-reinforced cement board after heating and the cracking and peeling conditions on the surface of the enhanced outer layer 1. The obtained results are summarized in Table 3.

[0088] The compressive properties of the polyvinyl alcohol fiber-reinforced cement boards prepared in Examples 1-4 and Comparative Examples 1-5 were tested with reference to GB / T50081-2002 Standard Test Method for Mechanical Properties of Ordinary Concrete. The results are summarized in Table 3.

[0089] To characterize the weather resistance of the reinforced cement board as an exterior wall material, at 50 °C and 90% humidity, the reinforced outer layer 1 of the polyvinyl alcohol fiber-reinforced cement boards prepared in Examples 1-4 and Comparative Examples 1-5 was sprayed with 1 wt% hydrochloric acid and kept for 24 h, and then their respective compressive strengths were tested. The results are summarized in Table 3.

[0090] Table 3 Fire resistance, compressive strength and weather resistance of the cement boards prepared in Examples 1-4 and Comparative Examples 1-5

[0091]

[0092] As shown by the fire resistance, compressive strength and weather resistance data in Table 3, the reinforced cement boards prepared in Examples 1-4 all have high compressive strength, and do not show significant cracking and spalling under direct baking of high-temperature flame for a short time. The temperature of the inner layer is much lower than the flame temperature, and they have good fire resistance and flame retardancy. At the same time, the loss of compressive strength of the reinforced cement board after acid treatment is not large, and it has excellent weather resistance as an exterior wall material. In Comparative Example 1, since PVA fibers that have not undergone polyvinyl chloride copolymerization and surface modification are not used, the fire resistance and flame retardancy are significantly reduced, and the compressive strength is also significantly lost. In Comparative Example 2, the surface of the un-copolymerized PVA fibers was modified, improving the properties of the obtained reinforced cement board, but there is still a certain performance loss compared with Examples 1-4. In Comparative Example 3, copolymerized PVA fibers were used but not surface-modified, and the degree of binding between the PVA fibers and the cement matrix is low. Therefore, cracking occurs at high temperature, and the compressive strength also decreases to a certain extent. In Comparative Example 4, due to the absence of triphenyl phosphate, the fire resistance is significantly reduced. While the reinforced outer layer 1 cracks and peels off, the temperature of the inner layer also rises significantly, and the fire protection performance is greatly reduced. In Comparative Example 5, because high-alumina cement is not used, the strength of the reinforced cement board decreases, and the fire resistance drops significantly. In summary, through the copolymerization reaction of vinyl alcohol and vinyl chloride, the flame retardancy and mechanical strength of the first PVA fibers can be significantly enhanced, and the fire resistance and flame retardancy of the reinforced outer layer 1 can be improved through the synergistic effect with triphenyl phosphate; further, the rapid hardening property of high-alumina cement enables the first PVA fibers to be quickly cured after being mixed with the first cement raw material, and the surface-modified PVA fibers effectively form a hardening network with the cement, improving the mechanical strength and weather resistance of the reinforced outer layer 1.

[0093] Experimental Example 2

[0094] The polyvinyl alcohol fiber-reinforced cement boards prepared in Examples 5-9 and Comparative Examples 6-9 were cut into cement boards of 300 mm * 200 mm, and fracture toughness experiments were carried out. The obtained results are summarized in Table 4.

[0095] To characterize the anti-aging properties of different cement boards, the polyvinyl alcohol fiber-reinforced cement boards prepared in Examples 5-9 and Comparative Examples 6-9 were cooled to -10 °C, then heated to 140 °C at a heating rate of 50 °C / min, held for 3 min and then cooled back to -10 °C again. After 50 cycles, the fracture toughness experiment was carried out again. The obtained results are summarized in Table 4.

[0096] Table 4 Fracture toughness and anti-aging properties of cement boards prepared in Examples 5-9 and Comparative Examples 6-9

[0097]

[0098] As shown in the fracture toughness and anti-aging property data in Table 4, Examples 5-9 have relatively stable fracture toughness. After the cooling-heating aging test, the fracture toughness attenuation is small, and they have significant anti-aging properties. In Comparative Example 6, no borax aqueous solution was added, and the in-situ crosslinking and curing process of the second PVA fiber and the second cement raw material was difficult to carry out. During the ordinary cement curing process, it was difficult to form a composite crosslinking network, resulting in a significant reduction in the toughness of the obtained cement board. In Comparative Example 7, the PVA fiber was not crosslinked and modified, resulting in a reduction in the toughness of the formed fiber-modified intermediate layer 2, and the combination of the PVA fiber and the cement was greatly affected by the environment, and the bonding strength decreased significantly after the aging test, resulting in an obvious reduction in toughness. In Comparative Example 8, no polyethylene glycol was added, and the compatibility between the PVA fiber and the cement matrix decreased. Therefore, the bonding strength decreased significantly after the aging test, which also led to an obvious reduction in toughness. In Comparative Example 9, the amount of the second PVA fiber was reduced, and the density of the reinforcement network was decreased, resulting in a certain degree of reduction in the toughness of the reinforced cement board. In summary, the fiber-modified intermediate layer 2 prepared by the crosslinking and curing of the crosslinked and modified second PVA fiber and the second cement raw material containing polyethylene glycol under the action of the borax aqueous solution has significant high toughness. At the same time, because the modified high-content second PVA fiber and the portland cement form a three-dimensional crosslinking network, the problem of the gradual decrease in the bonding strength between the fiber and the cement is avoided, and it has significant anti-aging properties on the premise of ensuring the toughness of the fiber-modified intermediate layer 2.

[0099] Experimental Example 3

[0100] Referring to Experimental Example 1 and Experimental Example 2, the compressive strength, compressive strength after acid treatment, fracture toughness, and fracture toughness after aging treatment of the reinforced cement boards prepared in Example 10 and Comparative Examples 10-12 were tested. The obtained results are summarized in Table 5.

[0101] Table 5 Compressive strength, compressive strength after acid treatment, fracture toughness, and fracture toughness after aging treatment of the cement boards prepared in Example 10 and Comparative Examples 10-12

[0102]

[0103] As shown in the relevant data in Table 5, the cement boards prepared in Example 10 and Examples 1-9 have similar compressive strength and fracture toughness, and their weather resistance and anti-aging properties are also almost the same. In Comparative Example 10, due to the too short curing time of the reinforced outer layer 1, the curing process of the reinforced outer layer 1 was interfered during the preparation of the fiber-modified intermediate layer 2, resulting in more structural defects, which were reflected in the significant decrease in the fracture toughness and compressive strength of the cement board product. In Comparative Example 11, since the curing of the reinforced outer layer 1 has been completely completed, it is difficult to form a partially cross-linked fiber-cement network between the two layers during the preparation of the fiber-modified intermediate layer 2, resulting in a decrease in its toughness and aging resistance, but the compressive strength increased slightly. In Comparative Example 12, the reinforced outer layer 1 and the fiber-modified intermediate layer 2 were not combined through a cross-linking curing process, but were directly bonded with an adhesive. Therefore, the composite effect of the two layers was significantly reduced, and all properties of the cement board showed great losses. In summary, cross-linking curing on the surface of the reinforced outer layer 1 after 7 days of curing effectively formed a partially cross-linked fiber-cement network between the two layers, organically connecting the two different reinforced cement boards, improving the composite effect of the two different structural board layers, reducing the process difficulty, and ensuring that the reinforced cement board has both high toughness and high strength while also having high weather resistance.

[0104] Experimental Example 4

[0105] Referring to Experimental Example 1 and Experimental Example 2, the compressive strength and fracture toughness of the reinforced cement boards prepared in Examples 11-14 and Comparative Examples 13-15 were tested, and the results are summarized in Table 6.

[0106] The thermal conductivity of the reinforced cement boards prepared in Examples 11-14 and Comparative Examples 13-15 was measured, and the results are summarized in Table 6.

[0107] Table 6 Thermal conductivity, compressive strength, and fracture toughness of the cement boards prepared in Examples 11-14 and Comparative Examples 13-15

[0108]

[0109] As shown in the data of thermal conductivity, compressive strength, and fracture toughness in Table 6, for Examples 11 - 14, sodium lauryl ether sulfate was used as the foaming agent. Although the strength of the foam layer decreased, the overall fracture toughness and compressive strength of the reinforced cement board were still at a relatively good level, and the thermal conductivity was low, indicating good heat insulation performance. For Comparative Example 13, the absence of nano-silica significantly reduced the strength of the foaming layer, resulting in a decrease in the overall fracture toughness and compressive strength of the reinforced cement board, but had little effect on the thermal conductivity. For Comparative Example 14, due to the absence of polypropylene fibers, the foam structure of the inner foaming layer 3 was unstable, leading to a decrease in the heat insulation performance of the foaming layer, that is, a relatively large increase in the thermal conductivity, and had a relatively small impact on the fracture toughness and compressive strength. For Comparative Example 15, the inner foaming layer 3 was not prepared in-situ on the surface of the fiber-modified intermediate layer 2, resulting in the foaming process being unable to fully fill the small depressions and holes on the surface of the intermediate layer, slightly reducing the mechanical strength and heat insulation performance of the reinforced cement board. In summary, the synergistic effect of the two reinforcing agents and the in-situ foaming process made the combination of the inner foaming layer 3 and the fiber-modified intermediate layer 2 closer, the filling layer smoother, effectively improving the buffering and shock absorption and heat insulation performance of the inner foaming layer, and without the need for additional gluing, effectively improving its mechanical strength.

[0110] Experimental Example 5

[0111] Referring to Experimental Example 2, the fracture toughness and anti-aging properties of the reinforced cement boards prepared in Examples 15 - 20 and Comparative Examples 16 - 18 were tested, and the obtained results are summarized in Table 7.

[0112] The sound absorption coefficient of the reinforced cement boards prepared in Examples 15 - 20 and Comparative Examples 16 - 18 was tested using the standing wave tube method, and the obtained results are summarized in Table 7.

[0113] Table 7 Fracture toughness, anti-aging property, and sound absorption coefficient of the cement boards prepared in Examples 15 - 20 and Comparative Examples 16 - 18

[0114]

[0115] As shown in the data of fracture toughness, anti-aging property and sound absorption coefficient in Table 7, there is no significant difference in fracture toughness and anti-aging property between Examples 15-20 and Examples 1-14, and the sound absorption coefficient is relatively high, having the sound insulation performance required for exterior wall materials. In Comparative Example 16, due to the absence of the fiber-modified intermediate layer 2, the combination of the reinforcing outer layer 1 and the foamed inner layer 3 is not tight, and the structure of the layer with the strongest toughness is lacking, resulting in a significant reduction in the fracture toughness of the cement board and a significant attenuation in the sound absorption coefficient. In Comparative Examples 17 and 18, the order of the three functional layers was changed. However, whether the reinforcing outer layer 1 is placed in the center or the foamed inner layer 3 is placed in the center, their fracture toughness and anti-aging property are far inferior to the structure with the fiber-modified intermediate layer 2 in the center, and the sound absorption coefficient is also significantly reduced. In summary, setting the fiber-modified intermediate layer 2 between the reinforcing outer layer 1 and the foamed inner layer 3 can effectively combine the different functions of the three-layer structure and give play to the advantages of the three in different aspects. That is, due to its high PVA content and being prepared by crosslinking and curing, the fiber-modified intermediate layer has good compatibility with both the organic structure of the foamed inner layer and the inorganic structure of the reinforcing outer layer, can effectively integrate the functionality of the two, significantly improve the anti-aging property of the reinforced cement board, and ensure the normal performance of its high strength, high toughness, sound insulation and heat insulation functions.

[0116] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made in these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for manufacturing a polyvinyl alcohol fiber reinforced cement board, characterized in that: The production method is as follows: Preliminarily mixing the first PVA fiber and the first cement raw material, and curing them in a mold to obtain a reinforced outer layer (1); Wherein, the first PVA fiber is obtained by copolymerization and surface modification; The copolymerization process is as follows: 100 parts of vinyl alcohol, 30 parts of vinyl chloride and 2 parts of dioctyl phthalate are dissolved in tetrahydrofuran at a pressure of 5 atm, 1 part of azobisisobutyronitrile is added, the temperature is raised to 60-80°C, and the mixture is stirred at a speed of 200 rpm for reaction for 4-5 hours, the solution is extruded through a spinneret to obtain copolymer fibers, and the copolymer fibers are washed with ethanol to obtain a first PVA precursor; the surface modification process is as follows: the first PVA precursor is heated to 120°C, maintained for 3 hours, and cooled to 25°C to obtain the first PVA fiber; The first cement raw material includes: high alumina cement, sulphoalumina cement and triphenyl phosphate; wherein the addition ratio of the high alumina cement, the sulphoalumina cement and the triphenyl phosphate is 30:70:1; The second PVA fiber and the second cement raw material are stirred and mixed, and after the surface of the reinforced outer layer (1) is cross-linked and cured, a fiber-modified middle layer (2) is obtained; Wherein, the second PVA fiber is obtained by cross-linking modification; The second cement raw material includes: silicate cement, sulphoaluminum cement and polyethylene glycol; wherein the addition ratio of the silicate cement, the sulphoaluminum cement and the polyethylene glycol is 60:40:5; The cross-linking modification process is as follows: 100 parts of PVA fibers are soaked in water, and swelled at 40° C. for 2 hours to obtain swollen PVA fibers; 100 parts of the swollen PVA fibers are placed in a 4wt% glutaraldehyde solution, the pH is adjusted to 3-4, stirred at 60° C. at a speed of 300 rpm for 3.5 hours, and washed and dried to obtain the second PVA fibers; The PVA resin is mixed with a reinforcing agent and a foaming agent, and then foamed on the surface of the fiber-modified intermediate layer (2) to obtain a foamed inner layer (3), thereby producing the polyvinyl alcohol fiber-reinforced cement board.

2. The method for manufacturing a polyvinyl alcohol fiber reinforced cement board according to claim 1, characterized in that: The average molecular weight of the polyethylene glycol is 2000; the specific surface area of ​​the second cement raw material is 450-550m 2 / kg.

3. The method for manufacturing a polyvinyl alcohol fiber reinforced cement board according to claim 1, characterized in that: The curing process is as follows: 3-5 parts of the first PVA fibers are uniformly mixed with 100 parts of the first cement raw material at a water-cement ratio of 0.4, poured at 25° C., and cured for 7 days to obtain the reinforced outer layer (1).

4. The method for manufacturing a polyvinyl alcohol fiber reinforced cement board according to claim 1, characterized in that: The PVA fiber has a polymerization degree of 1800-2000 and an alcoholysis degree of 98%-99%.

5. The method for manufacturing a polyvinyl alcohol fiber reinforced cement board according to claim 1, characterized in that: The cross-linking and curing process is as follows: 4-7 parts of the second PVA fibers are mixed with 100 parts of the second cement raw material and 2 parts of a 5wt% borax aqueous solution, and poured on the surface of the reinforced outer layer (1) at a water-cement ratio of 0.45 at a pouring temperature of 25°C. After curing for 7 days, the fiber-modified intermediate layer (2) is obtained.

6. The method for manufacturing a polyvinyl alcohol fiber reinforced cement board according to claim 1, characterized in that: The PVA resin has a polymerization degree of 200-300 and a degree of alcoholysis of 85-90%; the reinforcing agent includes nano-silica and polypropylene fiber, and the foaming agent is sodium dodecylbenzene sulfonate or sodium polyoxyethylene fatty alcohol ether sulfate; the foaming process is as follows: 100 parts of the PVA resin and 2 parts of the foaming agent are dissolved in 300 parts of water, 25 parts of the polypropylene fiber and 5 parts of the nano-silica are added, the temperature is raised to 50° C., the mixture is stirred at a speed of 1500 rpm for 30 minutes, and then poured on the surface of the fiber-modified middle layer (2), dried at 50° C. for 12 hours, and then cooled to 25° C. and dried for 48 hours to obtain the foamed inner layer (3).

7. A polyvinyl alcohol fiber reinforced cement board, characterized in that: The polyvinyl alcohol fiber reinforced cement board is manufactured by the manufacturing method described in any one of claims 1 to 6; the polyvinyl alcohol fiber reinforced cement board comprises: a reinforced outer layer (1), a fiber-modified middle layer (2) and a foamed inner layer (3); wherein the thickness of the reinforced outer layer (1) is 5 mm, the thickness of the fiber-modified middle layer (2) is 6 mm, and the thickness of the foamed inner layer (3) is 6 mm; the fiber-modified middle layer (2) is located between the reinforced outer layer (1) and the foamed inner layer (3).

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