Extruded sheet and preparation method thereof

Abstract

The invention relates to the technical field of building materials, in particular to an extruded sheet and a preparation method thereof, and the extruded sheet comprises the following raw materials in parts by weight: 60-70 parts of polystyrene resin, 30-40 parts of copolymer resin, 5-10 parts of a foaming agent, 0.5-0.8 part of an antioxidant, 1-2 parts of zinc stearate and 0.2-0.5 part of calcium carbonate. Through gradient chain segment design of the amphiphilic copolymer and a sodium alginate-calcium ion cross-linked network, the compression strength and bending strength of the prepared extruded sheet are improved, and the extruded sheet has good rigidity and deformation resistance. And meanwhile, the water vapor permeability of the extruded sheet is relatively low, so that the prepared extruded sheet can effectively balance the barrier and ventilation requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly to an extruded board and a preparation method thereof. Background Art

[0002] An extruded board is a rigid foam plastic board formed by heating and extrusion molding, with a continuous and uniform surface layer and a closed-cell honeycomb structure, and is an important part of the third-generation rigid foamed thermal insulation materials. With the rapid development of the construction industry and the continuous improvement of energy conservation and emission reduction requirements, the demand for high-performance thermal insulation materials is increasing day by day. The extruded board shows great application potential in the fields of building thermal insulation, moisture-proof, heat insulation, etc. due to its excellent thermal insulation performance, compressive strength, moisture-proof performance and environmental protection characteristics. The extruded board has a complete closed-cell honeycomb structure inside, and the structures are closely connected without gaps, with a low thermal conductivity coefficient and a high compressive strength. The extruded board is particularly widely used in the construction field. In terms of wall thermal insulation, the extruded board can effectively reduce building energy consumption and improve the living comfort; in terms of roof thermal insulation, the extruded board can effectively prevent problems such as roof leakage and frosting, and extend the service life of the building; in terms of ground moisture-proof and thermal insulation, the extruded board can effectively control ground frost heave and protect the safety of the foundation. In addition, the extruded board is also widely used in the moisture-proof and thermal insulation of low-temperature storage floors, parking platforms, airport runways, highways and other fields.

[0003] In the prior art, the extruded board material itself has a relatively high strength, so its material is relatively brittle and hard, with low structural flexibility, not easy to be bent, and prone to deformation, bulging, and even detachment of the thermal insulation layer. In building construction, if holes need to be drilled or other processing operations are carried out on the board, it is easy to cause phenomena such as cracks, breakage or splitting of the board. In addition, the surface of the extruded board is relatively smooth, with weak glue absorption, and poor bonding performance with other materials. During the bonding process, it is easy to damage the surface of the extruded board, resulting in insecure bonding and easy occurrence of detachment or cracking. The extruded board has a dense foaming structure, resulting in poor air permeability. When the temperature difference between the two sides of the panel is large and the humidity is high, water vapor is easily accumulated inside the extruded board, resulting in dew condensation, affecting the thermal insulation effect and service life. At the same time, the treatment of waste extruded boards is relatively difficult and it is difficult to recycle. Summary of the Invention

[0004] In order to solve the problems mentioned in the above background art, the present invention provides an extruded board and a preparation method thereof.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] An extruded board, comprising the following raw materials by weight parts: 60-70 parts of polystyrene resin, 30-40 parts of copolymer resin, 5-10 parts of foaming agent, 0.5-0.8 parts of antioxidant, 1-2 parts of zinc stearate, and 0.2-0.5 parts of calcium carbonate.

[0007] Further, the foaming agent includes one or more of azodicarbonamide, sodium bicarbonate, azodiisobutyronitrile, and cyclopentane.

[0008] Further, the antioxidant includes one or more of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 2,6-di-tert-butyl-p-cresol, tris(2,4-di-tert-butylphenyl) phosphite, dilauryl thiodipropionate, and N,N'-diphenyl-p-phenylenediamine.

[0009] Further, the copolymer resin is prepared by the following steps:

[0010] S1. Add adipic acid, butanediol, and L-malic acid into a reactor, protect with nitrogen, control the temperature, stir and react for 2-3 h, add tetrabutyl titanate, raise the temperature, increase the vacuum degree, and react for 4-5 h. After the reaction, pour the molten copolymer into a polytetrafluoroethylene mold to cool, crush it into particles with a particle size <1 mm, wash with methanol, and vacuum dry at 60 °C until constant weight to obtain polybutylene adipate-poly(malic acid) copolymer particles;

[0011] S2. Add the copolymer particles into dimethyl sulfoxide, stir at 55-60 °C for 2-3 h until completely dissolved to obtain solution A. Add sodium alginate into water, stir at 40-45 °C for 1-2 h until fully swollen to obtain solution B. Slowly drop solution B into solution A, shear and emulsify to form a water-in-oil emulsion. Dropwise add an aqueous calcium chloride solution, continue to stir for 2-3 h, then pour the composite emulsion into water to precipitate the resin. Let it stand for 1-2 h, then filter, wash, and dry to obtain a white porous copolymer resin.

[0012] Further, in step S1, the mass ratio of adipic acid, butanediol, L-malic acid, and tetrabutyl titanate is (10-11):(7.5-8):(8-9):(0.2-0.3).

[0013] Further, in step S2, the mass ratio of the copolymer particles to dimethyl sulfoxide is (2.5-3):(45-50), the mass ratio of sodium alginate to water is (5-6):(50-60), the mass ratio of calcium chloride to water in the aqueous calcium chloride solution is (2-3):(10-15), and the dropping amount is 15-16 wt%.

[0014] Further, in step S1, the controlled temperature is 150-160 °C, the temperature for raising the temperature is 210-220 °C, and the vacuum degree is increased to <10 Pa.

[0015] Furthermore, in step S2, the shearing speed is 5000 - 6000 rpm, and the emulsifying time is 10 - 15 min.

[0016] According to another aspect of the present invention, there is provided a method for preparing the above-mentioned extruded board, comprising the following steps:

[0017] A1. Weigh parts by weight of polystyrene resin and copolymer resin and dry them at 80 - 85 °C for 4 - 5 h. Add the dried polystyrene resin, copolymer resin, antioxidant, zinc stearate, and calcium carbonate into a high-speed mixer, mix at 500 - 600 rpm for 10 - 20 min until homogeneous, then feed them into a twin-screw extruder for sectional heating and extrusion. Inject a foaming agent into the melting section through a high-pressure metering pump, with a pressure of 8 - 12 MPa. After the molten material is extruded through the die head, it rapidly decompresses and expands to form a closed-cell structure;

[0018] A2. Rapidly cool it to below 60 °C through a cooling roll and a shaping die, conduct corona treatment with a power of 4.5 - 5 kW and a speed of 5 - 6 m / min, and then cut to obtain the extruded board.

[0019] Furthermore, in step A1, the L / D of the twin-screw extruder is 40:1, the screw diameter is 110 - 120 mm, and the sectional heating is specifically as follows: feeding section: 180 - 200 °C, compression section: 200 - 220 °C, melting section: 220 - 240 °C, die head section: 180 - 200 °C, the screw speed is 200 - 300 rpm, and the extrusion speed is 1 - 2 m / min.

[0020] Advantages of the present invention:

[0021] 1. In the technical solution of the present invention, the amphiphilic gradient block molecular chain (polybutylene adipate - polymalic acid copolymer) forms a microphase separation structure through the gradient distribution of hydrophobic - hydrophilic units. The polybutylene adipate chain segment provides good flexibility, while the polymalic acid chain segment increases the rigidity of the molecular chain. The polybutylene adipate chain segment (hydrophobic chain segment) is compatible with the polystyrene matrix through van der Waals forces, and the β-hydroxycarboxylic acid groups of the polymalic acid chain segment (hydrophilic chain segment) form a dynamic cross-linked network through hydrogen bonds, significantly improving the impact toughness of the material. At the same time, the chelation cross-linked network of sodium alginate and calcium ions forms an interfacial interpenetrating structure with the copolymer, making the stress distribution more uniform when the board is punched or cut.

[0022] 2. In the technical solution of the present invention, the bonding performance and interfacial bonding ability of the extruded board are significantly improved. When using a polyurethane-modified adhesive, the isocyanate groups (-NCO) in its molecular chain react with the hydroxyl groups (-OH) on the surface of the extruded board to form a covalent bond, resulting in no hollowing or peeling phenomenon in the bonding layer.

[0023] 3. In the technical solution of the present invention, during the emulsification process, the copolymer solution is sheared into tiny droplets and dispersed in the continuous phase to form multi-level pores, improving the air permeability of the extruded board. An alginate-calcium ion cross-linked layer is introduced. When the humidity is relatively high, the carboxylic acid groups dissociate to form hydrophilic channels, accelerating the diffusion of water vapor; when the humidity is relatively low, the closed-cell structure is restored to avoid condensation.

[0024] 4. In the technical solution of the present invention, both the polybutylene adipate and the poly(malic acid) segment in the copolymer resin belong to aliphatic polyesters, having good biodegradability, which helps to reduce the generation of waste, improve the utilization efficiency of resources, and reduce environmental pollution and waste of resources. Detailed implementation manners

[0025] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts fall within the protection scope of the present invention.

[0026] Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0027] Preparation Example 1

[0028] The copolymer resin is prepared through the following steps:

[0029] S1. Add 1 kg of adipic acid, 0.75 kg of butanediol, and 0.8 kg of L-malic acid to a reactor, protect with nitrogen, control the temperature at 150 °C, stir and react for 2 h, add 0.02 kg of tetrabutyl titanate, raise the temperature to 210 °C, increase the vacuum degree to 8 Pa, and react for 4 h. After the reaction is completed, pour the molten copolymer into a polytetrafluoroethylene mold to cool, crush it into particles, wash with methanol, and vacuum dry at 60 °C to constant weight to obtain polybutylene adipate-poly(malic acid) copolymer particles;

[0030] S2. Add 0.25 kg of copolymer particles to 4.5 kg of dimethyl sulfoxide, stir at 55 °C for 2 h until completely dissolved to obtain Solution A. Add 0.5 kg of sodium alginate to 5 kg of water, stir at 40 °C for 1 h until fully swollen to obtain Solution B. Slowly drip Solution B into Solution A, shear and emulsify at a speed of 5000 rpm for 10 min. Add 0.2 kg of calcium chloride to 1 kg of water to prepare an aqueous calcium chloride solution, drip 15 wt% aqueous calcium chloride solution, continue to stir for 2 h, then pour the composite emulsion into water to precipitate the resin, let it stand for 1 - 2 h, filter, wash, and dry to obtain white porous copolymer resin.

[0031] Preparation Example 2

[0032] The copolymer resin is prepared through the following steps:

[0033] S1. Add 1.05 kg of adipic acid, 0.78 kg of butanediol, and 0.85 kg of L - malic acid into a reactor, protect with nitrogen, control the temperature at 155 °C, stir and react for 2.5 h, add 0.025 kg of tetrabutyl titanate, raise the temperature to 215 °C, increase the vacuum degree to 8 Pa, react for 4.5 h. After the reaction ends, pour the molten copolymer into a polytetrafluoroethylene mold to cool, crush it into particles, wash with methanol, and vacuum - dry at 60 °C until constant weight to obtain poly(butylene adipate) - poly(malic acid) copolymer particles;

[0034] S2. Add 0.28 kg of copolymer particles into 4.7 kg of dimethyl sulfoxide, stir at 57 °C for 2.5 h until completely dissolved to obtain solution A. Add 0.55 kg of sodium alginate into 5.5 kg of water, stir at 42 °C for 1.5 h until fully swollen to obtain solution B. Slowly drip solution B into solution A, shear - emulsify at a speed of 5500 rpm for 12 min. Prepare an aqueous calcium chloride solution by adding 0.25 kg of calcium chloride into 1.25 kg of water, drip 15.5 wt% aqueous calcium chloride solution, continue to stir for 2.5 h, then pour the composite emulsion into water to precipitate the resin, let it stand for 1.5 h, filter, wash, and dry to obtain a white porous copolymer resin.

[0035] Preparation Example 3

[0036] The copolymer resin is prepared through the following steps:

[0037] S1. Add 1.1 kg of adipic acid, 0.8 kg of butanediol, and 0.9 kg of L - malic acid into a reactor, protect with nitrogen, control the temperature at 160 °C, stir and react for 3 h, add 0.03 kg of tetrabutyl titanate, raise the temperature to 220 °C, increase the vacuum degree to 8 Pa, react for 5 h. After the reaction ends, pour the molten copolymer into a polytetrafluoroethylene mold to cool, crush it into particles, wash with methanol, and vacuum - dry at 60 °C until constant weight to obtain poly(butylene adipate) - poly(malic acid) copolymer particles;

[0038] S2. Add 0.3 kg of copolymer particles into 5 kg of dimethyl sulfoxide, stir at 60 °C for 2 - 3 h until completely dissolved to obtain solution A. Add 0.6 kg of sodium alginate into 6 kg of water, stir at 45 °C for 2 h until fully swollen to obtain solution B. Slowly drip solution B into solution A, shear - emulsify at a speed of 6000 rpm for 15 min. Prepare an aqueous calcium chloride solution by adding 0.3 kg of calcium chloride into 1.5 kg of water, drip 16 wt% aqueous calcium chloride solution, continue to stir for 3 h, then pour the composite emulsion into water to precipitate the resin, let it stand for 2 h, filter, wash, and dry to obtain a white porous copolymer resin.

[0039] Example 1

[0040] A method for preparing an extruded board, comprising the following steps:

[0041] A1. Weigh 60 parts of polystyrene resin and 30 parts of the copolymer resin prepared in Preparation Example 1, and dry them at 80 °C for 4 h. Then add the dried 60 parts of polystyrene resin, 30 parts of the copolymer resin prepared in Preparation Example 1, 0.5 part of pentaerythritol tetra[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], 1 part of zinc stearate, and 0.2 part of calcium carbonate into a high-speed mixer, mix at 500 rpm for 10 min until homogeneous, and feed them into a twin-screw extruder with a length-diameter ratio (L / D) of 40:1 and a screw diameter of 110 mm. The twin-screw extruder is divided into a feeding section, a compression section, a melting section, and a die head section. The temperature settings for each section are as follows: feeding section: 180 °C, compression section: 200 °C, melting section: 220 °C, die head section: 180 °C. Heat and extrude in zones, inject 5 parts of cyclopentane into the melting section through a high-pressure metering pump at a pressure of 8 MPa. After the molten material is extruded through the die head, it is quickly decompressed and expanded to form a closed-cell structure;

[0042] A2. Quickly cool to 50 °C through a cooling roll and a shaping die, perform corona treatment with a power of 4.5 kW and a speed of 5 m / min, and cut to obtain the extruded board.

[0043] Example 2

[0044] A method for preparing an extruded board, comprising the following steps:

[0045] A1. Weigh 65 parts of polystyrene resin and 35 parts of the copolymer resin prepared in Preparation Example 2, and dry them at 82 °C for 4.5 h. Then add the dried 65 parts of polystyrene resin, 35 parts of the copolymer resin prepared in Preparation Example 2, 0.6 part of 2,6-di-tert-butyl-p-cresol, 1.5 parts of zinc stearate, and 0.4 part of calcium carbonate into a high-speed mixer, mix at 550 rpm for 15 min until homogeneous, and feed them into a twin-screw extruder with a length-diameter ratio (L / D) of 40:1 and a screw diameter of 115 mm. The twin-screw extruder is divided into a feeding section, a compression section, a melting section, and a die head section. The temperature settings for each section are as follows: feeding section: 190 °C, compression section: 210 °C, melting section: 230 °C, die head section: 190 °C. Heat and extrude in zones, inject 8 parts of azodicarbonamide into the melting section through a high-pressure metering pump at a pressure of 10 MPa. After the molten material is extruded through the die head, it is quickly decompressed and expanded to form a closed-cell structure;

[0046] A2. Quickly cool to 50 °C through a cooling roll and a shaping die, perform corona treatment with a power of 4.8 kW and a speed of 5.5 m / min, and cut to obtain the extruded board.

[0047] Example 3

[0048] A method for preparing an extruded board, comprising the following steps:

[0049] A1. Weigh 70 parts of polystyrene resin and 40 parts of the copolymer resin prepared in Preparation Example 3 and dry them at 85°C for 5 hours. Then add the dried 70 parts of polystyrene resin, 40 parts of the copolymer resin prepared in Preparation Example 3, 0.8 part of tris(2,4-di-tert-butylphenyl) phosphite, 2 parts of zinc stearate, and 0.5 part of calcium carbonate into a high-speed mixer, mix at 600 rpm for 20 minutes until homogeneous, and feed them into a twin-screw extruder with a length-to-diameter ratio (L / D) of 40:1 and a screw diameter of 120 mm. The twin-screw extruder is divided into a feeding section, a compression section, a melting section, and a die head section. The temperature settings for each section are as follows: feeding section: 200°C, compression section: 220°C, melting section: 240°C, die head section: 200°C. Heat and extrude in zones, inject 10 parts of sodium bicarbonate into the melting section through a high-pressure metering pump at a pressure of 12 MPa. After the molten material is extruded through the die head, it is rapidly depressurized and expanded to form a closed-cell structure;

[0050] A2. Rapidly cool to 50°C through a cooling roll and a shaping die, perform corona treatment with a power of 5 kW and a speed of 6 m / min, and cut to obtain an extruded board.

[0051] Comparative Example 1

[0052] The difference between this comparative example and Example 1 is that polybutylene adipate is used instead of the copolymer resin, and the other steps are the same as those in Example 1.

[0053] Comparative Example 2

[0054] The difference between this comparative example and Example 2 is that poly(malic acid) is used instead of the copolymer resin, and the other steps are the same as those in Example 2.

[0055] Comparative Example 3

[0056] The difference between this comparative example and Example 3 is that polystyrene is used instead of the copolymer resin, and the other steps are the same as those in Example 3.

[0057] (Ⅰ) Compressive strength test: Refer to GB / T 8813-2020 "Determination of Compressive Properties of Rigid Cellular Plastics" to prepare specimens of Examples 1-3 and Comparative Examples 1-3 respectively. Condition them in an environment of 23±2°C and 50±5% RH for 88 hours. Set the loading rate of a universal testing machine (Instron 5967) to 2 mm / min, adjust the compression plate spacing to the initial thickness of the specimen, place the specimen in the center, compress it at a constant rate to 10% deformation, record the maximum load, and calculate the compressive strength d m , Compressive strength = Maximum load / Initial cross-sectional area. The results are shown in Table 1:

[0058] Table 1. Compressive strength test results of Examples 1-3 and Comparative Examples 1-3

[0059] Sample Maximum Load (kN) <![CDATA[Initial cross-sectional area (cm 2 )]]> <![CDATA[d m (kPa)]]> Example 1 4.81 25 192.4 Example 2 4.86 25 194.4 Example 3 4.92 25 196.8 Comparative Example 1 3.14 25 125.6 Comparative Example 2 2.85 25 114.0 Comparative Example 3 3.36 25 134.4

[0060] (Ⅱ) Flexural strength test: Referring to ISO 178 "Plastics - Determination of flexural properties", specimens (80×20×4 mm) of Examples 1-3 and Comparative Examples 1-3 were prepared respectively. The support roller spacing of the universal material testing machine (KZ-DSC-20, equipped with a three-point bending fixture) was set to 200 mm, the loading rate was 1 mm / min, the displacement gauge was fixed below the midpoint of the specimen, and it was conditioned for 48 h in an environment of 23±2°C and 50±5% RH.

[0061] Place the specimen centered on the three-point bending fixture, apply a 5 N initial load for preloading, zero the displacement gauge, and apply the load at a uniform rate of 1 mm / min until the specimen breaks, record the maximum load (F m ), and calculate the flexural strength (σ f ), where L = 200 mm, b is the specimen width, h is the specimen thickness, and the results are shown in Table 2:

[0062] Table 2. Flexural strength test results of Examples 1-3 and Comparative Examples 1-3

[0063] Sample Maximum Load (N) Bending Strength (MPa) Example 1 385 56.4 Example 2 389 57.7 Example 3 397 58.9 Comparative Example 1 233 34.6 Comparative Example 2 214 31.8 Comparative Example 3 258 38.3

[0064] (Ⅲ) Water vapor permeability test: Referring to GB / T 17146-2015 "Test method for water vapor transmission properties of building materials and products", circular specimens with a diameter of 70 mm and a thickness of 32 mm of Examples 1-3 and Comparative Examples 1-3 were prepared respectively, and they were conditioned for 48 h in an environment of 23±2°C and 50±5% RH. Put anhydrous calcium chloride in the moisture permeation cup of the cup method water vapor transmission rate tester (WVTR-RC6), cover the cup mouth with each specimen and seal it with wax, the distance between the specimen and the desiccant is 6 mm, set the temperature to 38°C±0.5°C and the relative humidity to 90%±2% RH (high humidity side) vs. dry side, conduct the test for 1 h, and calculate the water vapor permeability (WVP), where Δm is the mass increment of the moisture permeation cup (g), d is the specimen thickness (m), A is the effective area of the specimen (m 2 ), t is the test time (s), and ΔP is the water vapor pressure difference (Pa). The results are shown in Table 3:

[0065] Table 3. Water vapor permeability test results of Examples 1-3 and Comparative Examples 1-3

[0066]

[0067]

[0068] As can be seen from Table 1 and Table 2, the compressive strengths (192.4–196.8 kPa) and flexural strengths (56.4–58.9 MPa) of Examples 1-3 are significantly higher than those of the comparative examples (compressive strength 114.0–134.4 kPa, flexural strength 31.8–38.3 MPa). The examples use poly(butylene adipate)-poly(malic acid) copolymer (PBA-PLA), while the comparative examples use single polymers (such as polystyrene, poly(butylene adipate) or poly(malic acid)).

[0069] In the PBA-PLA copolymer, poly(butylene adipate) (hydrophobic segment) may be compatible with the polystyrene matrix through van der Waals forces, providing flexibility; the β-hydroxycarboxylic acid groups of poly(malic acid) (hydrophilic segment) may form a dynamic cross-linked network through hydrogen bonds, enhancing rigidity. The carboxylic acid groups of poly(malic acid) and the hydroxyl groups of sodium alginate may form hydrogen bonds, further forming an interfacial interpenetrating network to disperse stress, possibly avoiding fracture caused by stress concentration, while Comparative Examples 1-3 may have performance degradation due to the lack of such effects in single polymers.

[0070] In the preparation step of Preparation Example S2, sodium alginate and calcium chloride form a three-dimensional network structure through ionic cross-linking and are embedded in the copolymer matrix, possibly forming a physical reinforcement phase. The examples form a uniform closed-cell structure through high-pressure foaming, which may reduce open-cell defects. The closed-cell structure disperses the compressive load and improves the anti-deformation ability. While in the comparative examples, due to the poor foaming compatibility of single polymers (pure polystyrene in Comparative Example 3), the open-cell rate is relatively high and the strength decreases.

[0071] As can be seen from Table 3, the WVPs (4.26–4.65 ng / Pa·s·m) of Examples 1-3 are much lower than those of the comparative examples (9.68–10.84 ng / Pa·s·m). The polar carboxylic acid groups of poly(malic acid) may form hydrogen bonds with water molecules, delaying the water vapor diffusion path. At the same time, the regularity of the copolymer molecular chains may reduce the molecular gaps and lower the permeation channels. When the humidity is relatively high, the carboxylic acid groups of the sodium alginate-calcium ion cross-linked network dissociate to form hydrophilic channels, which may accelerate the water vapor diffusion (preventing dew condensation); when the humidity is relatively low, the closed-cell structure is restored to block water vapor. While the comparative examples may lack such a dynamic response mechanism and have a higher permeability. The examples precisely control the injection of the blowing agent through a high-pressure metering pump to form uniform closed cells, while in the comparative examples, due to the poor compatibility of the blowing agent with single polymers (poly(butylene adipate) and cyclopentane in Comparative Example 1 may be incompatible), the number of connected pores increases and the permeability rises.

[0072] In Comparative Example 1, the rigid chain segments and hydrogen bond cross-linking network of poly(malic acid) may be lacking, resulting in excessive flexibility of the molecular chains and easy plastic deformation during compression (the compressive strength is only 125.6 kPa). In Comparative Example 2, excessive carboxylic acid groups may lead to over-crosslinking of the molecular chains, forming a brittle structure (the flexural strength is 31.8 MPa), and the strong hydrophilicity causes a further decrease in strength after moisture absorption.

[0073] Comparative Example 3 has poor compatibility with sodium alginate. Phase separation may cause interfacial defects, and the low closed cell rate (WVP = 10.07 ng / Pa·s·m)) leads to deterioration of both mechanical properties and barrier properties.

[0074] In summary, through the gradient chain segment design of the amphiphilic copolymer and the sodium alginate-calcium ion cross-linking network, the compressive strength and flexural strength of the examples are improved, and the extruded boards prepared have good rigidity and anti-deformation ability. At the same time, the water vapor permeability of the examples is more than 60% lower than that of the comparative examples, indicating that the extruded boards prepared in the examples can effectively balance the requirements of barrier and breathability.

[0075] In the description of the specification, the descriptions referring to terms such as "preparation example", "example", "each example", etc. mean that the specific features, structures, materials or characteristics described in connection with that example or preparation example are included in at least one example or preparation example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same example or preparation example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more examples or preparation examples.

[0076] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution of the present invention and its inventive concept, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. An extruded board, characterized in that: The invention comprises the following raw materials by weight: 60-70 parts of polystyrene resin, 30-40 parts of copolymer resin, 5-10 parts of foaming agent, 0.5-0.8 parts of antioxidant, 1-2 parts of zinc stearate and 0.2-0.5 parts of calcium carbonate.

2. An extruded board according to claim 1, characterized in that: The blowing agent includes one or more of azodicarbonamide, sodium bicarbonate, azobisisobutyronitrile and cyclopentane.

3. An extruded board according to claim 1, characterized in that: The antioxidant includes one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 2,6-di-tert-butyl-p-cresol, tris(2,4-di-tert-butylphenyl)phosphite, dilauryl thiodipropionate and N,N'-diphenyl-p-phenylenediamine.

4. An extruded board according to claim 1, characterized in that: The copolymer resin is prepared by the following steps: S1. Add adipic acid, butanediol and L-malic acid into a reactor, pass nitrogen protection, control the temperature, stir and react for 2-3 hours, add tetrabutyl titanate, increase the temperature, increase the vacuum degree, and react for 4-5 hours. After the reaction, pour the molten copolymer into a polytetrafluoroethylene mold, cool it, crush it into particles, wash it with methanol, and vacuum dry it to constant weight to obtain polybutylene adipate-polymalic acid copolymer particles; S2. Add the copolymer particles into dimethyl sulfoxide, stir at 55-60°C for 2-3h to obtain solution A, add sodium alginate into water, stir at 40-45°C for 1-2h to obtain solution B, slowly drip solution B into solution A, shear emulsify, add calcium chloride aqueous solution, continue stirring for 2-3h, pour the composite emulsion into water to precipitate the resin, let it stand for 1-2h, filter, wash and dry to obtain the copolymer resin.

5. An extruded board according to claim 4, characterized in that: The mass ratio of adipic acid, butanediol, L-malic acid and tetrabutyl titanate in step S1 is (10-11): (7.5-8): (8-9): (0.2-0.3).

6. An extruded board according to claim 4, characterized in that: In step S2, the mass ratio of copolymer particles to dimethyl sulfoxide is (2.5-3): (45-50), the mass ratio of sodium alginate to water is (5-6): (50-60), the mass ratio of calcium chloride to water in the calcium chloride aqueous solution is (2-3): (10-15), and the addition amount is 15-16wt%.

7. An extruded board according to claim 4, characterized in that: In step S1, the temperature is controlled at 150-160°C, the temperature is increased to 210-220°C, and the vacuum degree is increased to <10Pa.

8. An extruded board according to claim 4, characterized in that: In step S2, the shearing speed is 5000-6000 rpm, and the emulsification time is 10-15 min.

9. A method for preparing an extruded board according to any one of claims 1 to 8, characterized in that: The following steps are involved: A1. Dry the polystyrene resin and copolymer resin at 80-85°C for 4-5h by weight, add the dried polystyrene resin, copolymer resin, antioxidant, zinc stearate and calcium carbonate into a high-speed mixer, mix for 10-20min until uniform, feed into a twin-screw extruder, heat and extrude in different zones, and inject a foaming agent during the extrusion process; A2. Rapidly cool to below 60°C through cooling rollers and shaping dies, perform corona treatment, and cut to obtain an extruded board.

10. The method for preparing an extruded board according to claim 9, characterized in that: In step A1, the twin-screw extruder has L / D=40:1, a screw diameter of 110-120 mm, and zone heating is specifically as follows: feeding section: 180-200°C, compression section: 200-220°C, melting section: 220-240°C, die section: 180-200°C, screw speed of 200-300 rpm, and extrusion speed of 1-2 m / min.

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