A halogen-free flame-retardant and low-warpage polypropylene lock floor substrate and its preparation method

Abstract

The present invention belongs to the technical field of floor substrates, and particularly relates to a halogen-free flame-retardant and low-warpage polypropylene lock floor substrate and a preparation method thereof. The polypropylene lock floor substrate provided by the present invention is mainly prepared by extrusion after mixing calcium carbonate, polypropylene resin, lignin, nucleating agent, toughening agent, flame retardant, lubricant, and antioxidant. Among them, the polypropylene lock floor substrate of the present invention uses calcium carbonate as the stone powder aggregate, and uses a polypropylene resin compounded by homopolypropylene and copolymerized polypropylene to replace the traditional polyvinyl chloride resin. Further, lignin is introduced as a charring agent and a flame retardant synergist, which can effectively improve the mechanical properties, dimensional stability, and flame retardant properties of the polypropylene floor. Compared with the existing plastic floors, the lock floor prepared from the floor substrate of the present invention has the advantages of low warpage, not easy to crack and shrink, not easy to arch and deform, and halogen-free flame retardancy, and has extremely broad application potential in the field of high-quality lock floor preparation.

Description

Technical Field

[0001] The present invention belongs to the technical field of floor substrates, and particularly relates to a halogen-free flame-retardant and low-warpage polypropylene lock-floor substrate and a preparation method thereof. Background Art

[0002] Lock-floor is a type of floor that has been popular in recent years. It is connected by dovetail joints around the floor in an interlocking manner, and can be assembled into an integral structural form without any laying conditions. Lock-floor combines the performance characteristics of wood and plastic, and does not require the use of nails and glue during installation, which is environmentally friendly and easy to disassemble. It can also be designed with different patterns according to the decoration effect to meet the usage requirements of different occasions and tastes, and is deeply loved by consumers. At present, it has been widely used in home decoration, commercial offices, entertainment venues, etc.

[0003] Lock-floor usually consists of a floor substrate and an auxiliary functional layer. The floor substrate is the core component of the lock-floor. It is a composite board made by uniformly mixing stone powder and thermoplastic polymer materials and then extruding them at high temperature. The quality of the performance of the floor substrate also largely determines the service life of the lock-floor.

[0004] At present, the most common lock-floor for indoor laying on the market is the floor with a polyvinyl chloride (PVC) substrate. PVC floors are widely used in household or commercial places because of their good flame retardancy, good dimensional stability, rich color patterns and low price. However, the PVC molecular structure in the PVC floor substrate contains chlorine atoms, and toxic gases such as hydrogen chloride and dioxin will be generated during the forming process and combustion process. Moreover, PVC floors usually require a large amount of plasticizers such as dioctyl terephthalate (DOTP) to be added, which has a greater impact on the environment. With the rapid development of society, people's environmental protection requirements for indoor flooring materials are getting higher and higher, which also restricts the further application of PVC-based lock-floors. In addition, after long-term use, lock-floors will inevitably show phenomena such as cracking, warping, shrinking, arching and deformation.

[0005] Therefore, how to develop a new type of lock-floor substrate to meet the development needs of lock-floors for environmental protection, and at the same time comprehensively improve the defects such as cracking, warping, shrinking, arching and deformation of lock-floors has become an urgent technical problem to be solved. Summary of the Invention

[0006] To overcome the deficiencies in the prior art, the purpose of the present invention is to provide a halogen-free flame-retardant and low-warpage polypropylene lock-floor substrate. The lock-floor prepared from this substrate is not only green and environmentally friendly, has good dimensional stability and flame-retardant performance, but also can effectively improve defects such as floor cracking, warping, shrinking, and arching deformation, meeting the development requirements of high-quality lock-floors in the flooring field.

[0007] The purpose of the present invention is also to provide a preparation method for the above-mentioned halogen-free flame-retardant and low-warpage polypropylene lock-floor substrate.

[0008] To achieve the above purpose, the technical solution adopted by the present invention is:

[0009] A halogen-free flame-retardant and low-warpage polypropylene lock-floor substrate is prepared by mixing and extruding raw materials including the following parts by mass: 200 - 400 parts of calcium carbonate, 80 - 120 parts of polypropylene resin, 10 - 30 parts of lignin, 0.2 - 2 parts of nucleating agent, 10 - 20 parts of toughening agent, 20 - 40 parts of flame retardant, 2 - 5 parts of lubricant, and 1 - 3 parts of antioxidant;

[0010] Among them, the polypropylene resin is a blend of homopolypropylene and copolymerized polypropylene; the flame retardant is a blend of piperazine pyrophosphate and polysiloxane.

[0011] Further, to improve the stability of the substrate, the melt index of the homopolypropylene is 1.7 - 2.7 g / 10min; the melt index of the copolymerized polypropylene is 1.5 - 2.5 g / 10min.

[0012] Further, the mass ratio of homopolypropylene to copolymerized polypropylene is 1:(0.8 - 1.2), more preferably 1:1.

[0013] Further, the nucleating agent is one or more of 2,2′-methylene-bis(4,6-di-tert-butylphenol) phosphonate aluminum salt, dibenzylidene sorbitol, sodium benzoate, talcum powder, carbon black.

[0014] Further, the toughening agent is one or more of ethylene propylene diene monomer (EPDM), styrene-butadiene-styrene block copolymer (SBS), polyolefin elastomer (POE), ethylene-vinyl acetate copolymer (EVA).

[0015] Further, the polysiloxane is one or more of hydroxyphenyl silsesquioxane, phenyl silsesquioxane, ladder silsesquioxane.

[0016] Further, the particle size of the lignin is 100 - 400 mesh; the particle size of the calcium carbonate is 400 - 800 mesh.

[0017] Further, the lubricant is one or more of polyethylene wax, polypropylene wax, montan wax, and zinc stearate; the antioxidant is one or more of hindered phenols, aromatic amines, phosphite esters, and sulfur-containing esters.

[0018] The preparation method of the halogen-free flame-retardant and low-warpage polypropylene lock floor substrate includes the following steps:

[0019] (1) Mix calcium carbonate, polypropylene resin, lignin, nucleating agent, toughening agent, flame retardant, lubricant, and antioxidant according to the mass parts of the raw materials, and then place them at a temperature of 100-150°C for mixing to obtain a substrate mixture.

[0020] (2) Extrude and mold the substrate mixture to obtain a halogen-free flame-retardant and low-warpage polypropylene lock floor substrate.

[0021] Further, the mixing time is 10-20 min.

[0022] Further, the extrusion molding process is as follows: the temperature of the first zone of the mold is 172-177°C, the temperature of the second zone is 175-182°C, the temperature of the third zone is 180-190°C, the temperature of the fourth zone is 175-182°C, and the temperature of the fifth zone is 172-177°C; the temperature of the first zone of the extruder barrel is 170-175°C, the temperature of the second zone is 165-170°C, the temperature of the third zone is 158-160°C, the temperature of the fourth zone is 150-155°C, the temperature of the fifth zone is 148-153°C, the temperature of the sixth zone is 145-150°C; the main machine current is 205-215 A; the feeding speed is 280-400 kg / h; the main machine speed is 300-350 rpm; the extrusion pressure is 3-6 MPa; the extrusion speed is 100-140 kg / h.

[0023] The advantages and beneficial effects of the technical solution of the present invention are:

[0024] The polypropylene lock floor substrate provided by the present invention is mainly prepared by mixing calcium carbonate, polypropylene resin, lignin, nucleating agent, toughening agent, flame retardant, lubricant, and antioxidant and then extruding.

[0025] Among them, the floor substrate provided by the present invention uses calcium carbonate as the stone powder aggregate, and uses a polypropylene resin compounded by homopolypropylene (homo-PP) and copolymer polypropylene (copoly-PP) to replace the traditional polyvinyl chloride resin. The present invention uses a mixture of copolymer PP and homopolypropylene to promote the balance of material rigidity and toughness and reduce costs. Further introduce lignin as a charring agent and a flame retardant synergist. Lignin can form a fiber structure in the material to prevent the material from deforming and cracking. In addition, the benzene ring skeleton in the lignin structure enables it to produce a relatively high amount of residual carbon during the combustion process. The rich hydroxyl groups promote the charring reaction, improve the thermal stability and charring property of the material, thereby effectively improving the mechanical properties, dimensional stability and flame retardant properties of the polypropylene floor.

[0026] Compared with the existing plastic floors, the lock catch floor prepared from the floor substrate of the present invention has the advantages of low warping, not easy to crack and shrink, not easy to arch and deform, and halogen-free flame retardant, and has extremely broad development prospects and huge application potential in the field of preparing high-quality lock catch floors. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a cross-sectional schematic diagram of a lock catch floor product prepared from the halogen-free flame retardant and low warping polypropylene lock catch floor substrate of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] In order to make the above-mentioned technical solutions of the present invention more obvious and understandable in terms of purpose, features and advantages, the following specific embodiments are used to describe the specific implementation manners of the present invention in detail. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make equivalent replacements without departing from the connotation of the present invention. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0029] Unless otherwise specified, the test methods used in the following examples are all conventional methods; unless otherwise specified, the raw materials used are all commonly used in the art, publicly available or commercially available items.

[0030] In the following embodiments of the present invention, a halogen-free flame retardant and low warping polypropylene lock catch floor substrate is provided, which is prepared by mixing and extruding the following raw materials in parts by mass: 200-400 parts of calcium carbonate, 80-120 parts of polypropylene resin, 10-30 parts of lignin, 0.2-2 parts of nucleating agent, 10-20 parts of toughening agent, 20-40 parts of flame retardant, 2-5 parts of lubricant, 1-3 parts of antioxidant; wherein, the polypropylene resin is a blend of homopolypropylene and copolymer polypropylene; the flame retardant is a blend of piperazine pyrophosphate and polysiloxane.

[0031] Furthermore, the melt index of homopolypropylene is 1.7-2.7 g / 10 min; the melt index of copolymer polypropylene is 1.5-2.5 g / 10 min. The melt indexes of homopolypropylene and copolymer polypropylene used in the following examples meet the above requirements and are specifically from Kingfa Science & Technology Co., Ltd.

[0032] Furthermore, the mass ratio of homopolypropylene to copolymer polypropylene is 1:(0.8-1.2), more preferably 1:1.

[0033] Further, the nucleating agent is one or more of 2,2′-methylene-bis(4,6-tert-butylphenol)phosphine aluminum salt (hereinafter referred to as NA-21), dibenzylidene sorbitol, sodium benzoate, talc, and carbon black. Specifically, the nucleating agent used in the following examples is NA-21, which comes from Shanghai Qirun New Materials Co., Ltd.

[0034] Further, the toughening agent is one or more of EPDM rubber, styrene-butadiene-styrene block copolymer, polyolefin elastomer, and ethylene-vinyl acetate copolymer. Specifically, the toughening agent used in the following examples is EPDM rubber from Dow Chemical.

[0035] Further, the polysiloxane is one or more of hydroxyphenyl ladder silsesquioxane, phenyl silsesquioxane, and ladder silsesquioxane. Specifically, the hydroxyphenyl ladder silsesquioxane used in the following examples is SIFR-SI907, the phenyl silsesquioxane is SIFR-SI908, and the ladder silsesquioxane is SIFR-770N, all of which are from Quansheng Polycarbon Technology Co., Ltd.

[0036] Furthermore, the particle size of lignin is 100-400 meshes, and the particle size of calcium carbonate is 400-800 meshes. Specifically, the lignin used in the following examples comes from Wuhan Jiyesheng Chemical Co., Ltd.

[0037] Further, the lubricant is one or more of polyethylene wax, polypropylene wax, montan wax, and zinc stearate; the antioxidant is one or more of hindered phenols, aromatic amines, phosphites, and sulfur-containing esters. Specifically, the lubricant used in the following examples is polyethylene wax, which comes from Xingbeida Chemical Materials Co., Ltd. The antioxidant used in the following examples is antioxidant 1010, which comes from Tianjin Lianlong New Materials Co., Ltd.

[0038] Example 1

[0039] This embodiment provides a halogen-free, flame-retardant, low-warping polypropylene lock floor substrate, which is prepared by mixing and extruding the following raw materials in parts by weight: 300 parts of calcium carbonate, 100 parts of polypropylene resin, 15 parts of lignin, 1 part of nucleating agent, 15 parts of toughening agent, 25 parts of flame retardant, 3 parts of lubricant, and 2 parts of antioxidant.

[0040] Among them, the polypropylene resin is a blend of homopolypropylene and copolymerized polypropylene with a mass ratio of 1:1. The nucleating agent is aluminum 2,2'-methylene-bis(4,6-di-tert-butylphenol) phosphonate (NA-21). The toughening agent is ethylene-propylene-diene monomer rubber (model 722P). The flame retardant consists of 20 parts of piperazine pyrophosphate and 5 parts of polysiloxane. The polysiloxane is specifically hydroxy phenyl ladder polysilsesquioxane (model SIFR-SI907). The lubricant is polyethylene wax. The antioxidant is antioxidant 1010. The particle size of lignin is 100-400 mesh. The particle size of calcium carbonate is 400-800 mesh.

[0041] This embodiment provides a method for preparing the above-mentioned halogen-free flame-retardant and low-warpage polypropylene lock floor substrate, including the following steps:

[0042] S1. Mix the above raw materials according to the mass parts, and then place them in a high-speed mixer for mixing. The mixing temperature is 120°C and the mixing time is 15 min to obtain a PP substrate mixture.

[0043] S2. Extrude and mold the above PP substrate mixture in an extruder to obtain a halogen-free flame-retardant and low-warpage polypropylene lock floor substrate.

[0044] This embodiment also provides a polypropylene lock floor, the cross-sectional schematic diagram of which is as Figure 1 shown, and it sequentially includes from top to bottom: a PP transparent film, a PP color film, a PP substrate, and an IXPP soundproof pad. Among them, the PP substrate is the halogen-free flame-retardant and low-warpage polypropylene lock floor substrate prepared in Example 1 of the present invention. The method for preparing the polypropylene lock floor in this embodiment includes the following steps:

[0045] First, paste the PP color film on the above-prepared halogen-free flame-retardant and low-warpage polypropylene lock floor substrate, and then paste the PP transparent film; then paste an electron beam cross-linked polypropylene (IXPP) soundproof pad under the lock floor substrate, and perform lamination and compounding at a temperature of 35°C and a pressure of 10 MPa. After compounding, place it in a constant temperature room at 32°C for curing for 2 h to obtain a polypropylene floor; further perform an unlocking treatment on the obtained polypropylene floor to obtain a polypropylene lock floor.

[0046] In this embodiment, when preparing the polypropylene lock floor substrate, the equipment used for extrusion molding is a twin-screw extruder with a diameter of 110 mm. Since parameters such as temperature, pressure, and time in the extrusion molding process have an important impact on the final quality of the floor material. Different extrusion process parameters may cause defects such as warping, cracking, and insufficient strength of the material.

[0047] Based on this, in this embodiment, the above-mentioned PP base material mixture is placed in an extruder for extrusion molding. The optimal extrusion molding process obtained through experiments is as follows: the temperature of the first zone of the extruder die is 172 - 177°C, the second zone is 175 - 182°C, the third zone is 180 - 190°C, the fourth zone is 175 - 182°C, and the fifth zone is 172 - 177°C. The temperature of the first zone of the extruder barrel is 170 - 175°C, the second zone is 165 - 170°C, the third zone is 158 - 160°C, the fourth zone is 150 - 155°C, the fifth zone is 148 - 153°C, and the sixth zone is 145 - 150°C. The main machine current is 205 - 215A. The feeding speed is 280 - 400 kg / h. The main machine speed is 300 - 350 rpm. The extrusion pressure is 3 - 6 MPa. The extrusion speed is 100 - 140 kg / h.

[0048] In order to improve the efficiency of the extrusion molding process and obtain the best product performance, the following intelligent control system is adopted to control the extrusion molding process under the above optimal process conditions. The specific control method includes the following steps S1 - S5:

[0049] S1. During the extrusion process, temperature sensors, pressure sensors, current sensors, and speed sensors are installed to collect the temperature of the extruder barrel, die temperature, extrusion pressure, main machine current, and main machine speed in real time, and data preprocessing is carried out, including noise removal and data normalization. It can be understood that the control of pressure is adjusted through the main machine current. Under the condition of the same main machine screw speed, the faster the speed and the higher the main machine current, the greater the relative pressure and the better the plasticization.

[0050] Specifically, Kalman filtering or mean filtering is used to denoise the data, and the data of each sensor is normalized to the range of [0, 1].

[0051] Specifically, the temperature control range of the extruder barrel is: the temperature of the first zone is 170 - 175°C, the second zone is 165 - 170°C, the third zone is 158 - 160°C, the fourth zone is 150 - 155°C, the fifth zone is 148 - 153°C, and the sixth zone is 145 - 150°C. The temperature control range of the extruder die is: the temperature of the first zone is 172 - 177°C, the second zone is 175 - 182°C, the third zone is 180 - 190°C, the fourth zone is 175 - 182°C, and the fifth zone is 172 - 177°C. The extrusion pressure is 3 - 6 MPa. The main machine current is 205 - 215A. The main machine speed is 300 - 350 rpm.

[0052] S12. According to the raw material formula and target performance, set the target value and threshold of the extrusion pressure during the extrusion process to ensure that the pressure fluctuates within a reasonable range, guaranteeing the density and surface smoothness of the finished product. At the same time, set the range of the extrusion speed to ensure uniform thickness and prevent warping or cracking.

[0053] Specifically, the extrusion pressure is 3 - 6 MPa, and the extrusion speed is 100 - 140 kg / h.

[0054] Specifically, according to the characteristics of the material, select a suitable target pressure value, and then set the target extrusion speed based on the stable operating conditions of the extruder and the flow characteristics of the material. According to the target parameter values and process tolerances, set the upper and lower threshold values of the extrusion pressure and extrusion speed, including the pressure threshold and the extrusion speed threshold, to ensure the stability of the extrusion process.

[0055] S13. The fuzzy control algorithm compares the sensor data (such as extrusion pressure, extrusion speed) collected in real time with the set target values to generate a control signal. The fuzzy controller adjusts the extrusion pressure and extrusion speed of the extruder according to the fuzzy rules (for example: "If the pressure is high, then reduce the extrusion speed") to ensure that these parameters are maintained within the preset range.

[0056] Specifically, according to the set target values of the extrusion pressure and extrusion speed and the extrusion pressure and extrusion speed data collected in real time, calculate the current error value and error change rate. The error value includes the extrusion pressure error and the extrusion speed error. Subsequently, perform fuzzy processing on the error value and the error change rate, converting them into fuzzy linguistic variables such as high, medium, and low, and the fuzzy processing is completed through the membership function. Then, perform reasoning according to the fuzzy rules (such as "If the extrusion pressure error is high, then increase the extrusion speed"), calculate the fuzzy control output, and finally convert the calculated fuzzy control signal into an actual adjustment signal for subsequent use by the PID controller.

[0057] Among them, the expression of the fuzzy membership function is:

[0058]

[0059] In the formula, μ(eN) is the membership function, and N max is the maximum value of the physical quantity threshold. When it is the maximum pressure threshold, N can be replaced by P, and if it is the maximum speed threshold, N can be replaced by V.

[0060] It is not difficult to understand that the fuzzy rules are consistent with the process control theory in actual production. Generally, if the barrel temperature is too high (higher than the target value +2%), the mold temperature is reduced; if the mold temperature is too low (lower than the target value -2%), the barrel temperature in the corresponding area is increased. In addition, the feeding speed is proportional to the main machine current, and the faster the speed, the greater the extrusion pressure: if the extrusion pressure is high (higher than 6 MPa), the feeding speed is reduced; if the extrusion pressure is low (lower than 3 MPa), the screw rotation speed is increased. For the cycle, if the cycle is too long (longer than 120 seconds), the feeding speed and the main machine rotation speed are increased; if the cycle is too short (shorter than 60 seconds), the main machine rotation speed is appropriately reduced.

[0061] S14. The PID controller further finely adjusts the extrusion pressure and extrusion speed of the extruder according to the adjustment signal output by the fuzzy controller. PID control uses three control means: proportional, integral, and derivative, to eliminate real-time errors, keep the pressure and speed within the optimal range, precisely adjust each parameter in the extrusion process, and thus ensure the uniform thickness and smooth surface of the floor substrate, avoiding quality problems caused by control fluctuations.

[0062] Specifically, according to the adjustment signal output by the fuzzy controller, the error value of the PID controller is calculated, and then the proportional, integral, and derivative terms of the PID controller are calculated based on the error value. Subsequently, the results of the proportional, integral, and derivative terms are comprehensively calculated to obtain the adjustment signal of the PID controller. Finally, the calculated adjustment signal of the PID controller is transmitted to the control system to adjust the pressure and speed of the extruder.

[0063] Among them, the PID signal output expression is:

[0064] u N =N output +I N +D N

[0065] In the formula, u N is the adjustment output signal of the PID controller, N output is the proportional term, I N is the integral term, D N is the derivative term. N refers to the physical quantity, which is the same as above and will not be elaborated here.

[0066] S15. The real-time monitoring system tracks various parameters during the extrusion process. When it detects that the actual data deviates from the set target, the system will automatically feedback an adjustment signal to adjust the extrusion pressure and extrusion speed in real time to ensure that the equipment is always within the optimal process range.

[0067] Specifically, the real-time monitoring system continuously collects key data such as pressure, speed, and humidity through sensors and transmits the values to the control system for analysis. The error between the real-time collected data and the set value of the PID controller is calculated, and the control parameters are adjusted according to this error. The adjusted control parameters are transmitted to the PID controller for further adjustment.

[0068] Example 2

[0069] This example provides a halogen-free flame-retardant and low-warpage polypropylene lock-floor substrate. Its composition and overall preparation method are basically the same as those of Example 1. The difference between the two is that the flame retardant used in this example is composed of 22.5 parts of piperazine pyrophosphate and 2.5 parts of polysiloxane; the remaining processes and parameters are the same as those of Example 1.

[0070] This example also provides a polypropylene lock-floor. Its preparation method is basically the same as that of Example 1, except that the halogen-free flame-retardant and low-warpage polypropylene lock-floor substrate of Example 2 is used for the preparation of the polypropylene lock-floor.

[0071] Example 3

[0072] This example provides a halogen-free flame-retardant and low-warpage polypropylene lock-floor substrate. Its composition and overall preparation method are basically the same as those of Example 1. The difference between the two is that the flame retardant used in this example is composed of 20 parts of piperazine pyrophosphate and 5 parts of polysiloxane; the polysiloxane is specifically phenylsilsesquioxane (model SIFR-SI908), and the remaining processes are the same as those of Example 1.

[0073] This example also provides a polypropylene lock-floor. Its preparation method is basically the same as that of Example 1, except that the halogen-free flame-retardant and low-warpage polypropylene lock-floor substrate of Example 3 is used for the preparation of the polypropylene lock-floor.

[0074] Example 4

[0075] This example provides a halogen-free flame-retardant and low-warpage polypropylene lock-floor substrate. Its composition and overall preparation method are basically the same as those of Example 1. The difference between the two is that the flame retardant used in this example is composed of 20 parts of piperazine pyrophosphate and 5 parts of polysiloxane; the polysiloxane is specifically ladder-shaped silsesquioxane (model SIFR-770N), and the remaining processes are the same as those of Example 1.

[0076] This example also provides a polypropylene lock-floor. Its preparation method is basically the same as that of Example 1, except that the halogen-free flame-retardant and low-warpage polypropylene lock-floor substrate of Example 4 is used for the preparation of the polypropylene lock-floor.

[0077] Comparative Example 1

[0078] This comparative example provides a polypropylene lock - floor substrate, whose composition and overall preparation method are basically the same as those of Example 1. The difference between the two is that in the raw materials used in this comparative example, both the flame retardant and lignin are omitted, and other conditions and parameters are the same as those in Example 1.

[0079] This comparative example also provides a polypropylene lock - floor. Its overall preparation method is basically the same as that of Example 1. The only difference is that the polypropylene lock - floor substrate of Comparative Example 1 is used for the preparation of the polypropylene lock - floor.

[0080] Comparative Example 2

[0081] This comparative example provides a polypropylene lock - floor substrate, whose composition and overall preparation method are basically the same as those of Example 1. The difference between the two is that in the raw materials used in this comparative example, lignin is omitted, and other conditions and parameters are the same as those in Example 1.

[0082] This comparative example also provides a polypropylene lock - floor. Its preparation method is basically the same as that of Example 1. The only difference is that the polypropylene lock - floor substrate of Comparative Example 2 is used for the preparation of the polypropylene lock - floor.

[0083] Comparative Example 3

[0084] This comparative example provides a polypropylene lock - floor substrate, whose composition and overall preparation method are basically the same as those of Example 1. The difference between the two is that in the raw materials used in this comparative example, the flame retardant is omitted, and other conditions and parameters are the same as those in Example 1.

[0085] This comparative example also provides a polypropylene lock - floor. Its preparation method is basically the same as that of Example 1. The only difference is that the polypropylene lock - floor substrate of Comparative Example 3 is used for the preparation of the polypropylene lock - floor.

[0086] Comparative Example 4

[0087] This comparative example provides a polypropylene lock - floor substrate, whose composition and overall preparation method are basically the same as those of Example 1. The difference between the two is that in this comparative example, 100 parts of homopolypropylene are used to replace the blend of homopolypropylene and copolymer polypropylene in Example 1, and other conditions and parameters are the same as those in Example 1.

[0088] This comparative example also provides a polypropylene lock - floor. Its preparation method is basically the same as that of Example 1. The only difference is that the polypropylene lock - floor substrate of Comparative Example 4 is used for the preparation of the polypropylene lock - floor.

[0089] Comparative Example 5

[0090] This comparative example provides a polypropylene click-lock floor substrate, whose composition and overall preparation method are basically the same as those of Example 1. The difference between the two is that this comparative example uses 100 parts of copolymerized polypropylene to replace the homopolypropylene and copolymerized polypropylene blend in Example 1, and other conditions and parameters are the same as those in Example 1.

[0091] This comparative example also provides a polypropylene click-lock floor. Its overall preparation method is basically the same as that of Example 1. The only difference is that the polypropylene click-lock floor substrate of Comparative Example 5 is used for the preparation of the polypropylene click-lock floor.

[0092] Test Example, Performance Testing of Click-Lock Floors

[0093] This test example tests the performance of the polypropylene click-lock floors prepared in Examples 1 to 4 and Comparative Examples 1 to 5 of the present invention.

[0094] Among them, the warping performance: tested according to the ISO24342 standard: the sample is cut into a 250mm×250mm square, placed on a flat table, and the four corners of the sample are tested one by one with a feeler gauge. The maximum value among the four corners is selected as the test result.

[0095] Thermal shrinkage test: tested according to the ISO24342 standard: the sample is cut into a 250mm×250mm square, and the length and width of the sample are measured (the four sides need to be measured and the data recorded, the length is recorded as L10, L20, and the width is recorded as W10, W20). The sample is placed in an 80°C oven, taken out after 6h and placed in the laboratory to stand for 3h. After standing, the length and width of the sample are tested (the length is recorded as L11, L21, and the width is recorded as W11, W21). Calculate according to the following formula, length: {[(L10 + L20) / 2 - (L11 + L21) / 2] / [(L10 + L20) / 2]}×100%; width: {[(W10 + W20) / 2 - (W11 + W21) / 2] / [(W10 + W20) / 2]}×100%, and the maximum value is selected as the test result.

[0096] Thermal expansion test: Cut a 180mm×1220mm sample and place it in a drying oven. Set the drying oven temperature to 20°C. After the drying oven reaches the set temperature, keep it warm for 3h, and measure the length and width, the length is recorded as L10, L20, and the width is recorded as W10, W20. Then set the drying oven temperature to 70°C. After reaching the set temperature, keep it warm for 3h, and measure the length and width, the length is recorded as L11, L21, and the width is recorded as W11, W21. Calculate the experimental data. The linear thermal expansion coefficient of the length is: {[(L11 + L21) / 2 - (L10 + L20) / 2] / [(L10 + L20) / 2] / 50}×100000; the linear thermal expansion coefficient of the width is: {[(W11 + W21) / 2 - (W10 + W20) / 2] / [(W10 + W20) / 2] / 50}×100000, and the maximum value is selected as the test result.

[0097] Low-temperature ball-drop test: Test according to EN13329 standard. Take a 300mm×250mm sample and place it on the chassis of the ball-drop impact testing machine, and fix it with screws. Use a 2280g ball to drop from a height of 1500mm for impact testing.

[0098] Light exposure test: Cut a 180mm×1220mm sample and place it in the light exposure laboratory. Set the light exposure temperature at 70°C and expose it for 3h.

[0099] Elastic modulus and static bending strength test: Test according to GB / T17657-2013 standard. Cut a 50mm×150mm sample, measure the thickness of the sample, place the sample on the support rollers of the universal mechanical testing machine, and input the sample thickness for testing.

[0100] Flame retardancy performance: Test according to GB / T11785-2005 standard. Cut a 1050mm×230mm sample. First, fix the calibration plate on the platform of the combustion tester for heat flux calibration. After calibration, remove the calibration plate and replace it with the test plate. Ignite the ignition source with a blowtorch. After 120s, move the blowtorch of the ignition source forward to ignite the sample. After 720s, turn off the blowtorch of the ignition source and move it back. After the combustion flame goes out, the combustion tester automatically records the position and calculates the radiant flux.

[0101] The performance test results of the polypropylene lock floors of Examples 1 to 4 and Comparative Examples 1 to 5 are shown in Table 1.

[0102] Table 1. Performance test data of the polypropylene lock floors of Examples 1 to 4 and Comparative Examples 1 to 5

[0103]

[0104]

[0105] As can be seen from Table 1, for the lock floors prepared from the polypropylene base layers of Examples 1 to 4 of the present invention, the warpage is ≤0.98mm, the thermal shrinkage rate is ≤0.09%, the thermal expansion coefficient is ≤6.0×10 -5 , there is no cracking in the ball-drop impact test, no arching in the light exposure test, the elastic modulus is ≥2200MPa, the static bending strength is ≥18MPa, and the radiant flux is ≥8.2kW / m 2 . The comprehensive performance indicators are all superior to those of the lock floors prepared from the base layers of Comparative Examples 1 to 5.

[0106] Based on the above results, it can be seen that the polypropylene lock-floor substrate provided by the present invention is mainly prepared by extrusion after mixing calcium carbonate, polypropylene resin, lignin, nucleating agent, toughening agent, flame retardant, lubricant, and antioxidant. Among them, the floor substrate provided by the present invention uses calcium carbonate as the stone powder aggregate, and uses a polypropylene resin compounded by homopolypropylene and copolymer polypropylene to replace the traditional polyvinyl chloride resin. Further, lignin is introduced as a charring agent and a flame retardant synergist, which can effectively improve the mechanical properties, dimensional stability, and flame retardant properties of the polypropylene floor. Compared with the existing plastic floors, the lock-floor prepared from the floor substrate of the present invention has the advantages of low warping, not easy to crack and shrink, not easy to arch and deform, and halogen-free flame retardancy, and has extremely broad development prospects and huge application potential in the field of preparing high-quality lock-floors.

[0107] It should be noted that although the above embodiments have detailed the technical solutions of the present invention, these embodiments are only illustrative examples rather than restrictive definitions. Those skilled in the art should understand that any modifications or equivalent replacements made without departing from the spirit and scope of the technical solutions of the present invention shall be included within the scope of the claims of the present invention. Therefore, the protection scope of the present invention shall be subject to the content defined by the claims.

Claims

1. A halogen-free, flame-retardant, low-warping polypropylene lock floor substrate, characterized in that: The material is prepared by mixing and extruding the following raw materials in parts by weight: 200-400 parts of calcium carbonate, 80-120 parts of polypropylene resin, 10-30 parts of lignin, 0.2-2 parts of nucleating agent, 10-20 parts of toughening agent, 20-40 parts of flame retardant, 2-5 parts of lubricant, and 1-3 parts of antioxidant; Wherein, the polypropylene resin is a blend of homopolypropylene and copolymer polypropylene; and the flame retardant is a blend of piperazine pyrophosphate and polysiloxane.

2. The halogen-free flame-retardant low-warping polypropylene snap-on floor substrate according to claim 1, characterized in that: The melting index of the homopolypropylene is 1.7-2.7 g / 10 min; the melting index of the copolymer polypropylene is 1.5-2.5 g / 10 min.

3. The halogen-free flame-retardant low-warping polypropylene lock floor substrate according to claim 1, characterized in that: The mass ratio of homopolymer polypropylene to copolymer polypropylene is 1:(0.8~1.2).

4. The halogen-free flame-retardant low-warping polypropylene lock floor substrate according to any one of claims 1 to 3, characterized in that: The nucleating agent is one or more of 2,2′-methylene-bis(4,6-tert-butylphenol)phosphine aluminum salt, dibenzylidene sorbitol, sodium benzoate, talc and carbon black.

5. The halogen-free flame-retardant low-warping polypropylene snap-on floor substrate according to any one of claims 1 to 3, characterized in that: The toughening agent is one or more of ethylene propylene diene monomer rubber, styrene-butadiene-styrene block copolymer, polyolefin elastomer, and ethylene-vinyl acetate copolymer.

6. The halogen-free flame-retardant low-warping polypropylene snap-on floor substrate according to any one of claims 1 to 3, characterized in that: The polysiloxane is one or more of hydroxyphenyl ladder silsesquioxane, phenyl silsesquioxane, and ladder silsesquioxane.

7. The halogen-free flame-retardant low-warping polypropylene snap-on floor substrate according to any one of claims 1 to 3, characterized in that: The particle size of the lignin is 100-400 meshes; the particle size of the calcium carbonate is 400-800 meshes.

8. The halogen-free, flame-retardant, low-warping polypropylene snap-on floor substrate according to any one of claims 1 to 3, characterized in that: The lubricant is one or more of polyethylene wax, polypropylene wax, montan wax and zinc stearate; the antioxidant is one or more of hindered phenols, aromatic amines, phosphites and sulfur-containing esters.

9. A method for preparing a halogen-free, flame-retardant, low-warping polypropylene snap-fit ​​floor substrate according to any one of claims 1 to 8, characterized in that: The following steps are involved: (1) Calcium carbonate, polypropylene resin, lignin, nucleating agent, toughening agent, flame retardant, lubricant and antioxidant are mixed according to the weight proportion of raw materials, and then mixed at a temperature of 100-150° C. to obtain a base material mixture; (2) Extruding the substrate mixture to obtain a halogen-free, flame-retardant, low-warping polypropylene lock floor substrate.

10. The method for preparing the halogen-free flame-retardant low-warping polypropylene snap-fit ​​floor substrate according to claim 9, characterized in that: The mixing time is 10-20 min; the extrusion molding process is as follows: the temperature of the first zone of the mold is 172-177° C., the temperature of the second zone is 175-182° C., the temperature of the third zone is 180-190° C., the temperature of the fourth zone is 175-182° C., and the temperature of the fifth zone is 172-177° C.; the temperature of the first zone of the extruder barrel is 170-175° C., the temperature of the second zone is 165-170° C., the temperature of the third zone is 158-160° C., the temperature of the fourth zone is 150-155° C., the temperature of the fifth zone is 148-153° C., and the temperature of the sixth zone is 145-150° C.; the main machine current is 205-215A; the feeding speed is 280-400kg / h; the main machine speed is 300-350rpm; the extrusion pressure is 3-6MPa; and the extrusion speed is 100-140kg / h.

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