Mixing process of PVC composite material

Abstract

The present application relates to a mixing process of PVC composite material. The mixing process comprises the following steps: S1. preparing hot mixture; the components of the hot mixture include PVC resin, inorganic filler and heat stabilizer with a mass ratio of 50:(6-10):(3-4); S2. mixing the PVC resin without heat mixing and the hot mixture obtained in step S1 without cooling medium. The mixing process can realize the cooling of the hot mixture after the heat mixing of the PVC composite material without cooling medium, which not only reduces the energy consumption of mixing and improves the yield of mixing, but also keeps the mechanical properties of the PVC composite material good or improves the mechanical properties of the PVC composite material (compared with the traditional cold mixing process), thereby effectively reducing the production cost of enterprises.

Description

Technical Field

[0001] This invention relates to the field of PVC material processing technology, and more specifically, to a mixing process for PVC composite materials. Background Technology

[0002] PVC resin is the main material used in pipe production. To improve the strength of the pipes, inorganic fillers (such as calcium carbonate) are usually added to PVC composites. Furthermore, because PVC resin is prone to decomposition under high-temperature conditions (such as hot mixing and melt extrusion), leading to material defects, heat stabilizers are typically added to PVC composites to prevent resin decomposition.

[0003] The processing of PVC composite materials mainly includes hot mixing, cold mixing, and melt extrusion granulation. The resulting granules are further processed into pipes. Hot mixing and cold mixing are usually carried out in a hot and cold mixing machine. The specific process is as follows: First, the components (including PVC resin powder, fillers, additives, etc.) are added to the hot mixing machine according to the formula. After hot mixing, the set temperature is reached. Then, the hot-mixed material is automatically discharged directly into the cold mixing machine, where it is cooled to a suitable temperature (usually room temperature), completing the hot and cold mixing. In the hot mixing cylinder of the hot mixing machine, PVC resin, inorganic fillers, and various additives are mixed evenly and heated to about 110 degrees Celsius. The cold mixing cylinder of the cold mixing machine has a jacketed wall with cooling water flowing through it. The hot-mixed material is discharged into the cold mixing cylinder, where the cooling water in the jacket cools the hot-mixed material to a suitable temperature.

[0004] Due to space constraints and production line design limitations in actual production, the hot-mixed material cannot be immediately added to the extruder; it must wait approximately one hour before being added. This makes cold mixing a crucial step in the processing of PVC composite materials.

[0005] The main purposes of hot mixing of PVC composite materials are threefold: first, to ensure uniform spatial distribution of the components, achieving homogeneous mixing; second, to achieve pre-plasticization; and third, to remove as much moisture as possible from the PVC composite material. Immediately after hot mixing, cold mixing is necessary. The purposes of cold mixing include: first, preventing the PVC composite material from being exposed to high temperatures for extended periods, which could lead to PVC resin decomposition; second, preventing the PVC composite material from reabsorbing moisture during natural cooling, thus negatively impacting the performance of subsequent products; and third, further removing moisture and small-molecule volatiles from the PVC composite material, improving the mechanical properties of the PVC composite product. Therefore, in actual production, without cold mixing, the mechanical properties of PVC composite products will decrease due to PVC resin decomposition and moisture reabsorption.

[0006] To ensure the cooling effect of cold mixing, the volume of the cold mixer cylinder is usually more than twice that of the hot mixing cylinder, which limits the cold mixing output per unit time. In addition, to ensure the cooling effect of cold mixing, a large amount of cooling water needs to be circulated through the cylinder wall of the cold mixer to assist in cooling down, thereby achieving material cooling. However, the large amount of cooling water leads to higher production costs.

[0007] If the mechanical properties of PVC composite materials can be guaranteed, increasing the output of cold mixing and reducing the amount of cold water used can bring greater benefits to the production enterprise. Summary of the Invention

[0008] The primary objective of this invention is to overcome the problems of low output and high production costs caused by the existing cold mixing process for PVC composite materials, which requires a large amount of cold water for cooling, and to provide a mixing process for PVC composite materials.

[0009] A further objective of this invention is to provide a method for preparing PVC composite materials.

[0010] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0011] A mixing process for a PVC composite material includes the following steps:

[0012] S1. Preparation of a hot mix; the hot mix comprises PVC resin, inorganic filler and heat stabilizer in a mass ratio of 50:(6-10):(3-4);

[0013] S2. Without the need for a cooling medium, mix the PVC resin that has not been heat-mixed with the heat-mixed material obtained in step S1;

[0014] The mass ratio of the PVC resin that has not been heat-mixed to the PVC resin in the heat-mixed material in step S2 is 1:(1.0 to 1.2).

[0015] Through extensive research, the inventors of this invention discovered that by first preparing a hot-mixed material from PVC resin, inorganic fillers, and heat stabilizers in a specific mass ratio, and then mixing it with a specific mass of unmixed PVC resin, the PVC composite material can be cooled to a lower temperature before melt extrusion, thus replacing the cold mixing process in traditional methods. Since the cold mixing process is eliminated, i.e., the use of cooling media (such as cold water) is unnecessary, energy consumption is significantly reduced.

[0016] The inventors of this invention also unexpectedly discovered that by replacing the cold mixing in the traditional process with the mixing in step S2 of this invention, the quality (such as mechanical properties) of the PVC composite material does not decrease due to the elimination of the cold mixing in the traditional process; on the contrary, the quality of the PVC composite material product is improved compared to the traditional process (which involves cold mixing). The reason for this may be that controlling the amount of each component in the hot mix within a certain range, and controlling the mass ratio of the PVC resin that has not been hot mixed to the PVC resin in the hot mix within a certain range, allows the temperature of the mixed material to be lowered. Furthermore, since the PVC resin that has not been hot mixed is usually in powder or granular form, its contact with the hot mix is ​​faster and more thorough, resulting in a faster cooling rate, better cooling uniformity, less PVC resin decomposition, and less consumption of heat stabilizers. This, in turn, improves the stability of the PVC composite material in subsequent processing (melt extrusion) and thus improves the product quality. In addition, it is also crucial that inorganic fillers and heat stabilizers are mixed with PVC resin in the hot mixing process (step S1). This ensures the effective dispersion of inorganic fillers and heat stabilizers in the system, which in turn helps maintain good mechanical properties. If some inorganic fillers and heat stabilizers are added in step S2, it will lead to poor mechanical properties of the material, which will pose a risk to the use of the product and prevent the company from reducing production costs.

[0017] In addition, compared with the cold mixing of traditional processes, the mixing output of step S2 of the present invention can be significantly improved, and the improvement in mixing output further reduces the average energy consumption of mixing.

[0018] The mixing process of this invention can achieve cooling of hot mix without the need for a cooling medium. This not only reduces the energy consumption of mixing and increases the mixing output, but also maintains or improves the mechanical properties of PVC composite materials (compared to traditional cold mixing processes), thereby effectively reducing the production costs of enterprises.

[0019] Preferably, the inorganic filler is calcium carbonate, specifically light calcium carbonate.

[0020] Preferably, the average particle size of the inorganic filler is 2 to 10 micrometers.

[0021] Preferably, the heat stabilizer is a calcium-zinc heat stabilizer.

[0022] Preferably, the hot mix of step S1 further includes other additives.

[0023] More preferably, the other additives include, but are not limited to, impact modifiers (e.g., LB-564), lubricants (e.g., YT-95), and colorants (e.g., titanium dioxide).

[0024] Preferably, the process of preparing the hot mix in step S1 is as follows: the components of the hot mix are hot-mixed to obtain the hot mix.

[0025] More preferably, the hot mixing time is 5 to 8 minutes and the rotation speed is 800 to 1200 r / min.

[0026] Preferably, the temperature of the hot mix in step S1 is 110–120°C.

[0027] Preferably, the mixing time in step S2 is 2 to 3 minutes, and the rotation speed is 10 to 30 r / min.

[0028] Preferably, the temperature of the PVC resin that has not been heat-mixed in step S2 is 25-30°C.

[0029] Preferably, the average degree of polymerization of the PVC resin in the hot-mixed material in step S1 or the PVC resin that has not been hot-mixed in step S2 is 300 to 1500.

[0030] Preferably, the mass ratio of the uncooked PVC resin to the PVC resin in the hot-mixed material in step S2 is 1:(1.1 to 1.2). Within this mass ratio range, the material obtained through the mixing process exhibits better impact properties.

[0031] Preferably, the mixing process in step S2 is carried out in a hot and cold mixer.

[0032] More preferably, the preparation of the hot mix in step S1 is carried out in the cylinder of the hot mixer of the hot-cold mixer, and the mixing in step S2 is carried out in the cylinder of the cold mixer of the hot-cold mixer. When the mixing in step S2 is carried out in the cylinder of the cold mixer of the hot-cold mixer, no cooling medium (cooling water) is circulated in the cold mixer of the hot-cold mixer.

[0033] In this invention, the cooling medium is water. That is, step S2 is: mixing the PVC resin that has not been hot-mixed with the hot-mixed material described in step S1 without the need for cooling water.

[0034] In this invention, the hot-mixed material is not cooled before mixing in step S2. That is, in step S2, the temperature of the hot-mixed material is still 110-120°C before it is immediately mixed with the PVC resin that has not been hot-mixed.

[0035] A method for preparing a PVC composite material includes the following steps: the above-mentioned mixing process, melt extrusion, and granulation, to obtain the PVC composite material.

[0036] Compared with the prior art, the beneficial effects of the present invention are:

[0037] The mixing process of this invention can achieve cooling of hot mix without the need for a cooling medium. This not only reduces the energy consumption of mixing and increases the mixing output, but also maintains or improves the mechanical properties of PVC composite materials (compared to traditional cold mixing processes), thereby effectively reducing the production costs of enterprises. Detailed Implementation

[0038] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0039] Example 1

[0040] This embodiment provides a mixing process for PVC composite materials, including the following steps:

[0041] 1) Add 50 parts by weight of PVC resin (manufacturer: Zhongtai Chemical, grade: PVC-SG5), 6 parts by weight of light calcium carbonate and 4 parts by weight of heat stabilizer (BAERLOCHER MC 161FP) into the cylinder of the hot mixer of a 500 / 1000 hot and cold mixer, and stir at 1000 r / min for 6 min to obtain a hot mix.

[0042] 2) The hot mixture is automatically discharged into the cylinder of the cold mixer using a 500 / 1000 hot and cold mixer. At the same time, 55 parts by weight of PVC resin (manufacturer: Zhongtai Chemical, grade: PVC-SG5, temperature: approximately 30℃) that has not undergone hot mixing is added to the cylinder of the cold mixer of the 500 / 1000 hot and cold mixer. Without cooling water flowing through the cold mixer, the mixture is stirred at a speed of 15 r / min for 2 minutes to complete the mixing.

[0043] Example 2

[0044] This embodiment provides a mixing process for PVC composite materials, which is basically the same as that in Embodiment 1, except that:

[0045] In step 1), the amount of light calcium carbonate used is 8 parts by weight, and the amount of heat stabilizer used is 3 parts by weight.

[0046] Example 3

[0047] This embodiment provides a mixing process for PVC composite materials, which is basically the same as that in Embodiment 1, except that:

[0048] In step 2), the amount of PVC resin that has not undergone heat mixing is 50 parts by weight.

[0049] Example 4

[0050] This embodiment provides a mixing process for PVC composite materials, which is basically the same as that in Embodiment 1, except that:

[0051] In step 2), the amount of PVC resin that has not undergone heat mixing is 60 parts by weight.

[0052] Example 5

[0053] This embodiment provides a mixing process for PVC composite materials, which is basically the same as that in Embodiment 1, except that:

[0054] In step 1), the stirring time is 4 minutes.

[0055] Example 6

[0056] This embodiment provides a mixing process for PVC composite materials, which is basically the same as that in Embodiment 1, except that:

[0057] In step 2), the stirring speed is 20 r / min.

[0058] Comparative Example 1

[0059] This comparative example provides a mixing process for PVC composite materials, which is basically the same as that in Example 1, except that:

[0060] In step 2), the amount of PVC resin that has not undergone heat mixing is 40 parts by weight.

[0061] Comparative Example 2

[0062] This comparative example provides a mixing process for PVC composite materials, which is basically the same as that in Example 1, except that:

[0063] In step 2), the amount of PVC resin that has not undergone heat mixing is 70 parts by weight.

[0064] Comparative Example 3

[0065] This comparative example provides a mixing process for PVC composite materials, which differs from Example 3 in that:

[0066] In step 1), the amounts of PVC resin, light calcium carbonate, and heat stabilizer are 50 parts by weight, 3 parts by weight, and 2 parts by weight, respectively; in step 2), in addition to the hot mix and 50 parts by weight of PVC resin that has not undergone hot mixing treatment, 3 parts by weight of light calcium carbonate (at a temperature of about 30°C) and 2 parts by weight of heat stabilizer (at a temperature of about 30°C) are added.

[0067] Comparative Example 4

[0068] This comparative example provides a mixing process for a PVC composite material, which differs from Example 3 in that: in step 1), the amounts of PVC resin, light calcium carbonate, and heat stabilizer are 50 parts by weight, 3 parts by weight, and 2 parts by weight, respectively; in step 2), PVC resin that has not undergone heat mixing is not added, and the mixture is stirred at 15 r / min for 2 min with cooling water flowing through it in a cold mixer.

[0069] Comparative Example 5

[0070] This comparative example provides a mixing process for PVC composite materials, including the following steps:

[0071] 1) Add 50 parts by weight of PVC resin (manufacturer: Zhongtai Chemical, grade: PVC-SG5), 3 parts by weight of light calcium carbonate, and 2 parts by weight of heat stabilizer (BAERLOCHER MC 161FP) to the cylinder of a 500 / 1000 hot and cold mixer. Stir at 1000 rpm for 6 minutes to obtain a hot mix, and then let it stand at room temperature for 1 hour. No cold mixing is performed during the entire process.

[0072] Performance testing

[0073] After step 2) of the mixing process in Examples 1-6 and Comparative Examples 1-4, or after step 1) of Comparative Example 5, the materials were fed to an extruder for melt extrusion and granulation. The melt extrusion temperature was 160-210°C, yielding PVC composite materials. The PVC composite materials were injection molded into pipes, and their impact properties and tensile strength were tested according to GB / T14152-2016 and GB / T 8804.2-2003.

[0074] Meanwhile, according to the mixing process of each embodiment and comparative example, mixing was carried out continuously for 2 hours / day, and the mixing capacity (mixing amount per hour KG / hour) and energy consumption per ton of mixture (energy consumption per ton of mixture KWH / ton) of each embodiment and comparative example were calculated.

[0075] The performance test results of each embodiment and comparative example are shown in Table 1.

[0076] Table 1

[0077]

[0078]

[0079] As can be seen from Table 1:

[0080] The materials treated by the mixing process in Examples 1-5 all achieved (100 / 100 no breakage) in the impact performance test (equivalent to 100 samples without damage in the impact test), the tensile strength was above 45.5 MPa, the mixing capacity was above 1590 KG / hour, and the energy consumption per ton of mixing was below 29.50 KWH / ton. This indicates that the mixing process of the present invention can achieve cooling of the hot-mixed PVC composite material without the need for a cooling medium. It not only reduces the energy consumption of mixing and increases the mixing output, but also enables the PVC composite material to have good mechanical properties, meeting its requirements for use as a pipe material.

[0081] Comparative Example 1 contained too little PVC resin that had not undergone heat mixing, resulting in poor mechanical properties of the material. The impact performance test result was 96 / 100 without breakage, indicating a risky use of the product and requiring extensive quality control or disposal as waste, thus increasing the company's production costs. Comparative Example 2 contained too much PVC resin that had not undergone heat mixing, resulting in poor mechanical properties of the material. The impact performance test result was 94 / 100 without breakage, indicating a risky use of the product and requiring extensive quality control or disposal as waste, thus increasing the company's production costs. Comparative Example 3 had some inorganic filler and heat stabilizer added in step 2). The mixing in step 2) failed to effectively disperse the inorganic filler and heat stabilizer evenly, resulting in poor mechanical properties of the material. Compared to Example 3, the tensile strength of the material decreased by 10.5%; the impact performance test result was 92 / 100 without breakage, indicating a significant risky use of the product and requiring extensive quality control or disposal as waste, thus increasing the company's production costs. Comparative Example 4, which uses traditional hot and cold mixing, exhibits low mixing capacity, high average energy consumption, and significantly lower tensile strength compared to Example 3. This indicates that the mixing process of the present invention can improve the mechanical properties of the material. Comparative Example 5 omits step 2) of the mixing process of the present invention and traditional cold mixing, instead allowing the material to cool naturally at room temperature. This results in significantly poorer mechanical properties; the tensile strength of the material decreased by 12.3% compared to Example 3. The impact performance test result was 92 / 100 without breakage, indicating a significant risk in product use, requiring extensive quality inspection or disposal as scrap, thus increasing the company's production costs. Furthermore, the mixing output is low and the average energy consumption is high.

[0082] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A mixing process of PVC composite material, characterized in that, Includes the following steps: S1. Preparation of a hot mix; the hot mix comprises PVC resin, inorganic filler and heat stabilizer in a mass ratio of 50:6:4; S2. Without the need for a cooling medium, stir and mix the PVC resin that has not been hot-mixed with the hot-mixed material described in step S1; The inorganic filler is calcium carbonate; The temperature of the hot mix in step S1 is 110~120℃; the method for preparing the hot mix is ​​to stir and mix the components at a stirring speed of 1000 r / min for 6 min. In step S2, the temperature of the PVC resin that has not been hot-mixed is 25~30℃; the mass ratio of the PVC resin that has not been hot-mixed to the PVC resin in the hot-mixed material is 1:1; the stirring speed is 15r / min and the stirring time is 2min.

2. The process of claim 1 wherein, The heat stabilizer is a calcium-zinc heat stabilizer.

3. The process of claim 1 wherein, The process of preparing the hot mix in step S1 is as follows: the components of the hot mix are hot-mixed to obtain the hot mix.

4. The process of claim 1 wherein, The average degree of polymerization of the PVC resin in the hot-mixed material in step S1 or the PVC resin that has not been hot-mixed in step S2 is 300~1500.

5. The process of claim 1 wherein, The mixing process is carried out in a hot and cold mixer.

6. A method of producing a PVC composite material, characterized by, The process includes the following steps: mixing process as described in any one of claims 1 to 5, melt extrusion, and granulation, to obtain the PVC composite material.

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