A white food-grade EPDM rubber hose and preparation method thereof

Abstract

The present application relates to the technical field of EPDM rubber, and specifically to a white food-grade EPDM rubber hose and a preparation method thereof. A EPDM rubber, the raw materials for preparing the EPDM rubber include: EPDM rubber, white carbon black, kaolin, paraffin oil, zinc oxide powder, calcium oxide powder, 1-2 parts of stearin, silane coupling agent, titanium dioxide, sulfur, and a comprehensive accelerator. Its preparation method includes: after mixing EDPM rubber, zinc oxide, and stearic acid and heating and mixing, adding white carbon black, kaolin, etc. to continue mixing, adding sulfur, etc. after standing and mixing to obtain a pre-refined rubber material; refining the pre-refined rubber material, turning the rubber and then discharging the sheet; cutting the strips and hanging the rods, cooling at room temperature for standby; extruding the normal temperature rubber strips to obtain the product. The present application can reduce water absorption by additionally introducing kaolin into the raw materials and adopts a comprehensive accelerator of Altermix BGL-70, HANSUN EG6M-80GE and 5-hydroxy-1,4-naphthoquinone, so as to greatly improve the vulcanization efficiency, shorten the time, broaden the vulcanization temperature range, and make the process more stable and controllable.

Description

Technical Field

[0001] The present application relates to the technical field of EPDM rubber, and in particular to a white food-grade EPDM rubber hose and a preparation method thereof. Background Art

[0002] As a general-purpose rubber material with excellent performance and outstanding cost-effectiveness, EPDM has shown wide application potential in many fields, especially in the food and medical industries, which have extremely high requirements for material safety and durability. In these sensitive and critical industries, the quality of EPDM products is directly related to the safety and reliability of the products. However, in the process of preparing EPDM extruded pipes, a crucial link - microwave vulcanization, has brought considerable challenges to food-grade EPDM materials.

[0003] Specifically, food-grade EPDM white rubber contains a variety of fillers, such as white carbon black and calcium carbonate, which are highly hygroscopic. Once the rubber absorbs too much water, it will have a significant adverse effect on the subsequent vulcanization effect. The presence of water will not only cause bubbles to form during the vulcanization process, thereby affecting the product's appearance quality and internal structural stability, but also reduce the vulcanization efficiency, making it difficult for the product to meet the established performance standards.

[0004] In addition, food-grade EPDM white rubber is also very demanding on the selection of vulcanization accelerators. Since the vulcanization accelerator is directly related to the vulcanization speed and the quality of the vulcanized product, it is necessary to select those vulcanization accelerators that can meet the vulcanization speed requirements and will not threaten the safety of the product. However, in practical applications, such vulcanization accelerators are often limited in choice and it is difficult to fully meet the rapid vulcanization conditions required for microwave vulcanization. Summary of the invention

[0005] In order to solve the above-mentioned problems, the present application provides a white food-grade EPDM rubber and a preparation method thereof, aiming to overcome the microwave vulcanization difficulties caused by the hygroscopicity of the filler and the limitation of the selection of vulcanization accelerators during the preparation process, and to realize the efficient and rapid production of food-grade extruded tubes.

[0006] In the first aspect, the present application provides a white food-grade EPDM rubber hose, which adopts the following technical solution:

[0007] A raw material for preparing a white food-grade EPDM rubber hose, calculated by weight, includes the following:

[0008] EPDM rubber 100 parts

[0009] 20-40 parts of white carbon black

[0010] Kaolin 100-150 parts

[0011] Paraffin oil 10-30 parts

[0012] 3-5 parts zinc oxide powder

[0013] Calcium oxide powder 10-15 parts

[0014] 1-2 parts stearic acid

[0015] Silane coupling agent 1-3 parts

[0016] Titanium dioxide 5-10 parts

[0017] Sulfur 0.5-1.5 parts

[0018] 3-5 parts of comprehensive accelerator.

[0019] By adopting the above technical solution: optimizing the selection and ratio of raw materials, the microwave vulcanization problem caused by the hygroscopicity of fillers and the limitation of the selection of vulcanization accelerators in the preparation process is effectively solved, and efficient and rapid production of food-grade extruded tubes is achieved, while ensuring the safety and reliability of the product.

[0020] Alternatively, the raw materials used for preparing the white food-grade EPDM rubber hose include the following in parts by weight:

[0021] EPDM rubber 100 parts

[0022] 30-40 parts of white carbon black

[0023] Kaolin 130-150 parts

[0024] Paraffin oil 20-30 parts

[0025] 3-5 parts zinc oxide powder

[0026] Calcium oxide powder 10-15 parts

[0027] 1-2 parts stearic acid

[0028] Silane coupling agent 1-3 parts

[0029] Titanium dioxide 5-8 parts

[0030] Sulfur 0.5-1.5 parts

[0031] 3-5 parts of comprehensive accelerator.

[0032] Further, optionally, the raw materials used for preparing the white food-grade EPDM rubber hose are prepared from the following components in parts by weight:

[0033] EPDM rubber 100 parts

[0034] 30 parts of white carbon black

[0035] 130 parts of kaolin

[0036] 20 parts paraffin oil

[0037] Zinc oxide powder 5 parts

[0038] Calcium oxide powder 10 parts

[0039] 1 part stearic acid

[0040] Silane coupling agent 3 parts

[0041] 8 parts of titanium dioxide

[0042] 0.5 parts of sulfur

[0043] 5 parts of comprehensive accelerator.

[0044] By adopting the above technical solution: accurately controlling the weight of each component, the optimized preparation of white food-grade EPDM rubber hose can be achieved, the performance, safety and production efficiency of the product can be improved, and the demand for high-quality rubber products in the food and medical industries can be met.

[0045] Further, optionally, the comprehensive accelerator is a mixture of Altermix BGL-70, HANSUN EG6M-80GE and 5-hydroxy-1,4-naphthoquinone in a mass percentage of 43%:56%:1%.

[0046] By adopting the above technical solution: a mixture of Altermix BGL-70, HANSUN EG6M-80GE and 5-hydroxy-1,4-naphthoquinone compounded in a specific mass percentage is used as a comprehensive accelerator, which not only optimizes the vulcanization process, improves the performance and production efficiency of the product, but also ensures the safety and reliability of the product. This compound composition has unique advantages and characteristics, and provides an efficient, environmentally friendly and reliable solution for the preparation of white food-grade EPDM rubber hose;

[0047] These three components produce a significant synergistic effect after compounding. Altermix BGL-70 and HANSUNEG6M-80GE, as the main vulcanization accelerators, each have different vulcanization active points and action mechanisms. Their compounding can broaden the vulcanization temperature range, increase the vulcanization speed, and reduce the side effects during the vulcanization process.

[0048] Although the addition of 5-hydroxy-1,4-naphthoquinone is in a small proportion, it plays a key regulatory role. It can fine-tune the progress of the vulcanization reaction, making the vulcanization process smoother and avoiding over-vulcanization or under-vulcanization. Since the vulcanization reaction is more complete and uniform, the cross-linking structure in the vulcanization product is denser, reducing the generation of internal defects and bubbles, thereby improving the overall quality of the product.

[0049] Furthermore, the compound composition can significantly improve the vulcanization efficiency, shorten the vulcanization time, and under microwave vulcanization conditions, can quickly reach the required vulcanization temperature and maintain a stable vulcanization rate, thereby speeding up the production process and improving production efficiency.

[0050] Further, optionally, the silane coupling agent is selected from one or more of bis(triethoxysilylpropyl) disulfide, bis-(γ-triethoxysilylpropyl) tetrasulfide, and bis-(γ-triethoxysilylpropyl) tetrasulfide wax.

[0051] In a specific embodiment, the bis(triethoxysilylpropyl) disulfide may be one of SG-Si996, SG-Si 998, and SG-Si 1589, the bis-(γ-triethoxysilylpropyl) tetrasulfide may be KH-845-4 or SG-Si1289, and the bis-(γ-triethoxysilylpropyl) tetrasulfide wax may be Rsi-E.

[0052] Further, optionally, the EPDM rubber has an ethylene content of 70.0-70.5 wt % and a norbornene content of 0.5-5.0 wt %.

[0053] In the second aspect, the present application provides a method for preparing a white food-grade EPDM rubber hose, which adopts the following technical solution:

[0054] A method for preparing a white food-grade EPDM rubber hose comprises the following preparation steps:

[0055] S1, banburying: adding EDPM rubber, zinc oxide powder, and stearic acid, heating and mixing at a constant rate of 10-20°C / min for 1-2min, then adding white carbon black, kaolin, paraffin oil, silane coupling agent, and titanium dioxide, and continuing to mix for 5-8min until the temperature reaches 110-120°C, then removing the glue to obtain a coarse rubber material, after the coarse rubber material is left to stand at room temperature for 24h, the rubber material is mixed with sulfur, a comprehensive accelerator, and calcium oxide powder for mixing for 2-3min, until the temperature reaches 110-120°C, and then removing the glue to obtain a pre-refined rubber material;

[0056] S2, refining: refining the pre-refined rubber material at a rate of 30-40 rpm / min, and discharging the sheet after 3-7 minutes of refining;

[0057] S3, preforming: the film obtained after S2 is cut into strips and hung on a rod, and is left to cool naturally to below 25° C. at room temperature for standby use;

[0058] S4, extrusion molding: the room temperature rubber strip obtained after cooling in S3 is extruded to obtain a product.

[0059] Further, optionally, the specific process of extrusion molding is: using a cold feed extruder for extrusion molding, the screw temperature is 50-60°C, the plasticizing temperature is 65-75°C, the head temperature is 75-85°C, and the extrusion speed is 15-25m / min.

[0060] By adopting the above technical scheme: in the mixing step, the heating rate, mixing time and temperature are strictly controlled to ensure the full mixing and uniform dispersion of the raw materials, avoid the problem of local overheating or insufficient mixing, and at the same time, the standing time of the coarse rubber material is also carefully set to ensure its full maturation and stability. In the open mixing step, the open mixing rate and the rubber turning time are controlled to further optimize the fluidity and plasticity of the rubber material, laying a good foundation for the subsequent molding step;

[0061] During the extrusion step, a cold feed extruder is used, and key parameters such as screw temperature, plasticizing temperature, die temperature and extrusion speed are strictly controlled. This not only ensures the smooth extrusion and molding of the rubber compound, but also improves production efficiency and product quality. The extrusion temperature is precisely controlled to avoid degradation or insufficient cross-linking of the rubber compound due to excessively high temperature during the extrusion process. At the same time, a reasonable extrusion speed also ensures the dimensional stability and surface quality of the hose.

[0062] The entire preparation process, from internal mixing, open mixing, preforming to extrusion molding, has been carefully designed and optimized to ensure a smooth and efficient production process. This efficient production process not only improves production efficiency, but also reduces production costs and energy consumption.

[0063] In summary, this application has the following beneficial technical effects:

[0064] 1. Kaolin is introduced into the raw materials for preparing the white food-grade EPDM rubber hose in this application. Compared with traditional white carbon black and calcium carbonate, kaolin has lower hygroscopicity, which helps to reduce the moisture absorbed by the rubber during preparation and storage, avoid the generation of bubbles during vulcanization, and ensure the appearance quality and internal structure stability of the product;

[0065] 2. The comprehensive accelerator in the raw materials for preparing the white food-grade EPDM rubber hose of this application is compounded by Altermix BGL-70, HANSUN EG6M-80GE and 5-hydroxy-1,4-naphthoquinone in a specific proportion, which can significantly improve the vulcanization efficiency and shorten the vulcanization time. The compounded comprehensive accelerator can broaden the vulcanization temperature range and make the vulcanization process more stable and controllable. DETAILED DESCRIPTION

[0066] The present application is further described in detail below with reference to embodiments.

[0067] Performance testing

[0068] The physical properties of the rubber tubes prepared in the embodiments and comparative examples were tested according to standards GB / T3512-2014 and ISO 188:2011, and the test items were hardness (Shore A), tensile strength, and elongation at break (%);

[0069] According to standard FDA 21 CFR 177.2600, the rubber tubes prepared in the examples and comparative examples were subjected to distilled water tests, and the residual content (residue refers to the content of distilled water and other non-essential impurities) was tested 7 hours before distillation and 2 hours after distillation.

[0070] Examples 1-4

[0071] A white food grade EPDM rubber hose, the components and their usage (kg) are shown in the following table.

[0072] Table 1: Raw materials used in the preparation of white food-grade EPDM rubber hose in Examples 1-4

[0073]

[0074] The above-mentioned white carbon black is AEROSIL R202 hydrophobic fumed silica; the above-mentioned kaolin is BASF Metamax high-activity metakaolin; the above-mentioned silane coupling agent is SG-Si 1589 and Rsi-E, with a ratio of 40%:60%; the above-mentioned comprehensive accelerator is a mixture of Altermix BGL-70, HANSUN EG6M-80GE and 5-hydroxy-1,4-naphthoquinone in a weight percentage of 43%:56%:1%, the above-mentioned EPDM rubber has an ethylene content of 70.0-70.5wt%, and a norbornene content of 0.5-5.0wt%;

[0075] The above-mentioned white food-grade EPDM rubber hose is prepared by the following preparation steps:

[0076] S1, banburying: adding a predetermined amount of EDPM rubber, zinc oxide powder, and stearic acid, heating and mixing at a constant rate of 15°C / min for 1 min, then adding white carbon black, kaolin, paraffin oil, silane coupling agent, and titanium dioxide, and continuing to mix for 5 min until the temperature reaches 115°C, then draining the rubber to obtain a coarse rubber material, after the coarse rubber material is left to stand at room temperature for 24 h, the rubber material is mixed with sulfur, a comprehensive accelerator, and calcium oxide powder for 3 min, and then draining the rubber material after the temperature reaches 120°C to obtain a pre-refined rubber material;

[0077] S2, refining: refining the pre-refined rubber material at a rate of 35 rpm / min, and discharging the sheet after turning the rubber for 5 minutes;

[0078] S3, preforming: the film obtained after S2 is cut into strips and hung on a rod, and is left to cool naturally to below 25° C. at room temperature for standby use;

[0079] S4, extrusion molding: use a cold feed extruder to extrude the room temperature rubber strip obtained after cooling in S3, the screw temperature is 55°C, the plasticizing temperature is 65°C, the extrusion temperature is 70°C, the head temperature is 80°C, and the extrusion speed is 20m / min to obtain a rubber tube crude product, and then the rubber tube crude product is subjected to microwave vulcanization through multiple sections of hot air to obtain a white food-grade EPDM rubber hose.

[0080] Embodiment 5-8

[0081] A white food-grade EPDM rubber hose, the only difference from Example 2 is that the dosage of each component is different. The components and their dosage (kg) are shown in the following table.

[0082] Table 2: Raw materials used in the preparation of white food-grade EPDM rubber hose in Example 1 and Examples 5-8

[0083]

[0084] The white food-grade EPDM rubber hoses prepared in the above Examples 1-8 were subjected to various performance tests with reference to the aforementioned performance test tests, and the test results are recorded in the following table.

[0085] Table 3: Performance test results of white food grade EPDM rubber hose of Examples 1-8

[0086]

[0087] It can be seen from the test data in the above table that the rubber hoses prepared in Examples 1-8 have good physical properties and can meet the needs of daily use. In the FDA distilled water test, the performance of each embodiment is different, and the residual amount before distillation 7 hours is 1.6-22.4 mg / in 2Only Example 6 failed the test requirement, with the residual content after distillation for 2 hours being between 0.33 and 5.4 mg / in 2 , only Example 2 passed the test requirements;

[0088] It can be seen that Example 2 can be used as a preferred embodiment among the above embodiments.

[0089] Examples 9-11

[0090] A white food-grade EPDM rubber hose, the only difference from Example 2 is that:

[0091] The usage of white carbon black used in the preparation is different, see the table below for details.

[0092] Table 4: Usage of white carbon black used as raw material in the preparation of white food grade EPDM rubber hose in Examples 9-11

[0093]

[0094] Example 12

[0095] A white food-grade EPDM rubber hose, the only difference from Example 2 is that:

[0096] The kaolin used in the preparation is Acti-Min® RG.

[0097] Examples 13-16

[0098] A white food-grade EPDM rubber hose, the only difference from Example 2 is that the use of the comprehensive accelerator used in the preparation is different.

[0099] Table 5: Usage of comprehensive accelerator in raw materials for preparing white food-grade EPDM rubber hose in Examples 13-16

[0100]

[0101] Comparative Examples 1-3

[0102] A white food-grade EPDM rubber hose, the only difference from Example 2 is that different raw materials are used in its preparation, as shown in the table below.

[0103] Table 6: Raw materials used in the preparation of white food-grade EPDM rubber hose in Comparative Examples 1-3

[0104]

[0105] The white food-grade EPDM rubber hoses prepared in the above-mentioned Examples 9-16 and Comparative Examples 1-3 were subjected to various performance tests with reference to the aforementioned performance test tests, and the test results are recorded in the following table.

[0106] Table 7: Performance test results of white food grade EPDM rubber hose in Examples 1-8

[0107]

[0108] As can be seen from the table above, the white food-grade EPDM rubber hoses prepared in Examples 9-11 have a residual concentration of 4.2-30.4 mg / in in the FDA distilled water test 7 hours before distillation. 2 The residual content after distillation for 2 hours is between 0.54-7.7 mg / in 2 Inside;

[0109] Example 9 failed to pass the FDA distilled water test because the white carbon black in Example 9 was AEROSIL20 hydrophilic fumed silica, which contained hydrophilic groups such as hydroxyl groups on its surface and was more likely to interact with water molecules.

[0110] In Example 11, a mixture of two hydrophobic silicas was used to replace AEROSIL R202 in equal amounts. Compared with the test results of Example 2, there was still a certain gap in the FDA distilled water test. Although the two hydrophobic silicas performed well when used alone, their mixture may not have the same performance advantages. This may be due to the interaction between different types of hydrophobic silica in the mixture, resulting in a compromise or imbalance in performance.

[0111] In Example 10, WACKER hydrophobic white carbon black HDK H20 was used to replace AEROSIL R202 hydrophobic fumed silica in equal amounts, but the test results were still inferior to those of the white food-grade EPDM rubber hose prepared in Example 2.

[0112] In Example 12, the residual amount was 22.7 mg / in 7 hours before distillation. 2 , the residual after 2 hours of distillation is 5.6mg / in 2 ; It is unable to pass the FDA distilled water test. This may be because BASF Metamax high-activity kaolin has unique functional properties, which makes it perform well in rubber hoses. Although Acti-Min® RG kaolin is also a high-quality kaolin, its properties may be different from Metamax, resulting in failure to achieve the same performance after replacement.

[0113] In Examples 13-16, the residual concentration in the first 7 hours of distillation was 5.4-9.8 mg / in 2 , the residual after 2 hours of distillation is 0.78-1.43mg / in 2, Example 15 and Example 16 both passed the indicators calibrated by the FDA distilled water test. When the comprehensive accelerator was a mixture of Altermix BGL-70 and HANSUN EG6M-80GE at a mass percentage of 50%:50% or a mixture of Actmix®EG3M-75GEF140, Altermix BGL-70, and HANSUN EG6M-80GE at a mass percentage of 20%:40%:40%, as shown in the performance test results of Example 13 and Example 14, both failed to pass the indicators calibrated by the FDA distilled water test;

[0114] However, when 5-hydroxy-1,4-naphthoquinone is included in the comprehensive accelerator, as shown in Examples 13 and 14, it has a significant impact on the vulcanization efficiency and whether it can pass the FDA distilled water test, and the white food-grade EPDM rubber hose is only produced when the comprehensive accelerator is a mixture of Altermix BGL-70, HANSUN EG6M-80GE and 5-hydroxy-1,4-naphthoquinone in a mass percentage of 43%:56%:1%.

[0115] In addition, in Comparative Examples 1-3, attempts were made to use multiple rubber components instead of single EPDM rubber to prepare white food-grade EPDM rubber hoses. From the test results, although their physical properties performed well, they could not meet the indicators calibrated by the FDA distilled water test, and there was a large gap between them and the calibrated indicators.

[0116] Therefore, the above-mentioned raw material components are specially selected so that the rubber material can reach the vulcanization temperature more quickly during the microwave vulcanization process, thereby improving the vulcanization efficiency. At the same time, since the adverse effect of moisture on the vulcanization process is reduced, the vulcanization process is more stable and controllable, further improving the production efficiency and quality of the product. The various components work together to make the prepared white food-grade EPDM rubber hose have excellent physical properties and chemical stability.

[0117] The above are all modifications without creative contribution or solutions that obviously constitute technical inspiration that can be made to the present embodiment as needed by technical personnel in this field after reading this specification, but they should be protected by patent law as long as they are within the scope of the claims of this application.

Claims

1. A white food grade EPDM rubber hose, characterized in that: The raw materials used for preparation, by weight, include the following: 100 parts of EPDM rubber, 30 parts of white carbon black, 130 parts of kaolin, 20 parts of paraffin oil, 5 parts of zinc oxide powder, 10 parts of calcium oxide powder, 1 part of stearic acid, 3 parts of silane coupling agent, 8 parts of titanium dioxide, 0.5 parts of sulfur, and 5 parts of comprehensive accelerator; The comprehensive accelerator is a mixture of Altermix BGL-70, HANSUN EG6M-80GE and 5-hydroxy-1,4-naphthoquinone in a weight percentage of 43%:56%:1%. The silane coupling agent is selected from one or more of bis(triethoxysilylpropyl) disulfide, bis-(γ-triethoxysilylpropyl) tetrasulfide, and bis-(γ-triethoxysilylpropyl) tetrasulfide wax; The EPDM rubber has an ethylene content of 70.0-70.5wt% and a norbornene content of 0.5-5.0wt%; The white carbon black is AEROSIL R202 hydrophobic fumed silica; the kaolin is BASF Metamax high-activity metakaolin.

2. The method for preparing the white food-grade EPDM rubber hose according to claim 1, characterized in that: The method comprises the following preparation steps: S1, banburying: adding EDPM rubber, zinc oxide powder, and stearic acid, heating and mixing at a constant rate of 10-20°C / min for 1-2min, then adding white carbon black, kaolin, paraffin oil, silane coupling agent, and titanium dioxide, and continuing to mix for 5-8min until the temperature reaches 110-120°C, then removing the glue to obtain a coarse rubber material, after the coarse rubber material is left to stand at room temperature for 24h, the rubber material is mixed with sulfur, a comprehensive accelerator, and calcium oxide powder for mixing for 2-3min, until the temperature reaches 110-120°C, and then removing the glue to obtain a pre-refined rubber material; S2, refining: refining the pre-refined rubber material at a rate of 30-40 rpm / min, and discharging the sheet after 3-7 minutes of refining; S3, preforming: the film obtained after S2 is cut into strips and hung on a rod, and is left to cool naturally to below 25° C. at room temperature for standby use; S4, extrusion molding: the room temperature rubber strip obtained after cooling in S3 is extruded to obtain a product.

3. The method for preparing the white food-grade EPDM rubber hose according to claim 2, characterized in that: The specific process of extrusion molding is: use a cold feed extruder for extrusion molding, the screw temperature is 50-60°C, the plasticizing temperature is 65-75°C, the head temperature is 75-85°C, and the extrusion speed is 15-25m / min.

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