A high-load-bearing low-migration white conveying belt applied to food processing and a preparation method thereof

Abstract

This application relates to the field of conveyor belt technology in food processing, specifically disclosing a high-load-bearing, low-migration white conveyor belt for food processing and its preparation method. The high-load-bearing, low-migration white conveyor belt for food processing includes a skeleton layer, an upper cover rubber and a lower cover rubber covering the upper and lower surfaces of the skeleton layer, and side rubbers disposed on both sides of the conveyor belt. The upper cover rubber, lower cover rubber, and side rubbers are all made of white rubber compound. The raw materials of the white rubber compound include natural rubber, styrene-butadiene rubber, pre-modified composite filler, titanium dioxide, colorant, sulfur, accelerator, vulcanization activator, antioxidant, and plasticizer. The high-load-bearing, low-migration white conveyor belt for food processing of this application exhibits stable high load-bearing and low-migration characteristics, meeting the stringent requirements of food contact safety standards for low migration levels.

Description

Technical Field

[0001] This application relates to the field of food processing conveyor belt technology, and more specifically, it relates to a high-load-bearing, low-migration white conveyor belt for food processing and its preparation method. Background Technology

[0002] Food conveyor belts are core components of automated food production lines. White rubber conveyor belts, in particular, are widely used in meat cutting, seafood processing, and baking conveying due to their ability to visually identify contaminants and their compatibility with GMP (Good Manufacturing Practice) visual control requirements. Compared to PVC and TPU plastic conveyor belts, white conveyor belts combining natural rubber and styrene-butadiene rubber (SBR) have become the mainstream technology for heavy-duty, high-impact food production lines due to their superior elasticity, impact resistance, and wide temperature range adaptability.

[0003] However, long-term industry verification has revealed that existing natural / styrene-butadiene (SBR) system white food conveyor belts generally suffer from the following core technical defects, significantly falling short of the compliance requirements and stringent operating conditions of the food industry, and failing to simultaneously meet multiple requirements such as food-grade safety, specific white appearance, high load-bearing capacity, low migration, and washability. First, the migration risk of additives in existing white rubber formulations is significant, making food safety compliance difficult to guarantee. Second, existing formulations often use silica and titanium dioxide for direct coloring, resulting in poor white appearance stability and frequent yellowing, discoloration, and blooming issues. Third, white rubber cannot be reinforced with carbon black and must rely on white fillers such as silica. However, in existing technologies, silica is not surface-modified, resulting in poor dispersibility and weak interfacial bonding, making its reinforcing effect far inferior to carbon black systems. This leads to insufficient tensile strength, tear resistance, and abrasion resistance in the cover rubber, making it difficult to balance whiteness and mechanical properties, and severely limiting load-bearing capacity and service life. Finally, the processing technology and batch stability are insufficient, resulting in poor interlayer adhesion.

[0004] Therefore, there is an urgent need to provide a white conveyor belt that simultaneously meets the stringent requirements of food contact safety standards for low migration, and also possesses high load-bearing capacity, high abrasion resistance, and excellent whiteness stability, as well as a controllable preparation method thereof. Summary of the Invention

[0005] To improve the load-bearing capacity and stability of white conveyor belts, this application provides a high-load-bearing, low-migration white conveyor belt for food processing and its preparation method.

[0006] In a first aspect, this application provides a high-load-bearing, low-migration white conveyor belt for food processing, employing the following technical solution:

[0007] A white conveyor belt for food application includes a skeleton layer, an upper cover adhesive and a lower cover adhesive covering the upper and lower surfaces of the skeleton layer, and side adhesives disposed on both sides of the conveyor belt, wherein the upper cover adhesive, the lower cover adhesive and the side adhesives are all made of white rubber.

[0008] By weight, the raw materials of the white rubber compound include 16.5-20 parts natural rubber, 13.5-17 parts styrene-butadiene rubber, 27-34 parts pre-modified composite filler, 3-4 parts titanium dioxide, 3-4 parts colorant, 0.55-0.66 parts sulfur, 0.6-0.8 parts accelerator, 1.5-2 parts vulcanization activator, 0.9-1.1 parts antioxidant, and 2.5-3 parts plasticizer; the raw materials of the pre-modified composite filler include silica and barium sulfate.

[0009] By adopting the above technical solution, this application uses natural rubber and styrene-butadiene rubber as the matrix, pre-modified composite filler as the reinforcing filler system, titanium dioxide and colorant as the coloring system, and vulcanizing agent, accelerator, activator, antioxidant, and plasticizer as the auxiliary system. The raw materials for the pre-modified filler include silica and barium sulfate. Replacing the traditional unmodified silica-only reinforcement scheme with pre-modified composite filler, silica provides reinforcement and barium sulfate provides compatibilization. The synergistic effect of both allows the cover rubber to significantly enhance the mechanical properties and wear resistance of the white conveyor belt while maintaining its white color, thus resolving the technical contradiction in traditional technologies where white materials cannot achieve high load-bearing capacity.

[0010] The pre-modified composite filler is not a simple physical mixture or in-situ coupling of silica and barium sulfate, but rather a pre-associated composite with a unified interface formed through independent pre-processing. In traditional simple physical mixing processes, silica tends to agglomerate due to hydrogen bonding, forming a filler network. Barium sulfate particles are excluded from the agglomerates, resulting not only in a lack of synergy but also stress concentration points due to localized enrichment of barium sulfate. This application employs a pre-modification method, enabling silica and barium sulfate to be mutually bound at the microscopic level. When incorporated into the rubber matrix, they can be wetted by the rubber molecular chains as a unified dispersion unit, allowing the weak functional properties of silica to be fully utilized. This achieves uniform dispersion of nanoparticles and full utilization of specific surface area. Simultaneously, barium sulfate acts as a filler skeleton, uniformly dispersed within the reinforcing network of silica, effectively preventing stress concentration caused by localized enrichment, effectively improving the stability of the white conveyor belt, enhancing its high load-bearing capacity, and reducing the risk of harmful substance migration.

[0011] Optionally, the preparation method of the pre-modified composite filler includes the following steps:

[0012] S1: Add the precipitated silica and barium sulfate to water and stir to prepare a mixed slurry with a solid content of 15-25%, then perform wet ball milling at a temperature of ≤45℃ to obtain a pre-dispersed slurry;

[0013] S2: Heat the pre-dispersed slurry to 60-80℃, add an ethanol solution of silane coupling agent under stirring, wherein the amount of silane coupling agent is 3-5% of the mass of the silica, stir at constant temperature for 2-3 hours, then add 1-2% of the mass of barium sulfate as phosphonic acid modifier, and continue to stir at constant temperature for 1-1.5 hours to obtain the modified slurry;

[0014] S3: The modified slurry is vacuum filtered, washed, dried, and then pulverized to obtain the final product.

[0015] Optionally, the mass ratio of the silica to barium sulfate is 1:(1.2-1.7).

[0016] Optionally, the silane coupling agent is selected from bis-[γ-(triethoxysilane)propyl]tetrasulfide.

[0017] Optionally, the phosphonic acid modifier in step S2 is mono-dodecyl phosphate.

[0018] By adopting the above technical solution, the uniform mixing of silica and barium sulfate at the nanoscale is first achieved by aqueous wet ball milling, which effectively improves the problem of interfacial incompatibility after the two fillers are modified independently. Low temperature control prevents the dehydration condensation of hydroxyl groups on the filler surface, ensuring sufficient active sites for subsequent modification reactions.

[0019] A stepwise coupling method is adopted. In the first step, a silane coupling agent is used. The ethoxy group of Si-69 forms a covalent bond with the hydroxyl group on the surface of silica, and the sulfur bond at the other end crosslinks with the rubber matrix. In the second step, mono-dodecyl phosphate is used as a phosphonic acid modifier to modify barium sulfate. The P-OH in mono-dodecyl phosphate forms a coordinate bond with the barium ions on the surface of barium sulfate, and P=O provides auxiliary coordination, forming a bidentate chelate anchor. The formation of covalent bonds has better resistance to hydrolysis and displacement than ionic bonds, and can exhibit better kinetic stability even under high vulcanization temperature and hydrothermal washing conditions.

[0020] Optionally, it may also include 0.75-1 part of a dihydroxy polymer selected from PEG-2000, PEG-4000 and PEG-6000.

[0021] By adopting the above technical solution, medium and high molecular weight polyethylene glycol (PEG-2000 to PEG-6000) is introduced into the white rubber compound formulation as an interface compatibilizer and dispersant. The ether oxygen atoms in the PEG molecular chain can form hydrogen bonds with the residual silanol groups on the surface of silica, while the ethylene segments have a certain compatibility with the rubber matrix. The PEG molecules form an interface buffer layer between the filler particle surface and the rubber matrix, which effectively inhibits the re-agglomeration of filler particles during the storage and vulcanization process of the compound, and further improves the uniformity of filler dispersion in the rubber matrix.

[0022] Secondly, this application provides a method for preparing a high-load-bearing, low-migration white conveyor belt for food processing, employing the following technical solution:

[0023] A method for preparing a high-load-bearing, low-migration white conveyor belt for food processing includes the following steps:

[0024] S1: Weigh natural rubber, styrene-butadiene rubber, pre-dispersed composite filler, and plasticizer according to the formula raw materials and put them into the internal mixer for the first stage of mixing. After the rubber is discharged, the first stage of compound rubber is obtained. After cooling, it is put into the internal mixer together with titanium dioxide, colorant, vulcanization activator, and antioxidant as minor materials for the second stage of mixing. After the rubber is discharged, the masterbatch is obtained.

[0025] S2: The masterbatch is passed through a two-roll mill, accelerator and sulfur are added, and after being kneaded evenly, it is sheeted to obtain a white compound rubber.

[0026] S3: The white compound rubber is hot-melted and then coated on both sides of the skeleton material through a calender to make white rubber sheet. Then, according to the conveyor belt structure requirements, the white rubber sheet and edge rubber strips are bonded together through a molding machine to make a white conveyor belt blank.

[0027] S4: Place the white conveyor belt blank in a vulcanizing equipment for vulcanization to obtain the desired product.

[0028] Optionally, the vulcanization temperature in step S4 is 140-160℃ and the vulcanization pressure is 2-2.5MPa.

[0029] By adopting the above technical solution, the first stage of mixing involves mixing rubber with pre-modified composite fillers and plasticizers at high temperature to ensure that the fillers are fully impregnated and dispersed. After cooling, auxiliary agents other than vulcanizing agents and accelerators are added for the second stage of mixing to avoid premature reaction or decomposition of antioxidants, vulcanization activators, etc. at excessively high temperatures. Accelerators and sulfur are added at low temperature in the open mill at the end to effectively prevent scorching.

[0030] After hot refining, the white compound rubber is applied to both sides of the skeleton material using a four-roll calender. During calendering, the rubber compound penetrates into the gaps between the canvas fibers under the combined action of heat and pressure, forming an interfacial layer that combines mechanical anchoring and chemical bonding. The excellent dispersibility of the pre-modified composite filler and the interfacial stabilizing effect of PEG indirectly improve the wettability of the compound rubber to the skeleton material, which is beneficial to improving the interlayer adhesion strength.

[0031] In summary, this application has the following beneficial effects:

[0032] 1. Because this application adds pre-modified composite filler to the rubber matrix, firstly, the silica and barium sulfate are uniformly mixed at the nanoscale by aqueous wet ball milling, and then a stepwise coupling method is adopted to enable the pre-modified composite filler to be uniformly dispersed in the rubber matrix and form a stable connection with the rubber matrix. This effectively prevents stress concentration caused by local enrichment in the rubber matrix, thereby effectively improving the stability of the white conveyor belt, enhancing its high load-bearing capacity, and reducing the risk of migration of harmful substances.

[0033] 2. This application introduces medium-to-high molecular weight polyethylene glycol (PEG-2000 to PEG-6000) as an interface compatibilizer and dispersant in the white rubber compound formulation. On the one hand, the ether oxygen atoms in the PEG molecular chain can form hydrogen bonds with the residual silanol groups on the surface of silica, while the ethylene segments have a certain compatibility with the rubber matrix. The PEG molecules form an interface buffer layer between the filler particle surface and the rubber matrix, which effectively inhibits the re-agglomeration of filler particles during the storage and vulcanization process of the compound, and further improves the uniformity of filler dispersion in the rubber matrix.

[0034] 3. The white rubber compound prepared by the method of this application gives the conveyor belt a clean white appearance, which facilitates the intuitive identification of food residue and foreign matter contamination during the production process, and is compatible with the visual hygiene control requirements of food cleanrooms. The uniform dispersion of the pre-modified composite filler in the rubber matrix and its stable combination with the organic-inorganic interface make the surface of the cover rubber dense and the filler less prone to precipitation, giving the product good anti-pollution and easy-to-clean properties. Detailed Implementation

[0035] The present application will be further described in detail below with reference to embodiments and comparative examples.

[0036] Preparation example of pre-modified composite filler

[0037] Preparation Example 1

[0038] The pre-modified composite filler is prepared by means of the following steps:

[0039] S1: Add silica and barium sulfate in a mass ratio of 1:1.4 to deionized water and stir to prepare a mixed slurry with a solid content of 20%. Then put it into a wet ball mill for wet ball milling for 30 minutes. The ball milling media is zirconia beads and the ball milling temperature is ≤45℃ to obtain a pre-dispersed slurry.

[0040] S2: The pre-dispersed slurry was heated to 70℃. Bis-[γ-(triethoxysilyl)propyl]tetrasulfide was mixed with anhydrous ethanol in equal amounts and pre-dissolved in a 60℃ water bath to form a homogeneous solution. The solution was slowly added dropwise to the pre-dispersed slurry under stirring. The amount of silane coupling agent was 4% of the mass of silica. The reaction was carried out at a constant temperature and stirred for 2.5h. Then, 1.5% of the mass of barium sulfate mono-n-dodecyl phosphate was added and the reaction was continued at a constant temperature and stirred for 1.2h to obtain the modified slurry. The CAS of mono-n-dodecyl phosphate is 2627-35-2.

[0041] S3: Vacuum filter the modified slurry, wash the filter cake three times with deionized water to remove unreacted excess coupling agent and free alcohol, dry and pulverize to obtain the final product.

[0042] Preparation Example 2

[0043] The pre-modified composite filler is prepared by means of the following steps:

[0044] S1: Add silica and barium sulfate in a mass ratio of 1:1.2 to deionized water and stir to prepare a mixed slurry with a solid content of 15%. Then put it into a wet ball mill for wet ball milling for 30 minutes. The ball milling media is zirconia beads and the ball milling temperature is ≤45℃ to obtain a pre-dispersed slurry.

[0045] S2: Heat the pre-dispersed slurry to 60℃, mix bis-[γ-(triethoxysilyl)propyl]tetrasulfide with anhydrous ethanol in equal amounts, pre-dissolve in a 60℃ water bath to form a homogeneous solution, and slowly add it dropwise to the pre-dispersed slurry under stirring. The amount of silane coupling agent is 3% of the mass of silica. Stir at constant temperature for 3 hours, then add 1-2% of the mass of barium sulfate mono-n-dodecyl phosphate, and continue to stir at constant temperature for 1.5 hours to obtain the modified slurry. The CAS of mono-n-dodecyl phosphate is 2627-35-2.

[0046] S3: Vacuum filter the modified slurry, wash the filter cake three times with deionized water to remove unreacted excess coupling agent and free alcohol, dry and pulverize to obtain the final product.

[0047] Preparation Example 3

[0048] The pre-modified composite filler is prepared by means of the following steps:

[0049] S1: Add silica and barium sulfate in a mass ratio of 1:1.7 to deionized water and stir to prepare a mixed slurry with a solid content of 25%. Then put it into a wet ball mill for wet ball milling for 30 minutes. The ball milling media is zirconia beads and the ball milling temperature is ≤45℃ to obtain a pre-dispersed slurry.

[0050] S2: Heat the pre-dispersed slurry to 80℃, mix bis-[γ-(triethoxysilyl)propyl]tetrasulfide with anhydrous ethanol in equal amounts, pre-dissolve in a 60℃ water bath to form a homogeneous solution, and slowly add it dropwise to the pre-dispersed slurry under stirring. The amount of silane coupling agent is 5% of the mass of silica. Stir at constant temperature for 2 hours, then add 1-2% of the mass of barium sulfate mono-n-dodecyl phosphate, and continue to stir at constant temperature for 1 hour to obtain the modified slurry. The CAS of mono-n-dodecyl phosphate is 2627-35-2.

[0051] S3: Vacuum filter the modified slurry, wash the filter cake three times with deionized water to remove unreacted excess coupling agent and free alcohol, dry and pulverize to obtain the final product.

[0052] Preparation Example 4

[0053] The difference between the pre-modified composite filler and Preparation Example 1 is that step S1 specifically involves:

[0054] Add silica and barium sulfate in a mass ratio of 1:1.4 to deionized water and stir to prepare a mixed slurry with a solid content of 20%. Disperse the mixture ultrasonically for 30 minutes to obtain a pre-dispersed slurry.

[0055] Preparation Example 5

[0056] The difference between the pre-modified composite filler and Preparation Example 1 is that step S2 specifically involves:

[0057] The pre-dispersed slurry was heated to 70°C. Bis-[γ-(triethoxysilyl)propyl]tetrasulfide was mixed with anhydrous ethanol in equal amounts and pre-dissolved in a 60°C water bath to form a homogeneous solution. The solution was then slowly added dropwise to the pre-dispersed slurry under stirring. The amount of silane coupling agent was 4% of the mass of silica. The mixture was stirred at a constant temperature for 2.5 hours to obtain the modified slurry.

[0058] Preparation Example 6

[0059] The difference between the pre-modified composite filler and Preparation Example 1 is that step S2 specifically involves:

[0060] The pre-dispersed slurry was heated to 70°C, and 1.5% (by weight) of barium sulfate mono-dodecyl phosphate was added under stirring. The mixture was stirred at a constant temperature for 1.2 hours to obtain the modified slurry.

[0061] Preparation Example 7

[0062] The pre-modified composite filler differs from Preparation Example 1 in that the mono-n-dodecyl phosphate in step S2 is replaced with an equal mass of stearic acid.

[0063] Example

[0064] Example 1

[0065] A high-load-bearing, low-migration white conveyor belt for food processing includes a skeleton layer, an upper cover rubber and a lower cover rubber covering the upper and lower surfaces of the skeleton layer, and side rubbers disposed on both sides of the conveyor belt. The upper cover rubber, the lower cover rubber and the side rubbers are all made of white rubber material.

[0066] By weight, the raw materials of the white rubber compound include 18.4 parts of natural rubber, 15.6 parts of styrene-butadiene rubber, 31 parts of the pre-modified composite filler prepared in Preparation Example 1, 3.5 parts of titanium dioxide, 3.5 parts of colorant C5, 0.58 parts of sulfur, 0.7 parts of accelerator, 1.8 parts of vulcanization activator, 0.85 parts of PEG-2000, 1 part of antioxidant 264 and 2.8 parts of plasticizer, wherein the accelerator is accelerator CZ and accelerator DM in a mass ratio of 2:1, the vulcanization activator is zinc oxide and stearic acid in a mass ratio of 3:2, and the plasticizer is transformer oil and paraffin wax in a mass ratio of 5:1;

[0067] The above-mentioned method for preparing a high-load-bearing, low-migration white conveyor belt for food processing includes the following steps:

[0068] S1: Weigh natural rubber, styrene-butadiene rubber, pre-dispersed composite filler, and plasticizer according to the formula raw materials and put them into the internal mixer for the first stage of mixing. After the rubber is discharged, the first stage of compound rubber is obtained. After cooling, it is put into the internal mixer together with titanium dioxide, colorant, vulcanization activator, and antioxidant as minor materials for the second stage of mixing. After the rubber is discharged, the masterbatch is obtained.

[0069] S2: Pass the masterbatch through a two-roll mill, add accelerator and sulfur, and after mixing evenly, sheet out to obtain white compound rubber.

[0070] S3: The white compound rubber is hot-melted and then coated on both sides of the skeleton material through a calender to make white rubber sheet. Then, according to the structural requirements of the conveyor belt, the white rubber sheet and edge rubber strips are bonded together through a molding machine to make a white conveyor belt blank.

[0071] S4: Place the white conveyor belt blank in the vulcanizing equipment and vulcanize it for 30 minutes at a vulcanizing temperature of 150℃ and a vulcanizing pressure of 2.2MPa to obtain the desired product.

[0072] Example 2

[0073] A high-load-bearing, low-migration white conveyor belt for food processing differs from Example 1 in that, by weight, the raw materials of the white rubber compound include 16.5 parts of natural rubber, 13.5 parts of styrene-butadiene rubber, 27 parts of the pre-modified composite filler prepared in Preparation Example 2, 3 parts of titanium dioxide, 3 parts of colorant C5, 0.55 parts of sulfur, 0.6 parts of accelerator, 1.5 parts of vulcanization activator, 0.75 parts of PEG-2000, 0.9 parts of antioxidant 264, and 2.5 parts of plasticizer. The accelerator is accelerator CZ and accelerator DM in a mass ratio of 2:1, the vulcanization activator is zinc oxide and stearic acid in a mass ratio of 3:2, and the plasticizer is transformer oil and paraffin wax in a mass ratio of 4:1.

[0074] The above-mentioned method for preparing a high-load-bearing, low-migration white conveyor belt for food processing includes the following steps:

[0075] S1: Weigh natural rubber, styrene-butadiene rubber, pre-dispersed composite filler, and plasticizer according to the formula raw materials and put them into the internal mixer for the first stage of mixing. After the rubber is discharged, the first stage of compound rubber is obtained. After cooling, it is put into the internal mixer together with titanium dioxide, colorant, vulcanization activator, and antioxidant as minor materials for the second stage of mixing. After the rubber is discharged, the masterbatch is obtained.

[0076] S2: Pass the masterbatch through a two-roll mill, add accelerator and sulfur, and after mixing evenly, sheet out to obtain white compound rubber.

[0077] S3: The white compound rubber is hot-melted and then coated on both sides of the skeleton material through a calender to make white rubber sheet. Then, according to the structural requirements of the conveyor belt, the white rubber sheet and edge rubber strips are bonded together through a molding machine to make a white conveyor belt blank.

[0078] S4: Place the white conveyor belt blank in the vulcanizing equipment and vulcanize it for 30 minutes at a vulcanizing temperature of 140℃ and a vulcanizing pressure of 2.5MPa to obtain the desired product.

[0079] Example 3

[0080] A high-load-bearing, low-migration white conveyor belt for food processing differs from Example 1 in that, by weight, the raw materials of the white rubber compound include 20 parts natural rubber, 17 parts styrene-butadiene rubber, 34 parts pre-modified composite filler prepared in Preparation Example 3, 4 parts titanium dioxide, 4 parts colorant C5, 0.66 parts sulfur, 0.8 parts accelerator, 2 parts vulcanization activator, 1 part PEG-2000, 1.1 parts antioxidant 264, and 3 parts plasticizer. The accelerator is accelerator CZ and accelerator DM in a mass ratio of 2:1, the vulcanization activator is zinc oxide and stearic acid in a mass ratio of 3:2, and the plasticizer is transformer oil and paraffin wax in a mass ratio of 6:1.

[0081] The above-mentioned method for preparing a high-load-bearing, low-migration white conveyor belt for food processing includes the following steps:

[0082] S1: Weigh natural rubber, styrene-butadiene rubber, pre-dispersed composite filler, and plasticizer according to the formula raw materials and put them into the internal mixer for the first stage of mixing. After the rubber is discharged, the first stage of compound rubber is obtained. After cooling, it is put into the internal mixer together with titanium dioxide, colorant, vulcanization activator, and antioxidant as minor materials for the second stage of mixing. After the rubber is discharged, the masterbatch is obtained.

[0083] S2: Pass the masterbatch through a two-roll mill, add accelerator and sulfur, and after mixing evenly, sheet out to obtain white compound rubber.

[0084] S3: The white compound rubber is hot-melted and then coated on both sides of the skeleton material through a calender to make white rubber sheet. Then, according to the structural requirements of the conveyor belt, the white rubber sheet and edge rubber strips are bonded together through a molding machine to make a white conveyor belt blank.

[0085] S4: Place the white conveyor belt blank in the vulcanizing equipment and vulcanize it for 30 minutes at a vulcanizing temperature of 160℃ and a vulcanizing pressure of 2MPa to obtain the desired product.

[0086] Example 4

[0087] A high-load-bearing, low-migration white conveyor belt for food processing differs from Example 1 only in that the pre-modified composite filler in the white rubber raw material is prepared in Preparation Example 4.

[0088] Example 5

[0089] A high-load-bearing, low-migration white conveyor belt for food processing differs from Example 1 only in that the pre-modified composite filler in the white rubber raw material is prepared by Example 5.

[0090] Example 6

[0091] A high-load-bearing, low-migration white conveyor belt for food processing differs from Example 1 only in that the pre-modified composite filler in the white rubber raw material is prepared by Example 6.

[0092] Example 7

[0093] A high-load-bearing, low-migration white conveyor belt for food processing differs from Example 1 only in that the pre-modified composite filler in the white rubber raw material is prepared in Preparation Example 7.

[0094] Example 8

[0095] A high-load-bearing, low-migration white conveyor belt for food processing differs from Example 1 only in that the PEG-2000 in the white rubber raw material is replaced with an equal mass of PEG-4000.

[0096] Example 9

[0097] A high-load-bearing, low-migration white conveyor belt for food processing differs from Example 1 only in that the PEG-2000 in the white rubber raw material is replaced with an equal mass of PEG-6000.

[0098] Example 10

[0099] A high-load-bearing, low-migration white conveyor belt for food processing differs from Example 1 only in that PEG-2000 is not added to the white rubber raw material.

[0100] Comparative Example

[0101] Comparative Example 1

[0102] A high-load-bearing, low-migration white conveyor belt for food processing differs from Example 1 only in that the barium sulfate and silica have not undergone pre-modification treatment, and the pre-modified composite filler in the white rubber raw material is replaced with silica, barium sulfate and bis-[γ-(triethoxysilyl)propyl]tetrasulfide in a mass ratio of 1:1.4:0.04.

[0103] Performance testing

[0104] The high-load-bearing, low-migration white conveyor belts prepared in Examples 1-10 and Comparative Example 1 for food processing were subjected to the following relevant performance tests. Each test was conducted 3 times, and the average value of the 3 test results was taken as the final result and recorded in Table 1.

[0105] Tensile strength and elongation at break were tested according to GB / T 7984-2013; the volume loss of the sample (mm) was measured using a DIN abrasion tester with a load of 10±0.2 N, according to ISO 4649-2017 (determination of abrasion resistance of rubber or thermoplastic elastomers using a rotating cylindrical drum apparatus). 3 ).

[0106] Table 1

[0107] Group Tensile strength / MPa Elongation at break / % Wear amount / mm 3 ]] Example 1 20.5 480 132 Example 2 19.8 465 141 Example 3 21.1 498 127 Example 4 18.2 420 168 Example 5 17.5 405 182 Example 6 16.8 390 198 Example 7 18.0 415 175 Example 8 21.4 545 128 Example 9 23.7 580 123 Example 10 18.5 430 158 Comparative Example 1 15.2 355 234

[0108] According to the performance test results of Examples 1-4 and Comparative Example 1 in Table 1, the white conveyor belt prepared in this application has a tensile strength ≥19.8MPa, an elongation at break ≥465%, and an abrasion amount ≤141mm. 3This indicates that the application adds pre-modified composite filler to the rubber matrix. First, the silica and barium sulfate are uniformly mixed at the nanoscale by aqueous wet ball milling. Then, a step-by-step coupling method is used to ensure that the pre-modified composite filler is uniformly dispersed inside the rubber matrix and forms a stable connection with the rubber matrix. This effectively prevents stress concentration caused by local enrichment inside the rubber matrix, thereby effectively improving the stability of the white conveyor belt, enhancing its high load-bearing capacity, and reducing the risk of migration of harmful substances.

[0109] According to the performance test results of Examples 1 and 4, it can be seen that in the mixing stage of silica and barium sulfate, ultrasonic dispersion alone cannot achieve uniform mixing of silica and barium sulfate at the nanoscale. Aqueous wet ball milling can effectively improve the problem of incompatibility at the interface after the two fillers are modified independently. Low temperature control prevents the dehydration condensation of hydroxyl groups on the filler surface and ensures sufficient active sites for subsequent modification reactions.

[0110] The performance test results of Examples 1 and 5-7 show that the stepwise coupling method is effective. In the first step, a silane coupling agent, Si-69, forms a covalent bond between its ethoxy group and the hydroxyl group on the surface of silica, while the sulfur bond at the other end crosslinks with the rubber matrix. In the second step, mono-dodecyl phosphate is used as a phosphonic acid modifier to modify barium sulfate. The P-OH group in mono-dodecyl phosphate forms a coordination bond with the barium ions on the surface of barium sulfate, with P=O providing auxiliary coordination, forming a bidentate chelate anchor. The covalent bond formation exhibits superior resistance to hydrolysis and displacement compared to ionic bonds, demonstrating better kinetic stability even under high vulcanization temperatures and hydrothermal washing conditions. The performance of white conveyor belts obtained by using only silane coupling agents or only phosphonic acid modifiers is inferior to that of this application.

[0111] According to the performance test results of Examples 1 and 8-10, it can be seen that the introduction of medium and high molecular weight polyethylene glycol (PEG-2000 to PEG-6000) into the white rubber compound formulation can act as an interface compatibilizer and dispersant, further improving the processing performance of the white rubber compound. The ether oxygen atoms in the PEG molecular chain can form hydrogen bonds with the residual silanol groups on the surface of silica, forming an interface buffer layer between the filler particle surface and the rubber matrix, effectively inhibiting the re-agglomeration of filler particles during the storage and vulcanization process of the compound, and further improving the uniformity of filler dispersion in the rubber matrix.

[0112] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high-load-bearing, low-migration white conveyor belt for food processing, characterized in that, It includes a skeleton layer, an upper cover adhesive and a lower cover adhesive covering the upper and lower surfaces of the skeleton layer, and side adhesives disposed on both sides of the conveyor belt. The upper cover adhesive, the lower cover adhesive and the side adhesives are all made of white rubber. By weight, the raw materials of the white rubber compound include 16.5-20 parts natural rubber, 13.5-17 parts styrene-butadiene rubber, 27-34 parts pre-modified composite filler, 3-4 parts titanium dioxide, 3-4 parts colorant, 0.55-0.66 parts sulfur, 0.6-0.8 parts accelerator, 1.5-2 parts vulcanization activator, 0.9-1.1 parts antioxidant, and 2.5-3 parts plasticizer; the raw materials of the pre-modified composite filler include silica and barium sulfate.

2. The high-load-bearing, low-migration white conveyor belt for food processing according to claim 1, characterized in that, The preparation method of the pre-modified composite filler includes the following steps: S1: Add the precipitated silica and barium sulfate to water and stir to prepare a mixed slurry with a solid content of 15-25%, then perform wet ball milling at a temperature of ≤45℃ to obtain a pre-dispersed slurry; S2: Heat the pre-dispersed slurry to 60-80℃, add an ethanol solution of silane coupling agent under stirring, wherein the amount of silane coupling agent is 3-5% of the mass of the silica, stir at constant temperature for 2-3 hours, then add 1-2% of the mass of barium sulfate as phosphonic acid modifier, and continue to stir at constant temperature for 1-1.5 hours to obtain the modified slurry; S3: The modified slurry is vacuum filtered, washed, dried, and then pulverized to obtain the final product.

3. The high-load-bearing, low-migration white conveyor belt for food processing according to claim 2, characterized in that, The mass ratio of the silica to barium sulfate is 1:(1.2-1.7).

4. The high-load-bearing, low-migration white conveyor belt for food processing according to claim 2, characterized in that, The silane coupling agent is selected from bis-[γ-(triethoxysilyl)propyl]tetrasulfide.

5. The high-load-bearing, low-migration white conveyor belt for food processing according to claim 2, characterized in that, The phosphonic acid modifier in step S2 is mono-dodecyl phosphate.

6. The high-load-bearing, low-migration white conveyor belt for food processing according to claim 1, characterized in that, It also includes 0.75-1 part of a dihydroxy polymer selected from PEG-2000, PEG-4000 and PEG-6000.

7. The method for preparing the high-load-bearing, low-migration white conveyor belt for food processing according to any one of claims 1-6, characterized in that, Includes the following steps: S1: Weigh natural rubber, styrene-butadiene rubber, pre-dispersed composite filler, and plasticizer according to the formula raw materials and put them into the internal mixer for the first stage of mixing. After the rubber is discharged, the first stage of compound rubber is obtained. After cooling, it is put into the internal mixer together with titanium dioxide, colorant, vulcanization activator, and antioxidant as minor materials for the second stage of mixing. After the rubber is discharged, the masterbatch is obtained. S2: The masterbatch is passed through a two-roll mill, accelerator and sulfur are added, and after being kneaded evenly, it is sheeted to obtain a white compound rubber. S3: The white compound rubber is hot-melted and then coated on both sides of the skeleton material through a calender to make white rubber sheet. Then, according to the conveyor belt structure requirements, the white rubber sheet and edge rubber strips are bonded together through a molding machine to make a white conveyor belt blank. S4: Place the white conveyor belt blank in a vulcanizing equipment for vulcanization to obtain the desired product.

8. The method for preparing a high-load-bearing, low-migration white conveyor belt for food processing according to claim 7, characterized in that, In step S4, the vulcanization temperature is 140-160℃ and the vulcanization pressure is 2-2.5MPa.