High-oil-locking food-grade TPE (thermoplastic elastomer) material as well as preparation method and application thereof

Abstract

The invention relates to the field of high polymer materials, and particularly discloses a high-oil-locking food-grade TPE material as well as a preparation method and application thereof. The material comprises a styrene thermoplastic elastomer, white oil, polyolefin, a dispersed phase polymer, a compatilizer, a composite oil locking agent, an antioxidant and a lubricant. The composite oil locking agent comprises white carbon black and hydrogenated petroleum hydrocarbon resin in a weight ratio of (1-2): 1; the material is free of chemical cross-linking agents. The preparation method comprises the following steps: mixing the components, melting, extruding and granulating. Through a sea-island barrier constructed by the dispersed phase polymer, a multiple physical locking network formed by the composite oil locking agent and a compounding synergistic effect of the specific molecular weight elastomer, efficient constraint on the white oil is realized on the premise that a chemical cross-linking agent is not used; therefore, the material has excellent high-temperature precipitation resistance, good mechanical property and food-grade safety, and is particularly suitable for products such as beverage bottle cap inner pads which are in direct contact with food.

Description

Technical Field

[0001] This application relates to the field of materials, and more specifically, to a high oil-locking food-grade TPE material, its preparation method, and its application. Background Technology

[0002] Thermoplastic elastomer (TPE) materials, especially SEBS-based thermoplastic elastomers (TPE-SEBS), have been widely used in the automotive, electronics, and consumer goods industries due to their combination of rubber elasticity and plastic processing convenience, as well as their halogen-free and recyclable nature. In recent years, with increasing environmental and safety awareness, TPE materials have gradually gained attention in food packaging, particularly in direct food contact applications such as beverage bottle cap liners.

[0003] However, under high temperatures or prolonged use, the white oil in TPE materials can easily migrate from the matrix to the surface, causing an "oil seepage" phenomenon. In the food packaging industry, especially in beverage bottle cap liners, the seepage of white oil not only affects the material's appearance and feel but can also contaminate the contents, impacting food flavor and safety. This problem is particularly pronounced in the high temperatures of summer or in hot and humid environments during logistics.

[0004] Several improved solutions exist in the prior art to address the oil leakage problem of TPE materials. For example, CN 119161667 B discloses a high-temperature resistant oil-leaking TPE material that achieves chemical locking of the filler oil by introducing a crosslinking agent and a crosslinking network surface modifier, making it suitable for electrical products. However, this technology uses a chemical crosslinking system, and the crosslinking agent may decompose during processing or use, producing small molecule residues or odors, making it unsuitable for food-grade materials, especially for inner linings in beverage packaging that come into direct contact with food.

[0005] Therefore, there is an urgent need to develop a high oil-locking TPE material that does not require chemical cross-linking, has no odor or residue risk, and is especially suitable for the food packaging field. It can stably lock in oil at high temperatures while maintaining good processing performance and food safety. Summary of the Invention

[0006] TPE elastomers have low hardness and a high proportion of white oil in their composition. During the shelf life of beverages, exposure to high summer temperatures and the hot and humid environment during transportation can cause white oil to leach onto the material surface and eventually drip into the beverage, affecting product quality. To address these issues, this application provides a high-oil-locking food-grade TPE material, its preparation method, and its applications.

[0007] The technical solution of this application is as follows:

[0008] In a first aspect, this application provides a high oil-locking food-grade TPE material, which comprises, by weight parts:

[0009] 25-45 parts of styrene-based thermoplastic elastomer;

[0010] 35-50 parts white oil;

[0011] 10-25 parts of polyolefin;

[0012] 1-5 parts of dispersed phase polymer;

[0013] 1-5 parts of maleic anhydride graft compatibilizer;

[0014] 2-7 parts of compound oil-locking agent;

[0015] Antioxidant 0.2-0.5 parts;

[0016] Lubricant 0.1-0.4 parts;

[0017] The composite oil-locking agent is formed by mixing silica and hydrogenated petroleum hydrocarbon resin at a mass ratio of 1-2:1 and heating the mixture at 200-240°C.

[0018] The material does not contain chemical cross-linking agents and is suitable for preparing products that come into direct contact with food.

[0019] Furthermore, the aforementioned composite oil-locking agent is prepared by combining silica and hydrogenated petroleum hydrocarbon resin in a weight ratio of 1-2:1.

[0020] Furthermore, the silica in the above-mentioned composite oil-locking agent is a mixture of hydrophilic silica and hydrophobic silica in a 1:1 weight ratio, wherein the specific surface area of ​​each of the hydrophilic silica and hydrophobic silica is 100-400 m² / g; and the softening point of the hydrogenated petroleum hydrocarbon resin is 115-150℃.

[0021] Furthermore, the above-mentioned composite oil-locking agent is prepared by the following method:

[0022] The hydrogenated petroleum hydrocarbon resin is heated to 200-240℃ and melted into a liquid state. Then, the silica is added and the mixture is heated and stirred for 20-40 minutes. After the material has completely cooled, it is pulverized.

[0023] Furthermore, the aforementioned maleic anhydride-grafted compatibilizer is selected from any of the following: maleic anhydride-grafted SEBS, maleic anhydride-grafted PP, and maleic anhydride-grafted PE.

[0024] Furthermore, the dispersed phase polymer is at least one of nylon or ethylene-vinyl alcohol copolymer (EVOH).

[0025] Furthermore, the aforementioned nylon is a crystalline nylon with a melting point below 250°C or an amorphous non-crystalline nylon.

[0026] Preferably, the nylon is selected from at least one of the following polymers:

[0027] Polymers of 1,12-dodecanoic acid and 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane; polymers of 1,6-hexanediamine and 1,12-dodecanoic acid; polymers of 1,6-hexanediamine and 1,6-adipic acid; polymers of 1,6-adipic acid and terephthalic acid; polymers of 1,6-hexanediamine with isophthalic acid and terephthalic acid; caprolactam homopolymers; polyazide tridecane-2-one.

[0028] Furthermore, the aforementioned styrene-based thermoplastic elastomer is at least one of SEBS, SEPS, and SEEPS;

[0029] Preferably, the styrene-based thermoplastic elastomer is SEBS; the styrene content of the SEBS is 25-35%, and it includes high molecular weight SEBS with a molecular weight of more than 150,000 and low molecular weight SEBS with a molecular weight of less than 100,000, wherein the proportion of high molecular weight SEBS exceeds 60%.

[0030] Furthermore, the white oil has a kinematic viscosity of 15-100 mm at 40°C. 2 / s of paraffinic white oil.

[0031] Furthermore, the polyolefin is polypropylene, or a mixture of polypropylene and polyethylene.

[0032] Furthermore, the lubricant is an amide lubricant, selected from at least one of erucamide, behenamide, and stearamide.

[0033] Furthermore, the antioxidant comprises a mixture of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (type 1010) and tris[2,4-di-tert-butylphenyl]phosphite (type 168) in a mass ratio of 1:1.

[0034] Secondly, this application also provides a method for preparing a high oil-locking food-grade TPE material, comprising the following steps: mixing each component evenly according to the ratio, then melting and extruding the mixture through a twin-screw extruder at 180-240°C and granulating it.

[0035] Thirdly, this application provides a food contact article made of the aforementioned high oil-locking food-grade TPE material.

[0036] In summary, this application has the following beneficial effects:

[0037] The technical solution provided in this application effectively solves the industry problem of easy white oil precipitation in food-grade TPE materials, especially in high-oil-filled formulations, under high-temperature environments. Compared with existing technologies, it has the following beneficial effects:

[0038] First, by introducing a dispersed polymer (such as nylon or EVOH) and a compatibilizer, a stable and dense "sea-island" two-phase structure was constructed in a non-polar TPE matrix. This island phase acts as a physical barrier, effectively blocking and delaying the migration of white oil molecules. More importantly, the addition of the compatibilizer significantly improves the bonding force between the island and island phase interfaces, making the structure more compact and stable. This avoids interfacial defects (such as creasing and microcracks) caused by complete incompatibility, thus enhancing the oil-locking effect while ensuring the integrity and long-term stability of the material structure.

[0039] Secondly, the core component, a composite oil-locking agent (composed of hydrophilic silica, hydrophobic silica, and hydrogenated petroleum hydrocarbon resin), forms a unique multi-layered physical locking network within the material, achieving active binding and dynamic adaptation of the white oil. Specifically: ① The hydrophilic silica, through strong hydrogen bonding between surface hydroxyl groups, constructs a continuous, rigid three-dimensional network framework that interweaves with the physical cross-linking network of SEBS, physically dividing and restricting the free flow of the white oil. ② Due to its surface alkylation, the hydrophobic silica exhibits excellent compatibility with the white oil and the swollen SEBS soft segments (EB segments). It not only disperses uniformly, but its alkyl chains can also form strong physical entanglements with oil molecules and polymer chains, an effect far stronger than simple physical adsorption. ③ Hydrogenated petroleum hydrocarbon resin plays a dual role of "tackifying" and "supporting": its chain structure is similar and compatible with white oil and EB segment, acting as a tackifier and increasing the resistance to movement of white oil; its ring structure unit can appropriately expand the EB chain segment, expanding the space for white oil to be contained, and at the same time, through the good mutual solubility of the three, a "swelling and oil-locking" microenvironment that requires higher energy to escape is formed.

[0040] Third, the molecular weight of the styrene-based thermoplastic elastomer matrix was optimized by employing a strategy of blending high-molecular-weight and low-molecular-weight SEBS, synergistically optimizing the material's "oil storage" and "oil locking" capabilities. High-molecular-weight SEBS has longer EB segments, providing more space to absorb and accommodate more white oil; while low-molecular-weight SEBS, due to its denser PS hard segment crosslinking points and shorter EB segments, can form a more compact physical crosslinking network, exerting a stronger binding force on oil molecules. The combination of the two is like a composite of a "loose large network" and a "dense small network," maximizing oil locking capacity while ensuring good material elasticity and processability.

[0041] Therefore, this application does not rely on a single method, but rather forms a complete physical oil-locking system through the synergistic effect of "dispersed phase barrier stabilization," "composite oil-locking agent network construction," and "matrix elastomer molecular weight optimization." This system fundamentally avoids the use of chemical crosslinking agents, completely eliminates the risk of small molecule residues and odors, and fully complies with the stringent safety standards for food contact materials. Ultimately, the resulting TPE material maintains excellent soft touch and elasticity while exhibiting outstanding high-temperature exudation resistance, making it particularly suitable for direct food contact products such as beverage bottle cap liners where safety and reliability requirements are extremely high, successfully expanding the application boundaries of high-performance food-grade TPE materials. Attached Figure Description

[0042] Figure 1 This is an image of the high oil-locking food-grade TPE material provided in Embodiment 1 of this application. Detailed Implementation

[0043] The embodiments of the present invention will be described in detail below with reference to the examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Specific conditions not specified in the examples shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0044] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0045] Preparation Example

[0046] Preparation Example 1

[0047] This preparation example provides a composite oil-locking agent, the preparation method of which includes:

[0048] With a specific surface area of ​​100-200 m² 2 / g of hydrophilic silica and hydrophobic silica are mixed at a mass ratio of 1:1 to obtain a silica mixture.

[0049] Hydrogenated petroleum hydrocarbon resin (softening point 115-150℃) is heated to 220℃ in a reactor until it melts into a liquid state. Then, a mixture of silica is added to the reactor. The mixture is heated and stirred for 30 minutes before being discharged. After the material has completely cooled, it is then pulverized.

[0050] Preparation Example 2

[0051] The difference between this preparation example and Preparation Example 1 is that the specific surface area of ​​both the hydrophilic and hydrophobic silica is 300-400 m². 2 / g, with a mass ratio of 1:0.5.

[0052] Preparation Example 3

[0053] The difference between this preparation example and Preparation Example 1 is that the specific surface area of ​​both the hydrophilic and hydrophobic silica is 300-400 m². 2 / g, with a mass ratio of 1:1.5.

[0054] Preparation Example 4

[0055] The difference between this preparation example and Preparation Example 1 is that the mixing temperature of the mixture of hydrogenated petroleum hydrocarbon resin and silica is 200°C.

[0056] Preparation Example 5

[0057] The difference between this preparation example and Preparation Example 1 is that the mixing temperature of the mixture of hydrogenated petroleum hydrocarbon resin and silica is 250°C.

[0058] Preparation Example 6

[0059] The difference between this preparation example and Preparation Example 1 is that the silica used is hydrophilic silica with the same specific surface area.

[0060] Preparation Example 7

[0061] The difference between this preparation example and Preparation Example 1 is that the silica used is hydrophobic silica with the same specific surface area.

[0062] Preparation Example 8

[0063] The difference between this preparation example and Preparation Example 1 is that an equal amount of unhydrogenated petroleum resin is used instead of hydrogenated petroleum hydrocarbon resin.

[0064] Example 1

[0065] This embodiment provides a high oil-locking food-grade TPE material, the preparation method of which is as follows:

[0066] (1) Preparation of materials: 32 kg of styrene thermoplastic elastomer (abbreviated as rubber powder); 42 kg of white oil; 16.5 kg of polyolefin; 2 kg of dispersed phase polymer; 2 kg of maleic anhydride grafted compatibilizer; 5 kg of composite oil-locking agent (provided by preparation example 1); 0.2 kg of antioxidant; 0.3 kg of lubricant;

[0067] Among them, the styrene-based thermoplastic elastomer is obtained by mixing high molecular weight SEBS (molecular weight of 150,000-300,000) and low molecular weight SEBS (molecular weight of 50,000-100,000) in a mass ratio of 6:4, and the styrene content in the SEBS is 30%;

[0068] The white oil is a paraffin-based white oil with a kinematic viscosity of 50-60 mmHg at 40°C.2 / s; the polyolefin is polypropylene; the dispersed phase polymer is crystalline nylon with a melting point below 250°C (specifically, a polymer of 1,12-dodecanoic acid and 3,3'-dimethyl-4,4'-diaminodicyclohexylmethane); the compatibilizer is maleic anhydride-grafted SEBS; the lubricant is erucamide; the antioxidant is a mixture of antioxidant type 1010 and antioxidant type 168 (mass ratio 1:1).

[0069] (2) Weigh the above materials and add them to the high-speed mixer in sequence. Mix for 10 minutes to ensure that the materials are uniform.

[0070] (3) The material is extruded and granulated using a twin-screw extruder at an extrusion temperature of 210-215℃. The particles are dried and sampled for performance testing.

[0071] Examples 2-5

[0072] The only difference between this set of examples and Example 1 is the amount of each component in the formula, as shown in Table 1.

[0073] Table 1.

[0074]

[0075] Examples 6-10

[0076] The difference between this set of examples and Example 1 is that the composite oil-locking agent in the ingredients is provided by Preparation Examples 2-5 respectively.

[0077] Example 11

[0078] The difference between this embodiment and Example 1 is that the dispersed phase polymer is an equal amount of ethylene-vinyl alcohol copolymer.

[0079] Comparative Examples 1-8

[0080] The materials provided in this comparative example were prepared using the method of Example 1, and their material formulations are shown in Table 2:

[0081] Table 2.

[0082]

[0083] in:

[0084] The rubber powder in Comparative Example 4 was pure high molecular weight SEBS (molecular weight of 150,000-300,000) and did not contain low molecular weight SEBS.

[0085] The rubber powder in Comparative Example 5 was pure low molecular weight SEBS (molecular weight of 50,000-100,000) and did not contain high molecular weight SEBS.

[0086] The composite oil-locking agents of Comparative Examples 6-8 were provided by Preparation Examples 6-8, respectively.

[0087] Performance testing

[0088] I. Detection Methods

[0089] 1. Hardness: The hardness was measured in accordance with the international standard ISO 868:2003 "Plastics and hard rubbers - Determination of indentation hardness (Shore hardness) using a hardness tester".

[0090] 2. Tensile properties: The tensile properties were determined in accordance with the international standard ISO 37:2017 "Determination of tensile stress-strain properties of vulcanized rubber or thermoplastic rubber".

[0091] 3. Oil Locking Ability (High-Temperature Extraction): Referring to the test principle of international standard ISO 815-1:2014 "Determination of Compression Permanence of Vulcanized or Thermoplastic Rubber – Part 1: Under Normal and High Temperature Conditions", a custom-designed accelerated evaluation method is used. Specifically: After compressing the sample at 90℃ for 48 hours, it is removed and soaked in unsweetened tea broth for 2 hours. The extraction of white oil from the tea broth surface is observed and recorded, evaluated on a scale of 1-5: 1. No oil droplets on the surface; 2. Scattered oil droplets on the surface, almost invisible; 3. Obvious oil droplets on the surface, scattered; 4. Obvious oil droplets on the surface, appearing continuously; 5. Abundant oil droplets on the surface, appearing over a large area (Level 1 is the best, Level 5 is the worst).

[0092] II. Test Results

[0093] As shown in Table 3:

[0094] Table 3. Performance of materials provided in each embodiment and comparative example

[0095]

[0096] As can be seen from Table 3:

[0097] The technical solutions of this application (Examples 1-5, 11) demonstrate superior performance in the core indicator "oil-locking ability" (all at level 1 or 2), significantly outperforming all comparative examples (levels 3-5). This strongly proves that this application achieves highly efficient physical oil-locking under conditions without chemical cross-linking through the synergistic effect of multiple components and mechanisms.

[0098] As can be seen from Example 1 and Comparative Example 1, the oil-locking ability of Comparative Example 1 (without nylon and compatibilizer) is only level 4, which is significantly inferior to the complete formulation of the Example (levels 1-2). This proves that the stable "sea-island" structure formed by the dispersed phase polymer (nylon) and compatibilizer is the first effective physical barrier to prevent white oil migration.

[0099] As can be seen from Example 1 and Comparative Examples 2-8:

[0100] Comparative Example 2 (without composite oil-locking agent) has an oil-locking ability of level 3, which is better than Comparative Example 1, but still far worse than the example, indicating that relying solely on the "island" barrier is not enough, and composite oil-locking agent is the key to significantly improving oil-locking performance.

[0101] Comparative Examples 6 and 7 (using pure hydrophilic or pure hydrophobic silica, respectively) both exhibited an oil-locking ability of grade 3, demonstrating that the rigid / flexible dual network constructed from a 1:1 blend of hydrophilic and hydrophobic silica provides superior oil-locking performance compared to a single type. Comparative Example 8 (using unhydrogenated petroleum resin) showed the worst oil-locking ability (grade 4), and the material may also exhibit odor and yellowing risks. This directly and strongly demonstrates that using hydrogenated petroleum hydrocarbon resin is an indispensable and crucial choice for achieving food-grade safety and high-temperature stable oil-locking, and is not a conventional or obvious replacement in the field.

[0102] Comparative Examples 4 and 5 (using pure high-molecular-weight SEBS or pure low-molecular-weight SEBS, respectively) both showed an oil-locking capacity of level 3, with Comparative Example 5 exhibiting a significant decrease in tensile strength. This indicates that the specific blending strategy of high- and low-molecular-weight SEBS maximizes oil-locking capacity while ensuring good mechanical properties (such as tensile strength), demonstrating the synergistic design advantages of a "loose large network" and a "dense small network."

[0103] In summary, this application successfully developed a high-performance food-grade TPE material that combines excellent oil-locking properties (grades 1-2), good mechanical properties, and is completely free of chemical crosslinking agents by synergistically utilizing a stable island barrier constructed from a dispersed phase polymer / compatibilizer, a composite oil-locking network composed of specific hydrophilic / hydrophobic silica and hydrogenated petroleum hydrocarbon resin, and an optimized blend of high / low molecular weight SEBS. This material perfectly solves the problem of oil leakage in high-oil-filled formulations at high temperatures, and is particularly suitable for food contact products such as beverage bottle cap liners where safety and reliability requirements are extremely high, showing broad application prospects.

[0104] 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 oil-locking food-grade TPE material, characterized in that, It includes, by weight, parts: 25-45 parts of styrene-based thermoplastic elastomer; 35-50 parts white oil; 10-25 parts of polyolefin; 1-5 parts of dispersed phase polymer; 1-5 parts of maleic anhydride graft compatibilizer; 2-7 parts of compound oil-locking agent; Antioxidant 0.2-0.5 parts; Lubricant 0.1-0.4 parts; The composite oil-locking agent is formed by mixing silica and hydrogenated petroleum hydrocarbon resin at a mass ratio of 1-2:1 and heating the mixture at 200-240°C. The TPE material does not contain chemical crosslinking agents and is suitable for preparing products that come into direct contact with food.

2. The high oil-locking food-grade TPE material according to claim 2, characterized in that, The silica in the composite oil-locking agent is a mixture of hydrophilic silica and hydrophobic silica in a weight ratio of 1:0.5-1.5, and the specific surface area of ​​each of the hydrophilic and hydrophobic silica is 100-400 m² / g; the softening point of the hydrogenated petroleum hydrocarbon resin is 115-150℃.

3. The high oil-locking food-grade TPE material according to claim 2, characterized in that, The composite oil-locking agent is prepared by the following method: The hydrogenated petroleum hydrocarbon resin is heated to 200-240℃ and melted into a liquid state. Then, the silica is added and the mixture is heated and stirred for 20-40 minutes. After the material has completely cooled, it is pulverized.

4. The high oil-locking food-grade TPE material according to claim 1, characterized in that, The dispersed phase polymer is at least one of nylon or ethylene-vinyl alcohol copolymer.

5. The high oil-locking food-grade TPE material according to claim 1, characterized in that, The nylon is a crystalline nylon with a melting point below 250°C or an amorphous non-crystalline nylon.

6. The high oil-locking food-grade TPE material according to claim 1, characterized in that, The styrene-based thermoplastic elastomer is at least one of SEBS, SEPS, and SEEPS.

7. The high oil-locking food-grade TPE material according to claim 6, characterized in that, The styrene-based thermoplastic elastomer is SEBS; the styrene content of the SEBS is 25-35%, and it includes high molecular weight SEBS with a molecular weight of more than 150,000 and low molecular weight SEBS with a molecular weight of less than 100,000, wherein the proportion of high molecular weight SEBS exceeds 60%.

8. The high oil-locking food-grade TPE material according to claim 1, characterized in that, The maleic anhydride-grafted compatibilizer is selected from any of the following: maleic anhydride-grafted SEBS, maleic anhydride-grafted PP, and maleic anhydride-grafted PE.

9. A method for preparing a high oil-locking food-grade TPE material as described in any one of claims 1-8, characterized in that, The process includes the following steps: mixing the components evenly according to the specified ratio, then melting and extruding the mixture using a twin-screw extruder at 180-240℃ and granulating it.

10. A food contact article, characterized in that, Made from any one of the high oil-locking food-grade TPE materials according to claims 1-8.

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