A hydrolysis-resistant food-grade silica gel material with TPR slow rebound hand feeling and a preparation method thereof

Abstract

This invention discloses a hydrolysis-resistant food-grade silicone material that combines the slow rebound feel of TPR (Total Resin) and its preparation method. By weight, it comprises the following raw materials: 90-150 parts of methyl vinyl silicone rubber matrix, 1-5 parts of a structure control agent, 1-5 parts of reinforcing filler, 1-5 parts of a softening regulator, 0.3-1.2 parts of a silane coupling agent, and 0.1-0.6 parts of a vulcanizing agent. Using methyl vinyl silicone rubber as the matrix, the synergistic combination of the structure control agent and the softening regulator precisely controls the density of the silicone rubber crosslinking network and the slippage behavior of the molecular chains, extending the recovery time after compression deformation to 6-15 seconds, perfectly replicating the soft, slow-rebound, and decompression-relieving feel of TPR materials. Simultaneously, relying on the high bond energy characteristics of the Si-O bonds in the silicone rubber main chain, the material does not exhibit whitening, stickiness, or cracking after immersion in boiling water for 48 hours, maintaining a mechanical property retention rate of over 90%. This fundamentally solves the problems of traditional TPR toys being prone to hydrolysis and aging in humid and hot environments, and having a short service life.

Description

Technical Field

[0001] This invention relates to the field of silicone preparation technology, specifically to a hydrolysis-resistant food-grade silicone material that combines the slow rebound feel of TPR with its preparation method. Background Technology

[0002] Slow-rebound decompression toys (commonly known as "squeezable toys") have become emotional consumer products covering all age groups in recent years, and the market demand for materials that combine a soft, bouncy feel with durability is growing. Currently, most mainstream slow-rebound toys on the market are made of TPR (thermoplastic rubber). TPR is a polymer material obtained by blending and modifying SBS (styrene-butadiene-styrene block copolymer) with components such as rubber oil, polypropylene, or polystyrene. This material has a unique physical cross-linking structure and can be directly molded through thermoplastic processes such as injection molding and extrusion without vulcanization, resulting in high production efficiency and low energy consumption. At the same time, TPR material has a wide adjustable hardness range (Shore A 5~100 degrees), a soft and bouncy feel, and moderate rebound, which can well meet the "decompression feel" requirements of slow-rebound toys.

[0003] However, TPR materials have several inherent drawbacks in slow rebound toy applications. Firstly, because TPR uses SBS as its base material, its molecular chain contains unsaturated double bonds, resulting in poor chemical stability and consequently, poor aging resistance and UV resistance. TPR materials are prone to hydrolytic degradation at high temperatures (above 60°C) or in humid environments. Prolonged immersion in water can cause TPR products to whiten, become sticky, crack, and even powder, leading to a shorter lifespan. Specifically, the whitening of TPR products may be due to external friction causing the white filler powder in the compound to be exposed, or it may be due to the migration of stabilizers and other additives from the formula to the product surface. Furthermore, TPR plastic products commonly exhibit surface aging and a significant reduction in mechanical properties during long-term use.

[0004] Secondly, TPR materials pose safety and hygiene risks. Some TPR formulations require the addition of small-molecule additives such as plasticizers and stabilizers, which may migrate and leach onto the surface of the product during use. Especially when toys are put in the mouths of infants and young children, these leachates pose a risk of ingestion, failing to meet increasingly stringent high-end infant and toddler safety standards. Furthermore, TPR materials tend to develop a sticky feel after prolonged use, further impacting user experience and product hygiene.

[0005] On the other hand, while traditional silicone materials possess good food-grade safety and excellent resistance to hydrolysis and aging, meeting the requirements for use in scenarios where infants and children chew on them, conventional silicone materials have a relatively fast rebound speed and a hard feel, failing to achieve the slow-rebound decompression feel unique to TPR. Currently, there is no material solution that can simultaneously achieve the slow-rebound feel of TPR and the hydrolysis resistance and food-grade safety of silicone. Therefore, to address this issue, the inventors have proposed a hydrolysis-resistant food-grade silicone material that combines the slow-rebound feel of TPR with its preparation method. Summary of the Invention

[0006] To address the shortcomings of the aforementioned technologies, this invention provides a hydrolysis-resistant food-grade silicone material that combines the slow rebound feel of TPR with its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a hydrolysis-resistant food-grade silicone material with TPR slow rebound feel and its preparation method, comprising the following raw materials by weight:

[0008] The composition includes 90-150 parts of methyl vinyl silicone rubber matrix, 1-5 parts of structure control agent, 1-5 parts of reinforcing filler, 1-5 parts of softening modifier, 0.3-1.2 parts of silane coupling agent, and 0.1-0.6 parts of vulcanizing agent.

[0009] As further explained, the methyl vinyl silicone rubber matrix is ​​100-150 parts by weight.

[0010] As further explained, the structuring control agent is selected from at least one of hydroxyl silicone oil and hexamethyldisilazane.

[0011] As further explained, the reinforcing filler is silica.

[0012] As further explained, the vulcanizing agent is an odorless vulcanizing agent.

[0013] As a further explanation, the following steps are included:

[0014] S1: Add methyl vinyl silicone rubber matrix, reinforcing filler, and silane coupling agent to a mixer and mix at 80-120°C for 15-40 minutes;

[0015] S2: Cool down to below 60℃, add the structure control agent and softening regulator, and continue to mix for 10-30 minutes;

[0016] S3: Add vulcanizing agent and mix for 5-10 minutes;

[0017] S4: Mold the rubber compound into shape and vulcanize it at 150-200℃ for 1-10 minutes;

[0018] S5: After vulcanization, bake at 120℃ for 2 hours.

[0019] As a further explanation, the mixing described in S3 is low-speed mixing.

[0020] As a further explanation, the mixing described in S1 ensures that the filler is uniformly dispersed.

[0021] As a further explanation, the mixing described in S3 ensures that the vulcanizing agent is evenly distributed.

[0022] In summary, the present invention has the following beneficial effects: The present invention provides a hydrolysis-resistant food-grade silicone material with the slow rebound feel of TPR and its preparation method. Methyl vinyl silicone rubber is used as the matrix. Through the synergistic combination of structure control agent and softening regulator, the crosslinking network density and molecular chain slippage behavior of silicone rubber are precisely controlled, so that the recovery time of the material after compression deformation is extended to 6-15 seconds, perfectly replicating the soft, slow rebound decompression feel of TPR material. At the same time, relying on the high bond energy characteristics of Si-O bonds in the main chain of silicone rubber, the material does not show whitening, stickiness, or cracking after being soaked in boiling water for 48 hours, and the mechanical property retention rate reaches more than 90%. This fundamentally solves the industry pain points of traditional TPR toys being prone to hydrolysis and aging in humid and hot environments and having a short service life. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] This invention discloses a hydrolysis-resistant food-grade silicone material with the slow rebound feel of TPR and its preparation method. By weight, it comprises the following raw materials: 90-150 parts of methyl vinyl silicone rubber matrix, 1-5 parts of a structure control agent, 1-5 parts of reinforcing filler, 1-5 parts of a softening regulator, 0.3-1.2 parts of a silane coupling agent, and 0.1-0.6 parts of a vulcanizing agent. The methyl vinyl silicone rubber matrix comprises 100-150 parts by weight. The structure control agent is selected from at least one of hydroxyl silicone oil and hexamethyldisilazane. The reinforcing filler is silica. The vulcanizing agent is an odorless vulcanizing agent.

[0025] Specifically, methyl vinyl silicone rubber is used as the matrix material. The main chain of methyl vinyl silicone rubber molecules is composed of alternating Si-O-Si bonds, whose bond energy is significantly higher than that of C-C and C=C bonds, giving the material excellent heat aging resistance, UV aging resistance, and hydrolytic stability. Under long-term use or high temperature and humidity environments, the material of this invention will not suffer from the problems of molecular chain breakage and cross-linking network destruction caused by the oxidation of unsaturated double bonds or ester hydrolysis in TPR materials, thus effectively avoiding failure phenomena such as whitening, stickiness, cracking, and even powdering of the product surface.

[0026] Methyl vinyl silicone rubber is vulcanized and crosslinked using an odorless vulcanizing agent to form a three-dimensional network structure. The amount of vulcanizing agent is controlled at a low level of 0.1 to 0.6 parts, resulting in a moderate to low crosslinking density. This appropriate crosslinking density ensures sufficient structural integrity to maintain the shape of the product while providing ample space for the sliding and rearrangement of molecular chain segments under stress. When external force is applied to the material, the silicone rubber molecular chain segments stretch and slide relative to each other, absorbing and dissipating external energy. When the external force is removed, the elastic recovery force of the crosslinked network drives the molecular chain segments to slowly return to their equilibrium conformation, thereby achieving the mechanical response characteristic of "slow rebound".

[0027] Structure control agents and softening regulators synergistically regulate the interaction forces between silicone rubber molecular chains. Structure control agents (hydroxyl silicone oil and / or hexamethyldisilazane) react with the active silanol groups on the surface of silica, inhibiting hydrogen-bonded aggregation between silica particles and improving the uniformity of filler dispersion in the matrix. Furthermore, the active groups at the ends or side groups of their molecular chains can undergo condensation or addition reactions with the silanol groups or residual vinyl groups on the silicone rubber molecular chains, forming chemical bonds or strong physical entanglements between the filler and the matrix. This significantly inhibits the "structuring" phenomenon of silica fillers during storage or processing (i.e., filler aggregation leading to increased system viscosity and deteriorated processing performance), thereby ensuring the processing stability of the rubber compound and the consistency of product performance.

[0028] The addition of softening modifiers increases the inter-chain spacing of silicone rubber by inserting their molecular chains into the molecular chains, weakening van der Waals forces and dipole interactions between the chains. This lowers the glass transition temperature and the density of physical cross-linking points in the cross-linked network, effectively reducing material hardness and improving the mobility of molecular chain segments. This results in a soft, elastic feel in the finished product, and further enhances the slow rebound effect by extending the relaxation time of the molecular chain segments after the removal of external force. The synergistic effect of the structure control agent and the softening modifier causes the material's mechanical loss factor (tan δ) to exhibit a broadened loss peak with a moderate peak value near room temperature, corresponding to excellent damping performance and slow rebound characteristics.

[0029] In terms of filler reinforcement and interfacial chemistry, this invention selects silica as a reinforcing filler and performs surface modification treatment on it using a silane coupling agent. The hydrolyzable group at one end of the silane coupling agent molecule undergoes a condensation reaction with the silanol groups on the silica surface, forming a stable chemical bond; the organic functional groups (such as vinyl and methyl groups) at the other end have good compatibility with the silicone rubber matrix and can participate in vulcanization crosslinking reactions or form strong physical entanglements. This interfacial chemistry design allows silica particles to be uniformly dispersed at the nanoscale in the silicone rubber matrix and form a strong interfacial bond with the matrix through chemical bonds, effectively transferring and bearing stress, significantly improving the tensile strength, tear strength, and abrasion resistance of the material, overcoming the shortcomings of insufficient mechanical strength in traditional low-crosslink density silicone rubber.

[0030] The process includes the following steps: S1: Add the methyl vinyl silicone rubber matrix, reinforcing filler, and silane coupling agent to a mixer and mix at 80–120°C for 15–40 minutes; S2: Cool to below 60°C, add the structure control agent and softening regulator, and continue mixing for 10–30 minutes; S3: Add the vulcanizing agent and mix for 5–10 minutes; S4: Mold the rubber compound and vulcanize at 150–200°C for 1–10 minutes; S5: After vulcanization, bake a second time at 120°C for 2 hours. Mixing in S3 is done at a low speed. Mixing in S1 ensures uniform dispersion of the filler. Mixing in S3 ensures uniform distribution of the vulcanizing agent.

[0031] Specifically, regarding the synergistic effects of the processes, this invention employs a step-by-step mixing and segmented vulcanization process. First, the silicone rubber matrix, reinforcing filler, and silane coupling agent are mixed at 80–120°C. This temperature condition is beneficial for reducing the viscosity of the rubber compound, promoting filler dispersion, and providing sufficient activation energy for the condensation reaction between the silane coupling agent and the silica surface, achieving in-situ chemical modification of the filler surface. Subsequently, the temperature is lowered to below 60°C, and a structure control agent and softening regulator are added. The low temperature effectively avoids premature reaction consumption or volatilization loss of the structure control agent at high temperatures, ensuring its full function in inhibiting filler structure formation and regulating the interactions between molecular chains. Finally, the vulcanizing agent is added at low temperature and mixed at low speed to avoid shear heating and scorching, ensuring the vulcanizing agent is evenly distributed in the rubber compound without premature crosslinking. After compression molding, high-temperature rapid vulcanization is performed at 150–200°C, causing the peroxide to decompose and generate free radicals, which trigger addition crosslinking reactions on the vinyl side groups of the silicone rubber molecular chains, forming a stable C-C bond crosslinking network. After vulcanization, a secondary baking treatment is carried out at 120℃. This step promotes the full release of vulcanization byproducts (such as low molecular weight volatiles and residual peroxide decomposition products), and further relaxes and rearranges the silicone rubber molecular chains during the heat treatment process, eliminating internal stress and stabilizing the cross-linked network structure. At the same time, it promotes the unreacted structure control agents and softening regulators to continue to react with the matrix or filler surface, further optimizing the microstructure and macroscopic properties of the material.

[0032] This invention achieves a soft touch and slow rebound characteristics approaching those of TPR materials by synergistically controlling the crosslinking density, molecular chain mobility, filler dispersion state, and interfacial chemical bonding of silicone rubber. This is achieved while fully leveraging the inherent food-grade safety, hydrolysis resistance, and aging resistance of silicone materials. A moderately crosslinked network within the material provides structural support and elastic recovery. The synergistic effect of the structure control agent and softening regulator reduces inter-chain frictional resistance and prolongs stress relaxation time. The reinforced interface formed by silica and silane coupling agent provides sufficient mechanical strength to maintain durability for repeated use. This synergistic effect allows the material to slowly absorb and release energy during repeated compression, exhibiting an excellent decompression feel. Furthermore, it avoids common TPR material failures such as surface whitening, stickiness, cracking, powdering, and additive precipitation after long-term use, combining a slow rebound feel with food-grade safety and hygiene.

[0033] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0034] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A hydrolysis-resistant food-grade silicone material that combines the slow rebound feel of TPR, characterized in that, By weight, it includes the following ingredients: The composition includes 90-150 parts of methyl vinyl silicone rubber matrix, 1-5 parts of structure control agent, 1-5 parts of reinforcing filler, 1-5 parts of softening modifier, 0.3-1.2 parts of silane coupling agent, and 0.1-0.6 parts of vulcanizing agent.

2. The hydrolysis-resistant food-grade silicone material with TPR slow rebound feel according to claim 1, characterized in that: The methyl vinyl silicone rubber matrix is ​​100-150 parts by weight.

3. The hydrolysis-resistant food-grade silicone material with TPR slow rebound feel according to claim 1, characterized in that: The structuring control agent is selected from at least one of hydroxyl silicone oil and hexamethyldisilazane.

4. The hydrolysis-resistant food-grade silicone material with TPR slow rebound feel according to claim 1, characterized in that: The reinforcing filler is silica.

5. A hydrolysis-resistant food-grade silicone material with TPR slow rebound feel according to claim 1, characterized in that: The vulcanizing agent is an odorless vulcanizing agent.

6. The method for preparing the hydrolysis-resistant food-grade silicone material with slow rebound feel according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Add methyl vinyl silicone rubber matrix, reinforcing filler, and silane coupling agent to a mixer and mix at 80-120°C for 15-40 minutes; S2: Cool down to below 60℃, add the structure control agent and softening regulator, and continue to mix for 10-30 minutes; S3: Add vulcanizing agent and mix for 5-10 minutes; S4: Mold the rubber compound into shape and vulcanize it at 150-200℃ for 1-10 minutes; S5: After vulcanization, bake at 120℃ for 2 hours.

7. The hydrolysis-resistant food-grade silicone material with TPR slow rebound feel and its preparation method according to claim 6, characterized in that, The mixing described in S3 is low-speed mixing.

8. A hydrolysis-resistant food-grade silicone material with TPR slow rebound feel and its preparation method according to claim 6, characterized in that, The mixing described in S1 ensures that the filler is evenly dispersed.

9. A hydrolysis-resistant food-grade silicone material with TPR slow rebound feel and its preparation method according to claim 6, characterized in that, The mixing process described in S3 ensures that the vulcanizing agent is evenly distributed.