A solvent-resistant foaming material and its preparation method

Abstract

This invention discloses a solvent-resistant foaming material and its preparation method, relating to the technical field of polymeric rubber foaming materials. The solvent-resistant foaming material is prepared from the following raw materials in parts by weight: 90 parts of a base polymer, 5-25 parts of a chemical foaming agent, 0.5-5 parts of a crosslinking agent, 0.5-8 parts of a foaming aid, 5-40 parts of a filler, 10-30 parts of a solvent-resistant modifier, 0.5-5 parts of a processing aid, and 0.5-1.5 parts of an antioxidant. This invention solves the problem of easy swelling and deformation of traditional foaming materials in organic solvent environments through the synergistic effect of the base polymer (a 1:1 mixture of nitrile rubber and butadiene rubber) and the solvent-resistant modifier (such as polytetrafluoroethylene powder). This effectively reduces the volume swelling rate and mass change of the material in solvents, enhances its impermeability, and allows the material to maintain structural integrity during long-term contact with lubricating oils or alcohol solvents, thereby extending the service life of the seals.

Description

Technical Field

[0001] This invention relates to the field of polymer compound rubber foaming materials technology, specifically to a solvent-resistant foaming material and its preparation method. Background Technology

[0002] Foamed materials are widely used in automotive seals, industrial gaskets, and medical devices due to their lightweight, cushioning, and heat insulation properties. However, traditional rubber foamed materials are prone to swelling, deformation, and even dissolution when exposed to organic solvents (such as lubricating oils and alcohols) for extended periods, leading to seal failure and a sharp decline in mechanical properties. This has become a long-standing technical bottleneck, especially for seals that are constantly exposed to oily environments.

[0003] Meanwhile, the aging problem of foamed materials is also prominent. Conventional antioxidants tend to migrate and volatilize during the high-temperature foaming process, resulting in an incomplete anti-aging network inside the material. Furthermore, the porous nature of the foam structure further accelerates the penetration of oxygen and ozone, causing chain breakage and cross-linking failure. This manifests as surface powdering, hardening and cracking, a sharp decline in dynamic fatigue performance, and a shortened service life.

[0004] Therefore, developing a high-performance material that combines high solvent resistance, long-lasting anti-aging ability, and stable foaming structure is crucial for improving the reliability and lifespan of key sealing components. Summary of the Invention

[0005] The purpose of this invention is to provide a solvent-resistant foaming material and its preparation method. Through the synergistic effect of a specific base polymer and a fluorinated solvent-resistant modifier, combined with an antioxidant with optimized molecular structure and a staged processing technology, this invention solves the problems of existing foaming materials being prone to swelling and deformation in solvent environments, failure of the antioxidant system during high-temperature foaming, and poor stability of the cell structure. This invention achieves a combination of high solvent resistance, long-lasting anti-aging properties, and a uniform closed-cell structure.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a solvent-resistant foaming material, prepared from the following raw materials in parts by weight: 90 parts of base polymer, 5-25 parts of chemical foaming agent, 0.5-5 parts of crosslinking agent, 0.5-8 parts of foaming aid, 5-40 parts of filler, 10-30 parts of solvent-resistant modifier, 0.5-5 parts of processing aid, and 0.5-1.5 parts of antioxidant;

[0007] The antioxidant has the structure shown in Formula 1:

[0008] Equation 1 is as follows: ;

[0009] In Formula 1, R1 is a substituent, and R1 is any one of hydrogen, methyl, hydroxyl, fluorine, methyl ester group, or carbon atom in alkoxy groups of 1-3.

[0010] The base polymer is selected from: nitrile rubber and cis-butadiene rubber mixed in a 1:1 mass ratio;

[0011] The solvent-resistant modifier is selected from at least one of the following: polytetrafluoroethylene powder, perfluoropolyether, and chlorosulfonated polyethylene.

[0012] Furthermore, the chemical foaming agent is selected from at least one of azodicarbonamide, 4,4'-oxobisbenzenesulfonylhydrazine, p-toluenesulfonylhydrazine, and p-toluenesulfonamide.

[0013] Furthermore, the crosslinking agent is selected from at least one of dicumyl peroxide and bis-tert-butylperoxide.

[0014] Furthermore, the foaming agent is selected from at least one of zinc oxide, stearic acid, and urea.

[0015] Furthermore, the filler is selected from at least one of the following: calcium carbonate, talc, silica, carbon black, and diatomaceous earth.

[0016] Furthermore, the processing aid is selected from at least one of zinc stearate, paraffin wax, polyethylene wax, and silicone oil.

[0017] Furthermore, the antioxidant is selected from any one of the compounds shown in the following structures:

[0018] ;

[0019] ;

[0020] ;

[0021] .

[0022] A method for preparing a solvent-resistant foaming material includes the following steps:

[0023] (1) Internal mixing: The base polymer, filler, solvent-resistant modifier, antioxidant and processing aid are added to an internal mixer and mixed at 120-150℃ for 3-8 minutes to obtain mixture A;

[0024] (2) Open milling: Transfer the mixture A to an open mill, cool it to 60℃-80℃, add the chemical foaming agent, crosslinking agent and foaming aid, and mix evenly to obtain the compound;

[0025] (3) Foaming molding: The compound is placed in a mold and foamed at 160-190℃ and 5-15MPa pressure for 5-15 minutes. After cooling and demolding, a solvent-resistant foamed material is obtained.

[0026] Furthermore, the refining process in step (1) is carried out in two stages:

[0027] First stage: Mix the base polymer, filler and solvent-resistant modifier at 120-130℃ for 3-5 minutes;

[0028] Second stage: Add the antioxidant and processing aids, heat to 140-150℃ and continue mixing for 2-3 minutes.

[0029] Furthermore, the foaming molding in step (3) adopts a stepped heating procedure: first, the temperature is raised to 140-150℃ at 5-8℃ / min for pre-curing for 2-4 minutes; then, the temperature is raised to 160-190℃ at 3-5℃ / min for foaming and heat preservation; the cooling rate is controlled at 15-20℃ / min.

[0030] The NH structure in the antioxidant possesses lone pairs of electrons, which can efficiently capture alkyl and alkoxy radicals generated during material aging, interrupting the oxidation chain reaction. The fused conjugated system formed by the aromatic ring and heteroatoms (N, O) can disperse and stabilize the stable products generated after capturing free radicals, preventing them from initiating new oxidation reactions and improving anti-aging durability. The antioxidant also has a coordination effect, chelating residual metal ions (such as copper and iron ions) in the material, inhibiting metal ion-catalyzed oxidation reactions, and reducing accelerated aging caused by metal impurities.

[0031] This invention enhances solvent resistance through the synergistic effect of a basic polymer combination (nitrile rubber and butadiene rubber in a 1:1 ratio) and a solvent-resistant modifier: the polar cyano groups of nitrile rubber resist swelling in non-polar solvents, butadiene rubber compensates for elasticity, and fluorine-based materials migrate to the surface after dispersion during the mixing stage (120-150℃) to form a low surface energy barrier. Their highly electronegative fluorine elements form physical crosslinking points with the polar groups of the rubber, reducing the volume swelling rate in solvents. Long-lasting anti-aging is achieved through the synergistic effect of a specially structured antioxidant and a peroxide crosslinking agent: the antioxidant is added during the second stage of mixing. The molecules are fixed by a cross-linked network, inhibiting aging through a triple mechanism of capturing free radicals, stabilizing free radical products, and chelating metal ions. Simultaneously, the cross-linking agent constructs a stable network during the foaming stage (160-190℃) to reduce chain breakage and increase tensile strength retention. The cell structure is synergistically controlled through chemical foaming agents, fillers, and a stepped heating process: fillers are dispersed in the first stage of intensive mixing to enhance cell wall strength; the foaming agent uniformly decomposes into nuclei within the partially cross-linked matrix during the pre-curing stage at 140-150℃; and the stepped heating matches the bubble growth and cross-linking rate, combined with rapid cooling to lock in the structure. This achieves a synergistic breakthrough in solvent resistance, aging resistance, and cell structure stability.

[0032] Compared with the prior art, the beneficial effects of the present invention are:

[0033] 1. Significantly Improved Solvent Resistance: This invention solves the problem of easy swelling and deformation of traditional foamed materials in organic solvent environments through the synergistic effect of the base polymer (a 1:1 mixture of nitrile rubber and butadiene rubber) and the solvent-resistant modifier (such as polytetrafluoroethylene powder). This effectively reduces the volume swelling rate and mass change of the material in solvents, enhances its impermeability, and allows the material to maintain structural integrity during long-term contact with lubricating oils or alcohol solvents, thereby extending the service life of the seals.

[0034] 2. Enhanced Long-Term Anti-Aging Capacity: This invention employs a synergistic mechanism between a specific structured antioxidant and a peroxide crosslinking agent, solving the problem of antioxidant migration and volatilization during high-temperature foaming. This significantly slows down the aging process of the material, improving dynamic fatigue performance and tensile strength retention. The antioxidant forms a more durable anti-aging network through a triple mechanism of capturing free radicals, stabilizing free radical products, and chelating metal ions.

[0035] 3. Improved Cell Structure Stability: This invention optimizes the bubble nucleation and growth process through the synergistic control of chemical foaming agents, fillers, and a stepped heating process. This results in a more uniform and dense closed-cell structure, enhancing cell wall strength and overall material cushioning performance. Specifically, by matching bubble growth and crosslinking rates during the pre-curing stage, combined with a rapid cooling locking structure, the dimensional stability and mechanical property consistency of the material during the foaming process are improved. Detailed Implementation

[0036] The technical solution of the present invention will be clearly and completely described below in conjunction with the inventive content. 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.

[0037] Preparation Example 1

[0038] Preparation of antioxidant 1:

[0039] ;

[0040] 10 g of compound A and 8.50 g of compound B were dissolved in 120 ml of dichloromethane and stirred until evenly dispersed. Then, 14.43 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 6.14 g of 1-hydroxybenzotriazole were added. The mixture was reacted at 50 °C for 9 hours. The mixture was filtered through diatomaceous earth, concentrated, and evaporated to dryness. The filtrate was then purified by silica gel column chromatography using a mixture of n-heptane and petroleum ether as the eluent. After evaporation, 14.31 g of compound C was obtained.

[0041] ;

[0042] Under nitrogen protection, 14.31 g of compound C and 4.96 g of compound D were dissolved in 180 mL of a mixed solvent of 1,4-dioxane / diisopropylamine (120 mL / 60 mL). 0.13 g of palladium acetate, 0.30 g of 2-dicyclohexylphosphine-2',4',6'-triisopropylbiphenyl, and 0.30 g of CuI were added to the above system, and the reaction was carried out at 90 °C for 5 h. After the reaction was completed, the temperature was slightly lowered, and the mixture was filtered through diatomaceous earth to remove salts and catalyst. The reaction solution was concentrated, separated by silica gel column chromatography using a mixed solvent of n-heptane and ethyl acetate as the eluent, and evaporated to dryness to obtain 13.89 g of antioxidant 1.

[0043] Structural assessment:

[0044] Mass spectra of compound C: 471, measured using M / Z MS+1;

[0045] Mass spectrometry of antioxidant 1: 571, tested using M / Z MS+1;

[0046] NMR of antioxidant 1: 1 H NMR (Chloroform-d): δ 8.44 (d, 1H), 7.93 – 7.84 (m,2H), 7.72 (dd, 1H), 7.59 (dd, 1H), 7.53 – 7.39 (m, 7H), 7.39 – 7.27 (m, 4H), 7.17 (s, 2H).

[0047] Preparation Examples 2-6

[0048] In Preparation Examples 2-6, antioxidants were prepared by referring to the preparation method of Preparation Example 1, except that compound B was replaced, and the rest remained the same as in Preparation Example 1. For details, please refer to Table 1.

[0049] Table 1.

[0050]

[0051] Example 1

[0052] Preparation of a solvent-resistant foaming material:

[0053] 1. Raw material composition:

[0054] Base polymer: 90 parts, composed of nitrile rubber and butadiene rubber in a 1:1 mass ratio. The nitrile rubber was purchased from Wuhan Xinyang Ruihe Chemical Technology Co., Ltd., and the butadiene rubber was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0055] Chemical foaming agent: 15 parts, selected from: azodicarbonamide, purchased from: Xingyang No.10 Chemical Co., Ltd.;

[0056] Crosslinking agent: 2 parts, selected from: dicumyl peroxide, purchased from: Jiangsu Daoming Chemical Co., Ltd.;

[0057] Foaming agent: 4 parts, selected from: zinc oxide, purchased from: Shanghai Aladdin Biochemical Technology Co., Ltd.;

[0058] Filler: 20 parts, selected from calcium carbonate, purchased from Shanghai Nuocheng Pharmaceutical Co., Ltd.;

[0059] Solvent-resistant modifier: 20 parts, selected from: polytetrafluoroethylene powder, purchased from: Fuzhou Taipuda New Material Co., Ltd.;

[0060] Processing aids: 3 parts, selected from: zinc stearate, purchased from: Dongguan Hanwei Technology Co., Ltd.;

[0061] Antioxidant: 1 part, selected from: Antioxidant 1, synthesized by the method of Preparation Example 1;

[0062] 2. Preparation method:

[0063] (1) Internal mixing: The base polymer (mixture of nitrile rubber and butadiene rubber), filler (calcium carbonate) and solvent-resistant modifier (polytetrafluoroethylene powder) are added to an internal mixer and mixed at 125°C for 4 minutes; the antioxidant (antioxidant 1) and processing aid (zinc stearate) are added, and the temperature is raised to 145°C and mixed for another 2.5 minutes to obtain mixture A;

[0064] (2) Open milling: Transfer mixture A to an open mill, cool it to 70°C, add the chemical foaming agent (azodicarbonamide), crosslinking agent (diisopropylbenzene peroxide) and foaming aid (zinc oxide), and mix evenly to obtain a compound;

[0065] (3) Foaming molding: The compound is placed in a mold and pressure of 8MPa is applied. The following procedure is followed: First, the temperature is raised to 145°C at a heating rate of 7°C / min and pre-cured for 3 minutes; then the temperature is raised to 175°C at a heating rate of 4°C / min and foamed for 10 minutes; then the temperature is lowered to room temperature at a cooling rate of 18°C / min and then demolded to obtain the solvent-resistant foamed material.

[0066] Examples 2-6

[0067] In Examples 2-6, a solvent-resistant foaming material was prepared sequentially. The preparation method of Example 1 was followed, except that the antioxidant was replaced with the antioxidant prepared in Examples 2-6, and the rest remained the same as in Example 1.

[0068] Comparative Example 1

[0069] A solvent-resistant foaming material was prepared by referring to the preparation method of Example 1, except that the antioxidant was replaced with... (Antioxidant MC), the rest is the same as in Example 1.

[0070] Comparative Example 2

[0071] The preparation of a solvent-resistant foaming material is carried out by referring to the preparation method of Example 1, except that the antioxidant is replaced with antioxidant AW, and the rest is the same as in Example 1.

[0072] Comparative Example 3

[0073] The preparation of a solvent-resistant foaming material is the same as in Example 1, except that the antioxidant is not added.

[0074] Comparative Example 4

[0075] The preparation of a solvent-resistant foaming material is carried out according to the preparation method of Example 1, except that polytetrafluoroethylene powder is not added, and the rest is the same as in Example 1.

[0076] Performance testing:

[0077] 1. Tensile Strength: The tensile strength was tested using a universal tensile testing machine according to the method specified in GB / T 528-2009. The tensile rate was 500 mm / min, the test temperature was 23℃, and the effective part length of the specimen was 25 mm and the width was 6 mm. The data are shown in Table 2.

[0078] 2. Solvent Resistance Test: Solvent resistance was tested according to the method specified in GB / T 1690-2010. The test conditions were 23℃ for 48 hours, and the test solvents included toluene and acetone. The rate of change in test mass was recorded. The data are shown in Table 2.

[0079] 3. Anti-aging test: Following the method specified in GB / T 3512-2014, the heat aging temperature was 100±2℃, the heat aging time was 336 hours, and the tensile strength retention rate (%) was tested. The data are shown in Table 2.

[0080] Table 2.

[0081]

[0082] The example group (using the antioxidants and solvent-resistant modifiers specific to this invention) exhibited significant advantages in overall performance, including higher tensile strength, lower solvent absorption rate (reflected in the mass change rates of toluene and acetone), and excellent anti-aging ability (high tensile strength retention rate), indicating that the material achieved synergistic optimization in mechanical strength, solvent resistance, and long-term stability. In contrast, in the comparative examples: Comparative Examples 1 and 2, when using alternative antioxidants (such as MC or AW), showed a significant decrease in anti-aging performance, demonstrating the key role of antioxidant structural design in the long-term protection of the material; Comparative Example 3, completely lacking antioxidants, resulted in a comprehensive deterioration in performance, especially in anti-aging; while Comparative Example 4, omitting the solvent-resistant modifier, showed a significant degradation in solvent resistance, but relatively preserved anti-aging performance, highlighting the core contribution of the solvent-resistant modifier to solvent resistance. Overall, this trend confirms that the synergistic effect of the antioxidants and solvent-resistant modifiers of this invention is the decisive factor in improving the overall performance of the material.

[0083] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A solvent resistant foamed material, characterized in that, Prepared from the following raw materials by mass: base polymer 90 parts, chemical foaming agent 5-25 parts, crosslinking agent 0.5-5 parts, foaming aid 0.5-8 parts, filler 5-40 parts, solvent resistance modifier 10-30 parts, processing aid 0.5-5 parts, antioxidant 0.5-1.5 parts; The antioxidant is a structure shown in formula 1; The formula 1 is: ; R1 in formula 1 is a substituent, and R1 is any one of hydrogen, methyl, hydroxyl, fluorine, methyl ester, and alkoxyl with 1-3 carbon atoms; The base polymer is selected from the group consisting of butyl nitrile rubber and cis-butadiene rubber mixed in a mass ratio of 1:1; The solvent resistance modifier is selected from at least one of polytetrafluoroethylene powder, perfluoropolyether, and chlorosulfonated polyethylene.

2. A solvent resistant foam material as claimed in claim 1, wherein, The chemical foaming agent is selected from at least one of azodicarbonamide, 4,4'-oxybisbenzenesulfonylhydrazide, p-toluenesulfonylhydrazide, and p-toluenesulfonylurea.

3. A solvent resistant foam material as claimed in claim 1, wherein, The crosslinking agent is selected from at least one of dicumyl peroxide and bis-tert-butyl peroxyisopropylbenzene.

4. A solvent resistant foam material as claimed in claim 1, wherein, The foaming aid is selected from at least one of zinc oxide, stearic acid, and urea.

5. A solvent resistant foam material as claimed in claim 1, wherein, The filler is selected from at least one of calcium carbonate, talc, white carbon black, carbon black, and diatomite.

6. A solvent resistant foam material as claimed in claim 1, wherein, The processing aid is selected from at least one of zinc stearate, paraffin wax, polyethylene wax, and silicone oil.

7. A solvent resistant foam material as claimed in claim 1, wherein, The antioxidant is selected from any one of the compounds shown in the following structures: ； ； ； 。 8. A process for the preparation of a solvent resistant foam material as claimed in any one of claims 1 to 7, characterised in that, The method comprises the following steps: (1) Internal mixing: the base polymer, filler, solvent resistance modifier, antioxidant, and processing aid are added to an internal mixer, mixed at 120-150°C for 3-8 minutes to obtain a mixture A; (2) Open mixing: the mixture A is transferred to an open mill, cooled to 60-80°C, and the chemical foaming agent, crosslinking agent, and foaming aid are added and uniformly mixed to obtain a mixed rubber; (3) Foaming molding: the mixed rubber is placed in a mold, foamed at 160-190°C and a pressure of 5-15 MPa for 5-15 minutes, cooled, and demolded to obtain a solvent-resistant foaming material.

9. A process for preparing a solvent resistant foam material as claimed in claim 8, wherein, The internal mixing in step (1) is carried out in two stages: First stage: the base polymer, filler, and solvent resistance modifier are mixed at 120-130°C for 3-5 minutes; Second stage: the antioxidant and processing aid are added, and the temperature is increased to 140-150°C for continued mixing for 2-3 minutes.

10. A process for preparing a solvent resistant foam material as claimed in claim 8, wherein, The foaming molding in step (3) adopts a stepwise temperature rising program: first, the temperature is increased to 140-150°C at a rate of 5-8°C / min for pre-curing for 2-4 minutes; then, the temperature is increased to 160-190°C at a rate of 3-5°C / min for foaming and curing; and the cooling rate is controlled at 15-20°C / min.

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