PBT (polybutylene terephthalate) encapsulating material resistant to damp-heat aging and preparation method of PBT encapsulating material

Abstract

The invention belongs to the field of high polymer materials, and particularly relates to a hygrothermal aging-resistant PBT (polybutylene terephthalate) encapsulating material and a preparation method thereof. Through the polar compatibility of the thermoplastic polyester elastomer and PBT, the reactive bonding of the epoxy group of the epoxy modified polysiloxane resin and the PBT end group (-OH / -COOH), and the ultralow melt viscosity synergistic effect of CBT, the cohesiveness with the PBT base material is significantly improved. By combining a long-chain organic silicon hydrophobic barrier and a carboxyl capturing function of polymeric carbodiimide (anti-hydrolysis agent), the material is endowed with excellent damp-heat aging resistance. The material is adjustable in hardness, has excellent mechanical properties and high processing fluidity, is simple in preparation process, is suitable for industrial production, and is particularly suitable for encapsulation application in a high-damp-heat environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high polymer materials, and particularly relates to a PBT encapsulating material resistant to wet heat aging and a preparation method thereof. BACKGROUND

[0002] Polybutylene terephthalate (PBT) is a crystalline thermoplastic polyester made by polycondensation of terephthalic acid and 1,4-butanediol. As one of the five engineering plastics, PBT has excellent heat resistance, high impact strength, good self-lubricating property and wear resistance, and outstanding dimensional stability, and is widely used in automobile parts, mechanical equipment, precision instruments, electronic appliances and textile fields.

[0003] However, PBT material is rigid and hard, and has poor touch feeling in handheld application scenarios. In order to improve user experience, the industry generally adopts thermoplastic elastomer (TPE) to overmold (i.e., encapsulation technology) PBT substrate. This technology bonds TPE melt to the surface of PBT through injection molding to form a composite part with structural strength and comfortable touch feeling. The soft TPE coating layer can significantly improve the holding comfort, enhance the slip resistance and absorb vibration, thereby improving the product durability and human-computer interaction performance.

[0004] PBT is difficult to be rapidly encapsulated and effectively bonded due to its high polarity, high melting point (usually >220℃) and rapid crystallization characteristics. Although existing technologies have tried to improve it, there are still significant defects: CN102181169A improves the polarity of TPE by adding engineering plastics to enhance the bonding of PBT, but the high melting point engineering plastics require higher processing temperature, which causes the risk of component thermal degradation; CN112552658B improves the encapsulation by modifying the PBT substrate, but its processing temperature needs to be above 270℃, which severely limits the selection range of TPE (most TPEs have a temperature resistance <250℃); CN114736506B uses plasticizers to improve the flowability of TPU to enhance bonding, but plasticizers are prone to precipitation and cause a significant decrease in the mechanical properties of the material.

[0005] Existing solutions generally rely on thermoplastic polyester elastomer (TPEE) or thermoplastic polyurethane (TPU) to improve the polarity of TPE, but both have poor resistance to wet heat aging: when used for a long time in a high temperature and high humidity environment, the molecular chain is prone to hydrolysis and rupture, resulting in a sharp decline in the mechanical properties of the TPE coating layer and the failure of the interfacial adhesion between TPE and PBT, which eventually leads to peeling or cracking of the encapsulation layer. This defect seriously restricts the application of PBT encapsulation parts in engine compartments, outdoor electronic devices, high-humidity working instruments and other fields.

[0006] Therefore, it is necessary to develop a TPE material that has strong adhesion to PBT and strong resistance to wet heat aging. SUMMARY

[0007] In order to solve the problems in the prior art, the application provides a moisture and heat aging resistant PBT encapsulating material and a preparation method thereof.

[0008] The first object of the application is achieved by the following technical scheme:

[0009] The moisture and heat aging resistant PBT encapsulating material comprises the following raw materials:

[0010] Thermoplastic polyester elastomer: 25-60 parts;

[0011] Epoxy modified polysiloxane resin: 2-10 parts;

[0012] SEBS: 10-30 parts;

[0013] White oil: 10-30 parts;

[0014] Cyclic polyester oligomer: 0.5-3 parts;

[0015] Compatibility agent: 4-10 parts;

[0016] Inorganic filler: 0-20 parts;

[0017] Antioxidant: 0.1-2 parts;

[0018] Hydrolysis resistant agent: 0.1-2 parts.

[0019] Preferably, the thermoplastic polyester elastomer is one or more of polyester type polyester elastomer or polyether type polyester elastomer, and the hardness range is 20-50D.

[0020] Further preferably, the hard segment of the thermoplastic polyester elastomer is PBT, and the soft segment is polyether.

[0021] Further preferably, the thermoplastic polyester elastomer ranges from 25D to 40D, and the melting point is less than 190 DEG C.

[0022] Preferably, the epoxy modified polysiloxane resin is one or more of polysiloxane resin containing epoxy groups on the main chain, polysiloxane resin containing epoxy groups on the side chain, and polysiloxane resin containing epoxy groups on both the main chain and the side chain.

[0023] Further preferably, the epoxy modified polysiloxane resin contains long-chain organic silicon segments.

[0024] More preferably, the epoxy-modified polysiloxane resin has a molecular weight of 400-8000 g / mol and an epoxy equivalent weight of 100-4000 g / eq.

[0025] Preferably, the SEBS refers to a styrene-ethylene-butylene-styrene block copolymer. Preferably, the number average molecular weight of the SEBS is 100,000-250,000, and the styrene content is 25 wt%-40 wt%.

[0026] This solution combines thermoplastic polyester elastomers, epoxy-modified polysiloxane resins, and SEBS to enhance the system's coating effectiveness on PBT. Thermoplastic elastomers synthesized with PBT as the hard segment and polyester or polyether as the soft segment offer excellent compatibility with PBT resin, while polyether exhibits superior water resistance. The epoxy-modified polysiloxane resins allow the epoxy groups to react with the terminal hydroxyl and carboxyl groups of PBT during the encapsulation process, thereby increasing the interaction between the thermoplastic elastomer (TPE) and PBT interfaces. The long-chain silicone segments increase the hydrophobicity of the TPE material, preventing water molecules from penetrating from the TPE surface into the thermoplastic polyester elastomer molecular segments. SEBS with a number-average molecular weight between 100,000 and 250,000 and a styrene content between 25% and 40% provides superior strength and facilitates processing.

[0027] Preferably, the flash point of the white oil is above 200°C and the kinematic viscosity is 10-100 mm at 40°C. 2 / s.

[0028] More preferably, the white oil is white oil 50#.

[0029] Preferably, the cyclic polyester oligomer is cyclic butylene terephthalate (CBT).

[0030] More preferably, the molecular formula of the cyclic polyester oligomer is (C 12 H 12 O4) n , where n=2-6.

[0031] The CBT resin selected in this solution has good compatibility with PBT, low viscosity after heating, and excellent fluidity. It can improve the fluidity of the system so that the TPE melt can better infiltrate the PBT surface during coating, thereby improving the bonding effect of the system without significantly affecting other properties of the TPE material.

[0032] Preferably, the compatibilizer is one or more of maleic anhydride grafted PP, maleic anhydride grafted PE, maleic anhydride grafted POE, maleic anhydride grafted SEBS, and maleic anhydride grafted EPDM.

[0033] Further preferably, the compatilizer is SEBS grafted with maleic anhydride (SEBS-MAH) with a grafting rate of maleic anhydride of ≥1wt% and a melt index of 230℃ / 5kg of ≥10g / min.

[0034] The SEBS grafted with maleic anhydride used in the present application can increase the compatibility between the components of the system and avoid delamination of the TPE material.

[0035] Preferably, the inorganic filler is one or more of calcium carbonate, talc, wollastonite, kaolin, mica, diatomite, carbon black, and silicon dioxide.

[0036] Further preferably, the inorganic filler is light calcium carbonate.

[0037] Preferably, the antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants, thio antioxidants, and hindered amine antioxidants.

[0038] Further preferably, the antioxidant is a hindered phenol antioxidant.

[0039] Preferably, the anti-hydrolysis agent is one or more of monomeric carbodiimides, polymeric carbodiimides, and liquid carbodiimides.

[0040] Further preferably, the anti-hydrolysis agent is a polymeric carbodiimide.

[0041] The anti-hydrolysis agent used in the present application can react with the carboxyl groups produced by the hydrolysis of the ester groups in the thermoplastic polyester elastomer and produce stable ureide, thereby further improving the stability of the TPE material under humid heat conditions.

[0042] The second object of the present application is achieved by the following technical solution:

[0043] A method for preparing the PBT encapsulating material resistant to humid heat aging as described above, comprising the following steps:

[0044] a) weighing each component according to the weight ratio, adding SEBS and white oil into a high-speed mixer until the SEBS particles are completely swollen and no free white oil is visible, forming a pre-swollen SEBS matrix;

[0045] b) adding thermoplastic polyester elastomer, epoxy-modified polysiloxane resin, cyclic polyester oligomer, compatilizer, inorganic filler, antioxidant, and anti-hydrolysis agent into the pre-swollen SEBS matrix obtained in step a) and continuing to stir until a homogeneous premix without visible agglomerates is formed;

[0046] c) adding the homogeneous premix obtained in step b) into a twin-screw extruder, and after shearing, melt plasticizing, extruding and granulating by the twin-screw extruder, homogenizing to obtain the PBT encapsulating material resistant to humid heat aging.

[0047] Preferably, in step a), the stirring speed is 200-500 r / min.

[0048] Preferably, in step c), the screw speed is 300-500 r / min, and the processing temperature of each region is 180-230℃.

[0049] Compared with the prior art, the present application has the following advantages:

[0050] 1. The PBT encapsulating material provided by the present application is blended from thermoplastic polyester elastomer, epoxy-modified polysiloxane resin, SEBS, cyclic polyester oligomer, compatibility agent, anti-hydrolysis agent, white oil, inorganic filler and antioxidant, and has a hardness controllable in the range of 45-85A, excellent mechanical properties (tensile strength ≥ 5 MPa) and high processing fluidity (melt index ≥ 18 g / 10 min, 230℃ / 2.16 kg).

[0051] 2. The present application effectively improves the bonding effect of TPE material through the polar compatibility mechanism of thermoplastic polyester elastomer and PBT, the epoxy group-PBT end bond reactivity bonding (-OH / -COOH) of epoxy-modified polysiloxane resin, and the synergistic effect of the ultra-low melt viscosity characteristics of cyclic polyester oligomer (CBT), and the peel strength is greater than 4 KN / m.

[0052] 3. The present application uses thermoplastic polyester elastomer with PBT as hard segment and polyether as soft segment, combines the long-chain organic silicon hydrophobic barrier of epoxy-modified polysiloxane resin and the carboxyl capture function of polymeric carbodiimide, so that the material has a tensile strength retention rate ≥ 96%, an elongation at break retention rate ≥ 90%, and a peel strength retention rate ≥ 77% after 1000 hours of damp heat aging at 85℃ / 95% RH.

[0053] 4. The PBT encapsulating material of the present application has a simple preparation process, is easy to operate, is suitable for industrial production, and can ensure good encapsulating effect and mechanical properties in high humidity and heat environment conditions. DETAILED DESCRIPTION

[0054] The concept, specific structure and technical effects of the present application will be described below in conjunction with examples for a clear and complete understanding of the purpose, scheme and effects of the present application. It should be noted that the examples in the present application and the features in the examples can be combined with each other without conflict.

[0055] In the following examples and comparative examples, the raw materials used are commercially available unless otherwise specified.

[0056] SEBS: SEBS YH502 produced by Yueyang Petrochemical and SEBS 6153 produced by Tai Xiang.

[0057] White oil: 50# white oil produced by Zhejiang Zhengxin Petroleum Technology.

[0058] Thermoplastic polyester elastomer: TPEE L4020 produced by Jiangsu Keyile New Material Technology Co., Ltd., and TPEE H88AMG produced by Jiangyin Hechuang Elastomer New Material Technology Co., Ltd.

[0059] Epoxy-modified polysiloxane resin: produced by Evonik Industries EF.

[0060] Cyclic polyester oligomer: CBT 100 produced by Cyclics.

[0061] Compatibilizer: SEBS grafted maleic anhydride SEBS-MAH 7126 produced by TSRC and SEBS grafted maleic anhydride SEBS-MAH FG1901 produced by Kraton.

[0062] Inorganic filler: Light calcium carbonate WN100 produced by Changzhou Calcium Carbonate Co., Ltd.

[0063] Antioxidant: Antioxidant RIANOX 245 produced by Tianjin Li'anlong New Materials Co., Ltd.

[0064] Anti-hydrolysis agent: HYMax210 and HYMax213 produced by Shanghai Langyi Functional Materials Co., Ltd.

[0065] Example 1

[0066] The method for preparing the PBT encapsulating material resistant to moisture and heat aging of Example 1 comprises the following steps:

[0067] a) The raw material components and weight proportions of Example 1 are shown in Table 1. Each component was weighed according to the weight ratio, and SEBS and white oil were added to a high-speed mixer and stirred at a speed of 300 r / min until the SEBS particles were completely swollen and no free white oil was visible, thereby forming a pre-swollen SEBS matrix.

[0068] b) adding a thermoplastic polyester elastomer, an epoxy-modified polysiloxane resin, a cyclic polyester oligomer, a compatibilizer, an inorganic filler, an antioxidant, and an anti-hydrolysis agent to the pre-swollen SEBS matrix obtained in step a), and continuing stirring at a speed of 300 r / min until a homogeneous premix is ​​formed without visible agglomerates;

[0069] c) adding the homogeneous premix obtained in step b) into a twin-screw extruder at a screw speed of 350 r / min and a processing temperature of 200° C., subjecting the premix to shearing, melt plasticization, extrusion granulation, and homogenization to obtain a PBT encapsulating material resistant to moisture and heat aging.

[0070] Example 2

[0071] The preparation method of the moisture and heat aging resistant PBT encapsulating material of Example 2 comprises the following steps:

[0072] a) The raw material components and weight fractions of Example 2 are shown in Table 1. Each component is weighed according to the weight ratio. SEBS and white oil are added to a high-speed mixer and stirred at a speed of 300 r / min until the SEBS particles are completely swollen and no visible free white oil is present, forming a pre-swollen SEBS matrix.

[0073] b) The pre-swollen SEBS matrix obtained in step a) is added with thermoplastic polyester elastomer, epoxy-modified polysiloxane resin, cyclic polyester oligomer, compatibilizer, inorganic filler, antioxidant, and hydrolysis inhibitor. Stirring is continued at a speed of 300 r / min until a homogeneous premix without visible agglomerates is formed.

[0074] c) The homogeneous premix obtained in step b) is added to a twin-screw extruder with a screw speed of 350 r / min and a processing temperature of 210°C. After shearing, melting, plasticizing, and extruding and granulating in the twin-screw extruder, the moisture and heat aging resistant PBT encapsulating material is obtained.

[0075] Example 3

[0076] The preparation method of the moisture and heat aging resistant PBT encapsulating material of Example 3 comprises the following steps:

[0077] a) The raw material components and weight fractions of Example 3 are shown in Table 1. Each component is weighed according to the weight ratio. SEBS and white oil are added to a high-speed mixer and stirred at a speed of 300 r / min until the SEBS particles are completely swollen and no visible free white oil is present, forming a pre-swollen SEBS matrix.

[0078] b) The pre-swollen SEBS matrix obtained in step a) is added with thermoplastic polyester elastomer, epoxy-modified polysiloxane resin, cyclic polyester oligomer, compatibilizer, inorganic filler, antioxidant, and hydrolysis inhibitor. Stirring is continued at a speed of 300 r / min until a homogeneous premix without visible agglomerates is formed.

[0079] c) The homogeneous premix obtained in step b) is added to a twin-screw extruder with a screw speed of 300 r / min and a processing temperature of 190°C. After shearing, melting, plasticizing, and extruding and granulating in the twin-screw extruder, the moisture and heat aging resistant PBT encapsulating material is obtained.

[0080] Example 4

[0081] The preparation method of the moisture and heat aging resistant PBT encapsulating material of Example 4 comprises the following steps:

[0082] a) The raw material components and weight proportions of Example 4 are shown in Table 1. The components were weighed according to the weight ratio, and SEBS and white oil were added to a high-speed mixer and stirred at a speed of 300 r / min until the SEBS particles were completely swollen and no free white oil was visible, thereby forming a pre-swollen SEBS matrix.

[0083] b) adding a thermoplastic polyester elastomer, an epoxy-modified polysiloxane resin, a cyclic polyester oligomer, a compatibilizer, an inorganic filler, an antioxidant, and an anti-hydrolysis agent to the pre-swollen SEBS matrix obtained in step a), and continuing stirring at a speed of 300 r / min until a homogeneous premix is ​​formed without visible agglomerates;

[0084] c) adding the homogeneous premix obtained in step b) into a twin-screw extruder at a screw speed of 400 r / min and a processing temperature of 200° C., subjecting the premix to shearing, melt plasticization, extrusion granulation, and homogenization to obtain a PBT encapsulating material resistant to moisture and heat aging.

[0085] Example 5

[0086] The method for preparing the PBT encapsulating material resistant to moisture and heat aging of Example 5 comprises the following steps:

[0087] a) The raw material components and weight proportions of Example 5 are shown in Table 1. The components were weighed according to the weight ratio, and SEBS and white oil were added to a high-speed mixer and stirred at a speed of 300 r / min until the SEBS particles were completely swollen and no free white oil was visible, forming a pre-swollen SEBS matrix.

[0088] b) adding a thermoplastic polyester elastomer, an epoxy-modified polysiloxane resin, a cyclic polyester oligomer, a compatibilizer, an inorganic filler, an antioxidant, and an anti-hydrolysis agent to the pre-swollen SEBS matrix obtained in step a), and continuing stirring at a speed of 300 r / min until a homogeneous premix is ​​formed without visible agglomerates;

[0089] c) adding the homogeneous premix obtained in step b) into a twin-screw extruder at a screw speed of 400 r / min and a processing temperature of 210° C., and subjecting the mixture to shearing, melt plasticization, extrusion granulation, and homogenization to produce a PBT encapsulating material resistant to moisture and heat aging.

[0090] Comparative Example 1

[0091] In the preparation method of the PBT encapsulating material of Comparative Example 1, steps b) to c) are the same as in Example 1. In step a), the raw material components and weight proportions are as shown in Table 2, except that no thermoplastic polyester elastomer is added.

[0092] Comparative Example 2

[0093] In the preparation method of the PBT encapsulating material of Comparative Example 2, steps b) to c) are the same as in Example 2. In step a), the raw material components and weight proportions are as shown in Table 2, except that no epoxy-modified polysiloxane is added.

[0094] Comparative Example 3

[0095] In the preparation method of the PBT encapsulating material of Comparative Example 3, steps b) to c) are the same as those of Example 3. In step a), the raw material components and weight fractions are as shown in Table 2, except that no cyclic polyester oligomer is added.

[0096] Comparative Example 4

[0097] In the preparation method of the PBT encapsulating material of Comparative Example 4, steps b) to c) are the same as in Example 4. In step a), the raw material components and weight proportions are as shown in Table 2, except that the thermoplastic polyester elastomer used is a thermoplastic polyester elastomer having a hard segment of PBT and a soft segment of polyester (TPEE ZY2510 produced by Huashuo Technology Co., Ltd.).

[0098] Comparative Example 5

[0099] In the preparation method of the PBT encapsulating material of Comparative Example 5, steps b) to c) are the same as those of Example 5. In step a), the raw material components and weight proportions are as shown in Table 2, except that no anti-hydrolysis agent is added.

[0100] Comparative Example 6

[0101] In the preparation method of the PBT encapsulating material of Comparative Example 6, steps b) to c) are the same as in Example 1. In step a), the raw material components and weight proportions are as shown in Table 2, except that the styrene content of SEBS is 13% (SBESYH688 produced by Yueyang Petrochemical).

[0102] Comparative Example 7

[0103] In the preparation method of the PBT encapsulating material of Comparative Example 7, steps b) to c) are the same as in Example 1. In step a), the raw material components and weight proportions are as shown in Table 2, except that the styrene content of SEBS is 53% (SBESYH512 produced by Yueyang Petrochemical).

[0104] Table 1 Raw material formula of TPE materials of Examples 1-5

[0105]

[0106] Table 2 Raw material formula of TPE materials of comparative examples 1-5

[0107]

[0108] The TPE materials prepared in Examples 1-5 and Comparative Examples 1-7 were subjected to performance tests. The results are shown in Table 3. The test methods and standards are as follows:

[0109] Hardness test standard: ASTM D2240;

[0110] Specific gravity test standard: ASTM D297;

[0111] Melt index test standard: ASTM D1238 (210℃ / 2.16kg);

[0112] Tensile strength and elongation at break test standard: ASTM D412;

[0113] Water contact angle test standard: ASTM D724; the larger the water contact angle, the more hydrophobic the material surface is;

[0114] Peel strength test method and test standard: After PBT is injection molded into a standard frame, it is dried at 110°C for 5 hours. Then the prepared TPE material is injection molded and bonded to the PBT frame at 230°C. After cooling to room temperature and standing for 24 hours, the peel strength is tested according to standard ASTM 903. The greater the peel strength, the better the surface encapsulation adhesion effect;

[0115] Test method and test standard for resistance to moisture and heat aging: After the prepared TPE material is injection molded into standard specimens, the tensile strength, elongation at break and peel strength are measured. The samples are then subjected to moisture and heat aging treatment for 1000 hours in a constant temperature and humidity chamber at a temperature of 85°C and a humidity of 95%. After being taken out, the samples are placed in an environment at room temperature of 25°C and a humidity of 50% for 24 hours, and the tensile strength, elongation at break and peel strength are measured again. The data before and after moisture and heat aging treatment are compared to obtain the tensile strength retention rate and elongation at break retention rate. The higher the tensile strength retention rate, elongation at break retention rate and peel strength after aging, the better the moisture and heat aging resistance and the better the stability in use under high humidity and heat conditions.

[0116] Table 3 TPE material performance data of Examples 1-5 and Comparative Examples 1-7

[0117]

[0118] As shown in Table 3, the hardness of the TPE material prepared in the application can be adjusted in the range of 45-85A, the mechanical properties are good, and the processing fluidity is good. After the TPE material is injection molded to cover the PBT skeleton, the peeling strength is greater than 4KN / m, which indicates that the bonding between the TPE material and the PBT is firm, and the effect of encapsulation is good. After 1000 hours of hygrothermal aging (temperature of 85℃, humidity of 95%), the tensile strength retention rate and the elongation at break retention rate of the TPE material are both above 90%, and the peeling strength is still above 3KN / m, which can still effectively bond the PBT, indicating that the material has excellent hygrothermal aging resistance and can be used stably for a long time in a high-humidity environment.

[0119] As shown by the comparison between Comparative Example 1 and Comparative Example 1, when the thermoplastic polyester elastomer is not used, the polarity gap between the TPE material system and the PBT segment is large, the compatibility between the two is poor, which leads to insufficient interfacial bonding force and difficulty in encapsulation.

[0120] As shown by the comparison between Comparative Example 2 and Comparative Example 2, when the epoxy-modified polysiloxane is not used, the further reaction between the epoxy group and the terminal hydroxyl group and the terminal carboxyl group of the PBT is lacking, which leads to a decrease in the surface bonding force of the TPE and PBT, and a decrease in the peeling strength. The addition of the epoxy-modified polysiloxane introduces a hydrophobic long-chain silicone segment, which increases the water contact angle of the TPE material from 83° to 103°, effectively improving the hydrophobicity and hygrothermal aging resistance of the material.

[0121] As shown by the comparison between Comparative Example 3 and Comparative Example 3, when the cyclic polyester oligomer is not used, the flowability of the TPE material is greatly reduced, the melt cannot rapidly spread and infiltrate on the surface of the PBT during injection molding, which leads to a decrease in the peeling strength and a decrease in the encapsulation effect.

[0122] As shown by the comparison between Comparative Example 4 and Comparative Example 4, when the thermoplastic polyester elastomer with PBT as the hard segment and polyester as the soft segment is used, the ester group is more prone to hydrolysis under hygrothermal conditions, which leads to a low tensile strength retention rate and elongation at break retention rate of the TPE material after 1000 hours of hygrothermal aging, and a decrease in the encapsulation strength to below 3KN / m after aging, which results in poor stability in practical application.

[0123] As shown by the comparison between Comparative Example 5 and Comparative Example 5, when the anti-hydrolysis agent is not used, the chain segment hydrolysis during the hygrothermal aging process cannot be effectively inhibited, which leads to a significantly greater attenuation of the mechanical properties and peeling strength after aging than in Example 5.

[0124] From the comparison of Example 1 with Comparative Examples 6 and 7, it can be seen that when the content of styrene is less than 25%, the proportion of styrene block in the molecular chain of SEBS is insufficient to provide rigidity, resulting in a significant decrease in the tensile strength of the TPE material, and the mechanical properties cannot meet the requirements. When the content of styrene is higher than 40%, the rigidity of the molecular chain is too strong, the elongation at break of the material decreases, and at the same time, the melt viscosity of SEBS is too high, the flowability is poor, the processing performance is poor (such as injection filling difficulty), which is not conducive to the encapsulation, and affects the comprehensive performance of the final product.

[0125] The specific embodiments described herein are merely illustrative of the spirit of the present application. Those skilled in the art of the present application can make various modifications or supplements to the described specific embodiments or replace them with similar ways without deviating from the spirit of the present application or exceeding the scope defined by the appended claims.

Claims

1. A PBT encapsulating material resistant to moisture and heat aging, characterized in that: The PBT encapsulation material resistant to moisture and heat aging comprises the following raw materials: Thermoplastic polyester elastomer: 25-60 parts; Epoxy modified polysiloxane resin: 2-10 parts; SEBS: 10-30 parts; White oil: 10-30 parts; Cyclic polyester oligomer: 0.5-3 parts; Compatibilizer: 4-10 parts; Inorganic filler: 0-20 parts; Antioxidant: 0.1-2 parts; Anti-hydrolysis agent: 0.1-2 parts; The epoxy-modified polysiloxane resin is one or more of a polysiloxane resin containing epoxy groups on the main chain, a polysiloxane resin containing epoxy groups on the side chain, and a polysiloxane resin containing epoxy groups on both the main chain and the side chain; The epoxy-modified polysiloxane resin contains organic silicon segments.

2. The PBT encapsulating material resistant to moisture and heat aging according to claim 1, characterized in that: The epoxy-modified polysiloxane resin has a molecular weight of 400-8000 g / mol and an epoxy equivalent weight of 100-4000 g / eq.

3. The PBT encapsulating material resistant to moisture and heat aging according to claim 1, characterized in that: The number average molecular weight of the SEBS is 100,000-250,000, and the styrene content is 25 wt%-40 wt%.

4. The PBT encapsulating material resistant to moisture and heat aging according to claim 1, characterized in that: The thermoplastic polyester elastomer is one or more of polyester-type polyester elastomer and polyether-type polyester elastomer, and has a hardness range of 20-50D.

5. The PBT encapsulating material resistant to moisture and heat aging according to claim 4, characterized in that: The hard segment of the thermoplastic polyester elastomer is PBT, the soft segment is polyether, the hardness range is 25-40D, and the melting point is less than 190°C.

6. The PBT encapsulating material resistant to moisture and heat aging according to claim 1, characterized in that: The cyclic polyester oligomer is cyclic butylene terephthalate, and the molecular formula is (C 12 H 12 O4) n , where n=2-6.

7. The PBT encapsulating material resistant to moisture and heat aging according to claim 1, characterized in that: The anti-hydrolysis agent is one or more of monomeric carbodiimide, polymeric carbodiimide, and liquid carbodiimide.

8. The PBT encapsulating material resistant to moisture and heat aging according to claim 1, characterized in that: The compatibilizer is one or more of maleic anhydride grafted PP, maleic anhydride grafted PE, maleic anhydride grafted POE, maleic anhydride grafted SEBS, and maleic anhydride grafted EPDM; And / or, the flash point of the white oil is ≥200°C, the temperature is ≤40°C and the kinematic viscosity is 10-100mm 2 / s between; And / or, the inorganic filler is one or more of calcium carbonate, talc, wollastonite, kaolin, mica, diatomaceous earth, carbon black, and silicon dioxide; And / or, the antioxidant is one or more of hindered phenol antioxidants, phosphite antioxidants, thio antioxidants and hindered amine antioxidants.

9. A method for preparing the PBT encapsulating material resistant to moisture and heat aging according to any one of claims 1 to 8, characterized in that: The following steps are involved: a) Weighing each component according to the weight ratio, adding SEBS and white oil into a high-speed blender until the SEBS particles are completely swollen and no free white oil is visible, forming a pre-swollen SEBS matrix; b) adding a thermoplastic polyester elastomer, an epoxy-modified polysiloxane resin, a cyclic polyester oligomer, a compatibilizer, an inorganic filler, an antioxidant, and an anti-hydrolysis agent to the pre-swollen SEBS matrix obtained in step a) in sequence, and continuing to stir until a homogeneous premix is ​​formed with no visible agglomerates; c) adding the homogeneous premix obtained in step b) into a twin-screw extruder, subjecting the mixture to shearing, melt plasticization, extrusion granulation, and homogenization to obtain a PBT encapsulating material resistant to moisture and heat aging.

10. The preparation method according to claim 9, characterized in that: In step a), the stirring speed is 200-500 r / min; And / or, in step c), the screw speed is 300-500 r / min, and the processing temperature in each zone is 180-230°C.

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