Low-thin-consistency filler type high-temperature-resistant hot-melt pressure-sensitive adhesive and preparation method thereof

Abstract

The invention is applied to the technical field of high polymer materials, and discloses a low-thin-consistency filler type high-temperature-resistant hot-melt pressure-sensitive adhesive which comprises the following components in parts by weight: 30-50 parts of SBC rubber which is a high-melt-index elastomer and has the styrene content of 25-40%; 10-20 parts of an inorganic filler which is a compound of nano-scale fumed silica and heavy calcium carbonate; 20-40 parts of tackifying resin, which is a compound of highly hydrogenated C5 petroleum resin and high softening point monomer resin; 5-15 parts of a softening agent which is naphthenic oil; and 0.5-2 parts of an antioxidant which is a compound of hindered phenol and phosphite ester. According to the low-thin-consistency filler type high-temperature-resistant hot-melt pressure-sensitive adhesive, a rigid core-flexible shell structure is formed through an in-situ grafting reaction of the nanoscale fumed silica and the main polymer, a protective framework can be formed in a high-temperature environment, and the cohesive strength is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive and its preparation method. Background Technology

[0002] Currently, most hot melt pressure-sensitive adhesives used in linear speed tapes on the market are mainly composed of styrene block copolymers, combined with tackifying resins, white mineral oil and other raw materials. However, these hot melt pressure-sensitive adhesives have significant limitations in high-temperature environments, such as inside electronic devices and around automobile engines where the temperature often exceeds 80°C: they are prone to softening and decreased cohesive strength, resulting in a sharp decrease in holding power, which in turn leads to problems such as decreased adhesion, flow and delamination, causing the core functions of the tape, such as fixing and sealing, to fail, seriously affecting the normal use and stability of the product; To improve high-temperature resistance, existing technologies often employ methods such as adjusting the formulation ratio or adding conventional inorganic fillers. However, these approaches often introduce new technical problems: On the one hand, conventional inorganic fillers tend to agglomerate in the system due to the difference between their surface polarity and that of the non-polar polymer matrix, leading to a significant increase in adhesive viscosity and severely affecting the coating process. On the other hand, while high filler content (>20%) can improve temperature resistance to some extent, it can impair the mobility of polymer chains, resulting in decreased adhesive flexibility and even brittle fracture. Furthermore, other high-temperature modification schemes (such as introducing acrylates, epoxy resins, etc.) are often accompanied by problems such as loss of initial tack or increased process complexity, making it difficult to balance high-temperature stability, low viscosity, and excellent flexibility. Therefore, developing a hot melt pressure-sensitive adhesive that can maintain stable performance under high temperature conditions (≥150℃) while possessing low melt viscosity (≤50000cPS) and good flexibility has become the key to solving the pain points of existing technologies. Summary of the Invention

[0003] The purpose of this invention is to provide a low-viscosity filler-type high-temperature resistant hot melt pressure-sensitive adhesive and its preparation method, so as to solve the problems mentioned in the background art that the existing hot melt pressure-sensitive adhesives have insufficient performance in high-temperature environments and that existing improvement schemes are difficult to balance high-temperature stability, low melt viscosity and excellent flexibility.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive, comprising the following components in parts by weight: SBC rubber: 30-50 parts, wherein the SBC rubber is a high melt index elastomer with a styrene content of 25-40%; Inorganic filler: 10-20 parts, a compound of nano-sized fumed silica and heavy calcium carbonate; Tackifying resin: 20-40 parts, a complex of highly hydrogenated C5 petroleum resin and high softening point monomer resin; Softener: 5-15 parts, naphthenic oil; Antioxidant: 0.5-2 parts, a compound of hindered phenol and phosphite.

[0005] Preferably, the nanoscale fumed silica has a particle size of 20-50 nm and is pretreated with silane coupling agent KH-550, with amino functional groups grafted onto its surface.

[0006] Using the above technical solution, after nano-sized fumed silica is pretreated with silane coupling agent KH-550, the amino functional groups grafted on the surface can undergo an in-situ grafting reaction with the butadiene double bonds of SBC to form a "rigid core-flexible shell" structure. This effectively improves the compatibility between the filler and the polymer matrix, reduces filler agglomeration, enhances the high-temperature stability of the system, and retains the mobility of polymer chain segments through the flexible shell, avoiding the viscosity surge problem caused by poor compatibility.

[0007] Preferably, the amount of nano-sized fumed silica added in the inorganic filler is 5-15 wt%.

[0008] Using the above technical solution, the addition of 5-15wt% nano-sized fumed silica can precisely reduce the polymer chain entanglement density through the steric hindrance effect, effectively reducing the melt zero-shear viscosity to ≤50000cPS (180℃). At the same time, this addition amount can ensure that the filler forms a continuous reinforcing framework in the system, providing sufficient cohesive strength at high temperatures. This avoids the problems of insufficient temperature resistance due to too low an addition amount or a sudden increase in viscosity and decrease in flexibility due to too high an addition amount, thus achieving a balance between low viscosity and high temperature resistance.

[0009] Preferably, the hot melt pressure-sensitive adhesive has the following properties: melt viscosity at 180°C ≤50000CPS, peel strength from steel plate at 180° ≥2.5N / cm, and back adhesion to substrate at 180° ≥2.5N / cm. It exhibits no warping, cracking, or adhesive overflow under ambient temperature (23°C for 72h), short-term heat aging at 125°C for 240h, and overload heat aging at 150°C for 6h.

[0010] Using the above technical solution, the melt viscosity at 180℃ is ≤50000CPS, ensuring that the hot melt pressure-sensitive adhesive has good coating processability and meets the needs of industrial production. The peel force of 180° steel plate and the back adhesion of the substrate are ≥2.5N / cm, ensuring excellent adhesion to different substrates. The absence of lifting, cracking, and overflow under both room temperature and high temperature aging conditions proves that it can stably perform its fixing and sealing functions in both room temperature and high temperature (≥150℃) environments. This solves the problem of performance failure of traditional hot melt pressure-sensitive adhesives at high temperatures and is suitable for high-temperature and high-reliability scenarios such as new energy vehicle battery pack packaging and engine compartment wiring harness bundling.

[0011] Preferably, the hot melt pressure-sensitive adhesive further includes other additives, which are one or more of the following: UV-resistant additives, high-temperature yellowing-resistant additives, fluorescent-shielding additives, or additives that maintain tackiness under high humidity conditions.

[0012] By adopting the above technical solutions, UV-resistant additives and high-temperature yellowing-resistant additives can specifically improve the stability of products under UV irradiation, high-temperature aging and other environments, while fluorescent shielding additives meet the optical requirements of specific scenarios, and high-humidity tack-maintaining additives ensure the ability to maintain tack in humid environments. This expands the applicable environment range of hot melt pressure-sensitive adhesives and enhances their reliability under complex working conditions.

[0013] A method for preparing a low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive, the method comprising the following steps: Step 1: Raw material preparation: Accurately weigh each component according to its weight percentage; Step 2, Mixing and Melting: Add the inorganic filler, SBC, and softener to the reactor, heat to 150-180℃, and fully melt and mix them under stirring conditions. The stirring speed is 100-300 r / min, and the stirring time is 30-60 minutes. Step 3: Add tackifying resin and antioxidant: After the inorganic filler, SBC and softener are mixed evenly, lower the temperature to 120-140℃, add tackifying resin and antioxidant, and continue stirring for 30-60 minutes to ensure that all components are fully mixed. Step 4, Discharge: After stirring, filter the hot melt pressure-sensitive adhesive in the reactor through a filter screen to remove impurities, and then discharge the material to obtain the high-temperature resistant hot melt pressure-sensitive adhesive.

[0014] Preferably, the mixing and melting process in step two employs a two-stage mixing process: Primary dispersion: SBC and naphthenic oil were melt-blended at 160°C with a stirring speed of 300 r / min for 40 min to form a pre-crosslinked network; High-speed shearing: Stir at 1000 r / min for 20 min to force dispersion of nanofillers.

[0015] Using the above technical solution, a pre-crosslinked network is formed at 160℃ in the primary dispersion stage, providing basic structural support for the system. High-speed shearing (1000r / min×20min) can forcibly disperse the nanofiller, breaking the secondary agglomeration caused by van der Waals forces and ensuring uniform distribution of the filler. The synergistic effect of the two-stage mixing not only avoids the uneven dispersion of filler caused by single low-speed stirring (which can easily lead to excessively high local viscosity), but also prevents the direct high-speed shearing from destroying the pre-crosslinked structure, thus ensuring the uniformity and stability of the system performance.

[0016] Preferably, after adding the tackifying resin and antioxidant in step three, the resin is cured at a low temperature of 130°C. The low glass transition temperature (Tg≈-30°C) of the resin promotes interfacial wetting and forms a "gradient crosslinking" structure.

[0017] By adopting the above technical solution, the low-temperature curing at 130℃ combined with the low glass transition temperature (Tg≈-30℃) of the tackifying resin can promote the interfacial wetting of the tackifying resin, antioxidant and pre-crosslinking system, forming a "gradient crosslinking" structure. The outer layer has a lower crosslinking density to retain tackiness and flexibility, while the inner layer has a higher crosslinking density to provide cohesive strength at high temperatures. This structure avoids resin volatilization or excessive crosslinking (which can easily lead to brittleness) caused by high-temperature curing, and also solves the problem of uneven performance caused by insufficient interfacial wetting at low temperatures, thus taking into account tackiness, flexibility and high-temperature stability.

[0018] Compared with the prior art, the beneficial effects of the present invention are: the low-viscosity filler-type high-temperature resistant hot melt pressure-sensitive adhesive: 1. Excellent high-temperature stability: Through the in-situ grafting reaction of nano-scale fumed silica with the main polymer, a "rigid core-flexible shell" structure is formed, which can form a protective framework under high temperature environment, significantly improving cohesive strength. Under short-term heat aging at 125℃ (240h) and overload heat aging at 150℃ (6h), there is no warping, cracking or glue overflow. This solves the problems of traditional hot melt pressure sensitive adhesives being easy to soften, have a sudden decrease in holding power and fail to function at high temperature. It can be stably applied to high-temperature scenarios such as new energy vehicle battery pack packaging and engine compartment wiring harness bundling. 2. Low viscosity and good flowability: By controlling the amount of nano-sized fumed silica added (5-15wt%), its steric hindrance effect is used to reduce the polymer chain entanglement density, effectively reducing the melt viscosity. The melt viscosity of the product of this invention at 180℃ is as low as 45000cPS, which is far lower than the traditional solution and meets the process requirement of ≤50000cPS, ensuring convenient coating process and adapting to industrial production. 3. Excellent balance between flexibility and adhesion: The “gradient cross-linking” structural design avoids the problem of reduced polymer chain mobility caused by the addition of traditional high fillers, and balances high temperature resistance and flexibility. At the same time, the composite tackifying system of high hydrogenated C5 petroleum resin and high softening point monomer resin, combined with the softening effect of naphthenic oil, ensures excellent adhesion of the product to steel plates and substrates, and solves the contradiction of adhesion loss or reduced flexibility in existing modification schemes. 4. Simplified preparation process: Through dynamic thermal crosslinking process, performance optimization can be achieved without the introduction of complex exogenous crosslinking agents. Compared with existing modification schemes that require the introduction of acrylates, epoxy resins, etc., the process is simpler, lower in cost, and suitable for large-scale production. 5. Excellent overall performance and environmental adaptability: The compounded hindered phenol and phosphite antioxidants can effectively resist high-temperature yellowing and oxidative aging. Optional additives such as UV protection, fluorescence shielding, and high-humidity adhesion retention further enhance the product's stability in complex environments and broaden its application scenarios. Detailed Implementation

[0019] 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.

[0020] This invention provides a technical solution: a low-viscosity filler-type high-temperature resistant hot melt pressure-sensitive adhesive, comprising the following components in parts by weight: SBC rubber: 30-50 parts. SBC rubber is a high melt index elastomer with a styrene content of 25-40%. Inorganic filler: 10-20 parts, a compound of nano-sized fumed silica and heavy calcium carbonate; Tackifying resin: 20-40 parts, a complex of highly hydrogenated C5 petroleum resin and high softening point monomer resin; Softener: 5-15 parts, naphthenic oil; Antioxidant: 0.5-2 parts, a compound of hindered phenol and phosphite.

[0021] Example 1: Preferred Formula 1. Formula composition (parts by weight) SIS (35% styrene content): 40 parts Inorganic filler (a mixture of heavy calcium carbonate and nano-sized fumed silica, wherein the fumed silica particles are 20-50 nm in size and pretreated with silane coupling agent KH-550): 15 parts Hydrogenated C5 petroleum resin: 25 parts High softening point monomer resin: 10 parts Naphthenic oil (model KN4010): 10 parts Antioxidant (1010 and 168 mixed in a 1:1 ratio): 0.3 parts 2. Preparation method Step 1: Accurately weigh each raw material according to the above weight proportions; Step 2: Mixing and melting: Add inorganic filler, SIS, and naphthenic oil to the reactor, heat to 160℃, stir at 300r / min for 40min (primary dispersion to form a pre-crosslinked network), and then shear at 1000r / min for 20min (forced dispersion of nanofiller to avoid secondary agglomeration). Step 3: Cool down to 130℃, add hydrogenated C5 petroleum resin, high softening point monomer resin and antioxidant, stir for 45 minutes (low temperature curing, utilizing the low Tg of the resin to promote interface wetting and form a "gradient crosslinking" structure). Step 4: After filtering through a filter screen, the material is discharged to obtain a low-viscosity filler-type high-temperature resistant hot melt pressure-sensitive adhesive.

[0022] 3. Performance Test Results Melt viscosity at 180℃ (HG / T3660-1999): 45000 cPS (≤50000 cPS, meeting the requirements for low viscosity). 180° steel plate peel force (LV312-1): 3.9 N / cm (≥2.5 N / cm); 180° substrate backing adhesion: 4.1 N / cm (≥2.5 N / cm); Room temperature wrapping (23℃ for 72 hours): No warping, no cracking, no excess adhesive; Short-term heat aging (125℃ for 240h): No warping, no cracking, no glue overflow; Overload heat aging (150℃ for 6 hours): No warping, no cracking, no glue overflow.

[0023] Comparative Example 2: Traditional Solution 1 1. Formula composition (parts by weight) SIS: 25 copies SBS: 15 copies Inorganic filler (heavy calcium carbonate, without surface modification): 15 parts C5 / C9 copolymer resin: 15 parts Hydrogenated DCPD petroleum resin: 15 parts Naphthenic oil (model KN4010): 10 parts Antioxidant (1010 and 168 mixed in a 1:1 ratio): 0.3 parts 2. Preparation method Step 1: Accurately weigh each raw material according to the above weight proportions; Step 2: Mixing and melting: Add inorganic filler, SIS, SBS, and naphthenic oil to the reactor, heat to 170℃, and stir at 200r / min for 50min; Step 3: Cool down to 130℃, add C5 / C9 copolymer resin, hydrogenated DCPD petroleum resin and antioxidant, and stir for 50 minutes; Step 4: After filtering through a filter screen, the material is discharged to obtain the traditional hot melt pressure-sensitive adhesive.

[0024] 3. Performance Test Results Melt viscosity at 180℃ (HG / T3660-1999): 80000 cPS (far exceeding 50000 cPS, indicating excessively high viscosity); 180° steel plate peel force (LV312-1): 3.2 N / cm (≥2.5 N / cm); 180° substrate backing adhesion: 3.7 N / cm (≥2.5 N / cm); Room temperature wrapping (23℃ for 72 hours): No warping, no cracking, no excess adhesive; Short-term heat aging (125℃ 240h): warping, glue overflow, no brittleness; Overload heat aging (150℃ for 6 hours): warping, glue overflow, brittle cracking.

[0025] Comparative Example 3: Traditional Option 2 1. Formula composition (parts by weight) SBR (35% styrene content): 15 parts SBS (Model YH-791): 15 copies SIS: 20 copies Inorganic filler (heavy calcium carbonate, without surface modification): 15 parts C5 / C9 copolymer resin: 25 parts Modified epoxy resin: 15 parts Naphthenic oil (model KN4010): 10 parts Antioxidant (1010 and 168 mixed in a 1:1 ratio): 0.3 parts 2. Preparation method Step 1: Accurately weigh each raw material according to the above weight proportions; Step 2: Mixing and melting: Add inorganic filler, SBR, SBS, SIS, and naphthenic oil to the reactor, heat to 180℃, and stir at 250r / min for 60min; Step 3: Cool down to 140℃, add C5 / C9 copolymer resin, modified epoxy resin and antioxidant, and stir for 60 minutes; Step 4: After filtering through a filter screen, the material is discharged to obtain the traditional modified hot melt pressure-sensitive adhesive.

[0026] 3. Performance Test Results Melt viscosity at 180℃ (HG / T3660-1999): 120,000 cPS (significantly exceeds 50,000 cPS, indicating excessively high viscosity). 180° steel plate peel force (LV312-1): 4.3 N / cm (≥2.5 N / cm); 180° substrate backing adhesion: 4.8 N / cm (≥2.5 N / cm); Room temperature wrapping (23℃ for 72 hours): No warping, no cracking, no excess adhesive; Short-term heat aging (125℃ 240h): slight warping, slight glue overflow, no brittleness; Overload heat aging (150℃ for 6 hours): warping, glue overflow, brittle cracking.

[0027] The above specific embodiments further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are merely specific embodiments of the present invention and do not limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive, characterized in that: The components include the following parts by weight: SBC rubber: 30-50 parts, wherein the SBC rubber is a high melt index elastomer with a styrene content of 25-40%; Inorganic filler: 10-20 parts, a compound of nano-sized fumed silica and heavy calcium carbonate; Tackifying resin: 20-40 parts, a complex of highly hydrogenated C5 petroleum resin and high softening point monomer resin; Softener: 5-15 parts, naphthenic oil; Antioxidant: 0.5-2 parts, a compound of hindered phenol and phosphite.

2. The low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive according to claim 1, characterized in that: The nanoscale fumed silica has a particle size of 20-50 nm and is pretreated with silane coupling agent KH-550, with amino functional groups grafted onto its surface.

3. The low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive according to claim 1, characterized in that: The amount of nano-sized fumed silica added in the inorganic filler is 5-15 wt%.

4. The low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive according to claim 1, characterized in that: This hot melt pressure-sensitive adhesive has a melt viscosity of ≤50000 CPS at 180℃, a peel strength of ≥2.5 N / cm from a steel plate at 180°, and a back adhesion strength of ≥2.5 N / cm from a substrate at 180°. It exhibits no curling, cracking, or excess adhesive under normal temperature winding (23℃ for 72 hours), short-term heat aging at 125℃ for 240 hours, and overload heat aging at 150℃ for 6 hours.

5. The low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive according to claim 1, characterized in that: The hot melt pressure-sensitive adhesive also includes other additives, which are one or more of the following: UV-resistant additives, high-temperature yellowing-resistant additives, fluorescent-shielding additives, or additives that maintain tackiness under high humidity conditions.

6. A method for preparing a low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive according to any one of claims 1-5, characterized in that: The preparation method includes the following steps: Step 1: Raw material preparation: Accurately weigh each component according to its weight percentage; Step 2, Mixing and Melting: Add the inorganic filler, SBC, and softener to the reactor, heat to 150-180℃, and fully melt and mix them under stirring conditions. The stirring speed is 100-300 r / min, and the stirring time is 30-60 minutes. Step 3: Add tackifying resin and antioxidant: After the inorganic filler, SBC and softener are mixed evenly, lower the temperature to 120-140℃, add tackifying resin and antioxidant, and continue stirring for 30-60 minutes to ensure that all components are fully mixed. Step 4, Discharge: After stirring, filter the hot melt pressure-sensitive adhesive in the reactor through a filter screen to remove impurities, and then discharge the material to obtain the high-temperature resistant hot melt pressure-sensitive adhesive.

7. The preparation method of a low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive according to claim 6, characterized in that: The mixing and melting process in step two employs a two-stage mixing process: Primary dispersion: SBC and naphthenic oil were melt-blended at 160°C with a stirring speed of 300 r / min for 40 min to form a pre-crosslinked network; High-speed shearing: Stir at 1000 r / min for 20 min to force dispersion of nanofillers.

8. The method for preparing a low-viscosity filler-type high-temperature resistant hot-melt pressure-sensitive adhesive according to claim 6, characterized in that: In step three, after adding tackifying resin and antioxidant, the mixture is cured at a low temperature of 130°C. The low glass transition temperature of the resin (Tg≈-30°C) promotes interfacial wetting and forms a "gradient crosslinking" structure.