Low-temperature instant cross-linking rubber type cold-resistant polyethylene protective film and preparation method thereof

Abstract

This invention discloses a low-temperature instant crosslinking rubber-type cold-resistant polyethylene protective film and its preparation method, belonging to the field of protective film technology. The protective film is prepared by coating a polyethylene base film with a two-component rubber pressure-sensitive adhesive and then crosslinking it at low temperature. Component A is a ternary compound rubber phase, and component B is an aliphatic triisocyanate crosslinking phase, combined with synergistic additives to achieve rapid low-temperature catalytic crosslinking. The preparation process employs a two-component synchronous delivery, static mixing, slot coating, and low-temperature curing at 70-90℃, completing crosslinking in 3-5 minutes, significantly reducing energy consumption. The resulting protective film exhibits excellent initial tack and holding power, shows no brittleness or residue at -30℃, has a gel content of over 91%, and demonstrates excellent low-temperature protective performance. This invention's process is safe, efficient, and suitable for industrial production, meeting the requirements for product surface protection in low-temperature environments.

Description

Technical Field

[0001] This invention relates to the field of protective film preparation technology, specifically to a low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film and its preparation method. Background Technology

[0002] In modern industrial production and daily life, protective films, as key materials for surface protection, are widely used in the entire process of production, transportation, storage and use of various products such as electronic components, metal sheets, architectural glass and plastic parts. Their core function is to resist external damage such as scratches, wear, corrosion and pollution, and to ensure the integrity of the product surface and the stability of its performance.

[0003] Rubber-type polyethylene protective film is a polymer film prepared by extrusion molding of polyethylene plastic masterbatch, followed by coating with rubber-type pressure-sensitive adhesive, drying, winding, and cutting. It possesses excellent flexibility, high elasticity, and weather resistance, while also exhibiting good peelability and temperature resistance, demonstrating irreplaceable application value in high-precision product protection and extreme environment applications. Pressure-sensitive adhesive (PSA) is the core functional layer of the protective film. Rubber-type PSA, in particular, has significant application value in the protective film field due to its excellent initial adhesion, good wettability to low surface energy substrates, and relatively low cost. Currently, most mainstream rubber-type polyethylene protective film products on the market use single-component adhesive systems in their formulation design and rely on high-temperature crosslinking agents (such as dicumyl peroxide, DCP) to achieve crosslinking of the materials, thereby ensuring the adhesive performance and stability of the protective film.

[0004] However, the existing single-component high-temperature crosslinking scheme has many inherent defects, specifically: First, the crosslinking reaction can only be initiated under high temperature conditions, resulting in high energy consumption during the production process and significantly increasing the production cost for enterprises; Second, high-temperature crosslinking agents are mostly free radical initiators with poor storage stability, and are prone to decomposition during room temperature storage, which not only affects the performance of adhesives but may also cause safety hazards; Third, the decomposition of high-temperature crosslinking agents easily produces a large number of volatile byproducts, which not only pollute the environment but also increase the risk of flammability and explosion in the production environment, reducing the safety of the production process; Fourth, the high-temperature crosslinking process adversely affects the flexibility, transparency, and other properties of polyethylene substrates and rubber adhesives, causing the prepared protective film to be brittle and cracked at low temperatures, failing to meet the usage requirements of cold regions or low-temperature working conditions.

[0005] To address the aforementioned technical challenges, the industry urgently needs to develop an innovative preparation technology that integrates processing safety, efficient crosslinking, and coating processes. In existing technologies, some isocyanate crosslinking agents possess low-temperature reaction capabilities, but they are primarily used in structural adhesives or spray coatings, and have not yet been applied to the crosslinking system of rubber-based polyethylene protective films. Therefore, this invention proposes a solution combining static mixing of two-component adhesive solutions with low-temperature instant crosslinking technology, aiming to overcome existing technological bottlenecks and prepare a high-performance, safe, and energy-efficient rubber-based cold-resistant polyethylene protective film. Summary of the Invention

[0006] The purpose of this invention is to provide a low-temperature instant crosslinking rubber-type cold-resistant polyethylene protective film. This protective film is formed by low-temperature instant crosslinking of a two-component rubber pressure-sensitive adhesive. The crosslinking conditions are mild and the production energy consumption is low. At the same time, it has excellent cold resistance, adhesion stability and peelability, which can meet the long-term use requirements in low-temperature environments.

[0007] Another objective of this invention is to provide a method for preparing the above-mentioned low-temperature instant crosslinking rubber-type cold-resistant polyethylene protective film. This method employs a two-component adhesive solution static synchronous mixing and low-temperature instant crosslinking process, which eliminates the need for high-temperature initiation of crosslinking. It is simple to operate, has high production efficiency, is safe and environmentally friendly, and is suitable for industrial continuous production.

[0008] To achieve the above objectives, the present invention adopts the following technical solution: A low-temperature instant crosslinking rubber-type cold-resistant polyethylene protective film is prepared by coating a two-component rubber pressure-sensitive adhesive onto the surface of a polyethylene base film. The two-component rubber pressure-sensitive adhesive consists of component A and component B, wherein: component A is a non-polar rubber phase, comprising, by weight: 7-15 parts of rubber mixture, 1-5 parts of terpene resin, 1-10 parts of petroleum resin, 0.1-1 parts of antioxidant, 0.3-1 parts of additives, 0.05-0.5 parts of ultraviolet absorber, and 50-90 parts of gasoline; the additives are composed of tetrahydroxyethyl ethylenediamine and modified attapulgite in a mass ratio of 1:(5-15); the rubber mixture consists of vulcanized natural rubber, natural rubber, and maleic anhydride-modified natural rubber; component B is a polar crosslinking phase, comprising, by weight: 10-30 parts of aliphatic triisocyanate, 5-20 parts of 4-hydroxybutyl acrylate, 0.01-0.3 parts of dibutyltin dilaurate, and 30-60 parts of toluene.

[0009] Furthermore, the mass ratio of component A to component B is (8-10):1.

[0010] Furthermore, the Mooney viscosity ML(1+4) of the natural rubber in component A is 60~80 at 100°C, and the Mooney viscosity ML(1+4) of the vulcanized natural rubber is 50~70 at 100°C.

[0011] Furthermore, the aliphatic triisocyanate in component B is a hexamethylene diisocyanate trimer (HDI trimer).

[0012] Furthermore, the weight ratio of vulcanized natural rubber, natural rubber and maleic anhydride modified natural rubber in the rubber mixture is 1:2:(1.5-2).

[0013] Furthermore, the maleic anhydride-modified natural rubber has a maleic anhydride grafting rate of 0.5% to 2.0%, and is prepared by a method comprising the following steps: (i) adding 100 parts by weight of natural rubber, 5-8 parts by weight of maleic anhydride, and 0.3-0.6 parts by weight of dicumyl peroxide into a two-roll mill, with the roller temperature controlled at 150-160°C; (ii) mixing and reacting for 10-15 minutes; (iii) passing the mixture through a thin sheet, cooling, and pelletizing to obtain the final product.

[0014] Furthermore, the modified attapulgite is prepared using the following method: (1) After activating the attapulgite with 1 mol / L dilute HCl, it was reacted with KH792 silane coupling agent in toluene at 80℃ for 10-12 h to obtain KH792 modified attapulgite. (2) Disperse KH792 modified attapulgite in dichloromethane at a solid-liquid ratio of 1g:20mL to form a uniform dispersion; (3) Dissolve azodicyanovalerate in dichloromethane at a ratio of 1g:10mL, then add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N,N-dimethylaminopyridine, and stir at room temperature for 1-2h to obtain an activated mixture. (4) Mix the dispersion obtained in step (2) and the activated mixture obtained in step (3) at a volume ratio of 2:1, react at room temperature for 24-36 hours, centrifuge to separate the solid product after the reaction, wash repeatedly with deionized water and anhydrous ethanol several times, and vacuum dry at room temperature to constant weight to obtain the product.

[0015] Furthermore, in step (1), the ratio of activated attapulgite, KH792 silane coupling agent, and toluene is 10g:15g:100mL.

[0016] Further, in step (3), the mass ratio of azobiscyanopentanoic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N,N-dimethylaminopyridine is 10:8:(0.8-1).

[0017] The present invention also provides a method for preparing the above-mentioned low-temperature instant crosslinked rubber-type cold-resistant polyethylene protective film, comprising the following steps: (1) Add the crushed vulcanized natural rubber, natural rubber, and maleic anhydride modified natural rubber to the open mill in proportion. Set the open mill temperature to 30-50℃, the roller gap to 0.5-1mm, and the plasticizing time to 15-25min until the rubber is completely softened and a uniform rubber mixture is formed. Finally, put the plasticized rubber mixture into the reactor that has been pre-added with solvent gasoline, keep the temperature at 30-40℃, stir for 1-2h to make the rubber completely dissolved, and then add terpene resin, petroleum resin, antioxidant, additives, and ultraviolet absorber to the reactor in sequence, keep the temperature at 30-40℃, stir fully for 24h to obtain component A. (2) Add toluene into a stirring vessel and control the stirring speed to 100-150 r / min. Add aliphatic triisocyanate, 4-hydroxybutyl acrylate and dibutyltin dilaurate in sequence. Maintain the stirring temperature at 20-25℃ and the stirring time at 30-60 min to ensure that all components are completely dissolved and uniformly mixed to obtain component B. (3) Use dual metering pumps to synchronously transport component A and component B, control the mass ratio of component A to component B to be 10:1-8:1, stabilize the output pressure of the dual pumps at 0.3-0.5MPa, and synchronously transport component A and component B to the static mixer. The residence time of the material in the static mixer is 5-10s, so as to realize the instantaneous and uniform mixing of the two-component adhesive liquid. The mixed adhesive liquid is directly fed into the slit coating head. The coating gap of the coating head is 50-100μm, the coating speed is 1-3m / min, and a uniform adhesive film layer is formed on the surface of the polyethylene substrate. (4) The polyethylene substrate coated with adhesive film is sent into a hot air drying oven. The oven temperature is set to 70℃-90℃, the temperature deviation is controlled within ±2℃, the hot air speed is 1-2m / s, and the adhesive film stays in the oven for 3-5 minutes. Under these conditions, the low-temperature instant cross-linking reaction is completed, and then the finished product is obtained by winding.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The rubber mixture in component A of this invention is a ternary compound of vulcanized natural rubber, natural rubber and maleic anhydride modified natural rubber. Among them, vulcanized natural rubber provides a moderate pre-crosslinking network, which enhances the cohesive strength and creep resistance of the film; unvulcanized natural rubber imparts good initial tack and wettability; while maleic anhydride modified natural rubber acts as a bridging component, and its anhydride groups can undergo nucleophilic addition reactions with aliphatic triisocyanates in component B, forming crosslinking points at room temperature. The three components are compounded in a specific ratio, which not only ensures the pressure-sensitive adhesion performance in the initial stage of coating, but also provides sufficient active sites for subsequent low-temperature crosslinking, avoiding excessive degradation or embrittlement of the rubber molecular chains by high-temperature crosslinking.

[0019] (2) The additive of the present invention is composed of tetrahydroxyethyl ethylenediamine and modified attapulgite in a mass ratio of 1:(5-15). Tetrahydroxyethyl ethylenediamine, as a polyhydroxy tertiary amine compound, can react with the isocyanate groups in component B and participate in the construction of crosslinking network, thus accelerating the low-temperature curing process. On the other hand, its tertiary amine structure can catalyze the reaction of isocyanate with hydroxyl, carboxyl and anhydride groups, and act as a low-temperature latent curing agent, so that the crosslinking reaction can be completed within 3-5 minutes under the oven conditions of 70-90℃, which is much lower than the temperature of more than 120℃ required for traditional high-temperature crosslinking. There are hydrogen bonds and electrostatic interactions between modified attapulgite and tetrahydroxyethyl ethylenediamine. When the two are added together, they play a key role in synergy. The overall dispersion of the additive in the rubber matrix is ​​greatly improved, and it can synergistically promote the migration and reaction of isocyanate crosslinking agent to the surface of rubber phase, so as to achieve low-temperature, fast and uniform crosslinking effect.

[0020] (3) This invention employs a two-component system. The aliphatic triisocyanate in component B, under the catalysis of dibutyltin dilaurate, can undergo a low-temperature addition reaction with the anhydride groups of maleic anhydride-modified natural rubber, the hydroxyl groups of tetrahydroxyethyl ethylenediamine, and the carboxyl groups on the surface of modified attapulgite in component A. Because component A contains abundant active hydrogen groups (hydroxyl, carboxyl, and amine groups), and the tertiary amine in the additives further catalyzes the reaction, the crosslinking reaction can reach the ideal crosslinking density within 3-5 minutes under mild conditions of 70-90℃. Compared with the prior art, the crosslinking temperature of this invention is reduced by 30-50℃, and the oven dwell time is shortened by more than 40%, significantly reducing production energy consumption while avoiding damage to the polyethylene substrate and rubber elasticity caused by high temperatures.

[0021] (4) This invention employs an integrated process of simultaneous delivery by dual metering pumps, static mixing, and slot coating. Component A and component B are uniformly mixed after 5-10 seconds in a static mixer. The mixture is then directly coated, avoiding the risk of gelation within the reactor caused by premixing. After coating, the film is dried with hot air at 70-90℃, allowing the solvent to evaporate and cross-link to solidify simultaneously. The process is continuous and compact, suitable for large-scale industrial production. The low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film prepared by this invention exhibits excellent low-temperature cold resistance, instant adhesion, tackiness, and anti-residue properties, demonstrating good industrial practical value. Detailed Implementation

[0022] The technical solution of the present invention will be further described below with reference to specific embodiments, but is not limited thereto. Unless otherwise specified, all raw materials used in the present invention are commercially available, and some of the raw materials are sourced from the following sources: vulcanized natural rubber (Hainan Rubber, SCR 20), natural rubber (Hainan Rubber, SCR WF), terpene resin (Yoshida Chemical, T-80L; Hubei Songtai, H-T120), petroleum resin (Yoshida Chemical, C5-90, HC5-110), antioxidant (Tianjin Lianlong, RIANOX® 1010), and ultraviolet absorber (Tianjin Lianlong, any one of RIASORB® UV-326, UV-327, UV-328, and UV-329).

[0023] Example 1 A low-temperature instant crosslinking rubber-type cold-resistant polyethylene protective film is prepared by coating a two-component rubber pressure-sensitive adhesive onto the surface of a polyethylene base film. The two-component rubber pressure-sensitive adhesive consists of component A and component B, wherein: component A is a non-polar rubber phase, comprising by weight: 7 parts of rubber mixture, 1 part of terpene resin, 1 part of petroleum resin, 0.1 part of antioxidant, 0.3 parts of additives, 0.05 parts of ultraviolet absorber, and 50 parts of gasoline; component B is a polar crosslinking phase, comprising by weight: 10 parts of HDI trimer, 5 parts of 4-hydroxybutyl acrylate, 0.01 parts of dibutyltin dilaurate, and 30 parts of toluene; the mass ratio of component A to component B is 8:1.

[0024] The additive is composed of tetrahydroxyethyl ethylenediamine and modified attapulgite in a mass ratio of 1:5.

[0025] The modified attapulgite clay is prepared using the following method: (1) After activating the attapulgite with 1 mol / L dilute HCl, it was reacted with KH792 silane coupling agent in toluene at 80℃ for 10-12 h to obtain KH792 modified attapulgite; the ratio of activated attapulgite, KH792 silane coupling agent and toluene was 10 g: 15 g: 100 mL.

[0026] (2) Disperse KH792 modified attapulgite in dichloromethane at a solid-liquid ratio of 1g:20mL to form a uniform dispersion.

[0027] (3) Dissolve azodicyanovalerate in dichloromethane at a ratio of 1g:10mL, then add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N,N-dimethylaminopyridine, and stir at room temperature for 1-2h to obtain an activated mixture; the mass ratio of azodicyanovalerate, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N,N-dimethylaminopyridine is 10:8:0.8.

[0028] (4) Mix the dispersion obtained in step (2) and the activated mixture obtained in step (3) at a volume ratio of 2:1, react at room temperature for 24-36 hours, centrifuge to separate the solid product after the reaction, wash repeatedly with deionized water and anhydrous ethanol several times, and vacuum dry at room temperature to constant weight to obtain the product.

[0029] The rubber mixture is composed of vulcanized natural rubber, natural rubber and maleic anhydride modified natural rubber in a mass ratio of 1:2:1.5.

[0030] The Mooney viscosity ML (1+4) of the natural rubber in component A is 60 at 100°C, and the Mooney viscosity ML (1+4) of the vulcanized natural rubber is 50 at 100°C.

[0031] The maleic anhydride-modified natural rubber is prepared by the following method: (i) By weight, 100 parts of natural rubber, 5 parts of maleic anhydride and 0.3 parts of dicumyl peroxide are added to the open mill and the roller temperature is controlled at 150°C. (ii) Mixing reaction for 15 minutes; (iii) Thinly sheet, cool, and granulate to obtain the maleic anhydride grafting rate of 0.5%.

[0032] The preparation method of the above-mentioned low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film includes the following steps: (1) Add the crushed vulcanized natural rubber, natural rubber, and maleic anhydride modified natural rubber to the open mill in proportion. Set the open mill temperature to 30°C, the roller gap to 0.5 mm, and the plasticizing time to 25 min until the rubber is completely softened and a uniform rubber mixture is formed. Finally, put the plasticized rubber mixture into the reactor that has been pre-added with solvent gasoline, keep the temperature at 30-40°C, stir for 1-2 h to make the rubber completely dissolved, and then add terpene resin, petroleum resin, antioxidant, additives, and ultraviolet absorber to the reactor in sequence, keep the temperature at 30-40°C, stir fully for 24 h to obtain component A. (2) Add toluene into a stirring vessel and control the stirring speed to 100-150 r / min. Add HDI trimer, 4-hydroxybutyl acrylate and dibutyltin dilaurate in sequence. Maintain the stirring temperature at 20-25℃ and the stirring time at 30-60 min to ensure that all components are completely dissolved and uniformly mixed to obtain component B. (3) Use dual metering pumps to synchronously transport component A and component B, control the mass ratio of component A to component B to be 8:1, and stabilize the output pressure of the dual pumps at 0.3-0.5MPa. Transport component A and component B synchronously to the static mixer. The residence time of the material in the static mixer is 5-10s, so as to realize the instantaneous and uniform mixing of the two-component adhesive liquid. The mixed adhesive liquid is directly fed into the slit coating head. The coating gap of the coating head is 50-100μm, and the coating speed is 1-3m / min, so as to form a uniform adhesive film layer on the surface of the polyethylene substrate. (4) The polyethylene substrate coated with adhesive film is sent into a hot air drying oven. The oven temperature is set to 70℃, the temperature deviation is controlled within ±2℃, the hot air speed is 1-2m / s, and the adhesive film stays in the oven for 3-5 minutes. Under these conditions, the low-temperature instant cross-linking reaction is completed, and then the finished product is obtained by winding.

[0033] Example 2 A low-temperature instant crosslinking rubber-type cold-resistant polyethylene protective film is prepared by coating a two-component rubber pressure-sensitive adhesive onto the surface of a polyethylene base film. The two-component rubber pressure-sensitive adhesive consists of component A and component B, wherein: component A is a non-polar rubber phase, comprising, by weight: 15 parts rubber mixture, 5 parts terpene resin, 10 parts petroleum resin, 1 part antioxidant, 1 part additive, 0.5 parts ultraviolet absorber, and 90 parts gasoline; component B is a polar crosslinking phase, comprising, by weight: 30 parts HDI trimer, 20 parts 4-hydroxybutyl acrylate, 0.3 parts dibutyltin dilaurate, and 60 parts toluene; the mass ratio of component A to component B is 10:1.

[0034] The additive is composed of tetrahydroxyethyl ethylenediamine and modified attapulgite in a mass ratio of 1:15.

[0035] The modified attapulgite clay is prepared using the following method: (1) After activating the attapulgite with 1 mol / L dilute HCl, it was reacted with KH792 silane coupling agent in toluene at 80℃ for 10-12 h to obtain KH792 modified attapulgite; the ratio of activated attapulgite, KH792 silane coupling agent and toluene was 10 g: 15 g: 100 mL.

[0036] (2) Disperse KH792 modified attapulgite in dichloromethane at a solid-liquid ratio of 1g:20mL to form a uniform dispersion.

[0037] (3) Dissolve azodicyanovalerate in dichloromethane at a ratio of 1g:10mL, then add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N,N-dimethylaminopyridine, and stir at room temperature for 1-2h to obtain an activated mixture; the mass ratio of azodicyanovalerate, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N,N-dimethylaminopyridine is 10:8:1.

[0038] (4) Mix the dispersion obtained in step (2) and the activated mixture obtained in step (3) at a volume ratio of 2:1, react at room temperature for 24-36 hours, centrifuge to separate the solid product after the reaction, wash repeatedly with deionized water and anhydrous ethanol several times, and vacuum dry at room temperature to constant weight to obtain the product.

[0039] The rubber mixture is composed of vulcanized natural rubber, natural rubber and maleic anhydride modified natural rubber in a mass ratio of 1:2:2.

[0040] The Mooney viscosity ML (1+4) of the natural rubber in component A is 60~80 at 100℃, and the Mooney viscosity ML (1+4) of the vulcanized natural rubber is 50~70 at 100℃.

[0041] The maleic anhydride-modified natural rubber is prepared by the following method: (i) By weight, 100 parts of natural rubber, 8 parts of maleic anhydride and 0.6 parts of dicumyl peroxide are added to the open mill and the roller temperature is controlled at 160°C. (ii) Mixing reaction for 15 minutes; (iii) Thinly sheet, cool, and granulate to obtain the maleic anhydride grafting rate of 2.0%.

[0042] The preparation method of the above-mentioned low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film includes the following steps: (1) Add the crushed vulcanized natural rubber, natural rubber, and maleic anhydride modified natural rubber to the open mill in proportion. Set the open mill temperature to 40℃, the roller gap to 1mm, and the plasticizing time to 15min until the rubber is completely softened and a uniform rubber mixture is formed. Finally, put the plasticized rubber mixture into the reactor that has been pre-added with solvent gasoline, keep the temperature at 30-40℃, stir for 1-2h to make the rubber completely dissolved, and then add terpene resin, petroleum resin, antioxidant, additives, and ultraviolet absorber to the reactor in sequence, keep the temperature at 30-40℃, stir fully for 24h to obtain component A. (2) Add toluene into a stirring vessel and control the stirring speed to 100-150 r / min. Add HDI trimer, 4-hydroxybutyl acrylate and dibutyltin dilaurate in sequence. Maintain the stirring temperature at 20-25℃ and the stirring time at 30-60 min to ensure that all components are completely dissolved and uniformly mixed to obtain component B. (3) Use dual metering pumps to synchronously transport component A and component B, control the mass ratio of component A to component B to be 10:1, and stabilize the output pressure of the dual pumps at 0.3-0.5MPa. Transport component A and component B synchronously to the static mixer. The residence time of the material in the static mixer is 5-10s, so as to realize the instantaneous and uniform mixing of the two-component adhesive liquid. The mixed adhesive liquid is directly fed into the slit coating head. The coating gap of the coating head is 50-100μm, and the coating speed is 1-3m / min, so as to form a uniform adhesive film layer on the surface of polyethylene substrate. (4) The polyethylene substrate coated with adhesive film is sent into a hot air drying oven. The oven temperature is set to 90℃, the temperature deviation is controlled within ±2℃, the hot air speed is 1-2m / s, and the adhesive film stays in the oven for 3-5 minutes. Under these conditions, the low-temperature instant cross-linking reaction is completed, and then the finished product is obtained by winding.

[0043] Example 3 A low-temperature instant crosslinking rubber-type cold-resistant polyethylene protective film is prepared by coating a polyethylene base film with a two-component rubber pressure-sensitive adhesive. The two-component rubber pressure-sensitive adhesive consists of component A and component B, wherein: component A is a non-polar rubber phase, comprising by weight: 10 parts of rubber mixture, 3 parts of terpene resin, 7 parts of petroleum resin, 0.5 parts of antioxidant, 0.7 parts of additives, 0.25 parts of ultraviolet absorber, and 70 parts of gasoline; component B is a polar crosslinking phase, comprising by weight: 20 parts of HDI trimer, 15 parts of 4-hydroxybutyl acrylate, 0.2 parts of dibutyltin dilaurate, and 50 parts of toluene; the mass ratio of component A to component B is 9:1.

[0044] The additive is composed of tetrahydroxyethyl ethylenediamine and modified attapulgite in a mass ratio of 1:10.

[0045] The modified attapulgite clay is prepared using the following method: (1) After activating the attapulgite with 1 mol / L dilute HCl, it was reacted with KH792 silane coupling agent in toluene at 80℃ for 10-12 h to obtain KH792 modified attapulgite; the ratio of activated attapulgite, KH792 silane coupling agent and toluene was 10 g: 15 g: 100 mL.

[0046] (2) Disperse KH792 modified attapulgite in dichloromethane at a solid-liquid ratio of 1g:20mL to form a uniform dispersion.

[0047] (3) Dissolve azodicyanovalerate in dichloromethane at a ratio of 1g:10mL, then add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N,N-dimethylaminopyridine, and stir at room temperature for 1-2h to obtain an activated mixture; the mass ratio of azodicyanovalerate, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N,N-dimethylaminopyridine is 10:8:0.9.

[0048] (4) Mix the dispersion obtained in step (2) and the activated mixture obtained in step (3) at a volume ratio of 2:1, react at room temperature for 24-36 hours, centrifuge to separate the solid product after the reaction, wash repeatedly with deionized water and anhydrous ethanol several times, and vacuum dry at room temperature to constant weight to obtain the product.

[0049] The rubber mixture is composed of vulcanized natural rubber, natural rubber and maleic anhydride modified natural rubber in a mass ratio of 1:2:1.8.

[0050] The Mooney viscosity ML(1+4) of the natural rubber in component A is 70 at 100°C, and the Mooney viscosity ML(1+4) of the vulcanized natural rubber is 60 at 100°C.

[0051] The maleic anhydride-modified natural rubber is prepared by the following method: (i) By weight, 100 parts of natural rubber, 6 parts of maleic anhydride and 0.4 parts of dicumyl peroxide are added to the open mill and the roller temperature is controlled at 155°C. (ii) Mixing reaction for 15 minutes; (iii) Thinly sheet, cool, and granulate to obtain the maleic anhydride grafting rate of 1.5%.

[0052] The preparation method of the above-mentioned low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film includes the following steps: (1) Add the crushed vulcanized natural rubber, natural rubber, and maleic anhydride modified natural rubber to the open mill in proportion. Set the open mill temperature to 50°C, the roller gap to 0.8 mm, and the plasticizing time to 20 min until the rubber is completely softened and a uniform rubber mixture is formed. Finally, put the plasticized rubber mixture into the reactor that has been pre-added with solvent gasoline, keep the temperature at 30-40°C, stir for 1-2 h to make the rubber completely dissolved, and then add terpene resin, petroleum resin, antioxidant, additives, and ultraviolet absorber to the reactor in sequence. Keep the temperature at 30-40°C and stir fully for 24 h to obtain component A. (2) Add toluene into a stirring vessel and control the stirring speed to 100-150 r / min. Add HDI trimer, 4-hydroxybutyl acrylate and dibutyltin dilaurate in sequence. Maintain the stirring temperature at 20-25℃ and the stirring time at 30-60 min to ensure that all components are completely dissolved and uniformly mixed to obtain component B. (3) Use dual metering pumps to synchronously transport component A and component B, control the mass ratio of component A to component B to be 9:1, and stabilize the output pressure of the dual pumps at 0.3-0.5MPa. Transport component A and component B synchronously to the static mixer. The residence time of the material in the static mixer is 5-10s, so as to realize the instantaneous and uniform mixing of the two-component adhesive liquid. The mixed adhesive liquid is directly fed into the slit coating head. The coating gap of the coating head is 50-100μm, and the coating speed is 1-3m / min, so as to form a uniform adhesive film layer on the surface of polyethylene substrate. (4) The polyethylene substrate coated with adhesive film is sent into a hot air drying oven. The oven temperature is set to 90℃, the temperature deviation is controlled within ±2℃, the hot air speed is 1-2m / s, and the adhesive film stays in the oven for 3-5 minutes. Under these conditions, the low-temperature instant cross-linking reaction is completed, and then the finished product is obtained by winding.

[0053] Comparative Example 1 A low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film differs from Example 1 in that the rubber mixture uses only a binary blend of vulcanized natural rubber and natural rubber, without maleic anhydride-modified natural rubber. The remaining raw materials, proportions, preparation steps, and process parameters are exactly the same as in Example 1.

[0054] Comparative Example 2 A low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film differs from Example 1 in that: the rubber mixture is composed of vulcanized natural rubber, natural rubber and maleic anhydride modified natural rubber in a mass ratio of 1:2:1; the mixing ratio of the three is different, but the other two are the same as in Example 1.

[0055] Comparative Example 3 A low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film differs from Example 1 in that: the rubber mixture is composed of vulcanized natural rubber, natural rubber and maleic anhydride modified natural rubber in a mass ratio of 1:2:3; the mixing ratio of the three is different, but the other two are the same as in Example 1.

[0056] Comparative Example 4 A low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film differs from Example 1 in that the additive in component A is only tetrahydroxyethyl ethylenediamine (excluding modified attapulgite), i.e., the additive is 0.3 parts of tetrahydroxyethyl ethylenediamine. The remaining components and preparation methods are the same as in Example 1.

[0057] Comparative Example 5 A low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film differs from Example 1 in that: only modified attapulgite clay is used as the additive, tetrahydroxyethyl ethylenediamine is removed, the total amount of additives remains unchanged at 0.3 parts, and the remaining raw materials, proportions, preparation steps and process parameters are exactly the same as in Example 1.

[0058] Comparative Example 6 A low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film differs from Example 1 in that: ordinary attapulgite is used instead of modified attapulgite, and it is not modified by KH792 silane coupling agent and azodicyanovalerate. The remaining raw materials, proportions, preparation steps and process parameters are exactly the same as in Example 1.

[0059] Comparative Example 7 A low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film differs from Example 1 in that: the additives consist of tetrahydroxyethyl ethylenediamine and modified attapulgite in a mass ratio of 1:3, while the remaining raw materials, proportions, preparation steps, and process parameters are exactly the same as in Example 1.

[0060] Comparative Example 8 A low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film differs from Example 1 in that: the additives consist of tetrahydroxyethyl ethylenediamine and modified attapulgite in a mass ratio of 1:20, while the remaining raw materials, proportions, preparation steps, and process parameters are exactly the same as in Example 1.

[0061] Comparative Example 9 A low-temperature instant crosslinked rubber-type cold-resistant polyethylene protective film differs from Example 1 in that: the aliphatic triisocyanate in component B is replaced with aromatic diisocyanate (TDI), while the remaining raw materials, proportions, preparation steps, and process parameters are exactly the same as in Example 1.

[0062] Performance testing The protective films prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to the following performance tests, and the test methods are as follows: Initial tack (rolling ball method): Refer to GB / T 4852-2002, and use the inclined rolling ball method for testing. The value is indicated by the steel ball number (the larger the value, the stronger the initial tack).

[0063] Holding power: Refer to GB / T 4851-2014, suspend a 1kg weight at 25℃, and record the time (h) for the tape to completely detach from the standard plate.

[0064] Low-temperature resistance: Cut the protective film into strips of 2cm×10cm, freeze them in a -30℃ low-temperature chamber for 24 hours, and then immediately bend them 180° around a 10mm diameter rod. Observe whether cracks or brittle fractures appear on the surface of the film.

[0065] Peel strength (low temperature): After the protective film is attached to the stainless steel plate, it is placed in an environment of -20℃ for 2 hours to equilibrate, and the peel strength (N / 25mm) at 180° is tested immediately at this temperature.

[0066] Residual adhesive rate test: The protective film was attached to a stainless steel plate and aged for 72 hours at 60℃ and 90%RH. It was then peeled off at a speed of 300mm / min. After peeling, the residual adhesive on the adhered surface was observed, and the mass fraction of the residual adhesive was quantitatively tested.

[0067] Crosslinking efficiency: Record the temperature and time for complete curing of the film and the gel content. Gel content: Peel the film off the substrate, weigh about 0.5g, wrap it with a 200-mesh stainless steel mesh, extract it in toluene using Soxhlet for 24h, dry it and weigh it. Calculate the gel content (%) = (mass after extraction / mass before extraction) × 100%.

[0068] The test results are shown in Table 1.

[0069] Table 1 Performance Test Results As can be seen from Table 1 above, Examples 1-3 of the present invention significantly outperform all comparative examples in core indicators such as crosslinking efficiency, holding power, low-temperature resistance, and residue resistance. This indicates that the present invention, through the precise design of a ternary rubber compound system, a two-component synergistic additive system, and an aliphatic isocyanate low-temperature crosslinking system, achieves a comprehensive improvement in the protective film in terms of low-temperature rapid crosslinking, high adhesion stability, excellent cold resistance, and residue-free properties. The present invention uses vulcanized natural rubber, natural rubber, and maleic anhydride-modified natural rubber in a weight ratio of 1:2:(1.5-2) to form a rubber mixture. Vulcanized natural rubber enhances the cohesive strength and creep resistance of the film, natural rubber ensures good initial tack and wettability, and maleic anhydride-modified natural rubber provides anhydride active sites for reaction with isocyanate. The three components synergistically construct a stable crosslinking precursor network. Comparative Example 1, without maleic anhydride-modified natural rubber, lacked active crosslinking sites, resulting in an inability to form an effective crosslinking network. This led to a holding power of only 6 hours, film brittleness at -30°C, a residual rubber rate as high as 8.2%, and a gel content of only 28.6%. Comparative Example 2 had an insufficient proportion of modified rubber, resulting in low crosslinking density and defects such as microcracks, residual rubber, and decreased adhesive strength. Comparative Example 3 had an excessive amount of modified rubber, leading to increased film hardness and a significant decrease in initial tack. Only under the specific compounding ratios defined in this invention can initial tack, holding power, low-temperature toughness, and crosslinking efficiency be balanced.

[0070] The additives of this invention are compounded with tetrahydroxyethyl ethylenediamine and modified attapulgite in a ratio of 1:(5-15). Tetrahydroxyethyl ethylenediamine provides hydroxyl and tertiary amine catalytic structures, accelerating the low-temperature crosslinking reaction of isocyanate; modified attapulgite improves dispersibility and provides active sites. The two work synergistically to achieve low-temperature, rapid, and uniform crosslinking. Comparative Example 4 uses only tetrahydroxyethyl ethylenediamine, lacking the synergistic effect of inorganic fillers, resulting in uneven crosslinking dispersion and decreased cohesive strength and cold resistance; Comparative Example 5 uses only modified attapulgite, lacking catalytic and crosslinking sites, making it difficult to trigger low-temperature crosslinking and significantly deteriorating performance; Comparative Example 6 uses ordinary attapulgite, with insufficient dispersibility and reactivity, reduced crosslinking efficiency, and slight cracks; Comparative Examples 7 and 8 have additive ratios exceeding the 1:(5-15) range, weakening the synergistic effect, and resulting in lower crosslinking density and overall performance than the examples. Only under the specified ratios of this invention can the additives fully exert their catalytic, crosslinking, and dispersing effects, achieving rapid curing at 70-90℃ for 3-5 minutes. Comparative Example 9 used aromatic diisocyanate (TDI) instead of HDI trimer. Due to poor low-temperature reactivity and high rigidity of the crosslinking product, the film cracked at -30°C, had a holding power of only 9 hours, high residual rate, and low gel content, failing to meet the requirements for cold-resistant use. This invention adopts an integrated process of simultaneous delivery by dual metering pumps, static mixing, slot coating, and 70-90°C hot air drying. Components A and B are mixed online in real time, avoiding the risk of premixed gel. Solvent evaporation and crosslinking curing are completed simultaneously within 3-5 minutes at 70-90°C. The crosslinking temperature is reduced by 30-50°C compared to traditional high-temperature crosslinking, and the curing time is shortened by more than 40%. It has low energy consumption, high safety, and is suitable for continuous industrial production. Examples 1-3, under optimal formulation and process, show that the initial tack of the steel ball reaches 15-16, the holding power is 80-82h, there are no cracks at -30℃, the low-temperature peel strength at -20℃ is 5.4-5.9N / 25mm, the residual adhesive rate is 0%, and the gel content is 91.3%-92.4%, which are all superior to the comparative examples and can meet the requirements for long-term stable use in low-temperature environments.

[0071] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

Claims

1. A low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film, characterized in that, It is prepared by coating a two-component rubber pressure-sensitive adhesive onto the surface of a polyethylene-based film; The two-component rubber pressure-sensitive adhesive is composed of component A and component B, wherein: Component A is a non-polar rubber phase, comprising, by weight: 7-15 parts rubber mixture, 1-5 parts terpene resin, 1-10 parts petroleum resin, 0.1-1 parts antioxidant, 0.3-1 parts additives, 0.05-0.5 parts ultraviolet absorber, and 50-90 parts gasoline; the additives are composed of tetrahydroxyethyl ethylenediamine and modified attapulgite in a mass ratio of 1:(5-15); the rubber mixture is composed of vulcanized natural rubber, natural rubber, and maleic anhydride-modified natural rubber; Component B is a polar crosslinked phase, comprising, by weight: 10-30 parts of aliphatic triisocyanate, 5-20 parts of 4-hydroxybutyl acrylate, 0.01-0.3 parts of dibutyltin dilaurate, and 30-60 parts of toluene.

2. The low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film according to claim 1, characterized in that, The mass ratio of component A to component B is (8-10):

1.

3. The low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film according to claim 1, characterized in that, The Mooney viscosity ML(1+4) of the natural rubber in component A is 60~80 at 100℃, and the Mooney viscosity ML(1+4) of the vulcanized natural rubber is 50~70 at 100℃.

4. The low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film according to claim 1, characterized in that, The aliphatic triisocyanate in component B is a hexamethylene diisocyanate trimer.

5. The low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film according to claim 1, characterized in that, The weight ratio of vulcanized natural rubber, natural rubber and maleic anhydride modified natural rubber in the rubber mixture is 1:2:(1.5-2).

6. The low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film according to claim 1, characterized in that, The maleic anhydride-modified natural rubber has a maleic anhydride grafting rate of 0.5% to 2.0%, and is prepared by a method comprising the following steps: (i) adding 100 parts by weight of natural rubber, 5-8 parts by weight of maleic anhydride, and 0.3-0.6 parts by weight of dicumyl peroxide into a two-roll mill, with the roller temperature controlled at 150-160°C; (ii) mixing and reacting for 10-15 minutes; (iii) passing the mixture through a thin sheet, cooling, and pelletizing to obtain the final product.

7. The low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film according to claim 1, characterized in that, The modified attapulgite clay is prepared using the following method: (1) After activating the attapulgite with 1 mol / L dilute HCl, it was reacted with KH792 silane coupling agent in toluene at 80℃ for 10-12 h to obtain KH792 modified attapulgite. (2) Disperse KH792 modified attapulgite in dichloromethane at a solid-liquid ratio of 1g:20mL to form a uniform dispersion; (3) Dissolve azodicyanovalerate in dichloromethane at a ratio of 1g:10mL, then add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N,N-dimethylaminopyridine, and stir at room temperature for 1-2h to obtain an activated mixture. (4) Mix the dispersion obtained in step (2) and the activated mixture obtained in step (3) at a volume ratio of 2:1, react at room temperature for 24-36 hours, centrifuge to separate the solid product after the reaction, wash repeatedly with deionized water and anhydrous ethanol several times, and vacuum dry at room temperature to constant weight to obtain the product.

8. The low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film according to claim 7, characterized in that, In step (1), the ratio of activated attapulgite, KH792 silane coupling agent, and toluene is 10g:15g:100mL.

9. The low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film according to claim 7, characterized in that, In step (3), the mass ratio of azobiscyanopentanoic acid, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and N,N-dimethylaminopyridine is 10:8:(0.8-1).

10. A method for preparing a low-temperature instant cross-linked rubber-type cold-resistant polyethylene protective film according to any one of claims 1-9, characterized in that, Includes the following steps: (1) Add the crushed vulcanized natural rubber, natural rubber, and maleic anhydride modified natural rubber to the open mill in proportion. Set the open mill temperature to 30-50℃, the roller gap to 0.5-1mm, and the plasticizing time to 15-25min until the rubber is completely softened and a uniform rubber mixture is formed. Finally, put the plasticized rubber mixture into the reactor that has been pre-added with solvent gasoline, keep the temperature at 30-40℃, stir for 1-2h to make the rubber completely dissolved, and then add terpene resin, petroleum resin, antioxidant, additives, and ultraviolet absorber to the reactor in sequence, keep the temperature at 30-40℃, stir fully for 24h to obtain component A. (2) Add toluene into a stirring vessel and control the stirring speed to 100-150 r / min. Add aliphatic triisocyanate, 5-20 parts of 4-hydroxybutyl acrylate and dibutyltin dilaurate in sequence. Maintain the stirring temperature at 20-25℃ and the stirring time at 30-60 min to ensure that all components are completely dissolved and uniformly mixed to obtain component B. (3) A component A and component B are transported synchronously by dual metering pumps, wherein pump 1 transports component A and pump 2 transports component B. The mass ratio of component A to component B is controlled to be 10:1-8:

1. The output pressure of the two pumps is stabilized at 0.3-0.5MPa. Component A and component B are transported synchronously to the static mixer. The residence time of the material in the static mixer is 5-10s, so as to realize the instantaneous and uniform mixing of the two-component adhesive liquid. The mixed adhesive liquid is directly fed into the slit coating head. The coating gap of the coating head is 50-100μm and the coating speed is 1-3m / min, so as to form a uniform adhesive film layer on the surface of the polyethylene substrate. (4) The polyethylene substrate coated with adhesive film is sent into a hot air drying oven. The oven temperature is set to 70℃-90℃, the temperature deviation is controlled within ±2℃, the hot air speed is 1-2m / s, and the adhesive film stays in the oven for 3-5 minutes. Under these conditions, the low-temperature instant cross-linking reaction is completed, and then the finished product is obtained by winding.

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