Pressure-sensitive adhesive for optical cable and optical cable

Abstract

A pressure-sensitive adhesive for an optical cable and an optical cable. The pressure-sensitive adhesive is used for being arranged on the outer surface of a sheath of an optical cable and comprises a main resin, a cross-linking agent, a nano inorganic flame retardant, a phosphate flame retardant and a tackifier, wherein the main resin at least comprises a polymer with a crosslinkable group, and the polymer and the cross-linking agent are used for forming a cross-linked network structure from the pressure-sensitive adhesive. The visible light transmittance of the pressure-sensitive adhesive is 10% or above. The pressure-sensitive adhesive can have both good transparency, good flame retardance, adhesion, etc., such that the optical cable has a relatively good invisible effect and good laying reliability.

Description

Pressure-sensitive adhesive for optical cable and optical cable

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on November 29, 2023, with application number 202311621728.1 and application name “Pressure-sensitive adhesive for optical cables and optical cables”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The embodiments of the present application relate to the technical field of home optical cables, and specifically to a pressure-sensitive adhesive for optical cables and an optical cable. Background Art

[0003] With the advent of the 5G era of the Internet of Everything, people are placing higher demands on home networking. FTTR (Fiber to the Room) is a new home network coverage model that runs indoor fiber optic cables to every room in a user's home, ensuring high internet speeds in every room.

[0004] Optical cables used in FTTR scenarios typically consist of optical fibers, fibers embedded in a sheath, and an adhesive layer applied to the sheath. To ensure fire safety, the adhesive layer must possess excellent flame retardancy. However, adhesive layers with excellent flame retardancy typically have poor transparency, resulting in poor cable invisibility.

[0005] Summary of the Invention

[0006] In view of this, an embodiment of the present application provides a pressure-sensitive adhesive for an optical cable to solve the problem that the existing adhesive layer used for an optical cable cannot achieve both good transparency and flame retardancy.

[0007] Specifically, the first aspect of an embodiment of the present application provides a pressure-sensitive adhesive for optical cable, which is used to be arranged on the outer surface of the sheath of the optical cable, and the pressure-sensitive adhesive includes a main resin, a cross-linking agent, a nano-inorganic flame retardant, a phosphate flame retardant and a tackifier, wherein the main resin at least contains a polymer with a cross-linkable group, and the polymer and the cross-linking agent are used to make the pressure-sensitive adhesive form a cross-linked network structure; the visible light transmittance of the pressure-sensitive adhesive is above 10%.

[0008] The simultaneous introduction of nano-inorganic flame retardants and phosphate flame retardants into the pressure-sensitive adhesive can ensure that the flame retardant performance of the pressure-sensitive adhesive is relatively good. At the same time, the compatibility between the nano-inorganic flame retardant and the main resin can be promoted with the help of the phosphate flame retardant, and the above-mentioned cross-linked network structure of the pressure-sensitive adhesive can reduce the precipitation of the nano-inorganic flame retardant, thereby ensuring that the visible light transmittance of the pressure-sensitive adhesive is still relatively high and the bonding reliability is high.

[0009] In the embodiment of the present application, the peak heat release rate of the pressure-sensitive adhesive is less than or equal to 600 kW / m 2This reflects that the pressure-sensitive adhesive of this application has good flame retardancy.

[0010] In some embodiments of the present application, the visible light transmittance of the pressure-sensitive adhesive is above 50%, and the peak heat release rate is less than or equal to 400 kW / m 2 In this case, the pressure-sensitive adhesive can better balance high transparency and excellent flame retardancy.

[0011] In the embodiment of the present application, the softening point of the pressure-sensitive adhesive is between 100-125° C. A higher softening point can reflect that the pressure-sensitive adhesive of the present application has good thermal stability and is not prone to creep.

[0012] In the embodiment of the present application, the adhesive layer formed by the pressure-sensitive adhesive has a peeling force greater than or equal to 0.4 N / m on the polyethylene terephthalate film. Even when the pressure-sensitive adhesive of the embodiment of the present application contains a nano inorganic flame retardant, its adhesion is still good, and the polyethylene terephthalate film is not easily peeled off from the pressure-sensitive adhesive layer.

[0013] In the embodiment of the present application, the total weight percentage of the nano inorganic flame retardant and the phosphate flame retardant in the pressure sensitive adhesive is 5-40%. Controlling the sum of the weight percentages of the nano inorganic flame retardant and the phosphate flame retardant within this range is conducive to ensuring good flame retardancy and transparency of the pressure sensitive adhesive.

[0014] In the embodiment of the present application, the mass ratio of the nano inorganic flame retardant to the phosphate flame retardant is (0.2-1.2): 1. The application of these two flame retardants in the pressure-sensitive adhesive at such a mass ratio is more conducive to the synergistic flame retardant effect of the two and more conducive to the uniform dispersion of the nano inorganic flame retardant in the pressure-sensitive adhesive.

[0015] In the embodiment of the present application, the nano-inorganic flame retardant accounts for 5-20% by weight of the pressure-sensitive adhesive. When both the nano-inorganic flame retardant and the phosphate flame retardant are present in the pressure-sensitive adhesive, the mass proportion of the former within this range is more conducive to the pressure-sensitive adhesive having good transparency and its flame retardant properties are not too weak.

[0016] In the embodiment of the present application, the size of the nano inorganic flame retardant is between 1nm and 500nm. The smaller size of the inorganic flame retardant is more conducive to its good dispersion in the pressure-sensitive adhesive system, ensuring high transparency and good adhesion of the pressure-sensitive adhesive.

[0017] In the embodiments of the present application, the nano inorganic flame retardant includes one or more of aluminum phosphate, zinc phosphate, aluminum hypophosphite, and zinc oxide; the phosphate ester flame retardant includes one or more of hexadecyl phosphate, octadecyl phosphate, tetraphenyl bisphenol A diphosphate, bisphenol A bis(diphenyl phosphate), resorcinol bis(diphenyl phosphate), cyclic phosphate, and triethyl phosphate. These phosphate ester flame retardants have relatively good flame retardancy, and in the presence of these phosphate ester flame retardants, the inorganic flame retardants have better dispersion in the pressure-sensitive adhesive system.

[0018] In an embodiment of the present application, the cross-linkable group includes one or more of an epoxy group, a carboxyl group, a sulfonic acid group, a hydroxyl group, and an amino group.

[0019] In some embodiments of the present application, the crosslinkable groups include carboxyl groups and / or sulfonic acid groups, and the crosslinking agent includes a metal salt; wherein the metal ions in the metal salt can form non-covalent ionic bonds with the carboxyl groups and / or sulfonic acid groups. Ionic crosslinks ensure that the pressure-sensitive adhesive maintains a good network structure and good thermal stability at moderately high temperatures, while dissociating at even higher temperatures, facilitating reprocessing and coating of the pressure-sensitive adhesive.

[0020] In an embodiment of the present application, the metal ion in the metal salt includes one of zinc ion, magnesium ion, iron ion, cobalt ion, and manganese ion.

[0021] In the embodiment of the present application, the crosslinking agent accounts for 0.2% to 10% of the total weight of the pressure-sensitive adhesive. The addition of an appropriate amount of crosslinking agent can provide the pressure-sensitive adhesive with a moderately crosslinked network structure, imparting good thermal stability, while not degrading the adhesive properties and optical properties of the pressure-sensitive adhesive due to an excessive amount of crosslinking agent.

[0022] In some embodiments of the present application, the main resin further comprises a resin without a cross-linkable group. In this case, the pressure-sensitive adhesive contains both types of main resins, which has excellent mechanical properties, especially better elasticity.

[0023] In some embodiments of the present application, the polymer with crosslinkable groups accounts for 1% to 20% by weight of the pressure-sensitive adhesive, and the resin without crosslinkable groups accounts for 10% to 60% by weight of the pressure-sensitive adhesive. By adjusting the weight ratios of these two main resins in the pressure-sensitive adhesive, it is possible to achieve comprehensive control over the thermal stability, elasticity, adhesion, transparency, and other properties of the pressure-sensitive adhesive.

[0024] In the embodiment of the present application, the main resin accounts for 30% to 70% of the total mass of the pressure-sensitive adhesive. Controlling the total mass proportion of the main resin in the pressure-sensitive adhesive within the above range is conducive to the good dispersion of the above two types of flame retardants in the system, resulting in high transparency and good adhesion of the pressure-sensitive adhesive.

[0025] In the embodiment of the present application, the pressure-sensitive adhesive comprises the following raw materials, calculated by weight: 32-70 parts of a main resin; 0.5-3 parts of a cross-linking agent; 5-15 parts of a nano-inorganic flame retardant; 5-30 parts of a phosphate ester flame retardant; 20-150 parts of a tackifier; 0-100 parts of a softening oil; and 0-2 parts of an additive. By properly adjusting the raw materials and their proportions, the pressure-sensitive adhesive can achieve excellent transparency, flame retardancy, adhesion, thermal stability, and other properties.

[0026] A second aspect of the embodiments of the present application provides an optical cable comprising a sheath, an optical fiber, and an adhesive layer, wherein the optical fiber is located within the sheath, and the adhesive layer is disposed on at least a portion of the outer surface of the sheath, and the adhesive layer utilizes the pressure-sensitive adhesive described in the first aspect of the embodiments of the present application. Because the adhesive layer in the optical cable utilizes the pressure-sensitive adhesive having high transparency, good flame retardancy, and excellent mechanical properties, the optical cable exhibits excellent stealth, fire resistance, and installation reliability.

[0027] In the embodiment of the present application, the thickness of the adhesive layer is 50-600 μm. The adhesive layer has a suitable thickness to ensure reliable adhesion.

[0028] In the embodiment of the present application, the fireproof grade of the optical cable is above Eca grade. The adhesive layer of the optical cable adopts the pressure-sensitive adhesive with good flame retardancy, and the fireproof performance of the optical cable is also good accordingly.

[0029] In some embodiments of the present application, the optical cable further comprises a release film disposed on the surface of the adhesive layer. The release film can protect the adhesive layer and can be removed before installing the optical cable.

[0030] In the embodiment of the present application, the optical fiber is a single-core optical fiber or a multi-core optical fiber.

[0031] In some embodiments of the present application, the optical cable further includes a conductor, and the conductor is located inside the sheath. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG1A is a schematic diagram of a three-dimensional structure of an optical cable.

[0033] FIG. 1B is a side view of the optical cable shown in FIG. 1A .

[0034] FIG1C is another structural schematic diagram of an optical cable shown in an embodiment of the present application.

[0035] FIG2 is another structural schematic diagram of an optical cable shown in an embodiment of the present application.

[0036] FIG3 is another structural schematic diagram of an optical cable according to an embodiment of the present application. DETAILED DESCRIPTION

[0037] The embodiments of the present application will be described below with reference to the accompanying drawings.

[0038] In the FTTR solution, optical cables installed between the main optical modem and the information boxes in each room of the home can be used to transmit optical signals between the two, ensuring that each room has a stable network point. Please refer to Figures 1A and 1B , which illustrate an optical cable according to an embodiment of the present application. Figure 1A is a schematic diagram of the three-dimensional structure of the optical cable, and Figure 1B is a side view of the optical cable shown in Figure 1A .

[0039] The optical cable 100 includes a sheath 10, an optical fiber 20, and an adhesive layer 30, wherein the optical fiber 20 is located inside the sheath 10, and the adhesive layer 30 is provided on at least a portion of the surface of the sheath 10. The optical fiber 20 is used to transmit optical signals. For example, after the optical cable 100 is connected to the main optical modem in the home and the information box in each room, the optical fiber 20 in the optical cable realizes signal transmission between the main optical modem and the information box. The optical fiber in the optical cable 100 can be a single-core optical fiber or a multi-core optical fiber. The position marked 20 in Figures 1A and 1B is for placing an optical fiber to realize single-core communication. In other embodiments of the present application, multiple optical fibers can also be placed in the sheath 10 to realize multi-core communication.

[0040] The sheath 10 is used to wrap the optical fiber 20, etc., and can isolate the optical fiber 20 from the external environment, thereby protecting the optical fiber 20 and preventing the optical fiber 20 from being damaged by collision with the external environment during transportation or installation. When installing the optical cable 100, the sheath 10 at the outer periphery of the end of the optical fiber 20 can be partially torn off to expose the end of the optical fiber 20, and the optical fiber 20 can be fused or connected with an FMC connector, and then connected to an information box and a main optical modem. In other cases, the two ends of the optical fiber 20 in the optical cable 100 can be directly prefabricated with connectors. In this way, when installing the optical cable, the sheath 10 at the outer periphery of the end of the optical fiber 20 can be partially torn off to expose the prefabricated connector at the end of the main optical fiber 20, and finally the prefabricated connector can be connected to the information box, etc.

[0041] An adhesive layer 30 is provided on at least a portion of the outer surface (i.e., part or all of the outer surface) of the jacket 10. The adhesive layer 30 allows the optical cable to be bonded to the wall between the main optical modem and the information box. It is understood that the adhesive layer 30 is provided on the surface of the jacket 10 facing the wall. Figures 1A and 1B illustrate the adhesive layer 30 being provided on a portion of the lower surface of the jacket 10. It is understood that the extended width of the adhesive layer 30 (i.e., the length along the x-axis in the figures) can be less than or equal to the extended width of the jacket 10. Figures 1A and 1B illustrate the extended width of the adhesive layer 30 being slightly less than the extended width of the jacket 10. Furthermore, to enhance the bonding reliability of the optical cable, at least a portion of the outer surface of the jacket 10 can be configured as a plane, with the adhesive layer 30 provided on this plane. This allows the adhesive layer 30 to be stably fixed to the outer surface of the jacket 10, while also allowing the jacket 10 to be stably fixed to the wall via the horizontal adhesive layer 30.

[0042] Among them, the adhesive layer 30 can be a pressure-sensitive adhesive layer or a hot-melt adhesive layer, and the pressure-sensitive adhesive layer is more common. If the adhesive layer 30 is a pressure-sensitive adhesive layer, during the installation of the optical cable, the sheath 10 can be bonded to the wall to be installed with the optical cable by pressing the pressure-sensitive adhesive layer to make it sticky. However, the pressure-sensitive adhesive used for the adhesive layer 30 cannot take into account both good transparency and flame retardancy. If the transparency of the pressure-sensitive adhesive is too low, the invisible effect of the optical cable 100 will be poor, the aesthetics will be affected, and it will not be able to adapt to different home decoration styles; if the pressure-sensitive adhesive is basically not flame retardant or the flame retardancy is too poor, it will cause the optical cable to fail to meet indoor fire safety requirements, and open flames will damage the sheath, optical fiber, etc. of the optical cable. Based on this, the embodiment of the present application provides a pressure-sensitive adhesive that can be used for the adhesive layer 30 in the optical cable, so that the adhesive layer 30 can take into account both good transparency and flame retardancy.

[0043] Specifically, the adhesive layer 30 in the optical cable 100 is a pressure-sensitive adhesive layer, which can be formed using the following pressure-sensitive adhesive according to the embodiment of the present application. The pressure-sensitive adhesive includes a main resin, a cross-linking agent, a nano-inorganic flame retardant, a phosphate flame retardant, and a tackifier. The main resin includes at least a polymer with cross-linkable groups. The polymer and the cross-linking agent are used to form a cross-linked network structure in the pressure-sensitive adhesive. The visible light transmittance (i.e., "transparency") of the pressure-sensitive adhesive is greater than 10%.

[0044] The pressure-sensitive adhesive (PSA) is a composite of a nanoscale inorganic flame retardant and an organic flame retardant, a phosphate flame retardant. The combination of these two types of flame retardants ensures excellent flame retardancy, enabling optical cables employing the PSA to meet indoor flame retardancy requirements. Furthermore, the inorganic nanoscale flame retardant is relatively small in size, which has little effect on the PSA's transparency. Furthermore, the phosphate flame retardant exhibits excellent compatibility with the main resin in the system, establishing a compatible bridge between the nanoscale inorganic flame retardant and the main resin, preventing the powdered inorganic flame retardant from precipitating and ensuring uniform dispersion within the PSA. Furthermore, the crosslinked network formed by the crosslinkable polymer and the crosslinking agent effectively restrains the flame retardant, helping to reduce the aggregation and precipitation of the flame retardant, thereby maintaining the PSA's transparency (visible light transmittance exceeding 10%) and adhesion. Furthermore, the crosslinked network formed by the crosslinkable polymer and the crosslinking agent also imparts to the PSA excellent thermal stability, making it less susceptible to creep and providing high adhesion reliability. Therefore, the pressure-sensitive adhesive provided in the embodiments of the present application can take into account good flame retardancy, transparency, adhesion and stability, and has high application aesthetics and reliability.

[0045] The phrase "the polymer and the crosslinking agent are used to form a crosslinked network structure" specifically means that the polymer forms covalent or non-covalent crosslinks with the crosslinking agent via its crosslinkable groups, thereby providing the pressure-sensitive adhesive with a crosslinked network structure. Non-covalent crosslinks may be, for example, ionic bonds, which can dissociate under certain conditions. In this application, the term "creep" refers to the phenomenon in which a solid material experiences an increase in strain over time while maintaining a constant stress.

[0046] In this application, the term "visible light transmittance" refers to the percentage of visible light that passes through the surface of an object in a certain environment. This parameter can reflect the appearance and transparency of an object. Visible light transmittance can be tested by adhering a 20-50 μm thick pressure-sensitive adhesive layer formed from the aforementioned pressure-sensitive adhesive to optical glass and measuring its visible light transmittance using a spectrophotometer. In this application, the visible light transmittance of the pressure-sensitive adhesive can be greater than 20%, greater than 30%, greater than 40%, greater than 45%, greater than 50%, greater than 55%, greater than 60%, greater than 66%, greater than 70%, greater than 75%, greater than 80%, greater than 85%, or greater than 90%. In some embodiments of this application, the visible light transmittance of the pressure-sensitive adhesive is greater than 50%. A higher visible light transmittance of a pressure-sensitive adhesive indicates greater transparency, which helps it meet the invisible requirements of optical cables. In some embodiments, the visible light transmittance of the pressure-sensitive adhesive is between 50% and 85%. In this case, the pressure-sensitive adhesive also exhibits improved flame retardancy.

[0047] In the embodiment of the present application, the peak heat release rate (PHRR) of the pressure sensitive adhesive is less than or equal to 600 kW / m 2 . PHRR is the maximum value of the heat release rate of the material during the entire combustion period. The size of PHRR represents the maximum degree of heat release when the material burns. The smaller the value, the less heat the material releases during combustion, and the smaller the fire hazard. The PHRR can be measured using a cone calorimeter on a pressure-sensitive adhesive sample of a certain shape (a cube with a thickness of 3 mm and a length × width of 100 mm × 100 mm). The test standard is GB / T 16172-2007. Specifically, the peak heat release rate of the pressure-sensitive adhesive is less than or equal to 500kW / m 2 , or less than or equal to 400kW / m 2 , or less than or equal to 300kW / m 2 , or less than or equal to 250kW / m 2 wait.

[0048] In some embodiments of the present application, the visible light transmittance of the pressure-sensitive adhesive is above 50%, and the peak heat release rate is less than or equal to 400 kW / m 2 This reflects that the pressure-sensitive adhesive can better balance good transparency and flame retardancy.

[0049] In the embodiment of the present application, the softening point of the pressure-sensitive adhesive is above 100°C. It can further be above 110°C. The term "softening point" refers to the temperature at which a substance softens, and mainly refers to the temperature at which a substance begins to soften. The softening point of the pressure-sensitive adhesive in the embodiment of the present application is at a suitably high temperature, which may reflect that the pressure-sensitive adhesive has good thermal stability. In some embodiments of the present application, the softening point of the pressure-sensitive adhesive is between 110-125°C. In this case, the pressure-sensitive adhesive can better maintain its cross-linked network structure below 100°C, is not prone to creep and thus causes its adhesion to decrease, and has high thermal stability. At the same time, the pressure-sensitive adhesive can have a certain reprocessing ability at high temperatures, which is convenient for application.

[0050] In an embodiment of the present application, the adhesive layer formed by the pressure-sensitive adhesive has a peeling force greater than or equal to 0.4 N / m on a polyethylene terephthalate (PET) film. The strong peeling force exhibited by the pressure-sensitive adhesive layer on PET indicates that it has good bonding properties and can effectively achieve adhesion between the optical cable sheath and the wall, preventing the installed optical cable from falling off the wall. The pressure-sensitive adhesive of the embodiment of the present application still has good adhesion when containing a nano inorganic flame retardant, which can also indicate to a certain extent that the nano inorganic flame retardant can be fully dispersed in the system. In some embodiments of the present application, the peeling force of the adhesive layer formed by the pressure-sensitive adhesive on the PET film is greater than or equal to 0.5 N / m, or greater than or equal to 0.6 N / m, or greater than or equal to 0.7 N / m, or greater than or equal to 0.8 N / m, or greater than or equal to 0.9 N / m, etc. In some embodiments, the peeling force of the adhesive layer formed by the pressure-sensitive adhesive on the PET film is between 0.4 N / m and 0.8 N / m. In this case, the pressure-sensitive adhesive can also have high visible light transmittance and flame retardancy.

[0051] Among them, the above-mentioned peeling force can be tested by the following method: first heat the pressure-sensitive adhesive to 180°C to make it have good fluidity, then coat the pressure-sensitive adhesive on the steel plate, and quickly attach a PET film (about 50 μm thick) to the pressure-sensitive adhesive. After cooling, a pressure-sensitive adhesive layer with a thickness of 50 μm is formed between the steel plate and the PET film. Use a tensile testing machine to peel off the PET film at room temperature of 25°C to test the peeling force of the pressure-sensitive adhesive layer on the PET.

[0052] The pressure-sensitive adhesive of the embodiment of the present application still has good elastic properties when containing both the nano inorganic flame retardant and the phosphate flame retardant. The Young's modulus of the pressure-sensitive adhesive can be in the range of 20-1000 MPa.

[0053] In the embodiment of the present application, the size of the nano inorganic flame retardant can be between 1nm-500nm. Exemplarily, the size of the nano inorganic flame retardant can be specifically 2nm, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 200nm, 300nm, 400nm, etc. In some embodiments, the size of the nano inorganic flame retardant can be 1nm-200nm, 1nm-100nm, 5nm-200nm, or 5nm-100nm, etc. Smaller-sized nano inorganic flame retardants are more conducive to achieving good dispersion effect in the pressure-sensitive adhesive system, ensuring that the pressure-sensitive adhesive has higher transparency and better adhesion.

[0054] In the embodiments of the present application, the nano-inorganic flame retardant includes one or more of, but is not limited to, aluminum phosphate (chemical formula: AlPO4), zinc phosphate (chemical formula: Zn3(PO4)2), aluminum hypophosphite (chemical formula: Al(H2PO2)3), and zinc oxide (chemical formula: ZnO). These inorganic flame retardants have excellent flame retardant properties. In particular, aluminum phosphate, zinc phosphate, and aluminum hypophosphite are all phosphorus-containing inorganic flame retardants. They have better compatibility with phosphorus-containing phosphate flame retardants, which in turn allows for better dispersibility in pressure-sensitive adhesive systems.

[0055] In the embodiment of the present application, the phosphate flame retardant may include but is not limited to one or more of hexadecyl phosphate, octadecyl phosphate, tetraphenyl bisphenol A diphosphate, bisphenol A bis(diphenyl phosphate), resorcinol bis(diphenyl phosphate), triethyl phosphate, and cyclic phosphate.

[0056] In an embodiment of the present application, the total mass proportion of the nano-inorganic flame retardant and the phosphate flame retardant in the pressure-sensitive adhesive is 5-40%. When the nano-inorganic flame retardant and the phosphate flame retardant are both present in the pressure-sensitive adhesive, the total mass proportion of the two is within this range, which is conducive to ensuring that the flame retardancy and transparency of the pressure-sensitive adhesive are good. Specifically, the total mass proportion can be 10%, 12%, 15%, 16%, 17%, 18%, 20%, 25%, 28%, 30%, 36%, etc. In some embodiments, the total mass proportion is 10%-40%. When the total mass proportion of the two is within this range, the two flame retardants are not easy to precipitate, the transparency of the pressure-sensitive adhesive is higher, the adhesion is higher, and the pressure-sensitive adhesive has good flame retardancy.

[0057] In the embodiment of the present application, the mass ratio of the nano inorganic flame retardant to the phosphate flame retardant can be (0.2-1.2):1. In this case, it is more conducive to the two flame retardants to exert a synergistic flame retardant effect, and the solid nano inorganic flame retardant is better compatible with the organic matter such as the matrix resin and tackifier in the pressure sensitive adhesive with the help of the phosphate flame retardant, ensuring that the pressure sensitive adhesive has higher transparency while having the same flame retardant effect; or in other words, ensuring that the pressure sensitive adhesive has better flame retardancy while having the same transparency. Specifically, the mass ratio is, for example, 0.3:1, 0.5:1, 0.7:1, 0.8:1, 0.9:1, 1.0:1, 1.1:1, 1.15:1, 1.2:1, etc. In some embodiments, the mass ratio is (0.5-1.2):1.

[0058] In the embodiment of the present application, when a nano inorganic flame retardant and a phosphate flame retardant are both present in the above-mentioned pressure-sensitive adhesive, the mass proportion of the nano inorganic flame retardant in the pressure-sensitive adhesive can be less than 30%, and the pressure-sensitive adhesive can still be guaranteed to have good transparency. In some embodiments of the present application, the mass proportion of the nano inorganic flame retardant in the pressure-sensitive adhesive can be 5-20%, for example, specifically 6%, 7%, 8%, 10%, 12%, 15%, etc., and can further be within the range of 5-10%. The mass proportion of the phosphate flame retardant in the pressure-sensitive adhesive can be 5-20%, for example, specifically 6%, 7%, 8%, 10%, 12%, 15%, etc., and can further be within the range of 5-10%.

[0059] In the embodiment of the present application, the crosslinkable group of the polymer may include one or more of an epoxy group, a carboxyl group (-COOH), a sulfonic acid group (-SO3H), a hydroxyl group (-OH), and an amino group, but is not limited thereto. The amino group should be understood in a broad sense and may be a primary amino group (-NH2), or a secondary amino group (-NHR, where R may be a substituted or unsubstituted alkyl or aryl group). In some embodiments, the polymer may be a styrene block copolymer with a crosslinkable group, such as a carboxyl-modified styrene block copolymer (e.g., a maleic anhydride-modified styrene block copolymer).

[0060] In some embodiments of the present application, the crosslinking agent is capable of forming covalent crosslinks with the polymer having crosslinkable groups. In this case, the crosslinking agent has at least two corresponding reactive groups capable of reacting with the crosslinkable polar groups. A crosslinked network structure with covalent crosslinks exhibits greater thermal stability.

[0061] When the crosslinkable group is an epoxy group, the crosslinking agent capable of forming a covalent bond with the polymer having the crosslinkable group includes one or more of a substance having at least two amino groups in its molecular structure, a substance having at least two carboxyl groups, and an acid anhydride. Specifically, the crosslinking agent includes one or more of an amine crosslinking agent (such as a diprimary amine, a disecondary amine, or a ditertiary amine), an acid anhydride crosslinking agent, and an acid crosslinking agent (such as a dicarboxylic acid or a polycarboxylic acid).

[0062] When the cross-linkable group is a carboxyl group, the cross-linking agent includes one or more of a substance having at least two hydroxyl groups, a substance having at least two amino groups, or a substance having at least two epoxy groups in its molecular structure. For example, the cross-linking agent includes one or more of an alcohol cross-linking agent (such as a diol, a polyol, or a resin with a hydroxyl group), an amine cross-linking agent, and an epoxy cross-linking agent (such as an epoxy resin or a difunctional epoxy small molecule).

[0063] When the crosslinkable group is a hydroxyl group, the crosslinking agent includes one or more of a substance having at least two isocyanate groups, a substance having at least two carboxyl groups, or a substance having at least two ester groups in its molecular structure. In other words, the crosslinking agent includes one or more of an isocyanate crosslinking agent (such as a diisocyanate or polyisocyanate), a carboxylic acid crosslinking agent, and an ester crosslinking agent (such as a dicarboxylic acid ester).

[0064] When the crosslinkable group is an amino group, the crosslinking agent includes one or more of a substance having at least two epoxy groups, at least two carboxyl groups, at least two isocyanate groups, and anhydride substances in its molecular structure. Specifically, the crosslinking agent includes one or more of an epoxy crosslinking agent, a carboxylic acid crosslinking agent, an isocyanate crosslinking agent, and an acid anhydride crosslinking agent.

[0065] In some other embodiments of the present application, the cross-linking agent can form a non-covalent cross-linking bond with a polymer with a cross-linkable group. For example, when the cross-linkable group includes a carboxyl group and / or a sulfonic acid group, the cross-linking agent includes a metal salt. In this case, the metal ions in the metal salt can form a non-covalent ionic bond with the carboxyl group and / or the sulfonic acid group. Among them, the ionic bond can enable the above-mentioned pressure-sensitive adhesive to maintain a stable cross-linked network structure below a certain temperature (such as below 100°C), thereby improving its thermal stability. When subjected to high temperature (such as above 180°C), the ionic bond can dissociate, so that the pressure-sensitive adhesive exhibits a certain fluidity, which is convenient for its re-melting processing and coating, etc. For example, a block-shaped pressure-sensitive adhesive containing ionic bonds in a cross-linked network structure has good thermal stability and will not creep below 100°C. When the block-shaped pressure-sensitive adhesive is subjected to high-temperature treatment, the ionic bonds can be broken, and the pressure-sensitive adhesive can be melt-processed into other shapes, such as dots, which are convenient for spot coating. This makes the pressure-sensitive adhesive have low requirements for coating equipment and can be used to make pressure-sensitive adhesive layers on various types of optical cables.

[0066] In the embodiment of the present application, the metal ion in the metal salt includes but is not limited to one of zinc ion, magnesium ion, iron ion, cobalt ion, manganese ion, etc. The ionic bonds formed by these metal ions with carboxyl groups, sulfonic acid groups, etc. are relatively strong. The anion in the metal salt can be a halogen-free anion. In some embodiments, the metal salt can be acetylacetonate, sulfate, acetate, benzenesulfonate, etc. of the metal ion. In some embodiments, the metal salt is a zinc salt, for example, zinc acetylacetonate, zinc sulfate, zinc benzenesulfonate, etc.

[0067] In the embodiment of the present application, the total weight proportion of the crosslinking agent in the pressure-sensitive adhesive can be 0.2%-10%. The addition of an appropriate amount of crosslinking agent can give the pressure-sensitive adhesive good thermal stability through the crosslinked network structure with covalent or non-covalent crosslinking bonds formed between the crosslinking agent and the polymer with crosslinkable groups, while not reducing the adhesive properties and optical properties of the pressure-sensitive adhesive due to excessive content of the crosslinking agent. Specifically, the weight proportion of the crosslinking agent can be 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, 1.6%, 1.8%, 1.9%, 2%, 2.5%, 3%, 4%, 5%, 8%, etc.

[0068] In embodiments of the present application, the polymer with crosslinkable groups comprises at least 1% by weight of the pressure-sensitive adhesive. This ensures that the pressure-sensitive adhesive has a suitably high-strength crosslinked network structure at low temperatures (e.g., below 100°C), thereby providing good thermal stability and mechanical properties. In some embodiments, the polymer with crosslinkable groups comprises at least 2% by weight of the pressure-sensitive adhesive.

[0069] In some embodiments of the present application, the main resin further comprises a resin without crosslinkable groups. In this case, the main resin in the pressure-sensitive adhesive comprises both a polymer with crosslinkable groups and a resin without crosslinkable groups. While the polymer with crosslinkable groups is introduced to form the crosslinked network structure of the pressure-sensitive adhesive, the resin without crosslinkable groups is also introduced. This allows for the elasticity of the pressure-sensitive adhesive to be controlled, ensuring that the pressure-sensitive adhesive layer formed by the pressure-sensitive adhesive has good elasticity and is resistant to cracking. It also allows for the regulation of the pressure sensitivity and adhesion of the pressure-sensitive adhesive.

[0070] The resin without a crosslinkable group may be one or more of a styrene block copolymer without a crosslinkable group, an ethylene-vinyl acetate copolymer, a polyurethane, etc. For example, the styrene block polymer may include a styrene diblock copolymer or a styrene triblock copolymer, for example, one or more selected from styrene-ethylene (SE) copolymer, styrene-isoprene-styrene (SIS) copolymer, styrene-ethylene-butylene-styrene (SEBS) copolymer, styrene-butylene-styrene (SBS) copolymer, styrene-ethylene-propylene-styrene (SEPS) copolymer, styrene-ethylene-propylene (SEP) copolymer, etc.

[0071] In the embodiment of the present application, the mass proportion of the polymer with crosslinkable groups in the pressure-sensitive adhesive can be 1%-20%, and the mass proportion of the resin without crosslinkable groups in the pressure-sensitive adhesive can be 10%-60%. By regulating the mass proportion of these two main resins in the pressure-sensitive adhesive, it is possible to achieve comprehensive regulation of the thermal stability, elasticity, adhesion, transparency, etc. of the pressure-sensitive adhesive. Among them, the polymer with crosslinkable groups with a suitable content can form a crosslinked network structure with an appropriate number of covalent or non-covalent crosslinks through its crosslinkable groups and the crosslinking agent, thereby controlling the effect of the crosslinking bonds on the chemical crosslinking, which is beneficial to improving the thermal stability and mechanical properties of the pressure-sensitive adhesive, and reducing the precipitation of flame retardants, while ensuring that the adhesion and transparency of the pressure-sensitive adhesive remain high.

[0072] Specifically, the mass proportion of the polymer with crosslinkable groups in the pressure-sensitive adhesive can be 1%, 2%, 2.2%, 2.5%, 3%, 3.5%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15% or 18%, etc. The mass proportion of the resin without crosslinkable groups in the pressure-sensitive adhesive can be, for example, 15%, 20%, 25%, 30%, 35%, 40%, 42%, 45%, 48%, 50% or 55%, etc. Furthermore, the mass ratio of the resin without crosslinkable groups to the polymer with crosslinkable groups is greater than 1, that is, the mass proportion of the former in the pressure-sensitive adhesive is greater than the latter. This can help ensure that the pressure-sensitive adhesive is not over-crosslinked and too hard.

[0073] In some embodiments of the present application, the mass proportion of the polymer with crosslinkable groups in the pressure-sensitive adhesive is 1%-10%, and the mass proportion of the resin without crosslinkable groups in the pressure-sensitive adhesive can be 20%-50%. The mass proportions of the two main resins are respectively within the above ranges, which is conducive to the pressure-sensitive adhesive having a moderate crosslinked network structure while taking into account good thermal stability and good elasticity, and can also make the total mass proportion of the two within a suitable range, so that the above-mentioned phosphate flame retardant is fully dispersed in the pressure-sensitive adhesive system, which is conducive to the dispersion of the nano-inorganic flame retardant, so that the pressure-sensitive adhesive has a highly transparent appearance, good adhesion, high cohesive strength, and excellent flame retardant properties. In some embodiments, the mass proportion of the polymer with crosslinkable groups in the pressure-sensitive adhesive can be in the range of 2%-5%. The mass proportion of the resin without crosslinkable groups in the pressure-sensitive adhesive can be in the range of 25%-40%.

[0074] In the embodiment of the present application, the total mass proportion of the main resin in the pressure-sensitive adhesive is 30%-70%. Specifically, when the main resin in the pressure-sensitive adhesive is only a polymer with a cross-linkable group, the mass proportion of the polymer is 30%-70%; when the main resin in the pressure-sensitive adhesive includes both a polymer with a cross-linkable group and a resin without a cross-linkable group, the total mass proportion of the polymer with a cross-linkable group and the resin without a cross-linkable group is 30%-70%. Controlling the total mass proportion of the main resin in the pressure-sensitive adhesive within the above range is conducive to the good dispersion of the above two types of flame retardants in the system, making the pressure-sensitive adhesive have high transparency and good adhesion. Specifically, the total mass proportion can be, for example, 32%, 35%, 40%, 42%, 45%, 50%, 55%, 60%, 65%, or 68%. In order to ensure that the pressure-sensitive adhesive has high transparency, good adhesion, thermal stability and elasticity, in some embodiments, the total mass proportion of the main resin in the pressure-sensitive adhesive is 30%-60%, and further can be 32%-45%.

[0075] In this application, the tackifier in the pressure-sensitive adhesive can be used to enhance its adhesion and, together with the main resin, impart good adhesion to the pressure-sensitive adhesive. The tackifier can be selected from one or more of hydrogenated rosin resin, terpene resin, petroleum resin, and the like. Furthermore, the weight percentage of the tackifier in the pressure-sensitive adhesive is generally greater than 10%, and can further be greater than 20%.

[0076] In some embodiments of the present application, the pressure-sensitive adhesive may further contain softening oil. The softening oil may include one or more of cyclohexane oil, aromatic oil, paraffin oil, etc. The softening oil may be used to increase the fluidity of the mixed raw materials used to prepare the pressure-sensitive adhesive, thereby facilitating the processing of the pressure-sensitive adhesive. It may also soften the main resin so that the hardness of the pressure-sensitive adhesive is not too hard. Of course, in some other embodiments of the present application, the pressure-sensitive adhesive may also not contain softening oil. In the present application, the pressure-sensitive adhesive may contain softening oil in an amount not exceeding 50% by mass, and further contain softening oil in an amount not exceeding 40% by mass.

[0077] In some embodiments of the present application, the pressure-sensitive adhesive may further contain an additive. The additive may be selected from one or more of an antioxidant and an anti-ultraviolet agent. The additive can be used to reduce yellowing of the pressure-sensitive adhesive layer during use, thereby improving long-term reliability. Of course, in other embodiments of the present application, the pressure-sensitive adhesive may also be free of additives. In the present application, the pressure-sensitive adhesive may contain no more than 3% by weight of an additive.

[0078] In the embodiments of the present application, the pressure-sensitive adhesive described above does not contain halogen elements. For example, the flame retardants, crosslinking agents, etc. do not contain halogen elements. When such a pressure-sensitive adhesive is applied to an optical cable, it has essentially no corrosive effect on the cable jacket 10. While halogen-free, the pressure-sensitive adhesive containing the aforementioned nano-inorganic flame retardant and phosphate flame retardant can still exhibit excellent flame retardancy, meeting the halogen-free flame retardancy requirements of optical cables.

[0079] In the embodiment of the present application, the pressure-sensitive adhesive may include the following raw materials in parts by weight:

[0080] 32-70 parts of a main resin; wherein the main resin comprises at least a polymer with a cross-linkable group;

[0081] 0.5-3 parts of a cross-linking agent;

[0082] 5-15 parts of nano inorganic flame retardant;

[0083] 5-30 parts of phosphate flame retardant;

[0084] 20-150 parts of a tackifier;

[0085] 0-100 parts of softening oil;

[0086] 0-2 parts of additives.

[0087] By rationally adjusting the raw materials and their proportions, the pressure-sensitive adhesive can achieve excellent transparency, flame retardancy, adhesion, thermal stability, and other properties. A softening oil or additive in the pressure-sensitive adhesive of 0 parts by weight indicates that the adhesive contains no softening oil or additive. In some cases, the phosphate flame retardant can be present in the pressure-sensitive adhesive in an amount of 5-15 parts by weight.

[0088] In some embodiments of the present application, the pressure-sensitive adhesive may include the following raw materials in parts by weight:

[0089] 2-10 parts of a polymer with a cross-linkable group;

[0090] 30-60 parts of a resin without crosslinkable groups;

[0091] 0.5-3 parts of a cross-linking agent;

[0092] 5-15 parts of nano inorganic flame retardant;

[0093] 5-30 parts of phosphate flame retardant;

[0094] 20-150 parts of a tackifier;

[0095] 0-100 parts of softening oil;

[0096] 0-2 parts of additives.

[0097] In the application, above-mentioned pressure-sensitive adhesive can be melt-mixed by will comprising each raw material of main body resin, cross-linking agent, nano inorganic flame retardant, phosphate flame retardant, tackifier, be cooled to normal temperature, obtain pressure-sensitive adhesive.Wherein, melt-mixing can be carried out in high-temperature internal mixer or twin-screw extruder, and the purpose of melting can make each raw material melt, to reach better mixed effect, particularly be helpful for the abundant dispersion of powdery nano inorganic flame retardant in system.In addition, when melt-mixing, for reaching better mixed effect, can earlier main body resin, nano inorganic flame retardant, phosphate flame retardant, softening oil etc. are mixed, add tackifier, auxiliary agent etc. again afterwards, add cross-linking agent at last, to impel to form cross-linked network structure.Certainly, also all raw materials can be added in the mixing plant together.

[0098] The obtained pressure-sensitive adhesive can be a solid adhesive material, such as a block. When the pressure-sensitive adhesive is used in an optical cable, the solid adhesive material can be remelted and applied to the outer surface of the optical cable sheath by dispensing or other methods. After cooling, a pressure-sensitive adhesive layer is formed, such as the adhesive layer 30 mentioned above.

[0099] The pressure-sensitive adhesive provided in the embodiments of this application can achieve good transparency, flame retardancy, thermal stability, adhesion, and elasticity, and can be used in optical cables to form a pressure-sensitive adhesive layer on the cable sheath, thereby providing a stable bond between the cable and the wall on which it is to be laid, preventing the cable from falling off. Furthermore, the pressure-sensitive adhesive provides a transparent appearance and good stealth, adapting to different home decoration styles. It also provides the cable with good flame retardancy, meeting indoor fire safety requirements. Furthermore, the pressure-sensitive adhesive provided in the embodiments of this application can also be used in other fields with high requirements for transparency and flame retardancy of the adhesive layer, and is not limited to application in optical cables.

[0100] As previously described in this application, the adhesive layer 30 in the optical cable 100 can be a pressure-sensitive adhesive layer formed using the pressure-sensitive adhesive of the embodiments of this application. The thickness of the adhesive layer 30 can be set as needed, and the thickness of the adhesive layer 30 can be, for example, 50 μm to 600 μm. A suitable thickness can ensure more reliable adhesion of the adhesive layer 30. In some embodiments, the thickness of the adhesive layer 30 can be 80 μm, 100 μm, 150 μm, 200 μm, 300 μm, 400 μm, 500 μm, etc.

[0101] As previously mentioned in this application, the visible light transmittance of the adhesive layer 30 using the above-mentioned pressure-sensitive adhesive is above 10%, and can further be above 50%. This indicates that the transparency of the adhesive layer 30 is high. The softening point of the adhesive layer 30 using the above-mentioned pressure-sensitive adhesive is between 100-125°C, and can further be between 110-125°C. This indicates that the thermal stability of the adhesive layer 30 is good. The peak heat release rate of the adhesive layer 30 using the above-mentioned pressure-sensitive adhesive is less than or equal to 600kW / m2 , further can be less than or equal to 400kW / m 2 This indicates that the adhesive layer 30 has good flame retardant properties.

[0102] Based on the good flame retardant performance of the adhesive layer 30, the CPR certified fire rating of the optical cable 100 using it can be above the Eca level. The good fire / flame retardant performance of the optical cable 100 facilitates the indoor application of the optical cable. Among them, the CPR certification is a special certification for building products under the EU CE certification system. The fire rating of the optical cable CPR certification is evaluated according to the EN13501-6 standard, and Eca is one of the grade indicators. The complete CPR certified optical cable fire rating includes Aca, B1ca, B2ca, Cca, Dca, Eca and Fca in order from low to high. In other words, the fire rating of the optical cable 100 in the embodiment of the present application can reach the Eca level or the Fca level.

[0103] Continuing to refer to FIG. 1A and FIG. 1B , in some embodiments, to facilitate tearing off the jacket 10, a groove 101 may be provided on the jacket 10. The groove 101 may be provided in a first radial direction of the optical fiber 20 (i.e., the z-axis direction in the figure), and the groove 101 extends from one end of the jacket 10 to the other end along an extension direction (the extension direction of the groove 101 is parallel to the length direction of the jacket 10, i.e., the y-axis direction in the figure). In other words, the extension length of the groove 101 is consistent with the extension length of the jacket 10. The jacket 10 can be easily torn off from the groove, and the end of the optical fiber 20 can be quickly exposed, further improving the installation efficiency of the optical cable, or improving the maintenance efficiency of the optical cable after the optical fiber 20 is damaged.

[0104] The cross-sectional shape of the groove 101 along the radial direction of the optical fiber 20 can be any shape such as an inverted trapezoid, a rectangle, a square and a triangle. The cross-sectional shape of the groove 101 along the radial direction of the optical fiber 20 in Figure 1A is specifically a triangle, wherein the vertex of the triangle is located at the bottom of the groove 101 (the groove wall opposite to the opening of the groove), so that it is easier to tear the sheath 10 from the bottom of the groove 101. In addition, the number of grooves 101 set on the sheath 10 can be one or two. The two grooves 101 in Figure 1A are respectively arranged on opposite sides of the sheath 10 along the z-axis direction. That is, the two grooves 101 are arranged on the upper surface and the lower surface of the sheath 10. The adhesive layer 30 may or may not cover the groove 101 on the surface of the sheath 10 where it is located. When the adhesive layer 30 does not cover the groove 101 (as shown in Figure 2 below), it is easier to tear the sheath 10 from the groove later and retain the end of the optical fiber 20.

[0105] In some embodiments of the present application, referring to FIG1C , the optical cable 100 further includes a release film 40; the release film 40 is disposed on the surface of the adhesive layer 30, specifically, on the surface of the adhesive layer 30 facing away from the sheath 10. The release film 40 is removable and is disposed on the surface of the adhesive layer 30 before the optical cable 100 is installed. It protects the adhesive layer 30, prevents adhesion of the optical cable during transportation and storage, and prevents the surface to be bonded of the adhesive layer 30 from being contaminated by the external environment. When installing the optical cable 100 of the embodiment of the present application, the release film 40 on the surface of the adhesive layer 30 can be torn off first, and then the optical cable 100 can be stably bonded to the wall through the adhesive layer 30, thereby improving the laying efficiency of the optical cable of the embodiment of the present application, and also improving the laying reliability of the optical cable of the embodiment of the present application.

[0106] In some other embodiments of the present application, referring to FIG2 , the optical cable 100 further includes two conductors 50 . Both the optical fiber 20 and the conductors 50 are located within the sheath 10 , and the optical fiber 20 and the conductors 50 extend in the same direction. In this case, the optical cable shown in FIG2 can be referred to as an "optoelectronic composite cable." The conductors 50 serve as conductors and are generally disposed around the outer periphery of the optical fiber 20 without contacting the optical fiber 20. In FIG2 , the optical fiber 20 is disposed at the center of the sheath 10, and the two conductors 50 are symmetrically disposed around the outer periphery of the optical fiber 20. The conductors 50 are typically copper wires.

[0107] While Figures 1A through 1C and 2 illustrate single-core optical fibers 20, it is understood that optical cables can also include multiple optical fibers. As shown in Figure 3, optical cable 100 can include multiple optical fibers 20 to achieve multi-core communication. The optical fibers 20 are spaced apart, but are all encased in a common sheath 10.

[0108] Generally speaking, the adhesive layer 30 of the optical cable 100 provided in the embodiment of the present application adopts the above-mentioned pressure-sensitive adhesive, so that the optical cable has good stealth, flame retardancy and laying reliability, thereby facilitating the widespread application of the FTTR solution.

[0109] The embodiments of the present application are further described below with reference to a number of embodiments.

[0110] Example 1

[0111] A pressure-sensitive adhesive comprising the following raw materials in parts by weight:

[0112] Maleic anhydride modified styrene block polymer: 5 parts;

[0113] Styrene block polymer without crosslinkable groups: 60 parts;

[0114] Nano inorganic flame retardant (specifically aluminum hypophosphite with an average particle size of 80 nm): 15 parts;

[0115] Phosphate flame retardant (specifically resorcinol bis(diphenyl phosphate)): 15 parts;

[0116] Tackifier (specifically hydrogenated rosin resin): 20 parts;

[0117] Naphthenic oil: 50 parts;

[0118] Cross-linking agent (specifically zinc acetylacetonate): 3 parts;

[0119] Additives (antioxidant + anti-UV agent): 2 parts.

[0120] Among them, the above-mentioned pressure-sensitive adhesive can be prepared by the following method: first, maleic anhydride modified styrene block polymer, styrene block polymer without crosslinkable groups, nano inorganic flame retardant, phosphate flame retardant, and cyclohexane oil are added to a high-temperature internal mixer to melt and mix evenly, then a tackifier and an auxiliary agent are added to melt mix, and then a crosslinking agent is added to melt mix, and finally cooled to room temperature to obtain a solid pressure-sensitive adhesive.

[0121] Example 2

[0122] A pressure-sensitive adhesive is obtained by melt-mixing the following raw materials in parts by weight:

[0123] Maleic anhydride modified styrene block polymer: 5 parts;

[0124] Styrene block polymer without crosslinkable groups: 40 parts;

[0125] Polyurethane without crosslinkable groups: 20 parts;

[0126] Ethylene-vinyl acetate copolymer without crosslinkable groups: 20 parts;

[0127] Nano inorganic flame retardant (specifically aluminum phosphate with a particle size of 500 nm): 15 parts;

[0128] Cyclic phosphate flame retardant: 15 parts;

[0129] Tackifier (specifically hydrogenated rosin resin): 20 parts;

[0130] Naphthenic oil: 50 parts;

[0131] Cross-linking agent (specifically zinc acetylacetonate): 3 parts;

[0132] Additives (antioxidant + anti-UV agent): 2 parts.

[0133] The preparation method of the pressure-sensitive adhesive of Example 2 is basically the same as that of Example 1.

[0134] Example 3

[0135] A pressure-sensitive adhesive, the preparation of which is mainly different from that of Example 1 in that a resin without a cross-linkable group is not used.

[0136] Specifically, the pressure-sensitive adhesive of Example 3 is obtained by melt-mixing the following raw materials in parts by weight:

[0137] Maleic anhydride modified styrene block polymer: 60 parts;

[0138] Nano inorganic flame retardant (same as in Example 1): 15 parts;

[0139] Phosphate flame retardant (same as in Example 1): 15 parts;

[0140] Tackifier (specifically hydrogenated rosin resin): 40 parts;

[0141] Naphthenic oil: 50 parts;

[0142] Cross-linking agent (specifically zinc acetylacetonate): 3 parts;

[0143] Additives (antioxidant + anti-UV agent): 2 parts.

[0144] Example 4

[0145] A pressure-sensitive adhesive, which differs from Example 1 mainly in that the total weight of the nano-inorganic flame retardant and the phosphate flame retardant is still 30 parts, but the nano-inorganic flame retardant is 10 parts and the phosphate flame retardant is 20 parts.

[0146] Example 5

[0147] A pressure-sensitive adhesive, which differs from Example 1 mainly in that the total weight of the nano-inorganic flame retardant and the phosphate flame retardant is still 30 parts, but the nano-inorganic flame retardant is 20 parts and the phosphate flame retardant is 10 parts.

[0148] Example 6

[0149] A pressure-sensitive adhesive is obtained by melt-mixing the following raw materials in parts by weight:

[0150] Maleic anhydride modified styrene block polymer: 5 parts;

[0151] Styrene block polymer without crosslinkable groups: 55 parts;

[0152] Nano inorganic flame retardant: 15 parts;

[0153] Phosphate flame retardant: 30 parts;

[0154] Hydrogenated rosin resin: 20 parts;

[0155] Naphthenic oil: 40 parts;

[0156] Cross-linking agent: 3 parts;

[0157] Additives: 2 parts.

[0158] Example 7

[0159] A pressure-sensitive adhesive is obtained by melt-mixing the following raw materials in percentage by weight:

[0160] Maleic anhydride modified styrene block polymer: 2.9%;

[0161] Styrene block polymer without crosslinkable groups: 42.9%;

[0162] Nano inorganic flame retardant: 5%;

[0163] Phosphate flame retardant: 5%;

[0164] Hydrogenated rosin resin: 11.8%;

[0165] Naphthenic oil: 29.4%;

[0166] Cross-linking agent: 1.8%;

[0167] Additives: 1.2%.

[0168] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0169] Comparative Example 1

[0170] A pressure-sensitive adhesive is provided, which differs from Example 1 in that the flame retardant in the raw materials for preparing the pressure-sensitive adhesive is only 30 parts by weight of a nano-inorganic flame retardant and does not contain a phosphate flame retardant.

[0171] Comparative Example 2

[0172] A pressure-sensitive adhesive is provided, which differs from Example 1 in that the flame retardant in the raw materials for preparing the pressure-sensitive adhesive is only 30 parts by weight of a phosphate flame retardant, and does not contain a nano inorganic flame retardant.

[0173] Comparative Example 3

[0174] A pressure-sensitive adhesive is obtained by melt-mixing the following raw materials in parts by weight:

[0175] Styrene block polymer without crosslinkable groups: 68 parts;

[0176] Nano inorganic flame retardant: 15 parts;

[0177] Phosphate flame retardant: 15 parts;

[0178] Hydrogenated rosin resin: 20 parts;

[0179] Naphthenic oil: 50 parts;

[0180] Additives: 2 parts.

[0181] In order to strongly support the beneficial effects brought about by the technical solutions of the embodiments of the present application, the pressure-sensitive adhesives provided in the above embodiments and comparative examples were subjected to various performance tests as shown in Table 1 below, and the results are also summarized in Table 1 below.

[0182] Table 1 Performance test results of pressure sensitive adhesive

[0183] As can be seen from Table 1, compared to Comparative Examples 1-2 in which the pressure-sensitive adhesive contains only an inorganic flame retardant or an organophosphate flame retardant, the pressure-sensitive adhesive of the present application embodiment simultaneously introduces a nano-inorganic flame retardant and an organophosphate flame retardant, and by virtue of the cross-linked network structure formed by the cross-linkable polymer and the cross-linking agent in the main resin, the two flame retardants are inhibited from precipitating. This allows the pressure-sensitive adhesive of the present application embodiment to better balance transparency and flame retardancy, while also having good adhesion and thermal stability. In addition, as can be seen from the comparison between Examples 1 and 4 and Example 5, when the mass ratio of the nano-inorganic flame retardant to the phosphate flame retardant in the pressure-sensitive adhesive is in the range of 0.5 to less than 2, the pressure-sensitive adhesive has better visible light transmittance and adhesion.

[0184] Furthermore, the pressure-sensitive adhesive of each embodiment of the present application is used to form a pressure-sensitive adhesive layer on the outer surface of the sheath of the optical cable. The optical cable can have a good stealth effect and a high fire protection level (the CPR certified fire protection level can be above the Eca level), and has good adhesion on walls such as latex paint. The market competitiveness of the optical cable is outstanding.

[0185] It should be noted that the terms "disposed", "connected", "installed", etc. in this application should be understood in a broad sense. For example, they can refer to direct disposition, connection, or installation, or they can refer to indirect disposition, connection, or installation through an intermediate medium. Directional terms mentioned in this application, such as "upper", "lower", "front", "back", "left", "right", "inside", "outside", "front", "back", "bottom", "top", "side", etc., are only used to better and more clearly illustrate and understand this application, and do not indicate or imply that the referred components must have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limitations on this application.

[0186] It should be understood that the terms "first", "second", etc. used in this application are only used for the purpose of description and are not intended to limit the scope of this application. In the description of this application, unless otherwise stated, the meaning of "multiple (kinds)" refers to greater than or equal to two (kinds). "At least one (kind)" refers to one (kind) or more (kinds). "At least one of the following (individuals)" or similar expressions refer to any combination of these items, including any combination of single items (individuals) or plural items (individuals). For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0187] In addition, the numerical range represented by "-" in this application refers to the range including the numerical values ​​recorded before and after "-" as the minimum and maximum values, respectively. In this application, expressions about parameter ranges, such as "greater than or equal to (≥)", "less than or equal to (≤)", "above...", and "below..." all include the number itself. The numerical values ​​and numerical ranges involved in the embodiments of this application are approximate values. Due to the influence of manufacturing process / testing method, etc., there may be a certain range of errors, which can be considered negligible by those skilled in the art.

Claims

1. A pressure-sensitive adhesive for an optical cable, used to be arranged on the outer surface of the sheath of the optical cable, characterized in that: The pressure-sensitive adhesive comprises a main resin, a cross-linking agent, a nano inorganic flame retardant, a phosphate flame retardant and a tackifier, wherein the main resin at least contains a polymer with a cross-linkable group, and the polymer and the cross-linking agent are used to form a cross-linked network structure for the pressure-sensitive adhesive; the visible light transmittance of the pressure-sensitive adhesive is above 10%.

2. The pressure-sensitive adhesive according to claim 1, characterized in that: The peak heat release rate of the pressure-sensitive adhesive is less than or equal to 600 kW / m 2 .

3. The pressure-sensitive adhesive according to claim 1 or 2, characterized in that: The pressure-sensitive adhesive has a visible light transmittance of more than 50% and a peak heat release rate of less than or equal to 400 kW / m 2 .

4. The pressure-sensitive adhesive according to any one of claims 1 to 3, characterized in that: The softening point of the pressure sensitive adhesive is between 100-125°C.

5. The pressure-sensitive adhesive according to any one of claims 1 to 4, characterized in that: The peeling force of the adhesive layer formed by the pressure-sensitive adhesive on the polyethylene terephthalate film is greater than or equal to 0.4 N / m.

6. The pressure-sensitive adhesive according to any one of claims 1 to 5, characterized in that: The total weight of the nano inorganic flame retardant and the phosphate flame retardant in the pressure sensitive adhesive accounts for 5-40%.

7. The pressure-sensitive adhesive according to claim 6, characterized in that: The mass ratio of the nano inorganic flame retardant to the phosphate flame retardant is (0.2-1.2):

1.

8. The pressure-sensitive adhesive according to claim 6 or 7, characterized in that: The mass proportion of the nano inorganic flame retardant in the pressure sensitive adhesive is 5-20%.

9. The pressure-sensitive adhesive according to any one of claims 1 to 8, characterized in that: The size of the nano inorganic flame retardant is between 1nm and 500nm.

10. The pressure-sensitive adhesive according to any one of claims 1 to 9, characterized in that: The nano inorganic flame retardant includes one or more of aluminum phosphate, zinc phosphate, aluminum hypophosphite, and zinc oxide; The phosphate flame retardant includes one or more of hexadecyl phosphate, octadecyl phosphate, tetraphenyl bisphenol A diphosphate, bisphenol A bis(diphenyl phosphate), resorcinol bis(diphenyl phosphate), cyclic phosphate, and triethyl phosphate.

11. The pressure-sensitive adhesive according to any one of claims 1 to 10, characterized in that: The crosslinkable group includes one or more of an epoxy group, a carboxyl group, a sulfonic acid group, a hydroxyl group, and an amino group.

12. The pressure-sensitive adhesive according to any one of claims 1 to 11, characterized in that: The cross-linkable groups include carboxyl groups and / or sulfonic acid groups, and the cross-linking agent includes a metal salt; wherein the metal ions in the metal salt can form non-covalent ionic bonds with the carboxyl groups and / or the sulfonic acid groups.

13. The pressure-sensitive adhesive according to claim 12, characterized in that: The metal ion in the metal salt includes one of zinc ion, magnesium ion, iron ion, cobalt ion and manganese ion.

14. The pressure-sensitive adhesive according to any one of claims 1 to 13, characterized in that: The cross-linking agent accounts for 0.2%-10% of the total mass of the pressure-sensitive adhesive.

15. The pressure-sensitive adhesive according to any one of claims 1 to 14, characterized in that: The main resin also includes a resin without a cross-linkable group.

16. The pressure-sensitive adhesive according to claim 15, characterized in that: The mass proportion of the polymer with cross-linkable groups in the pressure-sensitive adhesive is 1%-20%, and the mass proportion of the resin without cross-linkable groups in the pressure-sensitive adhesive is 10%-60%.

17. The pressure-sensitive adhesive according to any one of claims 1 to 16, characterized in that: The main resin accounts for 30%-70% of the total mass of the pressure-sensitive adhesive.

18. The pressure-sensitive adhesive according to any one of claims 1 to 17, characterized in that: The pressure-sensitive adhesive comprises the following raw materials in parts by weight: 32-70 parts of main resin; 0.5-3 parts of a cross-linking agent; 5-15 parts of nano inorganic flame retardant; 5-30 parts of phosphate flame retardant; 20-150 parts of tackifier; 0-100 parts of softening oil; 0-2 parts of additives.

19. An optical cable, characterized in that: The optical cable comprises a sheath, an optical fiber, and an adhesive layer, wherein the optical fiber is located inside the sheath, the adhesive layer is arranged on at least a portion of the outer surface of the sheath, and the adhesive layer adopts the pressure-sensitive adhesive according to any one of claims 1-18.

20. The optical cable according to claim 19, characterized in that The thickness of the adhesive layer is 50-600 μm.

21. The optical cable according to any one of claims 19 to 20, characterized in that: The fire protection level of the optical cable is above Eca level.

22. The optical cable according to any one of claims 19 to 21, characterized in that: The optical cable further comprises a release film; the release film is arranged on the surface of the adhesive layer.

23. The optical cable according to any one of claims 19 to 22, characterized in that: The optical fiber is a single-core optical fiber or a multi-core optical fiber.

24. The optical cable according to any one of claims 19 to 23, characterized in that: The optical cable further comprises a conductor, wherein the conductor is located inside the sheath.

Images