Special high-temperature-resistant hot melt adhesive for bonding PP (polypropylene) and PE (polyethylene) and application thereof

Abstract

The invention relates to a high-temperature-resistant hot melt adhesive special for bonding PP and PE and application of the high-temperature-resistant hot melt adhesive. According to the hot melt adhesive, through the double-end modification design of the functionalized olefin block copolymer (OBC), polar groups are introduced according to the characteristics of PE and PP chain segments, and the interface bonding strength and high-temperature resistance of PP and PE are remarkably improved through the synergistic effect of auxiliaries such as the chain extender and the tackifying resin. The hot melt adhesive middle layer can be compounded with PP-R and PE-RT pipes through a three-layer co-extrusion process to form a stable multi-layer structure, and the PP-R and PE-RT composite pipe is suitable for a pipeline system in a high-temperature and high-pressure environment.

Description

Technical Field

[0001] The present invention relates to the field of hot melt adhesives, and particularly relates to a high-temperature resistant hot melt adhesive specifically for bonding PP and PE and its application. Background Art

[0002] Polyethylene (PE) materials and polypropylene (PP) materials have poor compatibility and cannot be directly melted together. When producing plastic products with a multi-layer composite structure (such as an anti-freezing composite pipe with an outer layer of PP-R and an inner layer of PE-RT), a suitable hot melt adhesive is required that has good bonding strength with both polyethylene (PE) and polypropylene (PP). Currently, the materials used for bonding polyethylene (PE) or polypropylene (PP) mainly involve selecting polyethylene or polypropylene as the base resin and graft-modifying it to increase functional groups with adhesiveness, such as maleic anhydride grafts or acrylate grafts.

[0003] However, although the hot melt adhesives of the maleic anhydride graft or acrylate graft system have good connectivity with polyethylene or polypropylene, they mainly rely on their base resins. For currently existing hot melt adhesives, those with good bonding strength with polyethylene have poor bonding strength with polypropylene; those with good bonding strength with polypropylene have poor bonding strength with polyethylene.

[0004] Therefore, a hot melt adhesive is needed that can have excellent bonding strength with both PE and PP. Summary of the Invention

[0005] The technical objective of the present invention is to solve the problems in the background art and provide a high-temperature resistant hot melt adhesive specifically for bonding PP and PE.

[0006] The above technical objective of the present invention is achieved through the following technical solutions: A high-temperature resistant hot melt adhesive specifically for bonding PP and PE includes the following preparation process: Step S1: Functionalization OBC formulation design for the PE end layer of the hot melt adhesive: The raw materials for the PE end layer include olefin block copolymer OBC, maleic anhydride MAH, initiator, and functionalization modifier A; Step S2: Functionalization OBC formulation design for the PP end layer of the hot melt adhesive: The raw materials for the PP end layer include olefin block copolymer OBC, acrylic acid AA, initiator, and functionalization modifier B; Step S3: Extrusion of the PE end layer and PP end layer of the high-temperature resistant hot melt adhesive: The raw materials of Step S1 and Step S2 are co-extruded under specific processes respectively to obtain the high-temperature resistant hot melt adhesive specifically for bonding PP and PE, and a twin-screw extruder is used for the extruder.

[0007] Preferably, in the hot melt adhesive PE end layer formula of step S1, the initiator is dicumyl peroxide DCP, and the functional modifier A is glycidyl methacrylate GMA; Preferably, in the composition design of the hot melt adhesive PE end layer, the mass fraction of the initiator DCP is 0.3-1.0 parts, the mass fraction of maleic anhydride MAH is 3-8 parts, the mass fraction of the functional modifier A is 1-3 parts, and the rest is olefin block copolymer OBC, and the total mass fraction of the PE end layer is 100 parts.

[0008] The invention has the advantages that maleic anhydride MAH is a polar monomer containing anhydride groups, which is used for grafting and introducing carboxylic acid groups (-COOH), can improve the polarity of OBC, and enhance the compatibility with pipe raw materials; DCP is used as an initiator, which can induce the OBC molecular chain (PE / PP) to generate active sites, and promote the grafting of MAH and GMA; GMA is selected as the functional modifier A, and its epoxy group can react with the anhydride of MAH or the subsequent hydrolysis product (-COOH) to form a cross-linked network or a co-grafted structure, so that the grafting rate of MAH can be improved and the surface compatibility of the material can be improved.

[0009] Preferably, in the hot melt adhesive PP end layer formula of step S2, the initiator is dicumyl peroxide DCP, and the functional modifier B is divinylbenzene DVB; In the composition design of the hot melt adhesive PP end layer, the mass fraction of acrylic acid AA is 3-6 parts, the mass fraction of initiator DCP is 0.5-1 part, the mass fraction of functional modifier B is 0.3-1 part, the rest is olefin block copolymer OBC, and the total mass fraction of the PP end layer is 100 parts.

[0010] Furthermore, 0.1-0.3 parts of antioxidant can be added into the composition design of the hot melt adhesive PP end layer.

[0011] The advantage of the present invention is that acrylic acid AA is very suitable for grafting to PP segments (tertiary hydrocarbons of PP are more likely to generate free radicals), and its dosage is controlled to <1 wt% in combination with DVB to avoid excessive cross-linking and material embrittlement caused by excessive dosage; adding a proper amount of antioxidant can avoid degradation of PP segments caused by long-term high temperature exposure.

[0012] Preferably, the step S3 adopts segmented temperature control and gradient grafting melt grafting extrusion; the extrusion process adopts a co-rotating twin-screw extruder, which can realize multi-zone temperature control and is provided with a side feeding port.

[0013] Preferably, the PE end layer raw material extrusion process is as follows: The temperature in the feeding zone is controlled at 160 - 170 °C. After maleic anhydride and GMA are premixed, the OBC raw material is preliminarily pre - melted in the feeding zone; the temperature in the initiation reaction zone is controlled at 180 - 190 °C. After adding the DCP initiator in the initiation reaction zone, the maleic anhydride and GMA blend is fed into the side - feeding zone simultaneously; the temperature in the grafting reaction zone is controlled at 170 - 175 °C, the temperature in the exhaust zone is controlled at 160 °C, and the temperature in the cooling zone is controlled at 140 °C. After vacuum - removing unreacted monomers and by - products in the exhaust zone, it is cooled.

[0014] Preferably, the extrusion process of the PP end - layer raw material is as follows: The temperature in the feeding zone is 160 °C; the initiation reaction zone is a high - shear reaction zone with a temperature of 180 °C; the grafting reaction zone is at 170 °C; the exhaust zone is at 150 °C; the OBC raw material is fed in the feeding zone. After introducing the initiator in the initiation reaction zone, acrylic acid and divinylbenzene are fed through the side - feeding port and the functional grafting is completed in the grafting reaction zone.

[0015] Adopting the present invention, the advantages are as follows: By using the segmented temperature control and gradient grafting extrusion process of the above - mentioned PE end - layer and PP end - layer raw materials, through temperature zoning, the PE and PP chain segments are activated respectively to improve the grafting efficiency. In addition, it can also reduce the risk of thermal degradation of the PP chain segment and retain the mechanical properties of the material; by controlling the monomer concentration and reaction time, the functional groups form a concentration gradient in the OBC molecular chain or the material body to optimize the interfacial compatibility.

[0016] Preferably, the raw materials for the extrusion granulation of the hot - melt adhesive further include a chain extender, a dispersant, a plasticizer, a wetting agent, and a tackifying resin. The tackifying resin uses a bio - based tackifying resin; the temperature zoning and feeding process for the extrusion granulation of the hot - melt adhesive are as follows: Feeding zone: The temperature is controlled at 160 °C, and the above - mentioned functionalized OBC of the PE end - layer and PP end - layer is pre - melted in this zone; Reaction zone 1: The temperature is controlled at 175 - 185 °C, and the functionalized OBC of the PP end - layer reacts with the chain extender; Reaction zone 2: The temperature is controlled at 165 - 175 °C, and the functionalized OBC of the PE end - layer reacts with the chain extender; Side - feeding ports are respectively arranged in reaction zone 1 and reaction zone 2 to feed the bio - based tackifying resin and the plasticizer; Homogenization zone: The temperature is controlled at 160 - 170 °C, and the dispersant, the wetting agent, and the above - mentioned filler are put into this zone for uniform dispersion; Die head: The die - head temperature is controlled at 150 - 160 °C to ensure stable discharging; finally, the extruded product is cut and granulated to obtain the hot - melt adhesive.

[0017] Preferably, the chain extender uses an epoxy - functionalized acrylic copolymer, the dispersant uses a silane coupling agent KH550, the plasticizer uses a citrate ester, and the wetting agent uses a composition of sodium stearate and sodium dialkyl sulfate.

[0018] Preferably, in the hot melt adhesive, the mass fraction of the PP-end layer functionalized OBC is 25-35 parts, the mass fraction of the PE-end layer functionalized OBC is 35-45 parts, the chain extender is 0.1-1 part, the dispersant is 0.1-0.5 part, the plasticizer is 0.01-1 part, the wetting agent is 1-5 parts, and the rest is the bio-based tackifying resin.

[0019] Furthermore, in the application of a high-temperature resistant hot melt adhesive specifically for bonding PP and PE, PP-R and PE-RT are co-extruded in three layers synchronously with the hot melt adhesive compounding agent in the step S3, that is, the PE and PP pipes bonded by the hot melt adhesive are obtained.

[0020] Preferably, when the hot melt adhesive is used for bonding PP-R and PE-RT materials to prepare pipes, preferably the mass fraction of the hot melt adhesive is 40-60 parts, the mass fraction of the PP-R raw material is 30-50 parts, and the mass fraction of the PE-RT raw material is 10-15 parts.

[0021] Preferably, in the use of a high-temperature resistant hot melt adhesive specifically for bonding PP and PE, it is co-extruded in three layers with the PE-RY and PP-R special resins for pipes, and 1-5 parts of antioxidant are added during the extrusion process, that is, a high-strength heat-resistant product is obtained: The outer layer is a PP-R layer, and the extrusion parameters are 200 °C in the feeding zone, 230-240 °C in the melting zone, and 220 °C at the die head; The middle layer is a hot melt adhesive layer, and the extrusion parameters are 160 °C in the feeding zone, 170-180 °C in the melting zone, and 195 °C at the die head; The inner layer is a PE-RT layer, and the extrusion parameters are 180 °C in the feeding zone, 200-210 °C in the melting zone, and 165 °C at the die head.

[0022] Preferably, the ratio of the hot melt adhesive to PP and PE is adjusted and applied to the temperature-resistant and pressure-resistant composite pipes of plastic products with a multi-layer composite structure of an outer PP-R and an inner PE-RT. Adopting the present invention has the advantage that the subsequent process can also follow the segmented temperature control process, and can match the high-temperature processing window of PP-R and the medium-temperature processing window of PE-RT.

[0023] In summary, the present invention has the following beneficial effects: Dual-end functionalization design: The PE end introduces anhydride groups through grafting with maleic anhydride (MAH) to enhance the chemical bonding with PE-RT; the PP end introduces carboxylic acid groups through grafting with acrylic acid (AA), combines divinylbenzene (DVB) crosslinking and ZnO dynamic crosslinking agent to enhance the physical entanglement and heat resistance with PP-R; Gradient grafting and segmented temperature control process: The temperature of the twin-screw extruder is controlled in segments (170 - 190 °C for the PE end / 160 - 180 °C for the PP end), accurately activating the reaction sites of different chain segments to avoid degradation; Multi-layer co-extrusion compatibility: The melt viscosity of the hot melt adhesive intermediate layer is between PP-R and PE-RT. The interfacial bonding force is optimized synchronously through polar groups and chemical cross-linking, and the peel strength ≥ 4 N / mm; High temperature and pressure resistance performance: This special hot melt adhesive can ensure that the pipe does not show problems such as delamination and leakage during long-term pressure tests at normal temperature and 95 °C high temperature. Description of the drawings

[0024] Figure 1 Process flow chart of a high-temperature resistant hot melt adhesive dedicated to bonding PP and PE. Detailed implementation manners

[0025] The following specific embodiments are only explanations of the present invention and are not limitations thereof. Those skilled in the art can make modifications without creative contributions to the embodiments according to needs after reading this specification, but as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

[0026] Example 1

[0027] Functionalized OBC formulation design for the PE end layer of the hot melt adhesive: The mass fraction of initiator DCP is 0.3 parts, the mass fraction of maleic anhydride MAH is 3 parts, the mass fraction of functionalized modifier A is 1 part, and the rest is olefin block copolymer OBC.

[0028] Functionalized OBC formulation design for the PP end layer of the hot melt adhesive: The mass fraction of acrylic acid AA is 3 parts, the mass fraction of initiator DCP is 0.5 parts, the mass fraction of functionalized modifier B is 0.3 parts, and 0.1 part of antioxidant is further added. The rest is olefin block copolymer OBC, and the total mass fraction of the PP end layer is 100 parts.

[0029] In step S3, during the extrusion of the PE end layer and PP end layer of the high-temperature resistant hot melt adhesive, The extrusion process parameters of the PE end layer are: The temperature of the feeding zone is controlled at 160 °C. After premixing maleic anhydride and GMA, the OBC raw material is preliminarily pre-melted in the feeding zone; the temperature of the initiation reaction zone is controlled at 180 °C. After adding the DCP initiator in the initiation reaction zone, the maleic anhydride and GMA blend is fed into the side feeding zone at the same time; the temperature of the grafting reaction zone is controlled at 170 °C, the temperature of the exhaust zone is controlled at 160 °C, and the temperature of the cooling zone is controlled at 140 °C. After vacuum removing the unreacted monomers and by-products in the exhaust zone, it is cooled.

[0030] The extrusion process parameters of the PP end layer are: The temperature in the feeding zone is 160°C; the initiation reaction zone is a high-shear reaction zone with a temperature of 180°C; the grafting reaction zone is at 170°C; the exhaust zone is at 150°C; the OBC raw material is introduced in the feeding zone. After introducing the initiator in the initiation reaction zone, acrylic acid and divinylbenzene are fed through the side feeding port, and functionalized grafting is completed in the grafting reaction zone.

[0031] Step S4 Extrusion granulation of the hot melt adhesive: In the hot melt adhesive, the mass fraction of the PP end-layer functionalized OBC is 25 - parts, the mass fraction of the PE end-layer functionalized OBC is 35 parts, 0.1 part of chain extender, 0.1 part of dispersant, 0.01 part of plasticizer, 1 part of wetting agent, and the rest is bio-based tackifying resin; the extrusion process parameters of the hot melt adhesive are as follows: Reaction zone 1: The temperature is controlled at 175°C, and the PP end-layer functionalized OBC reacts with the chain extender; Reaction zone 2: The temperature is controlled at 165°C, and the PE end-layer functionalized OBC reacts with the chain extender; Side feeding ports are respectively arranged in reaction zone 1 and reaction zone 2 to feed the bio-based tackifying resin and the plasticizer. Homogenization zone: The temperature is controlled at 160°C, and the dispersant, wetting agent and the above-mentioned fillers are put into this zone for uniform dispersion; Die head: The die head temperature is controlled at 150°C to ensure stable discharging; Finally, the extruded product is cut and granulated to obtain the hot melt adhesive.

[0032] Example 2 Formulation design of the PE end-layer functionalized OBC of the hot melt adhesive: The mass fraction of the initiator DCP is 1.0 part, the mass fraction of maleic anhydride MAH is 8 parts, the mass fraction of the functionalization modifier A is 3 parts, and the rest is olefin block copolymer OBC.

[0033] Formulation design of the PP end-layer functionalized OBC of the hot melt adhesive: The mass fraction of acrylic acid AA is 6 parts, the mass fraction of the initiator DCP is 1 part, the mass fraction of the functionalization modifier B is 1 part, and 0.3 part of antioxidant is further added. The rest is olefin block copolymer OBC, and the total mass fraction of the PP end-layer is 100 parts.

[0034] In step S3, during the extrusion of the high-temperature resistant hot melt adhesive for the PE end-layer and the PP end-layer, The extrusion process parameters of the PE end-layer are as follows: The temperature in the feeding zone is controlled at 170°C. After premixing maleic anhydride and GMA, the OBC raw material is preliminarily pre-melted in the feeding zone; the temperature in the initiation reaction zone is controlled at 190°C. After putting the DCP initiator into the initiation reaction zone, the blend of maleic anhydride and GMA is fed into the side feeding zone at the same time; the temperature in the grafting reaction zone is controlled at 175°C, the temperature in the exhaust zone is controlled at 160°C, and the temperature in the cooling zone is controlled at 140°C. After vacuum removing the unreacted monomers and by-products in the exhaust zone, it is cooled.

[0035] The extrusion process parameters of the PP end layer are as follows: The temperature of the feeding zone is 160 °C; the initiation reaction zone is a high-shear reaction zone with a temperature of 180 °C; the grafting reaction zone is 170 °C; the exhaust zone is 150 °C; the OBC raw material is fed into the feeding zone, and after introducing the initiator in the initiation reaction zone, acrylic acid and divinylbenzene are fed through the side feeding port, and the functional grafting is completed in the grafting reaction zone.

[0036] Step S4: Extrusion granulation of the hot melt adhesive: In the hot melt adhesive, the mass fraction of the functionalized OBC in the PP end layer is 35 parts, the mass fraction of the functionalized OBC in the PE end layer is 45 parts, 1 part of chain extender, 0.5 part of dispersant, 1 part of plasticizer, 5 parts of wetting agent, and the rest is bio-based tackifying resin; the extrusion process parameters of the hot melt adhesive are as follows: Reaction zone 1: The temperature is controlled at 185 °C, and the functionalized OBC in the PP end layer reacts with the chain extender; Reaction zone 2: The temperature is controlled at 175 °C, and the functionalized OBC in the PE end layer reacts with the chain extender; Side feeding ports are respectively arranged in reaction zone 1 and reaction zone 2 to feed the bio-based tackifying resin and plasticizer; Homogenization zone: The temperature is controlled at 170 °C, and the dispersant, wetting agent and the above fillers are put into this zone and evenly dispersed; Die head: The temperature of the die head is controlled at 160 °C to ensure stable discharging; finally, the extruded product is cut and granulated to obtain the hot melt adhesive.

[0037] Example 3 Formulation design of the functionalized OBC in the PE end layer of the hot melt adhesive: The mass fraction of the initiator DCP is 0.3 part, the mass fraction of maleic anhydride MAH is 3 parts, the mass fraction of the functionalization modifier A is 1 part, and the rest is the olefin block copolymer OBC.

[0038] Formulation design of the functionalized OBC in the PP end layer of the hot melt adhesive: The mass fraction of acrylic acid AA is 6 parts, the mass fraction of the initiator DCP is 1 part, the mass fraction of the functionalization modifier B is 1 part, and 0.3 part of antioxidant is further added, and the rest is the olefin block copolymer OBC, and the total mass fraction of the PP end layer is 100 parts.

[0039] In step S3, during the extrusion of the high-temperature resistant hot melt adhesive for the PE end layer and the PP end layer, The extrusion process parameters of the PE end layer are as follows: The temperature of the feeding zone is controlled at 160 °C. After premixing maleic anhydride and GMA, the OBC raw material is preliminarily pre-melted in the feeding zone; the temperature of the initiation reaction zone is controlled at 180 °C. After putting the DCP initiator into the initiation reaction zone, the maleic anhydride and GMA blend is fed into the side feeding zone at the same time; the temperature of the grafting reaction zone is controlled at 170 °C, the temperature of the exhaust zone is controlled at 160 °C, and the temperature of the cooling zone is controlled at 140 °C. After vacuum removing the unreacted monomers and by-products in the exhaust zone, it is cooled.

[0040] The extrusion process parameters of the PP end layer are as follows: The temperature of the feeding zone is 160 °C; the initiation reaction zone is a high-shear reaction zone with a temperature of 180 °C; the grafting reaction zone is 170 °C; the exhaust zone is 150 °C; the OBC raw material is fed into the feeding zone, and after introducing the initiator in the initiation reaction zone, acrylic acid and divinylbenzene are fed through the side feeding port, and the functional grafting is completed in the grafting reaction zone.

[0041] Step S4: Extrusion granulation of the hot melt adhesive: In the hot melt adhesive, the mass fraction of the functionalized OBC in the PP end layer is 25 parts, the mass fraction of the functionalized OBC in the PE end layer is 35 parts, 0.1 part of the chain extender, 0.1 part of the dispersant, 0.01 part of the plasticizer, 1 part of the wetting agent, and the rest is the bio-based tackifying resin; the extrusion process parameters of the hot melt adhesive are as follows: Reaction zone 1: The temperature is controlled at 175 °C, and the functionalized OBC in the PP end layer reacts with the chain extender; Reaction zone 2: The temperature is controlled at 170 °C, and the functionalized OBC in the PE end layer reacts with the chain extender; Side feeding ports are respectively arranged in reaction zone 1 and reaction zone 2 to feed the bio-based tackifying resin and the plasticizer; Homogenization zone: The temperature is controlled at 160 °C, and the dispersant, the wetting agent and the above-mentioned fillers are put into this zone for uniform dispersion; Die head: The temperature of the die head is controlled at 150 °C to ensure stable discharging; finally, the extruded product is cut and granulated to obtain the hot melt adhesive.

[0042] Example 4

[0043] Formulation design of the functionalized OBC in the PE end layer of the hot melt adhesive: The mass fraction of the initiator DCP is 1.0 part, the mass fraction of maleic anhydride MAH is 8 parts, the mass fraction of the functionalized modifier A is 3 parts, and the rest is the olefin block copolymer OBC.

[0044] Formulation design of the functionalized OBC in the PP end layer of the hot melt adhesive: The mass fraction of acrylic acid AA is 3 parts, the mass fraction of the initiator DCP is 0.5 part, the mass fraction of the functionalized modifier B is 0.3 part, and 0.1 part of antioxidant is further added. The rest is the olefin block copolymer OBC, and the total mass fraction of the PP end layer is 100 parts.

[0045] In step S3, during the extrusion of the high-temperature resistant hot melt adhesive PE end layer and PP end layer, The extrusion process parameters of the PE end layer are as follows: The temperature of the feeding zone is controlled at 170 °C. After maleic anhydride and GMA are premixed, the OBC raw material is preliminarily pre-melted in the feeding zone; the temperature of the initiation reaction zone is controlled at 190 °C. After adding the DCP initiator in the initiation reaction zone, the maleic anhydride and GMA blend is fed into the side feeding zone at the same time; the temperature of the grafting reaction zone is controlled at 175 °C, the temperature of the exhaust zone is controlled at 160 °C, and the temperature of the cooling zone is controlled at 140 °C. After the unreacted monomers and by-products are removed by vacuum in the exhaust zone, it is cooled.

[0046] The extrusion process parameters of the PP end layer are as follows: The temperature of the feeding zone is 160 °C; the initiation reaction zone is a high-shear reaction zone with a temperature of 180 °C; the grafting reaction zone is 170 °C; the exhaust zone is 150 °C; the OBC raw material is fed into the feeding zone. After introducing the initiator in the initiation reaction zone, acrylic acid and divinylbenzene are fed through the side feeding port and the functionalized grafting is completed in the grafting reaction zone.

[0047] Step S4 Extrusion granulation of the hot melt adhesive: In the hot melt adhesive, the mass fraction of the functionalized OBC of the PP end layer is 35 parts, the mass fraction of the functionalized OBC of the PE end layer is 45 parts, 1 part of chain extender, 0.5 part of dispersant, 1 part of plasticizer, 5 parts of wetting agent, and the rest is bio-based tackifying resin; the extrusion process parameters of the hot melt adhesive are as follows: Reaction zone 1: The temperature is controlled at 185 °C, and the functionalized OBC of the PP end layer reacts with the chain extender; Reaction zone 2: The temperature is controlled at 175 °C, and the functionalized OBC of the PE end layer reacts with the chain extender; Side feeding ports are respectively arranged in reaction zone 1 and reaction zone 2 to feed bio-based tackifying resin and plasticizer; Homogenization zone: The temperature is controlled at 170 °C, and the dispersant, wetting agent and the above fillers are put into this zone and uniformly dispersed; Die head: The temperature of the die head is controlled at 160 °C to ensure stable discharging; Finally, the extruded product is cut and granulated to obtain the hot melt adhesive.

[0048] Example 5

[0049] Formulation design of the functionalized OBC of the PE end layer of the hot melt adhesive: The mass fraction of the initiator DCP is 0.5 part, the mass fraction of maleic anhydride MAH is 5 parts, the mass fraction of the functionalized modifier A is 1.9 parts, and the rest is olefin block copolymer OBC.

[0050] Formulation design of the functionalized OBC of the PP end layer of the hot melt adhesive: The mass fraction of acrylic acid AA is 5 parts, the mass fraction of the initiator DCP is 0.8 part, the mass fraction of the functionalized modifier B is 0.4 part, and 0.2 part of antioxidant is further added. The rest is olefin block copolymer OBC, and the total mass fraction of the PP end layer is 100 parts.

[0051] In step S3, during the extrusion of the high-temperature resistant hot melt adhesive PE end layer and PP end layer, The extrusion process parameters of the PE end layer are as follows: The temperature of the feeding zone is controlled at 165°C. After maleic anhydride and GMA are premixed, the OBC raw material is preliminarily pre-melted in the feeding zone; the temperature of the initiation reaction zone is controlled at 185°C. After adding the DCP initiator in the initiation reaction zone, the maleic anhydride and GMA blend are fed into the side feeding zone at the same time; the temperature of the grafting reaction zone is controlled at 175°C, the temperature of the exhaust zone is controlled at 160°C, and the temperature of the cooling zone is controlled at 140°C. After the unreacted monomers and by-products are removed by vacuum in the exhaust zone, it is cooled.

[0052] The extrusion process parameters of the PP end layer are as follows: The temperature of the feeding zone is 160°C; the initiation reaction zone is a high-shear reaction zone with a temperature of 180°C; the grafting reaction zone is 170°C; the exhaust zone is 150°C; the OBC raw material is fed into the feeding zone. After introducing the initiator in the initiation reaction zone, acrylic acid and divinylbenzene are fed through the side feeding port and the functionalized grafting is completed in the grafting reaction zone.

[0053] Step S4: Extrusion granulation of the hot melt adhesive: In the hot melt adhesive, the mass fraction of the functionalized OBC in the PP end layer is 35 parts, the mass fraction of the functionalized OBC in the PE end layer is 35 parts, 1 part of chain extender, 0.5 part of dispersant, 0.01 part of plasticizer, 3 parts of wetting agent, and the rest is bio-based tackifying resin; the extrusion process parameters of the hot melt adhesive are as follows: Reaction zone 1: The temperature is controlled at 185°C, and the functionalized OBC in the PP end layer reacts with the chain extender; Reaction zone 2: The temperature is controlled at 175°C, and the functionalized OBC in the PE end layer reacts with the chain extender; Side feeding ports are respectively arranged in reaction zone 1 and reaction zone 2 to feed the bio-based tackifying resin and plasticizer; Homogenization zone: The temperature is controlled at 170°C, and the dispersant, wetting agent and the above fillers are put into this zone and evenly dispersed; Die head: The temperature of the die head is controlled at 160°C to ensure stable discharging; Finally, the extruded product is cut and granulated to obtain the hot melt adhesive.

[0054] Example 6

[0055] Formulation design of the functionalized OBC in the PE end layer of the hot melt adhesive: The mass fraction of the initiator DCP is 0.5 part, the mass fraction of maleic anhydride MAH is 5 parts, the mass fraction of the functionalized modifier A is 1.9 parts, and the rest is olefin block copolymer OBC.

[0056] Formulation design of the functionalized OBC in the PP end layer of the hot melt adhesive: The mass fraction of acrylic acid AA is 5 parts, the mass fraction of the initiator DCP is 0.8 part, the mass fraction of the functionalized modifier B is 0.4 part, and 0.2 part of antioxidant is further added. The rest is olefin block copolymer OBC, and the total mass fraction of the PP end layer is 100 parts.

[0057] In step S3, during the extrusion of the high-temperature resistant hot melt adhesive's PE layer and PP layer, The extrusion process parameters of the PE layer are as follows: The temperature of the feeding zone is controlled at 165°C. After premixing maleic anhydride and GMA, the OBC raw material is preliminarily pre-melted in the feeding zone; the temperature of the initiation reaction zone is controlled at 185°C. After adding the DCP initiator in the initiation reaction zone, the maleic anhydride and GMA blend is fed into the side feeding zone simultaneously; the temperature of the grafting reaction zone is controlled at 175°C, the temperature of the exhaust zone is controlled at 160°C, and the temperature of the cooling zone is controlled at 140°C. After vacuum removing unreacted monomers and by-products in the exhaust zone, it is cooled.

[0058] The extrusion process parameters of the PP layer are as follows: The temperature of the feeding zone is 160°C; the initiation reaction zone is a high-shear reaction zone with a temperature of 180°C; the grafting reaction zone is 170°C; the exhaust zone is 150°C; the OBC raw material is fed into the feeding zone. After introducing the initiator in the initiation reaction zone, acrylic acid and divinylbenzene are fed through the side feeding port, and functionalized grafting is completed in the grafting reaction zone.

[0059] In step S4, extrusion granulation of the hot melt adhesive: In the hot melt adhesive, the mass fraction of functionalized OBC in the PP layer is 28 parts, the mass fraction of functionalized OBC in the PE layer is 40 parts, 0.8 part of chain extender, 0.4 part of dispersant, 0.5 part of plasticizer, 2 parts of wetting agent, and the rest is bio-based tackifying resin; the extrusion process parameters of the hot melt adhesive are as follows: Reaction zone 1: The temperature is controlled at 175°C, and the functionalized OBC in the PP layer reacts with the chain extender; Reaction zone 2: The temperature is controlled at 175°C, and the functionalized OBC in the PE layer reacts with the chain extender; Side feeding ports are respectively arranged in reaction zone 1 and reaction zone 2 to feed bio-based tackifying resin and plasticizer; Homogenization zone: The temperature is controlled at 170°C, and the dispersant, wetting agent, and the above fillers are put into this zone for uniform dispersion; Die head: The die head temperature is controlled at 160°C to ensure stable discharging; Finally, the extruded product is cut and granulated to obtain the hot melt adhesive.

[0060] Example 7

[0061] Formulation design of functionalized OBC in the PE layer of the hot melt adhesive: The mass fraction of the initiator DCP is 0.5 part, the mass fraction of maleic anhydride MAH is 5 parts, the mass fraction of functionalized modifier A is 1.9 parts, and the rest is olefin block copolymer OBC.

[0062] Functionalized OBC Formulation Design for the PP Layer of Hot Melt Adhesive: The mass fraction of acrylic acid AA is 5 parts, the mass fraction of initiator DCP is 0.8 parts, the mass fraction of functionalized modifier B is 0.4 parts, and 0.2 parts of antioxidant are further added. The rest is olefin block copolymer OBC, and the total mass fraction of the PP layer is 100 parts.

[0063] In step S3, during the extrusion of the high-temperature resistant hot melt adhesive PE layer and PP layer, The extrusion process parameters of the PE layer are: The temperature of the feeding zone is controlled at 165°C. After maleic anhydride and GMA are premixed, the OBC raw material is preliminarily pre-melted in the feeding zone; the temperature of the initiation reaction zone is controlled at 185°C. After the DCP initiator is added in the initiation reaction zone, the maleic anhydride and GMA blend are fed into the side feeding zone at the same time; the temperature of the grafting reaction zone is controlled at 175°C, the temperature of the exhaust zone is controlled at 160°C, and the temperature of the cooling zone is controlled at 140°C. After the unreacted monomers and by-products are removed by vacuum in the exhaust zone, it is cooled.

[0064] The extrusion process parameters of the PP layer are: The temperature of the feeding zone is 160°C; the initiation reaction zone is a high-shear reaction zone with a temperature of 180°C; the grafting reaction zone is 170°C; the exhaust zone is 150°C; the OBC raw material is fed into the feeding zone, and after the initiator is introduced into the initiation reaction zone, acrylic acid and divinylbenzene are fed through the side feeding port, and the functionalized grafting is completed in the grafting reaction zone.

[0065] Step S4 Extrusion Granulation of Hot Melt Adhesive: In the hot melt adhesive, the mass fraction of functionalized OBC of the PP layer is 30 parts, the mass fraction of functionalized OBC of the PE layer is 39 parts, 0.6 parts of chain extender, 0.25 parts of dispersant, 0.63 parts of plasticizer, 2.8 parts of wetting agent, and the rest is bio-based tackifying resin; the extrusion process parameters of the hot melt adhesive are: Reaction zone 1: The temperature is controlled at 180°C, and the functionalized OBC of the PP layer reacts with the chain extender; Reaction zone 2: The temperature is controlled at 170°C, and the functionalized OBC of the PE layer reacts with the chain extender; Side feeding ports are respectively arranged in reaction zone 1 and reaction zone 2 to feed bio-based tackifying resin and plasticizer; Homogenization zone: The temperature is controlled at 165°C, and the dispersant, wetting agent and the above fillers are put into this zone for uniform dispersion; Die head: The die head temperature is controlled at 155°C to ensure stable discharging; Finally, the extruded product is cut into granules to obtain the hot melt adhesive.

[0066] Comparative Example 1 Common ordinary OBC hot melt adhesive on the market.

[0067] Comparative Example 2

[0068] Different from the above-mentioned Embodiment 7, in this comparative example, the component design at the PE end is removed.

[0069] Comparative Example 3

[0070] Different from the above-mentioned Embodiment 7, in this comparative example, the component design at the PP end is removed.

[0071] For the hot melt adhesives prepared in the above-mentioned Embodiments 1-7 and Comparative Examples 1-3, with the extrusion process: The mass fraction of the hot melt adhesive is 50 parts, the mass fraction of the PP-R raw material is 40 parts, and the mass fraction of the PE-RT raw material is 10 parts; The outer layer is a PP-R layer, and the extrusion parameters are 200 °C in the feeding zone, 235 °C in the melting zone, and 220 °C at the die head; the middle layer is a hot melt adhesive layer, and the extrusion parameters are 160 °C in the feeding zone, 175 °C in the melting zone, and 195 °C at the die head; the inner layer is a PE-RT layer, and the extrusion parameters are 180 °C in the feeding zone, 205 °C in the melting zone, and 165 °C at the die head.

[0072] By respectively testing their long-term tests under the hydrostatic test at 95 °C (stop when delamination or leakage starts to occur); in addition, test the peel strength and temperature resistance (i.e., the temperature at which the product starts to soften) of the extruded bonding of PP and PE pipes.

[0073] The test results of Embodiments 1-7 and Comparative Examples 1-3 are shown in Table 1 below: Table 1 Test and Detection Results

[0074] It can be seen from the table that: In the data results of Embodiments 1-4, since the extreme values of the process parameters are all adopted and the parameters are not appropriate, the hot melt adhesives prepared therefrom have worse bonding properties to PP and PE, material temperature resistance, and pressure test results than those of Embodiments 5-7; In Embodiment 5, the process parameters of the two end layers are optimized. On this basis, the product performance of the hot melt adhesive prepared therefrom is better than that of Embodiments 1-4. However, compared with the subsequent embodiments, it can be concluded that the formulation and process parameter design of the hot melt adhesive still need to be optimized; Compared with Embodiments 6-7, the functionalized modified hot melt adhesive prepared under the process conditions of Embodiment 7 has the best bonding properties to PP and PE among them, can reach 160 °C in the temperature resistance test, and can last for more than 5000 h without delamination or leakage in the 95 °C pressure test.

[0075] Compared with Comparative Examples 2-3, in the above embodiments, since Comparative Example 2 and Comparative Example 3 did not adopt the end-layer raw material process design of PP and PE respectively, and the process of segmented temperature control and gradient grafting was not adopted during preparation, the hot melt adhesives prepared in Comparative Examples 2-3 are far inferior to the embodiments in terms of adhesiveness, heat resistance, and pressure resistance; Comparative Example 1 used an ordinary OBC hot melt adhesive without any processing and modification for bonding, and the performance obtained was the worst. It can be concluded that the hot melt adhesive of the present invention is significantly superior to the traditional scheme in terms of the double-phase bonding strength of PP / PE, high temperature resistance, and process compatibility, and is suitable for the manufacture of composite pipes under harsh working conditions.

Claims

1. A high-temperature resistant hot melt adhesive specifically for bonding PP and PE, characterized in that, It includes the following preparation processes: Step S1: Functionalized OBC formulation design for the PE end layer of the hot melt adhesive: The raw materials for the PE end layer include olefin block copolymer OBC, maleic anhydride MAH, initiator, and functionalized modifier A; Step S2: Functionalized OBC formulation design for the PP end layer of the hot melt adhesive: The raw materials for the PP end layer include olefin block copolymer OBC, acrylic acid AA, initiator, and functionalized modifier B; Step S3: Extrusion of the PE end layer and PP end layer of the high-temperature resistant hot melt adhesive: The raw materials in Step S1 and Step S2 are co-extruded under specific processes respectively to obtain a kind of high-temperature resistant hot melt adhesive dedicated to bonding PP and PE. The extruder used is a twin-screw extruder.

2. The high-temperature resistant hot melt adhesive specifically for bonding PP and PE according to claim 1, characterized in that, In the formulation of the PE end layer of the hot melt adhesive in Step S1, the initiator used is dicumyl peroxide DCP, and the functionalized modifier A is glycidyl methacrylate GMA; In the composition design of the PE end layer of the hot melt adhesive, the mass fraction of the initiator DCP is 0.3 - 1.0 parts, the mass fraction of maleic anhydride MAH is 3 - 8 parts, the mass fraction of the functionalized modifier A is 1 - 3 parts, and the rest is olefin block copolymer OBC, and the total mass fraction of the PE end layer is 100 parts.

3. A high-temperature resistant hot melt adhesive specifically for bonding PP and PE according to claim 1, characterized in that, In the formulation of the PP end layer of the hot melt adhesive in Step S2, the initiator is dicumyl peroxide DCP, and the functionalized modifier B uses divinylbenzene DVB; In the composition design of the PP end layer of the hot melt adhesive, the mass fraction of acrylic acid AA is 3 - 6 parts, the mass fraction of the initiator DCP is 0.5 - 1 part, the mass fraction of the functionalized modifier B is 0.3 - 1 part, 0.1 - 0.3 parts of antioxidant can be further added, and the rest is olefin block copolymer OBC, and the total mass fraction of the PP end layer is 100 parts.

4. A high-temperature resistant hot melt adhesive specifically for bonding PP and PE according to claim 1, characterized in that, Step S3 adopts segmented temperature control and gradient grafting melt grafting extrusion; The extrusion process uses a multi-zone temperature control of a co-rotating twin-screw extruder and is equipped with a side feeding port.

5. A high temperature resistant hot melt adhesive specifically for bonding PP and PE according to claim 4, characterized in that, The extrusion process of the raw materials for the PE end layer is as follows: The temperature of the feeding zone is controlled at 160 - 170 °C. After pre-mixing maleic anhydride and GMA, the OBC raw materials are preliminarily pre-melted in the feeding zone; The temperature of the initiation reaction zone is controlled at 180 - 190 °C. After adding the DCP initiator in the initiation reaction zone, the mixture of maleic anhydride and GMA is fed into the side feeding zone at the same time; The temperature of the grafting reaction zone is controlled at 170 - 175 °C, the temperature of the exhaust zone is controlled at 160 °C, and the temperature of the cooling zone is controlled at 140 °C. After vacuum removing unreacted monomers and by-products in the exhaust zone, it is cooled.

6. A high-temperature resistant hot melt adhesive specifically for bonding PP and PE according to claim 4, characterized in that, The extrusion process of the raw materials for the PP end layer is as follows: The temperature of the feeding zone is 160 °C; The initiation reaction zone is a high-shear reaction zone with a temperature of 180 °C; The grafting reaction zone is at 170 °C; The exhaust zone is at 150 °C; The OBC raw materials are fed into the feeding zone, the initiator is introduced in the initiation reaction zone, and acrylic acid and divinylbenzene are fed through the side feeding port, and functionalized grafting is completed in the grafting reaction zone.

7. A high-temperature resistant hot melt adhesive specifically for bonding PP and PE according to claim 1, characterized in that, The raw materials for the extrusion granulation of the hot melt adhesive also include chain extender, dispersant, plasticizer, wetting agent, and tackifying resin. The tackifying resin uses bio-based tackifying resin; The temperature zoning and feeding process for the extrusion granulation of the hot melt adhesive are: Reaction zone 1: The temperature is controlled at 175 - 185 °C, and the PP-end functionalized OBC reacts with the chain extender; Reaction zone 2: The temperature is controlled at 165 - 175 °C, and the PE-end functionalized OBC reacts with the chain extender; Side feed ports are respectively arranged in reaction zone 1 and reaction zone 2 to feed in the bio-based tackifying resin and the plasticizer; Homogenization zone: The temperature is controlled at 160 - 170 °C, and the dispersant, wetting agent and the above-mentioned fillers are put into this zone for uniform dispersion; Die head: The die head temperature is controlled at 150 - 160 °C to ensure stable discharging; Finally, the extruded product is cut into pellets to obtain the hot melt adhesive.

8. A high-temperature resistant hot melt adhesive for bonding PP and PE according to claim 7, characterized in that, The chain extender uses an epoxy-functionalized acrylic copolymer, the dispersant uses a silane coupling agent KH550, the plasticizer uses a citrate ester, and the wetting agent uses a composition of sodium stearate and sodium dialkyl sulfate; In the hot melt adhesive, the mass fraction of the PP-end functionalized OBC is 25 - 35 parts, the mass fraction of the PE-end functionalized OBC is 35 - 45 parts, the chain extender is 0.1 - 1 part, the dispersant is 0.1 - 0.5 part, the plasticizer is 0.01 - 1 part, the wetting agent is 1 - 5 parts, and the rest is the bio-based tackifying resin.

9. Application of a high-temperature resistant hot melt adhesive for bonding PP and PE, characterized in that, In the application of the special high-temperature resistant hot melt adhesive for bonding PP and PE, PP-R and PE-RT are co-extruded in three layers synchronously with the auxiliary agent of the hot melt adhesive in step S3, that is, the PE and PP pipes bonded with the hot melt adhesive are obtained; When the hot melt adhesive is used for bonding materials of PP-R and PE-RT to prepare pipes, preferably, the mass fraction of the hot melt adhesive is 40 - 60 parts, the mass fraction of the PP-R raw material is 30 - 50 parts, and the mass fraction of the PE-RT raw material is 10 - 15 parts.

10. The application of a high-temperature resistant hot melt adhesive for bonding PP and PE according to claim 9, characterized in that, The hot melt adhesive is co-extruded in three layers with the PE-RY and PP-R special resins for pipes, and 1 - 5 parts of antioxidant are added during the extrusion process, that is, a high-strength heat-resistant product is obtained: The outer layer is a PP-R layer, and the extrusion parameters are: the feeding zone is 200 °C, the melting zone is 230 - 240 °C, and the die head is 220 °C; The middle layer is a hot melt adhesive layer, and the extrusion parameters are: the feeding zone is 160 °C, the melting zone is 170 - 180 °C, and the die head is 195 °C; The inner layer is a PE-RT layer, and the extrusion parameters are: the feeding zone is 180 °C, the melting zone is 200 - 210 °C, and the die head is 165 °C; Adjust the ratio of the hot melt adhesive to PP and PE, and apply it to the production of high-temperature and high-pressure composite pipes of plastic products with a multi-layer composite structure of outer PP-R and inner PE-RT.

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