A maleic anhydride grafted adhesive resin for PPR / PA composite pipe and a preparation method thereof

Abstract

The application discloses a maleic anhydride grafted adhesive resin for PPR / PA composite pipes and a preparation method thereof. The adhesive resin comprises a base polyolefin resin, maleic anhydride, an initiator, a grafting efficiency promoter, a side reaction inhibitor, a long-acting antioxidant, a lubricant and a water-resistant agent. The base polyolefin resin comprises at least one of random copolymerized polypropylene PPR, block copolymerized polypropylene PP-B and linear low-density polyethylene LLDPE. The grafting efficiency promoter is at least one of triallyl isocyanurate TAIC, trimethylolpropane trimethacrylate TMPTMA and divinylbenzene DVB. The side reaction inhibitor adopts a compound system of a hindered phenol antioxidant and a phosphite antioxidant. The application can solve the technical problems of insufficient bonding strength, poor high-temperature aging resistance and water resistance, poor processing thermal stability and insufficient base material adaptability when the adhesive resin is used for PPR / PA12 composite.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a maleic anhydride grafting adhesive resin for PPR / PA composite pipes and its preparation method, which is particularly suitable for the intermediate bonding layer of PPR / PA12 building water supply pipes. Background Technology

[0002] In multilayer composite pipes with different substrates, the bonding resin is the core to ensure the stability of the interlayer bond. PPR / PA12 composite pipes have attracted much attention due to their heat resistance, convenient hot-melt socketing, and excellent low-temperature toughness. However, PPR pipes and PA12 pipes have differences in molecular polarity and functional group reactivity, resulting in a lack of effective intermolecular forces at the interface. When directly composited, the bonding force is weak, and the melt flow is greatly different. Co-extrusion molding can easily cause uneven distribution of interlayer shear force, making them prone to delamination failure under thermal cycling or pressure.

[0003] To address the aforementioned compatibility issues, maleic anhydride-grafted polyolefins are commonly used as adhesive resins in industry. However, existing maleic anhydride-grafted polyolefin adhesive resins are mostly developed for PP / PA6 or PE / PA66 composite pipe systems. For PPR / PA12 composite pipe systems, due to the differences in melt flow characteristics and crystallization behavior between PPR and homopolymer PP, and the differences in end-group activity and hygroscopicity between PA12 and PA6, the general-purpose adhesive resins used in existing technologies often exhibit poor high-temperature aging resistance, water resistance, and bonding performance.

[0004] Meanwhile, most existing adhesive resins use melt grafting (reactive extrusion at 180-220℃). Although solvent-free and highly continuous, during the high-temperature melting process, in addition to the target grafting reaction, there is also β-chain scission degradation and cross-linking reaction of polyolefins. At processing temperatures above 230℃, the grafted maleic anhydride groups are prone to degrafting reaction or thermal degradation, resulting in reduced chemical reactivity with PA12. Summary of the Invention

[0005] In view of the technical defects of existing maleic anhydride grafted adhesive resins when used for PPR and PA12 composites, such as insufficient bonding strength, poor high-temperature aging resistance and water resistance, poor processing thermal stability, and insufficient substrate compatibility, the purpose of this invention is to provide a maleic anhydride grafted adhesive resin for PPR / PA composite pipes and its preparation method.

[0006] The design concept solved by this invention includes: (1) To address the technical problem that PA12 has a low content of terminal amino groups and insufficient reactive sites compared to PA6 or PA66, a high grafting rate (1.2-1.6%) was designed and a multifunctional synergistic promoter was introduced to improve grafting efficiency. (2) The co-extrusion temperature of PPR-PA12 composite pipe needs to be 220-240℃, but the grafted groups of existing adhesive resins are prone to degrafting above 230℃. Moreover, when PPR is used as the adhesive resin matrix, the vinyl side chains in PPR molecules are prone to β-chain scission degradation, resulting in a decrease in grafting rate and melt strength during processing. By introducing a selective β-chain scission inhibitor to capture PPR macromolecular free radicals and inhibit degradation, and at the same time compounding a high molecular weight antioxidant with phosphite to form a synergistic stabilizing system, the chemical stability of the grafted groups at high temperatures is protected.

[0007] (3) By optimizing the consistency between the grafted matrix and the outer layer material of PPR, the interfacial stress is reduced. Combined with a high grafting rate, full chemical bonding is ensured, so that the interlayer bonding strength exceeds the PA12 body strength. The failure mode of the adhesive resin is changed to cohesive failure rather than interfacial separation, thus eliminating the risk of substrate delamination failure.

[0008] Through the synergistic effect of the above technical approaches, this invention achieves a good interface match between the special adhesive resin and the PPR outer layer and PA12 inner layer, meeting the requirements of high temperature aging resistance, water resistance, and long-term reliability for building water supply pipelines.

[0009] The technical solution adopted in this invention is as follows: A maleic anhydride grafting adhesive for PPR / PA composite pipes comprises, by weight, the following components: 100 parts of base polyolefin resin, 1.5-4.0 parts of maleic anhydride (MAH), 0.1-0.5 parts of initiator, 0.5-2.0 parts of grafting efficiency promoter, 0.3-1.5 parts of side reaction inhibitor, 0.2-1.0 parts of long-lasting antioxidant, 0.1-0.5 parts of lubricant, and 0.5-1.0 parts of water-resistant agent.

[0010] Further, by weight, it includes the following components: 100 parts of base polyolefin resin, 2.0-3.0 parts of maleic anhydride (MAH), 0.15-0.3 parts of initiator, 0.8-1.5 parts of grafting efficiency promoter, 0.5-1.0 parts of side reaction inhibitor, 0.3-0.6 parts of long-lasting antioxidant, 0.2-0.4 parts of lubricant, and 0.5-0.8 parts of water-resistant agent.

[0011] Furthermore, by weight, it comprises the following components: 100 parts of base polyolefin resin, 2.5 parts of maleic anhydride (MAH), 0.2 parts of initiator, 1.0 part of grafting efficiency promoter, 0.8 parts of side reaction inhibitor, 0.5 parts of long-lasting antioxidant, 0.3 parts of lubricant, and 0.6 parts of water-resistant agent.

[0012] The base polyolefin resin is a polyolefin material with good compatibility with the outer PPR, including at least one of random copolymer polypropylene PPR, block copolymer polypropylene PP-B, and linear low-density polyethylene LLDPE, with a melt flow rate (MFR) of 0.5-3.0 g / 10 min at 230°C and 2.16 kg load.

[0013] Furthermore, the random copolymer polypropylene (PPR) has a melt flow rate (MFR) of 0.5-2.0 g / 10 min at 230°C and 2.16 kg load, and an ethylene content of 2-4%; the block copolymer polypropylene (PP-B) has a melt flow rate (MFR) of 1.0-3.0 g / 10 min at 230°C and 2.16 kg load; and the linear low-density polyethylene (LLDPE) has a melt flow rate (MFR) of 1.0-3.0 g / 10 min at 230°C and 2.16 kg load.

[0014] Furthermore, the grafting efficiency promoter is at least one of triallyl isocyanurate (TAIC), trimethylolpropane trimethacrylate (TMPTMA), and divinylbenzene (DVB).

[0015] Furthermore, the side reaction inhibitor is a compound system of hindered phenolic antioxidants and phosphite antioxidants.

[0016] Furthermore, the side reaction inhibitor comprises a primary antioxidant 1010 and a secondary antioxidant 168, wherein the mass ratio of the primary antioxidant 1010 to the secondary antioxidant 168 is 1-1.5:1. It inhibits the β-chain scission degradation of polyolefins by scavenging free radicals and decomposing hydroperoxides.

[0017] Furthermore, in addition to the side reaction inhibitor, a long-lasting antioxidant is added, wherein the long-lasting antioxidant is at least one of antioxidant 1076 or 3114, to improve the long-term thermal stability of the grafted resin.

[0018] Furthermore, the initiator comprises dicumyl peroxide (DCP) and benzoyl peroxide (BPO), wherein the mass ratio of DCP to BPO is 0.8-1.2:1.2-0.8.

[0019] Furthermore, the lubricant used is polyethylene wax, zinc stearate, or ethylene bis-stearamide (EBS).

[0020] Furthermore, the water-resistant agent selected is γ-aminopropyltriethoxysilane KH550.

[0021] Furthermore, the grafting efficiency promoter comprises TAIC and TMPTMA in a mass ratio of 1-3:1, preferably 1.5-2:1.

[0022] The method for preparing maleic anhydride grafted adhesive resin for PPR / PA composite pipes includes the following steps: S1 Pretreatment: Dry the base polyolefin resin to remove moisture; S2 Mixing: According to the raw material formula, add the basic polyolefin resin, maleic anhydride masterbatch, initiator, grafting efficiency promoter, side reaction inhibitor, antioxidant, lubricant and water-resistant agent to a high-speed mixer and mix for 5-10 minutes at a mixing speed of 300-500 r / min. S3 Melt Grafting: The material mixed in step S2 is added to a co-rotating twin-screw extruder, heated and melted for extrusion; S4 post-processing: The extruded material is cooled with water, pelletized, and dried to obtain maleic anhydride grafted adhesive resin particles.

[0023] Further, in step S3, the segmented temperatures of the co-rotating twin-screw extruder are as follows: feeding section 160-170℃, melting section 180-190℃, reaction section 200-210℃, homogenization section 200-205℃, and die head 195-200℃; a vacuum port is set after the reaction section, with a vacuum degree ≤-0.08MPa, to remove residual monomers, solvents, and by-products; the screw speed is 150-250 rpm, and the residence time is controlled at 2-4 minutes.

[0024] Compared with the prior art, the beneficial effects achieved by the present invention are: 1. Using PPR of the same material as the outer layer as the grafting matrix to achieve homogeneous matching, eliminating the difference in thermal expansion coefficient and interfacial stress caused by different substrates; 2. Wide-temperature-range staged initiation is achieved by using DCP and BPO as initiators. BPO is pre-initiated in the low-temperature region (130-150℃), while DCP is the main initiator in the high-temperature region (170-190℃). At the same time, the grafting and degradation processes are balanced, BPO is preferentially consumed, the concentration of DCP is reduced, and the probability of β-chain scission (absorption of tertiary hydrogen) of PPR is reduced.

[0025] 3. When grafting a single MAH, MAH self-polymerization is difficult, grafting points are dispersed, and the probability of reaction with the terminal amino group of PA12 is low. However, the double bond of TAIC preferentially reacts with PPR free radicals to form short branches, and the double bonds at the end of the branches then copolymerize with MAH to form a "PPR-TAIC-MAH" ternary graft structure. The role of TMPTMA (trimethylolpropane trimethacrylate) is to improve the melt strength of the graft and prevent degradation during high-temperature extrusion. At the same time, the benzene ring structure in DVB (divinylbenzene) generates π-π interactions with the vinyl side chains of PPR, and the divinyl groups bridge different PPR molecular chains, enhancing the compatibility of the graft with the PPR substrate and reducing phase separation. Finally, the TAIC / TMPTMA multifunctional monomer constructs a three-level structure of "main link grafting + branch reinforcement + network fixation", increasing the density of MAH grafting points. 4. Existing technologies, without or with only the addition of antioxidants, cause severe β-chain scission of PPR during high-temperature grafting. This invention employs a 1010 / 168 compound antioxidant system as a side reaction inhibitor. Antioxidant 1010 captures free radicals in PPR macromolecules to block chain degradation, while antioxidant 168 decomposes hydrogen peroxide to inhibit oxidative propagation, synergistically inhibiting β-chain scission during grafting and maintaining the stability of PPR molecular weight. Simultaneously, additional antioxidants 1076 or 3114 are added to provide long-term thermal stability, forming a dual guarantee of "reaction inhibition + long-term protection".

[0026] 5. In terms of interfacial bonding, existing technologies rely on the amino group (-NH2) at the end of PA and the anhydride group (-CO-O-CO-) on the adhesive resin to form a single imide covalent bond, with a theoretical bonding strength of 4-8 N / mm. The present invention forms multiple interfacial synergies, including imide covalent bonds (-NH2 and -CO-O-CO-), hydrogen bond networks (isocyanurate carbonyl group of TAIC and amide group of PA12), and coordination effects (ester group of TMPTMA and carboxyl group at the end of PA12), and the destruction mode changes from interfacial separation to PA12 cohesive destruction. Attached Figure Description

[0027] Figure 1 This is a process flow diagram of the adhesive resin production process of the present invention. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0029] In this embodiment of the invention, the sources of the different raw materials are as follows: Random copolymer polypropylene (PPR): PetroChina Daqing Refining & Chemical PA14D-2.

[0030] Block copolymer polypropylene PP-B: Sinopec Yangzi Petrochemical PPB-M02.

[0031] Linear low-density polyethylene (LLDPE): Sinopec Maoming DFDA-7042.

[0032] Polyamide PA12: Wanhua Chemical, L3000.

[0033] Maleic anhydride (MAH): Shandong Qilu Petrochemical industrial grade, purity ≥99.5%.

[0034] Initiator DCP / BPO: Shanghai Aladdin.

[0035] Grafting efficiency promoters TAIC / TMPTMA / DVB: Jiangsu Sanmu Chemical Co., Ltd.

[0036] Antioxidant 1010 / 168 / 1076 / 3114: BASF.

[0037] Lubricant EBS / Polyethylene Wax / Zinc Stearate: Hangzhou Haishi Chemical.

[0038] Water-resistant agent KH550: Nanjing Shuguang Silane Chemical Co., Ltd.

[0039] All raw materials are commercially available conventional industrial raw materials.

[0040] Example 1: The formulation composition (parts by weight) of the general-purpose PPR-based adhesive resin is shown in Table 1.

[0041] Table 1 .

[0042] Example 1: The preparation method of the general-purpose PPR-based adhesive resin includes the following steps: S1 Pretreatment: Dry the base polyolefin resin to remove moisture; S2 Mixing: According to the raw material formula, add the basic polyolefin resin, maleic anhydride masterbatch, initiator, grafting efficiency promoter, side reaction inhibitor, antioxidant, lubricant and water-resistant agent to the high-speed mixer and mix for 8 minutes at a mixing speed of 400 r / min. S3 Melt Grafting: The material mixed in step S2 is added to a co-rotating twin-screw extruder and heated for melt extrusion. The operating conditions are as follows: the co-rotating twin-screw extruder uses segmented temperature control: feeding section 165℃, melting section 185℃, reaction section 205℃, homogenization section 205℃, and die head 198℃. A vacuum port is set after the reaction section, with a vacuum degree ≤-0.08MPa, to remove residual monomers, solvents, and by-products. The screw speed is 200 rpm, and the residence time is controlled at 3 minutes. S4 post-processing: The extruded material is cooled with water, pelletized, and dried to obtain maleic anhydride grafted adhesive resin particles.

[0043] Example 2: The formulation composition (parts by weight) of the high bond strength (TAIC / TMPTMA compound) adhesive resin is shown in Table 2.

[0044] Table 2 .

[0045] Example 3: The formulation composition (parts by weight) of the LLDPE modified matrix adhesive resin is shown in Table 3.

[0046] Table 3 .

[0047] The formulation of the adhesive resin of Comparative Example 1 was the same as that of Example 2, except that "Comparative Example 1 did not add grafting efficiency promoter (TAIC+TMPTMA)", and all other conditions remained the same.

[0048] The formulation of the adhesive resin in Comparative Example 2 was the same as that in Example 2, except that "the grafting efficiency promoter used in Comparative Example 2 was TAIC only, not TMPTMA, and the weight of TAIC was 1.5 parts". All other conditions remained the same.

[0049] The formulation of the adhesive resin in Comparative Example 3 was the same as that in Example 2, except that antioxidant 3114 was not added in Comparative Example 3, while all other conditions remained the same.

[0050] The formulation of the adhesive resin in Comparative Example 4 was the same as that in Example 2, except that "only a single initiator DCP was used, BPO was not used, and the weight of DCP was 0.25 parts", while the other conditions remained unchanged.

[0051] The preparation methods of the adhesive resins in Examples 2-3 and Comparative Examples 1-4 are all the same as those in Example 1.

[0052] The adhesive resins prepared in Examples 1-3 and Comparative Examples 1-4 were subjected to performance tests, and the test methods are described below: 1) Detection of maleic anhydride grafting rate of adhesive resin In this invention, the grafting rate of the adhesive resin is determined by acid-base titration, which measures the mass percentage of maleic anhydride units grafted onto the polyolefin molecular chain.

[0053] The grafting rate was determined by acid-base titration: the carboxyl group (-COOH) generated after the hydrolysis of maleic anhydride grafted onto the polyolefin molecular chain reacts with KOH (strong base) to neutralize the carboxyl group. The mass of maleic anhydride grafted onto the polyolefin molecular chain was calculated by the amount of KOH consumed, and the grafting rate was finally obtained.

[0054] 2) Testing of PPR / PA12 interlaminar peel strength (N / mm) First, prepare the exfoliated sample to be tested, following these steps: ① PA12 sheet preparation: PA12 is hot-pressed into 0.2mm thin sheets at 210℃.

[0055] ②PPR sheet preparation: PPR (PA14D-2) is hot-pressed into 2.0mm thin sheets at 200℃.

[0056] ③ Preparation of adhesive resin film: The adhesive resin of the present invention is hot-pressed into a 0.15mm film at 200℃.

[0057] ④ Composite molding: Stack PPR sheet / adhesive resin film / PA12 sheet in sequence, hot press composite at 220℃ and 0.5MPa for 20 seconds, cool to room temperature, and cut into 25mm wide samples, which are the peel samples to be tested.

[0058] The peel samples prepared above were subjected to peel tests. T-type peeling was performed according to GB / T 2791 standard at a peeling speed of 50 mm / min to obtain the PPR / PA12 interlayer peel strength (N / mm) data.

[0059] 3) Testing of interlaminar peel strength (N / mm) after 95℃ / 1000h heat aging First, prepare a composite sample of PPR sheet / adhesive resin film / PA12 sheet according to the method in step 2) above. Place the composite sample in a heat cycle chamber and heat-treat it at 95°C for 1000 hours. Then, take out the sample, cool it to room temperature, and test the interlayer peel strength according to the method in step 2).

[0060] 4) Testing of interlayer bonding after 1000 cycles at 0-95℃ First, prepare a PPR sheet / adhesive resin film / PA12 sheet composite sample according to step 2) above. Place the composite sample in a thermal cycling chamber: maintain at 0℃ for 15 min, then raise the temperature to 95℃, maintain at 95℃ for 15 min, and then cool down to 0℃. Repeat this hot and cold treatment cycle, with a heating and cooling rate of 10℃ / min. Repeat this process 1000 times, with one 0℃-95℃ hot and cold cycle constituting one cycle. After 1000 cycles, remove the sample and observe whether there is delamination or detachment between the layers. Do not prepare a new sample after each cycle; directly observe the original composite interface.

[0061] The test results of the adhesive resins prepared in Examples 1-3 according to the above test procedure are shown in Table 4.

[0062] Table 4 .

[0063] The test results of the adhesive resins prepared in Example 2 and Comparative Examples 1-4 according to the above test procedure are shown in Table 5.

[0064] Table 5 .

[0065] According to the results in Table 5: 1. Compared with Example 1, without the addition of grafting efficiency promoter, Example 2 showed a significant decrease in grafting rate and a peel strength of only 4.2 N / mm. After high-temperature aging, it almost failed, indicating that the TAIC / TMPTMA compound is the key to improving grafting rate and bonding strength.

[0066] 2. In Comparative Example 2 and Control Example 2, which used only TMPTMA without TAIC, the grafting rate and peel strength were significantly reduced, proving that the combination of the two promoters has a synergistic effect and can further improve the interfacial bonding force.

[0067] 3. Compared with Example 2, which did not add antioxidant 3114, the long-term heat aging resistance performance of Example 2 and Example 3 decreased significantly and the peel strength retention rate decreased significantly, proving that antioxidant 3114 is crucial for long-term high-temperature stability.

[0068] 4. Compared with Example 2, which uses only a single initiator DCP, the grafting rate decreased and the aging strength deteriorated, proving that the DCP and BPO combined initiation system can improve grafting efficiency and reduce degradation.

[0069] In addition, commercially available general-purpose PP-g-MAH, FH116A, was used from Dongguan Darui Plastics Co., Ltd., and its performance was tested according to steps 1) to 4) above. The results are shown in Table 6.

[0070] Table 6 .

[0071] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A maleic anhydride grafting adhesive resin for PPR / PA composite pipes, characterized in that, By weight, it comprises the following components: 100 parts of base polyolefin resin, 1.5-4.0 parts of maleic anhydride (MAH), 0.1-0.5 parts of initiator, 0.5-2.0 parts of grafting efficiency promoter, 0.3-1.5 parts of side reaction inhibitor, 0.2-1.0 parts of long-lasting antioxidant, 0.1-0.5 parts of lubricant, and 0.5-1.0 parts of water-resistant agent; The base polyolefin resin is a polyolefin material with good compatibility with the outer PPR, including at least one of random copolymer polypropylene PPR, block copolymer polypropylene PP-B and linear low-density polyethylene LLDPE, with a melt flow rate (MFR) of 0.5-3.0 g / 10 min at 230°C and 2.16 kg load. The grafting efficiency promoter is at least one of triallyl isocyanurate (TAIC), trimethylolpropane trimethacrylate (TMPTMA), and divinylbenzene (DVB). The side effect inhibitor is a combination system of hindered phenolic antioxidants and phosphite antioxidants.

2. The maleic anhydride graft bonding resin for PPR / PA composite pipes as described in claim 1, characterized in that, The product comprises the following components by weight: 100 parts of base polyolefin resin, 2.0-3.0 parts of maleic anhydride (MAH), 0.15-0.3 parts of initiator, 0.8-1.5 parts of grafting efficiency promoter, 0.5-1.0 parts of side reaction inhibitor, 0.3-0.6 parts of long-lasting antioxidant, 0.2-0.4 parts of lubricant, and 0.5-0.8 parts of water-resistant agent.

3. The maleic anhydride grafting adhesive resin for PPR / PA composite pipes as described in claim 1, characterized in that, The initiator comprises dicumyl peroxide (DCP) and benzoyl peroxide (BPO), with a mass ratio of DCP to BPO of 0.8-1.2:1.2-0.

8.

4. The maleic anhydride grafting adhesive resin for PPR / PA composite pipes as described in claim 1, characterized in that, The side reaction inhibitors include primary antioxidant 1010 and secondary antioxidant 168, with a mass ratio of primary antioxidant 1010 to secondary antioxidant 168 of 1-1.5:

1.

5. The maleic anhydride grafting adhesive resin for PPR / PA composite pipes as described in claim 1, characterized in that, The long-lasting antioxidant is at least one of antioxidant 1076 or 3114.

6. The maleic anhydride graft bonding resin for PPR / PA composite pipes as described in claim 1, characterized in that, The lubricant used is polyethylene wax, zinc stearate, or ethylene bis-stearamide (EBS).

7. The maleic anhydride grafting adhesive resin for PPR / PA composite pipes as described in claim 1, characterized in that, The water-resistant agent is γ-aminopropyltriethoxysilane KH550, and the grafting efficiency promoter includes TAIC and TMPTMA, with a mass ratio of 1-3:

1.

8. The method for preparing maleic anhydride grafted adhesive resin for PPR / PA composite pipes as described in claim 1, characterized in that, Includes the following steps: S1 Pretreatment: Dry the base polyolefin resin to remove moisture; S2 Mixing: According to the raw material formula, add the basic polyolefin resin, maleic anhydride masterbatch, initiator, grafting efficiency promoter, side reaction inhibitor, antioxidant, lubricant and water-resistant agent to a high-speed mixer and mix for 5-10 minutes at a mixing speed of 300-500 r / min. S3 Melt Grafting: The material mixed in step S2 is added to a co-rotating twin-screw extruder, heated and melted for extrusion; S4 post-processing: The extruded material is cooled with water, pelletized, and dried to obtain maleic anhydride grafted adhesive resin particles.

9. The preparation method according to claim 8, characterized in that, In step S3, the segmented temperatures of the co-rotating twin-screw extruder are as follows: feeding section 160-170℃, melting section 180-190℃, reaction section 200-210℃, homogenization section 200-205℃, and die head 195-200℃; a vacuum port is set after the reaction section, with a vacuum degree ≤-0.08MPa, to remove residual monomers, solvents, and by-products; the screw speed is 150-250 rpm, and the residence time is controlled at 2-4 minutes.

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