Nylon alloy oxygen-barrier composite pipe and preparation method thereof

Abstract

The invention discloses a nylon alloy oxygen-barrier composite pipe and a preparation method thereof. The preparation method comprises the following steps: firstly, pretreating a nylon alloy raw material; the preparation method comprises the following steps: firstly, mixing all raw materials of the nylon alloy pretreated in the step 1 at normal temperature in proportion by adopting a high-speed mixer, and then preparing nylon alloy granules by adopting a twin-screw extrusion granulator; the nylon alloy granules prepared in the second step are dried and then placed in a barrier layer extruder barrel of an extruder unit, hot melt adhesive is placed in an adhesive layer extruder barrel of the extruder unit, and the nylon alloy oxygen barrier composite pipe is prepared. According to the oxygen barrier layer nylon alloy, the compatilizer and the antioxidant effectively improve the interfacial compatibility and thermal stability of PE-RT or PP-R and nylon, improve the bonding performance and heat resistance of the alloy oxygen barrier layer and the PE-RT or PP-R working pipe material, solve the problems that a traditional EVOH oxygen barrier layer is prone to cracking, layering and the like in a hot water environment, and enable construction to be efficient.

Description

Technical Field

[0001] The invention relates to the technical field of pipe preparation, and in particular to a nylon alloy oxygen-barrier composite pipe and a preparation method thereof. Background Art

[0002] Oxygen-barrier plastic pipes are widely accepted by users in the fields of hot and cold water transportation, HVAC floor heating, radiator connection, etc. due to their superior performance, such as safety, hygiene, oxygen barrier, and long service life. There are various oxygen-barrier plastic pipes at home and abroad, which can be divided into metal oxygen-barrier pipes and polymer oxygen-barrier pipes according to different barrier materials. Metal oxygen barrier mainly achieves oxygen barrier by compounding aluminum and other metal layers in the middle of the plastic pipe wall; polymer oxygen barrier is mainly made by compounding plastic pipes with barrier polymers, such as ethylene-vinyl alcohol copolymer (EVOH), to make oxygen-barrier pipes. Common EVOH-compounded three-layer and five-layer cross-linked polyethylene (PE-X) pipes, PE-RT pipes, polybutylene (PB) pipes, etc. However, both metal oxygen barrier layers and EVOH oxygen barrier layers have their own defects. Although the metal oxygen barrier layer has excellent and stable barrier properties, its waste products and waste are difficult to be directly recycled and reused, and the energy consumption is high and the environmental pressure is relatively large. Oxygen-barrier plastic pipes made of EVOH have excellent oxygen-barrier properties only under normal temperature and humidity conditions. Once the temperature rises or the humidity increases (high temperature and high humidity), especially in the high water vapor environment conditions of hot water transportation, their barrier properties decay rapidly and cannot meet the oxygen-barrier requirements. At the same time, their bonding and composite properties with polyolefins are poor, and interlayer cracking is easy to affect the service life.

[0003] To this end, the present invention proposes a nylon alloy oxygen-barrier composite pipe that is not affected by high temperature and high humidity environments and a preparation method thereof. Summary of the invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a nylon alloy oxygen-barrier composite tube and a preparation method thereof, which has the characteristics of good composite effect, excellent oxygen-barrier performance, no influence from high temperature and high humidity environment, and long service life.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A nylon alloy oxygen-barrier composite tube comprises a working tube, a nylon alloy barrier layer is provided on the outer surface of the working tube, and a first hot-melt adhesive layer is provided between the nylon alloy barrier layer and the working tube.

[0007] Furthermore, it comprises an outer protective layer, the outer surface of the nylon alloy barrier layer is provided with an outer protective layer, and a second hot melt adhesive layer is provided between the outer protective layer and the nylon alloy barrier layer.

[0008] Furthermore, the working tube is a PE-RT I type tube, a PE-RT II type tube or a PP-R tube; the nylon alloy of the nylon alloy barrier layer is a semi-aromatic nylon alloy; specifically, MXD6 / PE-RT alloy, MXD6 / EVOH / PE-RT alloy, MXD6 / PP-R alloy or MXD6 / EVOH / PP-R alloy.

[0009] Furthermore, the nylon alloy is composed of the following raw materials in parts by weight:

[0010] 20-80 parts of nylon, 1-50 parts of EVOH, 19-50 parts of polyolefin resin, 5-20 parts of compatibilizer, and 0.2-0.5 parts of antioxidant.

[0011] Furthermore, the nylon is MXD6; the EVOH is an ethylene-vinyl alcohol copolymer with an ethylene content of 32 mol%-44 mol%; the compatibilizer is maleic anhydride grafted polyethylene or maleic anhydride grafted polypropylene, and the maleic anhydride grafting rate is 0.8%-2.0%; the antioxidant is one or more of antioxidant 1010, antioxidant 168, and antioxidant 330; and the polyolefin resin is PE-RT or PP-R.

[0012] Furthermore, the first hot melt adhesive layer and the second hot melt adhesive layer are maleic anhydride grafted polyethylene or maleic anhydride grafted polypropylene, and the maleic anhydride grafting rate is 0.2%-2.0%; the outer protective layer is PE-RT I type, PE-RT II type or PP-R.

[0013] The present invention also proposes a method for preparing the nylon alloy oxygen-barrier composite tube, comprising the following steps:

[0014] Step 1: First, pre-treat the nylon alloy raw material;

[0015] Step 2: firstly, using a high-speed mixer to mix the nylon alloy raw materials pretreated in step 1 in proportion at room temperature, and then using a twin-screw extruder granulator to prepare nylon alloy pellets;

[0016] Step 3: First dry the nylon alloy pellets prepared in step 2, and then place them in the barrier layer extruder barrel of the extruder unit, and place the hot melt adhesive in the adhesive layer extruder barrel of the unit to obtain a nylon alloy oxygen-barrier composite tube.

[0017] Furthermore, when EVOH < 1 part, the nylon is dried in an electric hot air drying oven at 90-110°C for 6-10 hours and then used immediately; when 1≤EVOH≤50 parts, the nylon and EVOH are dried in an electric hot air drying oven at 90-110°C for 6-10 hours and then used immediately;

[0018] Step 2: The speed of the granulating screw is 20-30 r / min, the temperatures of each section of the barrel are set to 200, 230, 250, 270, 240°C, and the melt temperature is 250°C.

[0019] Further, step three: first, the nylon alloy pellets prepared in step two are placed in an electric hot air drying oven at 90-110° C. for 6-10 hours, and then placed in the barrier layer extruder barrel of a five-layer plastic pipe extrusion unit, PE-RT or PP-R is placed in the inner layer extruder barrel and the outer protective layer extruder barrel of the unit, and the hot melt adhesive is placed in the adhesive layer extruder barrel of the unit to prepare a five-layer new nylon alloy oxygen barrier tube;

[0020] Among them, the extrusion process conditions of the inner working tube are 150-210°C, the screw speed is 20-28r / min, and the extrusion process conditions of the nylon alloy barrier layer are 200-300°C, and the screw speed is 30-50r / min.

[0021] Furthermore, step three: first put the nylon alloy pellets prepared in step two into an electric hot air drying oven at 90-110°C for 6-10h, and then place them in the barrier layer extruder barrel of the three-layer plastic pipe extrusion unit, PE-RT or PP-R is placed in the inner working tube extruder barrel of the unit, and the hot melt adhesive is placed in the adhesive layer extruder barrel of the unit to prepare a three-layer new nylon alloy oxygen barrier tube; wherein, the extrusion process conditions of the inner working tube are 150-210°C, the screw speed is 20-28r / min, and the extrusion process conditions of the nylon alloy barrier layer are 200-300°C, and the screw speed is 30-50r / min.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1) The outer surface of the inner working tube of the present invention is provided with a nylon alloy oxygen barrier layer. On the one hand, due to the strong hydrogen bonding between C=O and NH in the nylon molecular structure, the nylon macromolecular chains can be tightly combined together, so that the nylon has high barrier properties, and its oxygen barrier effect is no less than that of the traditional EVOH oxygen barrier layer; on the other hand, the present invention adopts semi-aromatic nylon, which contains both aliphatic chain segments and rigid benzene ring structures in its structure, has good heat resistance and processability, and the steric hindrance of the benzene ring is large, which is not conducive to the penetration of water vapor molecules. The barrier performance is not affected by temperature and humidity, and is more stable and reliable than EVOH;

[0024] 2) The oxygen barrier layer nylon alloy used in the present invention effectively improves the interface compatibility and thermal stability of PE-RT or PP-R and nylon through compatibilizers and antioxidants, greatly improving the bonding performance and heat resistance of the alloy oxygen barrier layer and the PE-RT or PP-R working pipe material, solving the problems of easy cracking and delamination of the traditional EVOH oxygen barrier layer in hot water environment, making the construction convenient, simple and fast;

[0025] 3) The damping alloy oxygen-barrier composite tube prepared by the method of the present invention has the characteristics of simple structure, good composite effect, excellent oxygen-barrier performance, no influence from high temperature and high humidity environment, and long service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the five-layer structure of the composite pipe of the present invention;

[0027] Figure 2 It is a schematic cross-sectional view of a five-layer structure of a composite pipe of the present invention;

[0028] Figure 3 This is a schematic diagram of the three-layer structure of the composite pipe of the present invention;

[0029] Figure 4 It is a schematic cross-sectional view of the three-layer structure of the composite pipe of the present invention;

[0030] Figure 5 This is a schematic diagram of the composite pipe structure of Comparative Example 1 of the present invention;

[0031] Figure 6 This is a schematic diagram of the composite pipe structure of Comparative Example 2 of the present invention.

[0032] In the figure: 1. working tube; 2. first hot melt adhesive layer; 3. nylon alloy barrier layer; 4. outer protective layer; 5. EVOH barrier layer; 6. second hot melt adhesive layer. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the described scope.

[0034] The present invention is compared with a commercially available EVOH oxygen-barrier multilayer composite PE-RT pipe, where the commercially available PE-RT is a type I PE-RT pipe, and EVOH is an ethylene-vinyl alcohol copolymer with an ethylene content of 32 mol% to 44 mol%.

[0035] Comparative Example 1: Commercially available EVOH oxygen-barrier three-layer composite PE-RT pipe, structure see Figure 5 .

[0036] Comparative Example 2: Commercially available EVOH oxygen-barrier five-layer composite PE-RT pipe, structure see Figure 6 .

[0037] Comparative Example 3: Five-layer structure

[0038] The barrier layer is MXD6 / PE-RT alloy with the following formula:

[0039] 70 parts of nylon MXD6, 30 parts of PE-RT II, ​​10 parts of maleic anhydride grafted polyethylene, 0.15 parts of antioxidant 1010, and 0.15 parts of antioxidant 330.

[0040] The hot melt adhesive is maleic anhydride grafted polyethylene, and the maleic anhydride grafting rate is 0.4-0.5%.

[0041] The steps for pipe preparation are as follows:

[0042] Step 1: Dry MXD6 in an electric hot air drying oven at 95°C for 6 hours and use it immediately;

[0043] Step 2: Mix the raw materials in the above ratio at room temperature for 5 minutes using a high-speed mixer; and prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 25r / min, the temperatures of each section of the barrel are set at 200, 230, 250, 270, and 240°C, and the melt temperature is 250°C.

[0044] Step 3: Place the MXD6 / PE-RT alloy pellets prepared by granulation into a 95°C electric heated air drying oven for 8 hours, and then place them in the barrier layer extruder barrel of the five-layer plastic pipe extrusion unit, place the PE-RT II type in the inner layer extruder barrel and the outer protective layer extruder barrel of the unit, and place the hot melt adhesive in the adhesive layer extruder barrel of the unit to prepare a new MXD6 / PE-RT alloy oxygen-barrier PE-RT II pipe.

[0045] Among them, the extrusion process conditions of the inner working tube are 200°C and the screw speed is 25r / min, and the extrusion process conditions of the nylon alloy barrier layer are 250°C and the screw speed is 35r / min.

[0046] Comparative Example 4: Five-layer structure

[0047] The barrier layer is MXD6 / PP-R alloy, the formula is as follows:

[0048] 70 parts of nylon MXD6, 30 parts of PP-R, 12 parts of maleic anhydride grafted polypropylene compatibilizer, 0.25 parts of antioxidant 1010, and 0.25 parts of antioxidant 168.

[0049] The hot melt adhesive is maleic anhydride grafted polypropylene, and the maleic anhydride grafting rate is 1.2-1.5%.

[0050] The steps for pipe preparation are as follows:

[0051] Step 1: Dry MXD6 in an electric hot air drying oven at 90°C for 8 hours and use it immediately;

[0052] Step 2: Mix the raw materials in the above ratio at room temperature for 10 minutes using a high-speed mixer; and prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 20r / min, the temperatures of each section of the barrel are set to 200, 220, 240, 250, and 230°C, and the melt temperature is 250°C.

[0053] Step 3: Place the MXD6 / PP-R alloy pellets prepared by granulation into a 90℃ electric blast drying oven for 8 hours, and then place them in the barrier layer extruder barrel of the five-layer plastic pipe extruder unit, PP-R is placed in the inner layer extruder barrel and the outer protective layer extruder barrel of the unit, and the hot melt adhesive is placed in the adhesive layer extruder barrel of the unit to prepare a new MXD6 / PP-R alloy oxygen-barrier PP-R pipe. Among them, the extrusion process conditions of the inner working pipe are 190℃ and the screw speed is 20r / min, and the extrusion process conditions of the nylon alloy barrier layer are 260℃ and the screw speed is 35r / min.

[0054] Comparative Example 5: Three-layer structure

[0055] The barrier layer is MXD6 / PE-RT alloy with the following formula:

[0056] 50 parts of nylon MXD6, 50 parts of PE-RT, 8 parts of maleic anhydride grafted polyethylene compatibilizer, and 0.2 parts of antioxidant 330.

[0057] The hot melt adhesive is maleic anhydride grafted polypropylene, and the maleic anhydride grafting rate is 0.6-0.8%.

[0058] The steps for pipe preparation are as follows:

[0059] Step 1: Dry MXD6 in an electric hot air drying oven at 90°C for 8 hours and use it immediately;

[0060] Step 2: Mix the raw materials in the above ratio at room temperature for 10 minutes using a high-speed mixer; and prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 20r / min, the temperatures of each section of the barrel are set to 200, 220, 240, 250, and 230°C, and the melt temperature is 250°C.

[0061] Step 3: Place the MXD6 / PE-RT alloy pellets prepared by granulation into a 90℃ electric blast drying oven for 8 hours, then place them in the barrier layer extruder barrel of the three-layer plastic pipe extrusion unit, PE-RT in the inner layer extruder barrel of the unit, and hot melt adhesive in the adhesive layer extruder barrel of the unit to prepare a three-layer MXD6 / PE-RT alloy oxygen-barrier PE-RT pipe. Among them, the extrusion process conditions of the inner working pipe are 180-190℃, the screw speed is 20r / min, and the extrusion process conditions of the nylon alloy barrier layer are 230℃, and the screw speed is 35r / min.

[0062] Example 1: Five-layer structure

[0063] The barrier layer is MXD6 / EVOH / PE-RT alloy, and the formula is as follows:

[0064] 50 parts of nylon MXD6, 20 parts of EVOH, 30 parts of PE-RT II, ​​12 parts of maleic anhydride grafted polyethylene compatibilizer, and 0.3 parts of antioxidant 1010.

[0065] The hot melt adhesive is maleic anhydride grafted polyethylene, and the maleic anhydride grafting rate is 0.4-0.5%.

[0066] The steps for pipe preparation are as follows:

[0067] Step 1: Dry MXD6 and EVOH in an electric hot air drying oven at 95°C for 8 hours and use them immediately;

[0068] Step 2: Mix the raw materials in the above ratio at room temperature for 10 minutes using a high-speed mixer; and prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 25r / min, the temperatures of each section of the barrel are set at 200, 220, 240, 250, and 230°C, and the melt temperature is 250°C.

[0069] Step 3: Place the MXD6 / EVOH / PE-RT alloy pellets prepared by granulation into a 95°C electric heating blast drying oven for 8 hours, and then place them in the barrier layer extruder barrel of the five-layer plastic pipe extruder unit, PE-RT II type is placed in the inner layer extruder barrel and the outer protective layer extruder barrel of the unit, and hot melt adhesive is placed in the adhesive layer extruder barrel of the unit to prepare a new MXD6 / EVOH / PE-RT alloy oxygen-barrier PE-RT II pipe. Among them, the extrusion process conditions of the inner working pipe are 210°C and the screw speed is 30r / min, and the extrusion process conditions of the nylon alloy barrier layer are 240°C and the screw speed is 40r / min.

[0070] Example 2: Five-layer structure

[0071] The barrier layer is MXD6 / EVOH / PE-RT alloy, and the formula is as follows:

[0072] 80 parts of nylon MXD6, 1 part of EVOH, 19 parts of PE-RT II, ​​16 parts of maleic anhydride grafted polyethylene compatibilizer, and 0.3 parts of antioxidant 1010.

[0073] The hot melt adhesive is maleic anhydride grafted polyethylene, and the maleic anhydride grafting rate is 0.4-0.5%.

[0074] The steps for pipe preparation are as follows:

[0075] Step 1: Dry MXD6 and EVOH in an electric hot air drying oven at 95°C for 8 hours and use them immediately;

[0076] Step 2: Mix the raw materials in the above ratio at room temperature for 10 minutes using a high-speed mixer; and prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 25r / min, the temperatures of each section of the barrel are set at 200, 220, 240, 250, and 230°C, and the melt temperature is 250°C.

[0077] Step 3: Place the MXD6 / EVOH / PE-RT alloy pellets prepared by granulation into a 95°C electric heating blast drying oven for 8 hours, and then place them in the barrier layer extruder barrel of the five-layer plastic pipe extruder unit, PE-RT II type is placed in the inner layer extruder barrel and the outer protective layer extruder barrel of the unit, and hot melt adhesive is placed in the adhesive layer extruder barrel of the unit to prepare a new MXD6 / EVOH / PE-RT alloy oxygen-barrier PE-RT II pipe. Among them, the extrusion process conditions of the inner working pipe are 210°C and the screw speed is 30r / min, and the extrusion process conditions of the nylon alloy barrier layer are 240°C and the screw speed is 40r / min.

[0078] Example 3: Five-layer structure

[0079] The barrier layer is MXD6 / EVOH / PE-RT alloy, and the formula is as follows:

[0080] 20 parts of nylon MXD6, 30 parts of EVOH, 50 parts of PE-RT II, ​​12 parts of maleic anhydride grafted polyethylene compatibilizer, 0.3 parts of antioxidant 1010, and 0.1 parts of antioxidant 330.

[0081] The hot melt adhesive is maleic anhydride grafted polyethylene, and the maleic anhydride grafting rate is 0.5-0.6%.

[0082] The steps for pipe preparation are as follows:

[0083] Step 1: Dry MXD6 and EVOH in an electric hot air drying oven at 95°C for 8 hours and use them immediately;

[0084] Step 2: Mix the raw materials in the above ratio at room temperature for 10 minutes using a high-speed mixer; and prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 25r / min, the temperatures of each section of the barrel are set at 200, 220, 240, 250, and 230°C, and the melt temperature is 250°C.

[0085] Step 3: Place the MXD6 / EVOH / PE-RT alloy pellets prepared by granulation into a 95°C electric heating blast drying oven for 8 hours, and then place them in the barrier layer extruder barrel of the five-layer plastic pipe extruder unit, PE-RT II type is placed in the inner layer extruder barrel and the outer protective layer extruder barrel of the unit, and hot melt adhesive is placed in the adhesive layer extruder barrel of the unit to prepare a new MXD6 / EVOH / PE-RT alloy oxygen-barrier PE-RT II pipe. Among them, the extrusion process conditions of the inner working pipe are 210°C and the screw speed is 30r / min, and the extrusion process conditions of the nylon alloy barrier layer are 240°C and the screw speed is 40r / min.

[0086] Example 4: Five-layer structure

[0087] The barrier layer is MXD6 / EVOH / PP-R alloy, and the formula is as follows:

[0088] 50 parts of nylon MXD6, 20 parts of EVOH, 30 parts of PP-R, 15 parts of maleic anhydride grafted polypropylene compatibilizer, 0.25 parts of antioxidant 1010, and 0.25 parts of antioxidant 168.

[0089] The hot melt adhesive is maleic anhydride grafted polypropylene, and the maleic anhydride grafting rate is 1.2-1.5%.

[0090] The steps for pipe preparation are as follows:

[0091] Step 1: Dry MXD6 and EVOH in an electric hot air drying oven at 90°C for 8 hours and use them immediately;

[0092] Step 2: Mix the raw materials in the above ratio at room temperature for 10 minutes using a high-speed mixer; and prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 20r / min, the temperatures of each section of the barrel are set to 200, 220, 240, 250, and 230°C, and the melt temperature is 250°C.

[0093] Step 3: Place the MXD6 / EVOH / PP-R alloy pellets prepared by granulation into a 90℃ electric heating blast drying oven for 8 hours, and then place them in the barrier layer extruder barrel of the five-layer plastic pipe extruder unit, PP-R is placed in the inner layer extruder barrel and the outer protective layer extruder barrel of the unit, and the hot melt adhesive is placed in the adhesive layer extruder barrel of the unit to prepare a new MXD6 / EVOH / PP-R alloy oxygen-barrier PP-R pipe. Among them, the extrusion process conditions of the inner working pipe are 190℃ and the screw speed is 20r / min, and the extrusion process conditions of the nylon alloy barrier layer are 240℃ and the screw speed is 35r / min.

[0094] Example 5: Five-layer structure

[0095] The barrier layer is MXD6 / EVOH / PP-R alloy, and the formula is as follows:

[0096] 80 parts of nylon MXD6, 1 part of EVOH, 19 parts of PP-R, 12 parts of maleic anhydride grafted polypropylene compatibilizer, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.1 parts of antioxidant 330.

[0097] The hot melt adhesive is maleic anhydride grafted polypropylene, and the maleic anhydride grafting rate is 1.2-1.3%.

[0098] The steps for pipe preparation are as follows:

[0099] Step 1: Dry MXD6 and EVOH in an electric hot air drying oven at 90°C for 8 hours and use them immediately;

[0100] Step 2: Mix the raw materials in the above ratio at room temperature for 10 minutes using a high-speed mixer; and prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 20r / min, the temperatures of each section of the barrel are set to 200, 220, 240, 250, and 230°C, and the melt temperature is 250°C.

[0101] Step 3: Place the MXD6 / EVOH / PP-R alloy pellets prepared by granulation into a 90℃ electric heating blast drying oven for 8 hours, and then place them in the barrier layer extruder barrel of the five-layer plastic pipe extruder unit, PP-R is placed in the inner layer extruder barrel and the outer protective layer extruder barrel of the unit, and the hot melt adhesive is placed in the adhesive layer extruder barrel of the unit to prepare a new MXD6 / EVOH / PP-R alloy oxygen-barrier PP-R pipe. Among them, the extrusion process conditions of the inner working pipe are 190℃ and the screw speed is 20r / min, and the extrusion process conditions of the nylon alloy barrier layer are 240℃ and the screw speed is 35r / min.

[0102] Example 6: Five-layer structure

[0103] The barrier layer is MXD6 / EVOH / PP-R alloy, and the formula is as follows:

[0104] 20 parts of nylon MXD6, 30 parts of EVOH, 50 parts of PP-R, 12 parts of maleic anhydride grafted polypropylene compatibilizer, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.1 parts of antioxidant 330.

[0105] The hot melt adhesive is maleic anhydride grafted polypropylene, and the maleic anhydride grafting rate is 1.2-1.3%.

[0106] The steps for pipe preparation are as follows:

[0107] Step 1: Dry MXD6 and EVOH in an electric hot air drying oven at 90°C for 8 hours and use them immediately;

[0108] Step 2: Mix the raw materials in the above ratio at room temperature for 10 minutes using a high-speed mixer; and prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 20r / min, the temperatures of each section of the barrel are set to 200, 220, 240, 250, and 230°C, and the melt temperature is 250°C.

[0109] Step 3: Place the MXD6 / EVOH / PP-R alloy pellets prepared by granulation into a 90℃ electric heating blast drying oven for 8 hours, and then place them in the barrier layer extruder barrel of the five-layer plastic pipe extruder unit, PP-R is placed in the inner layer extruder barrel and the outer protective layer extruder barrel of the unit, and the hot melt adhesive is placed in the adhesive layer extruder barrel of the unit to prepare a new MXD6 / EVOH / PP-R alloy oxygen-barrier PP-R pipe. Among them, the extrusion process conditions of the inner working pipe are 190℃ and the screw speed is 20r / min, and the extrusion process conditions of the nylon alloy barrier layer are 240℃ and the screw speed is 35r / min.

[0110] Example 7: Three-layer structure

[0111] The barrier layer is MXD6 / EVOH / PP-R alloy, and the formula is as follows:

[0112] 35 parts of nylon MXD6, 35 parts of EVOH, 30 parts of PP-R, 10 parts of maleic anhydride grafted polypropylene compatibilizer, 0.2 parts of antioxidant 1010, and 0.2 parts of antioxidant 168.

[0113] The hot melt adhesive is maleic anhydride grafted polypropylene, and the maleic anhydride grafting rate is 0.6-0.8%.

[0114] The steps for pipe preparation are as follows:

[0115] Step 1: Dry MXD6 and EVOH in an electric hot air drying oven at 90°C for 8 hours and use them immediately;

[0116] Step 2: Mix the raw materials in the above ratio at room temperature for 10 minutes using a high-speed mixer; and prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 20r / min, the temperatures of each section of the barrel are set to 200, 220, 240, 250, and 230°C, and the melt temperature is 250°C.

[0117] Step 3: Place the MXD6 / EVOH / PP-R alloy pellets prepared by granulation into a 90°C electric heating blast drying oven for 8 hours, then place them in the barrier layer extruder barrel of the three-layer plastic pipe extrusion unit, place PP-R in the inner layer extruder barrel of the unit, and place the hot melt adhesive in the adhesive layer extruder barrel of the unit to prepare a three-layer MXD6 / EVOH / PP-R alloy oxygen-barrier PP-R pipe. Among them, the extrusion process conditions of the inner working pipe are 190°C and the screw speed is 20r / min, and the extrusion process conditions of the nylon alloy barrier layer are 240°C and the screw speed is 33r / min.

[0118] Example 8: Three-layer structure

[0119] The barrier layer is MXD6 / EVOH / PE-RT alloy, and the formula is as follows:

[0120] 40 parts of nylon MXD6, 40 parts of EVOH, 20 parts of PE-RT, 11 parts of maleic anhydride grafted polypropylene compatibilizer, 0.2 parts of antioxidant 1010, 0.2 parts of antioxidant 168, and 0.1 parts of antioxidant 330.

[0121] The hot melt adhesive is maleic anhydride grafted polyethylene, and the maleic anhydride grafting rate is 0.8-1.0%.

[0122] The steps for pipe preparation are as follows:

[0123] Step 1: Dry MXD6 and EVOH in an electric hot air drying oven at 90°C for 8 hours and use them immediately;

[0124] Step 2: Mix the raw materials in the above ratio at room temperature for 10 minutes using a high-speed mixer; prepare nylon alloy pellets using a twin-screw extruder granulator. The speed of the granulating screw is 15r / min, the temperatures of each section of the barrel are set to 200, 220, 240, 250, 230°C, and the melt temperature is 250°C.

[0125] Step 3: Place the MXD6 / EVOH / PE-RT alloy pellets prepared by granulation in a 90°C electric heating blast drying oven for 8 hours, then place them in the barrier layer extruder barrel of the three-layer plastic pipe extrusion unit, place PE-RT in the inner layer extruder barrel of the unit, and place the hot melt adhesive in the adhesive layer extruder barrel of the unit to prepare a three-layer MXD6 / EVOH / PE-RT alloy oxygen-barrier PE-RT pipe. Among them, the extrusion process conditions of the inner working pipe are 200°C and the screw speed is 20r / min, and the extrusion process conditions of the nylon alloy barrier layer are 250°C and the screw speed is 31r / min.

[0126] The performance comparison data of Examples 1-8 and Comparative Examples 1-5 are shown in Table 1 below. The oxygen barrier performance of Examples 1-8 is better than that of Comparative Examples 3-5, and is not inferior to that of Comparative Examples 1 and 2. However, its compressive cracking performance, hot water hydrostatic performance and hot water immersion resistance are significantly better than those of Comparative Examples 1 and 2.

[0127] Table 1 Performance test data

[0128]

[0129]

Claims

1. A nylon alloy oxygen barrier composite tube, characterized in that It comprises a working tube (1), wherein a nylon alloy barrier layer (3) is provided on the outer surface of the working tube (1), and a first hot melt adhesive layer (2) is provided between the nylon alloy barrier layer (3) and the working tube (1).

2. A nylon alloy oxygen barrier composite tube according to claim 1, characterized in that It comprises an outer protective layer (4), the outer surface of the nylon alloy barrier layer (3) is provided with the outer protective layer (4), and a second hot melt adhesive layer (6) is provided between the outer protective layer (4) and the nylon alloy barrier layer (3).

3. A nylon alloy oxygen-barrier composite tube according to claim 1 or 2, characterized in that The working tube (1) is a PE-RT I type tube, a PE-RT II type tube or a PP-R tube; the nylon alloy of the nylon alloy barrier layer (3) is a semi-aromatic nylon alloy; specifically, MXD6 / PE-RT alloy, MXD6 / EVOH / PE-RT alloy, MXD6 / PP-R alloy or MXD6 / EVOH / PP-R alloy.

4. The nylon alloy oxygen barrier composite tube according to claim 3, characterized in that The nylon alloy is composed of the following raw materials in parts by weight composition: 20-80 parts of nylon, 1-50 parts of EVOH, 19-50 parts of polyolefin resin, 5-20 parts of compatibilizer, and 0.2-0.5 parts of antioxidant.

5. The nylon alloy oxygen barrier composite tube according to claim 4, characterized in that The nylon is MXD6; the EVOH is an ethylene-vinyl alcohol copolymer with an ethylene content of 32 mol%-44 mol%; the compatibilizer is maleic anhydride grafted polyethylene or maleic anhydride grafted polypropylene, and the maleic anhydride grafting rate is 0.8%-2.0%; the antioxidant is one or more of antioxidant 1010, antioxidant 168, and antioxidant 330; and the polyolefin resin is PE-RT or PP-R.

6. The nylon alloy oxygen barrier composite tube according to claim 2, characterized in that The first hot melt adhesive layer (2) and the second hot melt adhesive layer (6) are maleic anhydride grafted polyethylene or maleic anhydride grafted polypropylene, and the maleic anhydride grafting rate is 0.2%-2.0%; the outer protective layer (4) is PE-RT I type, PE-RT II type or PP-R.

7. A method for preparing a nylon alloy oxygen-barrier composite tube as claimed in any one of claims 1 to 6, characterized in that The steps include: Step 1: First, pre-treat the nylon alloy raw material; Step 2: firstly, using a high-speed mixer to mix the nylon alloy raw materials pretreated in step 1 in proportion at room temperature, and then using a twin-screw extruder granulator to prepare nylon alloy pellets; Step 3: First dry the nylon alloy pellets prepared in step 2, and then place them in the barrier layer extruder barrel of the extruder unit, and place the hot melt adhesive in the adhesive layer extruder barrel of the unit to obtain a nylon alloy oxygen-barrier composite tube.

8. The method for preparing the nylon alloy oxygen-barrier composite tube according to claim 7, characterized in that Step 1: When EVOH < 1 part, dry the nylon in an electric hot air drying oven at 90-110℃ for 6-10 hours and use it immediately; when 1≤EVOH≤50 parts, dry the nylon and EVOH in an electric hot air drying oven at 90-110℃ for 6-10 hours and use it immediately; Step 2: The speed of the granulating screw is 20-30 r / min, the temperatures of each section of the barrel are set to 200, 230, 250, 270, 240°C, and the melt temperature is 250°C.

9. The method for preparing the nylon alloy oxygen-barrier composite tube according to claim 7, characterized in that Step 3: firstly put the nylon alloy pellets prepared in step 2 into an electric heating blast drying oven at 90-110°C for 6-10h, and then put them into the barrier layer extruder barrel of the five-layer plastic pipe extrusion unit, put PE-RT or PP-R into the inner layer extruder barrel and the outer protective layer extruder barrel of the unit, and put the hot melt adhesive into the adhesive layer extruder barrel of the unit to prepare a five-layer new nylon alloy oxygen barrier tube; Among them, the extrusion process conditions of the inner working tube are 150-210°C, the screw speed is 20-28r / min, and the extrusion process conditions of the nylon alloy barrier layer are 200-300°C, and the screw speed is 30-50r / min.

10. The method for preparing the nylon alloy oxygen-barrier composite tube according to claim 7, characterized in that Step three: first put the nylon alloy pellets prepared in step two into an electric hot air drying oven at 90-110°C for 6-10h, then place it in the barrier layer extruder barrel of the three-layer plastic pipe extrusion unit, place PE-RT or PP-R in the inner working tube extruder barrel of the unit, and place the hot melt adhesive in the adhesive layer extruder barrel of the unit to prepare a three-layer new nylon alloy oxygen barrier tube; wherein, the extrusion process conditions of the inner working tube are 150-210°C, the screw speed is 20-28r / min, the extrusion process conditions of the nylon alloy barrier layer are 200-300°C, and the screw speed is 30-50r / min.

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