Polypropylene composite material for laser welding and method for producing the same

Abstract

The present application relates to a kind of polypropylene composite materials for laser welding and its preparation method.The composite material component includes by weight portion: polypropylene 39-80 parts, inorganic filler 10-30 parts, toughening agent 5-25 parts, laser welding modifier 5-15 parts, antioxidant 0.2-0.5 parts, weathering agent 0.2-0.5 parts, lubricant 0.1-0.3 parts, black mother 0.5-1.0 parts.The composite material and nylon welding have good welding strength.

Description

Technical Field

[0001] This invention belongs to the field of laser welding materials and their preparation methods, and particularly relates to a polypropylene composite material for laser welding and its preparation method. Background Technology

[0002] With the development of welding technology, laser welding is gradually being accepted and increasingly used. This welding method eliminates VOC emissions from adhesives, is less prone to weld marks, and offers advantages such as non-contact operation, high flexibility, short cycle time, high welding precision, and high automation. In the automotive industry, laser welding is increasingly being considered for joining plastic parts; for example, the welding of radar brackets, air duct brackets, and bumpers has already been applied, and laser welding of the inner and outer panels of all-plastic tailgates is under development. However, these parts are all made of polypropylene. Laser welding between polypropylene parts can achieve high weld strength as long as the light transmittance is high. However, some automotive parts are made of nylon. When welding nylon and polypropylene, high weld strength is usually not achieved due to their poor compatibility. Therefore, it is necessary to develop a polypropylene material that can be laser-welded with nylon to broaden the application of laser welding.

[0003] In their article "Research on Laser Transmission Welding Process of Modified Polypropylene and Nylon 66", Jiang Hairong et al. mentioned obtaining maleic anhydride-grafted polypropylene by grafting maleic anhydride onto the side chains of polypropylene, thereby achieving good welding between maleic anhydride-grafted polypropylene and nylon 6. However, it is well known that automotive modified polypropylene usually involves filler-toughened modified polypropylene. Maleic anhydride-grafted polypropylene, due to its poor flowability, poor compatibility with the toughening agent POE, and poor heat aging and weather resistance, is usually only added in small amounts as an auxiliary raw material and is not suitable to replace polypropylene as the main raw material for filler-toughened modified polypropylene, thus greatly limiting its application. Chinese patent CN1839031A discloses the preparation of laser-welded products by adding modified polyolefins (such as maleic anhydride-grafted polypropylene) to polyolefins. However, the compatibility between the modified polyolefin and polypropylene is not particularly good, which will cause significant loss of the mechanical properties of the material. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a polypropylene composite material for laser welding and its preparation method, so as to overcome the defects of the prior art that maleic anhydride grafted polypropylene is not suitable as the main raw material for filling toughened modified polypropylene materials and causes a large loss of mechanical properties when used as an auxiliary raw material.

[0005] This invention provides a polypropylene composite material for laser welding. The composite material comprises, by weight, 39-80 parts of polypropylene, 10-30 parts of inorganic filler, 5-25 parts of toughening agent, 5-15 parts of laser welding modifier, 0.2-0.5 parts of antioxidant, 0.2-0.5 parts of weathering agent, 0.1-0.3 parts of lubricant, and 0.5-1.0 parts of black masterbatch, wherein the laser welding modifier is a block copolymer of polypropylene and polyamide.

[0006] The polypropylene is at least one of homopolymer polypropylene and copolymer polypropylene, and the polypropylene melt index is 1-100 g / 10 min (test conditions are 230℃, 2.16 kg).

[0007] The inorganic filler is at least one of talc, calcium carbonate, wollastonite, mica, barium sulfate, and magnesium sulfate whiskers; the particle size of the inorganic filler is 1-10 μm.

[0008] The toughening agent is a copolymer of ethylene and an α-olefin containing 3-10 carbon atoms, and the melt index of the toughening agent is 0.5-30 g / 10 min (test conditions are 190℃, 2.16 kg).

[0009] The antioxidant is at least one of phenolic antioxidants, amine antioxidants, phosphite antioxidants, and hindered phenolic antioxidants.

[0010] The weathering agent is at least one of hindered amine light stabilizers, benzotriazole light stabilizers, benzophenone light stabilizers, and triazine benzylidene malonate light stabilizers.

[0011] The lubricant is at least one of amide lubricants, stearic acid lubricants, fatty acid lubricants, and ester lubricants.

[0012] This invention also provides a method for preparing a polypropylene composite material for laser welding, comprising:

[0013] Polypropylene, inorganic fillers, toughening agents, laser welding modifiers, antioxidants, weathering agents, lubricants, and black masterbatch are mixed, and the mixed raw materials are added to a twin-screw extruder for melt blending, extrusion granulation, and polypropylene composite material for laser welding is obtained.

[0014] The block copolymer of polypropylene and polyamide is generated by reacting bi-carboxylated polypropylene and polyamide under the action of a catalyst.

[0015] The block copolymer of polypropylene and polyamide is prepared by adding polyamide, bi-carboxylated polypropylene and catalyst to toluene solution, refluxing under nitrogen protection for 24-30 h, cooling, precipitating in methanol, washing, and drying to obtain the product. The weight ratio of amino groups in polyamide to carboxyl groups in bi-carboxylated polypropylene is 2-2.5:1, the mass ratio of catalyst to polyamide is 92-97:3-8, and the viscosity of polyamide is 5000-70000 mpa.s / 40℃, preferably 10000-50000 mpa.s / 40℃.

[0016] The washing process involves sequentially washing with methanol and acetone.

[0017] The preparation method of the double-ended carboxyl polypropylene is as follows: polypropylene and concentrated nitric acid are mixed in a ratio of 100g:450-550ml, heated to 120-140℃, stirred for 12-20h, washed, and dried to obtain the product, wherein the molecular weight of polypropylene is 1000-6000g / mol, preferably 3000-5000g / mol.

[0018] The washing process involves sequentially washing with water and acetone.

[0019] The mixing time is 1-2 minutes, and the mixing speed is 600-1000 revolutions per minute.

[0020] The melt blending temperature is 180-230℃.

[0021] The present invention also provides an application of polypropylene composite material for laser welding in laser welding.

[0022] Beneficial effects

[0023] The polypropylene-polyamide block copolymer added in this invention not only ensures good compatibility between the filled modified polypropylene material and nylon 6, but also exhibits good compatibility between the block copolymer and polypropylene itself. This allows the filled modified polypropylene material to fuse well with nylon 6 during the laser welding melting process, improving weld strength, while having minimal impact on the mechanical properties of the polypropylene material. Furthermore, adding the polypropylene-polyamide block copolymer to traditional modified polypropylene materials does not affect the material's filling, toughening, or other multi-dimensional design aspects, and its application scope covers all types of modified polypropylene materials. Detailed Implementation

[0024] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0025] The raw materials used in the embodiments and comparative examples of this invention are the following raw materials, but are not limited to the following raw materials:

[0026] PP BX3920: Copolymer polypropylene, SK Corporation, South Korea;

[0027] PP K9017: Copolymer polypropylene, Formosa Chemicals & Fibre Corporation, Taiwan;

[0028] AH-3000N9: Talc, 3000 mesh, Liaoning Aihai;

[0029] POE 8137: Ethylene-octene copolymer, Dow Chemical;

[0030] Antioxidant 1010: Main antioxidant, BASF;

[0031] Antioxidant 168: A co-antioxidant, BASF;

[0032] UV-3808PP5: Weather resistant agent, Cytec Chemicals;

[0033] TR451: Lubricant, Sruktol Corporation, USA;

[0034] PE2772: Black masterbatch, Cabot;

[0035] Maleic anhydride-grafted modified polypropylene wax: Clariant AR504.

[0036] The preparation method of the block copolymer of polypropylene and polyamide in this invention is as follows: polyamide (Changzhou Shanfeng Chemical, SF-650-200, viscosity 20000 mpa.s / 40℃) and carboxyl-terminated polypropylene are weighed according to an amino to carboxyl ratio of 2.2:1, with a total weight of 50g. The catalyst p-toluenesulfonic acid is weighed according to a mass ratio of 95:5 with polyamide. The mixture is placed in 500mL of toluene solution and heated under reflux for 24h under nitrogen protection. The reaction product is then cooled and precipitated in methanol, washed successively with methanol and acetone, and then dried in a vacuum oven to obtain the block copolymer.

[0037] The preparation method of double-carboxylated polypropylene is as follows: 100g of polypropylene (Korea COSCHEM, CS-53NC, molecular weight 3500g / mol) and 500mL of 70% concentrated nitric acid are placed in a container, heated to 130℃, and stirred for 16h. The reaction product is washed with water and acetone successively, and then dried in a vacuum oven.

[0038] Example 1

[0039] A polypropylene composite material for laser welding, comprising the following components by weight: 28.6 parts BX3920, 35 parts K9017, 12 parts AH-3000N9, 18 parts POE 8137, 5 parts a block copolymer of polypropylene and polyamide, 0.15 parts antioxidant 1010, 0.15 parts antioxidant 168, 0.2 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772.

[0040] The preparation method of the above composite material is as follows: all the above components are mixed at a mixing speed of 600 rpm for 2 min. The mixed raw material is added to the main feed port of a twin-screw extruder. The temperatures of each section are 180℃, 200℃, 220℃, 230℃, 220℃, and 210℃. The mixture is then melt-blended, extruded, and granulated to obtain a polypropylene composite material for laser welding.

[0041] Example 2

[0042] A polypropylene composite material for laser welding, comprising the following components by weight: 23.6 parts BX3920, 35 parts K9017, 12 parts AH-3000N9, 18 parts POE 8137, 10 parts a block copolymer of polypropylene and polyamide, 0.15 parts antioxidant 1010, 0.15 parts antioxidant 168, 0.2 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772.

[0043] The preparation method of the above composite material is as follows: all the above components are mixed at a mixing speed of 1000 rpm for 1 min. The mixed raw material is added to the main feed port of a twin-screw extruder. The temperatures of each section are 180℃, 200℃, 210℃, 220℃, 230℃, and 220℃. The mixture is melt-blended, extruded and granulated to obtain a polypropylene composite material for laser welding.

[0044] Example 3

[0045] A polypropylene composite material for laser welding, comprising the following components by weight: 23.6 parts BX3920, 30 parts K9017, 12 parts AH-3000N9, 18 parts POE 8137, 15 parts a block copolymer of polypropylene and polyamide, 0.15 parts antioxidant 1010, 0.15 parts antioxidant 168, 0.2 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772.

[0046] The preparation method of the above composite material is as follows: all the above components are mixed at a mixing speed of 1000 rpm for 1 min. The mixed raw material is added to the main feed port of a twin-screw extruder. The temperatures of each section are 180℃, 190℃, 210℃, 220℃, 220℃, and 210℃. The mixture is then melt-blended, extruded, and granulated to obtain a polypropylene composite material for laser welding.

[0047] Example 4

[0048] A polypropylene composite material for laser welding, comprising the following components by weight: 29.4 parts BX3920, 20 parts K9017, 21 parts AH-3000N9, 23 parts POE 8137, 5 parts a block copolymer of polypropylene and polyamide, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 0.3 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772.

[0049] The preparation method of the above composite material is as follows: all the above components are mixed at a mixing speed of 800 rpm for 1 min. The mixed raw material is added to the main feed port of a twin-screw extruder. The temperatures of each section are 180℃, 200℃, 220℃, 230℃, 220℃, and 210℃. The mixture is then melt-blended, extruded, and granulated to obtain a polypropylene composite material for laser welding.

[0050] Example 5

[0051] A polypropylene composite material for laser welding, comprising the following components by weight: 24.4 parts BX3920, 20 parts K9017, 21 parts AH-3000N9, 23 parts POE 8137, 10 parts a block copolymer of polypropylene and polyamide, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 0.3 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772.

[0052] The preparation method of the above composite material is the same as that in Example 4.

[0053] Example 6

[0054] A polypropylene composite material for laser welding, comprising the following components by weight: 24.4 parts BX3920, 15 parts K9017, 21 parts AH-3000N9, 23 parts POE 8137, 15 parts a block copolymer of polypropylene and polyamide, 0.2 parts antioxidant 1010, 0.2 parts antioxidant 168, 0.3 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772.

[0055] The preparation method of the above composite material is the same as that in Example 4.

[0056] Example 7

[0057] A polypropylene composite material for laser welding, comprising the following components by weight: 21.1 parts BX3920, 32 parts K9017, 30 parts AH-3000N9, 10 parts POE 8137, 5 parts a block copolymer of polypropylene and polyamide, 0.2 parts antioxidant 1010, 0.3 parts antioxidant 168, 0.5 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772.

[0058] The preparation method of the above composite material is as follows: all the above components are mixed at a mixing speed of 700 rpm for 1.5 min. The mixed raw material is added to the main feed port of a twin-screw extruder. The temperatures of each section are 180℃, 210℃, 230℃, 230℃, 230℃, and 220℃. The mixture is then melt-blended, extruded, and granulated to obtain a polypropylene composite material for laser welding.

[0059] Example 8

[0060] A polypropylene composite material for laser welding, comprising the following components by weight: 18.1 parts BX3920, 30 parts K9017, 30 parts AH-3000N9, 10 parts POE 8137, 10 parts a block copolymer of polypropylene and polyamide, 0.2 parts antioxidant 1010, 0.3 parts antioxidant 168, 0.5 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772.

[0061] The preparation method of the above composite material is the same as that in Example 7.

[0062] Example 9

[0063] A polypropylene composite material for laser welding, comprising the following components by weight: 15.1 parts BX3920, 28 parts K9017, 30 parts AH-3000N9, 10 parts POE 8137, 15 parts a block copolymer of polypropylene and polyamide, 0.2 parts antioxidant 1010, 0.3 parts antioxidant 168, 0.5 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772.

[0064] The preparation method of the above composite material is the same as that in Example 7.

[0065] Example 10

[0066] A polypropylene composite material for laser welding, comprising the following components by weight: 38.6 parts BX3920, 38 parts K9017, 12 parts AH-3000N9, 5 parts POE 8137, 5 parts a block copolymer of polypropylene and polyamide, 0.15 parts antioxidant 1010, 0.15 parts antioxidant 168, 0.2 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772.

[0067] The preparation method of the above composite material is the same as that in Example 1.

[0068] Comparative Example 1

[0069] This comparative example provides a polypropylene composite material and its preparation method. According to Example 1, the weight parts of BX3920 in the composite material are changed to 33.6 parts, and no block copolymer of polypropylene and polyamide is added. The rest are the same as in Example 1.

[0070] Comparative Example 2

[0071] This comparative example provides a polypropylene composite material and its preparation method. According to Example 4, the weight parts of BX3920 in the composite material are changed to 35.4 parts, no block copolymer of polypropylene and polyamide is added, the weight parts of AH-3000N9 are changed to 20 parts, and the rest are the same as in Example 4.

[0072] Comparative Example 3

[0073] This comparative example provides a polypropylene composite material and its preparation method. According to Example 7, the weight parts of BX3920 in the composite material are changed to 26.1 parts, and no block copolymer of polypropylene and polyamide is added. The rest are the same as in Example 7.

[0074] Comparative Example 4

[0075] According to Chinese Patent CN1839031A, this comparative example provides a polypropylene composite material. The components of this composite material, by weight, include: 28.6 parts BX3920, 35 parts K9017, 12 parts AH-3000N9, 18 parts POE 8137, 5 parts maleic anhydride-grafted modified polypropylene wax, 0.15 parts antioxidant 1010, 0.15 parts antioxidant 168, 0.2 parts UV-3808PP5, 0.2 parts TR451, and 0.7 parts PE2772. The preparation method of this composite material is the same as in Example 1.

[0076] The composite materials from Examples 1-10 and Comparative Examples 1-4 were injection molded into standard ISO mechanical specimens under the same injection molding process (a conventional injection molding process in the art) for mechanical property testing (tested according to ISO standard methods). These specimens, along with selected nylon 6 material (Xinhui Meda PA6 M2800), were injection molded into specimens with dimensions of 150mm × 15mm × 2mm. Laser welding was then performed using a Han's Laser welding machine (WFD120 W-PCTS333 SP) (welding process: laser wavelength 915nm, power 20W, welding speed 20mm / s, where nylon 6 is the light-transmitting layer and the polypropylene composite material of this invention is the light-absorbing layer). The welding force was then tested on a tensile testing machine (tensile speed 50mm / min). The test results are shown in Table 1.

[0077] Table 1

[0078]

[0079] As shown in Table 1, in Comparative Example 1, the composite material without the addition of the polypropylene-polyamide block copolymer exhibits significantly lower weld strength than Example 1, slightly lower tensile strength and flexural modulus, and slightly higher notched impact strength. In Comparative Example 2, the composite material without the addition of the polypropylene-polyamide block copolymer exhibits significantly lower weld strength than Example 4, slightly lower tensile strength and flexural modulus, and slightly higher notched impact strength. In Comparative Example 3, the composite material without the addition of the polypropylene-polyamide block copolymer exhibits significantly lower weld strength than Example 7, slightly lower tensile strength and flexural modulus, and slightly higher notched impact strength. Therefore, regardless of the talc content, adding the polypropylene-polyamide block copolymer to the composite material significantly improves weld strength, while also increasing tensile strength and flexural modulus to some extent, and slightly decreasing impact strength. In Comparative Example 4, the composite material with maleic anhydride-grafted modified polypropylene wax exhibited slightly weaker welding strength compared to the composite material with the polypropylene-polyamide block copolymer of this invention. Furthermore, its addition significantly reduced the tensile strength, flexural modulus, and notched impact strength of the simply supported beam. Moreover, when the amount of polypropylene-polyamide block copolymer added to the composite material was 10 parts, its laser welding strength increased by more than 2 times compared to the composite material without added polypropylene-polyamide block copolymer; while when the amount added was 15 parts, the laser welding strength increased by more than 3 times.

Claims

1. A polypropylene composite material for laser welding, characterized in that, The composite material components, by weight, include: 39-80 parts polypropylene, 10-30 parts inorganic filler, 5-25 parts toughening agent, 10-15 parts laser welding modifier, 0.2-0.5 parts antioxidant, 0.2-0.5 parts weathering agent, 0.1-0.3 parts lubricant, and 0.5-1.0 parts black masterbatch, wherein the laser welding modifier is a block copolymer of polypropylene and polyamide; The block copolymer of polypropylene and polyamide is prepared by adding polyamide and bicarboxylated polypropylene to toluene solution, refluxing under nitrogen protection for 24-30 h, cooling, precipitating in methanol, washing, and drying to obtain the product, wherein the weight ratio of amino groups in polyamide to carboxyl groups in bicarboxylated polypropylene is 2-2.5:

1. The polyamide has a viscosity of 5000-70000 mpa.s / 40℃.

2. The composite material according to claim 1, characterized in that, The polypropylene is at least one of homopolymer polypropylene and copolymer polypropylene, and the polypropylene melt index is 1-100 g / 10 min; the inorganic filler is at least one of talc, calcium carbonate, wollastonite, mica, barium sulfate, and magnesium sulfate whiskers; the particle size of the inorganic filler is 1-10 μm.

3. The composite material according to claim 1, characterized in that, The toughening agent is a copolymer of ethylene and an α-olefin containing 3-10 carbon atoms, and the toughening agent melt index is 0.5-30 g / 10 min; the antioxidant is at least one of phenolic antioxidants, amine antioxidants, phosphite antioxidants, and hindered phenolic antioxidants.

4. The composite material according to claim 1, characterized in that, The weathering agent is at least one of hindered amine light stabilizers, benzotriazole light stabilizers, benzophenone light stabilizers, and triazine benzylidene malonate light stabilizers.

5. The composite material according to claim 1, characterized in that, The lubricant is at least one of amide lubricants, stearic acid lubricants, fatty acid lubricants, and ester lubricants.

6. The composite material according to claim 1, characterized in that, The preparation method of the double-ended carboxyl polypropylene is as follows: polypropylene and concentrated nitric acid are mixed in a ratio of 100g:450-550ml, heated to 120-140℃, stirred for 12-20h, washed, and dried to obtain the product, wherein the molecular weight of polypropylene is 1000-6000g / mol.

7. A method for preparing the composite material as described in claim 1, comprising: Polypropylene, inorganic fillers, toughening agents, laser welding modifiers, antioxidants, weathering agents, lubricants, and black masterbatch are mixed, and the mixed raw materials are added to a twin-screw extruder for melt blending, extrusion granulation, and polypropylene composite material for laser welding is obtained.

8. The method according to claim 7, characterized in that, The mixing time is 1-2 minutes; the melt blending temperature is 180-230℃.

9. An application of the composite material as described in claim 1 in laser welding.

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