A laser transmission modified polypropylene and its application

Abstract

This invention provides a laser transmission modified polypropylene and its applications, belonging to the field of polymer materials technology. The laser transmission modified polypropylene provided by this invention is prepared from raw materials comprising the following mass percentages: 70-85% polypropylene, 10-25% talc, and 3-5% magnesium sulfate whiskers. This invention utilizes magnesium sulfate whiskers to improve the rigidity and light transmittance of the laser transmission modified polypropylene, and utilizes talc to improve dimensional stability. By limiting the addition amounts of magnesium sulfate whiskers and talc, the magnesium sulfate whiskers and talc exert a synergistic effect, thereby giving the laser transmission modified polypropylene high laser transmittance, high strength, and high dimensional stability. The laser transmission modified polypropylene provided by this invention has a 1.5mm 925nm transmittance of over 50%; a shrinkage ratio perpendicular to the flow direction / flow direction of less than 1.1%, high dimensional stability; and a flexural modulus exceeding 3000MPa.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a laser transmission modified polypropylene and its applications. Background Technology

[0002] Currently, automotive parts involving body panels are primarily joined by directly screwing the two halves together, a method that is inefficient and does not align with the trend towards automation to improve production efficiency. Laser welding technology, especially synchronous infrared laser welding, is an emerging welding technology in the automotive industry. It uses the heat generated by a laser beam to melt the plastic contact surfaces, thereby bonding the parts together. Laser welding technology typically requires one of the two plastic parts being welded to transmit the laser beam while the other absorbs it. While absorbing plastic parts are easier to achieve, high-transmittance plastic parts, due to the combined requirements of light transmittance and intensity, limit the application of laser welding technology in automotive parts.

[0003] Existing automotive parts, such as air conditioner housings, are mainly made of talc-modified polypropylene. Talc-modified polypropylene has a good balance of rigidity and toughness. However, its laser transmittance is only about 40% at a thickness of 1.5mm, while laser welding requires a transmittance of over 50% at the same thickness to meet the requirements of the most efficient synchronous infrared laser welding. Although glass fiber reinforced polypropylene has good light transmittance, its significant shrinkage orientation makes it unsuitable for use in parts with low wall thickness.

[0004] Therefore, providing a laser-transmittance modified polypropylene with high laser transmittance, high strength, and high dimensional stability has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to provide a laser transmission modified polypropylene and its applications. The laser transmission modified polypropylene provided by this invention has high laser transmittance, high strength, and high dimensional stability.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a laser transmission modified polypropylene, prepared from raw materials comprising the following mass percentages: 70-85% polypropylene, 10-25% talc, and 3-5% magnesium sulfate whiskers.

[0008] Preferably, the laser transmission modified polypropylene is prepared from raw materials comprising the following mass percentages: 75-85% polypropylene, 16-20% talc, and 3.5-4.5% magnesium sulfate whiskers.

[0009] Preferably, the raw materials for preparing the laser transmission modified polypropylene further include 0.05-0.1% nucleating agent and 0.4-0.5% antioxidant.

[0010] Preferably, the polypropylene is homopolymer polypropylene or copolymer polypropylene.

[0011] Preferably, the melt index of the polypropylene is 10-30 g / 10 min.

[0012] Preferably, the talc powder has a D50 particle size of 4–10 μm and an aspect ratio of 10–30.

[0013] Preferably, the SiO2 content in the talc powder is >58%.

[0014] Preferably, the aspect ratio of the magnesium sulfate whiskers is 20 to 30.

[0015] Preferably, the refractive index of the magnesium sulfate whiskers is 1.52 to 1.54.

[0016] The present invention also provides the application of the laser transmission modified polypropylene described in the above technical solution in laser welding of low wall thickness automotive parts.

[0017] This invention provides a laser transmission modified polypropylene, prepared from raw materials comprising the following mass percentages: 70-85% polypropylene, 10-25% talc, and 3-5% magnesium sulfate whiskers. This invention utilizes magnesium sulfate whiskers to improve the rigidity and light transmittance of the laser transmission modified polypropylene, and talc to improve dimensional stability. By limiting the addition amounts of magnesium sulfate whiskers and talc, the two elements work synergistically, resulting in laser transmission modified polypropylene exhibiting high laser transmittance, high strength, and high dimensional stability. Example results show that the laser transmission modified polypropylene provided by this invention has a 1.5mm 925nm light transmittance of over 50%; a shrinkage ratio perpendicular to the flow direction / flow direction of less than 1.1%, exhibiting high dimensional stability; and a flexural modulus exceeding 3000MPa, demonstrating high laser transmittance, high strength, and high dimensional stability. Attached Figure Description

[0018] Figure 1 This is a physical image of the automotive air conditioning housing component prepared using the laser transmission modified polypropylene described in Example 1 of this invention.

[0019] Figure 2 The image shows a partial physical photograph of an automotive air conditioning housing component prepared using laser transmission modified polypropylene as described in Example 1 of this invention. Detailed Implementation

[0020] This invention provides a laser transmission modified polypropylene, prepared from raw materials comprising the following mass percentages: 70-85% polypropylene, 10-25% talc, and 3-5% magnesium sulfate whiskers.

[0021] The raw materials for preparing the laser transmission modified polypropylene of the present invention, by weight percentage, comprise 70-85% polypropylene, preferably 75-85%, and more preferably 80%. By setting the polypropylene content within the above range, the processability of the modified polypropylene can be guaranteed.

[0022] In this invention, the polypropylene is preferably homopolymer polypropylene or copolymer polypropylene; the melt index of the polypropylene is preferably 10-30 g / 10 min, more preferably 15-25 g / 10 min, and even more preferably 20 g / 10 min; the homopolymer polypropylene is suitable for automotive air conditioning housings; the copolymer polypropylene is suitable for automotive interior and exterior trim. By limiting the type of polypropylene and the melt index to the above ranges, this invention ensures that the modified polypropylene has good performance.

[0023] The raw materials for preparing the laser transmission modified polypropylene of the present invention, by weight percentage, include 10-25% talc, preferably 16-20%, and more preferably 16-18%. In the present invention, the talc provides rigidity and dimensional stability. By limiting the content of talc within the above range, the present invention can improve the rigidity and dimensional stability of the modified polypropylene.

[0024] In this invention, the D50 particle size of the talc powder is preferably 4–10 μm, more preferably 4–7 μm; the aspect ratio of the talc powder is preferably 10–30, more preferably 20–30. When the powder diameter of the talc powder is small, its light scattering and shielding effect is strong; as the particle size continues to increase, the shielding effect decreases; when the talc powder particle size is greater than 7 μm, there is a significant loss in the impact performance of polypropylene. This invention limits the particle size and aspect ratio of the talc powder to the above-mentioned ranges to provide good rigidity and dimensional stability for modified polypropylene.

[0025] In this invention, the SiO2 content in the talc powder is preferably >58%, more preferably 58-61%. Limiting the SiO2 content in the talc powder to the above range ensures that the refractive index of the talc powder is 1.54-1.57, thus avoiding a significant impact on the light transmittance of the modified polypropylene.

[0026] The raw materials for preparing the laser transmission modified polypropylene of the present invention, by weight percentage, include 3-5% magnesium sulfate whiskers, preferably 3.5-4.5%, more preferably 4%. In the present invention, the magnesium sulfate whiskers provide good rigidity and light transmittance. The present invention limits the content of magnesium sulfate whiskers to the above range, allowing it to be combined with talc to further improve the light transmittance and strength of the modified polypropylene.

[0027] In this invention, the aspect ratio of the magnesium sulfate whiskers is preferably 20-30, more preferably 25%; the refractive index of the magnesium sulfate whiskers is preferably 1.52-1.54, more preferably 1.53. Limiting the aspect ratio and refractive index of the magnesium sulfate whiskers to the above ranges in this invention can provide good rigidity and laser transmittance for modified polypropylene.

[0028] In this invention, the raw materials for preparing the laser transmission modified polypropylene preferably further include 0.05-0.1% nucleating agent and 0.4-0.5% antioxidant.

[0029] The raw materials for preparing the laser transmission modified polypropylene of the present invention preferably further include 0.05-0.1% nucleating agent by mass percentage, more preferably 0.08-0.1%. The present invention reduces the crystal size of polypropylene by adding a nucleating agent, thereby further improving the light transmittance of the modified polypropylene.

[0030] The present invention does not have any particular limitation on the type of nucleating agent, and any nucleating agent commonly used by those skilled in the art in modified polypropylene can be used.

[0031] The raw materials for preparing the laser transmission modified polypropylene of the present invention preferably further include 0.4-0.5% antioxidant, more preferably 0.45-0.5%, by weight percentage. The present invention prevents the aging of modified polypropylene by adding antioxidant.

[0032] The present invention does not have a special limitation on the type of antioxidant, and any antioxidant commonly used by those skilled in the art in modified polypropylene can be used.

[0033] This invention utilizes magnesium sulfate whiskers to improve the rigidity and light transmittance of laser-transmitted modified polypropylene, and uses talc to improve dimensional stability. By limiting the amount of magnesium sulfate whiskers and talc added, the magnesium sulfate whiskers and talc work synergistically, thereby enabling the laser-transmitted modified polypropylene to have high laser transmittance, high strength and high dimensional stability.

[0034] The present invention also provides the application of the laser transmission modified polypropylene described in the above technical solution in laser welding of low wall thickness automotive parts.

[0035] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0036] Example 1

[0037] A laser transmission modified polypropylene is prepared from the following raw materials in weight percentages: 79.5% polypropylene, 16% talc, 4% magnesium sulfate whiskers, and 0.5% antioxidant.

[0038] The polypropylene is homopolymer polypropylene with a melt index of 20 g / 10 min;

[0039] The talc powder has a D50 particle size of 5 μm and an aspect ratio of 10; the talc powder contains 59% SiO2.

[0040] The magnesium sulfate whiskers have an aspect ratio of 30 and a refractive index of 1.53.

[0041] Example 2

[0042] A laser transmission modified polypropylene is prepared from the following raw materials in weight percentages: 79.4% polypropylene, 16% talc, 4% magnesium sulfate whiskers, 0.1% nucleating agent and 0.5% antioxidant;

[0043] The polypropylene is homopolymer polypropylene with a melt index of 20 g / 10 min;

[0044] The talc powder has a D50 particle size of 6 μm and an aspect ratio of 20; the talc powder contains 59% SiO2.

[0045] The magnesium sulfate whiskers have an aspect ratio of 30 and a refractive index of 1.53.

[0046] The nucleating agent is NX8000;

[0047] The antioxidant is a mixture of antioxidant 1010 and antioxidant 168; the mass ratio of antioxidant 1010 to antioxidant 168 is 1:1.

[0048] Comparative Example 1

[0049] A laser transmission modified polypropylene is prepared from the following raw materials in weight percentages: 79.5% polypropylene, 20% magnesium sulfate whiskers and 0.5% antioxidant;

[0050] The polypropylene is homopolymer polypropylene with a melt index of 20 g / 10 min;

[0051] The magnesium sulfate whiskers have an aspect ratio of 30 and a refractive index of 1.53.

[0052] Comparative Example 2

[0053] A laser transmission modified polypropylene is prepared from the following raw materials in weight percentages: 79.5% polypropylene, 20% talc, and 0.5% antioxidant.

[0054] The polypropylene is homopolymer polypropylene with a melt index of 20 g / 10 min;

[0055] The talc powder has a D50 particle size of 5 μm and an aspect ratio of 10; the talc powder contains 59% SiO2.

[0056] Comparative Example 3

[0057] A laser transmission modified polypropylene is prepared from the following raw materials in weight percentages: 69.5% polypropylene, 27% talc, 3% magnesium sulfate whiskers and 0.5% antioxidant.

[0058] The polypropylene is homopolymer polypropylene with a melt index of 20 g / 10 min;

[0059] The talc powder has a D50 particle size of 5 μm and an aspect ratio of 10; the talc powder contains 59% SiO2.

[0060] The magnesium sulfate whiskers have an aspect ratio of 30 and a refractive index of 1.53.

[0061] Comparative Example 4

[0062] A laser transmission modified polypropylene is prepared from the following raw materials in weight percentages: 74.5% polypropylene, 17% talc, 8% magnesium sulfate whiskers and 0.5% antioxidant.

[0063] The polypropylene is homopolymer polypropylene with a melt index of 20 g / 10 min;

[0064] The talc powder has a D50 particle size of 5 μm and an aspect ratio of 10; the talc powder contains 59% SiO2.

[0065] The magnesium sulfate whiskers have an aspect ratio of 30 and a refractive index of 1.53.

[0066] The flexural modulus of the laser transmission modified polypropylene in Examples 1-2 and Comparative Examples 1-4 was tested using a universal tensile testing machine.

[0067] The shrinkage rates of laser-transmitted modified polypropylene in Examples 1-2 and Comparative Examples 1-4 were tested using a self-made micrometer gauge (a novel plastic shrinkage rate measuring instrument in Chinese Patent CN209707423U).

[0068] The transmittance of laser transmission modified polypropylene in Examples 1-2 and Comparative Examples 1-4 was tested using a near-infrared light meter.

[0069] The test results of flexural modulus, shrinkage rate, and light transmittance of laser transmission modified polypropylene in Examples 1-2 and Comparative Examples 1-4 are shown in Table 1:

[0070] Table 1. Flexural modulus, shrinkage rate, and light transmittance data of laser transmission modified polypropylene in Examples 1-2 and Comparative Examples 1-4.

[0071]

[0072] As can be seen from the data in Table 1, Comparative Example 1 omits talc powder compared to Example 1. Due to the needle-like shape of the whiskers and their strong orientation, the ratio of vertical shrinkage to flow shrinkage in Comparative Example 1 is significantly higher than that in Example 1, making the injection-molded parts prone to warping. Comparative Example 2 omits magnesium sulfate whiskers compared to Example 1. Because the physical form of talc powder is flake-like, it hinders laser transmission, resulting in low light transmittance, which does not meet the needs of efficient continuous production. The flexural modulus and light transmittance of Comparative Example 2 are significantly lower than those of Example 1. Comparative Example 3 changes the talc powder content compared to Example 1. Although a high talc powder content can significantly improve the flexural modulus and meet the rigidity requirements of injection-molded products, a high talc powder content further reduces light transmittance, which does not meet the needs of continuous production. The light transmittance of Comparative Example 3 is significantly lower than that of Example 1. Comparative Example 4 changes the magnesium sulfate whisker content compared to Example 1. Due to the strong orientation of magnesium sulfate whiskers, the ratio of vertical shrinkage to flow shrinkage in Comparative Example 4 is significantly higher than that in Example 1, making the injection-molded products prone to warping.

[0073] This invention utilizes magnesium sulfate whiskers to improve the rigidity and light transmittance of laser-modified polypropylene, and talc to enhance dimensional stability. By limiting the addition amounts of magnesium sulfate whiskers and talc, the two materials work synergistically, resulting in laser-modified polypropylene exhibiting high laser transmittance, high strength, and high dimensional stability. Example results show that the laser-modified polypropylene provided by this invention has a 1.5mm 925nm light transmittance of over 50%; a shrinkage ratio perpendicular to the flow direction / flow direction of less than 1.1%, exhibiting high dimensional stability; and a flexural modulus exceeding 3000MPa, demonstrating high laser transmittance, high strength, and high dimensional stability.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. Laser transmission modified polypropylene, which is prepared from the following raw materials in mass percentage: polypropylene 70-85%, talcum powder 10-25%, magnesium sulfate whisker 3-5%, nucleating agent 0.05-0.1%, and antioxidant 0.4-0.5%. The polypropylene is homopolymer polypropylene. The talcum powder has a D50 particle size of 4-10 μm and an aspect ratio of 10-30. The talcum powder has a SiO2 content of >58%. The magnesium sulfate whisker has an aspect ratio of 20-30. The magnesium sulfate whisker has a refractive index of 1.52-1.

54.

2. The laser transmission modified polypropylene according to claim 1, characterized in that, The laser transmission modified polypropylene is prepared from the following raw materials in mass percentage: polypropylene 75-85%, talcum powder 16-20%, magnesium sulfate whisker 3.5-4.5%, nucleating agent 0.05-0.1%, and antioxidant 0.4-0.5%.

3. The laser transmission modified polypropylene of claim 1, wherein, The polypropylene has a melt index of 10-30 g / 10 min.

4. Use of the laser transmission modified polypropylene according to any one of claims 1-3 in laser welding of low-wall-thickness automobile parts.

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