A micro-foamed polypropylene composition and its preparation method and application

Abstract

The present invention relates to a micro-foamed polypropylene composition and a preparation method and application thereof. The micro-foamed polypropylene composition comprises the following components: polypropylene resin, carbon fiber, colorant, toughening agent, compatibilizer and additive. A workpiece prepared by the micro-foamed polypropylene composition has good welding shear force after laser welding. In addition, the micro-foamed polypropylene composition also has low density, good tensile strength, bending strength and notched impact strength.

Description

Technical Field

[0001] The present invention relates to the technical field of polypropylene materials, and more specifically, to a micro-foamed polypropylene composition and a preparation method and application thereof. Background Art

[0002] Under the premise of the increasing trend of environmental protection and lightweight in the automotive industry, polypropylene micro-foam material has become an ideal choice for lightweight composite materials. It has a unique dense surface layer and foam core layer structure. Under the premise of ensuring the basic performance of the material, it can significantly reduce the weight of the parts and achieve lightweight automobiles. The formation of micropores inside the foam material inevitably reduces the mechanical performance indicators of the foam material, especially the rigidity. Therefore, reinforcing materials (commonly glass fiber, calcium carbonate, etc.) must be added to ensure that the parts meet the corresponding performance. For example, the reinforced micro-foamed polypropylene material provided by the Chinese patent named "Glass fiber reinforced polypropylene micro-foamed material for electric tools and its preparation method" is achieved by adding glass fiber to achieve the reinforcement of polypropylene micro-foamed material.

[0003] Laser welding is a welding method that uses a high-energy-density laser beam as a heat source, that is, laser radiation (wavelength is generally 900-1100nm) heats the surface of the plastic workpiece, and the surface heat diffuses to the inside through heat conduction, melting the contact surface of the plastic workpiece to form a specific molten pool, and then the plastic workpieces are bonded together. Compared with other welding technologies (such as friction vibration, dehydration bonding, thermal welding, and ultrasonic welding), laser welding has the advantages of non-contact, airtight, watertight, fast and efficient, high precision, beautiful welds, unlimited product appearance, easy control, and strong adaptability.

[0004] At present, no enhanced micro-foamed polypropylene material is used as a laser welding material. The main reason is that the common enhanced micro-foamed polypropylene material has low laser transmittance and light absorption efficiency, resulting in insufficient welding shear force (less than 800N) of the workpiece made of the material, which cannot meet the requirements of use.

[0005] Therefore, it is necessary to solve the problem of insufficient welding shear force when laser welding is used to process reinforced micro-foamed polypropylene materials. Summary of the invention

[0006] The primary purpose of the present invention is to overcome the problem of insufficient welding shear force when laser welding is used to process the enhanced micro-foamed polypropylene material in the above-mentioned prior art, and to provide a micro-foamed polypropylene composition. The workpiece prepared by the micro-foamed polypropylene composition has good welding shear force after laser welding. In addition, the micro-foamed polypropylene composition also has a low density, good tensile strength, bending strength and notched impact strength, meeting the requirements of use.

[0007] A further object of the present invention is to provide a method for preparing the micro-foamed polypropylene composition.

[0008] A further object of the present invention is to provide the use of the micro-foamed polypropylene composition in the preparation of laser-welded polypropylene workpieces.

[0009] The above-mentioned object of the present invention is achieved by the following technical solutions:

[0010] A micro-foamed polypropylene composition comprises the following components in parts by weight:

[0011]

[0012] The colorant is at least one of tungsten organic salt, samarium trioxide, methyl catechol metal complex tetrabutylammonium salt, aminophthalocyanine metal complex or carbon black.

[0013] The inventors of the present invention have discovered through research that the reinforcing materials of the current enhanced micro-foamed polypropylene material are mainly glass fiber, calcium carbonate or talcum powder. These reinforcing materials have barrier properties to lasers with a wavelength of 900 to 1100 nm, thereby hindering the penetration of the laser into the enhanced micro-foamed polypropylene material during laser welding; in addition, the bubbles in the enhanced micro-foamed polypropylene material have a scattering effect on the laser, which also reduces the transmittance of the laser. These two aspects make the enhanced micro-foamed polypropylene material have a low absorption rate for the laser, thereby resulting in a low welding shear force of the workpiece.

[0014] The inventors of the present invention, through further research and development, added carbon fiber to the micro-foamed polypropylene composition, which not only plays the role of reinforcing material and improves the tensile strength, bending strength and notched impact strength of the micro-foamed polypropylene composition, but also cooperates with a specific colorant to improve the welding shear force of the micro-foamed polypropylene composition. The reason is that both carbon fiber and the specific colorant can be used as light-absorbing materials. The presence of both has high light absorption efficiency for lasers, which overcomes the problem of low absorption rate of lasers by the material, so that the surface contact surface of the micro-foamed polypropylene composition workpiece is fully melted, the workpiece is fully bonded, and the welding shear force of the material is effectively improved.

[0015] That is, the workpiece prepared by the micro-foamed polypropylene composition of the present invention has good welding shear force after laser welding. In addition, the micro-foamed polypropylene composition also has low density, good tensile strength, bending strength and notched impact strength, meeting the use requirements.

[0016] Preferably, the following components are included in parts by weight:

[0017]

[0018] In the present invention, the polypropylene resin is composed of a first polypropylene, a second polypropylene and a third polypropylene in a mass ratio of (2-6):(1-3):1, the first polypropylene is a homopolypropylene with a melt index of 1g / min≤MI≤10g / min, the second polypropylene is a copolymer polypropylene with a melt index of 50g / min<MI≤150g / min, and the third polypropylene is a copolymer polypropylene with a melt index of 10g / min≤MI≤50g / min.

[0019] The first polypropylene has high crystallinity, the second polypropylene has high fluidity, and the third polypropylene has good impact resistance. By compounding the three in a specific mass ratio, the micro-foamed polypropylene composition can have good fluidity and impact resistance as well as good strength, thereby making the welding shear force of the micro-foamed polypropylene composition higher.

[0020] More preferably, the third polypropylene is an ethylene-propylene copolymer.

[0021] More preferably, the first polypropylene is a homopolypropylene with a melt index of 1g / min≤MI≤3g / min, the second polypropylene is a copolymer polypropylene with a melt index of 60g / min≤MI≤150g / min, and the third polypropylene is a copolymer polypropylene with a melt index of 10g / min≤MI≤30g / min.

[0022] The melt index of the first polypropylene, the second polypropylene and the third polypropylene of the present invention can be measured according to the test standard ISO1133-1 / 2:2012 under the test conditions of 230° C. and 2.16 kg.

[0023] Optionally, the carbon fiber is at least one of ST600, ST800, FUY-110-10, FUY-110-15, PX35CA0250-65 or ACECA-CBZ SP2.

[0024] Preferably, the carbon fiber is at least one of ST600 or PX35CA0250-65.

[0025] By selecting the specific carbon fiber, the welding shear force of the obtained micro-foamed polypropylene composition is higher.

[0026] Preferably, the colorant is an organic tungsten salt; the organic tungsten salt is obtained by a chemical reaction between tungsten hexachloride and tributyl phosphate.

[0027] The inventors of the present invention have found through research that when a tungsten organic salt synthesized from specific raw materials is added as a colorant to the micro-foamed polypropylene composition of the present invention, the welding shear force of the obtained micro-foamed polypropylene composition is more excellent and can reach more than 850N.

[0028] Specifically, the preparation method of the tungsten organic salt is as follows: dissolve tungsten hexachloride in dichloromethane, add tributyl phosphate dropwise to an excess amount while stirring at 0 to 50°C, continue stirring for 1 to 2 hours, and then distill (distillation is to remove dichloromethane, unreacted tributyl phosphate and the by-product hydrogen chloride produced in the reaction) to obtain the tungsten organic salt.

[0029] Optionally, the metal in the methyl catechol metal complex tetrabutylammonium salt is at least one of iron, cobalt, nickel, copper, zinc or manganese.

[0030] Preferably, the metal in the methyl catechol metal complex tetrabutylammonium salt is at least one of iron or copper.

[0031] Optionally, the metal in the aminophthalocyanine metal complex is at least one of iron, cobalt, nickel, copper, zinc, manganese, lead or indium, and the aminophthalocyanine in the aminophthalocyanine metal complex is at least one of 3,3',3''',3'''''-tetra-n-butylaminophthalocyanine, 1,4,8,11,15,18,22,25-octabutoxyphthalocyanine or 1,8,15,22-tetra-butylphenoxyphthalocyanine.

[0032] Preferably, the metal in the aminophthalocyanine metal complex is at least one of copper and manganese, and the aminophthalocyanine in the aminophthalocyanine metal complex is 3,3',3'',3''''-tetra-n-butylaminophthalocyanine.

[0033] Optionally, the toughening agent is at least one of ethylene-butene copolymer, ethylene-octene copolymer or styrene-butene copolymer elastomer.

[0034] Preferably, the toughening agent is composed of ethylene-butene copolymer and styrene-butene copolymer elastomer in a mass ratio of (1-1.5): (1.5-1).

[0035] Optionally, the compatibilizer is at least one of maleic anhydride grafted polypropylene, glycidyl methacrylate grafted polypropylene or acrylic acid grafted polypropylene.

[0036] Preferably, the compatibilizer is maleic anhydride grafted polypropylene.

[0037] Optionally, the auxiliary agent is at least one of an antioxidant or a light stabilizer.

[0038] Optionally, the antioxidant is at least one of a hindered phenol antioxidant or a phosphite antioxidant.

[0039] Further optionally, the antioxidant is at least one of 1010, 1076, 3114, 168, and PEP-36.

[0040] Optionally, the light stabilizer is a hindered amine light stabilizer, including but not limited to UV-3808PP5, LA-402AF, etc.

[0041] The preparation method of the micro-foamed polypropylene composition comprises the following steps: mixing the components, melt-extruding, and granulating to obtain the micro-foamed polypropylene composition.

[0042] Generally, the preparation method comprises the following steps: stirring and mixing the components in a high-speed mixer, and then melt-extruding and granulating the components in a twin-screw extruder to obtain a micro-foamed polypropylene composition. The melting temperature is 170-220° C., and the screw speed of the twin-screw extruder is 350-450 rpm.

[0043] The micro-foamed polypropylene composition obtained by melt extrusion and granulation is mixed with a foaming agent and foamed by closed mold to obtain a micro-foamed polypropylene composition product. The amount of the foaming agent is 0.1-5% of the amount of the micro-foamed polypropylene composition.

[0044] Optionally, the foaming agent is at least one of ammonium bicarbonate, sodium bicarbonate, azodicarbonamide, toluenesulfonamide, and azodicarbonamide.

[0045] Preferably, the blowing agent is azodicarbonate.

[0046] The use of the micro-foamed polypropylene composition in the preparation of laser-welded polypropylene workpieces is also within the protection scope of the present invention.

[0047] Preferably, the polypropylene workpiece is an automobile structural part, including but not limited to a micro-foamed automobile door panel, a shifter base, etc.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] The workpiece prepared by the micro-foamed polypropylene composition of the present invention has good welding shear force after laser welding. In addition, the micro-foamed polypropylene composition also has low density, good tensile strength, bending strength and notched impact strength, meeting the use requirements. DETAILED DESCRIPTION

[0050] In order to more clearly and completely describe the technical solution of the present invention, the present invention is further described in detail through specific embodiments below. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention. Various changes can be made within the scope of the rights of the present invention.

[0051] Some of the reagents selected in the embodiments and comparative examples of the present invention are described as follows:

[0052] First polypropylene: N-T30S, Maoming Petrochemical, homopolymer polypropylene, MI = 3g / 10min;

[0053] Second polypropylene: HX3900, South Korea SK, copolymer polypropylene, MI = 60g / 10min;

[0054] The third polypropylene: K9928, Dushanzi Petrochemical, copolymer polypropylene, MI = 30g / 10min;

[0055] Carbon fiber 1#: ST600, Guangzhou Sente New Materials Co., Ltd.;

[0056] Carbon fiber 2#: PX35CA0250-65, Zoltek corporation;

[0057] Carbon fiber 3#: HT C415 6MM, Teijin Shoji (Shanghai) Co., Ltd.

[0058] Glass fiber: ECS3F-03-508A, China Jushi Co., Ltd.

[0059] Foaming agent: MB180, Sinochem Chemical Technology (Shanghai) Co., Ltd.

[0060] Colorant 1#: tungsten organic salt, homemade, the preparation process is as follows: dissolve tungsten hexachloride in dichloromethane, add tributyl phosphate until it is excessive, the adding time is about 1.5 hours, stir at 25℃ for 2 hours, then remove dichloromethane, unreacted tributyl phosphate and the by-product hydrogen chloride produced in the reaction by distillation to obtain a viscous product, which is the tungsten organic salt.

[0061] Colorant 2#: carbon black, RAVEN 2350, Shanghai Bohuai Chemical Co., Ltd.;

[0062] Colorant 3#: samarium trioxide, Shandong Poly Chemical Co., Ltd.;

[0063] Colorant 4#: (tetraaminophthalocyanine) copper (II), Hubei Jusheng Technology Co., Ltd.;

[0064] Colorant 5#: R225, 3-methyl-6-(p-toluidine)-3H-dibenzo[f,ij]isoquinoline-2,7-dione, Shenzhen Tianlaibao Pigment Co., Ltd.;

[0065] Toughener 1#: ethylene-octene copolymer, 8137, Dow Chemical;

[0066] Toughener 2#: styrene-butylene copolymer elastomer, G1633 ES, Kraton Polymer Trading (Shanghai) Co., Ltd.;

[0067] Compatibilizer: Maleic anhydride grafted polypropylene, CMG9801, Jiayirong Polymer (Shanghai) Co., Ltd.

[0068] Antioxidant 1#: Antioxidant 1010, commercially available;

[0069] Antioxidant 2#: Antioxidant 168, commercially available;

[0070] Light stabilizer: UV-3808PP5, commercially available.

[0071] Unless otherwise specified, the components (eg, compatibilizer, light stabilizer) used in the parallel examples and comparative examples are all the same commercially available products.

[0072] The preparation process of the micro-foamed polypropylene composition of each embodiment of the present invention and the comparative example is as follows: weigh each component except the foaming agent according to the ratio, mix them evenly and add them into a twin-screw extruder for melt mixing. The melt mixing temperature is 170-220°C, the screw speed is 350-450 rpm, and extrusion granulation is performed to obtain the micro-foamed polypropylene composition.

[0073] Take the micro-foamed polypropylene composition of each embodiment and comparative example, introduce the corresponding amount of foaming agent (according to Table 1) during the injection molding process, and prepare the micro-foamed polypropylene composition sample by closed mold foaming process for the following performance tests.

[0074] Take the micro-foamed polypropylene composition samples obtained after injection molding and foaming of each embodiment of the present invention and the comparative example, and then measure the properties according to the following test method:

[0075] (1) Density (unit: g / cm 3 ): The density of the material is tested in accordance with GB T 1033.1-2008 "Determination of density of non-foamed plastics Part 1: Immersion method, liquid pycnometer method and titration method"; the sample size is 80mm*10mm*4mm.

[0076] (2) Tensile strength (unit: MPa): The tensile strength of the material was determined in accordance with GB / T 1040.2-2022 "Determination of tensile properties Part 2: Test conditions for molded and extruded plastics". Type 1A specimen was selected; total length 170 mm, narrow parallel part length 80 mm, radius 24 mm, distance between wide parallel parts 109.3 mm, end width 20 mm, narrow part width 10 mm, thickness 4 mm, and gauge length 75 mm.

[0077] (3) Flexural strength (unit: MPa): The flexural strength of the material was tested in accordance with GB / T 9341-2008 “Determination of flexural properties of plastics”; the sample size was 80 mm*10 mm*4 mm.

[0078] (4) Notched impact strength (unit: KJ / m 2 ): Test the room temperature notched impact strength of the material according to GB / T 1843-2008 "Determination of Izod Impact Strength of Plastics". The notch type is B, the sample size is 80mm*10mm*4mm, and the notch residual thickness is 8mm.

[0079] (5) Welding shear force (unit: N): Take a micro-foamed polypropylene composition sample with a size of 80 mm*10 mm*4 mm and a UT8012M sample with a size of 80 mm*10 mm*4 mm (Maoming Petrochemical, MI=12 g / 10 min), stack the micro-foamed polypropylene composition sample under the UT8012M sample for laser welding, and then use a universal testing machine to test the shear force of the sample after welding.

[0080] Examples 1 to 10

[0081] Examples 1 to 10 provide a series of micro-foamed polypropylene compositions, the formulations of which are shown in Table 1.

[0082] Table 1 Formulas of Examples 1 to 10 (parts by weight)

[0083]

[0084]

[0085] Comparative Example 1

[0086] This comparative example provides a micro-foamed polypropylene composition, the formula of which is different from that of Example 1 in that no carbon fiber 1# is added.

[0087] Comparative Example 2

[0088] This comparative example provides a micro-foamed polypropylene composition, the formula of which is different from that of Example 1 in that carbon fiber 1# is replaced by glass fiber.

[0089] Comparative Example 3

[0090] This comparative example provides a micro-foamed polypropylene composition, the formula of which is different from that of Example 1 in that: colorant 1# is not added.

[0091] Comparative Example 4

[0092] This comparative example provides a micro-foamed polypropylene composition, the formula of which is different from that of Example 1 in that colorant 1# is replaced by colorant 5#.

[0093] The performance test results of the micro-foamed polypropylene compositions of the embodiments and comparative examples after injection molding and foaming into specimens are shown in Table 2.

[0094] Table 2 Performance test results of the micro-foamed polypropylene composition of each embodiment and comparative example

[0095]

[0096]

[0097] As can be seen from Table 2, the welding shear force of the micro-foamed polypropylene compositions of Examples 1 to 10 can reach more than 800N, which has good welding shear force and can solve the problem of insufficient welding shear force when laser welding is used to process enhanced micro-foamed polypropylene materials in the prior art.

[0098] Comparative Example 1 does not add carbon fiber, and the welding shear force of its micro-foamed polypropylene composition is only 761N, which cannot reach more than 800N; Comparative Example 2 adds glass fiber instead of carbon fiber, and the welding shear force of its micro-foamed polypropylene composition is lower than that of Comparative Example 1, which is only 736N; Comparative Example 3 does not add the specific colorant of the present invention, and the welding shear force of its micro-foamed polypropylene composition is only 758N, which cannot reach more than 800N; Comparative Example 4 adds an inappropriate colorant, and the welding shear force of its micro-foamed polypropylene composition is significantly lower.

[0099] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A micro-foamed polypropylene composition, characterized in that: The composition comprises the following components in parts by weight: Polypropylene resin 41.6~78 parts, 5-30 parts of carbon fiber, Colorant 0.2-2 parts, 10 to 30 parts of toughening agent, Compatibilizer 1 to 10 parts, 0.2-2 parts of additives; The colorant is a tungsten organic salt; the tungsten organic salt is obtained by a chemical reaction between tungsten hexachloride and tributyl phosphate; The polypropylene resin is composed of a first polypropylene, a second polypropylene and a third polypropylene in a mass ratio of (2-6): (1-3):

1. Under the test conditions of 230° C. and 2.16 kg, it is measured that the first polypropylene is a homopolypropylene with a melt index of 1 g / min≤MI≤10 g / min, the second polypropylene is a copolymer polypropylene with a melt index of 50 g / min<MI≤150 g / min, and the third polypropylene is a copolymer polypropylene with a melt index of 10 g / min≤MI≤50 g / min.

2. The micro-foamed polypropylene composition according to claim 1, characterized in that: The composition comprises the following components in parts by weight: Polypropylene resin 50~69 parts, 10~20 parts of carbon fiber, Colorant 0.4~1.5 parts, 15~25 parts of toughening agent, 3~6 parts of compatibilizer, 0.2 to 2 parts of additives.

3. The micro-foamed polypropylene composition according to claim 1, characterized in that: The carbon fiber is at least one of ST600, ST800, FUY-110-10, FUY-110-15, PX35CA0250-65 or ACECA-CBZ SP2.

4. The micro-foamed polypropylene composition according to claim 1, characterized in that: The toughening agent is at least one of ethylene-butene copolymer, ethylene-octene copolymer or styrene-butene copolymer elastomer.

5. The micro-foamed polypropylene composition according to claim 1, characterized in that: The compatibilizer is at least one of maleic anhydride grafted polypropylene, glycidyl methacrylate grafted polypropylene or acrylic acid grafted polypropylene.

6. The method for preparing the micro-foamed polypropylene composition according to any one of claims 1 to 5, characterized in that: The method comprises the following steps: mixing the components, melt extruding, granulating, and closing the mold for foaming to obtain the micro-foamed polypropylene composition.

7. Use of the micro-foamed polypropylene composition according to any one of claims 1 to 5 in preparing polypropylene workpieces for laser welding.

Images