CN102924806A - Polypropylene composite with low linear expansion coefficient and preparation method thereof - Google Patents

Abstract

The invention discloses a special polypropylene composite with a low linear expansion coefficient for bumpers and a preparation method thereof. The special polypropylene composite with low shrinking percentage for bumpers is characterized by comprising the following raw materials by weight percentages: 40-65 percent of polypropylene, 0-2 percent of heat stabilizer, 0-2 percent of processing agent, 20-25 percent of flexibilizer, 0-6 percent of compatilizer, 5-10 percent of ultrafine talcum powder and 10-15 percent of chopped flat glass fiber. The preparation method comprises the following steps that after the raw materials are mixed, the mixture is added into a double-screw extruder with the length-diameter ratio of (30-60):1 to be molten and dispersed, meanwhile, the chopped flat glass fiber is fed into the double-screw extruder from a side feeding mouth to be extruded and pelletized, and the product is obtained. The composite has the advantages of high liquidity, high stiffness, high heat resistance, high size stability, high impact resistance and low linear expansion coefficient and meets the development requirement of bumper materials.

Description

A kind of low linear expansion coefficient polypropylene compound and preparation method thereof

technical field

The invention relates to a special polypropylene compound for automobile bumper with low linear expansion coefficient (CLTE) and a preparation method thereof, belonging to the technical field of polymer materials.

Background technique

The car bumper is a safety device that absorbs and moderates external impact and protects the front and rear of the car body. At present, most automobile bumpers are made of plastic, and polypropylene composite materials are the first choice for making bumpers.

With the development of the automobile industry, the automobile bumper, as an important safety device, is also on the road of innovation. In addition to maintaining the original protection function, the front and rear bumpers of today's cars also pursue harmony and unity with the shape of the car body. Bumpers are used as automotive exterior parts. With the drastic changes in the external environment temperature, large dimensional changes and product deformations caused by thermal expansion and contraction cannot occur. Therefore, bumpers require materials with a low linear expansion coefficient (CLTE) to avoid The drastic change of the external environment temperature leads to abnormal dimensions, which leads to the "surface difference" of the car bumper and affects the appearance of the car.

Traditional polypropylene composite materials for bumpers are generally filled with talcum powder to increase rigidity, and at the same time, to ensure its toughness, a large amount of thermoplastic elastomer is added. The linear expansion coefficient of this bumper material is extremely large. Seasonal size changes greatly, which affects the assembly of the bumper, and also causes "surface difference", which affects the appearance of the car.

Contents of the invention

The purpose of the present invention is to provide a special polypropylene compound for automobile bumper with low linear expansion coefficient and its preparation method, so as to overcome the defects in the prior art and meet the needs of the development of automobile bumper materials.

In order to achieve the above object, the present invention provides a polypropylene compound with low coefficient of linear expansion, characterized in that, it is made of the following raw materials in weight percentage:

Polypropylene 40-65%;

Heat stabilizer 0-2%;

Processing aids 0-2%;

Toughener 20-25%;

Compatibilizer 0-6%;

Superfine talc powder 5-10%;

Chopped flat glass fibers 10-15%.

Preferably, the linear expansion coefficient of the low linear expansion coefficient polypropylene compound is 3.0˜4.0×10 ⁻⁵ mm/mm/°C.

Preferably, the polypropylene is homopolymerized, copolymerized polypropylene or a mixture of both, and its melt flow rate is 20-1000g/10min.

Preferably, the heat stabilizer is a mixture of one or two of phenolic heat stabilizers, phosphate ester heat stabilizers and thioester heat stabilizers.

More preferably, the phenolic heat stabilizer is antioxidant Irganox1010 or antioxidant 1076. The phosphite heat stabilizer is antioxidant Ultranox627A or Irganox168. The thioester heat stabilizer is antioxidant DLTP.

Preferably, the processing aid is polyethylene wax or paraffin wax.

Preferably, the toughening agent is any one of ethylene-vinyl acetate copolymer, ethylene-α-ethylene-octene copolymer, ethylene-acrylate-glycidyl methacrylate copolymer and EPDM One or a mixture of two or more.

Preferably, the compatibilizer is a polar monomer grafted polymer.

More preferably, the polar monomer graft polymer is maleic anhydride grafted ethylene-vinyl acetate copolymer, maleic anhydride grafted ethylene-α-ethylene-octene copolymer or a mixture thereof.

Preferably, the chopped flat glass fiber (flat fiber) is non-alkali chopped glass fiber specially used for polypropylene, and the cross section of the glass fiber is flat, and the cross section width-to-thickness ratio is 2-10:1.

The present invention also provides a preparation method of the above-mentioned low linear expansion coefficient polypropylene compound, which is characterized in that the specific steps are: mixing polypropylene, heat stabilizer, processing aid, toughening agent, superfine talcum powder, compatibilizer After mixing, it is added to a twin-screw extruder with a length-to-diameter ratio of 30-60:1 to melt and disperse, and at the same time, the chopped flat glass fiber is fed into the twin-screw extruder from the side feeding port through a weight-loss metering balance, and extruded Pelletizing to obtain polypropylene compound with low coefficient of linear expansion.

Preferably, the aspect ratio of the twin-screw extruder is 40:1, and the temperature of each section of the twin-screw extruder is 190-240° C. during extrusion and granulation.

The present invention also provides the application of the above-mentioned low linear expansion coefficient polypropylene compound in the production of automobile bumpers.

The present invention has prepared a kind of low linear expansion coefficient (CLTE) special-purpose polypropylene composite for automobile bumper, this composite material has not only significantly improved polypropylene composite material owing to adopting flat glass fiber (flat fiber) to replace part ultrafine talcum powder Rigidity and heat resistance, while greatly reducing the coefficient of linear expansion (CLTE) of the material. Moreover, because the cross-section of the flat glass fiber is flat, the overall fiber presents a sheet-like structure similar to talcum powder, so the fluidity is much higher than that of the usual circular cross-section glass fiber. The distribution inside the parts tends to be isotropic, so there will be no warping deformation that occurs in general glass fiber reinforced materials.

The present invention uses chopped flat glass fiber (flat fiber) to replace part of ultra-fine talcum powder, which increases the rigidity of the material and significantly reduces the coefficient of linear expansion (CLTE) of the material. At the same time, the flat glass fiber will not cause floating fibers and warping on the surface curved deformation.

In addition, the function of the heat stabilizer in the present invention is to inhibit the degradation of polypropylene during processing; the function of the processing aid is to promote good dispersion between the components of the blend; the function of the toughening agent is to increase the The toughness at low temperature prevents the parts from becoming brittle at extremely low temperatures; the function of the compatibilizer is to increase the interfacial compatibility between polypropylene and chopped flat glass fibers.

The present invention adopts flat glass fiber to replace part of talcum powder, compared with the prior art, greatly reduces the linear expansion coefficient of the material, so that the degree of bumper size change with temperature changes is reduced; in addition, the flat glass fiber used in the present invention is different from traditional Glass fiber, because of its flat cross-section, has the characteristics of high fluidity and isotropy, which overcomes the shortcomings of traditional glass fibers that are easy to warp and float.

Detailed ways

In order to make the present invention more comprehensible, preferred embodiments are described in detail as follows.

Example 1

The first step: 64 kg of polypropylene PP BX3800, 0.2 kg of phenolic heat stabilizer Irganox1010 (MI=30g/10min), 0.3 kg of heat stabilizer DLTP, 0.3 kg of processing aid polyethylene wax CH-6A (Jiangyin Sainuo Chemical Co., Ltd.), 10 kg of ethylene-vinyl acetate copolymer (Taiwan Formosa Plastics, 7240M), 10 kg of ethylene-butyl acrylate-glycidyl methacrylate copolymer Elvaloy PTW, 0.2 kg of maleic anhydride grafted ethylene-acetic acid Ethylene copolymer HS4-112A (manufactured by Guangzhou Hecheng Chemical Co., Ltd.), 5 kg of 3000-mesh ultrafine talcum powder is fully mixed with a high-speed mixer;

The second step: the mixture obtained in the first step is transported to a twin-screw extruder with a length-to-diameter ratio of 60:1 at a rate of 90 kg/hour to melt and disperse, and at the same time, 10 kg of chopped alkali-free flat glass fiber NITTOBOCSG3PA- 870 (the length-to-diameter ratio of the cross-sectional axis is=2) is added with a rate of 10 kg/hour from the side feeding port by a weight-loss type metering scale, extruded and granulated, and the temperature of each section of the extruder is set to 190 ° C to obtain Polypropylene compound with low coefficient of linear expansion for the production of automotive bumpers. The resulting low linear expansion coefficient polypropylene compound has been tested and its properties are as follows:

Table 1

performance unit standard test Test Results density g/ ^cm3 ISO1183-93 0.97 The melt flow rate g/10min ISO1133-93 12 Tensile Strength MPa ISO527/2-93 twenty two Flexural modulus MPa ISO178-93 2550 23℃ notched impact strength KJ/ ^m2 ISO180-93 43 -30℃ notched impact strength KJ/ ^m2 ISO180-93 11.5 Heat distortion temperature (0.45Mpa) ℃ ISO75-93 124 Coefficient of Linear Expansion (CLTE) mm/mm/°C ASTM E831 3.9×10 ^-5

Example 2

The first step: 50 kg of polypropylene PP BX3900 (MI=60g/10min), 0.5 kg of phenolic heat stabilizer Irganox1010, 0.5 kg of phosphite heat stabilizer Irganox168, 1 kg of processing aid paraffin, 15 kg of ternary Ethylene-propylene rubber EPDM3702EM, 5 kg of ethylene-α-ethylene-octene copolymer 8200 (DuPont), 5 kg of maleic anhydride grafted ethylene-α-ethylene-octene copolymer SZ41P, 8 kg of 5000 mesh ultrafine talcum powder The high mixer is fully mixed;

The second step: the mixture obtained in the first step is delivered to the length-to-diameter ratio at a rate of 85 kg/hour to melt and disperse in the twin-screw extruder of 30: 1, while 15 kilograms of chopped alkali-free flat glass fibers CS7928,

BAYER AG, Germany (with elliptical cross-section) is added at a rate of 15 kg/hour from the side feeding port through a weight-loss type weighing scale, extruded and granulated, and the temperature of each section of the extruder is set to 220 ° C to obtain low linearity Coefficient of expansion polypropylene compound for the production of automotive bumpers. The resulting low linear expansion coefficient polypropylene compound has been tested and its properties are as follows:

Table 2

performance unit standard test Test Results density g/ ^cm3 ISO1183-93 1.01 The melt flow rate g/10min ISO1133-93 28

Tensile Strength MPa ISO527/2-93 27 Flexural modulus MPa ISO178-93 2750 23℃ notched impact strength KJ/ ^m2 ISO180-93 46 -30℃ notched impact strength KJ/ ^m2 ISO180-93 12.5 Heat distortion temperature (0.45Mpa) ℃ ISO75-93 126 Coefficient of Linear Expansion (CLTE) mm/mm/°C ASTM E831 3.5×10 ^-5

Example 3

The first step: 49 kg of polypropylene PP BX3920 (MI=100g/10min), 2 kg of phenolic heat stabilizer 1076, 1 kg of phosphite heat stabilizer Ultranox627A, 1 kg of processing aid polyethylene wax CH-6A (Jiangyin Sainuo Chemical Co., Ltd.), 25 kilograms of ethylene-butyl acrylate-glycidyl methacrylate copolymer Elvaloy PTW, 10 kilograms of 3000 mesh talcum powder are fully mixed by a high mixer;

Second step: the mixture obtained in the first step is delivered to the length-to-diameter ratio at a rate of 88 kg/hour to melt and disperse in the twin-screw extruder of 40: 1, while 12 kilograms of chopped alkali-free flat glass fibers CS7928, BAYER AG, Germany (with elliptical cross-section) is added at a rate of 12 kg/hour from the side feed port through a weight-loss type weighing scale, extruded and granulated, and the temperature of each section of the extruder is set to 240 ° C to obtain low linearity Coefficient of expansion polypropylene compound for the production of automotive bumpers. The resulting low linear expansion coefficient polypropylene compound has been tested and its properties are as follows:

table 3

performance unit standard test Test Results density g/ ^cm3 ISO1183-93 1.05 The melt flow rate g/10min ISO1133-93 42 Tensile Strength MPa ISO527/2-93 31 Flexural modulus MPa ISO178-93 3050 23℃ notched impact strength KJ/ ^m2 ISO180-93 49 -30℃ notched impact strength KJ/ ^m2 ISO180-93 16.8 Heat distortion temperature (0.45Mpa) ℃ ISO75-93 132 Coefficient of Linear Expansion (CLTE) mm/mm/°C ASTM E831 3.0×10 ^-5

Example 4

The first step: 47 kg of polypropylene PP BX3800 (MI=30g/10min), 0.2 kg of phenolic heat stabilizer Irganox1010, 0.3 kg of heat stabilizer DLTP, 0.5 kg of processing aid polyethylene wax CH-6A (Jiangyin Sainuo Chemical Co., Ltd.), 22.5 kilograms of ethylene-α-ethylene-octene copolymer 8200 (DuPont), 2 kilograms of maleic anhydride grafted ethylene-α-ethylene-octene copolymer SZ41P, 13.5 kilograms of 3000 mesh ultrafine talcum powder The high mixer is fully mixed;

The second step: the mixture obtained in the first step is delivered to a twin-screw extruder with a length-to-diameter ratio of 40:1 at a rate of 86 kg/hour, and melted and mixed to disperse 14 kg of chopped alkali-free flat glass fibers NITTOBOCSG3PA- 870 (the length-to-diameter ratio of the cross-sectional axis is=2) is added with a rate of 14 kg/hour from the side feeding port by a weight-loss type metering scale, extruded and granulated, and the temperature of each section of the extruder is set to 190 ° C to obtain Polypropylene compound with low coefficient of linear expansion for the production of automotive bumpers. The resulting low linear expansion coefficient polypropylene compound has been tested and its properties are as follows:

Table 4

performance unit standard test Test Results density g/ ^cm3 ISO1183-93 0.98 The melt flow rate g/10min ISO1133-93 12 Tensile Strength MPa ISO527/2-93 twenty three Flexural modulus MPa ISO178-93 2450 23℃ notched impact strength KJ/ ^m2 ISO180-93 44 -30℃ notched impact strength KJ/ ^m2 ISO180-93 12 Heat distortion temperature (0.45Mpa) ℃ ISO75-93 123 Coefficient of Linear Expansion (CLTE) mm/mm/°C ASTM E831 3.8×10 ^-5

Example 5

The first step: 34 kg of polypropylene PP BX3900 (MI=60g/10min), 17 kg of polypropylene PPBX3800, 0.5 kg of heat stabilizer DLTP, 0.5 kg of phenolic heat stabilizer 1010, 1 kg of processing aid polyethylene wax, 22 kilograms of ethylene-vinyl acetate copolymer EVA7240 (Taiwan Formosa Plastics), 4 kilograms of maleic anhydride grafted ethylene-vinyl acetate copolymer HS4-112A (Guangzhou Hecheng Chemical Co., Ltd.), 8 kilograms of 5000 mesh ultrafine talcum powder The high mixer is fully mixed;

The second step: the mixture obtained in the first step is delivered to a twin-screw extruder with a length-to-diameter ratio of 40:1 at a rate of 87 kg/hour, and melted and mixed to disperse, while 13 kg of chopped alkali-free flat glass fiber NITTOBO CSG3PA-820 (length-to-diameter ratio of the cross-sectional axis = 4) (width-to-thickness ratio is 6:1) is added at a rate of 13 kg/hour from the side feeding port through a weight-loss weighing scale, extruded to granulate, extruded The temperature of each section of the machine is set to 220°C to obtain a low linear expansion coefficient polypropylene compound for the production of automobile bumpers. The resulting low linear expansion coefficient polypropylene compound has been tested and its properties are as follows:

table 5

performance unit standard test Test Results density g/ ^cm3 ISO1183-93 1.00 The melt flow rate g/10min ISO1133-93 26 Tensile Strength MPa ISO527/2-93 28 Flexural modulus MPa ISO178-93 2700 23℃ notched impact strength KJ/ ^m2 ISO180-93 46 -30℃ notched impact strength KJ/ ^m2 ISO180-93 12.5 Heat distortion temperature (0.45Mpa) ℃ ISO75-93 126 Coefficient of Linear Expansion (CLTE) mm/mm/°C ASTM E831 3.5×10 ^-5

Example 6

The first step: 49 kg of polypropylene PP BX3920 (MI=100g/10min), 1 kg of phenolic heat stabilizer 1010, 1 kg of phosphite heat stabilizer 627A, 1 kg of processing aid paraffin, 20 kg of EPDM3702EM, 6 kg of ethylene-butyl acrylate-glycidyl methacrylate copolymer Elvaloy PTW, 10 kg of 3000-mesh talcum powder are fully mixed with a high-speed mixer;

The second step: the mixture obtained in the first step is delivered to a twin-screw extruder with a length-to-diameter ratio of 40:1 at a rate of 88 kg/hour, melted and mixed, and 12 kg of chopped alkali-free flat glass fiber NITTOBO CSG3PA-820 (length-to-diameter ratio of the cross-sectional axis = 4) (width-to-thickness ratio is 10:1) is added at a rate of 12 kg/hour from the side feeding port through a weight-loss weighing scale, extruded to granulate, extruded The temperature of each section of the machine is set to 240°C to obtain a low linear expansion coefficient polypropylene compound for the production of automobile bumpers. The resulting low linear expansion coefficient polypropylene compound has been tested and its properties are as follows:

Table 6

performance unit standard test Test Results

density g/ ^cm3 ISO1183-93 1.05 The melt flow rate g/10min ISO1133-93 42 Tensile Strength MPa ISO527/2-93 30 Flexural modulus MPa ISO178-93 2950 23℃ notched impact strength KJ/ ^m2 ISO180-93 51 -30℃ notched impact strength KJ/ ^m2 ISO180-93 17.8 Heat distortion temperature (0.45Mpa) ℃ ISO75-93 130 Coefficient of Linear Expansion (CLTE) mm/mm/°C ASTM E831 3.0×10 ^-5

The material provided by the invention has high fluidity, high rigidity, high heat resistance, high dimensional stability, high impact and low coefficient of linear expansion (CLTE), and meets the requirements for the development of automobile bumper materials. After testing, melt flow rate ≥ 10g/10min, tensile strength ≥ 20MPa, flexural modulus ≥ 2200MPa, (23°C) notched impact strength ≥ 40KJ/m ² , (-30°C) notched impact strength ≥ 10KJ/m ² , heat distortion temperature (0.45Mpa) ≥ 120 ℃, coefficient of linear expansion (CLTE) ≤ 4×10 ^-5 .

The present invention uses flat glass fibers to replace part of the talcum powder. Compared with the prior art, the linear expansion coefficient of the material is greatly reduced, and the degree of bumper size change with temperature changes is reduced. At the same time, the flat glass fibers used in the present invention are different from traditional Glass fiber, because of its flat cross-section, has the characteristics of high fluidity and isotropy, which overcomes the shortcomings of traditional glass fibers that are easy to warp and float.

Claims (10)

1. A low linear expansion coefficient polypropylene compound is characterized in that, is made of the following raw materials in weight percent: Polypropylene 40-65%; Heat stabilizer 0-2%; Processing aids 0-2%; Toughener 20-25%; Compatibilizer 0-6%; Superfine talc powder 5-10%; Chopped flat glass fiber 10-15%. 2. The low linear expansion coefficient polypropylene compound according to claim 1, characterized in that its linear expansion coefficient is 3.0-4.0×10 ^-5 mm/mm/°C. 3. The polypropylene compound with low coefficient of linear expansion as claimed in claim 1, wherein said polypropylene is homopolymerization, copolymerization polypropylene or a mixture of both, and its melt flow rate is 20-1000g/ 10min. 4. The low linear expansion coefficient polypropylene compound as claimed in claim 1, is characterized in that, described thermal stabilizer is in phenolic thermal stabilizer and phosphate thermal stabilizer and thioester thermal stabilizer one or a mixture of two. 5. The polypropylene compound with low linear expansion coefficient as claimed in claim 1, characterized in that, the processing aid is polyethylene wax or paraffin wax. 6. The low linear expansion coefficient polypropylene compound as claimed in claim 1, is characterized in that, described toughening agent is ethylene-vinyl acetate copolymer, ethylene-alpha-ethylene-octene copolymer, ethylene-acrylic acid Any one or a mixture of two or more of ester-glycidyl methacrylate copolymer and EPDM rubber. 7. The polypropylene compound with low coefficient of linear expansion according to claim 1, characterized in that, the compatibilizer is a polar monomer graft polymer. 8. The polypropylene compound with low coefficient of linear expansion as claimed in claim 1, wherein the chopped flat glass fiber is a special alkali-free chopped glass fiber for polypropylene, and its glass fiber cross section is flat, and the cross section is flat. The aspect ratio is 2-10:1. 9. the preparation method of the described low linear expansion coefficient polypropylene compound of claim 1 is characterized in that, concrete steps are: polypropylene, thermal stabilizer, processing aid, toughening agent, superfine talcum powder, phase After the compatibilizer is mixed, it is added to a twin-screw extruder with a length-to-diameter ratio of 30-60:1 to melt and disperse, and at the same time, the chopped flat glass fiber is fed into the twin-screw extruder from the side feeding port through a weight-loss metering balance , extruded and granulated to obtain a polypropylene compound with a low coefficient of linear expansion. 10. The application of the low linear expansion coefficient polypropylene compound according to claim 1 in the production of automobile bumpers.