1. The polypropylene composition is characterized by comprising the following components in parts by weight: 65-90 parts of polypropylene resin, 1-20 parts of toughening agent, 1-20 parts of LDPE, 0-1 part of mineral filler and 0.1-1 part of compatilizer.

2. The polypropylene composition according to claim 1, comprising the following components in parts by weight: 76-79 parts of polypropylene resin, 10-18 parts of toughening agent, 3-10 parts of LDPE, 0-1 part of mineral filler and 0.1-1 part of compatilizer; preferably, the weight part of the compatilizer is 0.5 part.

3. The polypropylene composition according to claim 1, wherein the polypropylene resin is a copolymerized polypropylene resin, and the melt mass flow rate of the polypropylene resin is 3 to 15g/min at 230 ℃ and 2.16 kg.

4. The polypropylene composition of claim 1, wherein the toughening agent comprises ethylene-buteneAt least one of copolymer, ethylene-octene copolymer, and styrene copolymer; preferably, the density of the toughening agent is 0.85-0.9 g/cm³The melt mass flow rate of the toughening agent at 190 ℃ and 2.16kg is 0.03-3 g/min.

5. The polypropylene composition of claim 1, wherein the LDPE has a density of from 0.912 to 0.918g/cm³The melt mass flow rate of the LDPE at 190 ℃ and 2.16kg is 0.05-3 g/min.

6. The polypropylene composition according to claim 1, wherein the mineral filler is talc powder, the talc powder has an aspect ratio of 10 to 16, and the talc powder has a mesh number of 1250 to 5000; the compatilizer is a polyolefin graft; preferably, the polyolefin graft comprises at least one of a polypropylene grafted maleic anhydride compound and a POE grafted maleic anhydride compound.

7. The polypropylene composition according to claim 1, further comprising 0.2 to 2 parts of auxiliaries, wherein the auxiliaries comprise an antioxidant, a light stabilizer, a lubricant and a nucleating agent; preferably, the antioxidant comprises hindered phenol antioxidant and phosphite antioxidant; the light stabilizer is a hindered amine light stabilizer; the lubricant is a metal stearate compound.

8. The preparation method of the polypropylene composition as claimed in any one of claims 1 to 7, wherein the polypropylene composition is obtained by uniformly mixing the polypropylene resin, the toughening agent, the LDPE, the mineral filler, the compatilizer and the auxiliary agent, melting and mixing, extruding and granulating.

9. The application of LDPE in improving the foaming performance of a polypropylene composition is characterized in that the polypropylene composition comprises the following components in parts by weight: 65-90 parts of polypropylene resin, 1-20 parts of toughening agent, 1-20 parts of LDPE, 0-1 part of mineral filler and 0.1-1 part of compatilizer; preferably, the polypropylene composition comprises the following components in parts by weight: 76-79 parts of polypropylene resin, 10-18 parts of toughening agent, 3-10 parts of LDPE, 0-1 part of mineral filler and 0.1-1 part of compatilizer.

10. The use of the LDPE according to claim 9 for improving the foaming properties of a polypropylene composition, wherein the polypropylene resin is a co-polypropylene resin, and the melt mass flow rate of the polypropylene resin at 230 ℃ and 2.16kg is 3-15 g/min; the density of the LDPE is 0.912-0.918 g/cm³The melt mass flow rate of the LDPE at 190 ℃ and 2.16kg is 0.05-3 g/min.

Background

Polypropylene (PP) has the advantages of low density, easy processing, excellent mechanical properties, etc., and has been widely used in the automotive industry, home appliances, and machinery fields at present. For the automotive industry, polypropylene is mainly used in interior and exterior parts of automobiles, such as instrument panels, door panels, pillars, and the like, and exterior parts, such as bumpers, fenders, deflectors, and the like. With the annual promotion of energy conservation and emission reduction and light weight of automobiles, the technology of foaming and forming polypropylene is continuously popularized in the field of automobile parts, the polypropylene material for secondary die sinking foaming is in transition from the first generation (filled with 20% of talcum powder) to the second generation (filled with 10% of talcum powder), and the third generation (non-filled) foaming polypropylene is already applied primarily.

In order to improve the foaming performance of polypropylene materials, many researches are carried out, especially in the aspects of development and selection of high-melt-strength polypropylene and the aspects of mechanism and performance of foaming agents, and material products with good foaming multiplying power and appearance are obtained. However, the third-generation foamed polypropylene developed at present has few gas nuclei generated during foaming due to no mineral filling, the foaming ratio is low, usually only 1.2 to 1.5 times, the diameter of the foam pores is large, and the performance after foaming is poor. In addition, the secondary mold opening foaming multiplying power is low, the investment of equipment and molds is large, and the comprehensive economic benefit is not ideal, so the application range of the unfilled foamed polypropylene is limited, and the unfilled foamed polypropylene is widely applied to a closed mold foaming process at present.

Disclosure of Invention

Based on the defects of the prior art, the invention aims to provide a polypropylene composition with good foaming performance and high foaming ratio.

In order to achieve the purpose, the invention adopts the technical scheme that:

a polypropylene composition comprises the following components in parts by weight: 65-90 parts of polypropylene resin, 1-20 parts of toughening agent, 1-20 parts of LDPE, 0-1 part of mineral filler and 0.1-1 part of compatilizer.

According to the polypropylene composition, the LDPE (high-pressure polyethylene) with specific content is added into the polypropylene formula, so that the melt strength can be effectively improved, the diameter of cells of the material is reduced, the foaming is more uniform, and the foaming performance and quality are improved; the LDPE added in the formula has a good compatibility effect with the polypropylene and the toughening agent, and the mechanical property of the polypropylene material can be obviously improved after the polypropylene material is foamed.

Preferably, the polypropylene composition comprises the following components in parts by weight: 76-79 parts of polypropylene resin, 10-18 parts of toughening agent, 3-10 parts of LDPE, 0-1 part of mineral filler and 0.1-1 part of compatilizer. The polypropylene composition prepared by the optimized formula has better foaming performance, and the prepared material has good appearance and excellent performance.

Preferably, the polypropylene composition comprises 0.5 part by weight of the compatibilizer. In the formula of the polypropylene composition, the compatilizer is used for coordinating components such as polypropylene, LDPE (low-density polyethylene), toughening agent and the like, and if the content of the compatilizer is not enough, the mechanical property of the polypropylene material after foaming is correspondingly reduced; when the content is too high, the odor of the material may be generated, and the use effect may be affected.

Preferably, the polypropylene resin is a copolymerized polypropylene resin, and the melt mass flow rate of the polypropylene resin at 230 ℃ and 2.16kg is 3-15 g/min. The melt Mass Flow Rate (MFR) is the range measured according to standard test method ASTM-D1238 using a weight of 2.16kg and at a temperature of 230 ℃. The polypropylene copolymer has good comprehensive performance and good appearance gloss, and can keep good mechanical performance and appearance when used as a foaming material; the melt mass flow rate is mainly used for distinguishing the viscous flow characteristics of the polymer in a molten state, and the polypropylene resin at the melt mass flow rate can enable the finally prepared polypropylene composition to have better mechanical effect.

Preferably, the toughening agent comprises at least one of ethylene-butene copolymer, ethylene-octene copolymer, styrenic copolymer. The copolymer has good compatibility and toughness, high bonding strength, and better mechanical property of the prepared foaming material.

Preferably, the density of the toughening agent is 0.85-0.9 g/cm³The melt mass flow rate of the toughening agent at 190 ℃ and 2.16kg is 0.03-3 g/min. The melt Mass Flow Rate (MFR) is the range measured according to standard test method ASTM-D1238 using a weight of 2.16kg and at a temperature of 190 ℃. The toughening agent under the density and MFR has better compatibility with the polypropylene resin and the LDPE, so that the whole material is more uniform in the mixing preparation process.

Preferably, the density of the LDPE is 0.912-0.918 g/cm³The melt mass flow rate of the LDPE at 190 ℃ and 2.16kg is 0.05-3 g/min. The melt Mass Flow Rate (MFR) is the range measured according to standard test method ASTM-D1238 using a weight of 2.16kg and at a temperature of 190 ℃. As an addition auxiliary agent, the LDPE can have better compatibility with the polypropylene resin and the toughening agent in the formula of the polypropylene composition within a specific density and MFR range, so that the synergistic effect is realized in the foaming process, and the prepared foaming material has more excellent mechanical properties.

Preferably, the mineral filler is talcum powder, the length-diameter ratio of the talcum powder is 10-16, and the mesh number of the talcum powder is 1250-5000. As the filler in the foaming polypropylene material, the talcum powder with specific length-diameter ratio and size is used, so that the talcum powder is more uniformly distributed in a polymer formula system, and a certain mechanical strength can be provided for the finally prepared polypropylene composition.

Preferably, the compatibilizer is a polyolefin graft. More preferably, the polyolefin graft comprises at least one of a polypropylene grafted maleic anhydride compound and a POE grafted maleic anhydride compound. The compatilizer can be better mixed and compatible with polypropylene, polyethylene resin and olefin copolymer, further cooperates the polarity of each component, and promotes the cooperative synergism of the polypropylene resin, the toughening agent and LDPE while maintaining the overall stability of the material.

Preferably, the unfilled high-expansion-ratio polypropylene composition further comprises 0.2-2 parts of an auxiliary agent; the auxiliary agent comprises an antioxidant, a light stabilizer, a lubricant and a nucleating agent.

Preferably, the antioxidant comprises hindered phenol antioxidant and phosphite antioxidant; the light stabilizer is a hindered amine light stabilizer; the lubricant is a metal stearate compound. More preferably, the antioxidant comprises at least one of antioxidant 1010 (pentaerythritol tetrakis [ beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate), antioxidant 1076 (n-octadecyl beta- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate), antioxidant 3114(1,3, 5-tris (3, 5-di-tert-butyl-4-hydroxybenzyl) isocyanuric acid), antioxidant 168 (tris [2, 4-di-tert-butylphenyl ] phosphite), PEP-36; the light stabilizer comprises at least one of UV-3808PP5, LA-402XP and LA-402 AF. The addition of the antioxidant, the light stabilizer and the lubricant under the types can effectively ensure the stability and the usability of the polypropylene composition, and avoid the influence of external conditions on the change of material properties and the final influence on the usability of the polypropylene composition.

Another object of the present invention is to provide a method for preparing the polypropylene composition, comprising the steps of:

uniformly mixing polypropylene resin, a toughening agent, LDPE (low-density polyethylene), a mineral filler, a compatilizer and an auxiliary agent, melting, mixing, extruding and granulating to obtain the polypropylene composition.

The preparation method of the non-filling high-foaming-ratio polypropylene composition has simple operation steps and can realize industrial large-scale production.

Preferably, the temperature of the melt mixing is 170-220 ℃, and the rotating speed is 350-450 r/min. Under which conditions the compositions are more uniformly melt mixed.

The invention also aims to provide application of LDPE in improving the foaming performance of a polypropylene composition, wherein the polypropylene composition comprises the following components in parts by weight: 65-90 parts of polypropylene resin, 1-20 parts of toughening agent, 1-20 parts of LDPE, 0-1 part of mineral filler and 0.1-1 part of compatilizer; preferably, the polypropylene composition comprises the following components in parts by weight: 76-79 parts of polypropylene resin, 10-18 parts of toughening agent, 3-10 parts of LDPE, 0-1 part of mineral filler and 0.1-1 part of compatilizer.

It is a further object of the present invention to provide the use of said polypropylene composition for the manufacture of vehicle parts.

The polypropylene composition obtained by the invention has the advantages of secondary die opening foaming performance, small diameter and uniform distribution of foam holes, excellent mechanical property and flat and smooth appearance, and is suitable for preparation of various vehicle parts and parts.

Preferably, the vehicle parts comprise a column box, a trunk, a glove box, a seat back plate, an automobile tail door, an automobile door panel and an automobile decorative strip.

The invention has the beneficial effects that: the invention provides a polypropylene composition, which can effectively improve the melt strength, reduce the diameter of cells of a material and enable the foaming to be more uniform by adding LDPE with specific content in a polypropylene formula, thereby improving the foaming performance and quality; the LDPE, the polypropylene and the toughening agent added in the formula have good compatibility effect and adhesion, can reduce the breakage around the foam hole in the foaming process and reduce the problem of overlarge or foam combination of the foam hole, has high foaming ratio, can obviously improve the mechanical property of the polypropylene material after foaming, and simultaneously keeps the smooth appearance. The invention also provides a preparation method of the polypropylene composition, which has simple operation steps and can realize industrial large-scale production. The invention also provides application of the LDPE in improving the foaming performance of the polypropylene composition. The invention also provides application of the polypropylene composition in preparation of vehicle parts.

Detailed Description

For better illustrating the objects, technical solutions and advantages of the present invention, the present invention will be further described with reference to specific examples, which are intended to be understood in detail, but not intended to limit the present invention.

Unless otherwise specified, the raw materials used in the following examples are all commercially available common products.

Examples 1 to 11

Examples of the polypropylene compositions according to the invention, the component formulations of the products according to the examples are shown in Table 1.

The preparation method of the polypropylene composition described in each example is the same, and comprises the following steps:

mixing polypropylene resin, a toughening agent, LDPE (low-density polyethylene), a mineral filler, a compatilizer and an auxiliary agent in a high-speed mixer for 30s, transferring the mixture to a double-screw extruder for melt mixing at the temperature of 200 ℃ at the screw rotating speed of 400r/min, and then extruding and granulating to obtain the polypropylene composition.

Comparative examples 1 to 7

The polypropylene compositions of comparative examples 1 to 7 differ from those of examples 1 to 11 only in the component formulation and content, and the component formulation of each comparative product is shown in Table 1.

In the components of table 1:

the polypropylene resin is a copolymer polypropylene resin produced by Exxon Mobil, and the melt mass flow rate at 230 ℃ and 2.16kg is 9 g/min;

the toughening agent is P produced by the Dow chemical methodOE; the density of the POE is 0.866g/cm³The melt mass flow rate of the POE at 190 ℃ and 2.16kg is 1 g/min;

the LDPE is produced by Exxon Mobil; the density of the LDPE is 0.912-0.918 g/cm³(ii) a The melt mass flow rate of the LDPE at 190 ℃ and 2.16kg is 1 g/min;

the compatilizer is PP grafted maleic anhydride, and the grafting rate is 0.7-1.0%;

the mineral filler is talcum powder, the length-diameter ratio of the talcum powder is 15, and the mesh number of the talcum powder is 3000 meshes.

In order to verify the performance of the polypropylene composition of the present invention, 1-3% by mass of a foaming agent is additionally added to the polypropylene compositions obtained in examples 1-11 and comparative examples 1-7, and the specific addition amount is shown in table 1. The mixture products of each group are injected and molded on a Claus morphine injection machine to form an unfoamed/foamed experimental plate with the same specification of 100 x 100mm, and are injected and molded on a common injection machine to form an ISO standard experimental sample bar, and the tensile strength, the impact strength of a simply supported beam notch, the bending strength, the bending modulus and other properties are tested; the cell size was observed and measured simultaneously with a microscope.

The tensile strength is tested by adopting a Zwick Z005 electronic universal tester;

the impact strength of the simply supported beam notch is tested by adopting a ZwickHIT5.5P electronic display impact instrument;

the bending strength and the bending modulus are tested by adopting a Zwick Z005 electronic universal tester.

The test results are shown in table 2.

TABLE 1

TABLE 2

As can be seen from Table 2, the polypropylene compositions obtained in the examples of the present invention have excellent secondary open-mold foaming performance compared with the composition obtained in the comparative examples, the cell size is small, the foaming ratio is high (the maximum value is up to 2 times), and the polypropylene compositions also have good mechanical properties when the polypropylene resin, the LDPE and the toughening agent are mixed at specific contents.

Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.