CN1765976A - A kind of polypropylene foam premix and preparation method thereof - Google Patents

Abstract

The invention provides a pre-mix material for polypropylene foam, which comprises: using the polypropylene random copolymer of 100 weight shares with 3.5~6.5% content and 3.0~9.0 MWD and polypropylene of 5~10 weight shares with 1~4g/10min fusion index and 0.3~0.6N fused mass strength as base resin, and fusing with organic foamer. This product has well foam pore structure, even pore diameter, and high foaming ratio with 7~12 foaming multiplying power and 75~129Kg/m3 foam bulk weight, and has wide application.

Description

A kind of polypropylene foam premix and preparation method thereof

technical field

The present invention relates to a kind of foamed plastics, more specifically, it relates to a premixed material of foamed polypropylene material and a preparation method thereof.

Background technique

Due to the sharp drop in viscosity when polypropylene is melted, the melt strength is very low, and foam molding is very difficult. Therefore, the cross-linking process is often used to increase the melt viscosity of the system to prepare foamed polypropylene. Such as U.S. Patent No. 4,766,159, adopts the method for radiation cross-linking and foaming to prepare polypropylene foaming material. It adopts homopolymerized or copolymerized polypropylene, or the blended resin of the two with random copolymerized polypropylene as the matrix, and is processed with chemical foaming agent AC and peroxide crosslinking agent, etc., and then foamed after irradiation. However, because polypropylene is easy to degrade, the degradation and crosslinking of polypropylene molecules will occur simultaneously during the crosslinking process, which will affect the final use and mechanical properties of the foamed material, and the cell uniformity is not easy to control.

In addition, in the prior art, there is also a method of co-foaming polypropylene with other resins with high melt strength to obtain foam materials. Such as U.S. Patent No. 5,527,573, two or more polymers of block copolymerized polypropylene, random copolymerized polypropylene, traditional polypropylene, and high melt strength polypropylene are used as the foaming matrix, and physical foaming agents such as MeCl, FC-B34, CFC-114, HCFC-1426, etc. are prepared through a single-screw extruder to produce polypropylene foam materials with a foam density less than 80kg/m3. However, due to the compatibility problem of mixing other resins, the mechanical properties and heat-resistant temperature of the foam material will drop a lot. And this patent does not disclose whether this foaming matrix is used for chemical blowing agent.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention uses a mixture of a random copolymerized polypropylene and a polypropylene with high melt strength for foaming, which can obtain high expansion ratio, uniform cells, rigidity and thermal stability Good polypropylene foam material.

The purpose of the present invention is to provide a foaming premix which can obtain a polypropylene foaming material with uniform cell structure, high foaming ratio, rigidity and thermal stability.

Another object of the present invention is to provide the preparation method of said foaming premix.

In order to achieve the above-mentioned purpose, the present invention adopts a mixture of a random copolymerized polypropylene resin (PPR) and a polypropylene with high melt strength obtained through irradiation grafting as the base resin, and through chemical foaming, high foaming Expanded polypropylene material with high foam ratio.

The polypropylene foaming premix of the present invention comprises the following components blended: polypropylene I, polypropylene II and an organic chemical foaming agent. Wherein based on 100 parts by weight of the polypropylene I, the content of the polypropylene II is 5-10 parts by weight, preferably 6-8 parts by weight.

In the polypropylene foaming premix of the present invention described above, the polypropylene I is a random copolymer of propylene and ethylene, that is, a random copolymerized polypropylene (PPR). The ethylene content of this random copolymerized polypropylene [measured by infrared (Magna-IR760, Nicolet) and nuclear magnetic (400M, Swiss AVANCE)] is 3.5 to 6.5 wt%, preferably 4.0 to 5.0 wt%; molecular weight distribution (M _w /M _n ) is 3.0 to 9.0, preferably 4.2 to 7.0 [measured by gel chromatography with GPC (150-CALC/GPC, Waters)]. Its melt index is 0.10～1.2g/10min (test instrument: melt index meter code 6942, made by Italy CDAST; test standard ASTMD1238; test condition: 230 ℃, 2.16kg), preferably 0.13～0.40g/10min; its melt Tensile strength (210°C (Rheotens 71.97, GOTTFERT, Germany, 210°C)) is 0.75-4.5N, preferably 1.35-3.50N.

In the polypropylene foaming premix of the present invention described above, the polypropylene II is polypropylene (HMSPP) with a melt index of 1-4g/10min and a melt strength of 0.25-0.60N (measured at 200°C). Its melt index is preferably 2 to 3 g/10 min. The medium polypropylene has high melt strength.

The random copolymerized polypropylene with ethylene content and molecular weight distribution in the above ranges used in the present invention has excellent melt strength and is especially suitable for preparing polypropylene foam materials from thermal decomposition type chemical blowing agents. When the chemical blowing agent decomposes, a large amount of gas and heat are generated. During the formation, growth and shaping of cells, the viscoelasticity of general polypropylene changes greatly with temperature. When the temperature increases, the viscoelasticity of polypropylene melt will rapidly increase. Reduced, the cell walls collapsed and the size was uneven, as shown in Figure 2. However, the random copolymerized polypropylene of the present invention is combined with high melt strength polypropylene to meet the viscoelastic requirements of the cell formation process and form a foam with a uniform cell structure (see accompanying drawing 1).

The polypropylene II in the polypropylene foaming premix of the present invention can adopt the polypropylene that melt index and melt strength meet above-mentioned conditions in the prior art, also can preferably adopt the method preparation that comprises the following steps:

a. uniformly mixing polypropylene and multifunctional monomers to obtain a mixture;

b. The above mixture is fully replaced with nitrogen, and irradiated under a nitrogen atmosphere;

c. Mixing the polypropylene obtained through the above steps with an antioxidant, extruding and granulating to obtain polypropylene with high melt strength.

In the above method, the multifunctional group monomer is a monomer with two or more functional groups, such as: 1,6-hexanediol diacrylate (HDDA), neopentyl glycol diacrylate (NPGDA), divinylbenzene, etc. . Based on 100 parts by weight of polypropylene, the dosage is 0.1-3.0 parts.

Compared with the raw materials used, the change ΔF of the tensile force value of the polypropylene melt obtained by this method is greater than or equal to 40cN, and the storage modulus G' is 1 to 2 times that of the blank sample.

The mixing of polypropylene and multifunctional group monomers in step a of the above-mentioned polypropylene II preparation method is common mixing, that is, using common mixing methods such as dipping and stirring to fully contact and mix the multifunctional group monomers with the polypropylene used uniform. In this method, in order to make the multi-functional group monomer and polypropylene contact and mix uniformly to achieve the purpose of effectively improving the melt strength of polypropylene, it is best to choose powdery (including spherical) polypropylene. The melt index of the raw material polypropylene is 1-5g/10min, and the melt strength is above 0.1N, preferably 0.1-0.5N (measured at 200°C).

The irradiation used in the above-mentioned preparation method of polypropylene II is selected from electron ray, gamma ray, x-ray or ultraviolet light, preferably electron ray or gamma ray. The irradiation dose is 0.2-10 kGy, preferably 0.5-5 kGy.

Free radicals still remain in the irradiated polypropylene material. According to the conventional irradiation technology, the irradiated material needs to eliminate free radicals, so as to prevent the residual free radicals from interacting with oxygen to degrade polypropylene. Therefore, the irradiated materials are generally placed in a nitrogen atmosphere at room temperature for several days, or at high temperature for several hours. The present invention generally treats the irradiated polypropylene at 100C for 2 hours to eliminate residual free radicals.

In the polypropylene foaming premix of the present invention described above, various organic chemical foaming agents suitable for polypropylene foaming in the prior art can be used as the organic chemical foaming agent. Its general decomposition temperature is 180-240°C, preferably 190-230°C. They include, but are not limited to, azodicarbonamide (AC), azobisisobutyronitrile, N,N-dinitrosopentamethylenetetramine (BN), p-toluenesulfonamidourea, and the like. The amount used is the usual amount, or adjusted according to the requirements of the actual situation. The content of the organic chemical blowing agent in the premix of the present invention is preferably 2-6 parts by weight, more preferably 3-5 parts by weight, based on 100 parts by weight of the polypropylene I.

The above-mentioned polypropylene foaming premix of the present invention may also include inorganic fillers. Inorganic fillers include solid particles of inorganic salts and metal oxides, which can be selected from silica, talc, calcium carbonate, zinc oxide or magnesium oxide. Inorganic fillers are used here as nucleating agents, which are as important to the foaming process as zeolites are in boiling liquids. To be precise, inorganic fillers form hot spots during foaming, that is, bubble growth points. When the blowing agent decomposes, bubbles can be formed at the bubble growth points. Inorganic fillers play an important role in the uniform distribution and stable growth of cells. The amount of inorganic fillers can be used in conventional amounts, or adjusted according to the requirements of actual conditions. The cell size can be controlled by adjusting the amount of inorganic filler. If the amount is too high, it will become a filler, but it will not work as a hot spot. Therefore, the amount of inorganic filler in the premix of the present invention is based on 100 parts by weight of polypropylene I, preferably 0.5-5 parts by weight, more preferably 0.5-1.0 parts by weight. The average particle size of the inorganic filler is generally 1250 mesh or above.

The above-mentioned polypropylene foaming premix of the present invention may also include processing aids commonly used in the existing foaming technology to facilitate stable foaming, such as liquid additives. The liquid additive plays the role of lubricating during the extrusion process and adjusting the cells during foaming. Its addition is beneficial to the extrusion of the foaming material and also helps to form uniform, stable, and controllable cells. Here, the liquid auxiliary agent is a liquid low-molecular-weight linear hydrocarbon or a liquid low-molecular-weight organosilicon compound, preferably white oil, liquid paraffin or silicone oil. Its dosage can adopt conventional dosage, or be adjusted according to the requirement of actual situation. Adding too little liquid additive will not be effective, and too much will be unfavorable for processing. Therefore, the amount of liquid additives in the premix of the present invention is preferably 0.1 to 1, more preferably 0.2 to 0.5, based on 100 parts by weight of polypropylene.

In addition, the polypropylene foaming premix of the present invention may also include other commonly used additives for plastic processing, such as antioxidants, flame retardants and the like. The amount used is the usual amount, or adjusted according to the requirements of the actual situation.

The preparation method of the polypropylene foaming premix of the present invention comprises the following steps: melt blending the components including the polypropylene I, the polypropylene II and the organic chemical foaming agent. Wherein based on 100 parts by weight of the polypropylene I, the content of the polypropylene II is 5-10 parts by weight, preferably 6-8 parts by weight.

The method of the present invention is usually to mix the components together homogeneously, and then carry out melt blending. However, in order to fully blend the two polypropylene resins in the foaming premix and to make the matrix resin uniform in texture, it is preferable to mix the components including the above two polypropylene resins evenly for melt blending; The obtained blend is uniformly mixed with the components including the organic chemical blowing agent for melt blending.

In the preparation method of the polypropylene foam premix of the present invention described above, the polypropylene I is the aforementioned random copolymerized polypropylene. The ethylene content of this random copolymerized polypropylene [measured by infrared (Magna-IR760, Nicolet) and nuclear magnetic (400M, Swiss AVANCE)] is 3.5 to 6.5 wt%, preferably 4.0 to 5.0 wt%; molecular weight distribution (M _w /M _n ) is 3.0 to 9.0, preferably 4.2 to 7.0 [measured by gel chromatography with GPC (150-CALC/GPC, Waters)].

In the above-mentioned preparation method of the polypropylene foaming premix of the present invention, the polypropylene II adopts polypropylene (HMSPP) with a melt index of 1-4 g/10 min and a melt strength of 0.25-0.60N. Its melt index is preferably 2 to 3 g/10 min. The medium polypropylene has high melt strength. This kind of polypropylene can adopt the polypropylene whose melt index and melt strength meet the above-mentioned conditions in the prior art, and can also be prepared according to the above-mentioned method.

In the above-mentioned preparation method of the polypropylene foaming premix of the present invention, various organic chemical foaming agents suitable for polypropylene foaming in the prior art can be used as the organic chemical foaming agent. Its general decomposition temperature is 180-240°C, preferably 190-230°C. They include, but are not limited to, azodicarbonamide (AC), azobisisobutyronitrile, N,N-dinitrosopentamethylenetetramine (BN), p-toluenesulfonamidourea, and the like. The amount used is the usual amount, or adjusted according to the requirements of the actual situation. In the present invention, the content of the organic chemical foaming agent is preferably 2-6 parts by weight, more preferably 3-5 parts by weight, based on 100 parts by weight of the polypropylene I.

In the above-mentioned preparation method of the polypropylene foaming premix of the present invention, processing aids commonly used in the existing foaming technology may also be included to facilitate stable foaming.

The aforementioned inorganic fillers that function as nucleating agents may include solid particles of inorganic salts and metal oxides. It can be selected from silicon dioxide, talc, calcium carbonate, zinc oxide or magnesium oxide, etc. The amount used is the usual amount, or adjusted according to the requirements of the actual situation. In the present invention, the amount of the inorganic filler is preferably 0.5-5 parts by weight, more preferably 0.5-1.0 parts by weight based on 100 parts by weight of the polypropylene I. Generally 1250 mesh or above.

As mentioned above, the liquid additives used for lubricating during extrusion and adjusting cells during foaming can be liquid low-molecular linear hydrocarbons or liquid low-molecular organosilicon compounds, preferably white oil, liquid paraffin or silicone oil. The amount used is the usual amount, or adjusted according to the requirements of the actual situation. In the present invention, the amount of the liquid additive is preferably 0.1-1, more preferably 0.2-0.5 based on 100 parts by weight of the polypropylene I.

In addition, the formulation components involved in the method of the present invention may also include other commonly used additives for plastic processing, such as antioxidants, flame retardants, and the like.

In the above-mentioned preparation method of the present invention, various mixing equipment used in the prior art can be used as the equipment for mixing materials before melt blending, such as mixers, kneaders, etc.

The melt blending equipment used in the above method of the present invention is a general blending equipment in the rubber and plastic processing industry, which can be a twin-screw extruder, a single-screw extruder, an open mill or an internal mixer.

The melt blending used in the method of the present invention can adopt the process and equipment in the prior art, such as the blending temperature is generally controlled at 155 ~ 175 ° C; the melt blending equipment can use the general blending equipment in the rubber and plastic processing industry , can include an open mill, an internal mixer, a single-screw extruder or a twin-screw extruder, etc.

The profiles obtained after molding the polypropylene foam premix of the present invention can be heated and foamed at a constant temperature to obtain desired polypropylene foam products. The molding process used is the common plastic molding process in the prior art, including tablet molding or direct extrusion molding, injection molding or molding by other methods. The obtained profiles include sheet materials, profiled materials, etc., usually sheet materials . The constant temperature foaming process used can adopt the equipment and process conditions used in the foaming of organic chemical foaming agents in the prior art. General heating can be selected to heat and foam at a constant temperature in an oven or a foaming furnace, or to heat and pressurize on a press to foam. The foaming temperature is controlled at 195-235° C., preferably 210-235° C. by constant temperature heating and foaming in an oven or a foaming furnace; the foaming time is 3-10 minutes, preferably 4-8 minutes. The temperature of the press heating and pressurizing foaming is controlled at 200-255°C, preferably 210-235°C; the pressure is 0.5-5Mpa; the foaming time is 3-10 minutes, preferably 4-8 minutes.

The expansion ratio of the polypropylene foam thus obtained is 7 to 12 times, preferably 9 to 12 times. The bulk density of the foam is 75-129Kg/m ³ .

The foamed material obtained after conventional foaming of the polypropylene foamed premix described in the present invention has good cell structure, uniform pore diameter, and a foaming ratio of 7 to 12 times, preferably 9 to 12 times. The bulk density of the foam is 75-129Kg/m ³ . At the same time, it has the advantages of high modulus and good thermal stability. It is suitable for energy saving, sound insulation, shock absorption and buffering, etc., and has broad application prospects in many fields such as automobiles, refrigeration, building materials, packaging, transportation, and agriculture.

The preparation method of the foamed polypropylene material of the present invention does not need to carry out cross-linking, so the process is simple and the product cost is low.

Description of drawings

Fig. 1 is the scanning electron micrograph of the polypropylene foam material of embodiment 2, magnification 12 times.

Fig. 2 is a scanning electron micrograph of the polypropylene foam material of Comparative Example 5, with a magnification of 13 times.

Detailed ways

The present invention is further described below with examples, but the scope of the present invention is not limited by these examples. The scope of the present invention is set forth in the claims.

Embodiment 1～2

Polypropylene I—— random copolymerized polypropylene (PPR origin: Yanshan Petrochemical Co., Ltd., ethylene content: 4.1wt%, molecular weight distribution: 5.2, melt index: 0.223g/10min, melt tensile strength: 1.98N measured at 190°C, 210 ℃ 1.40N, 230 ℃ 1.1N), polypropylene II - high melt strength polypropylene (melt index 2.35g/10min, melt tensile strength 200 ℃ 0.29N, self-made), organic chemical foaming agent It is uniformly mixed with various processing aids through a high-speed mixer, and then melted and blended through a twin-screw extruder, extruded and granulated. Then, it is molded by an extruder die to form a sheet with a thickness of 2 to 6 mm, and the blending temperature is 155 to 175° C. The sheet is heated and foamed on a heating tunnel, the foaming temperature is 200-255° C., and the foaming time is 3-10 minutes. Then cool to obtain a foamed sheet with a thickness of 3-15 mm. Wherein the organic chemical foaming agent is azodicarbonamide (AC, Tianjin No. 1 Organic Chemical Plant), and the inorganic filler in the processing aid is silicon dioxide (SiO2, produced by Capote, Germany, with an average particle size of 2500 mesh) , The liquid additives are white oil (Beijing Organic Chemical Factory), antioxidants (1010, 168, produced by Ciba Jiaji, Switzerland). Prescription sees Table 1 in terms of 100 parts by weight of polypropylene. The performance test results and test standards of the samples are shown in Table 1.

The preparation method of the above polypropylene II - high melt strength polypropylene (melt index 2.35g/10min, melt tensile strength 0.34N at 190°C, 0.34N at 210°C, 0.31N at 230°C):

Add 0.35 parts of 1,6-hexanediol diacrylic acid based on 100 parts by weight of polypropylene to polypropylene powder (Tianjin Second Petrochemical Plant, melt index 4g/10min, melt strength 0.17N at 200°C) Esters (commercially available), mixed on a high speed mixer (1500 rpm) for 10 minutes, charged to a container. It was then fully replaced with nitrogen and sealed. Then irradiate with cobalt source, the irradiation dose is 1.0kGy. The irradiated material is treated at 100°C for 2 hours, taken out after cooling down, extruded and granulated to obtain the high melt strength polypropylene.

Its parameters are measured: the storage modulus G' is measured on the ARES rotational rheometer, the measurement temperature is 200°C, the shear rate is 0.01 seconds/rad, the G' of the raw material polypropylene is 18 Pas, and the high melt strength polypropylene G' It is 47Pas. Measure the melt strength on the melt strength instrument of Geottfert Werkstoff Pruefmaschinen Company in Germany, the melt measurement temperature is 200°C, and the measured tensile force value change ΔF is 13.3cN (the tensile force value of the pure material before the polypropylene is not modified is 0.17N, and the tensile force value after modification by the experimental conditions of this embodiment is 0.29N).

Example 3

Except that random copolymerized polypropylene is produced by Qilu Petrochemical (ethylene content: 4.3wt%, molecular weight distribution: 4.2, melt index: 0.135g/10min, melt tensile strength: 1.9N at 190°C, 1.3N at 210°C, 1.0 at 230°C N) except that all the other components, consumption and processing conditions are the same as in Example 1. The formula and sample performance test results are shown in Table 1.

Comparative example 1~2

Except not adding polypropylene II---high melt strength polypropylene, all other components, dosage and process conditions are the same as in Example 1. The formula and sample performance test results are shown in Table 1.

Comparative example 3

Except not adding polypropylene II---high melt strength polypropylene, all other components, dosage and process conditions are the same as in Example 3. The formula and sample performance test results are shown in Table 1.

Comparative example 4

Except that random copolymerized polypropylene was replaced by block copolymerized polypropylene 1330 (ethylene content: 8.9 wt%) produced by Yanshan Petrochemical Co., Ltd., other components, dosage and process conditions were the same as in Example 1. The formula and sample performance test results are shown in Table 1.

Comparative Example 5

Except that polypropylene II—high melt strength polypropylene was not added, the other components, dosage and process conditions were the same as in Comparative Example 4. The formula and sample performance test results are shown in Table 1.

The table standard of sample performance test in above-mentioned embodiment, comparative example is as follows:

Bulk density GB/T6343-86

Foaming ratio material The ratio of the density after foaming to the density before foaming

Bending strength GB/T8812-88

Dimensional Thermal Stability ISO2796

Table 1 unit Example 1 Comparative example 1 Example 2 Comparative example 2 Example 3 Comparative example 3 Comparative example 4 Example 4 Example 5 Comparative Example 5 Yanshan PPR parts by weight 100 100 100 100 - - - 100 100 - Qilu PPR parts by weight - - - - 100 100 - - - - PP1330 parts by weight - - - - - - 100 - - 100 HMSPP parts by weight 8 - 8 - 8 - 8 5 10 - AC parts by weight 3 3 5 5 5 5 5 5 5 5 SiO ₂ ? 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 antioxidant ? 1 1 1 1 1 1 1 1.0 1.0 1 white oil ? 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 cell structure - excellent generally excellent generally excellent generally Difference excellent excellent Difference Foam density kg/ ^m3 129 150 75 90 101 107 748 80 87 802 Expanding ratio - 7.05 6.01 12.01 10.02 8.92 8.43 1.20 11.4 10.5 1.12 Bending strength MPa 0.99 1.04 0.71 0.79 0.83 0.85 - ^* 0.73 0.77 - ^* Dimensional Thermal Stability % 0.4 0.4 0.8 0.7 0.6 0.5 - 0.8 0.7 -

^* Note: Due to the poor uniformity of the cell structure, it is difficult to meet the sample preparation requirements for the bending strength test, so the data in this column cannot be obtained.

As can be seen from the test results in Table 1, the foamed material obtained by using the random copolymerized polypropylene described in the present invention and coordinating high-melt strength polypropylene as the base resin for foaming has low bulk density and high expansion ratio. Good rigidity and heat resistance. It can be seen from the photo of accompanying drawing 1 that the foamed polypropylene material obtained in Example 2 of the present invention has a uniform pore size distribution and a thin and uniform cell wall thickness. It can be seen from the photo of accompanying drawing 2 that the foamed polypropylene material obtained in Comparative Example 5 has uneven pore size distribution, thick cell wall thickness, and uneven wall thickness. After comparison, it can be seen that the foamed polypropylene material obtained by the present invention has a good cell structure, which is better than that of the comparative example.

Claims (9)

1. polypropylene foaming premix includes the following component of blend: polypropylene I, polypropylene II and organic chemistry whipping agent; Described polypropylene I is that ethylene content is 3.5～6.5wt%, and molecular weight distribution is 3.0～9.0 atactic copolymerized polypropene; Described polypropylene II is that melting index is that 1～4g/10min, melt strength are the polypropylene of 0.25～0.60N; Be 100 parts by weight in polypropylene I wherein, polypropylene II content is 5～10 parts by weight.

2. polypropylene foaming premix according to claim 1 is 100 parts by weight in polypropylene I wherein, and polypropylene II content is 6～8 parts by weight.

3. polypropylene foaming premix according to claim 1 is characterized in that ethylene content is 4.0～5.0wt% in the atactic copolymerized polypropene of described polypropylene I.

4. polypropylene foaming premix according to claim 1, the molecular weight distribution that it is characterized in that the atactic copolymerized polypropene of described polypropylene I is 4.2～7.0.

5. polypropylene foaming premix according to claim 1, the melting index that it is characterized in that the atactic copolymerized polypropene of described polypropylene I is 0.10～1.2g/10min, the melt tensile strength is 0.75～4.50N.

6. polypropylene foaming premix according to claim 1, the melting index that it is characterized in that described polypropylene II is 2～3g/10min.

7. polypropylene foaming premix according to claim 1 is characterized in that described organic chemistry whipping agent is Cellmic C 121 or Diisopropyl azodicarboxylate.

8. according to the preparation method of each described polypropylene foaming premix of claim 1～7, comprise the component that includes described polypropylene I, polypropylene II, organic chemistry whipping agent is carried out melt blending by described component concentration.

9. the preparation method of polypropylene foaming premix according to claim 8 may further comprise the steps:

1. will include described polypropylene I, polypropylene II and carry out melt blending, wherein not contain the organic chemistry whipping agent in the component in interior component;

2. the polypropylene miser that above-mentioned steps is obtained with include described organic chemistry whipping agent and mix in interior component and carry out melt blending.

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