A non-weakening polypropylene foam for airbag explosion, preparation method, application and laminated skin material

Abstract

The present invention discloses a non-weakening polypropylene foam for airbag blasting, a preparation method, an application, and a laminated skin material, which relates to the technical field of automotive interior skin. To solve the problem of irregular tearing of the polypropylene foam in the skin material during airbag blasting; the cohesive force of the polypropylene foam of the present invention is 20-25 N / 1.5 cm. The raw materials of the polypropylene foam include 50-80 parts by weight of homopolypropylene, 20-30 parts by weight of block copolymerized polyethylene, 5-10 parts by weight of ethylene propylene diene monomer rubber, 1-2 parts by weight of a crosslinking agent, 1-2 parts by weight of an antioxidant, and 4-8 parts by weight of an ADCA blowing agent; the present invention realizes the improvement of the cohesive force of the polypropylene foam. After being made into a laminated skin material, it can be applied to the area of the automotive interior airbag, ensuring that when the airbag blasts and unfolds, the skin material tears regularly according to the shape of the airbag box.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive interior skin, especially copolymer laminated products, and specifically to a non-weakening polypropylene foam for airbag blasting, a preparation method, an application, and a laminated skin material. Background Art

[0002] In recent years, due to considerations such as the feel and aesthetic effect of automotive interiors, more and more large-area automotive interiors such as instrument panels and door panels have been designed as integral types. Especially in the airbag area, an integral skin design is also adopted. By using non-weakening airbag blasting materials, the TPO instrument panel can have better tensile strength and is more likely to rupture under blasting impact, ensuring the normal opening of the airbag.

[0003] Polypropylene foam has compressibility. After being bonded to a plastic skeleton, it can effectively cover some burrs and defects on the plastic skeleton. At the same time, it can improve the soft touch of support. And it can obtain good blasting effects without skin weakening. Therefore, polypropylene foam has become an excellent choice for the skin material of the airbag part in automotive interiors.

[0004] However, in actual applications, a large number of new technical problems still occur. For example, Figure 3 As shown, the deployment direction of airbag blasting deviates, resulting in an angular deviation in the deployment direction of the airbag. When the vehicle is impacted and the vehicle occupants need the correct protection of the airbag, this deviation is very likely to cause the airbag to fail to achieve the designed safety effect. Another example is Figure 4 As shown, when the airbag blasts, excessive flying objects are generated under the huge impact force. This situation may also lead to safety non-compliance and may cause accidental injuries to vehicle occupants facing the airbag directly.

[0005] After analysis, usually the bonding force between polypropylene foam and the TPO skin layer and the substrate is not a problem. However, when the airbag blasts and deploys, the skin material still fails to tear regularly along the direction specified by the airbag box. After more in-depth detailed analysis and research, it is found that the irregular tearing starts from the inside of the polypropylene foam itself. In addition to the above two problem situations, when the polypropylene foam tears irregularly, the huge impact force of airbag blasting may also break or shatter the weak parts of the skeleton. There are two possible ways in the prior art to solve this problem. One is to increase the density of the polypropylene foam, but this method not only has poor effects but also increases a lot of production costs. The other is to increase the hardness of the polypropylene foam, but nowadays, automotive interiors pursue a soft touch, and hard materials have gradually been phased out. Therefore, there is an urgent need for a non-weakening polypropylene foam for airbag blasting, a preparation method, an application, and a laminated skin material to solve this problem. Summary of the Invention

[0006] The object of the present invention is to provide a non-weakening polypropylene foam for airbag blasting, a preparation method, an application and a laminated skin material, so as to solve the problem of irregular tearing of the polypropylene foam in the skin material during airbag blasting.

[0007] To achieve the above object, the present invention provides the following technical solution: a non-weakening polypropylene foam for airbag blasting, the cohesive force of the polypropylene foam is 20-25 N / 1.5 cm, and the raw materials of the polypropylene foam include 50-80 parts by weight of homopolypropylene, 20-30 parts by weight of block copolymerized polyethylene, 5-10 parts by weight of ethylene propylene diene monomer rubber, 1-2 parts by weight of crosslinking agent, 1-2 parts by weight of antioxidant, and 4-8 parts by weight of ADCA blowing agent;

[0008] The melt index of the homopolypropylene is measured to be 1-8 g / 10 min at 230 °C under a load of 2.16 kg, the density is 0.89-0.91 g / cm 3 , and the softening temperature ≥ 135 °C;

[0009] The melt index of the block copolymerized polyethylene is measured to be 1-3 g / 10 min at 190 °C under a load of 2.16 kg, the melting point is 105-115 °C, and the hardness is 55-65 A.

[0010] Preferably, the main body of the above block copolymerized polyethylene is C2, and the comonomer is C8.

[0011] Preferably, the melt index of the above ethylene propylene diene monomer rubber is measured to be 1-3 g / 10 min at 190 °C under a load of 2.16 kg, the Mooney viscosity is 20-40, and the density is 0.89-0.91 g / cm 3 .

[0012] Preferably, the viscosity of the above crosslinking agent at room temperature is 40-70 mPa·s, the antioxidant is a hindered phenol antioxidant, the moisture content of the ADCA blowing agent ≤ 1%, and the gas evolution is 140-160 mL / g.

[0013] Preferably, the thickness of the above polypropylene foam is 1.5-3.0 mm; the density is 50-100 kg / m 3 ; the tensile strength MD is 1200-1800 kPa, CD is 200-700 kPa; the elongation at room temperature MD ≥ 300%, CD ≥ 250%; the elongation at 120 °C MD ≥ 800%, CD ≥ 600%; the 25% compression strength is 80-150 kPa.

[0014] Another technical solution provided by the present invention: A method for preparing polypropylene foam, comprising the following steps: putting the above raw materials into an extruder according to a set ratio, fully plasticizing and mixing them, and then extruding them into sheets through a mold. During the process, the melt temperature is controlled to ensure that the foaming agent does not decompose in the extruder; irradiating the sheets to make the crosslinking agent fully react and crosslink; using a vertical foaming furnace for foaming production, where the horizontal section is used to preheat the sheets, and the vertical section is the foaming section. After foaming, it is cooled and shaped.

[0015] Preferably, in the above preparation method, the melt temperature in the extruder ≤ 180 °C; double-layer irradiation is used for irradiation, and the dose is 30 - 40 KGy; the temperature of the preheating section is 200 - 240 °C, and preheating is carried out for 40 - 60 seconds; the temperature of the foaming section is 300 - 400 °C, and heating is carried out for 10 - 20 seconds.

[0016] Another technical solution provided by the present invention: A polypropylene foam is applied to the skin material in the airbag area of automotive interiors to ensure that when the airbag bursts and unfolds, the skin material tears regularly according to the shape of the airbag box.

[0017] Still another technical solution provided by the present invention: A laminated skin material, comprising a polypropylene foam layer and a TPO skin layer attached to a substrate, wherein the polypropylene foam layer uses the above polypropylene foam and is located between the substrate and the TPO skin layer.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] The polypropylene foam for airbag bursting, preparation method, application and laminated skin material, by specifically adjusting the properties of homopolypropylene and block copolymerized polyethylene themselves to a suitable range, combined with corresponding improvements in other ingredients and preparation methods, realizes the improvement of the cohesive force of the polypropylene foam. After the polypropylene foam of the present invention is made into a laminated skin material, it can be applied to the airbag area of automotive interiors. When the airbag bursts and unfolds, the skin material tears regularly according to the shape of the airbag box, ensuring that the safety measures can effectively achieve their design effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic structural diagram of the laminated material of the present invention;

[0021] Figure 2 It is the result of the airbag bursting test for Example 1 of the present invention;

[0022] Figure 3 It is the result of the airbag bursting test for Comparative Example 1;

[0023] Figure 4 It is the result of the airbag bursting test for Comparative Example 2.

[0024] In the figure: 1. TPO skin layer; 2. Polypropylene foam layer; 3. Substrate. Detailed implementation mode

[0025] Refer to Figure 1 , a non-weakening laminated skin material for airbag blasting, including a polypropylene foam layer and a TPO skin layer attached to a substrate. The substrate can generally be a plastic skeleton. The polypropylene foam layer is located between the substrate and the TPO skin layer, and is bonded to the TPO surface on one side. Usually, the TPO material is softened by high temperature and then hot-pressed to bond with the polypropylene foam layer. It is bonded to the skeleton on the other side. The bonding method can be to pre-spray glue on the plastic skeleton, and then on a vacuum forming machine, the heated composite material is vacuum thermoformed onto the plastic skeleton, and the glue is activated at high temperature and set after cooling; the TPO skin layer can use conventional TPO skin materials, such as those composed of modified polypropylene, low-density polyethylene, and ethylene propylene diene monomer, and are mixed on a co-rotating twin-screw extruder and extruded into a film material from the die orifice.

[0026] In the present invention, the most important thing is that the cohesive force of the polypropylene foam layer needs to be 20 - 25 N / 1.5 cm (the polypropylene foam in the prior art is mostly 10 - 15 N / 1.5 cm). Through experiments, regular tearing can be achieved in this way. The cohesive force is measured by the following method: Take a long strip-shaped specimen with a width of 15 mm and a length of 200 mm, then cut it from the middle of one end of the long strip with a knife, pre-peel 20 mm, and then use upper and lower clamps to clamp both ends of the peeled part, and stretch it on a tensile machine at a speed of 50 mm / min, and record the N force value; and in order to achieve this target property, the raw materials of the polypropylene foam layer include 50 - 80 parts by weight of homopolypropylene, 20 - 30 parts by weight of block copolymerized polyethylene, 5 - 10 parts by weight of ethylene propylene diene monomer, 1 - 2 parts by weight of crosslinking agent, 1 - 2 parts by weight of antioxidant, and 4 - 8 parts by weight of ADCA blowing agent; among them, the melt index of homopolypropylene is measured at 1 - 8 g / 10 min under a load of 2.16 kg at 230 °C, and the density is 0.89 - 0.91 g / cm 3 , the softening temperature ≥ 135 °C; the melt index of block copolymerized polyethylene is measured at 1 - 3 g / 10 min under a load of 2.16 kg at 190 °C, the melting point is 105 - 115 °C, and the hardness is 55 - 65 A.

[0027] For reference, the main body of the above-mentioned block copolymer polyethylene is C2, and the comonomer can be C8, wherein C8 is regularly arranged on the main chain of the C2 polymer, and it has the characteristics of high strength, low hardness and high melting point, but this is only a feasible solution. The implementer can adjust the structure of the block copolymer polyethylene according to the above-mentioned specific cohesion and MFR and other parameters. Under the idea provided by the present invention, the purpose of regular tearing can also be achieved, but the choice provided by the present invention also has the following advantages for reference when selecting other block copolymer polyethylenes: better toughness; due to the longer side chains of C8, it is easier to react with the crosslinking agent during radiation crosslinking, and it is easy to achieve a higher reasonable crosslinking degree at a low radiation dose; high melting point, which is conducive to the high temperature (85°C) burst test of the airbag.

[0028] Optionally, the melt index of the EPDM rubber is 1-3 g / 10 min at 190° C. and a load of 2.16 kg, the Mooney viscosity is 20-40, and the density is 0.89-0.91 g / cm 3 .

[0029] Optionally, the viscosity of the cross-linking agent at room temperature is 40-70 mPa.s, the antioxidant is a hindered phenol antioxidant, the water content of the ADCA foaming agent is ≤1%, and the gas release volume is 140-160 mL / g.

[0030] In a preferred embodiment, the thickness of the polypropylene foam layer can be 1.5 to 3.0 mm; the density can be 50 to 100 kg / m 3 ; The tensile strength can be MD 1200~1800kPa, CD 200~700kPa; the elongation at room temperature can be MD≥300%, CD≥250%; the elongation at 120℃ can be MD≥800%, CD≥600%; the 25% compressive strength can be 80~150kPa.

[0031] In the above-mentioned layered skin material, the preparation method of polypropylene foam comprises:

[0032] Put all raw materials (homopolymer polypropylene, block copolymer polyethylene, EPDM rubber, crosslinking agent, antioxidant, ADCA foaming agent) into the extruder according to the set ratio, preferably a co-rotating twin-screw extruder, and the liquid crosslinking agent is preferably fed with a high-precision liquid feeding pump. After being fully plasticized and mixed, it is extruded into a sheet through a die. During the process, the melt temperature is controlled to ensure that the foaming agent will not decompose in the extruder. For reference, the melt temperature in the extruder should be below 180°C;

[0033] Irradiate the material, preferably double-layer irradiation, the dose is preferably controlled at 30-40 KGy, specifically, an electron irradiation accelerator can be used to allow the crosslinking agent to fully react and crosslink;

[0034] A vertical foaming furnace is used for foaming production, in which the horizontal section is used to preheat the sheet, and the vertical section is the foaming section. Natural gas heating and infrared heating can be used as heat sources. For reference, the preheating section temperature is 200-240°C, preheating for 40-60 seconds, and the foaming section temperature is 300-400°C, heating for 10-20 seconds; after foaming, it is cooled and set.

[0035] In the following embodiments, homopolymer polypropylene is made of Korea Petrochemical, brand HJ4006; block copolymer polyethylene is made of C2 (ethylene) as the main body and C8 (octene) as the comonomer, wherein C8 is regularly arranged on the main chain of the C2 polymer, specifically Dow Chemical, brand 9107; EPDM is made of Dow Chemical, brand 4820P; the crosslinking agent is made of >99.9% trimethylolpropane trimethacrylate, specifically BASF, brand TMPTMA, the antioxidant is made of >99.9% pentaerythritol tetrakis (3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate), specifically BASF, brand IRGANOX 1010, and the ADCA foaming agent is calculated by weight percentage, 50-55% azodicarbonamide, and 45-50% low-density polyethylene carrier, specifically Lei Fus, brand 5038.

[0036] Embodiment 1:

[0037] 60 parts of homopolymer polypropylene, 30 parts of block copolymer polyethylene, 5 parts of ethylene propylene diene monomer rubber, 1 part of cross-linking agent, 1 part of antioxidant and 5 parts of ADCA foaming agent are weighed by weight, and the materials except the cross-linking agent are put into a co-rotating twin-screw extruder, and the cross-linking agent is fed by a high-precision liquid feeding pump. After being fully plasticized and mixed, the sheet is extruded through a mold; an electron irradiation accelerator is used to irradiate the sheet so that the cross-linking agent fully reacts and cross-links; a vertical foaming furnace is used for foaming production, with a preheating stage of 220°C for 40 seconds and a foaming stage of 350°C for 20 seconds; after foaming, the sheet is shaped by a cooling guide roller to obtain a polypropylene foam.

[0038] Its two sides are bonded to the plastic skeleton substrate and TPO skin layer respectively, and an airbag is installed under the substrate. The burst test results are as follows Figure 2 As shown; the cohesive force of the polypropylene foam is measured to be about 24N / 1.5cm.

[0039] Embodiment 2:

[0040] 70 parts of homopolymer polypropylene, 30 parts of block copolymer polyethylene, 10 parts of ethylene propylene diene monomer rubber, 2 parts of crosslinking agent, 2 parts of antioxidant and 6 parts of ADCA foaming agent are weighed by weight, and the materials except the crosslinking agent are put into a co-rotating twin-screw extruder, and the crosslinking agent is fed by a high-precision liquid feeding pump. After being fully plasticized and mixed, the sheet is extruded through a mold; an electron irradiation accelerator is used to irradiate the sheet so that the crosslinking agent fully reacts and crosslinks; a vertical foaming furnace is used for foaming production, with a preheating stage of 200°C for 50 seconds and a foaming stage of 300°C for 20 seconds; after foaming, the sheet is shaped by a cooling guide roller to obtain a polypropylene foam.

[0041] Its two sides are bonded to the plastic skeleton substrate and the TPO skin layer respectively, and an air bag is installed under the substrate. The bursting test results are basically the same as those in Example 1; the cohesive force of the polypropylene foam is measured to be about 21N / 1.5cm.

[0042] Embodiment 3:

[0043] 50 parts of homopolymer polypropylene, 20 parts of block copolymer polyethylene, 5 parts of ethylene propylene diene monomer rubber, 2 parts of crosslinking agent, 1 part of antioxidant and 4 parts of ADCA foaming agent are weighed by weight, and the materials except the crosslinking agent are put into a co-rotating twin-screw extruder, and the crosslinking agent is fed by a high-precision liquid feeding pump. After being fully plasticized and mixed, the sheet is extruded through a mold; an electron irradiation accelerator is used to irradiate the sheet so that the crosslinking agent fully reacts and crosslinks; a vertical foaming furnace is used for foaming production, with a preheating stage of 220°C for 40 seconds and a foaming stage of 400°C for 10 seconds; after foaming, the sheet is shaped by a cooling guide roller to obtain polypropylene foam.

[0044] Its two sides are bonded to the plastic skeleton substrate and the TPO skin layer respectively, and an air bag is installed under the substrate. The bursting test results are basically the same as those in Example 1; the cohesive force of the polypropylene foam is measured to be about 23N / 1.5cm.

[0045] Comparative Example 1:

[0046] According to the weight fraction, 86 parts of EPDM rubber (Kumho, 570P), 20 parts of polypropylene (ExxonMobil, 7032), 15 parts of ethylene-acrylate copolymer (BASF, VMX5020), 22 parts of paraffin oil (Wantai Chemical, paraffin oil) and 7 parts of talc (Xinda Talc, 92876) were plasticized at a roller temperature of 75°C and a plasticizing speed of 2min / kg, and then refined into sheets at a refining temperature of 60°C and a refining speed of 2min / kg, and then granulated to obtain modified EPDM rubber;

[0047] By weight fraction, 80 parts of polypropylene (Sinopec, 1806), 2.5 parts of nano calcium carbonate (Liangjiang Chemical Industry, 400 mesh), 6 parts of ethylene-octene copolymer (Dow, 8480), and 12 parts of ethylene-acrylate copolymer (BASF, VMX5020) were put into a mixer and kneaded at 180 °C for 10 min, then extruded at 180 °C and pelletized to obtain modified polypropylene;

[0048] For the raw material of polypropylene foam, by weight fraction, 21 parts of the above-mentioned modified polypropylene, 70 parts of the above-mentioned modified ethylene propylene diene monomer rubber, 27 parts of low-density polyethylene (Formosa Plastics, 3224), 2.5 parts of AC blowing agent (Jieshangjie, LD50S), and 2 parts of masterbatch (Aomeikai, 6006);

[0049] Using a preparation process as similar as possible to the example, the materials were put into a co-rotating twin-screw extruder, fully plasticized and mixed, and then extruded into sheets through a die; Vertical foaming furnace was used for foaming production, with a preheating section at 220 °C for 40 seconds and a foaming section at 350 °C for 20 seconds; After foaming, it was shaped by a cooling guide roller to obtain polypropylene foam.

[0050] Bond its two sides to the same plastic skeleton substrate and TPO skin layer as in the example respectively. An airbag is installed under the substrate, and the blasting test results are as Figure 3 shown; After measurement, the cohesion of this polypropylene foam is about 13 N / 1.5 cm.

[0051] Comparative Example 2:

[0052] Polypropylene resin (Sinopec, 1806), rubber (Dawn, D85), toughening agent (Dow Chemical, 8842), blowing agent (Jieshangjie, LD50S), lubricant (Kline, 4201), and antioxidant (BASF, grade IRGANOX 1010) were added to the hopper of a twin-screw extruder for melting, kneading, and extrusion. The screw temperature of the twin-screw extruder was controlled at 250 °C. The raw materials extruded from the twin-screw extruder were drawn, cooled, and dried to obtain polypropylene foam.

[0053] Bond its two sides to the same plastic skeleton substrate and TPO skin layer as in the example respectively. An airbag is installed under the substrate, and the blasting test results are as Figure 4 shown.

[0054] It can be seen from the airbag explosion test results of the embodiments and comparative examples that the tearing edges of the method of the present invention are regular and are all torn along the edge of the airbag box, with significant effects. The principle is mainly to improve the cohesive force of the polypropylene foam through special raw materials and proportions, combined with a suitable preparation method, so that it is not easy to break from the middle of the foam layer. In summary, after the polypropylene foam of the present invention is made into a layered skin material, it can be applied to the automotive interior safety airbag area to ensure that when the airbag explodes and deploys, the skin material is torn according to the shape of the airbag box, thereby ensuring that the safety measures can effectively achieve their designed effects.

[0055] The above are only preferred embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope defined by the claims.

[0056] The matters not described in detail in the present invention are all known technologies to those skilled in the art.

Claims

1. A non-weakening polypropylene foam for airbag blasting, characterized in that: The cohesive force of the polypropylene foam is 20-25 N / 1.5 cm. The raw materials of the polypropylene foam include 50-80 parts by weight of homopolypropylene, 20-30 parts by weight of block copolymerized polyethylene, 5-10 parts by weight of ethylene propylene diene monomer rubber, 1-2 parts by weight of crosslinking agent, 1-2 parts by weight of antioxidant, and 4-8 parts by weight of ADCA blowing agent; The melt index of the homopolypropylene is measured to be 1-8 g / 10 min under a load of 2.16 kg at 230 °C, and the density is 0.89-0.91 g / cm 3 , and the softening temperature is ≥135 °C; The melt index of the block copolymerized polyethylene is measured to be 1-3 g / 10 min under a load of 2.16 kg at 190 °C, the melting point is 105-115 °C, and the hardness is 55-65 A; The main body of the block copolymerized polyethylene is C2, and the comonomer is C8, where C8 is regularly arranged on the C2 polymer main chain; The melt index of the ethylene propylene diene monomer rubber is measured to be 1-3 g / 10 min at 190 °C under a load of 2.16 kg, the Mooney viscosity is 20-40, and the density is 0.89-0.91 g / cm 3 .

2. The non-weakening polypropylene foam for airbag blasting according to claim 1, wherein: The viscosity of the crosslinking agent at room temperature is 40-70 mPa·s, the antioxidant is a hindered phenol antioxidant, the moisture content of the ADCA blowing agent is ≤1%, and the gas evolution is 140-160 mL / g.

3. A method for preparing the polypropylene foam according to claim 1 or 2, characterized in that, It includes the following steps: putting the raw materials into an extruder according to a set ratio, fully plasticizing and mixing them, and then extruding them into sheets through a die. During the process, the melt temperature is controlled to ensure that the blowing agent does not decompose in the extruder; irradiating the sheets to make the crosslinking agent fully react and crosslink; using a vertical foaming furnace for foaming production, where the horizontal section is used to preheat the sheets, and the vertical section is the foaming section. After foaming, it is cooled and shaped.

4. The preparation method according to claim 3, wherein: The melt temperature in the extruder is ≤180 °C; the irradiation is carried out by double-layer irradiation, and the dose is 30-40 kGy; the temperature of the preheating section is 200-240 °C, and the preheating time is 40-60 seconds; the temperature of the foaming section is 300-400 °C, and the heating time is 10-20 seconds.

5. The polypropylene foam as described in claim 1 or 2 is applied to the skin material in the airbag area of automotive interior, and is characterized in that: It is used to ensure that when the airbag bursts and unfolds, the skin material tears regularly according to the shape of the airbag box.

6. A laminated skin material, characterized in that: It includes a polypropylene foam layer and a TPO skin layer attached to a substrate, where the polypropylene foam layer uses the polypropylene foam described in claim 1 or 2 and is located between the substrate and the TPO skin layer.

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