JP6760155B2 - Foamed polypropylene resin composition and molded article - Google Patents

Description

The present invention relates to a foamed polypropylene resin composition and a molded product using the same.

In vehicles such as automobiles, the proportion of thermoplastic resin foam molded products is increasing from the viewpoint of weight reduction. The conventional foam molded product of a resin composition containing a filler is supplemented by increasing the amount of talc for rigidity and increasing the amount of rubber component for impact resistance in order to achieve both rigidity and impact resistance. (Patent Document 1). However, rigidity and impact resistance are physical properties that contradict each other, and if the foaming ratio is increased, it becomes difficult to uniformly control the foam cell structure. Therefore, both rigidity and impact resistance of the foamed molded product should be achieved. Was difficult.

Patent Document 2 describes a resin composition obtained by blending a polypropylene resin with a thermoplastic elastomer and talc as an inorganic filler and adding a foaming agent, as shown in Table 1 below.

Patent Document 2 describes that the 50% particle size (D50) of talc is preferably 0.01 to 50 μm, and 1.8 μm or 2.7 μm is used in Examples. Regarding the surface treatment of talc, there is a description that it may be left untreated or may be treated to improve dispersibility, but in the examples, untreated talc is used. According to the study by the present inventors, fine talc having a 50% particle diameter of 3 μm or less is difficult to disperse during kneading and aggregates when added in a large amount, so that it is not always effective as a foam nuclei and has a continuous foam structure. It is difficult to achieve both rigidity and impact resistance.
Further, the organic peroxide is disclosed only up to 0.030 parts by mass in the examples, and there is room for improvement in the uniformity of the foam cell and the balance of impact resistance and rigidity.
In addition, there is no specific description about rigidity and impact resistance.

Next, the polypropylene resin foam molded product is used more and more as described above, but its application to material design parts is extremely small. The reason is that the scratch resistance of the conventional polypropylene resin composition is insufficient, and it is conspicuous when scratched. In order to impart scratch resistance, there is an example in which a fatty acid amide such as erucic acid amide or silicone is added as a surface modifier to a resin composition containing talc to reduce the surface resistance (Patent Document 3). However, even if fatty acid amide is added to the resin composition containing unsurface-treated talc, sufficient scratch resistance may not be obtained in some cases. When the reason was examined by the present inventor, it was considered that the fatty acid amide was absorbed by the unsurface-treated talc in the initial stage after molding, and the transfer to the surface of the molded product was insufficient. In addition, the addition of fatty acid amide alone may cause problems such as deterioration of appearance quality and stickiness over time. When the reason was examined by the present inventor, it was considered that the fatty acid amide continued to migrate to the surface of the molded product and was deposited over time.

Japanese Unexamined Patent Publication No. 8-20690 Japanese Unexamined Patent Publication No. 2009-132893 Japanese Unexamined Patent Publication No. 2016-12128

Therefore, an object of the present invention is to obtain a foamed resin molded product having a high level of rigidity and impact resistance. A further object of the present invention is to maintain the scratch resistance of the foamed resin molded product for a long period of time, and to prevent deterioration of appearance quality and stickiness.

The foamed polypropylene resin composition of the present invention contains 10 to 65 parts by mass of an ethylene-α olefin copolymer as a rubber or a styrene-based elastomer as a thermoplastic elastomer with respect to 100 parts by mass of a polypropylene resin, and a surface treatment for enhancing dispersibility. Contains 18 to 90 parts by mass of talc having a 50% particle size (D50) of 1 to 3 μm, 0.1 to 6.0 parts by mass of an organic crystal nucleating agent, and 5 to 15 parts by mass of a foaming agent. It is characterized in that it was formulated in such a manner.

Here, as the surface-treated talc that enhances dispersibility, talc having siloxane added to the surface is preferable.

The expanded polypropylene resin composition of the present invention is preferably blended so as to further contain a higher fatty acid amide and a compatibilizer.

The foamed polypropylene resin molded product of the present invention is a foamed polypropylene molded product foam-molded by the foamed polypropylene resin composition, the foamed state is mainly closed cells, and the average foamed cell conforms to ASTM D3576-77. It is characterized by having a diameter of 100 to 300 μm.

The crystallinity χc of the interfoamed cell resin portion of the core layer of the foamed molded product is 30.0% or more, and the ratio of the crystallinity χc of the interfoamed cell resin portion to the crystallinity χs of the skin layer resin portion. It is preferable that χc / χs is 1.05 or more.

It is preferable that the flexural rigidity of the foam molded product in accordance with ISO178 is 2.0 × ^10-6 Nm or more, and the puncture energy in accordance with ISO 6603-2 is 4J or more.

The expanded polypropylene resin composition contains a higher fatty acid amide and a compatibilizer, has a limit normal force of scratch characteristics according to ISO 19252 of the expanded molded product of 6.0 N or more, and has a heat resistance test of 110 ° C. for 600 hours. It is preferable that the color difference change according to ISO11664-4 before and after is 3.0 or less.

<Action>
Foam moldings of thermoplastic resins such as polypropylene generally have lower rigidity and impact resistance than solid moldings when foamed. One of the causes is that the higher the foaming, the more difficult it is to control the foamed cell structure uniformly, and the more the foaming becomes, the more the structure becomes an open cell (continuous bubble) structure. As a means for improving this problem, there is a method of adding talc, which is an inorganic filler, as a foaming nucleating agent, and it is known that the smaller the particle size, the higher the foaming nucleating effect. However, since it is fine particles, it has poor dispersibility and easily aggregates, so that it may not be effective as a nucleating agent. As a means for solving these problems, by using talc having a particle diameter of 1 to 3 μm that has been surface-treated (siloxane surface treatment, etc.) to enhance dispersibility, the bulk specific gravity is large and handling is easy, and the resin by kneading The dispersion in the inside is also good, and it functions effectively as a foam nucleating agent, and the foam cells can be made uniform. As a result, the foamed state can be mainly made into closed cells, the average foamed cell diameter can be made 100 to 300 μm, and the rigidity and impact resistance of the foamed molded product can be improved.

Further, by adding an organic crystal nucleating agent, the crystallinity of the interfoamed cell resin of the foamed molded product is increased, and the rigidity of the foamed molded product is improved. In the inorganic filler-based crystal nucleating agent, as a reciprocity, there is a decrease in impact resistance due to propagation of resin / filler interface fracture.

In normal molding (non-foaming), the molding die takes heat from the skin layer resin portion, so that the crystallinity χs of the skin layer resin portion is lower than the crystallinity χc of the core layer resin portion, and the resin portion between the foamed cells Crystallinity ratio of skin layer χc / χs <hereinafter referred to as "crystallinity index". ) Exceeds 1.
On the other hand, in the case of foam molding, heat is taken from the resin by the generation and expansion of bubbles, so that the resin part between the foam cells of the core layer is in a rapidly cooled state as compared with the resin part of the core layer of the core layer, and the resin between the foam cells of the core layer The crystallinity χc of the portion remains at the same level as the crystallinity χs of the skin layer resin portion.
In the foamed resin composition of the present invention, due to the effect of the organic crystal nucleating agent, the crystallinity χc of the interfoamed cell resin portion of the core layer is higher than that of the skin layer resin portion χs, and the crystallinity index is χc /. χs ≧ 1.05 can be set, and χc ≧ 30.0% can be set. Further, since the organic crystal nucleating agent is once completely dissolved in the resin, the influence of the propagation of the resin / filler interface fracture is reduced, and the impact resistance is improved.

Further, by adding the higher fatty acid amide and the compatibilizer, the surface frictional resistance of the foamed molded product is reduced and the scratch resistance is improved. As described above, when unsurface-treated talc is blended, the higher fatty acid amide may be absorbed by the talc, the transfer to the surface of the molded product may be insufficient, and the scratch resistance may not be exhibited. The surface-treated talc is blended in the present invention, and since the surface treatment suppresses the absorption of the higher fatty acid amide by the talc, the transfer of the higher fatty acid amide to the surface of the molded product is not hindered. In addition, by adding the higher fatty acid amide and the compatibilizer together, the compatibilizer acts to suppress the transfer of the higher fatty acid amide to the surface of the molded product, and the transfer of the higher fatty acid amide to the surface over time. Accumulation can be suppressed. As a result, scratch resistance can be maintained for a long period of time, and deterioration of appearance quality and stickiness can be prevented.

According to the present invention, the combination of the above actions produces an excellent effect that a foamed resin molded product having a high-dimensional balance of rigidity and impact resistance can be obtained. Further, due to the action of the above-mentioned higher fatty acid amide and the compatibilizer, the scratch resistance of the foamed resin molded product can be maintained for a long period of time, and deterioration of appearance quality and stickiness can be prevented.

It is a schematic partial enlarged sectional view of the foamed resin molded article of an Example.

1. 1. Polypropylene resin The polypropylene resin is not particularly limited, but a polypropylene resin having a melt flow rate (MFR) of 5 to 150 g / 10 minutes at 230 ° C. and 21.2 N measured in accordance with ISO1133 is preferable, and more preferably 15 to 15 to 10. 120 g / 10 minutes. This is because the fluidity of the composition becomes appropriate.

2. 2. As the rubber or thermoplastic elastomer rubber, an ethylene-α-olefin copolymer is used . Examples of the ethylene-α-olefin copolymer include an ethylene-propylene copolymer (EPM), an ethylene-butene copolymer (EBM), an ethylene-octene copolymer (EOM), and an ethylene-propylene-non-conjugated diene copolymer. (EPDM) and the like can be exemplified.
As the thermoplastic elastomer, a styrene-based elastomer is used .

3. 3. The surface-treated talc that enhances talc dispersibility was surface-treated with a silane coupling agent, a titanium coupling agent, a higher fatty acid, a higher fatty acid ester, a higher fatty acid amide, a higher fatty acid salt, or another surfactant. An example of talc can be given. Of these, talc in which siloxane is added to the surface by a silane coupling agent is preferable.
The blending amount of talc is preferably 20 parts by mass or more.
Further, the expanded polypropylene resin composition may contain an inorganic filler other than talc in addition to talc. Examples of the inorganic filler include granular fillers such as calcium carbonate, barium sulfate and glass beads, and plate-shaped fillers such as kaolin, glass flakes, layered silicate and mica.

4. Organic crystal nucleating agent The organic crystal nucleating agent is not particularly limited, and examples thereof include sorbitol-based, amide-based, and benzoic acid metal salts.

5. Foaming agent The foaming agent is not particularly limited, and examples thereof include a physical foaming agent and a chemical foaming agent. Of these, chemical foaming agents are preferred. Examples of the chemical foaming agent include an organic chemical foaming agent and an inorganic chemical foaming agent. Examples of the inorganic chemical foaming agent include baking soda (sodium hydrogen carbonate), nitrite and hydride.
As the foaming agent, it is preferable to mix 5 to 15 parts by mass with a gas generating amount of 150 to 250 ml / 5 g.

6. Higher fatty acid amide The higher fatty acid amide is not particularly limited, and examples thereof include erucic acid amide, stearic acid amide, oleic acid amide, and ethylene bisstearic acid amide. Of these, erucic acid amide is preferable.

7. Compatibility agent The compatibility agent is not particularly limited, but a copolymer of ethylene and at least one vinyl monomer having inferior affinity with higher fatty acid amide is preferable, and specifically, ethylene / acrylic acid Copolymer, ethylene / methyl acrylate copolymer, ethylene / methyl methacrylate copolymer, ethylene / ethyl acrylate copolymer, ethylene / isobutyl acrylate copolymer, n-butyl copolymer of ethylene / acrylate , Ethylene / 2-ethylhexyl acrylate copolymer, ethylene / ethyl acrylate / maleic anhydride copolymer, ethylene / ethyl acrylate / glycidyl methacrylate copolymer, ethylene / glycidyl methacrylate copolymer, ethylene / acetic acid Examples thereof include a vinyl / glycidyl methacrylate copolymer, an ethylene / vinyl acetate copolymer, and a saponified product thereof. These may be used alone or in combination of two or more.
The compounding mass ratio of the higher fatty acid amide and the compatibilizer is not particularly limited, but is preferably 1: 10 to 2: 1, more preferably 1: 3 to 2: 1.
The total amount of the higher fatty acid amide and the compatibilizer in the above compounding mass ratio with respect to 100 parts by mass of the polypropylene resin is not particularly limited, but is preferably 0.8 to 15.0 parts by mass, and 1.0 to 9. 5 parts by mass is more preferable.

6. Foam molding The use of foam molding is not particularly limited, but is limited to automobile exterior parts such as grills, bumpers, and cowl louvers, and automobile interior parts such as instrument panels, consoles, trims, pillars, center clusters, and deck side trims. Etc. can be exemplified.

The foamed polypropylene resin compositions of Samples 1 to 17 having the formulations shown in Table 2 below (the blending values are parts by mass) were prepared, and the expanded polypropylene resin molded product was molded. Samples 1 to 10 are examples, and samples 11 to 17 are comparative examples.

Here, the details of each material used are as follows. Here, "rubber" collectively refers to rubber or thermoplastic elastomer.
PP-1: The product name is "BX3920" manufactured by SK, and it is a polypropylene resin having an MFR of 100 g / 10 minutes.
PP-2: The product name is "BH975MO" manufactured by Bruges, and it is a polypropylene resin having an MFR of 38 g / 10 minutes.
Rubber-1: The trade name of Dow Elastomer Co., Ltd. is "Engage 8842", which is an ethylene-α-olefin copolymer.
Rubber-2: The trade name of Mitsui Chemicals, Inc. is "Toughmer DF610", which is an ethylene-α-olefin copolymer.
Rubber-3: The trade name of Kuraray Co., Ltd. is "Septon 2063", which is a styrene-based elastomer.

Talc-1: A talc having a trade name of "NANO ACE D-1000" manufactured by Nippon Tarku Co., Ltd., which is surface-treated with siloxane and has a 50% particle diameter (D50) of 1 μm. The 50% particle size is based on ISO 1330-1 and measured by a laser diffraction type particle size distribution measuring device (the same applies herein).
Talc-2: A talc having a particle size of 2 μm and surface-treated with siloxane under the trade name “NSultraC” of IMI FABI.
Talc-3: The trade name "HTPultra5L" of IMI FABI, which is a talc having a particle size of 2 μm and not surface-treated.
Talc-4: The trade name "GH7" of Hayashi Kasei Co., Ltd., which is a talc having a particle size of 6 μm and not surface-treated.

Organic crystal nucleating agent-1: The trade name is "Gelol MD" of New Japan Chemical Co., Ltd., and it is 1,3: 2,4-bis-O- (4-methylbenzylidene) -D-sorbitol.
Organic crystal nucleating agent-2: The trade name of New Japan Chemical Co., Ltd. is "Ricaclear PC1", which is an amide-based crystal nucleating agent.
Foaming agent MB-1: The trade name of Eiwa Kasei Co., Ltd. is "Polyslen EE25C". This is a baking soda master batch.
Foaming agent MB-2: The trade name of Eiwa Kasei Co., Ltd. is "Polyslen EE65C". This is a baking soda master batch.

The expanded polypropylene resin composition of Samples 1 to 17 is injected into a flat cavity having a gap of 1.5 mm in a molding mold (not shown), and then the movable mold of the molding mold is cored back to increase the gap between the cavities. The composition was foamed to form a plate-shaped foamed polypropylene resin molded product having a thickness of 2.8 mm. That is, the foaming ratio is 1.87 times. As shown in FIG. 1, the molded polypropylene resin molded body 1 has a core layer composed of a foam cell 2 and a resin portion 3 between foam cells, and a skin layer resin having almost no foam cells on the surface portion in contact with the molding die. It is composed of part 4 (the broken line in FIG. 1 is a distinguishing line from the core layer). From this plate-shaped molded body 1, a plate-shaped test piece having a predetermined size according to the measurement was cut out, and the physical property data was measured as follows.

(A) Flexural rigidity In accordance with ISO178 (JIS K7171), a test piece of 10 mm x 80 mm x 2.8 mm thickness is subjected to a three-point bending test to measure the flexural modulus, and the flexural modulus is multiplied by the moment of inertia of area. The bending rigidity was calculated.
Then, a flexural rigidity of 2.0 × ^10-6 Nm or more was judged to be “good”.

(B) High-speed surface impact test method In accordance with ISO 6603-2 (JIS K7211-2), a test piece of 120 mm x 130 mm x 2.8 mm thickness is subjected to a test temperature of -30 ° C by an instrumentation impact tester. High-speed and constant-velocity impact (striker shape: φ12.7 mm spherical, support inner diameter: φ76.2 mm, impact speed: 5 m / sec), the generated force and deformation amount are captured as the impact waveform, and the maximum impact force The impact energy (puncture energy) required to reach the puncture displacement where was reduced by half was measured.
Then, when the impact energy was 4J or more, it was judged as "good".

(C) How to determine the degree of crystallinity Measure each of the foamed cell-to-cell resin portion 3 and the skin layer resin portion 4 by the following method using a differential scanning calorimeter (DSC) (Q200 manufactured by TA Instruments). did.
The temperature was raised from 0 ° C. to 250 ° C. at a heating rate of 40 ° C./min, and the amount of heat of fusion was determined. From the obtained heat of fusion ΔH (J / g), from the formula (ΔH / resin fraction / 209) × 100 (%), the crystallinity (crystallinity χc of the interfoamed cell resin portion 3 and the skin layer resin) The crystallinity χs) of Part 4 was determined.
Here, the resin fraction is the remaining polymer fraction (0.8 if the filler is 20%) obtained by subtracting the weight fraction of the inorganic component (filler or the like) in the material. 209 is the amount of heat of fusion (J / g) at the time of 100% crystallization of the polypropylene resin.
Then, when the crystallinity χc of the resin portion 3 between the foamed cells was 30.0% or more, it was judged as “good”.
Further, when the crystallization index χc / χs was 1.05 or more, it was judged as “good”.

(D) Average foam cell diameter The average foam cell diameter was determined in accordance with ASTM D3576-77. First, the cross section of the test piece cut out from the molded body 1 was photographed with a stereomicroscope at a magnification of 50 times (the entire thickness direction can be photographed). Draw a straight line (shown by a two-point chain line in FIG. 1) in the horizontal and vertical directions on this photograph, measure the length of all the strings of the foam cell that the straight line crosses, and obtain the average value t of the lengths of the strings. It was. The average foam cell diameter d was calculated from the formula d = t / 0.616.
Then, an average foam cell diameter of 100 to 300 μm was evaluated as “good”.
In addition, regarding the foaming state, those that were mainly closed cells (single bubbles) were evaluated as "good".

Table 2 shows each of the above physical property data. In the molded products of Samples 1 to 10 (Example), all the physical property data were judged to be good, and the rigidity and the impact resistance were well balanced in a high dimension. On the other hand, the molded products of Samples 11 to 17 (Comparative Example) lack one or both of rigidity and impact resistance.

Next, the expanded polypropylene resin compositions of Samples 18 to 34 having the formulations shown in Table 3 below (the compounding values are parts by mass) further containing the scratch resistance improving agent were prepared, and the expanded polypropylene resin molded product was molded. .. Table 3 reprints Sample 1 with additional physical property data described below. Samples 18 to 23 are based on the formulation of sample 1 and contain a scratch resistance improving agent, and samples 24 to 32 are based on the formulation of samples 2 to 10 and contain a scratch resistance improving agent. Is.

Here, the details of the scratch resistance improving agent used are as follows, and the details of each of the other materials are as described above.
Scratch resistance improver-1: NOF Corporation's trade name "Nofalloy KA832", which is a higher fatty acid amide (presumed to be erucic acid amide) and a compatibilizer (ethylene and at least one vinyl monomer). It is presumed to be a copolymer of.). The compounding mass ratio of the higher fatty acid amide to the compatibilizer is estimated to be 2: 3.
Scratch resistance improver-2: Kao Corporation's trade name "fatty acid amide E", which is an erucic acid amide.
Scratch resistance improver-3: Kao Corporation's trade name "Kaowax EB-G", which is an ethylene / bisstearic acid amide.

A plate-shaped molded product 1 having a thickness of 2.8 mm was molded from the expanded polypropylene resin compositions of Samples 18 to 34 in the same manner as in Samples 1 to 17. From this plate-shaped molded body 1, a plate-shaped test piece having a predetermined size according to the measurement is cut out, physical property data similar to those of samples 1 to 17 are measured, and as additional physical property data, scratch resistance and heat resistance test are performed. The subsequent stickiness and change in color difference were measured as follows. Additional physical property data was also measured for Sample 1.

(E) Scratch resistance (scratch characteristics)
According to ISO19252 (JIS K7316), the surface of the test piece was scratch-tested (chip size: φ10 μm (stainless steel ball), scratch speed: 100 mm / sec, scratch distance: 100 mm), and the limit normal force was determined. A limit normal force of 6.0 N or more was judged to be "good".

(F) Stickiness after the heat resistance test The test piece was placed in a heating tank and subjected to a heat resistance test at 110 ° C. for 600 hours, and the surface of the test piece after the heat resistance test was touched with a finger for sensory evaluation. Those that were not sticky were evaluated as "good".

(G) Color difference change before and after the heat resistance test The color difference change on the surface of the test piece before and after the heat resistance test was measured according to ISO11664-4 (JIS Z8781-4). A color difference change of 3.0 or less was evaluated as "good".

Table 3 shows each of the above physical property data. The molded bodies of Samples 18 to 32 were judged to have good physical property data of flexural rigidity, high-speed surface impact, crystallinity, and average foam cell diameter, and the rigidity and impact resistance were balanced at a high level. This is an example. However, there is room for improvement in Samples 1 and 18 in that they lack scratch resistance. Further, the samples 22 and 23 are sticky after the heat resistance test and there is a lot of color difference change, so there is room for improvement. Samples 19 to 21, 24 to 32 are preferable examples because they are judged to have good scratch resistance, stickiness after the heat resistance test, and color difference change.

On the other hand, the molded products of the samples 33 and 34 lack one or both of rigidity and impact resistance, which is a comparative example. Further, despite the addition of the higher fatty acid amide and the compatibilizer, the scratch resistance was insufficient, which is considered to be because the unsurface-treated talc absorbed the higher fatty acid amide.

The present invention is not limited to the above-described embodiment, and can be appropriately modified and embodied without departing from the spirit of the invention.

1 Foamed polypropylene resin molded body 2 Foamed cell 3 Foamed cell inter-foamed resin part 4 Skin layer resin part

Claims (7)

With respect to 100 parts by mass of polypropylene resin, 10 to 65 parts by mass of an ethylene-α olefin copolymer as rubber or a styrene-based elastomer as a thermoplastic elastomer and a 50% particle diameter (D50) of 1 to 3 μm are dispersible. It is characterized in that it is blended so as to contain 18 to 90 parts by mass of a surface-treated talc, 0.1 to 6.0 parts by mass of an organic crystal nucleating agent, and 5 to 15 parts by mass of a foaming agent. Foamed polypropylene resin composition. The expanded polypropylene resin composition according to claim 1, wherein the surface-treated talc that enhances dispersibility is a talc in which siloxane is added to the surface. The expanded polypropylene resin composition according to claim 1 or 2, further comprising a higher fatty acid amide and a compatibilizer. A foamed molded product (1) foam-molded by the expanded polypropylene resin composition according to claim 1, 2 or 3, wherein the foamed state is mainly closed cells and an average foam cell conforming to ASTM D3576-77. A foamed polypropylene resin molded product having a diameter of 100 to 300 μm. The crystallinity (χc) of the interfoam resin portion (3) of the core layer of the foamed molded product (1) is 30.0% or more, and the crystallinity (χc) of the interfoam resin portion (3) is 30.0% or more. The foamed polypropylene resin molded product according to claim 4, wherein the ratio (χc / χs) of the skin layer resin portion (4) to the crystallinity (χs) of) is 1.05 or more. The foam according to claim 4 or 5, wherein the foamed molded product (1) has a bending rigidity of 2.0 × ^10-6 Nm or more according to ISO178 and a puncture energy of 4J or more according to ISO 6603-2. Polypropylene resin molded body. The expanded polypropylene resin composition contains a higher fatty acid amide and a compatibilizer, has a limit normal force of scratch characteristics according to ISO19252 of the foamed molded product of 6.0 N or more, and has a heat resistance test of 110 ° C. × 600 hours. The foamed polypropylene resin molded product according to claim 4, 5 or 6, wherein the color difference change according to ISO11664-4 before and after is 3.0 or less.

Images