JP2021161197A - Polypropylene resin composition for injection foam molding, and injection foam polypropylene resin composition molding using the same - Google Patents

Abstract

To provide a polypropylene resin composition for injection foam molding which enables production of a foam molding that has a comparatively high expansion ratio and is excellent in stability and appearance of a cell shape, and an injection foam polypropylene resin composition using the same.SOLUTION: There are provided a polypropylene resin composition for injection foam molding which contains 30-96 pts.mass of impact polypropylene (A) having MFR of 30-200 g/10 min and intrinsic viscosity [η] of a propylene homopolymer polymer part of 0.8-3.0 dl/g, 1-10 pts.mass of homopolypropylene (B) having intrinsic viscosity [η] of 6-10dl/g, 3-29 pts.mass of homopolypropylene (C) having an MFR of 200-1,000 g/10 min, 0-30 pts.mass of an α-olefin elastomer (D), and 0-30 pts.mass of an inorganic filler (E) (total amount of components (A) to (E) is 100 pts.mass); and an injection foam polypropylene resin composition molding using the same.SELECTED DRAWING: None

Description

The present invention relates to an injection-foamed polypropylene resin composition suitable for producing an injection-foamed molded article, and an injection-foamed polypropylene resin composition molded article suitable for use in automobile interior / exterior parts using the same.

Since polypropylene resin is excellent in moldability, physical characteristic balance, recycling characteristics and cost performance, it is widely used in various fields such as daily necessities, housing fields, home appliances fields, and automobile parts.

In recent years, there has been a strong demand for weight reduction of automobile parts, and in particular, the use of foam molded products for interior parts is increasing. However, automobile interior and exterior parts are required to be further reduced in weight and improved in mechanical properties. Therefore, an injection-foamed molded article having a higher foaming ratio and excellent mechanical properties has been proposed.

Patent Document 1 describes an impact polypropylene containing a high molecular weight component, a rubber component, and an inorganic filler. The impact polypropylene containing a high molecular weight component has a temperature of 135 ° C., and the ultimate viscosity [η] in tetralin is 13.5 to 20. A polypropylene resin composition for foam molding containing 0 dl / g of a propylene polymer component is disclosed. It is explained that this resin composition is suitable for injection foam molding, has an excellent balance between fluidity and melt tension, and can achieve high-magnification foam molding.

Patent Document 2 discloses a linear polypropylene-based resin composition containing a linear propylene / ethylene block copolymer, a polypropylene-based resin composed of a propylene-based polymer, and a foaming agent. It is explained that this resin composition is excellent in physical properties such as surface appearance, injection foam moldability and rigidity, and can be significantly reduced in weight.

International Publication No. 2010/050509 Japanese Unexamined Patent Publication No. 2010-144133

For the purpose of reducing the weight of the foam molded product, for example, in core back injection foam molding, the initial thickness of the resin material before foaming is preferably thin, and the foaming ratio is preferably high. However, when foam molding is performed at a high foaming ratio, the cell shape may deteriorate, or the appearance may be poor due to sink marks, avatars, and the like.

Focusing on the above problems, the present inventors have considered to further improve the foaming ratio, the stability of the cell shape, and the appearance. That is, an object of the present invention is an injection-foamed polypropylene resin composition capable of producing a foamed molded product having a relatively high foaming ratio and excellent cell shape stability and appearance, and an injection-foamed polypropylene resin composition using the same. The purpose is to provide a molded product.

As a result of diligent studies to solve the above problems, the present inventor has found that a composition composed of specific components is very effective, and has completed the present invention. That is, the gist of the present invention is as follows.

[1] The melt flow rate (MFR) measured by ASTM D-1238 at 230 ° C. and a load of 2.16 kg is 30 to 200 g / 10 min, and propylene alone is specified as an n-decane insoluble portion (Dinsol) at 23 ° C. 30 to 96 parts by mass of impact polypropylene (A) having an intrinsic viscosity [η] of the polymer part in tetralin at 135 ° C. of 0.8 to 3.0 dl / g,
1 to 10 parts by mass of homopolypropylene (B) having an intrinsic viscosity [η] of 6 to 10 dl / g in tetralin at 135 ° C.
Homopolypropylene (C) 3 to 29 parts by mass α-olefin elastomer (D) 0 to 30 parts by mass having a melt flow rate (MFR) of 200 to 1000 g / 10 min measured by ASTM D-1238 at 230 ° C. and a load of 2.16 kg. Parts and 0 to 30 parts by mass of the inorganic filler (E) [100 parts by mass of the total amount of the components (A) to (E)]
A polypropylene resin composition for injection foam molding comprising.

[2] The ultimate viscosity [η] of the propylene / ethylene copolymer portion of impact polypropylene (A) specified as the n-decane soluble portion (Dsol) at 23 ° C. in tetralin at 135 ° C. is 1.0 to 0. The polypropylene resin composition for injection foam molding according to [1], which is 10 dl / g.

[3] The content of the propylene homopolymer portion specified as the n-decane insoluble portion (Dinsol) at 23 ° C. in the impact polypropylene (A) is 70 to 97% by mass, and the n-decane soluble portion at 23 ° C. is soluble. The polypropylene resin composition for injection foam molding according to [1] or [2], wherein the content of the propylene / ethylene copolymer portion specified as the part (Dsol) is 3 to 30% by mass.

[4] The polypropylene resin composition for injection foam molding according to any one of [1] to [3], wherein the α-olefin elastomer (D) is an ethylene-based elastomer.

[5] The polypropylene resin composition for injection foam molding according to any one of [1] to [4], wherein the inorganic filler (E) is talc.

[6] Foaming, which is an inorganic or organic chemical foaming agent, with respect to the resin composition [total amount of components (A) to (E) 100 parts by mass] according to any one of [1] to [5]. An injection-foamed polypropylene resin composition molded product obtained by injection-foaming molding by adding 0.1 to 10 parts by mass of the agent (F).

[7] The injection-foamed polypropylene resin composition molded product according to [6], wherein the initial charged wall thickness before foaming is 1.0 to 2.0 mm, and the foaming ratio is 1.5 times or more.

According to the present invention, a polypropylene resin composition for injection foam molding capable of producing a foam molded product having excellent cell shape stability and appearance at a relatively high foaming ratio, and injection foamed polypropylene resin composition molding using the same. Can provide the body.

In the present invention, with respect to the impact polypropylene (A) of a specific MFR, the homopolypropylene (B) having a specific extreme viscosity [η] (that is, a sufficiently high molecular weight within a range that does not gel) and the specific MFR have a high flow rate. By adding the sex homopolypropylene (C) together in a specific ratio, good foamability and excellent appearance can be achieved in a well-balanced manner.

In particular, according to the present invention, as described in Examples described later, even when the plate thickness before foaming is thin and the foaming ratio is increased, the average cell diameter of bubbles is 200 μm or less, and the cell diameters are small and uniform. In addition, it is possible to obtain a foam molded product in which the occurrence of appearance defects due to sink marks, avatars, etc. is suppressed.

The reason why the above effects are obtained is not always clear, but regarding the cell shape, for example, by adding an appropriate amount of homopolypropylene (B), the melt tension of the resin composition is kept high, and as a result, the cell The shape is considered to be stable.

Regarding the suppression of sink marks, for example, by adding an appropriate amount of homopolypropylene (B), foaming is not excessively suppressed and foam breakage is suppressed, and it exists between the resin and the mold and causes sink marks. By adding an appropriate amount of homopolypropylene (C), high fluidity is maintained, the viscosity of the entire molded product is kept low, and the internal pressure during foaming is effectively utilized. As a result, it is considered that the occurrence of sink marks is suppressed.

Regarding the suppression of avatar generation, for example, by adding an appropriate amount of homopolypropylene (B), foam rupture is suppressed, and the generation of gas existing between the resin and the mold and causing sink marks is suppressed. As a result, the occurrence of avatars is considered to be suppressed.

Therefore, according to the present invention, for example, in core back injection foam molding, the initial thickness of the resin material before foaming can be made thin, and it can be satisfactorily molded with a high foaming ratio, which makes it extremely possible to reduce the weight of the foamed molded product. It is advantageous to.

<Impact polypropylene (A)>
The impact polypropylene (A) used in the present invention has a melt flow rate (MFR) of 30 to 200 g / 10 min measured by ASTM D-1238 at 230 ° C. and a load of 2.16 kg, and is an n-decane insoluble portion at 23 ° C. Dinsol) is an impact polypropylene having an intrinsic viscosity [η] of 0.8 to 3.0 dl / g in tetralin at 135 ° C. of the propylene homopolymer part.

Impact polypropylene (A) contains a propylene homopolymer portion identified as an n-decane insoluble moiety (Dinsol) at 23 ° C. Further, preferably, a propylene / ethylene copolymer portion specified as an n-decane soluble portion (Dsol) at 23 ° C. is also included. The content of the propylene homopolymer portion specified as the n-decane insoluble portion (Dinsol) is preferably 70 to 97% by mass, more preferably 73 to 95% by mass. The content of the propylene / ethylene copolymer portion specified as the n-decane soluble portion (Dsol) is preferably 3 to 30% by mass, more preferably 5 to 27% by mass.

The intrinsic viscosity [η] of the propylene homopolymer portion specified as the n-decane insoluble portion (Dinsol) at 23 ° C. is 0.8 to 3.0 dl / g, preferably 0.8 to 2.0 dl / g. Is.

The ultimate viscosity [η] of the propylene / ethylene copolymer portion specified as the n-decane soluble portion (Dsol) at 23 ° C. is preferably 1.0 to 10 dl / g, more preferably 3.0 to 8. It is 0 dl / g, particularly preferably 5.0 to 7.5. The ethylene content in the propylene / ethylene copolymer is preferably 20 to 50% by mass, more preferably 25 to 40% by mass.

The MFR of impact polypropylene (A) is 30 to 200 g / 10 min, preferably 30 to 150 g / 10 min.

The propylene homopolymer portion contained in the n-decane insoluble portion (Dinsol) at 23 ° C. in the impact polypropylene (A) preferably has excellent stereoregularity. For example, the isotactic pentad fraction (mmmm fraction). ) Is preferably 95.0% or more, more preferably 97.0% or more. When the propylene homopolymer portion has such a high isotactic pentad fraction, it is possible to produce a foam molded product having high crystallinity of the resin and high rigidity. The isotactic pentad fraction (mmmm fraction) is ^{a value measured using 13} C-NMR, and indicates the abundance ratio of the isotactic chain in the polypropylene molecular chain in pentad units. , It is a fraction of the propylene monomer unit at the center of the chain in which five propylene monomer units are continuously mesobonded. Specifically, it is a value calculated as a fraction of the mmmm peak in the total absorption peak of the methyl carbon region observed in the ^{13 C-NMR spectrum.}

The impact polypropylene (A) may contain the branched olefin polymer in a proportion of preferably 0.1% by mass or less, more preferably 0.05% by mass or less. Since the branched olefin polymer acts as a nucleating agent for impact polypropylene (A), the isotactic pentad fraction of the propylene homopolymer portion can be increased and the moldability can be improved. Examples of such branched olefin polymers include 3-methyl-1-butene, 3,3-dimethyl-1-butene, 3-methyl-1-pentene, 4-methyl-1-pentene, and 3-methyl-1. -A homopolymer of a branched olefin such as pentene or a copolymer containing the same can be used. Of these, 3-methyl-1-butene is preferred.

The impact polypropylene (A) may be used alone or in combination of two or more. When two or more kinds are used, it is preferable that the total of the impact polypropylene (A) satisfies each of the above ranges.

<Homopolypropylene (B)>
The homopolypropylene (B) used in the present invention is a homopolypropylene having an ultimate viscosity [η] of 6 to 10 dl / g in tetralin at 135 ° C.

The melt flow rate (MFR) measured by ASTM D-1238 of homopolypropylene (B) at 230 ° C. and a load of 2.16 kg is preferably 1-5 g / 10 min, more preferably 2-5 g / 10 min.

The ultimate viscosity [η] of homopolypropylene (B) in tetralin at 135 ° C. is 6 to 10 dl / g. If the ultimate viscosity [η] is less than 6 dl / g, the bubbles of the obtained foamed molded product may not be sufficiently finely divided. On the other hand, when the ultimate viscosity [η] exceeds 10 dl / g, the cell diameter of the bubbles in the obtained foamed molded product becomes too small, and dents on the surface of the molded product due to poor foaming are likely to occur. This ultimate viscosity [η] is preferably 7 to 9 dl / g.

<Homopolypropylene (C)>
The homopolypropylene (C) used in the present invention is a homopolypropylene having a melt flow rate (MFR) of 200 to 1000 g / 10 min measured by ASTM D-1238 at 230 ° C. and a load of 2.16 kg.

The melt flow rate (MFR) measured by ASTM D-1238 of homopolypropylene (C) at 230 ° C. and a load of 2.16 kg is 200 to 1000 g / 10 min. If this MFR is less than 200 g / 10 min, short shots and foaming defects at the ends are likely to occur when the flow length of the resin during injection molding is long, and the surface layer of the foamed molded product becomes soft and dimples occur on the surface. In some cases. On the other hand, if this MFR exceeds 1000 g / 10 min, foaming defects such as gas release and bubble rupture may occur. This MFR is preferably 300 to 700 g / 10 min.

<Α-olefin elastomer (D)>
The α-olefin elastomer (D) used in the present invention is an elastomer composed mainly of α-olefin. The type is not particularly limited, but an ethylene-based elastomer is preferable, and a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms is preferable. Specific examples of α-olefins having 3 to 10 carbon atoms that copolymerize with ethylene include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, and 3-methyl-1-pentene. , 1-Heptene, 1-octene, 1-nonene, 1-decene. Two or more of these α-olefins may be used in combination. Of these, 1-butene and 1-octene are particularly preferable.

The melt flow rate (MFR) measured by ASTM D-1238 of the α-olefin elastomer (D) at 190 ° C. and a load of 2.16 kg is preferably 0.5 to 40 g / 10 min, more preferably 0.5 to 20 g /. It is 10 min, particularly preferably 0.5 to 10 g / 10 min.

The density of the α-olefin elastomer (D) is preferably 0.850.90 g / cm ³ , more preferably 0.85 to 0.88 g / cm ³ .

<Inorganic filler (E)>
The type of the inorganic filler (E) used in the present invention is not particularly limited, but for example, talc, heavy calcium carbonate, light calcium carbonate, glass fiber, magnesium carbonate, mica, kaolin, calcium sulfate, barium sulfate, titanium white, white. Calcium, carbon black, aluminum hydroxide, magnesium hydroxide can be used. Two or more kinds of inorganic fillers may be used in combination. Of these, talc is particularly preferred.

<Other ingredients>
The polypropylene resin composition for injection foam molding of the present invention may contain various additives as necessary, as long as the purpose is not impaired. Specific examples of additives include nucleating agents, antioxidants, hydrochloric acid absorbers, heat-resistant stabilizers, weather-resistant stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, flame retardants, pigments, dyes, and dispersants. , Copper damage inhibitors, neutralizers, plasticizers, cross-linking agents, flowability improvers (peroxides, etc.), weld strength improvers, natural oils, synthetic oils, waxes.

<Polypropylene resin composition for injection foam molding>
The polypropylene resin composition for injection foam molding of the present invention contains the impact polypropylene (A), homopolypoly (B) and homopolypropylene (C) described above, and if necessary, α-olefin elastomer (D) and an inorganic filler. It is a resin composition containing (E) and may further contain other components. The content of each component (A) to (E) is as follows, based on 100 parts by mass of the total amount of the components (A) to (E).

The content of impact polypropylene (A) is 30 to 96 parts by mass, preferably 30 to 50 parts by mass.

The content of homopolypropylene (B) is 1 to 10 parts by mass. If this content is less than 1 part by mass, the cells of the foamed molded product are likely to break, and dents and variations in physical properties are likely to occur due to poor foaming. On the other hand, if this content exceeds 10 parts by mass, streaky defects and avatars are likely to occur on the surface of the foamed molded product. This content is preferably 1 to 7 parts by mass.

The content of homopolypropylene (C) is 3 to 29 parts by mass. If this content is less than 3 parts by mass, short shots and foaming defects at the ends are likely to occur when the flow length of the resin during injection molding is long, and the surface layer of the foamed molded product becomes soft and dimples appear on the surface. May occur. On the other hand, if this content exceeds 29 parts by mass, foaming defects such as gas release and bubble rupture may occur. It is preferably 5 to 20 parts by mass.

The content of the α-olefin elastomer (D) is preferably 0 to 30 parts by mass, more preferably 1 to 30 parts by mass, particularly preferably 10 to 30 parts by mass, and most preferably 15 to 25 parts by mass.

The content of the inorganic filler (E) is more preferably 1 to 30 parts by mass, particularly preferably 10 to 30 parts by mass, and most preferably 15 to 25 parts by mass.

The polypropylene resin composition for injection foam molding of the present invention described above is a composition used for injection foam molding by adding a foaming agent.

<Injection foamed polypropylene resin composition molded body>
The injection-foamed polypropylene resin composition molded product of the present invention has 0.1 to 10 parts by mass of a foaming agent (F), which is an inorganic or organic chemical foaming agent, with respect to the above-described injection-foamed molding polypropylene resin composition. It is a molded product obtained by injection foam molding with the addition of.

The foaming agent (F) may be an inorganic or organic foaming agent, and the type thereof is not particularly limited. Specific examples of the inorganic foaming agent include sodium bicarbonate, sodium carbonate, ammonium bicarbonate, ammonium carbonate, and ammonium nitrite. Specific examples of the organic foaming agent include N-nitroso compounds such as N, N'-dinitrosoterephthalamide and N, N'-dinitrosopentamethylenetetramine: azodicarboxylicamide, azobisisobutyronitrile, azocyclohexyl. Azo compounds such as nitrile, azodiaminobenzene, barium azodicarboxylate: benzenesulfonylhydrazide, toluenesulfonylhydrazide, p, p'-oxybis (benzenesulfenylhydrazide), diphenylsulphon-3,3'-disulfonylhydrazide, etc. Sulfonyl hydrazide compounds; examples thereof include azide compounds such as calcium azide, 4,4'-diphenyldisulfonyl azide, and p-toluene sulfonyl azide. Two or more kinds of foaming agents (F) may be used in combination. Further, the foaming agent (F) may be mixed in advance with the resin composition, or may be injected from the middle of the cylinder at the time of injection molding.

The amount of the foaming agent added is usually 0.1 to 10 parts by weight, preferably 0.4 to 10 parts by weight with respect to the polypropylene resin composition for injection foam molding [total amount of components (A) to (E) 100 parts by mass]. It is 5.0 parts by weight, more preferably 0.7 to 3.0 parts by weight.

In the injection-foamed polypropylene resin composition molded product of the present invention, the initial charged wall thickness before foaming is preferably 1.0 to 2.0 mm, more preferably 1.0 to 1.8 mm. The foaming ratio is preferably 1.5 times or more, and more preferably 1.5 to 3.0 times. Here, the "initial charged wall thickness before foaming" means the thickness of the resin material before foaming to be charged into the injection mold. Further, the “foaming ratio” means a _{plate thickness ratio (t / t 0 ) of the plate thickness (t 0} ) before foaming and the plate thickness (t) after foaming, as described in Examples described later.

In injection foam molding, for example, a plasticized resin composition is injection-filled from an injection molding machine into a cavity of a mold, and then the volume of the cavity is increased to foam the plasticized resin composition to produce a foamed molded product. To do.

The molding die used for injection foam molding is composed of, for example, a fixed mold and a movable mold, and these are preferably in a mold-clamped state at the time of injection filling of the plasticized resin composition. Further, the volume of the cavity can be increased by retracting the movable mold (core back) to expand the cavity, and it is particularly preferable to increase the volume after an appropriate time after injection filling. The core moving speed at the time of core back may be appropriately determined depending on the thickness of the molded product, the type of resin, the type of foaming agent, the mold temperature, and the resin temperature.

The temperature of the resin to be injected and the mold temperature vary depending on the thickness of the molded product, the type of resin, the type and amount of foaming agent added, etc., but the temperature normally used for molding polypropylene-based resin is sufficient, and the product thickness is high. If you want to obtain a thin one or one with a high foaming ratio, it is better to set it higher than the normal mold temperature. Specifically, for example, the temperature of the resin to be injected is usually 170 to 250 ° C, preferably 180 to 220 ° C. The mold temperature of the fixed mold and the movable mold is usually 10 to 100 ° C, preferably 30 to 80 ° C. The pressure inside the mold is usually 5 to 50 MPa, preferably 10 to 30 MPa. The injection pressure is usually 10 to 250 MPa, preferably 12 to 200 MPa.

By filling the cavity with the resin composition at once and then foaming it, the resin in the part in contact with the mold solidifies faster than the resin inside, forming an unfoamed solid skin layer on the surface of the molded product, and the center. An injection foam molded product having a foam layer is obtained. Since the injection-foamed molded product has an unfoamed solid skin layer on the surface of the molded product, a hard product shape can be obtained and maintained, and a highly rigid molded product can be obtained. Further, even if there is some distribution in the cell shape, cell density, and foaming ratio of the foam layer inside the molded product, a molded product having a good appearance can be obtained due to the smoothness and rigidity of the skin layer. The thickness of this solid skin layer is not particularly limited, but is preferably 0.1 to 0.5 mm, more preferably 0.3 to 0.5 mm. The thickness of the central foam layer is preferably 2 to 4 mm, more preferably 1.8 to 3.5 mm.

The injection-foamed polypropylene resin composition molded product of the present invention can be suitably used for various purposes such as automobile interior / exterior parts, substitutes such as cardboard, electric appliances, building materials, etc., and in particular, automobile interior parts and automobile exteriors. Suitable for use as parts for parts.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. However, the present invention is not limited to these examples.

The composition and physical properties of each component used in Examples and Comparative Examples were measured by the following methods.

(1) Amount of n-decane soluble part and insoluble part at 23 ° C. Sample 3 g ( ^{measured to the unit of 10 -4} g) in a glass measuring container. This mass is referred to as b (g) in the following formula. (Represented), 500 ml of decane, and a small amount of a heat-resistant stabilizer soluble in decane were charged, and the temperature was raised to 150 ° C. in 2 hours while stirring with a stirrer in a nitrogen atmosphere to dissolve the propylene block copolymer. The mixture was kept at 150 ° C. for 2 hours and then slowly cooled to 23 ° C. over 8 hours. The obtained liquid containing the precipitate of the propylene-based block copolymer was filtered under reduced pressure with a 25G-4 standard glass filter manufactured by Iwata Glass Co., Ltd. 100 ml of the filtrate was collected and dried under reduced pressure to obtain a part of the decan-soluble component, and the mass ^{was measured to the unit of 10-4} g (this mass is defined as a (g) in the following formula. expressed). After this operation, the amount of decane-soluble component was determined by the following formula.
Room temperature n-decane soluble component (Dsol) content = 100 × (500 × a) / (100 × b)
Room temperature n-decane insoluble component (Dinsol) content = 100-100 × (500 × a) / (100 × b)

(2) Ethylene content of decane-soluble part at 23 ° C
¹³ Based on the measurement of C-NMR, it was measured, calculated and determined as follows. As the sample, the decane-soluble component obtained when the amount of the n-decane-soluble component was determined was used. Using this soluble component as a sample, ¹³ C-NMR measurement was performed under the following conditions.

¹³ C-NMR measurement conditions Measuring device: LA400 type nuclear magnetic resonance device manufactured by JEOL Ltd. Measurement mode: BCM (Bilevel Complete decoupling)
Observation frequency: 100.4MHz
Observation range: 1706.8 Hz
Pulse width: C nucleus 45 ° (7.8 μsec)
Pulse repetition time: 5 seconds Sample tube: 5 mmφ
Sample tube rotation speed: 12 Hz
Number of integrations: 20000 times Measurement temperature: 125 ° C
Solvent: 1,2,4-trichlorobenzene: 0.35 ml / heavy benzene: 0.2 ml
Sample amount: Approximately 40 mg

From the spectrum obtained by the measurement, the ratio of the monomer chain distribution (triad (triple) distribution) was determined according to the following document (1), and it was derived from ethylene in the decan-soluble part of the propylene-based polymer. The mole fraction (mol%) of the constituent unit (hereinafter referred to as E (mol%)) and the molar fraction (mol%) of the constituent unit derived from propylene (hereinafter referred to as P (mol%)) were calculated. Converted from the obtained E (mol%) and P (mol%) to mass% according to the following (Formula 1), the mass (mass%) of the structural unit derived from ethylene in the Dsol of the propylene-based polymer (hereinafter E (hereinafter E ( (Mass%)) was calculated.

Reference (1): Kakugo, M .; Naito, Y .; Mizunuma, K .; Miyatake, T., Carbon-13 NMR determination of monomer sequence distribution in ethylene-propylene copolymers prepared with delta-titanium trichloride-diethylaluminum chloride. Macromolecules 1982, 15, (4), 1150-1152

E (wt%) = E (mol%) x 28 x 100 / [P (mol%) x 42 + E (mol%) x 28] ... (Equation 1)

(2) Extreme viscosity [η]
The ultimate viscosity [η] was measured in tetralin at 135 ° C. according to a conventional method.

(3) Melt flow rate (MFR)
According to ASTM D-1238, the measurement was performed under the conditions of 230 ° C. and a load of 2.16 kg, or 190 ° C. and a load of 2.16 kg (in the case of α-olefin elastomer (D)).

(4) Density of α-olefin elastomer (D) The density of α-olefin elastomer (D) was measured according to ISO-1183 (JIS K7112).

The components used in the examples and comparative examples are as follows.

[Impact polypropylene (A)]
"A-1": Impact polypropylene
MFR (230 ° C, 2.16 kg): 60 g / 10 min
Extreme viscosity of propylene homopolymer part [η]: 1.2 dl / g
Content of propylene / ethylene copolymer part: 14.4% by mass
Extreme viscosity of propylene / ethylene copolymer: 5.7 dl / g
Ethylene content of propylene / ethylene copolymer: 30% by mass
"A-2": Impact polypropylene
MFR (230 ° C, 2.16 kg): 80 g / 10 min
Extreme viscosity of propylene homopolymer part [η]: 1.2 dl / g
Content of propylene / ethylene copolymer: 10.0% by mass
Extreme viscosity of propylene / ethylene copolymer: 7.0 dl / g
Ethylene content of propylene / ethylene copolymer: 30% by mass
"A-3": Impact polypropylene
MFR (230 ° C, 2.16 kg): 110 g / 10 min
Extreme viscosity of propylene homopolymer part [η]: 1.2 dl / g
Content of propylene / ethylene copolymer: 12.0% by mass
Extreme viscosity of propylene / ethylene copolymer: 4.0 dl / g
Ethylene content of propylene / ethylene copolymer: 24% by mass

[Homopolypropylene (B)]
"B-1": Homopolypropylene
(Made by Prime Polymer Co., Ltd., Product name: Prime Polypro VP103W)
MFR (230 ° C, 2.16 kg): 3 g / 10 min
Extreme viscosity [η]: 8.1 dl / g
"B-2": Homopolypropylene
MFR (230 ° C, 2.16 kg): 7 g / 10 min
Extreme viscosity [η]: 3.5 dl / g

[Homopolypropylene (C)]
"C-1": Homopolypropylene
(Made by Prime Polymer Co., Ltd., Product name: H-50000)
MFR (230 ° C, 2.16 kg): 500 g / 10 min

[Α-olefin elastomer (D)]
"D-1": Ethylene elastomer (ethylene / 1-decene copolymer)
MFR (190 ° C, 2.16 kg): 2 g / 10 min
Density: 0.87 g / cm ³
"D-2": Ethylene-based elastomer (ethylene / 1-butene copolymer)
MFR (190 ° C, 2.16 kg): 35 g / 10 min
Density: 0.87 g / cm ³

[Inorganic filler (E)]
"JM209": Fine powder talc (manufactured by Asada Flour Milling Co., Ltd., product name: JM209)
Average particle size: 4.1 μm

[Blowing agent (F)]
_{"N 2} system": nitrogen-based foaming agent (Eiwa Chemical Industry Co., Ltd., trade name: Porisuren EE206)
"CO ₂ system": Sodium bicarbonate / sodium citrate inorganic foaming agent (manufactured by Eiwa Kasei Kogyo Co., Ltd., trade name Polyslen EE25C, kneaded into low density polyethylene so that the foaming agent concentration is 30% by mass. Foaming agent master batch)

<Examples 1 to 4, Comparative Examples 1 to 4>
Impact polypropylene (A), homopolypropylene (B), homopolypropylene (C), α-olefin elastomer (D) and inorganic filler (E) are mixed in the amounts (parts by mass) shown in Table 1, granulated and injected. A polypropylene resin composition for foam molding was obtained. The foaming agent masterbatch containing the foaming agent (F) was dry-blended into the obtained resin composition (the amount of the foaming agent (F) itself is shown in Table 1 (parts by mass)). Then, injection foam molding was performed under the following conditions to obtain a foam molded product.

[Injection foam molding method]
-Injection molding machine: MD350S-III type (mold clamping force 350t) manufactured by Ube Machinery Co., Ltd.
-Mold cavity size: length 400 mm, width 200 mm, thickness 1.2 mm
Gate: 1 point in the center of the cavity Direct gate Injection temperature: 210 ° C or 190 ° C
Mold surface temperature: 45 ° C
Injection time: 1.0 s (time from the start of injection to the end of injection of molten resin)
・ Foam molding conditions Mold clearance after the foaming process is completed: 3.0 mm
Core back speed: 20 mm / s
Foaming start delay time after resin filling: 0 to 1s
Mold cavity clearance (L0) at the time of injection: 1.2 mm

The foam molded product obtained as described above was evaluated by the following method. Each evaluation was carried out on each of a foam molded product obtained by molding under the condition of an injection temperature of 210 ° C. and a foam molded product obtained by molding under the condition of an injection temperature of 190 ° C. The results are shown in Table 1.

(1) Foaming ratio A foaming ratio of 2.5 times or more is achieved, with _{the plate thickness before foaming being t 0} = 1.2 mm, the plate thickness after foaming being t, and the plate thickness ratio t / t _{0 being the foaming ratio.} Whether or not it was done was evaluated according to the following criteria.
"A": The thickness t of the molded product after foaming was 3.0 mm or more, and a foaming ratio of 2.5 times or more could be achieved.
"B": The plate thickness t of the molded product after foaming was less than 3.0 mm, and a foaming ratio of 2.5 times or more could not be achieved.

(2) Poor foaming The surface of the molded product after foaming was visually observed, and the presence or absence of sink marks was evaluated according to the following criteria.
"A": No sink marks were visually observed.
"B": A sink mark was visually observed.

(3) Cell shape The air bubbles in the cross section of the molded product after foaming were visually observed, and the cell shape was evaluated according to the following criteria.
"A": Only closed cells without rupture were observed.
"B": Slightly open bubbles due to rupture were observed.
"C": Rhagades were observed in the foam layer due to open cells caused by foam rupture.

(4) Cell shape 2
The average cell diameter was measured from the air bubbles visually observed in the cross section of the molded product after foaming, and evaluated according to the following criteria.
"A": It was confirmed that the average cell diameter of the bubbles was 200 μm or less, and that the cell diameters were small and uniform.
"B": The average cell diameter of the bubbles was 200 μm or less, but it was not visually recognized that the cell diameters were small and uniform.
"C": The average diameter of the bubbles exceeded 200 μm.

(5) Appearance of avatar The molded product after foaming was visually observed, and the presence or absence of avatar was evaluated according to the following criteria.
"A": No avatar was visually observed.
"B": Abata was visually observed.

As shown in Table 1, in Examples 1 to 4, when the initial input wall thickness before foaming was 1.2 mm and the foaming ratio was 2.5 times or more, the injection temperature was 210 ° C. using a nitrogen-based foaming agent. Good foam molding was possible under any of the conditions of 190 ° C. and 190 ° C., and the appearance of the molded product was also good.

It is generally known that it is relatively difficult to obtain good foamability and good appearance when a nitrogen-based foaming agent is used. Therefore, since good results were obtained even when the nitrogen-based foaming agent was used in Examples 1 to 4, the remarkable effect of the present invention can be understood.

Comparative Examples 1 to 4 were examples in which homopolypropylene (B-2) having a low ultimate viscosity [η] of 3.5 dl / g was used, and avatar was observed in the foamed molded product. In Comparative Examples 1 to 4, since the viscosity of the homopolypropylene (B-2) was low, it is considered that the gas easily went out of the system and avatar was generated.

Further, from the evaluation results of "cell shape 2" of Comparative Examples 1 to 4, the foam molded product obtained under the condition of the injection temperature of 210 ° C. had an average cell diameter of 200 μm or less, but the cell diameters were all small. It can be seen that the foam molded product obtained under the condition of an injection temperature of 190 ° C. had an average cell diameter of bubbles exceeding 200 μm. In Comparative Examples 1 to 4, since the viscosity of the homopolypropylene (B-2) was low, it was not possible to suppress the expansion of bubbles, and it is considered that bubbles having a large cell diameter were mixed or the average cell diameter became large.

Of Comparative Examples 1 to 4, Comparative Examples 3 and 4 were examples of foam molding using a nitrogen-based foaming agent, and sink marks were observed in the foam molded product. In Comparative Examples 3 and 4, since the nitrogen-based foaming agent was used and the viscosity of the homopolypropylene (B-2) was low, it is considered that the gas easily went out of the system and sink marks occurred.

Further, from the evaluation results of the "cell shape" of Comparative Examples 3 and 4, it can be seen that the foamed molded product obtained under the condition of the injection temperature of 190 ° C. showed a slight amount of open cells due to defoaming. In Comparative Examples 3 and 4, since the nitrogen-based foaming agent was used and the viscosity of the homopolypropylene (B-2) was low, it was not possible to suppress the expansion of bubbles, and it is probable that open cells were generated due to bubble rupture.

The polypropylene resin composition for injection foam molding of the present invention can be suitably used for foam molding, particularly injection foam molding. The injection-foamed polypropylene resin composition molded product of the present invention using this resin composition can be suitably used for various purposes such as, for example, automobile interior / exterior parts, substitutes such as cardboard, electric appliances, building materials, and the like. It is suitable for applications of automobile interior parts and automobile exterior parts.

Claims (7)

The melt flow rate (MFR) measured by ASTM D-1238 at 230 ° C. and a load of 2.16 kg is 30 to 200 g / 10 min, and the propylene homopolymer portion specified as the n-decane insoluble portion (Dinsol) at 23 ° C. Impact Polypropylene (A) 30-96 parts by mass, wherein the ultimate viscosity [η] in tetralin at 135 ° C. is 0.8-3.0 dl / g.
1 to 10 parts by mass of homopolypropylene (B) having an intrinsic viscosity [η] of 6 to 10 dl / g in tetralin at 135 ° C.
Homopolypropylene (C) 3 to 29 parts by mass α-olefin elastomer (D) 0 to 30 parts by mass having a melt flow rate (MFR) of 200 to 1000 g / 10 min measured by ASTM D-1238 at 230 ° C. and a load of 2.16 kg. Parts and 0 to 30 parts by mass of the inorganic filler (E) [100 parts by mass of the total amount of the components (A) to (E)]
A polypropylene resin composition for injection foam molding comprising. Impact Polypropylene (A) has an extreme viscosity [η] of 1.0 to 10 dl / g in tetralin at 135 ° C. of the propylene / ethylene copolymer part specified as the n-decane soluble part (Dsol) at 23 ° C. The polypropylene resin composition for injection foam molding according to claim 1. The content of the propylene homopolymer portion specified as the n-decane insoluble portion (Dinsol) at 23 ° C. in the impact polypropylene (A) is 70 to 97% by mass, and the n-decane soluble portion (Dsol) at 23 ° C. The polypropylene resin composition for injection foam molding according to claim 1 or 2, wherein the content of the propylene / ethylene copolymer portion specified as) is 3 to 30% by mass. The polypropylene resin composition for injection foam molding according to any one of claims 1 to 3, wherein the α-olefin elastomer (D) is an ethylene-based elastomer. The polypropylene resin composition for injection foam molding according to any one of claims 1 to 4, wherein the inorganic filler (E) is talc. Foaming agent (F) 0, which is an inorganic or organic chemical foaming agent, with respect to the resin composition [total amount of components (A) to (E) 100 parts by mass] according to any one of claims 1 to 5. An injection-foamed polypropylene resin composition molded product obtained by injection-foaming molding by adding 1 to 10 parts by mass. The injection-foamed polypropylene resin composition molded product according to claim 6, wherein the initial charged wall thickness before foaming is 1.0 to 2.0 mm, and the foaming ratio is 1.5 times or more.