JP2003020353A - Olefinic resin composition for injection foaming and injection foamed body thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop an olefinic resin composition for injection foaming whose composition is excellent in the moldability and gives an injection foamed body having impact resistance, and to obtain an injection foamed body thereof. SOLUTION: The olefinic resin composition for injection foaming, comprises the olefinic resin (A) and olefinic resin (B), both of which have different melt flow rates(MFR) respectively, one of which has a melt flow rate of not less than 50 g/10 min, the other of which has a melt flow rate of less than 50 g/10 min, and the difference between the MFRs of which is 20 g/10 min or more, and the resin composition contains them in the range of (A):(B)=60-99:1-40 (weight ratio); the injection foamed body is made by a general injection foaming, using the above olefinic resin composition.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an olefin resin composition for injection foam molding and an injection foam molding comprising the same.

[0002]

2. Description of the Related Art In recent years, in order to reduce the weight and cost of automobile interior materials such as instrument panels, injection foam moldings using olefin resins such as propylene resins have been tried.

For example, in Japanese Patent Laid-Open No. 11-179752, the melt flow rate (MFR) is 10 to 200 g.
A method for manufacturing automobile interior parts using an olefin resin of / 10 minutes as a molding raw material is disclosed.
High MF with R of 50g / 10min and 80g / 10min
An example in which the R propylene / ethylene block copolymer resins are used alone is specifically shown.

However, when such a high MFR olefin resin is used alone as a resin raw material, the molding processability is good, but the impact resistance of the obtained foamed molded article is lowered. Therefore, it has been desired to develop a foamed molding material which is excellent in molding processability and whose molded product has impact resistance.

[0005]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The present inventors have completed the present invention as a result of investigations to develop an olefin resin composition for injection foam molding, which has excellent molding processability and in which the obtained injection foam molded article has impact resistance.

[0006]

According to the present invention, the melt flow rate (MFR) is 50 g / 10 minutes or more and less than 50 g / 10 minutes, respectively, and the difference in MFR between the two is 2%.
The olefin resin (A) and the olefin resin (B) having different MFRs of 0 g / 10 minutes or more are (A):
The present invention provides an olefin resin composition for injection foam molding, which is contained in the range of (B) = 60 to 99: 1 to 40 (weight ratio), and also relates to such olefin resin composition for injection foam molding. The present invention provides an injection foam molded product obtained by injection foam molding.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The olefin resin composition for injection foam molding according to the present invention has a melt flow rate (MF).
R) is 50 g / 10 min or more and 50 g / 10
The olefin-based resin composition comprises an olefin-based resin (A) and an olefin-based resin (B) having different MFRs that are less than 20 minutes / 10 minutes and have a difference in MFR of 20 g / 10 minutes or more.

The MFR of the olefin resin (A), which is one of the resin components in the present invention, is higher as the MFR is higher because the fluidity of the olefin resin composition at the time of melting is improved.
It is necessary to be 0 g / 10 minutes or more, but since the impact resistance tends to decrease as the MFR increases, the upper limit is about 300 g / 10 minutes.

Examples of such an olefin resin (A) include homopolymers or copolymers of propylene, ethylene, butene-1, hexene-1, 4-methylpentene-1, and the like. Polypropylene resin is preferably used. Polypropylene resin is a known propylene-based polymer, and examples thereof include propylene homopolymer, propylene and other α.
-Copolymer with olefin, for example, propylene-ethylene copolymer, propylene-ethylene block copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer and the like can be mentioned. Of these, polypropylene-ethylene block copolymers are particularly desirable.

The method for producing such an olefinic resin (A) is not particularly limited, and it can be produced by various conventionally known methods. For example, for a propylene-ethylene block copolymer, for example, , A known polymerization method, such as a Ziegler-Natta catalyst system and / or a metallocene catalyst system, is a known polymerization method such as a bulk polymerization method, a solution polymerization method, a slurry polymerization method or a gas phase polymerization method, or a polymerization method thereof. Can be manufactured in any combination. However, whichever method is used, the MFR of the obtained olefin resin must be 50 g / 10 minutes or more in order to be used as the olefin resin (A).

The MFR of the olefin resin (B), which is another resin component in the present invention, is required to be less than 50 g / 10 minutes because the smaller the MFR, the higher the impact resistance of the obtained molded product. However, if the MFR becomes too small, the fluidity of the olefin resin composition during melting in the molding process will be extremely deteriorated, so the lower limit is about 0.1 g / 10 minutes.

As such an olefin resin component (B), a homopolymer or copolymer of propylene, ethylene, butene-1, hexene-1, 4-methylpentene-1 or the like can be used. These are also produced by various conventionally known methods, and the production method is arbitrary, but in order to use as the olefin resin (B), the MFR of the obtained olefin resin is 50 g /
It should be less than 10 minutes.

In the combination of the olefin resin (A) and the olefin resin (B), the olefin resin (B) depends on the compatibility and dispersibility with the olefin resin (A) used in combination. Appropriately selected,
For example, when a propylene homopolymer or a propylene / ethylene block copolymer is used as the polyolefin resin (A), it is preferable to use the same polypropylene resin as the olefin resin (B).
It is also possible to use a polyolefin resin that is slightly crosslinked or has a branched molecular chain.

In the present invention, the MF of each of the olefin resin (A) and the olefin resin (B) is
Even if R is within the range specified above, it is necessary to combine the two so that the difference in MFR between them is 20 g / 10 minutes or more, and preferably 40 g / 10 minutes.

In the resin composition of the present invention, the higher the difference in MFR between the two olefin resins (A) and (B), the higher the fluidity and the high impact resistance can be obtained. For example, the olefin resin (A) has an MFR of 5
In order to obtain good fluidity (molding processability) and impact resistance when a propylene / ethylene block copolymer of 5 g / 10 min is used, the olefin resin (B) has an MFR of 35.
g / 10 minutes or less, especially 15 g /
It is preferably 10 minutes or less. When a propylene / ethylene block copolymer having an MFR of 100 g / 10 min is used as the olefin resin (A), the MFR of the olefin resin (B) needs to be less than 50 g / 10 min. Yes, in such a case, even if the MFR of the olefin resin (A) and the olefin resin (A)
Even if the difference is 20 g / 10 minutes or more, the desired effect cannot be obtained if the MFR of the olefin resin (B) is 50 g / 10 minutes or more.

The mixing ratio of the olefin resin (A) and the olefin resin (B) is (A) :( B) = weight ratio.
60 to 99: 1 to 40, preferably (A) :( B) = 7
It is 0 to 95: 5 to 30. The mixing ratio of both components is appropriately determined depending on the kinds of olefin resins (A) and (B) used and various properties such as required fluidity, but if the mixing ratio is out of the above range, satisfactory performances cannot be obtained. . For example, even if the difference in MFR between the olefin resin (A) and the olefin resin (B) is 20 g / 10 minutes or more, if the difference is relatively small and close to 20 g / 10 minutes, the olefin resin ( By making the mixing ratio of B) relatively high, high fluidity and impact resistance can be obtained. On the contrary, the difference in MFR between the olefin resin (A) and the olefin resin (B) is large, and for example, the difference is 4
When it exceeds 0 g / 10 minutes, high fluidity and impact resistance can be obtained by relatively reducing the mixing ratio of the olefin resin (B).

As a method for mixing the olefin resin (A) and the olefin resin (B), for example, a method of mixing at a polymerization stage by known multi-stage polymerization or the like, or pellets prepared in advance in an extruder are used. A method of melt-kneading using, or a method of melt-kneading a pellet-blended product with a direct injection molding machine, etc., the method is optional, but in terms of versatility, the latter pellet-blended product is extruded. And a method of melt-kneading with an injection molding machine is preferable.

The olefin resin (A) mentioned above is used.
The olefin resin (B) and the olefin resin (B) do not need to be independent olefin resins, and if necessary, either or both of the olefin resin (A) and the olefin resin (B) fall within the above-mentioned MFR range. In the above, a mixture composed of two or more kinds of olefin-based resins having different MFRs may be used. For example, a resin mixture obtained by mixing two or more kinds of olefin-based resins each having an MFR of 50 g / 10 minutes or more may be used as the olefin-based resin (A), and similarly, the MFR of each individual may be 50 g. A resin mixture obtained by mixing two or more kinds of olefin resins for less than / 10 minutes may be used as the olefin resin (B), and the MFR of the olefin resins (A) and (B) formed of such a mixture is It may be MFR in the mixture. Further, when the olefin resin (A) and the olefin resin (B) as described above are a mixture, the respective mixture is regarded as the olefin resin (A) and the olefin resin (B) in the above-mentioned proportions. Just mix.

In producing an injection foam molding using the olefin resin composition containing the olefin resin (A) and the olefin resin (B),
A foaming component is incorporated into the composition. As the foaming component at this time, a gas such as carbon dioxide gas or nitrogen gas or a liquefied gas thereof in a supercritical state by a conventionally known method may be directly pressed into a molten olefin resin composition for use. Or, conventionally known organic or inorganic chemical foaming agents may be used alone, or a mixture thereof may be used, or these may be used in combination. When carbon dioxide gas or nitrogen gas is used, for example, JP-A-10-2
Using an apparatus such as that shown in 30528, the mixture is directly pressed into the molten resin and kneaded.

When a chemical foaming agent is used, it is desirable to use a powdery foaming agent from the viewpoint of excellent dispersibility in the olefin resin composition. The chemical foaming agent may be added and blended as it is at the time of melt-kneading with the olefin resin composition, but generally, the chemical foaming agent is kneaded into the thermoplastic resin so that the content thereof becomes 20 to 80% by weight. A crushed masterbatch is used by blending the masterbatch with an olefin resin composition.

Examples of the organic chemical foaming agent include azodicarbonamide, oxybenzenesulfonyl hydrazide, azobisisobutyronitrile, barium azodicarboxylic acid, and hydrazodicarbonamide. Examples include sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, ammonium nitrite, citric acid, succinic acid and adipic acid.

When carbon dioxide gas or nitrogen gas is directly injected into the molten resin in a gaseous state or in a supercritical state, the amount of the gas is usually 0.1% with respect to 100 parts by weight of the olefin resin composition.
It is 5 to 10 parts by weight. When a chemical foaming agent is used, its amount is usually 100 olefin resin composition.
It is 0.5 to 5 parts by weight as a foaming agent with respect to parts by weight.

In the olefin resin composition of the present invention, various additives such as a neutralizing agent, an antioxidant, an antistatic agent, an ultraviolet absorber, and the like may be added as necessary so long as the effects of the present invention are not impaired. A pigment, a filler such as talc, a nucleating agent and the like can be added.

Next, a method for producing an injection foam molding using the above-mentioned olefin resin composition will be described.
A conventionally known method is applied to the injection foam molding method itself and is not particularly limited. For example, as described below, a molten olefin system containing a foaming component in a mold cavity of a mold composed of a male and female pair. After supplying and filling the resin composition, a mold cavity of a part or the whole of the mold is expanded according to a desired product shape, and the molten olefin resin composition is foamed to obtain an injection foam molded article. Obtainable.

FIG. 1 is a schematic sectional view showing an example of a mold used in this method. This mold consists of a male and female pair of male mold (1) and female mold (2). Usually, one of the two molds is connected to a mold clamping device such as a press machine, and the other mold is fixed to the longitudinal direction. Alternatively, both molds can be opened and closed laterally. In the figure, the male die (1) is fixed and the female die (2) is connected to a pressing device (not shown) so that both dies can be opened and closed in the vertical direction.

Although the method of supplying the molten olefin resin composition into the mold cavity is arbitrary, generally, a fluid press-fitting device, which will be described later, is provided via a resin supply passage (4) provided in the mold. A resin supply port (6) connected to a resin supply device (5) such as an attached injection machine is provided on the molding surface of one or both of the male and female molds, and the molten olefin system is introduced into the cavity from the resin supply port. A method of supplying the resin composition is preferable. In this case, a controllable open / close valve is provided in the resin supply passage (4) near the resin supply port (6) to supply the molten olefin resin composition stored in the resin supply device,
It is desirable that the stop can be controlled arbitrarily.

The molten olefin resin composition (3) is supplied into the mold cavity formed by such a mold. (FIG. 2) The molten olefin resin composition may be filled in the mold cavity by injection filling with both molds closed at a predetermined cavity clearance, or in an open state. The molten olefin resin composition may be supplied between both molds and then filled by the mold clamping operation of both molds. However, in order to obtain a stable foamed molded product, both molds should be closed. The method of injection filling in the closed state is preferable. In the case of injection filling, the molten olefin resin composition (3) can be supplied with both molds closed so that the cavity clearance is smaller than the thickness of the molded product before foaming or the thickness of the molded product before foaming. . At this time, 0.1-10 MPa in the mold cavity in advance
It may be filled with a pressurized fluid of a certain degree.

When starting the supply of the molten olefin resin composition (3) with both molds closed so that the cavity clearance is smaller than the thickness of the molded product before foaming,
The cavity clearance at the start of supply is such that the cavity volume at that time is usually 5% by volume or more and less than 100% by volume with respect to the required volume of the molten olefin resin composition before foaming, more preferably 30% by volume. As described above, it is less than 70% by volume. As the supply of the molten olefin resin composition progresses, the cavity clearance is expanded,
The supply of the required amount of molten olefin resin composition is completed. At this point, the volume of the supplied molten olefin resin composition and the cavity volume become substantially equal, and the cavity is filled with the molten olefin resin composition.

At this time, the cavity volume may become larger than the volume of the molten olefin resin composition when the supply of the molten olefin resin composition is completed.
In this case, the molten olefin resin composition is filled in the cavity by performing mold clamping so that a predetermined cavity clearance is obtained. (FIG. 3) When the molten olefin resin composition is supplied for a long time, the temperature of the olefin resin composition during supply is lowered. Therefore, the molten olefin resin composition should be supplied promptly. Is preferred, and here 0.5 to 5
It is about a second.

The expansion of the above-mentioned cavity clearance is
The expansion may be controlled positively by a pressing device or the like with a mold attached thereto, or the supply pressure of the molten olefin resin composition to be supplied may be used for expansion.

When the molten olefin resin composition (3) is supplied and filled in the cavity with both molds positioned so that the cavity clearance is the same as the thickness of the molded product before foaming, As in the case of injection molding, the cavity clearance may be maintained to be the same as the thickness of the molded product before foaming from the start of the supply of the molten olefin resin composition to the completion of the supply.

As a method of filling the molten olefin resin composition into the cavity by the clamping operation of both molds, both molds are opened so that the cavity clearance is larger than the thickness of the molded product before foaming. After supplying the required amount of molten olefinic resin composition in this state, and after supplying the molten olefinic resin composition in this state or at the same time as the supply is completed, the cavity clearance becomes the same as the thickness of the molded product before foaming. A method of tightening and filling, or starting the supply of the molten olefin resin composition with both molds open so that the cavity clearance is larger than the thickness of the molded product before foaming, and the molten olefin resin composition While the mold clamping is started while supplying the molten olefin resin composition and the mold clamping is performed in parallel with the molten olefin resin composition. Supply completion simultaneously with or cavity clearance after completion of the feeds of and a method of performing mold clamping to be the same as the molded body thickness before foaming.

The temperature of the molten olefin resin composition (3) to be supplied is appropriately selected depending on the kind of the raw material olefin resin composition, various additives, various mixing materials and the like. For example, the melting temperature is 160 ° C. When the above propylene / ethylene block copolymer is used as the olefin resin (A), the temperature is 170 to 230 ° C., preferably 180 to 21 ° C.
It is about 0 ° C.

The mold cavity filled with the molten olefin resin composition (3) by the above method is
It is kept at a high pressure and has almost no voids.
In this state, the surface of the molten olefin resin composition in contact with the molding surface is solidified to form the unfoamed layer (7). Generally, the mold temperature is higher than the melting point or softening point of the olefin resin used. Since this is also set to a low temperature, if this state is maintained and cooling is performed, the supplied molten olefin resin composition begins to solidify from the surface portion in contact with the mold molding surface, and eventually there are almost no voids. An unfoamed layer (7) is formed.

The temperature of the mold is appropriately determined according to the olefin resin used. For example, when a propylene / ethylene block copolymer is used as the olefin resin (A), it is preferably about 20 ° C. to 80 ° C. 30-60 ° C
It is a degree. In this case, the above cooling time is 0.1 to 5
It is about a second.

After the predetermined unfoamed layer (7) is formed, when the mold cavity is opened in the thickness direction of the molded body, the cell nuclei trapped in the supplied molten olefin resin composition expands. While forming the foam layer (8), at the same time, as a whole, the thickness is increased in the opening direction of the mold, that is, the thickness direction. (Figure 4)

When the cavity clearance reaches the final molded body thickness after foaming, the opening operation of the mold is stopped, and the molded body is cooled while maintaining the cavity clearance at this thickness.

At this time, after the mold is opened so that the cavity clearance is once larger than the final molded body thickness, the final molded body thickness is adjusted while a part of the foamed layer of the olefin resin composition is still in a molten state. It may be clamped until it is finished. In this case, the adhesion between the surface of the foamed molded product and the molding surface of the mold can be improved, the shape of the mold can be reproduced more faithfully, and the cooling efficiency can be increased.
The mold clamping operation at this time may be mechanically controlled,
When both molds are opened vertically, the cavity may be reduced by the weight of the upper mold.

After cooling is completed, the mold is completely opened,
When the olefin resin injection foamed molded product which is the final molded product is taken out from the mold (FIG. 5), an injection foamed molded product having an unfoamed layer (7) on the surface and a foamed layer (8) inside ( 9) can be obtained.

[0040]

EXAMPLES The present invention will be described below with reference to examples, but these are merely examples and the present invention is not limited to these examples. The methods for measuring the physical properties of the resin components and compositions used in the examples and comparative examples are shown below. (1) Melt flow rate (MFR, unit: g / 10
Min) Measured according to the method defined in JIS-K-6758. Unless otherwise specified, the measurement temperature was 230 ° C. and the load was 2.16 kg. (2) Impact resistance (DuPont impact) A 60 mm x 60 mm sample was cut out from an arbitrary flat portion of a disc-shaped olefin resin foam molded product of φ300 mm, and the test temperature was 23 ° C, the load was 9.8 N, and the dart tip r = 1
A load drop impact test was performed at / 4 in. The height at which the load was dropped was changed, and a load drop test was performed on each of the five pieces, and the height at which cracks did not occur in all the samples was determined. The energy value (J) at this time was taken as the value of DuPont impact.

Example 1 90 parts by weight of propylene-ethylene block copolymer (pellet form) with MFR = 55 g / min and 10 parts by weight of propylene-ethylene block copolymer (pellet form) with MFR = 10 g / min were mixed. , And resin material. A masterbatch containing 40 parts by weight of an inorganic foaming agent as a foaming component in 100 parts by weight of this resin material (Celmic MB3064:
Molding material with 3 parts by weight of Sankyo Kasei Co., Ltd.
m and a theoretical injection capacity of 750 cc were melt-kneaded at 200 ° C. with an in-line type injection machine and weighed about 130 g. φ3
A pair of disc-shaped molds having a cavity of 05 mm and a thickness of 2 mm and the mold temperature kept at 50 ° C. were injection-filled in about 1.5 seconds. One second after the completion of filling, the opening of the mold was started in the direction of increasing the cavity thickness, and the opening operation of the cavity was stopped when the cavity thickness reached 4 mm after about 2 seconds. After cooling the foam for 30 seconds while maintaining this state, both molds were opened and the olefin resin foam molded product was taken out. Table 1 shows the impact resistance of the obtained olefin resin injection foamed molded product having a diameter of 300 mm and a thickness of 4 mm. The olefin resin composition used in this example has MFR
The resulting foamed molded article was excellent in impact resistance.

Example 2 70% of propylene-ethylene block copolymer (pellet form) as MFR = 55 g / min was used as an olefin resin.
Φ300 mm, thickness 4 m in the same manner as in Example 1 except that 30 parts by weight of a propylene-ethylene block copolymer (pellet form), MFR = 30 g / min.
Thus, an olefin resin injection foam molding of m was obtained. Table 1 shows the impact resistance of the obtained olefin resin injection foam molded article. The olefin resin composition used in this example is M
The FR was high, the fluidity was excellent, the moldability was excellent, and the foamed molded product obtained had excellent impact resistance.

[0043]

[Table 1]

Comparative Example 1 φ300 mm, thickness 4 mm in the same manner as in Example 1 except that propylene-ethylene block copolymer alone having MFR = 100 g / min was used as the olefin resin.
To obtain an olefin resin injection foamed molded article. In this example, the fluidity of the molten resin was high and the moldability was excellent, but the DuPont impact value (J) of the obtained foamed molded product was 0.
It was as low as 49.

Comparative Example 2 Olefin resin injection foam molding having a diameter of 300 mm and a thickness of 4 mm in the same manner as in Example 1 except that propylene-ethylene block copolymer alone having MFR = 55 g / min was used as the olefin resin. Got the body In this example,
The flowability of the molten resin was high and the moldability was excellent,
The DuPont impact value (J) of the obtained foamed molded product was 0.56.
Was low.

Comparative Example 3 Olefin resin injection foam molding having a diameter of 300 mm and a thickness of 4 mm was carried out in the same manner as in Example 1 except that a propylene-ethylene block copolymer alone having an MFR of 30 g / min was used as the olefin resin. Got the body In this example,
The DuPont impact value (J) of the obtained foamed molded product was 0.69.
And the impact resistance was excellent, but the fluidity of the molten resin was relatively low and the moldability was poor.

[0047]

INDUSTRIAL APPLICABILITY The olefin resin composition for injection foam molding of the present invention is excellent in molding processability because of its high fluidity at the time of melting, and the injection foam molding obtained therefrom has excellent impact resistance. It is widely used in automobile fields such as automobile interior materials, home appliances, and building materials fields.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an example of a mold used for producing an injection-foam molded article.

FIG. 2 is a schematic sectional view of a mold showing a manufacturing process of an injection foam molding.

FIG. 3 is a schematic cross-sectional view of a mold showing a manufacturing process of an injection foam molding.

FIG. 4 is a schematic cross-sectional view of a mold showing a manufacturing process of an injection foam molding.

FIG. 5 is a schematic cross-sectional view of a mold showing a manufacturing process of an injection foam molding.

[Explanation of symbols]

1: Male 2: Female 3: Molten olefin resin composition 4: Resin supply path 5: Resin supply device 6: Resin supply port 7: Non-foamed layer 8: Foam layer

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B29K 105: 04 B29K 105: 04 B29L 31:58 B29L 31:58 F term (reference) 4F074 AA17 AA24 AB05 BA01 BA31 4F206 AA03 AG20 AH26 JA04 JQ81 4J002 BB03W BB04W BB11X BP02W FD326

Claims (5)

[Claims] 1. A melt flow rate (MFR) of 50 g / 10 minutes or more and less than 50 g / 10 minutes, respectively,
MF with a difference in MFR between the two of 20g / 10 minutes or more
The olefin resin (A) and the olefin resin (B) having different R are represented by (A) :( B) = 60 to 99: 1 to 40.
An olefin resin composition for injection foam molding, characterized in that it is contained in a range of (weight ratio). 2. The olefin resin (A) has an MFR of 50 to 50.
The olefin resin composition for injection foam molding according to claim 1, wherein the olefin resin (B) has an MFR of 300 g / 10 minutes and 0.1 g / 10 minutes or more and less than 50 g / 10 minutes. 3. The olefin resin composition for injection foam molding according to claim 1, wherein the difference in MFR between the olefin resin (A) and the olefin resin (B) is 40 g / 10 minutes or more. 4. The olefin resin composition for injection foam molding according to claim 1, wherein the olefin resin (A) is a propylene / ethylene block copolymer. 5. An injection-foam molded article obtained by injection-foam-molding the olefin resin composition for injection foam molding according to claim 1.