JP2014173012A - Polypropylene-based resin foam particle and compact thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polypropylene-based resin foam particle which is suppressed in embrittlement of foam at low temperatures and has good low-temperature impact resistance, and a compact thereof.SOLUTION: A polypropylene-based resin foam particle is produced from a polypropylene-based resin composition which has a melting point of 125-150°C, shows a single peak in the range of -20 to 20°C in a temperature-loss tangent(tanδ) curve obtained by solid dynamic viscoelasticity measurement, a temperature of the peak of 8°C or lower and a maximum value of tanδ of 0.12 or greater. A polypropylene-based resin foam particle has such a crystalline structure that there appear an endothermic peak (intrinsic peak) intrinsic to the polypropylene-based resin composition and another endothermic peak (high-temperature peak) on the high-temperature side relative to the intrinsic peak in the DSC curve (DSC curve for first heating) obtained when heating 1-3 mg of the foam particles from 25°C to 200°C at a programming rate of 10°C/min by the heat flux differential scanning calorimetry.

Description

  TECHNICAL FIELD The present invention relates to a polypropylene resin expanded particle and a molded product thereof. More specifically, the present invention relates to a polypropylene resin expanded particle capable of suppressing the embrittlement of a foam at a low temperature and improving low temperature impact resistance, and the expanded molded product thereof. It is about.

  Polypropylene resin foam particles molded body obtained from in-mold foaming of polypropylene resin foam particles is superior in chemical resistance, impact resistance, compression strain recovery, etc., compared to polystyrene resin foam particles molded body, It is used in a wide range of fields such as electrical / electronics, automobiles, building materials, and miscellaneous goods. In general, a propylene-ethylene random copolymer is used as the base resin of the polypropylene resin expanded particles because of excellent balance between the fusion property at the time of molding and the mechanical strength of the obtained molded body.

  It has been reported so far that polypropylene resin expanded resin molded articles exhibit large energy absorption characteristics at room temperature, but become brittle and deteriorate in low temperature atmosphere. Cracking or chipping of this polypropylene resin foam in a low temperature atmosphere is an obstacle to advance into new applications.

Foamed particle moldings obtained from polypropylene resin foamed particles based on a propylene-ethylene random copolymer polymerized using a Ziegler-Natta catalyst as a resin base contain an ethylene component. Although the impact resistance is strong, the impact resistance at cryogenic temperatures was insufficient depending on the application.
Further, in the foamed particle molded body obtained from the polypropylene resin foamed particle using a propylene-ethylene random copolymer polymerized using a metallocene catalyst as a resin base material, it is generally more resistant than the above Ziegler type. The impact resistance was strong, but the impact resistance at extremely low temperatures was still insufficient.
Furthermore, the propylene-ethylene block copolymer is excellent in impact resistance due to the large amount of ethylene component, but the melting point is as high as 160 ° C. or higher, and the polypropylene resin foamed particles have a propylene-ethylene block copolymer as a base resin. In the obtained foamed particle molded body, the molding pressure is about the same as that of homopolypropylene, that is, the molding pressure is 0.50 MPa (gauge pressure) or more, and foam molding is substantially impossible with the conventional molding apparatus. It was. Moreover, even if a molded body was obtained, the fusion between the expanded particles was likely to be insufficient, and the desired low temperature impact resistance could not be obtained.
Furthermore, even in the foamed particle molded body obtained from the polypropylene resin foamed particles using the propylene-ethylene block random copolymer as a base resin, the impact resistance at low temperature was still insufficient.

As a solution to this problem, a polypropylene resin foamed particle molded body obtained from a resin in which a rubber phase of an ethylene-propylene block copolymer and a thermoplastic resin phase of a propylene-ethylene random copolymer are combined is used for impact resistance at low temperatures. It has been proposed as a foam having high properties (for example, Patent Document 1).
However, in this foam, the low-temperature impact resistance is improved by the rubber component, but the low-temperature impact resistance is still inadequate. Further, when rubber is contained, foam breakage occurs when foamed particles are foamed or molded in-mold. There is a problem that it is often done, and recyclability is inferior.

JP-A-5-202221

Thus, conventionally, polypropylene-based resin expanded particles that can sufficiently improve low-temperature impact resistance have not been obtained.
The present invention has been made under such circumstances, and an object of the present invention is to provide a polypropylene resin expanded particle and a molded product thereof that can improve sufficient low temperature impact resistance.

As a result of intensive studies to achieve the above object, the present inventors have obtained the following knowledge.
That is, in a polypropylene resin expanded particle containing a propylene-ethylene block copolymer, a temperature-loss tangent (tan δ) curve obtained from a solid dynamic viscoelasticity measurement of a base resin of the expanded particle is -20 to 20 ° C. In the DSC curve (DSC curve of the first heating) having 1 to 3 mg of the foamed particles having a characteristic in the range and a heat flux differential scanning calorimetry method, an endothermic peak (inherent peak) inherent to the polypropylene resin composition ) And an endothermic peak (high temperature peak) on the higher temperature side than the intrinsic peak, the polypropylene resin foamed particles have low temperature impact without impairing the excellent mechanical strength inherent to the polypropylene resin. It has been found that a foamed particle molded body having excellent properties can be obtained.
The present invention has been completed based on such findings.

That is, the present invention
(1) Propylene-ethylene block copolymer (a) having a melting point of 125 to 140 ° C. and an ethylene component content of 3 to 8% by weight (hereinafter sometimes referred to as “copolymer (a)”). ] From the solid dynamic viscoelasticity measurement of the polypropylene resin composition, the melting point of the polypropylene resin composition is 125 to 150 ° C. The obtained temperature-loss tangent (tan δ) curve has a single peak in the range of −20 to 20 ° C., the temperature showing the peak is 8 ° C. or lower, and the maximum value of tan δ is 0.12 or higher. In a DSC curve (DSC curve of the first heating) obtained when 1 to 3 mg of the expanded particles are heated from 25 ° C. to 200 ° C. at a temperature rising rate of 10 ° C./min by a heat flux differential scanning calorimetry method, Polypropylene having a crystal structure in which an endothermic peak (inherent peak) unique to a polypropylene resin composition and an endothermic peak (high temperature peak) on a higher temperature side than the intrinsic peak appear. Pyrene-based resin expanded particles,
(2) The propylene-ethylene random copolymer (b) having a melting point of 130 to 155 ° C. and an ethylene component content of less than 5% by weight (excluding 0) (hereinafter referred to as “copolymer”). It may be referred to as “polymer (b)”. And the weight ratio of the copolymer (a) to the copolymer (b) is 40:60 to 90:10, and the expanded polypropylene resin particles according to (1),
(3) The polypropylene resin composition may be referred to as an ethylene polymer (c) [hereinafter referred to as “polymer (c)”. The polypropylene resin expanded particles according to (1) or (2), wherein the content of the polymer (c) in the polypropylene resin composition is 1 to 30% by weight,
(4) The copolymer (a) is a propylene homopolymer or a propylene-ethylene random copolymer component (a-1) having an ethylene content of 7% by weight or less in the first step using a metallocene catalyst. It may be referred to as (a-1). 30 to 95% by weight of propylene-ethylene random copolymer component (a-2) containing 3 to 20% more ethylene than component (a-1) in the second step [hereinafter referred to as component (a) -2). ] The polypropylene resin expanded particles according to any one of (1) to (3), which are propylene-ethylene block copolymers obtained by sequential polymerization of 70 to 5% by weight,
(5) The polypropylene-based resin expanded particles according to any one of (1) to (4), wherein the apparent density of the expanded particles is 20 to 300 g / L, and (6) any one of (1) to (5) A polypropylene resin foamed particle molded article, which is formed by molding the polypropylene resin foamed particle according to the above in-mold,
Is to provide.

According to the expanded polypropylene resin particles of the present invention, it is possible to suppress the embrittlement at a low temperature and obtain a molded polypropylene resin expanded particle having good low temperature impact properties.
The molded article of the expanded polypropylene resin particles of the present invention has improved impact resistance in an extremely low temperature atmosphere of −30 ° C. which has been difficult until now without impairing the excellent mechanical strength inherent to the expanded polypropylene resin particles. The foamed molded body is less likely to cause problems such as cracking and chipping at low temperatures, and can be suitably used for packaging materials, automotive shock absorbers / spacer parts, heat insulating materials for buildings, sound absorbing materials, etc. In particular, it can be suitably used for automobile applications.

3 is a temperature-loss tangent (tan δ) curve obtained from solid dynamic viscoelasticity measurement of a polypropylene resin composition according to the present invention. It is a figure which shows the 1st DSC curve of the polypropylene resin expanded particle which concerns on this invention.

First, the polypropylene resin expanded particles of the present invention will be described.
The expanded polypropylene resin particles of the present invention are expanded particles used in an in-mold molding method in which a mold is filled and heat-molded. The melting point is 125 to 140 ° C. and the ethylene component content is 3 to 8 weights. % Foamed particles having a polypropylene resin composition containing a% propylene-ethylene block copolymer (a) as a base resin.
Further, the melting point of the polypropylene resin composition is 125 to 150 ° C., and the temperature-loss tangent (tan δ) curve obtained from the solid dynamic viscoelasticity measurement is in the range of −20 to 20 ° C. as shown in FIG. In which the temperature showing the peak is 8 ° C. or less and the maximum value of tan δ is 0.12 or more.
In addition, in a DSC curve (DSC curve of the first heating) obtained when 1 to 3 mg of expanded particles are heated from 25 ° C. to 200 ° C. at a temperature rising rate of 10 ° C./min by a heat flux differential scanning calorimetry method, As shown in FIG. 2, a crystal structure in which two endothermic peaks, an endothermic peak (inherent peak) PTma inherent in the polypropylene resin composition, and an endothermic peak (high temperature peak) PTmb on the higher temperature side than the intrinsic peak appear. Have.
Hereinafter, the configuration of the expanded polypropylene resin particles of the present invention will be described.

The expanded polypropylene resin particles of the present invention have a temperature-loss tangent (tan δ) curve obtained from solid dynamic viscoelasticity measurement (DMA) of the polypropylene resin composition constituting the expanded particles in the range of -20 to 20 ° C. It has a single peak, the temperature showing the peak is 8 ° C. or less, and the maximum value of tan δ is 0.12 or more.
The temperature showing the peak of the tan δ curve is 8 ° C. or less, preferably 0 ° C. or less, more preferably −5 ° C. or less, and the maximum value of tan δ at 8 ° C. or less is 0.12 or more, preferably 0.16 That's it.
When a single peak is not shown, or when the temperature showing a single peak (top) exceeds 8 ° C. even if the peak is single, the polypropylene resin foamed particle molded body satisfies low temperature impact properties. Can't get.

  The melting point of the polypropylene-based resin composition is 125 to 150 ° C., preferably 125 to 145 ° C., more preferably 130 to 145 ° C., and particularly preferably 130 to 140 ° C. At this time, it is preferable in that a good foamed particle molded body can be obtained without excessively increasing the heating temperature, and the rigidity, heat resistance and the like of the obtained foamed particle molded body are ensured.

[Propylene-ethylene block copolymer (a)]
The polypropylene resin composition constituting the polypropylene resin expanded particles of the present invention includes a propylene-ethylene block copolymer (a) having a melting point of 125 to 140 ° C. and an ethylene component content of 3 to 8% by weight. Is included.
The propylene-ethylene block copolymer (a) has a melting point of 125 to 140 ° C, preferably 125 to 135 ° C, more preferably 130 to 135 ° C, thereby containing the propylene-ethylene block copolymer (a). When the foamed particles having the polypropylene resin composition as the base resin are molded in the mold, the foamed particle molded body is preferable in that a good foamed particle molded body can be obtained without excessively increasing the heating temperature. The rigidity, heat resistance, low-temperature impact resistance, etc. are ensured.

  The ethylene component content in the propylene-ethylene block copolymer (a) is 3 to 8% by weight, preferably 3 to 7% by weight, more preferably 3 to 6% by weight, particularly preferably 4 to 6% by weight. Thus, the above-mentioned range of the melting point is realized, and further, a foamed particle molded body obtained from foamed particles using a polypropylene resin composition containing the propylene-ethylene block copolymer (a) as a base resin is , Rigidity, heat resistance, low temperature impact resistance, etc. are ensured.

The propylene-ethylene block copolymer (a) used in the present invention is a propylene-only copolymer or a propylene-ethylene random copolymer component (a) having an ethylene content of 7% by weight or less in the first step using a metallocene catalyst. -1) 30 to 95% by weight, and in the second step, propylene-ethylene random copolymer component (a-2) containing 3 to 20% more ethylene than component (a-1) is 70 to 5%. A propylene-ethylene block copolymer obtained by sequential polymerization by weight% can be obtained.
Propylene-ethylene random copolymer component (a-1) obtained in the first step and propylene-ethylene random copolymer component (a-2) obtained in the second step [hereinafter referred to as component (a-2) There is a case. And the phase transition structure, the glass transition temperature of the amorphous part contained in the component (a-1) and the glass transition temperature of the amorphous part contained in the component (a-2) are different from each other. In this case, since the respective components are not compatible with each other, there arises a problem that low temperature impact resistance cannot be obtained. The fact that the phase separation structure is taken can be distinguished by showing a plurality of peaks in the tan δ curve in the measurement of solid viscoelasticity. This is caused by having a single peak.
The sequential polymerization method will be described later, and the solid viscoelasticity measurement will be performed by the method described in Examples described later.

When the expanded particles containing the propylene-ethylene block copolymer (a) of the present invention are heated from 25 ° C. to 200 ° C. at a heating rate of 10 ° C./min by 1 to 3 mg by a heat flux differential scanning calorimetry method. In the obtained DSC curve (DSC curve of the first heating), a crystal structure in which an endothermic peak (inherent peak) unique to the polypropylene resin composition and an endothermic peak (high temperature peak) on the higher temperature side than the intrinsic peak appear Have
In the expanded particles having such a crystal structure, the presence of secondary crystals that appear as high temperature peaks makes the expanded particles excellent in mechanical strength such as rigidity and excellent in-mold moldability. On the other hand, if there is no secondary crystal, the mechanical strength is inferior, and the expanded particles tend to shrink and do not become expanded particles with good in-mold moldability.

The DSC curve in this case is shown in FIG. 2 obtained when 1 to 3 mg of expanded polypropylene resin particles are heated from 25 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min by the heat flux differential scanning calorimetry. The DSC curve of the first heating as described above, and the inherent endothermic peak (intrinsic peak) PTma is an endothermic peak inherent to the polypropylene resin constituting the foamed particles, and when the crystal inherent in the polypropylene resin is melted It is thought that this is due to the endothermic heat.
On the other hand, the endothermic peak (high temperature peak) PTmb on the higher temperature side than the intrinsic peak is an endothermic peak that appears on the higher temperature side than the intrinsic peak in the first DSC curve. The presence of secondary crystals in the resin is determined by whether or not this high temperature peak appears in the DSC curve. If no substantial high temperature peak appears, it is determined that there are no secondary crystals in the resin. Is done.

The polypropylene resin composition of the present invention comprises a propylene-ethylene random copolymer (b) having a melting point of 130 to 155 ° C. and an ethylene component content of less than 5% by weight (excluding 0). The weight ratio of the union (a) and the copolymer (b) can be 40:60 to 90:10. By setting the weight ratio within the above range, it is possible to obtain a foamed particle molded body particularly excellent in the balance between low-temperature impact resistance and mechanical strength.
The ethylene component content of a general propylene-ethylene random copolymer (b) is 5% by weight or less (excluding 0). In order to increase the mechanical strength of the foamed particle molded body, an ethylene component content is included. The amount is preferably 4% by weight or less, more preferably 3% by weight or less.
In addition, when the ethylene component content of the copolymer (b) is too low, the compatibility with the copolymer (a) may be deteriorated. From this viewpoint, the propylene-ethylene random copolymer (b ) Is preferably 1% by weight, and more preferably 1.5% by weight.

Furthermore, in the present invention, the polypropylene resin composition contains an ethylene polymer (c), and the content of the ethylene polymer (c) in the polypropylene resin composition is 1 to 30% by weight. It can be set as resin foam particles.
Examples of the ethylene polymer (c) include a copolymer elastomer of ethylene and an α-olefin having 3 or more carbon atoms.

  Even when the polypropylene resin composition that is the base resin of the expanded polypropylene resin particles of the present invention is a mixture of the copolymer (a) and the copolymer (b), the polypropylene resin composition The temperature-loss tangent (tan δ) curve obtained from solid dynamic viscoelasticity measurement (DMA) has a single peak in the range of −20 to 20 ° C. Here, a general propylene-ethylene block copolymer and a propylene-ethylene random copolymer are not completely compatible with each other and have a phase separation structure. However, it is considered that the copolymer (a) used in the present invention is obtained by the following specific production method, so that the ethylene component is relatively uniformly introduced into the propylene chain. As a result, since the compatibility with the propylene-ethylene random copolymer is excellent, it is considered that the mixture of the two does not have a phase separation structure and exhibits the single peak.

[Propylene-ethylene block copolymer (a)]
The propylene-ethylene block copolymer (a) used in the present invention is a propylene-ethylene random copolymer component having propylene alone or an ethylene content of 7% by weight or less in the first step using a metallocene catalyst as described above. 70 to 95% by weight of (a-1) and 70 to 30% of propylene-ethylene random copolymer component (a-2) containing 3 to 20% more ethylene than component (a-1) in the second step. It can be obtained by sequential polymerization of ˜5% by weight.

(1) Basic rules of propylene-ethylene block copolymer (a) by sequential polymerization method The propylene-ethylene block copolymer (a) as the main component of the base resin constituting the expanded particles in the present invention is a metallocene catalyst. A block copolymer of propylene and ethylene, which can also be obtained by sequential polymerization using the above, is a component that largely controls the physical properties of the entire composition, and has an ethylene content of 7% by weight or less in the first step. Low crystalline or amorphous propylene- containing 30 to 95% by weight of crystalline propylene-ethylene random copolymer component (a-1) and 3 to 20% by weight of ethylene in the second step as compared with the first step It is a propylene-ethylene block copolymer obtained by sequentially polymerizing 70 to 5% by weight of the ethylene random copolymer component (a-2).
The crystallinity of the component (a-1) is a propylene-ethylene random copolymer having a high stereoregularity and a relatively small amount of ethylene in the copolymer, and the low crystallinity or amorphousness of the component (a-2). Means a polymer having lower crystallinity than the component (a-1) or crystallinity cannot be observed.
In addition, the propylene-ethylene random copolymer produced in each polymerization step is a polymer in which propylene and ethylene are randomly copolymerized, each having a different ethylene content.

Such a block copolymer component (a) is required to have the solid viscoelastic behavior described in paragraph [0012], and for this purpose, it is preferable to narrowly control the composition distribution of each component. In this case, it is necessary to carry out sequential multistage polymerization using a metallocene catalyst.
Propylene-ethylene block copolymer component (a) [hereinafter sometimes referred to as “copolymer component (a)”. ] Is a so-called block copolymer obtained by sequentially polymerizing components (a-1) and (a-2) having different crystallinity, and has a single phase defined by solid viscoelasticity measurement (DMA). Is.

(2) Ethylene content [E] a1 in component (a-1)
The propylene-ethylene random copolymer component (a-1) produced in the first step is a component that is crystalline and mainly responsible for the heat resistance of the block polymer, and has an ethylene content of 7% by weight or less, When the ethylene content [E] a1 in the component (a-1) is less than 1% by weight, the crystallinity of the random block copolymer is increased and the impact resistance is insufficient. When the ethylene content exceeds 7% by weight, the crystallinity becomes too low, and the heat resistance of the foamed molded product and the mechanical strength such as rigidity are deteriorated.

(3) Ethylene content [E] a2 in component (a-2)
The low crystalline or amorphous propylene-ethylene random copolymer component (a-2) produced in the second step is a component necessary for improving the flexibility and impact resistance of the block copolymer. is there.
In order for the component (a-2) to fully exhibit the above-described effects, it is necessary that the ethylene content is in the following specific range.

That is, in the block copolymer component in the present invention, the lower the crystallinity of the component (a-2) relative to the component (a-1), the greater the impact resistance improving effect, and the crystallinity is propylene-ethylene random copolymer. Since it is controlled by the ethylene content in the coalescence, the ethylene content [E] a2 in the component (a-2) must be 3% by weight or more than the ethylene content [E] a1 in the component (a-1). The effect is not sufficient, preferably 7% by weight or more, more preferably 8% by weight, should contain more ethylene than component (a-1).
Here, when the difference in ethylene content between the component (a-1) and the component (a-2) is defined as [E] gap (= [E] a2- [E] a1), [E] gap is 6% by weight. Above, preferably 7% by weight or more, more preferably 8% by weight or more.

On the other hand, if the ethylene content is excessively increased to lower the crystallinity of the component (a-2), the difference [E] gap in the ethylene content between the component (a-1) and the component (a-2) becomes too large. It takes a phase separation structure divided into matrix and domain.
This is because polypropylene originally has low compatibility with polyethylene, and even in a propylene-ethylene random copolymer, the compatibility of both components having different ethylene contents decreases as the difference in ethylene content increases.
Therefore, the upper limit of [E] gap may be in a range where the peak of tan δ is single by solid viscoelasticity measurement described later. For that purpose, [E] gap is not more than 15% by weight, preferably 14% by weight. % Or less, more preferably 13% by weight or less.

(4) Ratio of components (a-1) and (a-2) in the block copolymer When the ratio W (a-1) of component (a-1) in the block copolymer component is too large Impact resistance deteriorates.
Therefore, the proportion of component (a-1) is 95% by weight or less, preferably 80% by weight or less.
On the other hand, when the proportion of the component (a-1) is too small, the heat resistance is remarkably deteriorated. Therefore, the proportion of the component (a-1) is 30% by weight or more, preferably 40% by weight or more. is there.
Correspondingly, the lower limit of the proportion W (a-2) of the component (a-2) in the block copolymer component is 5% by weight or more, preferably 20% by weight or more, and the upper limit is 70% by weight. Hereinafter, it is preferably 60% by weight or less.

The ratio of the copolymer component (a-1) to the copolymer component (a-2) and the ethylene content thereof were measured using TREF (temperature rising temperature elution fractionation method) as follows. The First, using the difference in crystallinity between the component (a-1) and the component (a-2), the temperature T at which the components (a-1) and (a-2) are divided from the elution curve obtained by TREF measurement. (C) is determined, and the proportion of components eluting by T (C) is regarded as the proportion of component (a-2), and the proportion of components eluting at T (C) or higher is regarded as the proportion of component (a-1). .
The technique for evaluating the crystallinity distribution of a propylene-ethylene random copolymer by TREF measurement is well known to those skilled in the art. Glokner, J. et al. Appl. Polym. Sci: Appl. Poly. Symp. 45, 1-24 (1990), L .; Wild, Adv. Polym. Sci. 98, 1-47 (1990), J .; B. P. Soares, A .; E. A detailed measurement method is shown in Hamielec, Polymer; 36, 8, 1639-1654 (1995) and the like.
In the present invention, the measurement is specifically performed as follows. A sample is dissolved in o-dichlorobenzene (containing 0.5 mg / ml BHT) at 140 ° C. to obtain a solution. This is introduced into a 140 ° C. TREF column, cooled to 100 ° C. at a rate of 8 ° C./min, subsequently cooled to −15 ° C. at a rate of 4 ° C./min, and held for 60 minutes. Then, o-dichlorobenzene (containing 0.5 mg / ml BHT) as a solvent is passed through the column at a flow rate of 1 ml / min, and the components dissolved in o-dichlorobenzene at −15 ° C. are eluted in the TREF column for 10 minutes. Next, the column is linearly heated to 140 ° C. at a heating rate of 100 ° C./hour to obtain an elution curve.

  A component having a low elution temperature has low crystallinity and is highly flexible, while a component having a high elution temperature has high crystallinity, thereby increasing rigidity and improving heat resistance. In the elution curve (dwt% / dT curve with respect to temperature) of the propylene-based block copolymer in the present invention, the crystalline propylene-ethylene random copolymer component (a-1) and low crystallinity or The amorphous propylene-ethylene copolymer component (a-2) is observed as a component eluting at different temperatures due to the difference in crystallinity. That is, component (a-1) is observed on the high temperature side because of high crystallinity, and component (a-2) is observed on the low temperature side because it is low crystalline or amorphous, or has a peak within the TREF measurement temperature. Not shown. When each peak temperature is T (A) and T (B) (if the peak is not shown, the lower limit of the measurement temperature is −15 ° C.), the temperature T (C) between the two peaks ({T (A) In + T (B)} / 2), both components are almost separable.

  At this time, the integrated amount of the component eluted up to T (C) in TREF is defined as W (B) wt%, and the integrated amount of the portion eluted at T (C) or higher is defined as W (A) wt%. W (B) substantially corresponds to the amount of the low crystalline or amorphous component (a-2), and W (A) substantially corresponds to the amount of the highly crystalline component (a-1). ing.

  Next, it fractionates into T (C) soluble component = component (a-2) and T (C) insoluble component = component (a-1) by the temperature rising column fractionation method using a preparative separation apparatus. . A specific method of fractionation is based on T (C) determined by TREF measurement, and using a preparative fractionator, a temperature rising column fractionation method is used, and T (C) soluble component = component (a-2) and T (C) The insoluble component is fractionated into the component (a-1), and the ethylene content of each component is determined by NMR. The temperature rising column fractionation method refers to a measurement method disclosed in, for example, Macromolecules, 21, 314-319 (1988).

As the separation conditions, a glass bead carrier (80 to 100 mesh) is packed in a cylindrical column having a diameter of 50 mm and a height of 500 mm, and maintained at 140 ° C. Next, 200 ml of a sample o-dichlorobenzene solution (10 mg / ml) dissolved at 140 ° C. is introduced into the column. Thereafter, the temperature of the column is cooled to 0 ° C. at a rate of temperature decrease of 10 ° C./hour. After holding at 0 ° C. for 1 hour, the column temperature is heated to T (C) at a heating rate of 10 ° C./hour and held for 1 hour. Note that the temperature control accuracy of the column through a series of operations is ± 1 ° C.
Next, while maintaining the column temperature at T (C), 800 ml of T (C) o-dichlorobenzene is allowed to flow at a flow rate of 20 ml / min, so that T (C) -soluble components present in the column can be obtained. Elute and collect.

Next, the column temperature is increased to 140 ° C. at a rate of temperature increase of 10 ° C./min, left at 140 ° C. for 1 hour, and then 800 ml of o-dichlorobenzene as a solvent at 140 ° C. is flowed at a flow rate of 20 ml / min. , And eluting and recovering insoluble components at T (C).
The polymer-containing solution obtained by fractionation is concentrated to 20 ml using an evaporator and then precipitated in 5 times the amount of methanol. The precipitated polymer is collected by filtration and dried overnight in a vacuum dryer.

The ethylene content of each fractionated component is determined by NMR. A specific method is shown below.
Measurement of ethylene content by NMR The ethylene content of each of component (a-1) and component (a-2) obtained by the above fractionation was determined by measuring the ¹³ C-NMR spectrum measured according to the following conditions by the proton complete decoupling method. Obtained by analysis.
Model: GSX-400 manufactured by JEOL Ltd. or equivalent equipment (carbon nuclear resonance frequency of 100 MHz or more)
Solvent: o-dichlorobenzene: heavy benzene = 4: 1 (volume ratio) concentration: 100 mg / ml
Temperature: 130 ° C
Pulse angle: 90 °
Pulse interval: 15 seconds Integration number: 5,000 times or more The attribution of the spectrum may be performed with reference to Macromolecules, 17, 1950 (1984), for example. The spectral assignments measured under the above conditions are as shown in Table 1 below. Symbols such as Sαα in the table follow the notation of Carman et al. (Macromolecules, 10, 536 (1977)), P represents a methyl carbon, S represents a methylene carbon, and T represents a methine carbon.

Hereinafter, when “P” is a propylene unit in a copolymer chain and “E” is an ethylene unit, six kinds of triads of PPP, PPE, EPE, PEP, PEE, and EEE may exist in the chain. As described in Macromolecules, 15, 1150 (1982), the concentration of these triads and the peak intensity of the spectrum are linked by the following relational expressions (1) to (6).
[PPP] = k × I (Tββ) (1)
[PPE] = k × I (Tβδ) (2)
[EPE] = k × I (Tδδ) (3)
[PEP] = k × I (Sββ) (4)
[PEE] = k × I (Sβδ) (5)
[EEE] = k × {I (Sδδ) / 2 + I (Sγδ) / 4} (6)
Here, [] indicates the fraction of triads, for example, [PPP] is the fraction of PPP triads in all triads.
Therefore,
[PPP] + [PPE] + [EPE] + [PEP] + [PEE] + [EEE] = 1 (7)
It is.
Further, k is a constant, I indicates the spectral intensity, and for example, I (Tββ) means the intensity of the 28.7 ppm peak attributed to Tββ.
By using the relational expressions (1) to (7) above, the fraction of each triad is obtained, and the ethylene content is obtained from the following expression.
Ethylene content (mol%) = ([PEP] + [PEE] + [EEE]) × 100
In addition, the [propylene random copolymer component] of the present invention contains a small amount of a propylene hetero bond (2,1-bond and / or 1,3-bond), thereby producing the following minute peak.

In order to obtain an accurate ethylene content, it is necessary to include the peaks derived from these heterogeneous bonds in the calculation.However, it is difficult to completely separate and identify the peaks derived from the heterogeneous bonds, and the amount of heterogeneous bonds is small. Therefore, the ethylene content of the present invention is determined using the relational expressions (1) to (7) as in the analysis of the copolymer produced with a Ziegler-Natta catalyst that does not substantially contain a heterogeneous bond. And
Conversion from mol% to mass% of ethylene content is carried out using the following formula: ethylene content (mass%) = (28 × X / 100) / {28 × X / 100 + 42 × (1−X / 100)} × 100
Here, X is the ethylene content in mol%.
The ethylene content of the entire block copolymer is calculated from the ethylene contents [E] A, [E] B, and TREF of the components (a-1) and (a-2) measured above. It is calculated by the following formula from the mass ratios W (A) and W (B) [wt%] of the components.
[E] W = [E] A × W (A) / 100 + [E] B × W (B) / 100 (wt%)

  The apparent density of the expanded polypropylene resin particles of the present invention can be 20 to 300 g / L. If the apparent density of the expanded particles is less than 20 g / L, the shrinkage of the obtained expanded expanded particles becomes large, and it becomes difficult to produce the expanded expanded particles. On the other hand, when the apparent density of the expanded particles exceeds 300 g / L, it is difficult to obtain a expanded particle molded body satisfying 50% compression elasticity and the like. From this viewpoint, the lower limit of the apparent density of the expanded particles is preferably 20 g / L, and the upper limit of the apparent density of the expanded particles is preferably 300 g / L, more preferably 80 g / L.

  The apparent density of the expanded polypropylene resin particles of the present invention is the weight V (g) of the expanded particle group that was left standing for 2 days under the conditions of 50% relative humidity, 23 ° C. and 1 atm, and the volume V of the expanded particle group. It can be obtained by dividing by (L) (W / V). For the volume V (L) of the expanded particles, a graduated cylinder containing a liquid such as alcohol at 23 ° C. (eg, ethanol) is prepared, and the expanded particles are placed in the liquid in the graduated cylinder using a wire mesh or the like. It can be calculated from the rise of the liquid level.

  In the polypropylene-based expanded particles of the present invention, the ratio of the calorific value of the high temperature peak to the calorific value of the total endothermic peak based on the intrinsic peak and the high temperature peak can be 0.1 or more. If the ratio of the heat quantity of the high temperature peak to the heat quantity of the total endothermic peak is 0.1 or more, the physical properties such as the mechanical properties, heat resistance, and low temperature impact resistance of the foamed particle molded body and the in-mold moldability of the foamed particles From the viewpoint of balance. From this viewpoint, the ratio of the heat quantity of the high temperature peak to the heat quantity of the total endothermic peak is more preferably 0.15 or more, and the upper limit is 0.4 or less, preferably 0.38 or less, more preferably 0.35 or less. It is.

  The present invention also provides a polypropylene resin foamed particle molded body obtained by in-mold molding of the polypropylene resin foamed particles of the present invention.

[Production of expanded polypropylene resin particles]
In the production of the expanded particles of the present invention, particles having a polypropylene resin composition as a base resin (hereinafter sometimes simply referred to as “resin particles”) are used as a dispersion medium such as water in a sealed container together with a foaming agent. After dispersing and heating to soften the resin particles and impregnating the resin particles with a foaming agent, the resin particles are discharged at a temperature equal to or higher than the softening temperature of the resin particles under a low pressure (usually atmospheric pressure) from inside the container. Known methods such as a foaming method (hereinafter also referred to as a direct foaming method) and a method in which foamable resin particles containing a foaming agent are taken out from a hermetic container and the foamable resin particles are heated and heated with a heating medium such as steam. The foaming method can be applied. In addition, when the contents in the sealed container are released from the sealed container to a low pressure region in order to obtain expanded particles, back pressure is applied to the sealed container with the used foaming agent or an inorganic gas such as nitrogen. From the viewpoint of uniforming the apparent density of the obtained expanded particles, it is preferable to release the contents in such a manner that the pressure does not drop rapidly.

  As the method for adjusting the average cell diameter of the above-mentioned expanded particles, an inorganic substance such as talc, aluminum hydroxide, silica, zeolite, borax, inorganic powder or the like is mainly used as a cell regulator and is adjusted to a ratio of 0.1 to 100 parts by weight of the base resin. It is carried out by blending into the base resin during granulation of the resin particles for obtaining foamed particles in a proportion of 01 to 5 parts by weight, but even with the foaming temperature and the type and amount of foaming agent used during the production of the foamed particles Since the average bubble diameter changes, it is necessary to set conditions by conducting a preliminary experiment in order to obtain a desired average bubble diameter.

  Further, the foamed particles having a high temperature peak are equal to or higher than the melting end temperature of the resin particles (hereinafter also referred to as Te) when the resin particles are dispersed in a dispersion medium and heated in the above-described known foaming method. Without increasing the temperature, the temperature is stopped at an arbitrary temperature: Ta that is 15 ° C. lower than the resin melting point (hereinafter also referred to as Tm) of the resin particles and lower than Te, and the temperature: Ta By holding for a sufficient time, preferably about 10 to 60 minutes, the resin particles on which the secondary crystals are formed can be obtained by foaming. When obtaining expanded particles by the direct expansion method, the temperature is then adjusted to an arbitrary temperature in the range of (Tm−5 ° C.) to (Te + 5 ° C.): Tb, and the resin particles are released from the container to the low pressure region at that temperature. The foamed particles can be obtained by foaming. In addition, the retention within the range of (Tm-15 ° C.) or more and less than Te for forming a high temperature peak can be set in multiple stages within the temperature range, and within the temperature range. It is also possible to form the high temperature peak by slowly raising the temperature over a sufficient period of time.

  The formation of the high temperature peak of the expanded particles and the magnitude of the heat amount of the high temperature peak are mainly due to the temperature Ta and the retention time at the temperature Ta with respect to the resin particles when the expanded particles are produced, and the (Tm-5 ° C). ) To (Te + 5 ° C.) or (Tm−15 ° C.) or more and less than Te. The amount of heat of the high temperature peak of the expanded particles is such that the temperature Ta or Tb is lower in each of the above temperature ranges and the holding time in the range of (Tm−15 ° C.) or more and less than Te is longer and (Tm −15 ° C.), the lower the rate of temperature rise within the range of Te, the larger the tendency. In addition, 0.5-5 degreeC / min is normally employ | adopted for the said temperature increase rate. On the other hand, the higher the temperature Ta or Tb is in each of the above temperature ranges, the shorter the holding time in the range of (Tm−15 ° C.) or more and less than Te, and (Tm−15 ° C.) or more and less than Te. The higher the temperature rise rate within the range, the smaller the tendency. If the preliminary experiment is repeated in consideration of these points, it is possible to know the production conditions of the expanded particles exhibiting a desired high-temperature peak heat quantity. In addition, the temperature range which concerns on formation of the high temperature peak mentioned above is a suitable temperature range at the time of using an inorganic physical foaming agent as a foaming agent. Therefore, when the foaming agent is changed to an organic physical foaming agent, the appropriate temperature range is shifted by about 0 to 30 ° C. to the lower temperature side than the above temperature range depending on the type and amount of use. .

  As the foaming agent used in the above method, an organic physical foaming agent, an inorganic physical foaming agent, or a mixture thereof can be used. Examples of organic physical blowing agents include aliphatic hydrocarbons such as propane, butane, hexane and heptane, alicyclic hydrocarbons such as cyclobutane and cyclohexane, chlorofluoromethane, trifluoromethane, 1,1-difluoroethane, 1,1 , 1,2-tetrafluoroethane, halogenated hydrocarbons such as methyl chloride, ethyl chloride, and methylene chloride, and dialkyl ethers such as dimethyl ether, diethyl ether, and methyl ethyl ether. Can be used.

  Moreover, as an inorganic physical foaming agent, nitrogen, carbon dioxide, argon, air, water, etc. are mentioned, These can be used in mixture of 2 or more types. When water is used as a dispersion medium together with the resin particles in the closed container when obtaining the foamed particles, the dispersion medium can be obtained by mixing the resin particles with a water-absorbing resin or a water-absorbing inorganic substance. Certain water can be efficiently used as a blowing agent. When mixing and using an organic physical foaming agent and an inorganic physical foaming agent, the compound arbitrarily selected from the above-mentioned organic physical foaming agent and an inorganic physical foaming agent can be used in combination. In addition, when using together an inorganic physical foaming agent and an organic physical foaming agent, it is preferable that an inorganic gas type foaming agent contains at least 30 weight% or more. Among the above foaming agents, there is no risk of ozone layer destruction, and an inexpensive inorganic physical foaming agent is preferable, and nitrogen, air, carbon dioxide, and water are particularly preferable.

  The amount of the foaming agent used is determined in consideration of the apparent density of the foamed particles to be obtained, the type of the base resin, or the type of the foaming agent, and is usually an organic physical foaming agent per 100 parts by weight of the resin particles. It is preferable to use 5 to 50 parts by weight and 0.5 to 30 parts by weight of the inorganic physical foaming agent.

  The dispersion medium for dispersing the resin particles in the production of the expanded particles is not limited to the above-described water, and any dispersion medium that does not dissolve the resin particles can be used. Examples of the dispersion medium other than water include ethylene glycol, glycerin, methanol, ethanol and the like, but usually water is used. Further, when dispersing the resin particles in the dispersion medium, a dispersant can be added to the dispersion medium as necessary. Examples of the dispersant include fine aluminum oxide, titanium oxide, basic magnesium carbonate, basic zinc carbonate, calcium carbonate, kaolin, mica, and clay. These dispersants are usually used in an amount of 0.2 to 2 parts by weight per 100 parts by weight of the resin particles.

  As the resin particles, those made of the polypropylene resin composition specified in the present invention are used, but other polypropylene resins (for example, the resin melting point is 135 ° C. within the range not impairing the intended effect of the present invention). High-density polyethylene, medium-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultra-low-density polyethylene, ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, ethylene- A resin such as an ethylene resin such as a methacrylic acid copolymer, or a polystyrene resin such as polystyrene or a styrene-maleic anhydride copolymer can be blended and used.

  In addition to the above resins, ethylene-propylene rubber, ethylene-1-butene rubber, propylene-1-butene rubber, styrene-butadiene rubber and hydrogenated products thereof, isoprene rubber, neoprene rubber, nitrile rubber, or styrene-butadiene block It is also possible to add an elastomer such as a polymer elastomer or a hydrogenated product thereof. When a resin or elastomer other than the polypropylene resin is blended with the polypropylene resin, the total amount of addition of the resin and elastomer other than the polypropylene resin is 50 parts by weight or less with respect to 100 parts by weight of the polypropylene resin. It is preferable to adjust to 30 parts by weight or less, particularly 10 parts by weight or less.

  Furthermore, various additives can be added to the resin particles. Examples of such additives include antioxidants, ultraviolet absorbers, antistatic agents, conductivity imparting agents, flame retardants, metal deactivators, pigments, dyes, crystal nucleating agents, and inorganic fillers. . Each of these various additives is preferably added in an amount of 25 parts by weight or less, more preferably 20 parts by weight or less, and particularly preferably 5 parts by weight or less based on 100 parts by weight of the resin particles.

  In addition, the polypropylene-based resin expanded particles obtained by the above-described method are subjected to a curing step under atmospheric pressure that is usually performed after the foaming step, and then placed in a pressure-tight airtight container with a pressurized gas such as air, After performing an operation of increasing the pressure in the foamed particles by pressurizing to 0.01 to 1.0 MPa (G), the foamed particles are taken out from the container and heated using steam or hot air. It is possible to obtain expanded particles having a lower apparent density (this process is referred to as two-stage expansion).

  The foamed particle molded body of the present invention is optionally subjected to an operation for increasing the pressure in the foamed particles similar to the operation in the above-described two-stage foaming, and the pressure in the foamed particles is set to 0.01 to 0.30 MPa (G). After being adjusted, the cavity of a conventionally known thermoplastic resin foamed particle mold that can be heated and cooled and that can be opened and closed and filled is filled with a saturated vapor pressure of 0.08 to 0. .40 MPa (G), preferably 0.10 to 0.28 MPa (G) of water vapor is supplied to expand and fuse the foam particles by heating them in a mold, and then the resulting foam particle molded body is It can be manufactured by adopting an in-mold molding method of cooling and taking out from the cavity. In addition, as a method of steam heating in the in-mold molding method, a conventionally known method in which heating methods such as one heating, reverse one heating, and main heating are appropriately combined can be adopted. A method of heating the expanded particles in the order of heating and main heating is preferable. The saturated vapor pressure at the time of molding in the expanded particle mold is the maximum value of the saturated vapor pressure of water vapor supplied into the mold in the molding process.

  In the in-mold molding using the polypropylene resin foam particles of the present invention, the surface of the foam particles is first melted by the heating with the water vapor, while the foam particles themselves are softened, and the secondary foam is delayed after the melt of the surface of the foam particles. By doing so, it is considered that a good foamed particle molded body having excellent appearance and fusion property between the foamed particles can be obtained.

  The expanded particle molded body of the present invention produced as described above preferably has an open cell ratio based on ASTM-D2856-70 of Procedure C of 40% or less, more preferably 30% or less, Most preferably, it is 25% or less. A foamed particle molded body having a smaller open cell ratio is superior in mechanical strength.

EXAMPLES Next, although an Example demonstrates this invention concretely, this invention is not restrict | limited at all by these examples, unless it deviates from the summary.
The following catalyst synthesis step and polymerization step were all performed in a purified nitrogen atmosphere.
First, a method and an apparatus for measuring each physical property value and an example of production of the catalyst used will be shown.

1. Physical property measurement method and apparatus (1) MFR value The MFR value of a polypropylene-based polymer indicates the melt index value measured according to JIS-K-6758.

(2) Polymerization ratio of component (a-1) and component (a-2) Measured according to the method described above.

(3) Ethylene content in component (a-1) and component (a-2) Measured according to the method described above.

(4) Melting point (Tm) of component (a-1)
Using a DSC7 differential scanning calorimeter manufactured by Perkin Elmer, Inc., the sample was heated from room temperature to 230 ° C. under the condition of 80 ° C./minute, held at that temperature for 10 minutes, and then at −10 ° C./minute. The temperature was lowered to 50 ° C., held at the same temperature for 3 minutes, and then the peak temperature when melted under a temperature rising condition of 10 ° C./min was defined as the melting point (Tm).

[Production of catalyst]
Silicate chemical treatment : To a glass separable flask with a 10 liter stirring blade, 3.75 liters of distilled water was added slowly followed by 2.5 kg of concentrated sulfuric acid (96%). At 50 ° C., 1 kg of montmorillonite (Mizusawa Chemical Co., Ltd., Benclay SL; average particle size = 50 μm) was further dispersed, heated to 90 ° C., and maintained at that temperature for 6.5 hours. After cooling to 50 ° C., the slurry was filtered under reduced pressure to recover the cake. 7 liters of distilled water was added to this cake to reslurry it, and then filtered. This washing operation was performed until the pH of the washing solution (filtrate) exceeded 3.5. The collected cake was dried at 110 ° C. overnight under a nitrogen atmosphere. The mass after drying was 707 g. The chemically treated silicate was dried in a kiln dryer.

Preparation of catalyst : 200 g of the dry silicate obtained above was introduced into a glass reactor equipped with a stirring blade with an internal volume of 3 liters, 1160 ml of mixed heptane, and further 840 ml of a heptane solution of triethylaluminum (0.60 M) were added. Stir at room temperature. After 1 hour, the mixture was washed with mixed heptane to prepare a silicate slurry at 2.0 liters. Next, 9.6 ml of a heptane solution of triisobutylaluminum (0.71 M / L) was added to the prepared silicate slurry and reacted at 25 ° C. for 1 hour. In parallel, [(r) -dichloro [1,1′-dimethylsilylenebis {2-methyl-4- (4-chlorophenyl) -4H-azurenyl}] zirconium] (synthesized in JP-A-10-226712) 33.1 ml of a triisobutylaluminum heptane solution (0.71 M) was added to 2180 mg (3 mmol) and 870 ml of mixed heptane (performed according to the example), and the mixture reacted at room temperature for 1 hour was added to the silicate slurry, Stir for 1 hour.

Preliminary polymerization : Subsequently, 2.1 liters of n-heptane was introduced into a stirring autoclave having an internal volume of 10 liters that had been sufficiently substituted with nitrogen, and maintained at 40 ° C. The previously prepared silicate / metallocene complex slurry was introduced therein. When the temperature was stabilized at 40 ° C., propylene was supplied at a rate of 100 g / hour to maintain the temperature. After 4 hours, the supply of propylene was stopped and maintained for another 2 hours. After completion of the prepolymerization, the remaining monomer was purged, stirring was stopped and the mixture was allowed to stand for about 10 minutes, and then about 3 liters of the supernatant was decanted. Subsequently, 9.5 ml of a heptane solution of triisobutylaluminum (0.71 M / L) and 5.6 liters of mixed heptane were added, and the mixture was stirred at 40 ° C. for 30 minutes and allowed to stand for 10 minutes. Removed liters. This operation was further repeated 3 times. When the component analysis of the final supernatant was performed, the concentration of the organoaluminum component was 1.23 mmol / L and the Zr concentration was 8.6 × 10 ⁻⁶ g / L, and the abundance in the supernatant with respect to the amount charged. Was 0.016%. Subsequently, 17.0 ml of a heptane solution of triisobutylaluminum (0.71 M / L) was added, followed by drying at 45 ° C. under reduced pressure. By this operation, a prepolymerized catalyst containing 2.2 g of polypropylene per 1 g of catalyst was obtained.

Example 1
Production Example 1 (Production of PP1)
(1) First polymerization step 35 kg of seed polymer was introduced into a horizontal polymerization vessel (L / D = 3.7, internal volume 100 L) having a stirring blade, and then nitrogen gas was allowed to flow for 3 hours. Thereafter, the temperature was increased while introducing propylene, ethylene and hydrogen, and when the polymerization conditions were satisfied, the catalyst hexane slurry preliminarily polymerized from the pipe 1 was added as a catalyst component containing no prepolymerized polymer at 0.8 g / hr, triisobutylaluminum as an organoaluminum compound was supplied at a constant 15 mmol / hr. While maintaining the conditions of a reaction temperature of 65 ° C., a reaction pressure of 2.0 MPaG, and a stirring speed of 35 rpm, the ethylene / propylene mixed gas molar ratio in the reactor gas phase is maintained at 0.05 and the hydrogen / propylene molar ratio is 0.00001. Thus, ethylene gas and hydrogen gas were continuously supplied from the circulation pipe 3 to produce a produced polymer, that is, a propylene-ethylene random copolymer component (a-1).

  The reaction heat was removed by the heat of vaporization of the supplied raw material propylene. The unreacted gas discharged from the polymerization reactor was cooled and condensed outside the reactor system and refluxed to the polymerization reactor. The propylene-ethylene random copolymer component (a-1) obtained by the main polymerization is intermittently withdrawn from the polymerization vessel so that the retained level of the polymer is 65% by volume of the reaction volume, and passed through a degassing tank. It was supplied to the polymerization vessel in the second polymerization step.

(2) Second polymerization step The propylene-ethylene random copolymer component (a-) from the first polymerization step was added to the horizontal polymerization vessel (L / D = 3.7, internal volume 100 L) of the second polymerization step having a stirring blade. 1) was supplied intermittently to carry out copolymerization of propylene and ethylene. The reaction conditions were a stirring speed of 18 rpm, a reaction temperature of 70 ° C., a reaction pressure of 1.9 MPaG, and ethylene was continuously supplied to the circulation pipe so that the ethylene / propylene molar ratio in the gas phase was 0.5. No hydrogen feed was performed in the second polymerization step.

The reaction heat was removed by the heat of vaporization of the supplied raw material propylene. The unreacted gas discharged from the polymerization reactor was cooled and condensed outside the reactor system and refluxed to the polymerization reactor. Ethanol was continuously added at an addition amount of 1.1 times mol to triisobutylaluminum supplied in the first polymerization step. The propylene-based block copolymer produced in the second polymerization step was intermittently withdrawn from the polymerization vessel so that the retained level of the polymer was 50% by volume of the reaction volume. The extracted propylene block copolymer was dried at 80 ° C. for 1 hour in a drier to remove unreacted monomers and ethanol to obtain a propylene-ethylene block copolymer (PP1).
The propylene-ethylene block copolymer obtained had an MFR of 7 g / 10 min, a melting point of 134 ° C., the content of component (a-1) was 57% by weight, the content of component (a-2) was 43% by weight, and the component The ethylene content of (a-1) was 1.7% by weight, and the ethylene content in component (a-2) was 11.4% by weight.

The following antioxidant and neutralizing agent were added to the propylene-ethylene block copolymer powder produced through the first and second steps, and the mixture was sufficiently stirred and mixed.
[Additive formulation]
Antioxidant: Tetrakis {methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate} methane 500 ppm, Tris (2,4-di-t-butylphenyl) phosphite 500 ppm Neutralizing agent: 500 ppm of calcium stearate A part of this was granulated under the following conditions.

[Manufacture of pellets]
80% by weight of ethylene-propylene copolymer powder and 20% by weight of KF360T (manufactured by Nippon Polyethylene, MI = 3.5 g / 10 min, density = 0.898 g / cm ³ ) as the ethylene polymer (c) A polypropylene resin composition blended with an additive was melt kneaded under the following conditions to produce pellets.
Extruder: KZW-15-45MG twin screw extruder screw manufactured by Technobel Co., Ltd .: Diameter 15 mm L / D = 45
Extruder set temperature: (from below the hopper) 40, 80, 160, 200, 220, 220 (die temperature)
Screw rotation speed: 400rpm
Discharge amount: Adjusted to 1.5 kg / h with a screw feeder Die: 3 mm diameter Strand die Number of holes 2

(Manufacture of expanded particles)
Using an extruder with an inner diameter of 40 mm, the above pellets were melted and extruded into strands. The extruded strand was cooled with water, cut with a pelletizer to a weight of 1.5 mg, and dried to obtain resin particles.
In addition, in the melt extrusion, zinc borate powder (trade name: zinc borate 2335, manufactured by Tomita Pharmaceutical Co., Ltd.) is used as a foam regulator in 0.1 parts by weight per 100 parts by weight of the base resin in a master batch. Supplied.
Next, polypropylene resin expanded particles were prepared using the resin particles.
First, 1 kg of the resin particles obtained as described above was charged into a 5 L pressure vessel equipped with a stirrer together with 3 L of water as a dispersion medium, and further 3 g of kaolin as a dispersant and a surfactant ( 0.4 g was added as an active ingredient amount (trade name: Neogen S-20F, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., sodium alkylbenzene sulfonate). Next, the temperature is raised to the foaming temperature shown in Table 3-1 to Table 4-2 under stirring, and carbon dioxide as a foaming agent is added to the pressure vessel in the pressure vessel (Table 3-1 to Table 4-2). It was press-fitted until it reached (foaming pressure) and held at that temperature for 15 minutes. Thereafter, a back pressure is applied with carbon dioxide so that the pressure in the container becomes constant, and the contents are released under atmospheric pressure, and a polypropylene resin foam having an apparent density shown in Table 3-1 to Table 4-2. Particles were obtained.
The results of measuring various physical properties such as the endothermic amount of the high-temperature peak and the apparent density of the obtained expanded particles are collectively shown in Tables 3-1 to 4-2.

[Production of foamed particle compact]
Next, a foamed particle molded body was produced using the foamed particles.
First, the obtained foamed particles shown in Table 3-1 to Table 4-2 are filled into a flat plate mold having a length of 200 mm × width of 250 mm × thickness of 50 mm, and subjected to in-mold molding by steam heating to form plate-shaped foam particles. A molded body was obtained. In the heating method, steam was supplied for 5 seconds with the drain valves on both sides of the mold open, and after preliminary heating (exhaust process), steam was supplied from the moving side mold, and then steam was supplied from the stationary side mold. Then, it heated to the shaping | molding heating steam pressure (molding pressure = shaping | molding vapor pressure).
After completion of the heating, the pressure was released, and after cooling with water until the surface pressure due to the foaming force of the molded body decreased to 0.04 MPa (G), the mold was opened and the molded body was taken out of the mold. The obtained molded body was cured in an oven at 80 ° C. for 12 hours, and then gradually cooled to room temperature. In this way, a foamed particle molded body was obtained.

Various properties such as appearance, compressive strength, Charpy impact test, and low temperature brittleness evaluation of the foamed particle molded body thus obtained were evaluated as follows.
(1) Appearance The surface of the foamed particle molded body was observed with the naked eye and evaluated according to the following criteria.
○: Almost no particle gap is observed on the surface of the foamed particle molded body, and a good surface state is shown.
(Triangle | delta): Although the particle | grain space | interval is not remarkably recognized on the surface of a foaming particle molded object, it is recognized.
X: The particle | grain space | interval is remarkable on the surface of a foaming particle molding.
(2) Fusion rate The measurement of the fusion rate is performed based on the ratio (the fusion rate) of the number of foam particles whose material is destroyed among the foam particles exposed on the fracture surface when the foamed particle molded body is broken. It was. Specifically, a test piece was cut out from the foamed particle molded body, and after cutting about 5 mm into each test piece with a cutter knife, the foamed particle molded body was broken from the cut portion. Next, the number of foam particles (n) present on the fracture surface of the foam particle molded body and the number of foam particles (b) with material destruction were measured, and the ratio (b / n) of (b) and (n). Was expressed as a percentage and used as the fusion rate (%).

(3) Dynamic viscoelasticity (solid)
The dynamic viscoelasticity of the unfoamed base resin was evaluated.
Measurement was performed using Rheometric Scientific II (manufactured by Rheometric Scientific Co., Ltd.) using a sample made of a base resin having a diameter of 5 mm and a thickness of 1 mm. The sample was deformed by compression at 1.0 Hz from −40 ° C. to 50 ° C. at a rate of temperature increase of 3 ° C./min, and storage elastic modulus, loss elastic modulus, and loss tangent (tan δ) were determined.
(4) 50% compressive stress The mechanical strength of the molded body was evaluated by measuring the 50% compressive stress of the foamed particle molded body. From the center of the molded body, a test piece was cut out in a length of 50 mm × width 50 mm × thickness 25 mm so as to be a rectangular parallelepiped shape excluding the skin layer during molding, and AUTOGRAPH AGS-X (Shimadzu Corporation) The compression rate is set to 10 mm / min, and the load at 50% strain is obtained according to JIS K 6767 (1999), and this is divided by the pressure-receiving area of the test piece. 50% compressive stress [kPa] was determined.

(5) Charpy impact test in a low temperature atmosphere A Charpy impact test of a foamed particle molded body in a low temperature atmosphere at -30 ° C was conducted using a Charpy impact tester [CHARPY (manufactured by Toyo Seiki Co., Ltd.)]. From the center of the molded body, a test piece was cut out to a length of 100 mm, a width of 10 mm, and a thickness of 20 mm, excluding the skin layer during molding, and a weight of 195 g attached to the tip of a length of 250 mm was attached to this test piece. The U-shaped weight was swung down from a position at a lifting angle of 150 ° (lifting position) and brought into contact with the sample from the thickness direction. In the measurement, the angle swung in the direction opposite to the one swung up (the swing angle) was measured, and the Charpy impact strength was calculated from the following formula. Test methods other than the sample size were in accordance with JIS K 7111, and the test piece was carried out without a notch.
Charpy impact strength (a _cu , kJ / m ² ) = W × 10 ³ / hb
W: Impact energy after correction absorbed by the specimen (J)
h: Test piece thickness (mm)
b: Width of test piece (mm)

(6) Falling ball evaluation in a low temperature atmosphere (low temperature falling ball evaluation)
The low temperature brittleness of the foamed particle molded body was evaluated by a falling ball test. A sample was cut out from the center of the molded body to a size (length 60 mm × width 60 mm × thickness 20 mm), excluding the skin layer during molding. Condition (i): After allowing the sample to stand in a freezer at −30 ° C. for 24 hours or longer, the sample is supported at two points (distance between supports: 44 mm), and a 500 g iron ball is dropped from a height of 600 mm. went. Condition (ii): After allowing the sample to stand in a freezer at −30 ° C. for 24 hours or more, the sample is supported at two points (distance between supports: 44 mm), and a 500 g iron ball is dropped from a height of 500 mm. went.
A: Almost no change is observed in the foamed particle molded body under the condition (i).
○: In the condition (i), the foamed particle molded body is broken, but in the condition (ii), almost no change is observed in the foamed particle molded body.
X: The foamed particle molded body is broken.

Examples 2 and 3
Using the same polypropylene resin composition as in Example 1, the foaming conditions were changed to make the apparent density of the expanded particles 44 g / L (Example 2) and 29 g / L (Example 3), and the apparent density of the molded product was The evaluation was performed in the same manner as in Example 1 except that the change was made. The results are shown in Table 3-1.

Examples 4-7
50% by weight of a resin comprising the same propylene-ethylene block copolymer (a) and ethylene polymer (c) as in Example 1, and a propylene ethylene random copolymer (ethylene content 2.8% by weight, melting point 143 ° C.) 50% by weight was mixed as a base resin, foamed particles were produced at the foaming pressure and foaming temperature shown in Table 3-1, and the molded pressure was adjusted to obtain foamed molded products having different apparent densities. Evaluation was performed in the same manner as in Example 1. The results are summarized in Table 3-1.

Examples 8 and 9
Production Example 2 (Production of PP2)
In Production Example 1, ethylene / propylene mixed gas molar ratio in the gas phase of the reactor in the first polymerization step was 0.06, hydrogen / propylene molar ratio was 0.0005, ethylene / propylene mole in the gas phase in the second polymerization step A propylene-ethylene block copolymer (PP2) was obtained in the same manner as in Production Example 1, except that the ratio was 0.4 and the hydrogen / (propylene + ethylene) molar ratio was 0.0003.
The propylene-ethylene block copolymer obtained above has an MFR of 20 g / 10 min, a melting point of 133 ° C., a content of component (a-1) of 56% by weight, and a content of component (a-2) of 44. The ethylene content of the component (a-1) was 1.8% by weight, and the ethylene content in the component (a-2) was 10% by weight.
Pellets were produced in the same manner as in Example 1 except that the propylene-ethylene block copolymer powder was not blended with the ethylene polymer (c).
Example 1 except that the obtained pellet was used as a base resin, foamed particles were produced at the foaming pressure and foaming temperature shown in Table 3-2, and the molding pressure was adjusted to obtain foamed molded products having different apparent densities. And evaluated in the same manner. The results are summarized in Table 3-2.

Examples 10, 13, 14
The same propylene-ethylene block copolymer (a) as in Examples 8 and 9, ie PP2, and propylene-ethylene random copolymer (b) (ethylene content 2.8% by weight, melting point 143 ° C.) as a base resin In Example 10 and Example 13 and 14 in which these mixing ratios were 50/50, in Example 13 and 14, the foaming particles were produced at the foaming pressure and foaming temperature shown in Table 3-2, and the molding pressure was adjusted. Evaluation was performed in the same manner as in Example 1 except that foamed molded products having different apparent densities were obtained. The results are summarized in Table 3-2.

Examples 11 and 12
The same propylene-ethylene block copolymer (a) 64% by weight as in Example 1 and 80% by weight of the ethylene polymer (c) 16% by weight, and the propylene-ethylene random copolymer (b) (ethylene Content 2.8 wt%, melting point 143 ° C) 20 wt% is mixed to make a base resin, foamed particles are produced at the foaming pressure and foaming temperature shown in Table 3-2, and the molding pressure is adjusted to give an apparent density Evaluations were made in the same manner as in Example 1 except that foamed molded products having different sizes were obtained. The results are summarized in Table 3-2.

Comparative Examples 1-3
Propylene-ethylene random copolymer (b) (ethylene content 2.8% by weight, melting point 141 ° C.) is used as the base resin, and foamed particles are produced at the foaming pressure and foaming temperature shown in Table 4-1, and molded. Evaluation was performed in the same manner as in Example 1 except that foamed molded products having different apparent densities of the molded products were obtained by adjusting the pressure. The results are summarized in Table 4-1.

Comparative Examples 4 and 5
Propylene-ethylene random copolymer (b) (ethylene content 3.6 wt%, melting point 137 ° C.) is used as a base resin, and foamed particles are produced at the foaming pressure and foaming temperature shown in Table 4-1, and molded. Evaluation was performed in the same manner as in Example 1 except that foamed molded products having different apparent densities of the molded products were obtained by adjusting the pressure. The results are summarized in Table 4-1.

Comparative Example 6
As a base resin, a propylene-ethylene block copolymer (ethylene content 11.7% by weight, melting point 155 ° C.) was used (indicated as “bPP” in the table), and at the foaming pressure and foaming temperature shown in Table 4-1. Evaluation was performed in the same manner as in Example 1 except that foamed particles were produced and the molding pressure was adjusted to obtain foamed molded products having different apparent densities. The results are summarized in Table 4-1.

Comparative Example 7
As a base resin, a propylene-ethylene random copolymer (b) (ethylene content 2.8% by weight, melting point 135 ° C.) polymerized using a metallocene catalyst was used. Evaluation was conducted in the same manner as in Example 1 except that foamed particles were produced at a temperature and the molding pressure was adjusted to obtain foamed molded products having different apparent densities. The results are summarized in Table 4-1.

Comparative Example 8
When the foaming temperature of 143 ° C. for obtaining the foamed particles in Example 4 was set to 153 ° C. to obtain the foamed particles, the melting point of 139 ° C. was far exceeded, so the high-temperature peak heat quantity of the foamed particles was 0 (J / g), The foamed molded product obtained by forming foamed particles having a structure with a small amount of so-called secondary crystals, and the molded product thereof, was extremely inferior in surface appearance. The results are summarized in Table 4-1.

Comparative Example 9
Propylene-ethylene random copolymer (b) (ethylene content 2.8% by weight, melting point 143 ° C.) 80% by weight and JSR EP11 (produced by JSR, ethylene content 52% by weight) which is ethylene-propylene rubber (EPR) 20 wt% was mixed to make a base resin, foamed particles were produced at the foaming pressure and foaming temperature shown in Table 4-2, and the molded pressure was adjusted to obtain foamed molded products having different apparent densities. Evaluation was performed in the same manner as in Example 1. The results are summarized in Table 4-2.

Comparative Example 10
50% by weight of propylene-ethylene random copolymer (b) (2.8% by weight of ethylene content, melting point 143 ° C.) and 50% by weight of JSR EP11 which is the same ethylene-propylene rubber (EPR) as described above were mixed. Evaluation was made in the same manner as in Example 1 except that foamed particles were produced at the foaming pressure and foaming temperature shown in Table 4-2 and obtained by adjusting the molding pressure to obtain foamed molded products having different apparent densities. did. The results are summarized in Table 4-2.

The expanded polypropylene resin particles of the present invention can be used as expanded particles capable of suppressing the embrittlement at low temperatures and obtaining a molded polypropylene resin expanded particles having good low temperature impact properties.
The polypropylene resin foamed molded article of the present invention is a foamed molded article with improved impact properties in a low temperature atmosphere at about −30 ° C., which has been difficult until now, and has problems such as cracking and chipping at low temperatures. It is difficult to use, and can be used for packaging materials, automobile shock-absorbing materials / spacer parts, heat insulating materials for buildings, sound-absorbing materials, and the like, and can be suitably used mainly for automobile applications.

Claims (6)

A foamed particle having a base resin of a polypropylene resin composition containing a propylene-ethylene block copolymer (a) having a melting point of 125 to 140 ° C. and an ethylene component content of 3 to 8% by weight,
The melting point of the polypropylene resin composition is 125 to 150 ° C., and the temperature-loss tangent (tan δ) curve obtained from the solid dynamic viscoelasticity measurement of the polypropylene resin composition is -20 to 20 ° C. One peak, the temperature showing the peak is 8 ° C. or less, and the maximum value of tan δ is 0.12 or more,
In the DSC curve (the DSC curve of the first heating) obtained when 1 to 3 mg of the expanded particles are heated from 25 ° C. to 200 ° C. at a rate of temperature increase of 10 ° C./min by a heat flux differential scanning calorimetry method, Polypropylene resin foam characterized by having a crystal structure in which two endothermic peaks, an endothermic peak (inherent peak) unique to the resin-based resin composition and an endothermic peak (high temperature peak) on the higher temperature side than the intrinsic peak appear particle.   The polypropylene-based resin composition includes a propylene-ethylene random copolymer (b) having a melting point of 130 to 155 ° C. and an ethylene component content of less than 5% by weight (excluding 0). 2) and the copolymer (b) in a weight ratio of 40:60 to 90:10.   The polypropylene according to claim 1 or 2, wherein the polypropylene resin composition contains an ethylene polymer (c), and the content of the polymer (c) in the polypropylene resin composition is 1 to 30% by weight. Resin foam particles.   The copolymer (a) is 30 to 95% by weight of propylene alone or a propylene-ethylene random copolymer component (a-1) having an ethylene content of 7% by weight or less in the first step using a metallocene catalyst. It was obtained by sequentially polymerizing 70 to 5% by weight of a propylene-ethylene random copolymer component (a-2) containing 3 to 20% more ethylene than component (a-1) in the second step. The expanded polypropylene resin particle according to any one of claims 1 to 3, which is a propylene-ethylene block copolymer.   The polypropylene resin expanded particles according to any one of claims 1 to 4, wherein the expanded density of the expanded particles is 20 to 300 g / L.   A polypropylene resin foamed particle molded body obtained by molding the polypropylene resin foamed particle according to any one of claims 1 to 5 in a mold.

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